Battery cell, battery device and electric device

Abstract

The invention relates to a battery monomer, a battery device and a power utilization device, the battery monomer comprises a shell assembly and an electrode assembly, and the shell assembly comprises a shell and a first electrode terminal arranged on the shell; the electrode assembly is accommodated in the shell and comprises a first pole piece and a second pole piece, each of the first pole piece and the second pole piece comprises a coating part and a tab, the coating part comprises an active material layer, the tab is not provided with the active material layer, one of the first pole piece and the second pole piece is a positive pole piece, and the other one is a negative pole piece; the active material layer in the positive pole piece comprises a positive active material, and the positive active material comprises lithium-containing phosphate with an olivine structure; the tab in the first pole piece is used for electrically connecting the first electrode terminal and the coating part in the first pole piece, and the area of the projection plane of the first electrode terminal along the thickness direction of the first electrode terminal is 300mm < 2 >-500mm < 2 >. According to the invention, the cycle performance and the use reliability of the battery monomer under a fast charge condition can be effectively improved.

Description

[0001] This application claims the priority of International Application PCT / CN2024 / 109018, titled "Battery Cell, Battery Device and Electrical Device", filed on July 31, 2024, the entire content of which is incorporated herein by reference. Technical Field

[0002] This application relates to a battery cell, a battery device and an electrical device. Background Art

[0003] Lithium-ion batteries have characteristics such as high capacity and long life, and are thus widely used in electronic devices, such as mobile phones, laptop computers, battery cars, electric vehicles, electric airplanes, electric ships, and electric tools, etc. With the development of the application fields of lithium-ion batteries, higher requirements are put forward for the performance of lithium-ion batteries, such as cycle performance and usage reliability. Summary of the Invention This application provides a battery cell, a battery device and an electrical device, which can improve the cycle performance and usage reliability of the battery cell under fast charging conditions.

[0004] In a first aspect, this application proposes a battery cell. The battery cell includes an electrode assembly and a housing assembly. The housing assembly includes a housing and a first electrode terminal disposed on the housing; the electrode assembly is accommodated in the housing, and the electrode assembly includes a first electrode tab and a second electrode tab. Both the first electrode tab and the second electrode tab include a coated portion and an ear. The coated portion includes an active material layer, and the ear is not provided with an active material layer. Among them, one of the first electrode tab and the second electrode tab is a positive electrode tab, and the other is a negative electrode tab. The active material layer in the positive electrode tab includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure; the ear in the first electrode tab is used for electrically connecting the first electrode terminal and the coated portion in the first electrode tab. The area of the projection plane of the first electrode terminal along its own thickness direction is 200 mm 2 to 600 mm 2 , and the charging time of the battery cell from 10% state of charge to 80% state of charge is 5 min to 10.5 min; The first electrode terminal is used to connect to an external first busbar, and the area of the connection region between the first electrode terminal and the first busbar is 60 mm 2 to 150 mm 2 .

[0005] Thus, in the embodiments of this application, on the one hand, the area of the projection plane of the first electrode terminal is increased, and the area of the projection plane of the first electrode terminal is greater than or equal to 200 mm 2, so that the contact area between the first electrode terminal and the first tab is not too small, which can reduce the contact resistance between the first electrode terminal and the first tab, reduce the heat generated by the first electrode terminal, prevent the temperature in the battery cell system from being too high, and improve the cycle stability and use reliability of the active material; even in the case of a large current density during fast charging, the heat generated by the first electrode terminal will not be excessive, which is beneficial to improving the cycle stability of the active material; on the other hand, the positive active material includes lithium-containing phosphate with an olivine structure, and this material has a stable structure during charge and discharge and is not prone to capacity decay, which is beneficial to further improving the cycle performance of the battery cell; and since the area of the projection plane of the first electrode terminal is less than or equal to 600 mm 2 , the weight ratio of the electrode terminal in the battery cell is relatively small, which is beneficial to improving the weight energy density of the battery cell. The area of the connection region between the first electrode terminal and the first busbar is within the above range, and the area of the connection region is relatively large. When laser welding is used, the area of the weld mark is relatively large, which can reduce the welding resistance, reduce heat generation, reduce the heat transfer amount to the inside of the battery cell, and improve the cycle performance of the battery cell.

[0006] In some embodiments, the area of the projection plane of the first electrode terminal is 300 mm 2 to 500 mm 2 . Thus, the embodiments of the present application can improve the cycle performance and weight energy density of the battery cell.

[0007] In some embodiments, the tab in the first electrode plate is directly connected to the first electrode terminal. The direct connection can shorten the current conduction path, reduce the resistance on the current conduction path, reduce heat generation, and reduce the temperature inside the battery cell, thereby further improving the cycle performance of the battery cell.

[0008] In some embodiments, the outer shell includes an electrode lead-out hole, the first electrode terminal covers the electrode lead-out hole, and the first electrode terminal is also connected to the side of the outer shell facing the coating portion. The above setting method is beneficial to the direct connection between the first electrode terminal and the first tab.

[0009] In some embodiments, the first electrode terminal includes a bearing portion with a hollow structure, at least part of the tab in the first electrode plate is accommodated in the bearing portion, and the inner wall of the bearing portion is connected to the tab in the first electrode plate. Arranging at least part of the tab in the bearing portion can reduce the internal space of the battery cell occupied by the tab, increase the available space of the first coating portion in height, and improve the volume energy density of the battery cell.

[0010] In some embodiments, the inner wall includes an end wall and a side wall, the side wall is disposed around the end wall; the tab in the first electrode plate is connected to the end wall; and / or the tab in the first electrode plate is connected to the side wall.

[0011] In some embodiments, the battery cell includes a first adapter, the first adapter connects the tab of the first pole piece and the first electrode terminal, and the tab of the first pole piece is the first tab. The bearing portion not only has the function of accommodating the first tab, but also can realize the connection with the first tab, so that the structure of the first electrode terminal can be simplified, and the processing of the first electrode terminal can be facilitated; the structure of the first tab can also be simplified, the redundancy of the first tab can be reduced, and the manufacturing cost of the first tab can be reduced.

[0012] In some embodiments, the housing includes an electrode lead-out hole, the first electrode terminal covers the electrode lead-out hole, and the first electrode terminal is disposed on a side of the housing away from the coating portion. This structural form ensures that the first electrode terminal substantially does not occupy space inside the housing, which is beneficial for increasing the space utilization inside the housing, increasing the available space of the first coating portion, and improving the volume energy density of the battery cell.

[0013] In some embodiments, the area of the connection region between the first adapter and the first electrode terminal is 35 mm 2 Up to 50mm 2 The area of the connection region between the first adapter and the first electrode terminal is within the above range, and the area of the connection region is relatively large. When laser welding is used, the weld area is relatively large, which can reduce welding resistance, reduce heat generation, and improve the cycle performance of the battery cell.

[0014] In some embodiments, the area of the connection region between the first adapter and the first tab is 80 mm 2 Up to 160mm 2 The area of the connection region between the first adapter and the first pole ear is within the above range, and the area of the connection region is relatively large. When laser welding is used, the weld area is relatively large, which can reduce welding resistance, reduce heat generation, and improve the cycle performance of the battery cell.

[0015] In some embodiments, the first adapter is located between the first pole lug and the first electrode terminal; the projection surface of the connection area between the first adapter and the first pole lug along the thickness direction of the first electrode terminal is the first projection surface; the first electrode terminal is used to connect with the external first busbar, and the projection surface of the connection area between the first electrode terminal and the first busbar along the thickness direction of the first electrode terminal is the second projection surface, wherein the distance between the geometric center of the first projection surface and the geometric center of the second projection surface is 0 to 50 mm. The above arrangement makes the current conduction path between the first electrode terminal and the first pole lug appropriate, which can effectively reduce the heat generation resistance, reduce the heat generation of the battery cell, and improve the cycle performance of the battery cell.

[0016] In some embodiments, the first adapter is a positive adapter, and the thickness of the positive adapter is from 0.6 mm to 2.0 mm, optionally from 1.0 mm to 1.5 mm.

[0017] In some embodiments, the first adapter is a positive adapter, and the cross-sectional area of the positive adapter perpendicular to its own thickness direction is 30 mm 2 to 60 mm 2 .

[0018] In some embodiments, the first adapter is a negative adapter, and the thickness of the negative adapter is from 0.5 mm to 1.5 mm, preferably from 0.6 mm to 1.2 mm.

[0019] In some embodiments, the first adapter is a negative adapter, and the cross-sectional area of the negative adapter perpendicular to its own thickness direction is 24 mm 2 to 60 mm 2 .

[0020] In some embodiments, the tab in the first electrode sheet is a positive tab, and the cross-sectional area of the positive tab on the side close to the coating portion is 0.45 mm 2 to 1.0 mm 2 .

[0021] In some embodiments, the tab in the first electrode sheet is a negative tab, and the cross-sectional area of the negative tab on the side close to the coating portion is 0.18 mm 2 to 1.0 mm 2 .

[0022] In some embodiments, the electrode assembly is a laminated structure, the first electrode sheet and the second electrode sheet are laminated along the thickness direction of the electrode assembly, the first electrode terminal is connected to the tab of the first electrode sheet, and the area of the connection region between the first electrode terminal and the tab of the first electrode sheet is 140 mm 2 to 420 mm 2 , preferably 210 mm 2 to 350 mm 2 .

[0023] In some embodiments, the first electrode terminal is one or more.

[0024] In some embodiments, a plurality of first electrode terminals are located on both sides of the coating portion.

[0025] In some embodiments, a plurality of first electrode terminals are located on the same side of the coating portion.

[0026] In some embodiments, the outer shell assembly further includes a second electrode terminal disposed on the outer shell. The tab of the second electrode plate is used to electrically connect the second electrode terminal and the coated portion of the second electrode plate. The area of the projection plane of the second electrode terminal along its own thickness direction is 200 mm 2 to 600 mm 2 . When the area of the projection plane of the second electrode terminal along its own thickness direction is within the above range, the cycle performance and energy density of the battery cell can be effectively improved.

[0027] In some embodiments, the outer shell includes a housing and an end cap. The housing is in a cuboid structure. The housing accommodates the electrode assembly and has an opening. The end cap covers the opening, and a first electrode terminal is provided on the end cap; the dimension of the projection plane of the first electrode terminal along its own thickness direction in the thickness direction of the battery cell is a first dimension, and the dimension of the end cap in the thickness direction of the battery cell is a second dimension. The ratio of the first dimension to the second dimension is greater than 0 and less than or equal to 0.85, and can be selected from 0.40 to 0.85. The relatively high area occupancy of the first electrode terminal on the end cap is beneficial to improving the overcurrent capacity of the first electrode terminal.

[0028] In some embodiments, the electrode assembly is a wound structure. The first electrode plate and the second electrode plate are wound in one direction. In the direction from the coated portion to the end cap of the outer shell, the dimension of the coated portion of the first electrode plate is 60 mm to 120 mm.

[0029] In some embodiments, the electrode assembly is a stacked structure. The first electrode plate and the second electrode plate are stacked along the thickness direction of the battery cell. In the direction from the coated portion to the end cap of the outer shell, the dimension of the coated portion of the first electrode plate is 300 mm to 550 mm.

[0030] In some embodiments, the electrode assembly is a stacked structure. The first electrode plate and the second electrode plate are stacked along the thickness direction of the battery cell. The projection plane of the first electrode terminal along its own thickness direction is rectangular.

[0031] In some embodiments, the electrode assembly is a wound structure. The first electrode plate and the second electrode plate are wound in one direction. The projection plane of the first electrode terminal along its own thickness direction is circular.

[0032] In some embodiments, the first electrode plate is a positive electrode plate.

[0033] In some embodiments, the first electrode plate is a negative electrode plate.

[0034] In some embodiments, a battery cell includes a housing assembly, an electrode assembly, and an electrolyte. The electrode assembly and the electrolyte are accommodated within the housing assembly, and the housing assembly is provided with electrode terminals. The electrode assembly includes a first electrode tab, a second electrode tab, and a separator membrane located between the first electrode tab and the second electrode tab. Both the first electrode tab and the second electrode tab include a coated portion and an electrode ear, the coated portion is coated with an active material layer, and the electrode ear is not coated with the active material layer. The first electrode tab and the second electrode tab have opposite polarities, and one of the first electrode tab and the second electrode tab is a positive electrode tab. The active material layer of the positive electrode tab includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure. The electrode assembly is electrically connected to the electrode terminals through the electrode ears. Wherein, the coated portion of the first electrode tab includes a first straight section, the coated portion of the second electrode tab includes a second straight section, the first straight section and the second straight section are stacked along the thickness direction of the electrode assembly, and the ratio of the number of electrode ears of the first electrode tab to the number of first straight sections of the first electrode tab is 0.5 to 2. The electrolyte includes an organic solvent, and the organic solvent includes a chain carboxylic ester solvent, and the mass content of the chain carboxylic ester solvent in the electrolyte is 6% to 65%.

[0035] Thus, in the embodiments of the present application, the electrolyte includes the chain carboxylic ester solvent with the above mass content. The conductivity of this solvent system is relatively high, which is beneficial to the rapid migration of lithium ions and improves the rapid charging performance of the battery cell. In the rapid charging system of the battery cell, the current density of the electrode ears is usually relatively large, resulting in increased heat generation, making the temperature in the battery cell relatively high, which easily leads to the attenuation of the active material and the decomposition of the organic solvent in the electrolyte, deteriorating the cycle performance. While the positive electrode active material includes a lithium-containing phosphate with an olivine structure, this material has a stable structure during charge and discharge and is not prone to capacity attenuation, which is beneficial to improving the cycle performance of the battery cell. At the same time, when the ratio of the number of electrode ears of the first electrode tab to the number of first straight sections of the first electrode tab is within the above range, the shunting ability of the electrode ears can be increased, which can further improve the rapid charging performance of the battery cell. However, since the connection area between the electrode ears and other components such as the coated portion is relatively large, the overcurrent impedance can be effectively reduced, and the overcurrent temperature rise can be reduced, so that the temperature rise inside the battery cell will not be too high, improving the stability of the electrolyte system and the stability of the active material, which is beneficial to improving the use reliability of the battery cell and can improve the cycle performance. And there are more connection sites between the electrode ears and the coated portion, etc., which can increase connection redundancy such as welding redundancy and effectively improve the product yield. Thus, the embodiments of the present application can improve the cycle performance and rapid charging performance of the battery cell.

[0036] In some embodiments, the mass content of the chain carboxylic ester solvent in the electrolyte is 25% to 60%.

[0037] In some embodiments, the ratio of the number of the pole ears of the second pole piece to the number of the second straight sections of the second pole piece is 0.5 to 2. The embodiments of the present application can improve the cycle performance and fast charging performance of the battery cell.

[0038] In some embodiments, the electrode assembly is a wound structure, the first pole sheet and the second pole sheet are wound in one direction, and the first pole sheet has a plurality of pole ears.

[0039] In some embodiments, the ratio of the number of pole ears of the first pole piece to the number of the first straight sections of the first pole piece is 0.5 to 1. The embodiments of the present application can improve the cycle performance and fast charging performance of the battery cell.

[0040] In some embodiments, the electrode assembly is a laminated structure, and there are multiple first pole pieces and multiple second pole pieces, and each first pole piece has at least one pole ear.

[0041] In some embodiments, the ratio of the number of pole ears of the first pole piece to the number of the first straight sections of the first pole piece is 1 to 2. The embodiments of the present application can improve the cycle performance and fast charging performance of the battery cell.

[0042] In some embodiments, the first pole piece has multiple pole tabs, and the multiple pole tabs of the first pole piece are arranged on the same side of the coating portion. The first pole tabs can be arranged on the same side of the first coating portion, which can increase welding redundancy and effectively improve product yield.

[0043] In some embodiments, the first pole piece has multiple pole ears, and the multiple pole ears of the first pole piece are respectively arranged on both sides of the coating portion. The embodiments of the present application can improve the cycle performance and fast charging performance of the battery cell. The first pole ear can share the current density of a single first pole piece, especially when the area of the first pole piece is relatively large, the shunting inside the first pole piece is more uniform, which is conducive to uniform reaction and reduces impedance.

[0044] In some embodiments, the tab includes a tab body and a plurality of tab protrusions, wherein the tab body is connected to the coating portion; the plurality of tab protrusions are all connected to the side of the tab body away from the coating portion, and there is a gap between two adjacent tab protrusions, and each tab protrusion is used to be electrically connected to the electrode terminal.

[0045] Therefore, in the embodiment of the present application, the arrangement of multiple pole lug protrusions allows the first pole lug to have multiple connection sites. For example, when connecting the first pole lug to the first adapter, the multiple pole lug protrusions can be respectively connected to different positions of the first adapter, such as by welding, which can increase the welding positions of the first pole lug and the first adapter, improve the welding yield, and enhance the stability of the connection between the two.

[0046] In some embodiments, the tab in the first electrode sheet is a positive tab, and the thickness of the positive tab is 10 μm to 20 μm.

[0047] When the thickness of the positive tab is within the above range, the current-carrying capacity of the positive tab is relatively excellent, which can reduce heat generation and is beneficial to improving the fast charging performance of the battery cell.

[0048] In some embodiments, the tab in the first electrode sheet is a negative tab, and the thickness of the negative tab is 4 μm to 10 μm.

[0049] When the thickness of the negative tab is within the above range, the current-carrying capacity of the negative tab is relatively excellent, which can reduce heat generation and is beneficial to improving the fast charging performance of the battery cell.

[0050] In some embodiments, the conductivity of the electrolyte is 10.5 mS / cm to 20 mS / cm, and can be optionally 15 mS / cm to 20 mS / cm.

[0051] When the conductivity of the electrolyte at room temperature is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0052] In some embodiments, the chain carboxylic ester solvent includes the compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a halogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0053] Thus, the conductivity of the above chain carboxylic ester solvent in the embodiments of the present application is relatively high, which is beneficial to improving the fast charging ability of the battery cell.

[0054] In some embodiments, R1 includes a hydrogen atom, a halogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0055] In some embodiments, R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0056] In some embodiments, the chain carboxylic ester solvent includes one or more of the compounds shown in Formula I-1 to Formula I-8,

[0057] In some embodiments, the organic solvent further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The above-mentioned carbonate solvent and the chain carboxylic acid ester solvent are used in combination, so that the conductivity of the electrolyte is improved, which is beneficial to the migration of lithium ions.

[0058] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0059] In some embodiments, the mass content of the carbonate solvent in the electrolyte is 20% to 80%, and optionally 25.5% to 42.5%. The carbonate solvent with the above mass content can further improve the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0060] In some embodiments, the electrolyte further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The above-mentioned additive can improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0061] In some embodiments, the carbonate additive includes one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0062] In some embodiments, the sulfur-containing additive includes one or more of ethylene sulfate DTD, bis(ethylene sulfate) 2-DTD, butene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methylene methanedisulfonate MMDS.

[0063] In some embodiments, the lithium salt additive includes one or more of lithium difluorophosphate LiPO2F2, lithium difluorooxalate borate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bis(oxalate) borate LiBOB.

[0064] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, and optionally 2% to 8%. The additive with the above mass content can effectively improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to improving the fast charging performance of the battery cell and improving the cycle performance.

[0065] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes one or more of a fluorosulfonylimide salt and lithium hexafluorophosphate LiPF6. The above-mentioned lithium salt is easy to dissociate, which is beneficial to the rapid migration of lithium ions; and the electrolyte system is relatively stable and not easy to decompose, which can improve the cycle performance of the battery cell.

[0066] In some embodiments, the fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0067] In some embodiments, the lithium salt includes lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6). The molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is from 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is from 0.5 mol / L to 1.0 mol / L.

[0068] In some embodiments, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate (LiPF6) is from 0.2 to 1.0, and may be from 0.2 to 0.5.

[0069] In some embodiments, the viscosity of the electrolyte at room temperature is from 2.3 mPa·s to 3.5 mPa·s. When the viscosity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0070] In some embodiments, the density of the electrolyte at room temperature is from 1.05 g / mL to 1.35 g / mL. When the density of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0071] In some embodiments, the lithium-containing phosphate in the olivine structure includes phosphate particles and a coating layer. The coating layer coats the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn. By surface coating the coating layer, the conductivity of the lithium-containing phosphate in the olivine structure can be improved, the powder resistivity of the material can be reduced, and it is beneficial to the migration rate of lithium ions and reduce the heat generation of the battery cell.

[0072] In some embodiments, the phosphate particles include a general formula of Li x1 A y1 Me a M b P 1-c X c Y za compound, wherein 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F. The lithium-containing phosphate with olivine structure has excellent cycling stability, which is beneficial to improving the cycling performance of a single battery cell.

[0073] In some embodiments, the coating layer includes a fast ion conductor having the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 , where M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0 ≤ d ≤ 1, 0 < x2 < 5, and 0 < y2 < 4. Coating the phosphate particles with the fast ion conductor can significantly improve the transport rate of lithium ions during multiple deintercalation / insertion of lithium at the positive electrode, improve the ionic conductivity of the positive electrode active material, and further improve the specific capacity, and further improve the energy density of the corresponding single battery cell.

[0074] In some embodiments, the graphitization degree of the positive electrode active material is from 0.15 to 0.32; optionally from 0.19 to 0.26. When the graphitization degree of the positive electrode active material is within the above range, it is beneficial to improve the conductivity of the positive electrode active material, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the single battery cell.

[0075] In some embodiments, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1% to 2%; the specific surface area of the lithium-containing phosphate with olivine structure is 5 m 2 / g to 18 m 2 / g; optionally 7.5 m 2 / g to 14 m 2 / g.

[0076] Thus, the carbon element with the above mass content in the embodiments of the present application in combination with the material with the above specific surface area is more conducive to the effective contact between the electrolyte and the lithium-containing phosphate with olivine structure in the core, and is beneficial to the transport of lithium ions at the phase interface.

[0077] In some embodiments, the volume-based particle size distribution of the positive electrode active material satisfies: 1 µm ≤ Dv50 ≤ 2 µm, and 0.4 µm ≤ Dv10 ≤ 0.7 µm. The particle size of the positive electrode active material is relatively small, the lithium deintercalation / insertion path in the positive electrode active material is short, and the heat generation is less; moreover, the particle size of the above positive electrode active material is not too small, and basically no agglomeration occurs during the processing and preparation process, so that the performance of the positive electrode active material is stable.

[0078] In some embodiments, the lithium-containing phosphate with an olivine structure is granular. The lithium-containing phosphate with an olivine structure includes secondary particles formed by the agglomeration of primary particles, and the average particle size of the primary particles is from 200 nm to 500 nm. The average particle size of the primary particles is relatively small, the lithium deintercalation / insertion path in the positive electrode active material is short, and the heat generation is less.

[0079] In some embodiments, the coated part of the negative electrode plate includes a negative electrode film layer. The negative electrode film layer includes a negative electrode active material. The negative electrode active material includes a carbon-based material. The carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is from 92.0% to 94.5%.

[0080] When the graphitization degree of the graphite particles is within the above range, the conductive performance of the graphite particles is relatively excellent, which can reduce the heat generation of the negative electrode plate and the heat generation of the battery cell; and can improve the fast charging performance of the battery cell.

[0081] In some embodiments, the graphite particles include artificial graphite and amorphous carbon. The artificial graphite includes secondary particles formed by the aggregation of a plurality of primary particles; the amorphous carbon layer is coated on the surface of the artificial graphite. The amorphous carbon layer has more end faces and defects, so that the number of sites capable of deintercalating / inserting lithium ions is more, making the conductivity of the amorphous carbon layer relatively excellent, which can reduce the internal resistance of the negative electrode plate and the heat generation of the battery cell.

[0082] In some embodiments, based on the mass of the graphite particles, the mass content of the amorphous carbon layer is from 2% to 5%. When the mass content of the amorphous carbon layer is within the above range, it can further reduce the internal resistance of the negative electrode plate and the heat generation of the battery cell.

[0083] In some embodiments, the coated part of the negative electrode plate, the negative electrode film layer, includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector part. The carbon-based material in the first negative electrode film layer includes graphite particles. The second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector part. The carbon-based material in the second negative electrode film layer includes graphite particles. The volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0084] Therefore, in the embodiments of the present application, there are differences in the particle sizes of the particles in the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell; specifically, during fast charging, the overpotential of the second negative electrode film layer is usually relatively high, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the fast charging performance, and improve the problem of lithium deposition on the surface layer of the negative electrode sheet.

[0085] In some embodiments, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0086] In some embodiments, the tapped density of the carbon-based material in the first negative electrode film layer is less than or equal to the tapped density of the carbon-based material in the second negative electrode film layer. When the tapped density of the carbon-based material in the second negative electrode film layer is greater than the tapped density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, improving the energy density of the battery cell; the first negative electrode film layer is filled relatively sparsely with richer pores, which can improve the fast charging performance of the battery cell.

[0087] In some embodiments, the tapped density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 . When the tapped density of the carbon-based material in the first negative electrode film layer is within a suitable range, the fast charging performance of the battery cell can be improved.

[0088] In some embodiments, the tapped density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3 . When the tapped density of the carbon-based material in the second negative electrode film layer is within a suitable range, the energy density of the battery cell can be improved. In some embodiments, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is 9.5 μm to 18.5 μm. When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is within the above range, the fast charging performance can be improved.

[0089] In some embodiments, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is 7.8 μm to 14.3 μm. When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer is within the above range, the tortuosity of lithium ion transmission can be reduced, improving the fast charging performance of the battery cell.

[0090] In some embodiments, the first negative electrode film layer further includes a first lithium-containing binder, and the second negative electrode film layer further includes a second lithium-containing binder. The mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0091] Thus, in the embodiments of the present application, the mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the number of free-moving lithium ions provided by the second lithium-containing binder for the second negative electrode film layer is relatively more, which can further improve the fast charging performance of the battery cell.

[0092] In some embodiments, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. When the mass content of the first lithium-containing binder is within the above range, the intercalation and deintercalation rate of lithium ions can be improved, and the fast charging performance of the battery cell can be improved.

[0093] In some embodiments, the mass content of lithium element in the first lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. When the mass content of lithium element is within the above range, the number of free-moving lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0094] In some embodiments, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%. When the mass content of lithium element in the second lithium-containing binder is within the above range, the intercalation and deintercalation rate of lithium ions is improved, and the fast charging performance of the battery cell is improved.

[0095] In some embodiments, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. When the mass content of lithium element is within the above range, the number of free-moving lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0096] In some embodiments, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer. The lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a 2-hydroxyethyl acrylate monomer. The molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 2-hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0097] Therefore, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improving the fast charging performance of the battery cell; moreover, it is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0098] In some embodiments, the second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and 2-hydroxyethyl acrylate monomer. The molar ratio of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and 2-hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0099] Therefore, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, improving the fast charging performance of the battery cell; moreover, it is not prone to swelling during charge and discharge, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during fast charge and discharge.

[0100] In some embodiments, the negative electrode active material further includes a silicon-based material, and the mass content of silicon element in the silicon-based material is 0.3% to 10.0% based on the mass of the negative electrode active material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell.

[0101] In some embodiments, the battery cell includes a separator, and the separator includes a base film with a porous structure, and the porosity of the base film is 20% to 70%. When the porosity of the separator in the embodiments of the present application is within the above range, it can improve the migration ability of lithium ions in the separator, further reduce the internal resistance of the battery cell, and thus reduce heat generation.

[0102] In some embodiments, the separator includes a base film with a porous structure, and the porosity of the base film is 35% to 60%. When the porosity of the separator in the embodiments of the present application is within the above range, it can improve the migration ability of lithium ions in the separator, further reduce the internal resistance of the battery cell, and thus reduce heat generation.

[0103] In some embodiments, the thickness of the base film is 6 μm to 12 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, which can further reduce the internal resistance of the battery cell and thus reduce heat generation.

[0104] In some embodiments, the thickness of the base film is 6 μm to 9 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, which can further reduce the internal resistance of the battery cell and thus reduce heat generation.

[0105] In some embodiments, the separator membrane comprises a base film and functional layers disposed on at least one side of the base film. The functional layers include a first functional layer and a second functional layer. The first functional layer is located on one side of the base film and includes first inorganic particles. The second functional layer is located on the other side of the base film and includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles. The second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles. The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator membrane.

[0106] In some embodiments, the non-fluoropolymer particles include acrylate copolymers. Acrylate copolymers have excellent adhesion properties and high adhesion stability with the base film.

[0107] In some embodiments, the first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0108] In some embodiments, the second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above second inorganic particles can improve the heat resistance of the first functional layer.

[0109] In some embodiments, the average particle size of the second inorganic particles is 5 nm to 100 nm. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0110] In some embodiments, the base material of the housing includes steel, and the thickness of the housing is 0.1 mm to 0.5 mm, and can be selected as 0.2 mm to 0.35 mm. When the thickness of the housing is within the above range, the mechanical strength of the housing is high, which can improve the use reliability and cycle performance of the battery cell; and the housing occupies less space and there is more internal space in the housing, which is beneficial to improve the energy density of the battery cell.

[0111] In some embodiments, the charging time of the battery cell from 10% state of charge to 80% state of charge is 5 min to 10.5 min. The charging speed of the battery cell is fast, which is more beneficial to improve the fast charging ability.

[0112] In a second aspect, the present application provides a battery device, which includes a plurality of battery cells according to any one of the embodiments in the first aspect of the present application.

[0113] In some embodiments, the charging time of the battery device from 10% state of charge to 80% state of charge is 5 min to 10.5 min. The charging speed of the battery device is relatively fast, which is more conducive to improving the fast charging ability.

[0114] In a third aspect, the present application provides an electrical device, which includes the battery device according to any one of the embodiments of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0115] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0116] Figure 1 Schematic structural diagram of a battery cell provided in some embodiments of the present application; Figure 2 Explosion schematic diagram of a battery cell provided in some embodiments of the present application; Figure 3 Schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application; Figure 4 Schematic structural diagram of a first electrode tab of a battery cell provided in some embodiments of the present application; Figure 5 Schematic structural diagram of a second electrode tab of a battery cell provided in some embodiments of the present application; Figure 6 Schematic structural diagram of an electrode assembly of a battery cell provided in some other embodiments of the present application; Figure 7 Schematic structural diagram of a first electrode tab of a battery cell provided in some other embodiments of the present application; Figure 8 Schematic structural diagram of a second electrode tab of a battery cell provided in some other embodiments of the present application; Figure 9 Schematic cross-sectional structural diagram of a battery cell provided in some embodiments of the present application; Figure 10 For Figure 9 the enlarged structural diagram of the battery cell shown at I; Figure 11 Schematic cross-sectional structural diagram of a battery cell provided in some other embodiments of the present application; Figure 12 For Figure 11 the enlarged structural diagram of the battery cell shown at II; Figure 13Explosion schematic diagram of a battery cell provided for other embodiments of the present application; Figure 14 Top view structural schematic diagram of a battery cell provided for other embodiments of the present application; Figure 15 Structural schematic diagram of an electrode assembly of a battery cell provided for still other embodiments of the present application; Figure 16 Structural schematic diagram of an electrode assembly of a battery cell provided for still other embodiments of the present application; Figure 17 Structural schematic diagram of an electrode assembly of a battery cell provided for still other embodiments of the present application; Figure 18 Structural schematic diagram of an electrode assembly of a battery cell provided for still other embodiments of the present application; Figure 19 Expansion schematic diagram of a first pole piece of an electrode assembly in a battery cell provided for other embodiments of the present application; Figure 20 Expansion schematic diagram of a first pole piece of an electrode assembly in a battery cell provided for other embodiments of the present application; Figure 21 Structural schematic diagram of a second pole piece of a battery cell provided for other embodiments of the present application; Figure 22 Expansion structural schematic diagram of a first pole piece of a battery cell provided for other embodiments of the present application; Figure 23 For Figure 22 Partial enlarged structural schematic diagram of the first pole piece shown at A; Figure 24 Structural schematic diagram of a battery module provided for some embodiments of the present application; Figure 25 Structural schematic diagram of a battery pack provided for some embodiments of the present application; Figure 26 Structural schematic diagram of an electrical device provided for some embodiments of the present application.

[0117] The drawings are not necessarily drawn to actual scale.

[0118] Explanation of reference numerals in the drawings is as follows: 1. Electrical device; 2. Battery pack; 3. Controller; 4. Motor; 5. Box body; 5a. First box body part; 5b. Second box body part; 5c. Accommodating space; 6. Battery module; 61. First bus bar; 62. Second bus bar; 7. Battery cell; 10. Electrode assembly; 111, first pole ear; 1111, pole ear body; 1112, pole ear protrusion; 111a, first gathering portion; 111b, second gathering portion; 112, second pole ear; 13. first pole piece; 131. first straight section; 132. first bending section; 130. first coating portion; 14, second pole piece; 141, second straight section; 142, second bending section; 140, second coating portion; 15. Isolation film; 200, housing assembly; 20. Shell; 201. Electrode lead-out hole; 21. Shell; 22. End cover; 31, first electrode terminal; 311, bearing portion; 3110, inner wall; 3111, end wall; 3112, side wall; 33. Fixing parts; 32. a second electrode terminal; 41. A first adapter; 42. A second adapter. DETAILED DESCRIPTION

[0119] Hereinafter, the battery cells, battery devices and power devices of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0120] The "ranges" disclosed in this application are defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0121] If there is no special description, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0122] If there is no special description, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0123] If there is no special description, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0124] Due to the existence of resistance in the current conduction path, heat is inevitably generated during the cyclic charge and discharge process of the battery cell. For example, the electrode terminal is used to conduct the electrode assembly and the external circuit, and heat is generated at the electrode terminal. This part of the heat diffuses into the interior of the battery cell, increasing the temperature inside the battery cell. The active material is more likely to undergo high-temperature attenuation, shortening the cycle life of the battery cell and deteriorating the use reliability.

[0125] In view of this, the embodiments of the present application reasonably design the system of the battery cell. By adjusting the area of the first electrode terminal in the battery cell, the area of the first electrode terminal is relatively large, which can effectively reduce the contact resistance, lower the temperature of the battery cell, and improve the cycle stability of the active material, thereby improving the cycle life and service reliability of the battery cell.

[0126] Battery cell In a first aspect, an embodiment of the present application provides a battery cell.

[0127] As Figures 1 to 3 shown, the battery cell 7 includes a housing assembly 200 and an electrode assembly 10. The housing assembly 200 includes a housing 20 and a first electrode terminal 31 disposed on the housing 20. The electrode assembly 10 is received in the housing 20. The electrode assembly 10 includes a first electrode plate 13 and a second electrode plate 14. Both the first electrode plate 13 and the second electrode plate 14 include a coated portion and a tab. The coated portion includes an active material layer, and the tab does not include an active material layer. Among them, one of the first electrode plate 13 and the second electrode plate 14 is a positive electrode plate, and the other is a negative electrode plate. The active material layer in the positive electrode plate includes a positive active material, and the positive active material includes a lithium-containing phosphate with an olivine structure. The tab in the first electrode plate 13 is used to electrically connect the first electrode terminal 31 and the coated portion in the first electrode plate 13. The area of the projection plane of the first electrode terminal 31 along its own thickness direction is 200 mm 2 to 600 mm 2 .

[0128] The housing assembly 200 has a receiving space for receiving the electrode assembly 10. In some embodiments, the housing assembly 200 includes a housing 20. The housing 20 includes an end cap 22 and a housing body 21. The housing body 21 has an opening, and the end cap 22 covers the opening. The first electrode terminal 31 is disposed on the end cap 22. The shape of the housing body 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, a cylindrical housing body 21 can be selected; if the electrode assembly 10 is a cuboid structure, a cuboid housing body 21 can be selected. Optionally, both the electrode assembly 10 and the housing body 21 are cuboid structures. The thickness direction of the first electrode terminal 31 is parallel to the thickness direction of the end cap 22.

[0129] The battery cell 7 is a solid structure with length, thickness, and height. In the embodiments of the present application, the direction from the coated portion to the end cap 22 of the housing 20 can represent the height direction of the battery cell 7, and the thickness direction of the battery cell 7 is perpendicular to the direction from the coated portion to the end cap 22 of the housing 20. Figure 2 The Y direction shown in Figure 2The shown Z direction represents the direction pointing from the coated part to the end cap 22 of the housing 20. The Z direction is parallel to the thickness direction of the end cap 22 and also parallel to the thickness direction of the first electrode terminal 31. Figure 2 The shown W direction represents the first direction. The W direction, Y direction, and Z direction are perpendicular to each other in pairs.

[0130] The housing 21 of the battery cell 7 can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer housing 20 of the battery cell 7 can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0131] In some embodiments, the matrix material of the housing 21 includes steel. Steel has high mechanical strength and is not easily deformed, which can improve the reliability of use of the battery cell 7. In the embodiments of the present application, the matrix material refers to the material with the highest proportion in the housing 21.

[0132] When the housing 21 has a cuboid structure, the housing 21 includes two first shell parts 211 and two second shell parts 212. The two first shell parts 211 are arranged opposite to each other, and the two second shell parts 212 are arranged opposite to each other. The first shell part 211 is connected between the two second shell parts 212, and the area of the first shell part 211 is larger than the area of the second shell part 212.

[0133] In some embodiments, the matrix material of the housing 21 includes steel. Steel has high mechanical strength and is not easily deformed, which can improve the reliability of use and cycle performance of the battery cell. In the embodiments of the present application, the matrix material refers to the material with the highest proportion in the housing 21.

[0134] Optionally, when the matrix material of the housing 21 includes steel, the thickness of the housing 21 is 0.1 mm to 0.5 mm, and can be selected as 0.2 mm to 0.35 mm. Exemplarily, the thickness of the housing 21 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm or a range composed of any two of the above values. When the thickness of the housing 21 is within the above range, the mechanical strength of the housing 21 is high, which can improve the reliability of use of the battery cell 7; and the housing 21 occupies less space and there is more internal space in the housing 21, which is beneficial to improving the energy density of the battery cell 7.

[0135] In some embodiments, the matrix material of the housing 21 includes aluminum.

[0136] Optionally, when the matrix material of the housing includes aluminum, the thickness of the first shell part 211 is less than or equal to the thickness of the second shell part 212.

[0137] Exemplarily, the thickness of the first housing portion 211 is from 0.1 mm to 1.0 mm, and can be optionally from 0.3 mm to 0.8 mm. Exemplarily, the thickness of the first housing portion 211 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1.0 mm or a range composed of any two of the above values.

[0138] The thickness of the first housing portion 211 is relatively thin, so that the space occupied by the housing 21 is less, and the energy density of the battery cell 7 can be further improved.

[0139] Exemplarily, the thickness of the second housing portion 212 is from 0.1 mm to 1.0 mm, and can be optionally from 0.5 mm to 0.8 mm. Exemplarily, the thickness of the second housing portion 212 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1.0 mm or a range composed of any two of the above values.

[0140] The thickness of the second housing portion 212 is relatively thick, which can improve the overall mechanical strength of the housing 21 and reduce the risk of deformation of the housing 21.

[0141] In the embodiment of the present application, the projection plane of the first electrode terminal 31 along its own thickness direction means that the thickness direction of the first electrode terminal 31 is the normal line of the projection plane, that is, the projection plane is perpendicular to the thickness direction of the first electrode terminal 31, and this projection plane can represent the current-carrying area of the first electrode terminal 31.

[0142] The number of the first electrode terminals 31 can be one or more. When the number of the first electrode terminals 31 is multiple, multiple first electrode terminals 31 can all be used to connect the tabs of the first electrode plate 13. Multiple first electrode terminals 31 enable the first electrode terminals 31 and the tabs of the first electrode plate 13 to include multiple connection regions. Specifically, the first electrode plate 13 can be divided into multiple groups and welded to their respective corresponding first electrode terminals 31. Thereby, the connection area of a single first electrode terminal 31, such as the weld mark area, is reduced, the impedance at the connection can be reduced, and the heat generation can be reduced.

[0143] A plurality of first electrode terminals 31 can be located on the same side of the coating part, or on both sides of the coating part. When located on both sides of the coating part, for example, on both sides of the coating part along the Z direction, it can improve the internal current distribution behavior of the electrode sheet, equalize the current distribution, and is beneficial to further reduce the impedance; especially the impedance during the fast charging process can be effectively reduced.

[0144] The coating part is the part coated with the active material, which can carry out the insertion and extraction of active ions during the charge and discharge process of the battery cell 7. The coating part can include a current collecting part and an active material layer arranged on at least one side of the current collecting part; the tab is used for electrically connecting the coating part and the electrode terminal (such as the first electrode terminal 31), and the active material is not coated thereon.

[0145] In the embodiment of the present application, on the one hand, the area of the projection surface of the first electrode terminal 31 is increased, and the area of the projection surface of the first electrode terminal 31 is greater than or equal to 200 mm 2 , so that the contact area between the first electrode terminal 31 and the first tab 111 will not be too small, which can reduce the contact resistance between the first electrode terminal 31 and the first tab 111, reduce the heat generated by the first electrode terminal 31, and the temperature in the battery cell 7 system will not be too high, and the cycle stability of the active material is improved; even in the case of a large current density during fast charging, the heat generated by the first electrode terminal 31 will not be too much, which is beneficial to improving the cycle stability and use reliability of the active material; on the other hand, the positive electrode active material includes lithium-containing phosphate with an olivine structure, and this material has a stable structure during the charge and discharge process and is not prone to capacity decay, which is beneficial to further improving the cycle performance of the battery cell 7; and because the area of the projection surface of the first electrode terminal 31 is less than or equal to 600 mm 2 , the weight ratio of the electrode terminal in the battery cell 7 is relatively small, which is beneficial to improving the weight energy density of the battery cell 7.

[0146] Therefore, the embodiment of the present application can improve the cycle performance and weight energy density of the battery cell 7.

[0147] In the embodiment of the present application, the area of the projection surface of the first electrode terminal 31 along its own thickness direction is 200 mm 2 to 600 mm 2 , and can be selected as 300 mm 2 to 500 mm 2 . Exemplarily, the area of the projection surface of the first electrode terminal 31 along the thickness direction of the end cover 22 is 200 mm 2 , 220 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2, 350 mm 2 , 380 mm 2 , 400 mm 2 , 420 mm 2 , 450 mm 2 , 480 mm 2 , 500 mm 2 , 520 mm 2 , 550 mm 2 , 580 mm 2 , 600 mm 2 or a range composed of any two of the above values.

[0148] When the area of the projection plane of the first electrode terminal 31 along its own thickness direction is within the above range, the cycle performance and energy density of the battery cell 7 can be effectively improved.

[0149] In some embodiments, the housing assembly 200 further includes a second electrode terminal 32 disposed on the housing 20. The tab in the second electrode plate 14 is used to electrically connect the coated portion in the second electrode plate 14 and the second electrode terminal 32. Optionally, the second electrode terminal 32 may be disposed on the end cap 22.

[0150] Optionally, the area of the projection plane of the second electrode terminal 32 along its own thickness direction is 200 mm 2 to 600 mm 2 , and may be 300 mm 2 to 500 mm 2 . Exemplarily, the area of the projection plane of the second electrode terminal 32 along its own thickness direction is 200 mm 2 , 220 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2 , 350 mm 2 , 380 mm 2 , 400 mm 2 , 420 mm 2 , 450 mm 2 , 480 mm 2 , 500 mm 2 , 520 mm 2 , 550 mm 2 , 580 mm 2 , 600 mm 2 or a range composed of any two of the above values.

[0151] When the area of the projection surface of the second electrode terminal 32 in its own thickness direction is within the above range, the cycle performance and energy density of the battery cell 7 can be effectively improved.

[0152] The polarities of the first electrode tab 13 and the second electrode tab 14 are opposite. When the first electrode tab 13 is the positive electrode tab, the second electrode tab 14 is the negative electrode tab, the first electrode terminal 31 is the positive terminal, and the second electrode terminal 32 is the negative terminal; or when the first electrode tab 13 is the negative electrode tab, the second electrode tab 14 is the positive electrode tab, the first electrode terminal 31 is the negative terminal, and the second electrode terminal 32 is the positive terminal. The coated part in the positive electrode tab corresponds to the positive electrode coating part, the tab corresponds to the positive electrode tab, the active material layer corresponds to the positive electrode film layer containing the positive electrode active material, and the positive electrode coating part includes a positive electrode current collector part and a positive electrode film layer provided on at least one side of the positive electrode current collector part. The coated part in the negative electrode tab corresponds to the negative electrode coating part, the tab corresponds to the negative electrode tab, the active material layer corresponds to the negative electrode film layer containing the negative electrode active material, and the negative electrode coating part includes a negative electrode current collector part and a negative electrode film layer provided on at least one side of the negative electrode current collector part.

[0153] For example, the area of the projection surface of the positive terminal in its own thickness direction is 200 mm 2 to 600 mm 2 . Or the area of the projection surface of the negative terminal in its own thickness direction is 200 mm 2 to 600 mm 2 . Or the area of the projection surface of the positive terminal in its own thickness direction is 200 mm 2 to 600 mm 2 ; and the area of the projection surface of the negative terminal in its own thickness direction is 200 mm 2 to 600 mm 2 .

[0154] The electrode assembly 10 can be a wound structure or a stacked structure. Optionally, the electrode assembly 10 further includes a separator 15.

[0155] To illustrate the present application more clearly, the tab in the first electrode tab 13 is defined as the first tab 111, and the coated part in the first electrode tab 13 is defined as the first coating part 130; the tab in the second electrode tab 14 is defined as the second tab 112, and the coated part in the second electrode tab 14 is defined as the second coating part 140.

[0156] As Figures 3 to 5 shown, when the electrode assembly 10 is a wound structure, the first electrode tab 13, the separator 15 and the second electrode tab 14 are wound in one direction. Figure 4 The developed schematic diagram of the first electrode tab 13 is shown, and the first tab 111 is provided on one side or both sides of the first coating part 130, and can be optionally on one side; Figure 5The schematic diagram of the unfolded second pole piece 14 is shown. The second tab 112 is disposed on one side or both sides of the second coating portion 140, and preferably on one side.

[0157] In some embodiments, the dimension of the side of the first tab 111 facing the first coating portion 130 along the first direction W is from 30 mm to 50 mm, such as 30 mm, 32 mm, 35 mm, 38 mm, 40 mm, 42 mm, 45 mm, 48 mm, 50 mm, or any range composed of any two of the above values. Figure 4 The P1 shown represents the dimension of the side of the first tab 111 facing the first coating portion 130 along the first direction W. When the dimension of the first tab 111 meets the above range, the first tab 111 has good current-carrying capacity, which is beneficial to improving the heat dissipation effect.

[0158] When the first tab 111 is a positive tab, for example, when the material of the positive tab is aluminum, the cross-sectional area of the side of the first tab 111 facing the first coating portion 130 is greater than or equal to 0.45 mm 2 , and its upper limit depends on the thickness dimension of the first tab 111. This cross-section is parallel to the thickness direction of the positive tab. For example, the cross-sectional area of the first tab 111 is 0.45 mm 2 , 0.48 mm 2 , 0.50 mm 2 , 0.52 mm 2 , 0.55 mm 2 , 0.58 mm 2 , 0.60 mm 2 , 0.65 mm 2 , 0.70 mm 2 , 0.75 mm 2 , 0.80 mm 2 , 0.85 mm 2 , 0.90 mm 2 , 0.95 mm 2 , 1.0 mm 2 or any range composed of any two of the above values. When the cross-sectional area of the first tab 111 is within the above range, the first tab 111 has relatively strong current-carrying capacity and is also beneficial to rapid heat dissipation.

[0159] When the first tab 111 is a negative tab, for example, when the material of the negative tab is copper, the cross-sectional area of the side of the first tab 111 facing the first coating portion 130 is greater than or equal to 0.18 mm 2 , and its upper limit depends on the thickness dimension of the first tab 111. This cross-section is parallel to the thickness direction of the positive tab. For example, the cross-sectional area of the first tab 111 is 0.18 mm 2 , 0.20 mm 2 , 0.22 mm 2, 0.25 mm 2 , 0.28 mm 2 , 0.30 mm 2 , 0.32 mm 2 , 0.35 mm 2 , 0.38 mm 2 , 0.40 mm 2 , 0.42 mm 2 , 0.45 mm 2 , 0.48 mm 2 , 0.50 mm 2 , 0.52 mm 2 , 0.55 mm 2 , 0.58 mm 2 , 0.60 mm 2 , 0.65 mm 2 , 0.70 mm 2 , 0.75 mm 2 , 0.80 mm 2 , 0.85 mm 2 , 0.90 mm 2 , 0.95 mm 2 , 1.0 mm 2 Or a range composed of any two of the above values. The cross-sectional area of the first tab 111 is within the above range, and the current-carrying capacity of the first tab 111 is relatively strong, which is also beneficial for rapid heat dissipation.

[0160] In some embodiments, in the direction from the coated portion to the end cap 22 of the housing 20, that is, in the Z direction of the battery cell 7, the size of the first coating portion 130 is 60 mm to 120 mm. Exemplarily, the size of the first coating portion 130 in the Z direction is 60 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, 105 mm, 110 mm, 115 mm, 120 mm or a range composed of any two of the above values. Figure 4 P3 shown in represents the size of the first coating portion 130 in the Z direction.

[0161] The height and length dimensions of the battery cell 7 are limited. The energy density of the battery cell 7 can be increased by increasing the thickness dimension; and the thickness direction of the battery cell 7 is parallel to the width direction of the end cap 22. A thicker battery cell 7 is more beneficial for setting a wider end cap 22, and thus is beneficial for setting a large-sized first electrode terminal 31 and improving the current-carrying density of the first electrode terminal 31.

[0162] In some embodiments, the dimension of the second tab 112 along the first direction W on the side facing the second coating portion 140 is 30 mm to 50 mm, such as 30 mm, 32 mm, 35 mm, 38 mm, 40 mm, 42 mm, 45 mm, 48 mm, 50 mm, or a range composed of any two of the above values. Figure 5 P2 shown represents the dimension of the second tab 112 along the first direction W on the side facing the second coating portion 140. When the dimension of the second tab 112 meets the above range, the second tab 112 has good current-carrying capacity, which is beneficial to improving the heat dissipation effect.

[0163] In some embodiments, in the direction from the coating portion to the end cap 22 of the housing 20, that is, the Z direction of the battery cell 7, the dimension of the second coating portion 140 is 60 mm to 120 mm. Exemplarily, the dimension of the second coating portion 140 along the Z direction is 60 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, 105 mm, 110 mm, 115 mm, 120 mm, or a range composed of any two of the above values. Figure 5 P4 shown represents the dimension of the second coating portion 140 along the Z direction.

[0164] The height and length dimensions of the battery cell 7 are limited. The energy density of the battery cell 7 can be increased by increasing the thickness dimension; and the thickness direction of the battery cell 7 is parallel to the width direction of the end cap 22. A thicker battery cell 7 is more conducive to setting a wider end cap 22, thereby facilitating the setting of a large-sized second electrode terminal 32 and improving the current-carrying density of the second electrode terminal 32.

[0165] As Figures 6 to 8 shown, when the electrode assembly 10 is a laminated structure, the first electrode sheet 13 is at least one piece, optionally at least two pieces; the second electrode sheet 14 is at least one piece, optionally at least two pieces; the separator 15 is at least one piece, optionally at least two pieces. The first electrode sheet 13, the separator 15, and the second electrode sheet 14 are laminated along the thickness direction Y of the battery cell 7. Figure 7 The structural schematic diagram of the first electrode sheet 13 is shown. The first tab 111 is disposed on one or both sides of the first coating portion 130, optionally on both sides; Figure 8 The structural schematic diagram of the second electrode sheet 14 is shown. The second tab 112 is disposed on one or both sides of the second coating portion 140, optionally on both sides.

[0166] In some embodiments, the dimension of one side of the first tab 111 facing the first coating portion 130 along the first direction W is 30 mm to 80 mm, such as 30 mm, 32 mm, 35 mm, 38 mm, 40 mm, 42 mm, 45 mm, 48 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, or a range composed of any two of the above values. Figure 7 P1 shown represents the dimension of one side of the first tab 111 facing the first coating portion 130 along the first direction W. When the dimension of the first tab 111 satisfies the above range, the first tab 111 has good current-carrying capacity, which is beneficial to improving the heat dissipation effect.

[0167] When the first tab 111 is a positive tab, for example, when the material of the positive tab is aluminum, the cross-sectional area of one side of the first tab 111 facing the first coating portion 130 is greater than or equal to 0.45 mm 2 , and its upper limit depends on the thickness dimension of the first tab 111. This cross-section is parallel to the thickness direction of the positive tab. For example, the cross-sectional area of the first tab 111 is 0.45 mm 2 , 0.48 mm 2 , 0.50 mm 2 , 0.52 mm 2 , 0.55 mm 2 , 0.58 mm 2 , 0.60 mm 2 , 0.65 mm 2 , 0.70 mm 2 , 0.75 mm 2 , 0.80 mm 2 , 0.85 mm 2 , 0.90 mm 2 , 0.95 mm 2 , 1.0 mm 2 or a range composed of any two of the above values. When the cross-sectional area of the first tab 111 is within the above range, the first tab 111 has relatively strong current-carrying capacity and is also beneficial to rapid heat dissipation.

[0168] When the first tab 111 is a negative tab, for example, when the material of the negative tab is copper, the cross-sectional area of one side of the first tab 111 facing the first coating portion 130 is greater than or equal to 0.18 mm 2 , and its upper limit depends on the thickness dimension of the first tab 111. This cross-section is parallel to the thickness direction of the tab. For example, the cross-sectional area of the first tab 111 is 0.18 mm 2 , 0.20 mm 2 , 0.22 mm 2 , 0.25 mm 2 , 0.28 mm 2, 0.30 mm 2 , 0.32 mm 2 , 0.35 mm 2 , 0.38 mm 2 , 0.40 mm 2 , 0.42 mm 2 , 0.45 mm 2 , 0.48 mm 2 , 0.50 mm 2 , 0.52 mm 2 , 0.55 mm 2 , 0.58 mm 2 , 0.60 mm 2 , 0.65 mm 2 , 0.70 mm 2 , 0.75 mm 2 , 0.80 mm 2 , 0.85 mm 2 , 0.90 mm 2 , 0.95 mm 2 , 1.0 mm 2 Or a range formed by any two of the above values. The cross-sectional area of the first tab 111 is within the above range, and the current-carrying capacity of the first tab 111 is relatively strong, which is also conducive to rapid heat dissipation.

[0169] In some embodiments, in the direction from the coated portion to the end cap 22 of the housing 20, that is, the Z direction of the battery cell 7, the size of the first coating portion 130 is from 300 mm to 550 mm. Exemplarily, the size of the first coating portion 130 in the Z direction is 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm or a range formed by any two of the above values. Figure 7 P3 shown in represents the size of the first coating portion 130 in the Z direction.

[0170] The height and length dimensions of the battery cell 7 are limited, and the energy density of the battery cell 7 can be increased by increasing the thickness dimension; and the thickness direction of the battery cell 7 is parallel to the width direction of the end cap 22, and a thicker battery cell 7 is more conducive to setting a wider end cap 22, thereby facilitating the setting of a large-sized first electrode terminal 31 and increasing the current-carrying density of the first electrode terminal 31.

[0171] In some embodiments, the size of the side of the second tab 112 facing the second coating portion 140 in the first direction W is from 30 mm to 80 mm, such as 30 mm, 32 mm, 35 mm, 38 mm, 40 mm, 42 mm, 45 mm, 48 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm or a range formed by any two of the above values.Figure 8 The shown P2 represents the dimension of the side of the second tab 112 facing the second coating portion 140 along the first direction W. When the dimension of the second tab 112 meets the above range, the second tab 112 has good current-carrying capacity, which is beneficial to improving the heat dissipation effect.

[0172] In some embodiments, in the direction from the coating portion to the end cap 22 of the housing 20, that is, the Z direction of the battery cell 7, the dimension of the second coating portion 140 is 300 mm to 550 mm. Exemplarily, the dimension of the second coating portion 140 along the Z direction is 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm or a range composed of any two of the above values. Figure 8 The P4 shown therein represents the dimension of the second coating portion 140 along the Z direction.

[0173] The height and length dimensions of the battery cell 7 are limited. The energy density of the battery cell 7 can be increased by increasing the thickness dimension; and the thickness direction of the battery cell 7 is parallel to the width direction of the end cap 22. A thicker battery cell 7 is more conducive to setting a wider end cap 22, thereby facilitating the setting of a large-size second electrode terminal 32 and improving the current-carrying density of the second electrode terminal 32.

[0174] The first tab 111 and the first electrode terminal 31 can be directly connected or indirectly connected; when indirectly connected, the battery cell may further include a first adapter located between the first tab 111 and the first electrode terminal for electrically connecting the first tab 111 and the first electrode terminal.

[0175] Next, the case where the first tab is directly connected to the first electrode terminal will be described.

[0176] As Figure 9 and Figure 10 shown, in the case where the first tab 111 is directly connected to the first electrode terminal 31, the direct connection can shorten the current conduction path, reduce the resistance on the current conduction path, reduce the heat generation amount, and reduce the temperature inside the battery cell 7, thereby further improving the cycling performance of the battery cell 7. The first tab 111 and the first electrode terminal 31 can be electrically connected by welding, and the electrical connection position is the welding position of the first tab 111 and the first electrode terminal 31; the welding method is not limited. For example, it can be laser welding or ultrasonic welding the tabs into a single entity first and then laser welding. And according to factors such as the position, angle, or structure of the welding part, vertical welding, or inclined welding, etc., as well as lap welding, or edge sealing welding, etc. can be selected. The first tab 111 and the first electrode terminal 31 can also be electrically connected by other means, such as by setting conductive nails or conductive adhesives, etc.

[0177] In some embodiments, the outer casing 20 includes an electrode lead-out hole 201, the first electrode terminal 31 covers the electrode lead-out hole 201, and the first electrode terminal 31 is also connected to the side of the outer casing 20 facing the first coating portion 130 in the electrode assembly 10. Optionally, the end cap 22 includes the electrode lead-out hole 201, the first electrode terminal 31 is disposed on the end cap 22, and the first electrode terminal 31 is also connected to the side of the end cap 22 facing the first coating portion 130. The above arrangement is conducive to the direct connection between the first electrode terminal 31 and the first tab 111.

[0178] The first electrode terminal 31 can be a solid structure or a hollow structure, and a hollow structure is optional. When the first electrode terminal 31 is a hollow structure, it occupies less weight, which is beneficial to improving the weight energy density of the battery cell; part or all of the first tab 111 can be bundled in the hollow structure, saving the height space of the battery cell 7, which is beneficial to improving the volume energy density of the battery cell 7. Exemplarily, when the first electrode terminal 31 is a hollow structure, the first electrode terminal 31 includes a bearing portion 311 having a hollow structure, and at least a part of the first tab 111 is disposed in the bearing portion 311 and connected to the inner wall 3110 of the bearing portion 311. In other examples, a part of the first tab 111 is disposed in the bearing portion 311, but it may not be connected to the inner wall 3110 of the bearing portion 311. For example, a part of the first tab 111 is received in the bearing portion 311, and the other part is located outside the bearing portion 311 and connected to the surface of the first electrode terminal 31 facing the first coating portion 130. The electrical connection position between the first tab 111 and the first electrode terminal 31 is on the surface of the first electrode terminal 31 facing the first coating portion 130.

[0179] The bearing portion 311 is a solid structure having a receiving space and including an inner wall 3110. By disposing at least a portion of the first pole tab 111 in the bearing portion 311, the internal space occupied by the first pole tab 111 in the battery cell 7 can be reduced, and the available space in height of the first coating portion 130 can be increased, thereby increasing the volume energy density of the battery cell 7. At least a portion of the first pole tab 111 is disposed in the bearing portion 311, which means that the first pole tab 111 can be fully accommodated in the accommodation space or partially accommodated in the bearing portion 311. The first pole lug 111 is mechanically connected to the inner wall 3110 of the bearing portion 311, so that the first pole lug 111 and the first electrode terminal 31 can be electrically connected. Since the first pole lug 111 is accommodated in the bearing portion 311, the area where the first pole lug 111 is electrically connected to the first electrode terminal 31 can be set to be relatively large, which can reduce the difficulty of electrical connection and improve the reliability and stability of electrical connection. Moreover, when the first pole lug 111 and the first electrode terminal 31 are connected, such as by welding, the risk of foreign matter generated by welding falling into the first coating portion 130 can be reduced, and the interface of the pole piece can be optimized. By disposing at least a portion of the first pole lug 111 in the bearing portion 311, the internal space of the battery cell 7 occupied by the first pole lug 111 can be reduced, so that the volume energy density of the battery cell 7 can be improved.

[0180] Optionally, the inner wall 3110 includes an end wall 3111 and a side wall 3112, and the side wall 3112 is arranged around the end wall 3111, and the end wall 3111 and the side wall 3112 are arranged to form a load-bearing portion 311; for example, the end wall 3111 is connected to one side of the side wall 3112 along the thickness direction, the end wall 3111 is connected to the side of the side wall 3112 away from the first coating portion 130 along the thickness direction, or the end wall 3111 is connected to the side of the side wall 3112 facing the first coating portion 130 along the thickness direction; of course, the end wall 3111 can also be connected to both sides of the side wall 3112 along the thickness direction, and a through hole is opened on the side wall 3112 or the end wall 3111 to facilitate the introduction of the first pole ear 111 into the load-bearing portion 311.

[0181] The connection position between the first pole lug 111 and the first electrode terminal 31 can be located at the end wall 3111, or at the side wall 3112, or at both the end wall 3111 and the side wall 3112. The electrical connection is achieved through the connection of the mechanical structure, so that the bearing portion 311 not only has the function of accommodating the first pole lug 111, but also can achieve connection with the first pole lug 111, thereby simplifying the structure of the first electrode terminal 31 and facilitating the processing of the first electrode terminal 31; it can also simplify the structure of the first pole lug 111, reduce the redundancy of the first pole lug 111, and reduce the manufacturing cost of the first pole lug 111.

[0182] The first tab 111 is provided in multiple numbers. The multiple first tabs 111 are connected to the first coating portion 130. The first tabs 111 can be formed by die-cutting a structure without coated active material. The multiple first tabs 111 converge at a position close to the first coating portion 130 to form a first converging portion 111a. The multiple first tabs 111 are close to each other but not connected, and it can be understood that there are gaps between adjacent multiple first tabs 111. The multiple first tabs 111 converge and are connected at a position far from the first coating portion 130 to form a second converging portion 111b. The interlayer gaps between the multiple first tabs 111 are reduced, so that the fluffy multiple first tabs 111 are connected into an integral structure. For example, they are connected into an integral body by means such as welding, or can be formed into an integral structure by conductive adhesive, etc. Among them, the first converging portion 111a connects the second converging portion 111b and the first coating portion 130.

[0183] The multiple first tabs 111 converge at a position close to the first coating portion 130 to form a first converging portion 111a, and the multiple first tabs 111 converge and are connected at a position far from the first coating portion 130 to form a second converging portion 111b, which means that along the extending direction of the tab piece, the first converging portion 111a and the second converging portion 111b are arranged in sequence.

[0184] In the above technical solution, at least a part of the second converging portion 111b is accommodated in the carrier portion 311, which is convenient for connecting the first tab 111 and the first electrode terminal 31, can make full use of the space inside the first electrode terminal 31, reduce the occupied space of the first tab 111 inside the housing 20, accommodate a larger-sized first coating portion 130, and improve the volumetric energy density of the battery cell 7. The second converging portion 111b can be connected to the end wall 3111 and / or the second converging portion 111b is connected to the side wall 3112.

[0185] Furthermore, at least a part of the first converging portion 111a is accommodated in the carrier portion 311, which can further reduce the occupied space of the first tab 111 inside the housing 20, accommodate a larger-sized first coating portion 130, and improve the volumetric energy density of the battery cell 7.

[0186] Next, the case of indirect connection between the first tab and the first electrode terminal will be described.

[0187] As Figures 11 to 13 shown, in the case of indirect connection between the first tab 111 and the first electrode terminal 31, the battery cell 7 may further include a first adapter 41. The first adapter 41 is located between the first tab 111 and the first electrode terminal 31 and is used for electrically connecting the first tab 111 and the first electrode terminal 31.

[0188] In some embodiments, the outer casing 20 includes an electrode lead-out hole 201, the first electrode terminal 31 covers the electrode lead-out hole 201, and the first electrode terminal 31 is connected to one side of the outer casing 20 away from the coating portion. Optionally, the end cap 22 includes the electrode lead-out hole 201, the first electrode terminal 31 covers the electrode lead-out hole 201, and the first electrode terminal 31 is further connected to one side of the end cap 22 away from the first coating portion 130. This structural form enables the first electrode terminal 31 to hardly occupy the space inside the housing 21, which is beneficial to increasing the space utilization rate inside the housing 21, increasing the available space of the first coating portion 130, and improving the volumetric energy density of the battery cell 7. Specifically, the first electrode terminal 31 is connected to one side of the end cap 22 away from the first coating portion 130. Optionally, the first electrode terminal 31 can be connected to the end cap 22 through a fixing member 33. For example, the fixing member 33 can be an insulating fixing member, and the insulating fixing member is disposed on the outer periphery of the first electrode terminal 31 and located inside the electrode lead-out hole 201. In this structural form, the first electrode terminal 31 can be selected as a solid structure, which is beneficial to increasing the connection area between the first electrode terminal 31 and the first tab 111, increasing the current-carrying capacity, reducing the heat generation amount inside the battery cell 7, and improving the cycling performance of the battery cell 7.

[0189] In some embodiments, the area of the connection region between the first adapter 41 and the first electrode terminal 31 is 35 mm 2 to 50 mm 2 , such as 35 mm 2 , 38 mm 2 , 40 mm 2 , 42 mm 2 , 45 mm 2 , 48 mm 2 , 50 mm 2 or the range composed of any two of the above values. Figure 13 S1 shown in is the connection region between the first adapter 41 and the first electrode terminal 31. When they are welded, the connection region is the welding surface, and the area of the connection region is the welding area.

[0190] When the area of the connection region between the first adapter 41 and the first electrode terminal 31 is within the above range, the area of the connection region is relatively large. When laser welding is used, the area of the weld mark is relatively large, which can reduce the welding resistance, reduce heat generation, and improve the cycling performance of the battery cell 7.

[0191] In some embodiments, the area of the connection region between the first adapter 41 and the first tab 111 is 80 mm 2 to 160 mm 2 , such as 80 mm 2 , 90 mm 2 , 100 mm 2, 110 mm 2 , 120 mm 2 , 130 mm 2 , 140 mm 2 , 150 mm 2 , 160 mm 2 or a range formed by any two of the above values. Figure 13 The S2 shown represents the connection area between the first adapter 41 and the first tab 111. When the two are welded, the connection area is the welding surface, and the area of the connection area is the welding area.

[0192] The area of the connection area between the first adapter 41 and the first tab 111 is within the above range. The area of the connection area is relatively large. When laser welding is used, the weld mark area is relatively large, which can reduce the welding resistance, reduce heat generation, and improve the cycle performance of the battery cell 7.

[0193] In some embodiments, the first electrode terminal 31 is used to connect to an external first bus bar. The area of the connection area between the first electrode terminal 31 and the first bus bar is 60 mm 2 to 150 mm 2 , such as 60 mm 2 , 65 mm 2 , 70 mm 2 , 75 mm 2 , 80 mm 2 , 90 mm 2 , 100 mm 2 , 110 mm 2 , 120 mm 2 , 130 mm 2 , 140 mm 2 , 150 mm 22 or a range formed by any two of the above values. Figure 13 The S3 shown represents the connection area between the first electrode terminal 31 and the first bus bar. When the two are welded, the connection area is the welding surface.

[0194] The area of the connection area between the first electrode terminal 31 and the first bus bar is within the above range. The area of the connection area is relatively large. When laser welding is used, the weld mark area is relatively large, which can reduce the welding resistance, reduce heat generation, reduce the heat transfer amount to the inside of the battery cell 7, and improve the cycle performance of the battery cell 7.

[0195] In some embodiments, the first adapter 41 is located between the first tab 111 and the first electrode terminal 31; the projection plane of the connection area between the first adapter 41 and the first tab 111 along the thickness direction of the first electrode terminal is the first projection plane; the first electrode terminal 31 is used to connect with an external first bus bar, and the projection plane of the connection area between the first electrode terminal 31 and the first bus bar along the thickness direction of the first electrode terminal is the second projection plane, wherein the distance between the geometric centers of the first projection plane and the second projection plane is 0 to 50 mm, optionally 2 mm to 50 mm, for example 0, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm or the range composed of any two of the above values. Figure 13 In the figure, L1 represents the distance between the geometric centers of the first projection plane and the second projection plane.

[0196] The above settings enable an appropriate current conduction path between the first electrode terminal 31 and the first tab 111, which can effectively reduce the heat generation resistance, reduce the heat generation amount of the battery cell 7, and improve the cycle performance of the battery cell 7.

[0197] In some embodiments, the first adapter 41 is a positive adapter, and the thickness of the positive adapter is 0.6 mm to 2.0 mm, optionally 1.0 mm to 1.5 mm. For example, the thickness of the positive adapter is 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1 mm, 1.05 mm, 1.10 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, 1.5 mm or the range composed of any two of the above values.

[0198] When the first adapter 41 is a positive adapter, for example, when the material of the positive adapter is aluminum, the cross-sectional area of the first adapter 41 parallel to the thickness direction of the battery cell 7 is greater than or equal to 30 mm 2 , and its upper limit depends on the thickness dimension of the battery cell 7. For example, the cross-sectional area of the first adapter 41 is 30 mm 2 , 32 mm 2 , 35 mm 2 , 38 mm 2 , 40 mm 2 , 42 mm 2 , 45 mm 2 , 48 mm 2 , 50 mm 2 , 52 mm 2 , 55 mm 2 , 58 mm 2 , 60 mm 2Or a range composed of any two of the above numerical values. The cross-sectional area of the first adapter 41 is within the above range, and the current-carrying capacity of the first adapter 41 is relatively strong, which is also conducive to rapid heat dissipation.

[0199] When the thickness of the positive electrode adapter is within the above range, the current-carrying area of the positive electrode adapter is relatively large, which can reduce the heat generation resistance and the amount of heat generated; moreover, with an appropriate thickness, it is beneficial to the connection of the positive electrode adapter and other components such as the first tab 111 or the first electrode terminal 31. For example, during welding, the welding power requirement is appropriate and the welding quality is excellent.

[0200] In some embodiments, the first adapter 41 is a negative electrode adapter, and the thickness of the negative electrode adapter is from 0.5 mm to 1.5 mm, and can be selected from 0.6 mm to 1.2 mm. For example, the thickness of the negative electrode adapter is 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1 mm, 1.05 mm, 1.10 mm, 1.15 mm, 1.2 mm or a range composed of any two of the above numerical values.

[0201] When the first adapter 41 is a negative electrode adapter, for example, when the material of the negative electrode adapter is copper, the cross-sectional area of the first adapter 41 parallel to the thickness direction of the battery cell 7 is greater than or equal to 24 mm 2 , and its upper limit depends on the thickness dimension of the battery cell 7. For example, the cross-sectional area of the first adapter 41 is 24 mm 2 , 25 mm 2 , 28 mm 2 , 30 mm 2 , 32 mm 2 , 35 mm 2 , 38 mm 2 , 40 mm 2 , 42 mm 2 , 45 mm 2 , 48 mm 2 , 50 mm 2 , 52 mm 2 , 55 mm 2 , 58 mm 2 , 60 mm 2 Or a range composed of any two of the above numerical values. The cross-sectional area of the first adapter 41 is within the above range, and the current-carrying capacity of the first adapter 41 is relatively strong, which is also conducive to rapid heat dissipation.

[0202] When the thickness of the negative electrode adapter is within the above range, the current-carrying area of the negative electrode adapter is relatively large, which can reduce the heat generation resistance and the amount of heat generated. Moreover, the appropriate thickness is conducive to the connection between the negative electrode adapter and other components, such as the first tab 111 or the first electrode terminal 31. For example, during welding, the required welding power is appropriate and the welding quality is excellent.

[0203] In some embodiments, the housing 20 includes a housing body 21 and an end cap 22. The housing body 21 has a cuboid structure. The housing body 21 houses the electrode assembly 10 and has an opening. The end cap 22 covers the opening, and a first electrode terminal 31 is provided on the end cap 22. The size of the projection plane of the first electrode terminal 31 in its own thickness direction in the thickness direction of the battery cell 7 is a first dimension, and the size of the end cap 22 in the thickness direction of the battery cell 7 is a second dimension. The ratio of the first dimension to the second dimension is greater than 0 and less than or equal to 0.85, and can be selected from 0.40 to 0.85. Exemplarily, the ratio of the first dimension to the second dimension is 0.1, 0.2, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1 or the range composed of any two of the above values. Figure 14 In the figure, W1 represents the first dimension, and W2 represents the second dimension. The second dimension can also be understood as the width of the end cap 22.

[0204] The relatively high area occupancy of the first electrode terminal 31 on the end cap 22 is conducive to improving the current-carrying capacity of the first electrode terminal 31.

[0205] The structural and positional settings of the second electrode terminal 32 can be the same as or similar to those of the first electrode terminal 31, and will not be elaborated here.

[0206] In some embodiments, the battery cell 7 further includes a second adapter 42, which is located between the second tab 112 and the second electrode terminal 32 and is used for electrically connecting the second tab 112 and the second electrode terminal 32.

[0207] In some other embodiments, the second tab 112 and the second electrode terminal 32 are directly connected.

[0208] In some embodiments, the first electrode terminal 31 and the second electrode terminal 32 can be spaced apart on the end cap 22.

[0209] The structural form of the second tab 112 in the second electrode plate 14 is the same as that of the first tab 111 in the first electrode plate 13. For example, the second tab 112 in the second electrode plate 14 can include multiple ones, which will not be elaborated here.

[0210] In the embodiments of the present application, the electrode assembly 10 can be a stacked electrode assembly 10 or a wound electrode assembly 10.

[0211] When the electrode assembly 10 is of a stacked structure, the first electrode tab 13, the separator, and the second electrode tab 14 are stacked along the thickness direction of the battery cell 7, and the projection plane of the first electrode terminal 31 along its own thickness direction is rectangular.

[0212] In some embodiments, the electrode assembly 10 is of a stacked structure. The first electrode terminal 31 is connected to the tab of the first electrode tab, i.e., the first tab 111. The area of the connection region between the first electrode terminal 31 and the first tab 111 is 140 mm 2 to 420 mm 2 and is 210 mm 2 to 350 mm 2 such as 140 mm 2 、150 mm 2 、180 mm 2 、200 mm 2 、210 mm 2 、250 mm 2 、280 mm 2 、300 mm 2 、350 mm 2 、380 mm 2 、400 mm 2 、420 mm 2 or the range composed of any two of the above values. The above settings make the current conduction path between the first electrode terminal 31 and the first tab 111 appropriate, which can effectively reduce the heat generation resistance, reduce the heat generation amount of the battery cell 7, and improve the cycle performance of the battery cell 7.

[0213] When the electrode assembly 10 is of a wound structure, the first electrode tab 13, the separator, and the second electrode tab 14 are wound in one direction, and the projection plane of the first electrode terminal 31 along its own thickness direction is circular.

[0214] As Figure 15 shown, in some embodiments, the coated portion of the first electrode tab 13 includes a first straight section 131, the coated portion of the second electrode tab 14 includes a second straight section 141, the first straight section 131 and the second straight section 141 are stacked along the thickness direction Y of the electrode assembly 10, and the ratio of the number of tabs of the first electrode tab 13 to the number of the first straight sections 131 of the first electrode tab 13 is 0.5 to 2; the electrolyte includes an organic solvent, and the organic solvent includes a chain carboxylic acid ester solvent, and the mass content of the chain carboxylic acid ester solvent in the electrolyte is 6% to 65%.

[0215] The electrolyte includes the chain carboxylic ester solvent with the above mass content. The conductivity of this solvent system is relatively high, which is beneficial to the rapid migration of lithium ions and improves the fast charging performance of the battery cell 7; Under the fast charging system of the battery cell 7, the current density of the tab is usually relatively large, resulting in increased heat generation, making the temperature in the battery cell 7 relatively high, which easily leads to the attenuation of the active material and the decomposition of the organic solvent in the electrolyte, deteriorating the cycle performance. The positive electrode active material includes lithium-containing phosphate in the olivine structure. This material has a stable structure during charge and discharge and is not prone to capacity attenuation, which is beneficial to improving the cycle performance of the battery cell 7; At the same time, when the ratio of the number of tabs of the first electrode tab 13 to the number of the first straight section 131 of the first electrode tab 13 is within the above range, the shunting ability of the tab can be increased, and the fast charging performance of the battery cell 7 can be further improved. However, since the connection area between the tab and other components such as the coated part is relatively large, the overcurrent impedance can be effectively reduced, and the overcurrent temperature rise can be reduced, so that the temperature rise inside the battery cell 7 will not be too high, improving the stability of the electrolyte system and the stability of the active material, which is beneficial to improving the use reliability of the battery cell 7 and can improve the cycle performance. And there are more connection sites between the tab and the coated part, etc., which can increase connection redundancy such as welding redundancy and effectively improve the product yield.

[0216] Therefore, the embodiments of the present application can improve the cycle performance and fast charging performance of the battery cell 7.

[0217] The first electrode tab 13 and the second electrode tab 14 have opposite polarities. When the first electrode tab 13 is a positive electrode tab, the second electrode tab 14 is a negative electrode tab, the first electrode terminal 31 is a positive terminal, and the second electrode terminal 32 is a negative terminal; or when the first electrode tab 13 is a negative electrode tab, the second electrode tab 14 is a positive electrode tab, the first electrode terminal 31 is a negative terminal, and the second electrode terminal 32 is a positive terminal.

[0218] The coated part in the positive electrode tab corresponds to the positive electrode coated part, the tab corresponds to the positive electrode tab, the active material layer corresponds to the positive electrode film layer containing the positive electrode active material. The positive electrode coated part includes a positive electrode current collector part and a positive electrode film layer provided on at least one side of the positive electrode current collector part. When the positive electrode coated part includes a positive electrode straight section, the positive electrode straight section includes a positive electrode current collector part and a positive electrode film layer provided on at least one side of the positive electrode current collector part.

[0219] The coated part in the negative electrode tab corresponds to the negative electrode coated part, the tab corresponds to the negative electrode tab, the active material layer corresponds to the negative electrode film layer containing the negative electrode active material. The negative electrode coated part includes a negative electrode current collector part and a negative electrode film layer provided on at least one side of the negative electrode current collector part. When the negative electrode coated part includes a negative electrode straight section, the negative electrode straight section includes a negative electrode current collector part and a negative electrode film layer provided on at least one side of the negative electrode current collector part.

[0220] In the embodiment of the present application, the first tab 111 is electrically connected to the first straight section 131 and the first electrode terminal 31. The ratio of the number of the first tabs 111 of the first electrode plate 13 to the number of the first straight sections 131 of the first electrode plate 13 is 0.5 to 2, such as 0.5, 0.55, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 or the range composed of any two of the above values. When the ratio of the number of the first tabs 111 of the first electrode plate 13 to the number of the first straight sections 131 of the first electrode plate 13 is within the above range, the number of the first tabs 111 is relatively large, which can improve the shunt effect, reduce the over-current impedance between the first tab 111 and the first straight section 131, reduce the over-current temperature rise, and make the temperature rise inside the battery cell 7 relatively low.

[0221] In the embodiment of the present application, the electrode assembly 10 includes a second straight section 141. The second straight section 141 and the first straight section 131 are stacked, and are alternately stacked along the thickness direction Y of the electrode assembly 10. The second tab 112 is used to electrically connect the second straight section 141 and the second electrode terminal 32. Optionally, the battery cell 7 further includes a separator 15. The first straight section 131, the separator 15 and the second straight section 141 are alternately stacked.

[0222] In some embodiments, the ratio of the number of the second tabs 112 of the second electrode plate 14 to the number of the second straight sections 141 of the second electrode plate 14 is 0.5 to 2, such as 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 or the range composed of any two of the above values. When the ratio of the number of the second tabs 112 of the second electrode plate 14 to the number of the second straight sections 141 of the second electrode plate 14 is 0.5 to 2, the number of the second tabs 112 is relatively large, which can improve the shunt effect, reduce the over-current impedance between the second tab 112 and the second straight section 141, reduce the over-current temperature rise, and make the temperature rise inside the battery cell 7 relatively low.

[0223] When the number of the first tabs 111 is the same as that of the second tabs 112, the over-current density of a single tab is the same, and the performance matching is more excellent, which is beneficial to improving the homogenization reaction of the battery cell 7, improving the shunt effect, and improving the charge and discharge capacity of the battery cell 7.

[0224] In some embodiments, the first tab 111 is a positive tab; the first flat section 131 includes a positive active material, and the positive active material includes a lithium-containing phosphate in an olivine structure for providing lithium ions. The relatively large number of positive tabs can improve the current shunting effect, reduce the over-current impedance between the first tab 111 and the first flat section 131, reduce the over-current temperature rise, and result in a lower temperature rise inside the battery cell 7.

[0225] In some embodiments, the second tab 112 is a negative tab, the second flat section 141 includes a negative active material, and the negative active material includes a carbon-based material for receiving lithium ions from the first flat section 131.

[0226] The electrode assembly 10 can be a wound electrode assembly 10 or a stacked electrode assembly 10.

[0227] In the case where the electrode assembly 10 is in a wound structure, structurally, the electrode assembly 10 includes a first electrode sheet 13, a second electrode sheet 14, and a separator 15. The first electrode sheet 13 can be a single-piece structure, the second electrode sheet 14 is a single-piece structure, and the separator 15 is a single-piece structure. The separator 15 is disposed between the first electrode sheet 13 and the second electrode sheet 14. The first electrode sheet 13, the separator 15, and the second electrode sheet 14 are wound in one direction to form the electrode assembly 10. The first electrode sheet 13 includes a first coating portion 130 and a plurality of first tabs 111. The second electrode sheet 14 includes a second coating portion 140 and a plurality of second tabs 112.

[0228] After winding to form the electrode assembly 10, the first coating portion 130 of the first electrode sheet 13 can include a plurality of first flat sections 131 and a plurality of first bent sections 132. The first bent sections 132 are arranged along the winding direction of the electrode assembly 10 with respect to the first flat sections 131, and the first bent sections 132 are connected to the first flat sections 131. The first tabs 111 are connected to the first flat sections 131. During the process of winding to form the electrode assembly 10, one first flat section 131 can be formed when the first electrode sheet 13 is wound half a turn.

[0229] The second coating portion 140 of the second electrode sheet 14 can include a plurality of second flat sections 141 and a plurality of second bent sections 142. The second bent sections 142 are arranged along the winding direction of the electrode assembly 10 with respect to the second flat sections 141, and the second bent sections 142 are connected to the second flat sections 141. The second tabs 112 are connected to the second flat sections 141. The first flat sections 131 and the second flat sections 141 are alternately stacked, and the first bent sections 132 and the second bent sections 142 are alternately stacked.

[0230] In terms of the external shape, the electrode assembly 10 includes a flat region, a bent region, and a tab. The flat region includes a first flat section 131 and a second flat section 141. The bent region includes a first bent section 132 and a second bent section 142.

[0231] When the electrode assembly 10 is of a wound structure, the ratio of the number of the first tabs 111 of the first electrode sheet 13 to the number of the first flat sections 131 of the first electrode sheet 13 can be selected to be 0.5 to 1, can be selected to be greater than 0.5 and less than 1, and can be further selected to be 0.6 to 0.99; it can further cooperate with a chain carboxylic ester solvent with a mass content of 6% to 65% to improve the cycle performance and fast charging performance of the battery cell 7. Exemplarily, when the electrode assembly 10 is of a wound structure, the ratio of the number of the first tabs 111 of the first electrode sheet 13 to the number of the first flat sections 131 of the first electrode sheet 13 is 0.5, 0.55, 0.6, 0.7, 0.8, 0.9, 0.95, 0.99, 1 or a range composed of any two of the above values.

[0232] Figure 15 The case where the ratio of the number of the first tabs 111 of the first electrode sheet 13 to the number of the first flat sections 131 of the first electrode sheet 13 is 0.5 is shown. When the first electrode sheet 13 is wound once, two first flat sections 131 can be formed. One of the two first flat sections 131 is connected to a first tab 111, which means that there is one first tab 111 corresponding to the two first flat sections 131, that is, one of the two first flat sections 131 is provided with a first tab 111, and the other first flat section 131 is not provided with a first tab 111, which can be converted to 0.5 first tabs 111 are provided on each first flat section 131.

[0233] Figure 16 The case where the ratio of the number of the first tabs 111 of the first electrode sheet 13 to the number of the first flat sections 131 of the first electrode sheet 13 is 1 is shown. When the first electrode sheet 13 is wound once, two first flat sections 131 can be formed, and each first flat section 131 is connected to a first tab 111, which can be converted to that one first tab 111 is provided on each first flat section 131.

[0234] Figure 17It shows a case where the ratio of the number of the first tabs 111 of the first electrode tab 13 to the number of the first flat segments 131 of the first electrode tab 13 is greater than 0.5 and less than 1. The first electrode tab 13 is wound around multiple turns, and two first flat segments 131 can be formed in each turn. One first tab 111 can be provided on at least one of the two first flat segments 131 in at least one of the multiple turns, that is, one first tab 111 is provided in one turn; two first tabs 111 can be provided on at least one of the two first flat segments 131 in at least another one of the multiple turns, that is, two first tabs 111 are provided in one turn; in the electrode assembly 10, it can be converted that there are more than 0.5 and less than 1 first tabs 111 provided on each first flat segment 131.

[0235] When the battery cell 7 satisfies the above conditions, the conductivity of the solvent system is relatively high, which is beneficial to the rapid migration of lithium ions and can improve the rapid charging performance of the battery cell 7; moreover, the electrolyte system has an excellent protective effect on the negative active material, which is beneficial to the improvement of the cycle performance of the battery cell 7; when the ratio of the number of the first tabs 111 to the number of the first flat segments 131 is within the above range, the shunt capacity of the first tabs 111 can be increased, which is beneficial to the uniform reaction of the first electrode tab 13 and the reduction of impedance, and can further improve the rapid charging performance of the battery cell 7, and can also increase the connection sites between the first tabs 111 and other components, increase the welding redundancy, and effectively improve the product yield; since the connection area between the first tabs 111 and other components is relatively large, the overcurrent impedance can be reduced, the overcurrent temperature rise can be reduced, and the temperature rise in the battery cell 7 system will not be too high, so that the electrolyte system is more stable, which is beneficial to the improvement of the use reliability of the battery cell 7 and can improve the cycle performance.

[0236] Optionally, the number of the first tabs 111 in the first electrode tab 13 is multiple, and the first tabs 111 are located on at least one side of the first coating portion 130.

[0237] The electrode assembly 10 can be provided as at least one, optionally at least two, such as two, three, four, etc., and optionally two. At least two electrode assemblies 10 can be stacked along the thickness direction Y of the electrode assembly 10.

[0238] As Figures 18 to 21 As shown, when the electrode assembly 10 is a stacked structure, there can be multiple first electrode tabs 13 and multiple second electrode tabs 14. Each first electrode tab 13 respectively has a first flat segment 131 and a first tab 111. The first flat segments 131 of the multiple first electrode tabs 13 and the second flat segments 141 of the multiple second electrode tabs 14 are stacked along the thickness direction Y of the electrode assembly 10.

[0239] When the electrode assembly 10 has a stacked structure, from the external shape, the electrode assembly 10 includes a flat region. Optionally, the electrode assembly 10 may also include a bent region. For example, when the separator 15 has a one-piece structure, the separator 15 is bent multiple times and then laminated with the first electrode tab 13 and the second electrode tab 14 to form the electrode assembly 10. Or when the negative electrode tab has a one-piece structure, the negative electrode tab is bent multiple times and then laminated with the positive electrode tab and the separator to form the electrode assembly. Next, an example will be given with the electrode assembly 10 only including a flat region.

[0240] From the structural perspective, the electrode assembly 10 includes a first electrode tab 13, a second electrode tab 14, and a separator 15. The separator 15 is disposed between the first electrode tab 13 and the second electrode tab 14, and the first electrode tab 13, the separator 15, and the second electrode tab 14 are laminated.

[0241] There may be multiple first electrode tabs 13 and multiple second electrode tabs 14. Each first electrode tab 13 includes a first flat section 131 and a first tab 111, and the first tab 111 is connected to the first flat section 131. Each second electrode tab 14 includes a second flat section 141 and a second tab 112, and the second tab 112 is connected to the second flat section 141. The multiple first flat sections 131 and the multiple second flat sections 141 are alternately laminated along the thickness direction Y of the electrode assembly 10.

[0242] When the electrode assembly 10 has a stacked structure, the ratio of the number of the first tabs 111 of the first electrode tab 13 to the number of the first flat sections 131 of the first electrode tab 13 is from 1 to 2, and can be selected to be greater than 1 and less than or equal to 2. In combination with a chain carboxylic ester solvent with a mass content of 6% to 65%, it can effectively improve the performance of the battery cell 7. Exemplarily, when the electrode assembly 10 has a stacked structure, the ratio of the number of the first tabs 111 of the first electrode tab 13 to the number of the first flat sections 131 of the first electrode tab 13 is 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a range composed of any two of the above values.

[0243] When the ratio of the number of the first tabs 111 of the first electrode tab 13 to the number of the first flat sections 131 of the first electrode tab 13 is 1, it means that the first tabs 111 and the first flat sections 131 are arranged in a one-to-one correspondence, and it can be converted to that one first tab 111 is provided on each first flat section 131. Figure 10 The structural schematic diagram showing that one first tab 111 is provided on each first flat section 131 is shown.

[0244] When the ratio of the number of the first tab 111 of the first electrode sheet 13 to the number of the first straight section 131 of the first electrode sheet 13 is 2, it can be converted that two first tabs 111 are provided on each first straight section 131. In this case, one first tab 111 can be provided on each side of the first straight section 131. Figure 11 The structural schematic diagram shows that two first tabs 111 are provided on each first straight section 131.

[0245] When the ratio of the number of the first tabs 111 of the first electrode sheet 13 to the number of the first straight sections 131 of the first electrode sheet 13 can be selected to be greater than 1 and less than or equal to 2, it can be converted that more than 1 and less than or equal to 2 first tabs 111 are provided on each first straight section 131. For example, the electrode assembly 10 includes two first electrode sheets 13, one of the first electrode sheets 13 is provided with one first tab 111, and the other first electrode sheet 13 is provided with two first tabs 111. After conversion, 1.5 first tabs 111 are provided on each first electrode sheet 13.

[0246] When the battery cell 7 meets the above conditions, the conductivity of the solvent system is relatively high, which is beneficial to the rapid migration of lithium ions and can improve the rapid charging performance of the battery cell 7; moreover, the electrolyte system has an excellent protective effect on the negative active material, which is beneficial to the improvement of the cycle performance of the battery cell 7; the number of the first tabs 111 is relatively large, which can increase the shunt capacity of the first tabs 111, make the internal shunt of the first straight section 131 uniform, and can further improve the rapid charging performance of the battery cell 7. Moreover, it can also increase the connection sites between the first tabs 111 and other components, increase the welding redundancy, and effectively improve the product yield; since the connection area between the first tabs 111 and other components is relatively large, the overcurrent impedance can be reduced, the overcurrent temperature rise can be reduced, and the temperature rise in the battery cell 7 system will not be too high, so that the electrolyte system is more stable, which is beneficial to the improvement of the use reliability of the battery cell 7 and can improve the cycle performance.

[0247] Optionally, when the ratio of the number of the first tabs 111 of the first electrode sheet 13 to the number of the first straight sections 131 of the first electrode sheet 13 is greater than 1, after conversion, more than 1 first tabs 111 are provided on the first straight section 131 on average. More than 1 first tabs 111 can be respectively provided on both sides of the first straight section 131. In this case, more than 1 first tabs 111 can share the current density of a single first electrode sheet 13. Especially when the area of the first electrode sheet 13 is relatively large, the internal shunt of the first electrode sheet 13 is relatively uniform, which is beneficial to the homogenization reaction and reduces the impedance.

[0248] Optionally, when the ratio of the number of first pole ears 111 of the first pole piece 13 to the number of first straight sections 131 of the first pole piece 13 is greater than 1, after conversion, when there are more than one first pole ears 111 on average on the first straight section 131, more than one first pole ears 111 can be arranged on the same side of the first straight section 131. In this case, welding redundancy can be increased, thereby effectively improving product yield.

[0249] The arrangement of the second pole tab 112 can be the same or similar to that of the first pole tab 111, which will not be described in detail. For example, the ratio of the number of the second pole tabs 112 of the second pole piece 14 to the number of the second straight sections 141 of the second pole piece 14 is 1 to 2, which can be greater than 1 and less than or equal to 2.

[0250] When the electrode assembly 10 is a laminated structure, when the number of the first pole lug 111 and the second pole lug 112 is the same, the overcurrent density of a single pole lug is the same, and the performance matching is more excellent, which is beneficial to improving the uniform reaction of the battery cell 7, enhancing the shunt effect, and improving the charge and discharge capacity of the battery cell 7.

[0251] Regardless of whether the electrode assembly 10 is a wound structure or a laminated structure, the first electrode tab 111 is connected to at least one side of the first coating portion 130 .

[0252] like Figure 22 and Figure 23 As shown, in some embodiments, the first pole tab 111 includes a pole tab body 1111 and a plurality of pole tab protrusions 1112, the plurality of pole tab protrusions 1112 are all connected to a side of the pole tab body 1111 away from the first coating portion 130, and there is a gap between two adjacent pole tab protrusions 1112. Of course, the first pole tab 111 may also include only the pole tab body 1111. Figure 22 A schematic diagram of unfolding the first pole piece 13 in the electrode assembly 10 of the wound structure is shown.

[0253] The arrangement of multiple pole lug protrusions 1112 enables the first pole lug 111 to have multiple connection sites. For example, when connecting the first pole lug 111 to the first adapter 41, the multiple pole lug protrusions 1112 can be respectively connected to different positions of the first adapter 41, such as by welding. This can increase the welding positions of the first pole lug 111 and the first adapter 41, improve the welding yield, and enhance the stability of the connection between the two.

[0254] The structure of the second electrode tab 112 may be the same as or similar to that of the first electrode tab 111 , and will not be described in detail herein.

[0255] In some embodiments, the first tab 111 is a positive tab, and the thickness of the positive tab is from 10 μm to 20 μm, optionally from 10 μm to 15 μm. Exemplarily, the thickness of the positive tab is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm or a range composed of any two of the above values. When the thickness of the positive tab is within the above range, the current-carrying capacity of the positive tab is relatively excellent, which can reduce heat generation and is beneficial to improving the fast charging performance of the battery cell.

[0256] In some embodiments, the first tab 111 is a negative tab, and the thickness of the negative tab is from 4 μm to 10 μm, optionally from 4 μm to 6 μm. Exemplarily, the thickness of the negative tab is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm or a range composed of any two of the above values. When the thickness of the negative tab is within the above range, the current-carrying capacity of the negative tab is relatively excellent, which can reduce heat generation and is beneficial to improving the fast charging performance of the battery cell.

[0257] In the embodiments of the present application, the thickness of the tab has the meaning in the art and can be detected by detecting devices and methods well-known in the art. For example, the thickness measured by a micrometer.

[0258] [Positive electrode plate] The positive electrode plate includes a positive current collector portion and a positive electrode film layer provided on at least one surface of the positive current collector portion and including a positive electrode active material. For example, the positive current collector portion has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive current collector portion.

[0259] In the embodiments of the present application, the charging upper limit voltage and the discharging cut-off voltage of the battery cell are different according to different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the charging upper limit voltage can be 3.65 V and the discharging cut-off voltage can be 2.0 V. Also, for example, when the phosphate material includes lithium manganese iron phosphate, the charging upper limit voltage can be 4.3 V and the discharging cut-off voltage can be 2.0 V.

[0260] The 100% state of charge (SOC) and 0% state of charge (SOC) of the battery cell are defined as follows: Charge the battery cell at a constant current charge rate of 0.33C to the upper limit voltage of the battery, and then charge it at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell; discharge the battery cell at a constant current discharge rate of 0.33C to the cut-off voltage, corresponding to the state of 0% SOC of the battery cell.

[0261] In some embodiments, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode film layer is 2.50 g / cm 3 to 2.80 g / cm 3 ; optionally 2.55 g / cm 3 to 2.70 g / cm 3 . Exemplarily, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode film layer is 2.50 g / cm 3 , 2.52 g / cm 3 , 2.55 g / cm 3 , 2.56 g / cm 3 , 2.57 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.62 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm 3 , 2.80 g / cm 3 or the range composed of any two of the above values.

[0262] When the compaction density of the positive electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the positive electrode active materials in the positive electrode film layer are stacked relatively tightly, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0263] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 to 370 mg / 1540.25 mm 2 ; optionally 240 mg / 1540.25 mm 2 to 330 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 , 210 mg / 1540.25 mm 2 , 220 mg / 1540.25 mm2 、230 mg / 1540.25 mm 2 、240 mg / 1540.25 mm 2 、250 mg / 1540.25 mm 2 、260 mg / 1540.25 mm 2 、270 mg / 1540.25 mm 2 、280 mg / 1540.25 mm 2 、290 mg / 1540.25 mm 2 、300 mg / 1540.25 mm 2 、310 mg / 1540.25 mm 2 、320 mg / 1540.25 mm 2 、330 mg / 1540.25 mm 2 、340 mg / 1540.25 mm 2 、350 mg / 1540.25 mm 2 、360 mg / 1540.25 mm 2 、370 mg / 1540.25 mm 2 or a range composed of any two of the above values.

[0264] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode plate will not be too large, and it can take into account improving the energy density of the battery cell.

[0265] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell in the 100% state of charge (SOC) has the meaning well known in the art, that is, the positive electrode plate is disassembled from the battery cell in the 100% state of charge (SOC), and the compaction density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode plate (if it is a double-sided coated plate, one side of the positive electrode film layer can be wiped off first) is punched into small circular pieces with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then, the positive electrode film layer of the above-mentioned weighed positive electrode plate is wiped off, and the weight of the positive electrode current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode film layer = (the weight M1 of the positive electrode plate - the weight M0 of the positive electrode current collector) / S1, the thickness of the positive electrode film layer = the thickness H1 of the positive electrode plate - the thickness H0 of the positive electrode current collector, and the compaction density of the positive electrode film layer = the single-sided coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0266] In some embodiments, the powder resistivity of the positive electrode active material is from 1 Ω·cm to 27.5 Ω·cm; optionally, less than or equal to 20 Ω·cm; optionally, less than or equal to 11 Ω·cm. Exemplarily, the powder resistivity of the positive electrode active material can be 27.5 Ω·cm, 20 Ω·cm, 19 Ω·cm, 18 Ω·cm, 17 Ω·cm, 16 Ω·cm, 15 Ω·cm, 14 Ω·cm, 13 Ω·cm, 12 Ω·cm, 11 Ω·cm, 10 Ω·cm, 9 Ω·cm, 8 Ω·cm, 7 Ω·cm, 6 Ω·cm, 5 Ω·cm, 4 Ω·cm, 3 Ω·cm, 2 Ω·cm, 1 Ω·cm or the range composed of any two of the above values.

[0267] The relatively low powder resistivity of the positive electrode active material results in a relatively low resistance of the positive electrode sheet and less heat generation of the battery cell.

[0268] In the embodiments of the present application, the powder resistivity of the material has the meaning well-known in the art and can be detected by methods and equipment well-known in the art. For example, according to the test standard GB / T30835-2014, a PRCD1100 powder resistivity meter is used for testing.

[0269] In some embodiments, the powder compaction density of the positive electrode active material under 30000 N is 2.46 g / cm 3 to 2.8 g / cm 3 . Exemplarily, the powder compaction density of the positive electrode active material under 30000 N is 2.46 g / cm 3 , 2.47 g / cm 3 , 2.48 g / cm 3 , 2.49 g / cm 3 , 2.5 g / cm 3 , 2.51 g / cm 3 , 2.55 g / cm 3 , 2.58 g / cm 3 , 2.60 g / cm 3 , 2.65 g / cm 3 , 2.68 g / cm 3 , 2.70 g / cm 3 , 2.72 g / cm 3 , 2.75 g / cm 3 , 2.78 g / cm 3 , 2.80 g / cm 3 or the range composed of any two of the above values.

[0270] When the powder compaction density of the positive electrode active material is within the above range under 30,000 N, the energy density of the battery cell can be improved. Moreover, since the positive electrode active material in the positive electrode film layer can be stacked more closely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0271] In the embodiments of the present application, the powder compaction density of the material has the meaning well-known in the art and can be detected by methods and equipment well-known in the art. Detection is carried out according to the test standard GB / T24533-2009. For example, a certain amount of positive electrode active material is taken as a sample and added to a mold with a bottom area of 1.327 cm 2 in the UTM7305 type electronic pressure testing machine, pressurized to 3000 kg (equivalent to 30,000 N), kept under pressure for 30 s, then the pressure is released, kept for 10 s, and then the powder compaction density of the positive electrode active material under the action of 30,000 N is recorded and calculated.

[0272] In some embodiments, the charging specific capacity of the positive electrode active material at a 0.1C rate is 150 mAh / g to 170 mAh / g, and can be optionally 157 mAh / g to 170 mAh / g. Exemplarily, the charging specific capacity of the positive electrode active material at a 0.1C rate is 150 mAh / g, 151 mAh / g, 152 mAh / g, 153 mAh / g, 154 mAh / g, 155 mAh / g, 156 mAh / g, 157 mAh / g, 158 mAh / g, 159 mAh / g, 160 mAh / g, 161 mAh / g, 162 mAh / g, 163 mAh / g, 164 mAh / g, 165 mAh / g, 166 mAh / g, 167 mAh / g, 168 mAh / g, 169 mAh / g, 170 mAh / g or the range composed of any two of the above values.

[0273] When the charging specific capacity of the positive electrode active material at a 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0274] In the embodiments of the present application, the specific capacity of the active material has the meaning well-known in the art and can be tested by equipment and methods well-known in the art. The test method of the first Coulomb efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be adopted. Using metallic lithium as the negative electrode and the sample electrode sheet containing the above materials as the positive electrode, a half-button battery is assembled. Under the condition of 23°C ± 2°C, the half-button battery is placed on a battery tester or other test equipment with the same performance, and the charge-discharge capacity is obtained through charging and discharging at a 0.1C rate, and then the capacity is divided by the mass of the active material of the electrode sheet to obtain the charging specific capacity parameter.

[0275] In some embodiments, the mass percentage of the lithium-containing phosphate with an olivine structure in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%. It can be considered that the positive electrode active material of this application is a lithium-containing phosphate system with an olivine structure. When the mass percentage of the lithium-containing phosphate with an olivine structure is less than 100%, the positive electrode active material can also include common positive electrode active materials, such as, but not limited to, at least one of lithium-containing transition metal oxides and lithium-containing phosphates. Examples of the lithium-containing transition metal oxides can include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of the lithium-containing phosphates can include, but are not limited to, at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0276] Optionally, the mass percentage of the lithium-containing phosphate with an olivine structure in the positive electrode active material is 100%.

[0277] In the embodiments of this application, the lithium-containing phosphate with an olivine structure can be phosphate particles or a material obtained by coating and modifying them. For example, the lithium-containing phosphate with an olivine structure includes phosphate particles and a coating layer, and the coating layer is coated on the surface of the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

[0278] By coating the surface of the phosphate particles with the coating layer, the conductivity of the lithium-containing phosphate with an olivine structure can be improved, the powder resistivity of the material can be reduced, and it is beneficial to the migration rate of lithium ions, improving the fast charging ability of the battery and reducing the heat generation of the battery cell.

[0279] In some embodiments, the phosphate particles include a general formula of Li x1 A y1 Me a M b P 1-c X c Y zA compound, wherein 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A includes one or more of Na, K, and Mg, Me includes one or more of Mn, Fe, Co, and Ni, M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, X includes one or more of S, Si, Cl, B, C, and N, and Y includes one or more of O and F. The cyclic stability of the phosphate particles is relatively excellent, which is beneficial to improving the cyclic performance of the battery cell.

[0280] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charge and discharge process of the battery cell, the insertion and extraction and consumption of active ions such as Li will occur, and the molar content of Li is different when the battery cell is discharged to different states. In the enumeration of the cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of Li is the initial state of the material, that is, the state before feeding. When the cathode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li may change. In the embodiments of the present application, in the enumeration of the cathode active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of oxygen O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen O to change. Actually, the molar content of oxygen O will fluctuate, and the above situations are all within the protection scope of the present application.

[0281] In some embodiments, the coating layer includes a fast ion conductor with the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 , where M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0 ≤ d ≤ 1, 0 < x2 < 5, and 0 < y2 < 4.

[0282] Exemplarily, the fast ion conductor is a material with a NASICON structure, such as including one or more of lithium iron titanium phosphate Li2FeTi(PO4)3, lithium iron zirconium phosphate Li2FeZr(PO4)3, and lithium iron tin phosphate Li2FeSn(PO4)3.

[0283] Fast ion conductors with NASICON structures are materials with ultrafast ion conduction capabilities, rich three-dimensional lithium ion diffusion and transmission channels, and have the advantages of high ion conduction efficiency and strong structural stability during multiple lithium removal and insertion processes. Coating fast ion conductors with NASICON structures on the surface of phosphate particles can significantly increase the transmission rate of lithium ions during multiple lithium removal / insertion at the positive terminal, improve the ionic conductivity of the positive electrode active material, and improve the fast charging capability of the battery cell. In addition, it can also increase the gram capacity and the energy density of the corresponding battery cell.

[0284] In some embodiments, the coating layer further includes carbon.

[0285] The carbon element and the fast ion conductor can be arranged in layers, for example, the carbon element is used as an independent carbon coating layer, and the fast ion conductor is used as an independent fast ion conductor layer. The carbon coating layer can be coated on the surface of the phosphate particles, and the fast ion conductor layer is located on the surface of the carbon coating layer, that is, the fast ion conductor layer is located on the side of the carbon coating layer away from the phosphate particles. Alternatively, the fast ion conductor layer can be coated on the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, that is, the carbon coating layer is located on the side of the fast ion conductor layer away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0286] Optionally, the carbon coating layer can be coated on the surface of the fast ion conductor layer by a carbonization process of an organic carbon source (e.g., glucose, polyethylene glycol, etc.). The carbon coating layer can partially coat the fast ion conductor layer, or it can completely coat the fast ion conductor layer. The provision of the carbon coating layer can significantly improve the electronic conductivity of the phosphate particles, make up for the defect of poor electronic conductivity of the phosphate particles, and improve the energy density of the battery cell. Specifically, the provision of the carbon coating layer enables the positive electrode active material of the present application to have the following advantages: The carbon coating layer in the positive electrode active material of the present application provides a suitable channel for the transmission of electrons, which can significantly improve the conduction rate of electrons in multiple lithium de- and lithium insertion processes, improve the electronic conductivity of lithium-containing phosphates, improve the charging capacity of the corresponding battery cells, and also improve the energy density.

[0287] The carbon coating layer of the positive electrode active material of the present application is loose and porous, which enables the electrolyte to be in full and effective contact with the lithium-containing phosphate, thereby increasing the transmission rate of lithium ions at the interface and improving the charging capacity of the battery cell.

[0288] Coating a carbon coating on the surface of the lithium-containing phosphate can not only improve the conductivity of the lithium-containing phosphate, but also improve the structural stability of the positive electrode active material, effectively alleviate the iron dissolution of the positive electrode active material during long-term storage and cyclic use of the battery cell, thereby improving the cycle life of the battery cell. The positive electrode active material of the present application is based on lithium-containing phosphate, giving full play to the advantages of low cost, high use reliability, and good cycle stability of lithium-containing phosphate. At the same time, the coating layer (fast ion conductor layer and carbon coating layer) is used to solve the disadvantages of poor electronic conductivity and ion conductivity. The battery monomer prepared from the positive electrode active material of the present application can improve the energy density of the battery monomer on the premise of excellent cycle performance. In the embodiments of the present application, the content of elements in the positive electrode active material has the meaning well-known in the art and can be detected by equipment and methods well-known in the art. For example, referring to EPA 6010D-2014, it is tested by inductively coupled plasma atomic emission spectrometry and determined by inductively coupled plasma optical emission spectrometry (ICP-OES, instrument model: Thermo ICAP7400). After the battery monomer is discharged to 0% state of charge (SOC) and the positive electrode plate is disassembled, it is cleaned with DMC and dried, and then after high-temperature calcination to remove impurities, 0.4 g of the positive electrode active material is weighed, and 10 ml (50% concentration) of aqua regia is added thereto. Then it is placed on a flat plate at 180 °C for 30 min. After digestion on the flat plate, it is fixed to a volume of 100 mL, and quantitative testing is carried out by the standard curve method.

[0289] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32, and can be optionally 0.19 to 0.26. Exemplarily, the graphitization degree of the positive electrode active material is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32 or a range composed of any two of the above values.

[0290] When the graphitization degree of the positive electrode active material is within the above range, it is beneficial to improve the conductivity of the positive electrode active material, reduce the heat generation of the positive electrode plate, and thus reduce the heat generation of the battery monomer.

[0291] In the embodiments of the present application, the higher the graphitization degree of the material, the lower the degree of disorder, and it can be tested according to the general rules of X-ray diffraction analysis method of JIS / K 0131-1996.

[0292] In some embodiments, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1% to 2%, and the specific surface area of the lithium-containing phosphate with olivine structure is 5m 2 / g to 18m 2 / g.

[0293] Optionally, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1% to 2%, and the specific surface area of the lithium-containing phosphate with olivine structure is 7.5m 2 / g to 14m2 / g.

[0294] Exemplarily, the mass content of carbon element in the lithium-containing phosphate with olivine structure is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or the range composed of any two of the above values.

[0295] Exemplarily, the specific surface area of the lithium-containing phosphate with olivine structure is 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, 8 m 2 / g, 9 m 2 / g, 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g, 15 m 2 / g, 16 m 2 / g, 17 m 2 / g, 18 m 2 / g or the range composed of any two of the above values.

[0296] The carbon element mainly exists in the coating layer in the form of a carbon coating layer. The carbon coating layer is loose and porous, which is beneficial to improving the specific surface area of the material, more beneficial to the effective contact between the electrolyte and the phosphate particles, and beneficial to the transmission of lithium ions at the phase interface. In addition, when the mass content of the carbon element is within the above range, the conductivity of the lithium-containing phosphate with olivine structure can be significantly improved, which is beneficial to enhancing the ionic conductivity and electronic conductivity of the lithium-containing phosphate with olivine structure, and can improve the rapid charging ability and energy density of the battery monomer.

[0297] In the embodiments of the present application, the specific surface area of the material has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, it is detected according to the test standard GB / T 19587-2017. The positive electrode active material is used as a sample, and the specific surface area is tested by a Tri-Star 3020 specific surface area and pore size analyzer of Micromeritics Company, USA.

[0298] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies: 1 µm ≤ Dv50 ≤ 2 µm, 0.4 µm ≤ Dv10 ≤ 0.7 µm.

[0299] Exemplarily, the Dv50 of the positive electrode active material may be 1 µm, 1.1 µm, 1.15 µm, 1.2 µm, 1.25 µm, 1.3 µm, 1.35 µm, 1.4 µm, 1.45 µm, 1.5 µm, 1.55 µm, 1.6 µm, 1.65 µm, 1.7 µm, 1.75 µm, 1.8 µm, 1.85 µm, 1.9 µm, 1.95 µm, 2 µm, or a range composed of any two of the above values.

[0300] Exemplarily, the Dv10 of the positive electrode active material may be 0.4 µm, 0.45 µm, 0.5 µm, 0.55 µm, 0.6 µm, 0.65 µm, 0.7 µm, or a range composed of any two of the above values.

[0301] The particle size of the positive electrode active material is relatively small, the lithium deintercalation / insertion path of lithium ions in the positive electrode active material is short, and the heat generation is less. Moreover, the particle size of the above positive electrode active material is not too small, and basically no agglomeration occurs during the processing and preparation process, making the performance of the positive electrode active material stable.

[0302] In the embodiments of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution, and the volume average particle size Dv10 of the material refers to the particle size corresponding to 10% in the volume distribution. It can be detected by using equipment and methods well-known in the art. For example, taking the positive electrode active material as a sample, according to the test standard GB / T 19077-2016, the Dv50 and Dv10 of the particles are tested by a Mastersizer 2000E laser particle size analyzer, etc.

[0303] When the positive electrode active material includes other materials in addition to the lithium-containing phosphate with an olivine structure, the volume distribution particle size of the positive electrode active material refers to the volume distribution particle size of all positive electrode active materials.

[0304] In some embodiments, the lithium-containing phosphate with an olivine structure is in a granular shape. The lithium-containing phosphate with an olivine structure includes secondary particles, and the secondary particles include a plurality of primary particles. The average particle size of the primary particles is 200 nm to 500 nm. Exemplarily, the average particle size of the primary particles is 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, 500 nm, or a range composed of any two of the above values.

[0305] The average particle size of the primary particles is relatively small, the lithium deintercalation / insertion path of lithium ions in the positive electrode active material is short, and the heat generation is less.

[0306] In the embodiments of the present application, secondary particles refer to aggregated particles formed by the aggregation of two or more primary particles. The primary particles and secondary particles can be easily distinguished by experimental means (such as taking SEM images using a scanning electron microscope), and the average particle size of the primary particles can be obtained by testing in the SEM images of the scanning electron microscope. The SEM test parameters can be set as follows: the working voltage (EHT) is 10.00 kV, the InLens detector is used, the working distance is 4.6 mm, and the magnification is 1000X.

[0307] In some embodiments, the positive electrode film layer further includes one or more of ternary materials, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrate. The above materials can be used as a lithium supplement agent, which can supplement lithium ions to the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0308] Optionally, the ternary material includes Li x3 A y3 Ni a3 Co b3 Mn c M3 (1-a3-b3-c3) Y3 z3 , where 0 < x3 ≤ 2.1, 0 < y3 ≤ 2.1, and 0.9 ≤ x3 + y3 ≤ 2.1, 0 ≤ a3 ≤ 1, 0 ≤ b3 ≤ 1, 0 ≤ c3 ≤ 1, and 0.1 ≤ a3 + b3 + c3 ≤ 1, 1.8 ≤ z3 ≤ 3.5, A includes one or several of Na, K, and Mg, M3 includes one or several of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, and Y3 includes one or several of O and F.

[0309] Exemplarily, the ternary material includes LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.80 Co0.15 Al 0.05 At least one of O2.

[0310] In some embodiments, the mass content of the lithium supplement agent in the positive electrode film layer is 0.5% to 5%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or the range composed of any two of the above values. When the mass content of the lithium supplement agent is within the above range, it can supplement lithium ions for the positive electrode film layer, make up for the irreversible lithium ion loss in the system, improve the capacity, and thus improve the energy density of the battery cell.

[0311] The lithium supplement agent can be in the same layer as the positive electrode active material or in different layers. When the lithium supplement agent and the positive electrode active material are in different layers, the lithium supplement agent can be in the lithium supplement layer, and the positive electrode active material can be in the positive electrode active material layer. In other words, the positive electrode film layer includes a lithium supplement layer and a positive electrode active material layer. The positive electrode active material layer can be disposed on at least one side of the positive electrode current collector, and the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector. Or, the lithium supplement layer can be disposed on at least one side of the positive electrode current collector, and the positive electrode active material layer can be located between the lithium supplement layer and the positive electrode current collector. Optionally, the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector. During the charge and discharge cycle of the battery cell, the lithium supplement agent in the lithium supplement layer can be gradually released into the system to make up for the lithium loss in the battery system.

[0312] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The embodiments of the present application do not particularly limit the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode conductive agent is ≤5%.

[0313] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The embodiments of the present application do not particularly limit the type of the positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0314] In some embodiments, the positive current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy foils may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0315] In some embodiments, the ratio of the thickness of the positive current collector to the thickness of the single-sided positive electrode film layer is from 0.05 to 0.3. Exemplarily, the ratio of the thickness of the positive current collector to the thickness of the single-sided positive electrode film layer is 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3 or a range composed of any two of the above values.

[0316] When the ratio of the thickness of the positive current collector to the thickness of the single-sided positive electrode film layer is within the above range, the fast charging ability and energy density of the battery cell can be improved.

[0317] In some embodiments, the thickness of the positive current collector is from 10 μm to 20 μm, from 10 μm to 15 μm, and may be optionally 12 μm to 15 μm. Exemplarily, the thickness of the positive current collector is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 20 μm or a range composed of any two of the above values.

[0318] When the thickness of the positive current collector is within the above range, the current-carrying capacity of the positive current collector is relatively excellent, and the battery cell can have a high energy density.

[0319] In the embodiments of the present application, the thicknesses of the positive electrode film layer and the positive current collector have meanings well-known in the art, and can be detected by devices and methods well-known in the art. For example, the thickness of the positive electrode plate is measured with a micrometer, the film layer on the surface of the positive current collector is removed, and the thickness of the positive current collector is measured with a micrometer. When the positive electrode film layer is coated on one side, the thickness of the positive electrode film layer is the thickness of the positive electrode plate minus the thickness of the positive current collector. When the positive electrode film layer is coated on both sides, the thickness of the positive electrode film layer is (the thickness of the positive electrode plate minus the thickness of the positive current collector) / 2.

[0320] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector and then drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0321] The positive electrode sheet does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the embodiment of the present application further includes a positive electrode conductive layer disposed on the surface of the positive electrode current collector and sandwiched between the positive electrode current collector and the positive electrode film layer. In some other embodiments, the positive electrode sheet of the embodiment of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0322] In some embodiments, the positive electrode sheet further includes a positive electrode conductive layer, and the positive electrode conductive layer is located between the positive electrode film layer and the positive electrode current collector. The positive electrode conductive layer can further improve the conductivity of the positive electrode sheet, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the battery cell.

[0323] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. Exemplarily, the thickness of the positive electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm or a range composed of any two of the above values.

[0324] When the thickness of the positive electrode conductive layer is within the above range, it can further improve the conductivity of the positive electrode sheet, reduce the heat generation of the positive electrode sheet, and thus reduce the heat generation of the battery cell, and can also take into account the improvement of the energy density of the battery cell.

[0325] In the embodiment of the present application, the thickness of the positive electrode conductive layer has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, tomographic scanning is performed on the positive electrode sheet to directly measure the thickness of the positive electrode conductive layer.

[0326] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0327] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. Exemplarily, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50% or a range composed of any two of the above values.

[0328] Exemplarily, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The positive electrode conductive agent in the positive electrode conductive layer can improve the conductivity of the positive electrode conductive layer, thereby improving the conductivity of the positive electrode sheet and reducing the heat generation of the battery cell.

[0329] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%. Exemplarily, 50%, 60%, 65%, 70% or a range composed of any two of the above values.

[0330] Exemplarily, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and fluorinated acrylate resins. The positive electrode binder in the positive electrode conductive layer can improve the bonding performance between the positive electrode current collector part and the positive electrode film layer, and improve the structural stability of the positive electrode sheet.

[0331] [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector part and a negative electrode film layer provided on at least one surface of the negative electrode current collector part and including a negative electrode active material. For example, the negative electrode current collector part has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector part.

[0332] In some embodiments, when the battery cell is in a 100% charged state, the tap density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 ; it can be optionally 1.25 g / cm 3 to 1.36 g / cm 3 . Exemplarily, when the battery cell is in a 100% charged state, the tap density of the negative electrode film layer is 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.22 g / cm 3 , 1.25 g / cm 3 , 1.28 g / cm 3 , 1.3 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm 3 , 1.36 g / cm 3 or a range composed of any two of the above values.

[0333] When the tap density of the negative electrode film layer is within the above range, it is beneficial to improve the energy density of the battery cell; and since the negative electrode active materials in the negative electrode film layer are stacked relatively tightly and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0334] In the embodiments of the present application, the compaction density of the negative electrode film layer in the 100% charged state has the meaning well-known in the art, and can be detected by the equipment and methods well-known in the art. The detection method is the same as the compaction density test method of the positive electrode film layer described above.

[0335] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 to 170 mg / 1540.25 mm 2 , and may be optionally 110 mg / 1540.25 mm 2 to 150 mg / 1540.25 mm 2 . Exemplarily, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 , 92 mg / 1540.25 mm 2 , 95 mg / 1540.25 mm 2 , 96 mg / 1540.25 mm 2 , 100 mg / 1540.25 mm 2 , 102 mg / 1540.25 mm 2 , 104 mg / 1540.25 mm 2 , 105 mg / 1540.25 mm 2 , 108 mg / 1540.25 mm 2 , 110 mg / 1540.25 mm 2 , 112 mg / 1540.25 mm 2 , 114 mg / 1540.25 mm 2 , 115 mg / 1540.25 mm 2 , 116 mg / 1540.25 mm 2 , 118 mg / 1540.25 mm 2 , 120 mg / 1540.25 mm 2 , 122 mg / 1540.25 mm 2 , 125 mg / 1540.25 mm 2 , 128 mg / 1540.25 mm 2 , 130 mg / 1540.25 mm 2 , 132 mg / 1540.25 mm 2 , 135 mg / 1540.25 mm 2 , 137 mg / 1540.25 mm 2 , 140 mg / 1540.25 mm 2 , 142 mg / 1540.25 mm 2, 145 mg / 1540.25 mm 2 , 148 mg / 1540.25 mm 2 , 150 mg / 1540.25 mm 2 , 152 mg / 1540.25 mm 2 , 155 mg / 1540.25 mm 2 , 160 mg / 1540.25 mm 2 , 165 mg / 1540.25 mm 2 , 170 mg / 1540.25 mm 2 Or a range composed of any two of the above values.

[0336] When the single-sided coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode sheet will not be excessive, and it can take into account the improvement of the energy density of the battery cell.

[0337] In the embodiments of the present application, the single-sided coating weight of the negative electrode film layer has the meaning well-known in the art, and can be detected by the equipment and methods well-known in the art. The detection method is as described in the single-sided coating weight test method of the film layer above.

[0338] In some embodiments, the powder resistivity of the negative electrode active material is from 0.005 Ω·cm to 0.043 Ω·cm, and can be 0.04 Ω·cm. Exemplarily, the powder resistivity of the negative electrode active material can be 0.043 Ω·cm, 0.04 Ω·cm, 0.035 Ω·cm, 0.03 Ω·cm, 0.025 Ω·cm, 0.02 Ω·cm, 0.015 Ω·cm, 0.01 Ω·cm, 0.005 Ω·cm or a range composed of any two of the above values.

[0339] The relatively low powder resistivity of the negative electrode active material results in a relatively low resistance of the negative electrode sheet and less heat generation of the battery cell.

[0340] In the embodiments of the present application, the powder resistivity of the negative electrode active material has the meaning well-known in the art, and can be detected by the equipment and methods well-known in the art. The detection method is as described in the powder resistivity test method of the positive electrode active material above.

[0341] In some embodiments, the powder compaction density of the negative electrode active material under a pressure of 20000 N is 1.5 g / cm 3 to 1.85 g / cm 3 , and can be 1.55 g / cm 3 to 1.65 g / cm 3 . Exemplarily, the powder compaction density of the negative electrode active material under a pressure of 20000 N is 1.5 g / cm 3, 1.55 g / cm 3 , 1.6 g / cm 3 , 1.65 g / cm 3 , 1.7 g / cm 3 , 1.75 g / cm 3 , 1.8 g / cm 3 , 1.85 g / cm 3 or a range composed of any two of the above values.

[0342] When the powder compaction density of the negative electrode active material is within the above range under 20000 N, the energy density of the battery cell can be improved. Moreover, since the negative electrode active material in the negative electrode film layer can be stacked more closely and the contact resistance between particles is small, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0343] In the embodiments of the present application, the powder compaction density of the material has the meaning well-known in the art and can be detected by methods and equipment well-known in the art, and is detected according to the test standard GB / T24533-2009. As an example, a certain amount of negative electrode active material is taken as a sample and added to a mold with a bottom area of 1.327 cm 2 in a UTM7305 type electronic pressure testing machine, pressurized to 2000 kg (equivalent to 20000 N), kept under pressure for 30 s, then the pressure is released, kept for 10 s, and then the powder compaction density of the negative electrode active material under the action of 20000 N is recorded and calculated.

[0344] In some embodiments, the charging specific capacity of the negative electrode active material at a 0.1C rate is 350 mAh / g to 480 mAh / g. Exemplarily, the charging specific capacity of the negative electrode active material at a 0.1C rate is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g or a range composed of any two of the above values.

[0345] When the charging specific capacity of the negative electrode active material at a 0.1C rate is within the above range, the energy density of the battery cell is relatively high.

[0346] In the embodiments of the present application, the charging gram capacity of the negative electrode active material at a rate of 0.1C is a meaning well-known in the art, and can be detected by devices and methods well-known in the art. The detection method is the same as the charging gram capacity test method of the positive electrode active material at a rate of 0.1C described above.

[0347] In some embodiments, the negative electrode active material includes a carbon-based material. The carbon-based material has high cycle stability and can improve the cycle performance of the battery cell. Optionally, the mass ratio of the carbon-based material in the negative electrode active material can be greater than or equal to 80% and less than or equal to 100%.

[0348] The positive electrode active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative electrode active material is mainly a carbon-based material system. When used in combination, the battery cell has excellent cycle performance.

[0349] Optionally, the carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. Exemplarily, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5% or a range composed of any two of the above values.

[0350] When the graphitization degree of the graphite particles is within the above range, the graphite particles have excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet and the battery cell, and can improve the fast charging performance of the battery cell.

[0351] In some embodiments, the graphite particles include artificial graphite and a carbon coating layer. The artificial graphite includes secondary particles, and the secondary particles include a plurality of primary particles. The carbon coating layer covers the surface of the artificial graphite. The carbon in the carbon coating layer is mainly amorphous carbon. Amorphous carbon refers to a transitional carbon material with a very low degree of graphitization crystallization and an approximate amorphous form (or no fixed shape and periodic structural rules). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0352] The artificial graphite includes secondary particles. The migration path of lithium ions in the artificial graphite is more, and the migration path in the primary particles is shorter, which can improve the migration rate of lithium ions. The carbon coating layer has more end faces and defects, so that the number of sites capable of intercalating and deintercalating lithium ions is more, and the electrical conductivity of the carbon coating layer is excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0353] Optionally, based on the mass of the graphite particles, the mass content of the carbon coating layer is 2% to 5%. Exemplarily, the mass content of the carbon coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range composed of any two of the above values.

[0354] When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode sheet can be further reduced, and the heat generation of the battery cell can be reduced.

[0355] In the embodiments of the present application, the graphite particles can be prepared by methods well known in the art. For example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and after carbonization treatment, a carbon coating layer is formed on at least part of the surface of the artificial graphite particles.

[0356] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of coal tar pitch and petroleum pitch is below 250 °C.

[0357] Optionally, the carbonization treatment temperature is 700 °C to 1800 °C. Optionally, the carbonization treatment temperature is 1000 °C to 1300 °C. When the carbonization treatment temperature is within a suitable range, the organic carbon source can be carbonized, and a coating layer containing amorphous carbon is formed on at least a part of the surface of the artificial graphite.

[0358] Optionally, the carbonization treatment time is 1 h to 6 h.

[0359] In some embodiments, the carbon-based material may further include natural graphite. Specifically, the carbon-based material may include graphite particles, or the carbon-based material may include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0360] In some embodiments, the negative electrode active material may further include a silicon-based material. The introduction of the silicon-based material can increase the capacity of the negative electrode active material and improve the energy density of the battery cell.

[0361] Optionally, based on the mass of the negative electrode active material, the mass content of silicon element in the silicon-based material is 0.3% to 10.0%, and may be selected as 1% to 6%. Exemplarily, the mass content of silicon element in the silicon-based material is 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10% or any range composed of any two of the above values.

[0362] When the mass content of silicon element in the silicon-based material is within the above range, the capacity of the negative electrode active material can be increased, and the energy density of the battery cell can be improved.

[0363] Optionally, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0364] In some embodiments, in addition to the above-mentioned carbon-based material and optional silicon-based material, the negative electrode active material may further include at least one of a tin-based material and lithium titanate. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

[0365] In this application, the qualitative and quantitative determination of each substance or element can be detected by suitable equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc. And those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0366] For example, this application can combine the general rules of X-ray diffraction analysis method of JIS / K0131-1996 to perform X-ray powder diffraction test and qualitative analysis on the negative electrode sheet or the negative electrode active material.

[0367] Artificial graphite and natural graphite can be distinguished by the SEM cross-sectional view taken by scanning electron microscope (SEM). There are voids between the flake structures in the SEM cross-sectional view of natural graphite, and the SEM cross-sectional view of artificial graphite is dense and has no obvious gaps, or can be distinguished by the XRD spectrum obtained by X-ray diffraction method. There are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, and only 2H phase exists in the XRD spectrum of artificial graphite.

[0368] In the embodiments of this application, the negative electrode film layer includes at least one layer of film layer, and a single-layer film layer can be adopted, or at least two layers of film layers can be adopted. Optionally, the negative electrode film layer includes at least two layers of film layers.

[0369] When the negative electrode film layer adopts a single-layer film layer, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally also includes a silicon-based material. When a single-layer film layer is adopted, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm to 13.5 μm. Exemplarily, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm or the range composed of any two of the above values.

[0370] When the negative electrode film layer adopts at least two layers of film layers, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally also includes a silicon-based material. The silicon-based material can be located in one of the at least two layers of film layers, or can be located in at least two of the at least two layers of film layers. The negative electrode film layer can include two layers of film layers, three layers of film layers, four layers of film layers, or even more layers of film layers.

[0371] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is disposed on the surface of the negative electrode current collector. The carbon-based material in the first negative electrode film layer includes graphite particles. The second negative electrode film layer is connected to the side of the first negative electrode film layer facing away from the negative electrode current collector. The carbon-based material in the second negative electrode film layer includes graphite particles. The graphite particles in the first negative electrode film layer and the graphite particles in the second negative electrode film layer can be the same or different.

[0372] The interface between the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and is optionally irregular.

[0373] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0374] The negative electrode film layer includes at least two layers of film layers, and layer-by-layer coating is beneficial to improving the fast charging performance of the battery cell. Especially when there are differences between the first negative electrode film layer and the second negative electrode film layer, it is possible to construct pore differences in the negative electrode film layer, reduce the tortuosity of lithium ion transport, and improve the fast charging performance of the battery cell.

[0375] Optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer. Further optionally, the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is greater than the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer, which is beneficial to improving the compaction density of the negative electrode film layer. When the negative electrode active material includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer.

[0376] There are differences in the particle sizes in the first negative electrode film layer and the second negative electrode film layer, which can improve the fast charging performance of the battery cell. Specifically, during fast charging, the overpotential of the second negative electrode film layer is usually higher, and the bottleneck of fast charging lies mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transport path of lithium ions, improve the fast charging performance, and can improve the problem of lithium deposition on the surface layer of the negative electrode plate.

[0377] Optionally, the negative electrode active material in the first negative electrode film layer is granular, and its volume average particle size Dv50 is from 9.5 μm to 18.5 μm, optionally from 9.5 μm to 14.6 μm. Exemplarily, the volume average particle size of the negative electrode active material in the first negative electrode film layer is 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 14.6 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm, 18.5 μm or a range composed of any two of the above values. When the first negative electrode film layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer is from 9.5 μm to 18.5 μm, optionally from 9.5 μm to 14.6 μm.

[0378] When the volume average particle size Dv50 of the negative electrode active material in the first negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material.

[0379] Optionally, the negative electrode active material in the second negative electrode film layer is granular, and its volume average particle size Dv50 is from 7.8 μm to 14.3 μm, optionally from 7.8 μm to 11.3 μm. Exemplarily, the volume average particle size Dv50 of the negative electrode active material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm or a range composed of any two of the above values. When the second negative electrode film layer includes graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative electrode film layer is from 7.8 μm to 14.3 μm, optionally from 7.8 μm to 11.3 μm.

[0380] When the volume average particle size Dv50 of the negative electrode active material in the second negative electrode film layer is within the above range, on the one hand, it can shorten the solid-phase transmission path of lithium ions and improve the fast charging performance. On the other hand, the material is not prone to agglomeration during the preparation process, which can improve the stability of the material. On the other hand, the cooperation of the negative electrode active material in the second negative electrode film layer with the volume average particle size range and the negative electrode active material in the first negative electrode film layer is beneficial to constructing the gradient pore difference between the second negative electrode film layer and the first negative electrode film layer, reducing the tortuosity of lithium ion transmission, and improving the fast charging performance of the battery cell.

[0381] In the embodiments of the present application, the volume average particle size Dv50 of the negative electrode active material has the meaning well known in the art and can be detected by using the equipment and methods well known in the art. The detection method is the same as the volume average particle size Dv50 test method of the positive electrode active material described above.

[0382] Optionally, the tapped density of the carbon-based material in the first negative electrode film layer is less than or equal to the tapped density of the carbon-based material in the second negative electrode film layer. The tapped density can reflect the packing density of the active material in the film layer. When the tapped density of the carbon-based material in the second negative electrode film layer is greater than that in the first negative electrode film layer, the second negative electrode film layer is more densely packed, which improves the energy density of the battery cell. The first negative electrode film layer is relatively sparsely packed with more pores, which can improve the fast charging performance of the battery cell. When the negative electrode active material includes graphite particles, the tapped density of the graphite particles in the first negative electrode film layer is less than or equal to the tapped density of the graphite particles in the second negative electrode film layer.

[0383] Optionally, the tapped density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21 g / cm 3 , such as 0.82 g / cm 3 , 0.85 g / cm 3 , 0.88 g / cm 3 , 0.90 g / cm 3 , 0.92 g / cm 3 , 0.95 g / cm 3 , 0.98 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.08 g / cm 3 , 1.10 g / cm 3 , 1.12 g / cm 3 , 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.21 g / cm 3 or the range composed of any two of the above values. When the tapped density of the carbon-based material in the first negative electrode film layer is within a suitable range, the fast charging performance of the battery cell can be improved.

[0384] Optionally, the tapped density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 to 1.25 g / cm 3 , such as 0.90 g / cm 3 , 0.92 g / cm 3, 0.95 g / cm 3 , 0.98 g / cm 3 , 1.00 g / cm 3 , 1.05 g / cm 3 , 1.08 g / cm 3 , 1.10 g / cm 3 , 1.12 g / cm 3 , 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.21 g / cm 3 , 1.22 g / cm 3 , 1.23 g / cm 3 , 1.24 g / cm 3 , 1.25 g / cm 3 or a range composed of any two of the above values. When the tapped density of the carbon-based material in the second negative electrode film layer is within a suitable range, the energy density of the battery cell can be improved.

[0385] In the embodiments of the present application, the tapped density of the material has the meaning well known in the art and can be measured by instruments and methods known in the art. For example, reference can be made to GB / T5162-2006, and a powder tapped density tester can be used for measurement. The test instrument can be BT-301 produced by Dandong BETTER.

[0386] Optionally, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7 to 7:3, and can be optionally 4:6 to 6:4. Exemplarily, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7, 4:6, 5:5, 6:4, 7:3 or a range composed of any two of the above values. By adjusting the thickness ratio of the first negative electrode film layer and the second negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium ion transmission can be reduced, and the fast charging ability of the battery cell can be improved.

[0387] In some embodiments, after the battery cell undergoes 10 full charge test cycles at the beginning of life (BOL), the thickness of the first negative electrode film layer is 15 μm to 65 μm, such as 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm or a range composed of any two of the above values. When the thickness of the first negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be increased, the tortuosity of lithium ion transmission can be reduced, and the fast charging ability of the battery cell can be improved.

[0388] In some embodiments, after the battery cell undergoes 10 full charge test cycles at the beginning of life (BOL), the thickness of the second negative electrode film layer is 15 μm to 65 μm, such as 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 57 μm, 58 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm or a range composed of any two of the above values. When the thickness of the second negative electrode film layer is within the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be regulated and increased, the tortuosity of lithium ion transport can be reduced, and the fast charging ability of the battery cell can be improved.

[0389] In the embodiments of the present application, for example, taking the battery charging upper limit voltage of 3.65 V and the battery discharge cut-off voltage of 2.0 V as an example for illustration, The specific steps of the BOL full charge test are as follows: At 25 °C, charge at a charging rate of 0.33 C of the battery nominal capacity to 3.65 V, then charge at a constant voltage of 3.65 V to 0.05 C, stand for 10 min, then discharge at a discharge rate of 0.33 C to 2.0 V, stand for 10 min. The above one charge and discharge is one cycle, and cycle 10 times. Then charge at a charging rate of 0.33 C of the nominal capacity to 3.65 V, and then charge at a constant voltage of 3.65 V to 0.05 C to obtain the BOL full charge state. In the BOL full charge state, disassemble the negative electrode plate, use a tomography scanning electron microscope to observe the cross-section in the thickness direction of the middle area of the negative electrode plate, distinguish the regions of the two according to the interface between the first negative electrode film layer and the second negative electrode film layer, measure the thicknesses of the two respectively. For example, measure the thicknesses of 10 positions of the first negative electrode film layer, calculate their average value as the average value of the first negative electrode film layer, measure the thicknesses of 10 positions of the second negative electrode film layer, and calculate their average value as the average value of the second negative electrode film layer.

[0390] In some embodiments, after the full charge test at the end of life (EOL) of the battery cell, the thickness of the first negative electrode film layer is 15 μm to 70 μm, such as 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm or a range composed of any two of the above values. When the thickness of the first negative electrode film layer is within the above range, the first negative electrode film layer and the second negative electrode film layer can regulate and increase the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transport, and improve the fast charging ability of the battery cell.

[0391] In some embodiments, after the full charge test at the end of life (EOL) of the battery cell, the thickness of the second negative electrode film layer is 15 μm to 70 μm, such as 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 35 μm, 40 μm, 43 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm or a range composed of any two of the above values. When the thickness of the second negative electrode film layer is within the above range, the first negative electrode film layer and the second negative electrode film layer can regulate and increase the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transport, and improve the fast charging ability of the battery cell.

[0392] In the embodiments of the present application, for example, taking the upper limit voltage of battery charging as 3.65 V and the cut-off voltage of battery discharging as 2.0 V as an example for illustration, The specific steps for the EOL full charge test are as follows: At 60 °C, charge at a charging rate of 0.33C of the battery nominal capacity until 3.65V, then perform constant voltage charging at 3.65V until 0.05C, let it stand for 10 minutes, then discharge at a discharge rate of 0.33C until 2.0V, and let it stand for 10 minutes. The above one charge and discharge cycle is repeated until the battery capacity decays to 80% of the nominal capacity and the test stops. Then, at 25 °C, charge at a constant current of 0.33C until 3.65V, and perform constant voltage charging at a rate of 0.05C until 3.65V, which is the EOL full charge state. In the EOL full charge state, disassemble the negative electrode sheet, use a tomography scanning electron microscope to observe the cross-section in the thickness direction of the middle area of the negative electrode sheet, distinguish the regions of the first negative electrode film layer and the second negative electrode film layer according to the interface between them, and measure their thicknesses respectively. For example, measure the thicknesses at 10 positions of the first negative electrode film layer, calculate their average value as the average value of the first negative electrode film layer, measure the thicknesses at 10 positions of the second negative electrode film layer, and calculate their average value as the average value of the second negative electrode film layer.

[0393] In some embodiments, when the negative electrode film layer adopts a single-layer film layer (different from the above double-layer film layer), the negative electrode film layer further includes a lithium-containing binder. Optionally, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range composed of any two of the above values. The lithium element in the lithium-containing binder can exist in an ionic form, which can increase the number of free-moving lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the insertion and extraction rate of lithium ions, and improve the fast charging performance of the battery cell. Optionally, the negative electrode film layer can further include a negative electrode binder. For example, the negative electrode binder includes at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0394] Optionally, the mass content of lithium element in the lithium-containing binder is 3% to 10%. Exemplarily, the mass content of lithium element in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of the above values. The mass content of lithium element is calculated based on the mass of the lithium-containing binder. When the mass content of lithium element is within the above range, it can make the number of free-moving lithium ions in the negative electrode film layer relatively large, further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the insertion and extraction rate of lithium ions, and improve the fast charging performance of the battery cell.

[0395] Exemplarily, the lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer. The molar ratio of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of the lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0396] The lithium-containing binder of the above materials can provide a certain amount of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during the charge and discharge process, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during the fast charge and discharge process.

[0397] In some other embodiments, when the negative electrode film layer adopts at least two layers of film layers, the negative electrode film layer further includes a lithium-containing binder.

[0398] Optionally, the first negative electrode film layer further includes a first lithium-containing binder, and the second negative electrode film layer further includes a second lithium-containing binder. The mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than or equal to the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer. Further optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0399] The mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the number of freely movable lithium ions provided by the second lithium-containing binder for the second negative electrode film layer is relatively more, which can further improve the fast charging performance of the battery cell.

[0400] Optionally, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range composed of any two of the above values. The lithium element in the first lithium-containing binder can exist in the form of ions, which can increase the number of freely movable lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0401] Optionally, the mass content of lithium element in the first lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. Exemplarily, the mass content of lithium element in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range composed of any two of the above values. When the mass content of lithium element is within the above range, the number of free-moving lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0402] Exemplarily, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, and the lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer and a 2-hydroxyethyl acrylate monomer, and the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer and the 2-hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer and the 2-hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0403] The lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during the charge and discharge process, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during the fast charge and discharge process.

[0404] Optionally, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1% to 1%. Exemplarily, the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or the range composed of any two of the above values. The lithium element in the second lithium-containing binder can exist in the form of ions, which can increase the number of free-moving lithium ions in the negative electrode film layer, shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0405] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0406] Optionally, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, and can be optionally 3% to 8%. Exemplarily, the mass content of lithium element in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or the range composed of any two of the above values. When the mass content of lithium element is within the above range, the number of free-moving lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, improve the intercalation and deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0407] Exemplarily, the second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer, and the lithium acrylate-acrylonitrile-acrylamide-2-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer, and the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and 2-hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0408] The lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the fast charging performance of the battery cell, and is not prone to swelling during the charge and discharge process, with a stable structure, so that the cycle performance of the negative electrode film layer is improved during the fast charge and discharge process.

[0409] In some embodiments, the first negative electrode film layer further includes a negative electrode binder, and the second negative electrode film layer further includes a negative electrode binder. The negative electrode binder in the first negative electrode film layer and the negative electrode binder in the second negative electrode film layer each independently include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS).

[0410] In some embodiments, the total content of the first lithium-containing binder and the negative electrode binder in the first negative electrode film layer is greater than the total content of the second lithium-containing binder and the negative electrode binder in the second negative electrode film layer, and the mass content of the first lithium-containing binder relative to the mass of the first negative electrode film layer is less than the mass content of the second lithium-containing binder relative to the mass of the second negative electrode film layer.

[0411] In some embodiments, the negative electrode film layer may optionally further include a negative electrode conductive agent. There is no particular limitation on the type of the negative electrode conductive agent in the embodiments of the present application. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode conductive agent is ≤5%.

[0412] In some embodiments, the negative electrode film layer may optionally further include a negative electrode binder. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the negative electrode binder is ≤5%.

[0413] In some embodiments, the negative electrode film layer may optionally further include other additives. As an example, the other additives may include a thickening agent, a dispersing agent, etc. For example, sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, based on the total weight of the negative electrode film layer, the mass content of the other additives is ≤2%.

[0414] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0415] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 10 μm, and may be optionally 4 μm to 6 μm. Exemplarily, the thickness of the negative electrode current collector is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 10 μm or a range composed of any two of the above values.

[0416] When the thickness of the negative electrode current collector is within the above range, the current-carrying capacity of the negative electrode current collector is relatively excellent, and the battery cell can have a relatively high energy density.

[0417] In the embodiments of the present application, the thickness of the negative electrode current collector has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, the film layer on the surface of the negative electrode current collector is washed off with a solvent, and the thickness of the negative electrode current collector is measured with a micrometer.

[0418] The negative electrode film layer is usually formed by coating a negative electrode slurry on a negative electrode current collector part and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing negative electrode active materials, optional conductive agents, optionally binders, and other optional additives in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0419] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiment of the present application further includes a negative electrode conductive layer sandwiched between the negative electrode current collector part and the negative electrode film layer and disposed on the surface of the negative electrode current collector part. In some other embodiments, the negative electrode sheet of the embodiment of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0420] In some embodiments, the negative electrode sheet further includes a negative electrode conductive layer, and the negative electrode conductive layer is located between the negative electrode film layer and the negative electrode current collector part. The negative electrode conductive layer can further improve the conductivity of the negative electrode sheet, reduce the heat generation of the negative electrode sheet, and thus reduce the heat generation of the battery cell.

[0421] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. Exemplarily, the thickness of the negative electrode conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm or a range composed of any two of the above values.

[0422] When the thickness of the negative electrode conductive layer is within the above range, it can further improve the conductivity of the negative electrode sheet, reduce the heat generation of the negative electrode sheet, and thus reduce the heat generation of the battery cell, and can also take into account improving the energy density of the battery cell.

[0423] In the embodiment of the present application, the thickness of the negative electrode conductive layer has the meaning well known in the art, can be detected by equipment and methods well known in the art, and the testing method of the negative electrode conductive layer in the foregoing can be adopted.

[0424] In some embodiments, the negative electrode conductive layer includes one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode sheet and reducing the heat generation of the battery cell. The negative electrode binder in the negative electrode conductive layer can improve the bonding performance between the negative electrode current collector part and the negative electrode film layer and improve the structural stability of the negative electrode sheet.

[0425] In some embodiments, the negative electrode conductive layer may further optionally include other additives. As an example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0426] Optionally, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 20% to 40%. Exemplarily, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40% or a range composed of any two of the above values.

[0427] Exemplarily, the negative electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0428] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%. Exemplarily, 60%, 65%, 70%, 75%, 80% or a range composed of any two of the above values.

[0429] Exemplarily, the negative electrode binder includes one or more of styrene-butadiene rubber SBR, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0430] In some embodiments, the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is 1.05 to 1.30, and can be optionally 1.07 to 1.15. Exemplarily, the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is 1.05, 1.07, 1.1, 1.12, 1.15, 1.18, 1.2, 1.22, 1.25, 1.28, 1.3 or a range composed of any two of the above values.

[0431] When the ratio CB of the capacity of the negative electrode film layer per unit area to the capacity of the positive electrode film layer per unit area in the battery cell is within the above range, there are sufficient sites in the negative electrode film layer for lithium insertion, which can reduce the risk of lithium deposition and is beneficial for fast charging.

[0432] In the embodiments of the present application, the meaning of the CB value is well-known in the art, and it can be detected by using well-known equipment and methods in the art. For example, calculate the capacity of the negative electrode film layer per unit area and the capacity of the positive electrode film layer per unit area respectively, and then calculate the ratio of the two to obtain the CB value.

[0433] Specifically, taking the battery charging upper limit voltage of 3.65V and the battery discharging cut-off voltage of 2.0V as an example for illustration, The capacity of the positive electrode film layer per unit area refers to the actual de-lithiation capacity of the positive electrode active material. The test method is as follows: Disassemble the battery in a PRS340 / 11-119-11 Braun glove box, take the positive electrode plate, assemble it into a CR2430 type half-button battery of positive electrode-lithium sheet, and the area of the positive electrode plate used is amm 2, where the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio). Then, the assembled coin cell is left standing for 3 h, and the test is carried out at 25°C. First, charging (Charge) to deintercalate lithium is carried out at a rate of 0.1C in the voltage range of 2.0V to 3.65V, and then discharging (Discharge) to intercalate lithium is carried out at a rate of 0.05C to 2.0V. The cycle is repeated 2 times, and the discharge capacity of the second cycle is recorded as Y mAh. The actual length of the positive electrode tab of the battery design is b mm, the width is c mm, and the number of sides d on which the positive electrode active material is coated on the positive electrode current collector part, then the capacity of the positive electrode film layer per unit area = Y / a * b * c * d.

[0434] Specifically, the capacity of the negative electrode film layer per unit area refers to the actual lithium intercalation capacity of the negative electrode active material. The test method is as follows: The battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the negative electrode tab is taken, and a CR2430 type coin cell of negative electrode-lithium sheet is assembled. The area of the negative electrode tab used is f mm 2 , where the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio). Then, the assembled coin cell is left standing for 3 h, and the test is carried out at 25°C. First, discharging (Discharge) to intercalate lithium is carried out at a rate of 0.1C in the voltage range of 2V - 0V, and then charging (Discharge) to deintercalate lithium is carried out at a rate of 0.05C to 2V. The cycle is repeated 2 times, and the discharge capacity of the second cycle is recorded as Z mAh. The actual length of the negative electrode tab of the battery design is h mm, the width is i mm, and the number of sides d on which the negative electrode active material is coated on the negative electrode current collector part, then the lithium intercalation capacity of the negative electrode = Z / f * h * i * d.

[0435] [Separator membrane] In the embodiments of the present application, the separator membrane includes a base membrane with a porous structure.

[0436] In some embodiments, the base membrane includes at least one of glass fiber, non-woven fabric, and polyolefin. The base membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the base membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0437] Optionally, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0438] In some embodiments, the porosity of the base membrane is 20% to 70%, and can be optionally 35% to 60%. Exemplarily, the porosity of the base membrane is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or a range composed of any two of the above values.

[0439] When the porosity of the base film in the embodiments of the present application is within the above range, the migration ability of lithium ions in the separator can be improved, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0440] In the embodiments of the present application, the porosity refers to the percentage of the internal pore volume in the separator occupying the total volume of the separator. The porosity can be tested in accordance with the standard GB / T36363-2018 "Polyolefin Separator for Battery Cells". It should be noted that in the actual testing process, the testing process slightly different from the standard can be adopted according to the differences in testing instruments, testing errors, and in order to eliminate the testing influence on the porosity as much as possible, so as to obtain a more accurate test value.

[0441] In some embodiments, the thickness of the base film is 6 μm to 12 μm, and can be optionally 6 μm to 9 μm. Exemplarily, the thickness of the base film is 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm or the range composed of any two of the above values.

[0442] When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, the internal resistance of the battery cell can be further reduced, and thus the heat generation can be reduced.

[0443] In the embodiments of the present application, the separator can be a base film. Optionally, the separator further includes a functional layer disposed on at least one side of the base film. The functional layer can include inorganic particles to improve the heat resistance of the separator. Optionally, the functional layer is disposed on both sides of the base film.

[0444] In some embodiments, the functional layer includes a first functional layer and a second functional layer. The first functional layer is located on one side of the base film and includes first inorganic particles. The second functional layer is located on the other side of the base film and includes composite particles. The composite particles include second inorganic particles and a plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed inside the non-fluoropolymer particles.

[0445] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator.

[0446] Optionally, the first functional layer can include a binder, and can optionally include at least one of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0447] Optionally, the first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0448] In the embodiments of the present application, the meaning of the thickness of the base film is the meaning well-known in the art, and the meaning well-known in the art and equipment can be used for detection. For example, a newly prepared separator film can be taken as a sample, or a battery cell that has been discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, the separator film is obtained from the battery cell, and after drying the separator film, it is used as a sample. The separator film is cut by an ion beam cutter to form a cross-section. Subsequently, a scanning electron microscope is used to measure the thickness of the cross-section of the separator film and its respective layers.

[0449] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluoropolymer particles include acrylate copolymers. Optionally, the acrylate copolymers include acrylate-acrylonitrile-acrylamide-propylene copolymers. The acrylate copolymers have excellent adhesion properties and relatively high adhesion stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as a molar ratio of 35%:30%:15%:20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0450] The second inorganic particles in the composite particles make it difficult for the non-fluoropolymer particles to adhere to each other due to the high-temperature treatment during the granulation process, resulting in pores in the composite particles, which is beneficial to the transmission of lithium ions, improves the ionic conductivity of the separator film, and the second inorganic particles can also increase the compression modulus of the composite particles. During the charge and discharge process, the composite particles are not easily deformed, making the structure of the separator film more stable, which can improve the kinetic performance of the battery cell and the fast charging performance. Optionally, compared with the first functional layer, the second functional layer is disposed closer to the negative electrode tab. Since the composite particles are not easily deformed, the separator film basically does not cause side effects such as extrusion to the negative electrode tab, making the kinetic performance of the negative electrode tab stable. Correspondingly, the first functional layer is disposed closer to the positive electrode tab.

[0451] Optionally, the second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. Optionally, the second inorganic particles include silicon oxide. The above-mentioned second inorganic particles can improve the heat resistance of the second functional layer and can form composite particles in cooperation with the non-fluoropolymer, further improving the cycle stability and kinetic performance of the separator film, and improving the cycle performance and fast charging performance of the battery cell.

[0452] The average particle size of the second inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, and optionally 5 nm to 20 nm. Exemplarily, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm or a range composed of any two of the above values. When the average particle size of the second inorganic particles is within the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0453] In the embodiments of the present application, the average particle size of the second inorganic particles has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, after obtaining the separator and drying the separator as a sample, the separator is cut by an ion beam cutter to form a cross-section. Subsequently, a scanning electron microscope is used to measure the particle size of the second inorganic particles in the separator, and the particle sizes of multiple, such as 50, second inorganic particles are measured, and the average value is calculated as the average particle size of the second inorganic particles.

[0454] In some embodiments, the ionic conductivity of the separator is 0.3 mS / cm to 0.6 mS / cm. Exemplarily, the ionic conductivity of the separator is 0.3 mS / cm, 0.35 mS / cm, 0.4 mS / cm, 0.45 mS / cm, 0.5 mS / cm, 0.55 mS / cm, 0.6 mS / cm or a range composed of any two of the above values.

[0455] When the ionic conductivity of the separator is within the above range, the migration ability of lithium ions in the separator can be further improved, and the fast charging performance of the battery cell can be improved.

[0456] In the embodiments of the present application, the ionic conductivity of the separator has the meaning well-known in the art and can be detected by using the equipment and methods well-known in the art. For example, Prepare a 2025 type button cell for testing: In a vacuum glove box, put a lithium sheet into the negative electrode case of the battery, add 150 μL of electrolyte, and the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), and then put the separator (with an area of 3.14 cm 2 , a thickness of 12 μm) to make it close to the lithium sheet, add another 25 μL of electrolyte, and finally place the positive electrode plate (the positive electrode plate can be the positive electrode plate in Example 1) on it and seal it. Take out the assembled button cell from the vacuum glove box and place it for 24 h for the next test.

[0457] Testing: On an electrochemical workstation, at 10 -1~10 6 Test within the frequency range of 6 Hz to obtain the separator resistance Rb, and calculate the ionic conductivity σ (unit: mS / cm) through the following formula: σ = L / (R b ×S) where: R b is the separator resistance, and L and S are the thickness and area of the separator to be measured, respectively.

[0458] [Electrolyte] In some embodiments, the battery cell further includes an electrolyte.

[0459] During the charge and discharge process of the battery cell, active ions such as lithium ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0460] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, such as 25 °C, is 10.5 mS / cm to 20 mS / cm, and can be optionally 15 mS / cm to 20 mS / cm. Exemplarily, the conductivity of the electrolyte at room temperature is 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm, 18.5 mS / cm, 19 mS / cm, 19.5 mS / cm, 20 mS / cm or the range composed of any two of the above values.

[0461] When the conductivity of the electrolyte at room temperature is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation, and can improve the fast charging performance of the battery cell.

[0462] In the embodiments of the present application, the conductivity of the electrolyte at room temperature is the ionic conductivity, and it can be detected by using the equipment and methods well-known in the art, such as testing with reference to the industry standard HG-T 4067-2015.

[0463] In some embodiments, the viscosity of the electrolyte at room temperature, such as 25 °C, is from 2.3 mPa·s to 3.5 mPa·s. Exemplarily, the viscosity of the electrolyte is 2.3 mPa·s, 2.4 mPa·s, 2.5 mPa·s, 2.6 mPa·s, 2.7 mPa·s, 2.8 mPa·s, 2.9 mPa·s, 3.0 mPa·s, 3.1 mPa·s, 3.2 mPa·s, 3.3 mPa·s, 3.4 mPa·s, 3.5 mPa·s or a range composed of any two of the above values.

[0464] When the viscosity of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0465] In the embodiments of the present application, the viscosity of the electrolyte has the meaning well known in the art and can be detected by equipment and methods well known in the art. For example, it can be detected according to GB / T10247-2008.

[0466] In some embodiments, the density of the electrolyte at room temperature, such as 25 °C, is from 1.05 g / mL to 1.35 g / mL. Exemplarily, the density of the electrolyte is 1.05 g / mL, 1.10 g / mL, 1.15 g / mL, 1.2 g / mL, 1.25 g / mL, 1.3 g / mL, 1.35 g / mL or a range composed of any two of the above values.

[0467] When the density of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

[0468] In the embodiments of the present application, the density of the electrolyte has the meaning well known in the art and can be detected by equipment and methods well known in the art. For example, it can be tested with reference to GB / T 2013-2010.

[0469] The electrolyte includes an organic solvent and an electrolyte salt. The types of the organic solvent and the electrolyte salt are not specifically limited and can be selected according to actual needs.

[0470] In some embodiments, the organic solvent includes a chain carboxylic acid ester solvent, and the mass content of the chain carboxylic acid ester solvent in the electrolyte is from 6% to 65%, and can be optionally 25% to 60%. Exemplarily, the mass content of the chain carboxylic acid ester solvent is 6%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or a range composed of any two of the above values.

[0471] When the mass content of the chain carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions.

[0472] In some embodiments, the chain carboxylic acid ester solvent includes a compound represented by Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a halogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group, R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0473] The above chain carboxylic acid ester solvent has a high conductivity, which is beneficial to improving the fast charging ability of the battery monomer.

[0474] Optionally, R1 includes a hydrogen atom, a halogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R1 includes a hydrogen atom, a halogen atom, a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0475] Optionally, R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group. Further optionally, R2 includes a C1-C2 alkyl group or a C1-C2 haloalkyl group.

[0476] In the above embodiments, the halogen atom includes one or more of a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Optionally, the halogen atom includes a fluorine atom.

[0477] In the above embodiments, the haloalkyl group includes one or more of a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group and an iodoalkyl group. Optionally, the haloalkyl group includes a fluoroalkyl group.

[0478] Exemplarily, the chain carboxylic acid ester solvent includes one or more of the compounds represented by Formula I-1 to Formula I-8,

[0479] In some embodiments, the organic solvent further includes a carbonate solvent.

[0480] Optionally, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. Further optionally, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate. The above carbonate solvent and the chain carboxylic acid ester solvent are used in combination, so that the conductivity of the electrolyte at room temperature is improved, which is beneficial to the migration of lithium ions.

[0481] Further optionally, the mass content of the carbonate solvent in the electrolyte is 20% to 80%, and can be optionally 25.5% to 42.5%. Exemplarily, the mass content of the carbonate solvent in the electrolyte is 20%, 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 42.5%, 45%, 48%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or a range composed of any two of the above values. The carbonate solvent with the above mass content can further improve the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0482] Exemplarily, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, and the mass content of the carbonate solvent is 20% to 80%.

[0483] In some embodiments, the electrolyte further contains additives. The additives can include negative electrode film-forming additives, or can include positive electrode film-forming additives, or can also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature performance of the battery, additives for improving the low-temperature power performance of the battery, etc.

[0484] In some embodiments, the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives, and can be optionally at least two. The above additives can improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to enhancing the fast charging performance of the battery cell and improving the cycle performance.

[0485] In some embodiments, the mass content of the additives in the electrolyte is 1% to 10%, optionally 2% to 8%, and further optionally 3.5% to 8%. Exemplarily, the mass content of the additives in the electrolyte is 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range composed of any two of the above values.

[0486] The additives with the above mass content can effectively improve the interfacial film performance on the positive electrode side and / or the negative electrode side, which is beneficial to enhancing the fast charging performance of the battery cell and improving the cycle performance.

[0487] Exemplarily, the carbonate additives include one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0488] Exemplarily, the sulfur-containing additives include one or more of ethylene sulfate (DTD), bis(ethylene sulfate) (2-DTD), butylene sulfite (BS), 1,3-propane sultone (PS), ethylene sulfite (ES), and methylene methanedisulfonate (MMDS).

[0489] Optionally, the lithium salt additive includes one or more of lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium tetrafluoroborate (LiBF4), and lithium bis(oxalate) borate (LiBOB).

[0490] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 0.5% to 9%, and can be optionally 2% to 6%.

[0491] Optionally, the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.1% to 4%, and can be optionally 0.5% to 3%.

[0492] Optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 0.5% to 9%, and the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.1% to 4%.

[0493] Further optionally, the mass content of vinylene carbonate (VC) in the electrolyte is 2% to 6%, and the mass content of fluoroethylene carbonate (FEC) in the electrolyte is 0.5% to 3%.

[0494] In some embodiments, the electrolyte salt includes a lithium salt, and the lithium salt includes one or more of a fluorosulfonylimide salt and lithium hexafluorophosphate (LiPF6). The above lithium salts are easy to dissociate, which is beneficial to the rapid migration of lithium ions, and the electrolyte system is relatively stable and not easily decomposed, which can improve the cycle performance of the battery monomer.

[0495] Optionally, the fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0496] Optionally, the lithium salt includes lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6). The molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.5 mol / L to 1.0 mol / L.

[0497] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.4 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.7 mol / L.

[0498] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.5 mol / L.

[0499] Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.2 mol / L, and the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.8 mol / L.

[0500] Optionally, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration in lithium hexafluorophosphate LiPF6 is from 0.2 to 1.0, and may be optionally from 0.2 to 0.5. Exemplarily, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration in lithium hexafluorophosphate LiPF6 is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a range composed of any two of the above values.

[0501] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt concentration in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to the standard JY / T 020-1996 "General Rules for Ion Chromatographic Analysis Methods" to qualitatively or quantitatively analyze the inorganic components / lithium salt concentration in the electrolyte by ion chromatography. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample for detection by ion chromatography.

[0502] In the embodiments of the present application, the types and contents of the organic components in the electrolyte have meanings well-known in the art, and can be detected by equipment and methods well-known in the art. For example, reference can be made to GB / T 9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to qualitatively and quantitatively analyze the organic components in the electrolyte by gas chromatography. In the embodiments of the present application, freshly prepared electrolyte can be taken as a sample, free electrolyte of a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cut-off voltage so that the charged state of the battery is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery can be taken as a sample for detection by ion chromatography.

[0503] In the embodiments of the present application, after quantitatively and qualitatively detecting each component in the electrolyte, each component is classified. Chain carboxylic ester solvents and carbonate solvents (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate) are used as the constituent components of the organic solvent. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated. Carbonate additives (such as vinylene carbonate, fluoroethylene carbonate), sulfur-containing additives, and lithium salt additives are used as additives to the electrolyte. Based on the mass of the electrolyte being 100%, the mass content of each component is calculated.

[0504] In some embodiments, the battery cell satisfies: 2.45 g / Ah ≤ d / A ≤ 3.5 g / Ah, optionally 2.45 g / Ah ≤ d / A ≤ 3.3 g / Ah, where d represents the mass of the electrolyte in the battery cell, in g, and A represents the rated capacity of the battery cell, in Ah. Exemplarily, d / A can be 3.5 g / Ah, 3.3 g / Ah, 3.2 g / Ah, 3.0 g / Ah, 2.8 g / Ah, 2.5 g / Ah, 2.45 g / Ah or a range composed of any two of the above values.

[0505] d / A can reflect the liquid retention ability of the electrolyte. When d / A is within the above range, the electrolyte can play a good wetting role on the positive electrode plate and the negative electrode plate, and can also improve the migration rate of lithium ions in the liquid phase, which is beneficial to improving the fast charging ability of the battery cell.

[0506] In the embodiments of the present application, d / A of the battery cell can be understood as the liquid retention coefficient, and can be detected by using equipment and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.65 V and the cut-off voltage of battery discharging as 2.0 V in accordance with GB / T31486-2015 "Electrical Performance Requirements and Test Methods for Power Batteries for Electric Vehicles" for illustration, At 25 °C, the battery cell is charged to 3.65 V at 0.33 C, then charged at a constant voltage until 0.05 C, and then discharged at a constant current of 0.33 C to 2.0 V. The discharged capacity A is used as the denominator. The battery cell is weighed as M0, and then the positive electrode plate, the negative electrode plate, the separator and the electrolyte are disassembled. The free electrolyte is in a bag. All the above solid components are placed in an oven at 60 °C and baked for more than 4 hours (including but not limited to the positive electrode plate, the negative electrode plate, the separator, and other mechanical parts contributing to M0 of the disassembled battery cell), and then all the components of the battery cell are weighed as M1. The weight difference between M0 and M1 is used as the numerator. The liquid retention coefficient is equal to the value obtained by dividing the weight difference d between M0 and M1 by the capacity A.

[0507] In some embodiments, the positive electrode plate, the separator and the negative electrode plate can be made into an electrode assembly by a winding process and / or a stacking process.

[0508] As Figure 24 shown, in some embodiments of the present application, the battery cell 7 according to the embodiments of the present application can be assembled into a battery module 6. The number of battery cells 7 included in the battery module 6 can be one or more, and the specific number can be adjusted according to the application and capacity of the battery module 6.

[0509] If there are multiple battery cells 7, the multiple battery cells 7 can be connected in series, in parallel, or in a combined series-parallel configuration. A combined series-parallel configuration means that there are both series and parallel connections among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series, in parallel, or in a combined series-parallel configuration together, and then the whole formed by the multiple battery cells 7 is accommodated in the accommodating portion of the battery module 6. Of course, it is also possible that the multiple battery cells 7 are first connected in series, in parallel, or in a combined series-parallel configuration to form battery modules 6, and then the multiple battery modules 6 are connected in series, in parallel, or in a combined series-parallel configuration to form a whole and are accommodated in the accommodating portion. Optionally, the battery module 6 can also include an accommodating portion with an accommodating space, and the multiple battery cells 7 are accommodated in this accommodating space.

[0510] In some embodiments, the battery device may include a first busbar 61 and a second busbar 62. The first busbar 61 is used for electrically connecting the first electrode terminal, and the second busbar 62 is used for electrically connecting the second electrode terminal.

[0511] As Figure 25 shown, in some embodiments, the above-mentioned battery module 6 can also be assembled into a battery pack 2, and the number of battery modules 6 included in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. The battery device in this article can be either the battery module 6 or the battery pack 2.

[0512] The battery pack 2 may include a box body 5 and multiple battery modules 6 disposed in the box body 5. The box body 5 includes a first box body portion 5a and a second box body portion 5b. The box body 5 has an accommodating space 5c. The first box body portion 5a is used for covering the second box body portion 5b and forming a closed space for accommodating the battery module 6. The multiple battery modules 6 can be arranged in the box body 5 in any manner.

[0513] The first box body portion 5a and the second box body portion 5b are covered with each other, and the first box body portion 5a and the second box body portion 5b jointly define an accommodating space 5c for accommodating the battery cells. The second box body portion 5b can be a hollow structure with one end open, and the first box body portion 5a is a plate-like structure. The first box body portion 5a covers the open side of the second box body portion 5b to form the box body 5 with the accommodating space 5c. The first box body portion 5a and the second box body portion 5b can also both be hollow structures with one side open, and the open side of the first box body portion 5a covers the open side of the second box body portion 5b to form the box body 5 with the accommodating space 5c. Of course, the first box body portion 5a and the second box body portion 5b can be of various shapes, such as a cylinder, a cuboid, etc.

[0514] To improve the sealing performance after the connection between the first box body portion 5a and the second box body portion 5b, a sealing member, such as a sealant, a sealing ring, etc., can also be provided between the first box body portion 5a and the second box body portion 5b.

[0515] Assume that the first box body part 5a covers the top of the second box body part 5b. The first box body part 5a can also be called the upper box cover, and the second box body part 5b can also be called the lower box body. In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 0% state of charge (SOC) to 100% SOC, the temperature of the external environment where the battery pack 2 is located, for example, the room temperature, is 30°C.

[0516] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% SOC to 80% SOC, the temperature of the external environment where the battery pack 2 is located is 30°C.

[0517] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% SOC to 80% SOC, it includes multiple charging steps. The difference between the maximum state of charge of any charging step and the maximum state of charge of its adjacent charging step is less than or equal to 5% SOC, such as 1% SOC, 1.5% SOC, 2% SOC, 2.5% SOC, 3% SOC, 3.5% SOC, 4% SOC, 4.5% SOC, 5% SOC, or a range composed of any two of the above values.

[0518] The battery pack 2 or any battery cell constituting the battery pack 2 from 10% SOC to 40% SOC includes multiple charging steps. For any charging step, it can be charged at any rate between 5C and 10C. The charging rate corresponding to each charging step can be any value among 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a value within a range composed of any two of the above values.

[0519] Exemplarily, the charging steps of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% to 80% can be carried out as follows: Constant current charge from 10% SOC to 15% SOC at 5.0C, Constant current charge from 15% SOC to 20% SOC at 5.0C, Constant current charge from 20% SOC to 25% SOC at 5.0C, Constant current charge from 25% SOC to 30% SOC at 5.0C, Constant current charge from 30% SOC to 35% SOC at 5.0C, Constant current charge from 35% SOC to 40% SOC at 5.0C, Constant current charge from 40% SOC to 45% SOC at 4.6C, Charge from 45% SOC to 50% SOC at a constant current of 4.3C, Charge from 50% SOC to 55% SOC at a constant current of 4.0C, Charge from 55% SOC to 60% SOC at a constant current of 3.7C, Charge from 60% SOC to 65% SOC at a constant current of 3.4C, Charge from 65% SOC to 70% SOC at a constant current of 3.1C, Charge from 70% SOC to 75% SOC at a constant current of 2.9C, Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0520] In some embodiments, the charging time of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, and can be selected from 5 min to 10.5 min. The temperature of the external environment of the battery pack 2 at 10% state of charge is room temperature, for example, 30°C. Exemplarily, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min or the range composed of any two of the above values In some embodiments, the volumetric energy density of the battery cell is from 390 Wh / L to 500 Wh / L, and can be selected from 410 Wh / L to 470 Wh / L. Exemplarily, the volumetric energy density of the battery cell is 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 440 Wh / L, 450 Wh / L, 460 Wh / L, 470 Wh / L, 480 Wh / L, 490 Wh / L, 500 Wh / L or the range composed of any two of the above values. The volumetric energy density of the battery cell is relatively high.

[0521] In the embodiments of the present application, the volumetric energy density of the battery cell has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, taking the upper limit voltage of battery charging as 3.65V and the cut-off voltage of battery discharging as 2.0V as an example for illustration, The battery cell is placed at 25°C and charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage to 0.05C, and discharged at a constant current of 0.33C to 2.0V. Record the discharge capacity A0 at this time, unit: Ah. Use a caliper to measure the length, width, and height of the battery cell (generally calculated based on the outer shell size of the battery, excluding the height of the electrode terminals and the insulating film outside the outer shell), and calculate the volume V0 of the single battery cell, unit: L. The volume energy density VED of the battery cell = (A0 × discharge platform voltage) / V0, unit: Wh / L.

[0522] In some embodiments, the weight energy density of the battery cell is 175 Wh / Kg to 210 Wh / Kg. Exemplarily, the weight energy density of the battery cell is 175 Wh / Kg, 180 Wh / Kg, 185 Wh / Kg, 190 Wh / Kg, 200 Wh / Kg, 210 Wh / Kg or the range composed of any two of the above values. The volume energy density of the battery cell is relatively high.

[0523] In the embodiments of the present application, the weight energy density of the battery cell has the meaning well-known in the art, and can be detected by using the equipment and methods well-known in the art. For example, taking the battery charging upper limit voltage of 3.65V and the battery discharge cut-off voltage of 2.0V as an example for illustration. The battery cell is placed at 25°C and charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage to 0.05C; discharged at a constant current of 0.33C to 2.0V, record the discharge capacity A0 at this time, unit: Ah; use a scale to measure the mass of the electrode assembly in the battery cell, and calculate the weight energy density of the battery cell, unit: Wh / Kg.

[0524] Electric device The second aspect of the embodiments of the present application provides an electrical device, which includes the battery device of the embodiments of the present application, such as a battery cell, a battery module or a battery pack. The battery cell, the battery module or the battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or an extended-range electric vehicle, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spaceship, etc. The electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool and a railway electric tool, for example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact electric drill, a concrete vibrator and a power planer, etc. The embodiments of the present application do not impose special restrictions on the above electrical devices. The electrical device can select a battery cell, a battery module or a battery pack according to its usage requirements.

[0525] Figure 26 It is a schematic diagram of an electrical device 1 as an example. The electrical device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device 1 for high power and high energy density, a battery pack or a battery module can be adopted.

[0526] A battery pack 2 is arranged inside the electrical device 1. The battery pack 2 can be arranged at the bottom, the head or the tail of the electrical device 1. The battery pack 2 can be used for power supply of the electrical device 1. For example, the battery pack 2 can be used as the operating power source of the electrical device 1 and can also be used as the driving power source of the electrical device 1, replacing or partially replacing fuel or natural gas to provide driving power for the electrical device 1.

[0527] The electrical device 1 may further include a controller 3 and a motor 4. The controller 3 is used to control the battery pack 2 to supply power to the motor 4. For example, it is used for the startup, navigation and working power requirements of the electrical device 1 during driving.

[0528] Another example of the electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires being thin and light, and a battery cell can be used as the power source.

[0529] The charging process of the electrical device can select the following charging methods: Charge from 10% SOC to 15% SOC at a constant current of 5.0C, Charge from 15% SOC to 20% SOC at a constant current of 5.0C, Charge from 20% SOC to 25% SOC at a constant current of 5.0C, Charge from 25% SOC to 30% SOC at a constant current of 5.0C, Charge from 30% SOC to 35% SOC at a constant current of 5.0C, Charge from 35% SOC to 40% SOC at a constant current of 5.0C, Charge from 40% SOC to 45% SOC at a constant current of 4.6C, Charge from 45% SOC to 50% SOC at a constant current of 4.3C, Charge from 50% SOC to 55% SOC at a constant current of 4.0C, Charge from 55% SOC to 60% SOC at a constant current of 3.7C, Charge from 60% SOC to 65% SOC at a constant current of 3.4C, Charge from 65% SOC to 70% SOC at a constant current of 3.1C, Charge from 70% SOC to 75% SOC at a constant current of 2.9C, Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

[0530] In some embodiments, the charging time of the electrical device from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, and can be optionally 5 min to 10.5 min. The temperature of the external environment of the battery pack 2 at 10% state of charge is 30°C. Exemplarily, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min or a range composed of any two of the above values.

[0531] Embodiment The following examples more specifically describe the content disclosed in the embodiments of the present application. These examples are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the embodiments of the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples are commercially available.

[0532] Example 1-1 1. Preparation of the positive electrode plate The positive electrode plate includes a positive current collector portion, a positive conductive layer on the positive current collector portion, and a positive electrode film layer. The positive current collector portion is an aluminum foil, and the thickness of the aluminum foil is the same as that of the positive electrode tab. The positive conductive layer on the positive current collector portion is a film layer formed by uniformly coating a mixture of a positive conductive agent, superconducting carbon, a positive binder, polyvinylidene fluoride (PVDF), and a solvent, N-methylpyrrolidone (NMP), on the surface of the current collector portion. The thickness is 1 μm. The mass content of the positive conductive agent in the positive conductive layer is 40%, and the mass content of the positive binder is 60%.

[0533] The positive electrode film layer includes a film layer formed by uniformly coating a positive electrode slurry (with a solvent of N-methylpyrrolidone NMP) on the surface of the positive conductive layer and then drying and cold pressing. The positive electrode film layer includes a positive active material, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black in a weight ratio of 97:2:1.

[0534] The positive active material includes lithium iron phosphate and a coating layer. The coating layer coats the surface of the lithium iron phosphate. The coating layer includes lithium iron titanium phosphate Li2FeTi(PO4)3 and amorphous carbon. The Dv50 of the positive active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0535] The single-sided coating weight of the positive electrode film layer is 290 mg / 1540.25 mm 2 。

[0536] 2. Preparation of the negative electrode plate The negative electrode plate includes a negative current collector portion, a negative conductive layer on the negative current collector portion, and a negative electrode film layer. The negative current collector portion is a copper foil, and the thickness of the copper foil is the same as that of the negative electrode tab. The negative conductive layer on the negative current collector portion is a film layer formed by uniformly coating a mixture of a negative conductive agent, superconducting carbon, a negative binder, styrene-butadiene rubber (SBR), a thickening agent, sodium carboxymethyl cellulose (CMC-Na), and a solvent, water, on the surface of the negative current collector portion. The thickness is 1 μm. The mass content of the negative conductive agent in the negative conductive layer is 35%, the mass content of the negative binder in the negative conductive layer is 60%, and the mass content of the thickening agent in the negative conductive layer is 5%. The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (with a solvent of deionized water) on the surface of the negative conductive layer and then drying and cold pressing.

[0537] The single-sided coating weight of the negative electrode film layer is 135 mg / 1540.25 mm 2 。

[0538] The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer. The first negative electrode film layer is located on the surface of the negative conductive layer, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0539] The first negative electrode film layer comprises graphite particles, conductive agent acetylene black, a first lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer), negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose in a mass ratio of 96.5:0.5:0.5:1.5:1; the mass content of lithium element in the first lithium-containing binder is 4.8%; the Dv50 of the graphite particles is 11.3 μm, the graphite particles include artificial graphite and an amorphous carbon layer, the amorphous carbon layer coats the surface of the artificial graphite, and the mass content of the amorphous carbon is 3.5%.

[0540] The second negative electrode film layer comprises graphite particles, conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer), negative electrode binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose in a mass ratio of 97.5:0.5:0.5:0.5:1; the mass content of lithium element in the second lithium-containing binder is 4.8%; the Dv50 of the graphite particles is 11.3 μm, the graphite particles include artificial graphite and an amorphous carbon layer, the amorphous carbon layer coats the surface of the artificial graphite, and the mass content of the amorphous carbon is 3.5%.

[0541] 3. Separator The separator includes a base film, the base film is a 7-μm polyethylene film layer, and the porosity is 42%.

[0542] 4. Preparation of electrolyte The electrolyte includes organic solvent, lithium salt, and additive.

[0543] The organic solvent includes 48.5% chain carboxylic ester solvent (ethyl acetate) and 32.5% carbonate solvent (24.5% ethylene carbonate EC, 8% dimethyl carbonate), and the mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0544] Based on the mass of the electrolyte, the mass content of the additive is 6.5%, which includes vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES, and lithium difluorooxalate borate LiDFOB in a mass ratio of 5:0.5:0.5:0.5.

[0545] The lithium salt includes 1 mol / L lithium hexafluorophosphate LiPF6.

[0546] The conductivity of the electrolyte at room temperature is 16.4 mS / cm.

[0547] 5. Preparation of battery cell Stack the above positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, and obtain an electrode assembly through the winding process; place the electrode assembly in an outer packaging case, inject electrolyte after drying, and obtain a battery cell through processes such as vacuum packaging, standing, forming, and shaping. The compaction density of the positive electrode film layer is 2.60 / cm at 100% SOC 3 , and the compaction density of the negative electrode film layer is 1.25 g / cm at 100% SOC 3 .

[0548] Comparative Example 1-1 A battery cell was prepared using a method similar to that of Example 1. Different from Example 1, the area of the projection surface of the positive terminal and the area of the projection surface of the negative terminal were adjusted.

[0549] Examples 1-2 to 1-8 A battery cell was prepared using a method similar to that of Example 1. Different from Example 1, the size of the weld mark area and the weld mark position at the welding part were adjusted.

[0550] The specific parameters of the examples and comparative examples are shown in Tables 1 and 2.

[0551] Performance test 1. Lithium deposition area test of the battery cell At 60 °C, charge the battery cell at a constant current of 1C until the charging cut-off voltage of 3.65V, and then discharge it at a constant current of 1C to 2.0V. This is one charge-discharge cycle; after 200 cycles, fully charge it to 100% SOC according to the corresponding charging strategy, disassemble the negative electrode sheet in the battery pack, unfold the negative electrode sheet, observe the lithium deposition area (grayish-white area), and measure the lithium deposition area.

[0552] 2. Number of cycles for the battery cell to cycle to 70% SOH At 30 °C, charge and discharge the battery cell in cycles until the cycle capacity retention rate (i.e., Cn / C0 × 100%) is 70%, and record the number of cycles. The more the number of cycles, the better the cycle performance of the battery cell.

[0553] The charging steps include the following steps: Charge at a constant current of 5.0C from 0% SOC to 5% SOC; Charge at a constant current of 5.0C from 5% SOC to 10% SOC; Charge at a constant current of 5.0C from 10% SOC to 15% SOC; Charge at a constant current of 5.0C from 15% SOC to 20% SOC; Charge at a constant current of 5.0C from 20% SOC to 25% SOC; Charge from 25% SOC to 30% SOC at a constant current of 5.0C; Charge from 30% SOC to 35% SOC at a constant current of 5.0C; Charge from 35% SOC to 40% SOC at a constant current of 5.0C; Charge from 40% SOC to 45% SOC at a constant current of 4.6C; Charge from 45% SOC to 50% SOC at a constant current of 4.3C; Charge from 50% SOC to 55% SOC at a constant current of 4.0C; Charge from 55% SOC to 60% SOC at a constant current of 3.7C; Charge from 60% SOC to 65% SOC at a constant current of 3.4C; Charge from 65% SOC to 70% SOC at a constant current of 3.1C; Charge from 70% SOC to 75% SOC at a constant current of 2.9C; Charge from 75% SOC to 80% SOC at a constant current of 2.7C; Charge from 80% SOC to 85% SOC at a constant current of 1.8C; Charge from 85% SOC to 90% SOC at a constant current of 1.3C; Charge from 90% SOC to 95% SOC at a constant current of 0.7C; Charge from 95% SOC to 98% SOC at a constant current of 0.33C; Charge from 98% SOC to 100% SOC at a constant current of 0.1C.

[0554] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0555] The discharging strategy is as follows: discharge at a constant current of 0.33C until the cut-off voltage, for example, 2.0V.

[0556] The test results are shown in Table 3.

[0557] Table 1

[0558] In Table 1, L1 represents the distance between the projection plane of the welding mark area of the positive electrode connecting piece and the positive electrode tab along the thickness direction of the positive terminal and the projection plane of the welding mark area of the positive terminal and the positive electrode bus bar along the thickness direction of the positive terminal.

[0559] Table 2

[0560] In Table 2, L1 represents the distance between the projection plane of the welding mark area of the negative electrode connecting piece and the negative electrode tab along the thickness direction of the negative terminal and the projection plane of the welding mark area of the negative terminal and the negative electrode busbar along the thickness direction of the negative terminal.

[0561] Table 3

[0562] In Table 1, the charging time of the battery cells in each example and comparative example at 10% SOC to 80% SOC is less than or equal to 10.5 min.

[0563] In Comparative Example 1, the areas of the projection planes of the positive terminal and the negative terminal along their own thickness directions are small, resulting in more heat generated near the terminals and poor cycle stability of the active material; and the current density is too large, making lithium deposition likely to occur.

[0564] In the example of the present application, the area of the projection plane of the positive terminal along its own thickness direction is 200 mm 2 to 600 mm 2 ; and / or the area of the projection plane of the negative terminal along its own thickness direction is 200 mm 2 to 600 mm 2 ; so that less heat is generated near the terminals, the cycle stability of the active material is higher, lithium deposition is not likely to occur, the use reliability is improved, and a certain weight energy density can be maintained.

[0565] Example 2-1 A battery cell was prepared by a method similar to that of Example 1-1. Different from Example 1-1, a laminated process was used to prepare the electrode assembly, and the battery cell was thus prepared.

[0566] Comparative Example 2-1 and Example 2-2 A battery cell was prepared by a method similar to that of Example 2-1. Different from Example 2-1, the areas of the projection planes of the positive terminal and the negative terminal were adjusted.

[0567] Test result Table 4

[0568] In Table 4, the charging time of the battery cells in each example and comparative example at 10% SOC to 80% SOC is less than or equal to 10.5 min.

[0569] In Comparative Example 2-1, the areas of the projection planes of the positive terminal and the negative terminal along their own thickness directions are large, for example, greater than 600 mm 2 , and lithium deposition is not likely to occur, but its weight energy density decreases.

[0570] In the embodiment of the present application, the area of the projection plane of the positive terminal along its own thickness direction is 200 mm 2 to 600 mm 2 ; and / or the area of the projection plane of the negative terminal along its own thickness direction is 200 mm 2 to 600 mm 2 ; such that less heat is generated near the terminal, the cycle stability of the active material is relatively high, and lithium plating is not likely to occur, the use reliability is improved, and a certain weight energy density can be maintained.

[0571] Although the illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and the embodiments can be changed, substituted, and modified without departing from the spirit, principle, and scope of the present application.

Claims

1. A battery cell, characterized in that, The battery cell includes: A housing assembly, including a housing and a first electrode terminal disposed on the housing; and An electrode assembly, accommodated within the housing, the electrode assembly including a first electrode tab and a second electrode tab, both the first electrode tab and the second electrode tab including a coated portion and an electrode ear, the coated portion including an active material layer, and the electrode ear not being provided with an active material layer. Among them, One of the first electrode tab and the second electrode tab is a positive electrode tab, and the other is a negative electrode tab. The active material layer in the positive electrode tab includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate having an olivine structure; the electrode ear in the first electrode tab is used for electrically connecting the first electrode terminal and the coated portion in the first electrode tab, Among them, the area of the projection plane of the first electrode terminal along its own thickness direction is 300 mm 2 to 500 mm 2 , and the charging time of the battery cell from 10% state of charge to 80% state of charge is 5 min to 10.5 min; The first electrode terminal is used to connect to an external first bus bar, and the area of the connection region between the first electrode terminal and the first bus bar is 60 mm 2 to 150 mm 2 .

2. The battery cell according to claim 1, wherein, The electrode ear in the first electrode tab is directly connected to the first electrode terminal.

3. The battery cell according to claim 2, wherein The housing includes an electrode lead-out hole, the first electrode terminal covers the electrode lead-out hole, and the first electrode terminal is further connected to a side of the housing facing the coated portion.

4. The battery cell according to claim 2 or 3, characterized in that, The first electrode terminal includes a bearing portion having a hollow structure, at least a part of the electrode ear in the first electrode tab is accommodated within the bearing portion, and the inner wall of the bearing portion is connected to the electrode ear in the first electrode tab.

5. The battery cell according to claim 4, wherein The inner wall includes an end wall and a side wall, and the side wall is disposed around the outside of the end wall; The electrode ear in the first electrode tab is connected to the end wall; and / or the electrode ear in the first electrode tab is connected to the side wall.

6. The battery cell according to claim 1, characterized in that, The battery cell includes a first adapter, the first adapter connects the electrode ear of the first electrode tab and the first electrode terminal, and the electrode ear of the first electrode tab is the first electrode ear.

7. The battery cell according to claim 6, characterized in that, The housing includes an electrode lead-out hole, the first electrode terminal covers the electrode lead-out hole, and the first electrode terminal is disposed on a side of the housing facing away from the coated portion.

8. The battery cell according to claim 6 or 7, characterized in that, The area of the connection region between the first adapter and the first electrode terminal is 35 mm 2 to 50 mm 2 .

9. The battery cell according to claim 6, wherein The area of the connection region between the first adapter and the first tab is 80 mm 2 to 160 mm 2 .

10. The battery cell according to claim 6, wherein The first adapter is located between the first electrode ear and the first electrode terminal; A projection plane of a connection region between the first adapter and the first electrode ear along a thickness direction of the first electrode terminal is a first projection plane; The first electrode terminal is used for connecting to an external first bus bar, and a projection plane of a connection region between the first electrode terminal and the first bus bar along the thickness direction of the first electrode terminal is a second projection plane. Among them, A distance between a geometric center of the first projection plane and a geometric center of the second projection plane is 0 to 50 mm.

11. The battery cell according to claim 6, wherein, The first adapter is a positive electrode adapter, and a thickness of the positive electrode adapter is 0.6 mm to 2.0 mm; and / or The cross-sectional area of the positive electrode adapter perpendicular to its own thickness direction is 30 mm 2 to 60 mm 2 .

12. The battery cell according to claim 6, wherein, The first adapter is a negative electrode adapter, and a thickness of the negative electrode adapter is 0.5 mm to 1.5 mm; and / or The cross-sectional area of the negative electrode adapter perpendicular to its own thickness direction is 24 mm 2 to 60 mm 2 .

13. The battery cell according to claim 1, characterized in that, The tab in the first electrode sheet is a positive tab, and the cross-sectional area of the positive tab on the side close to the coating part is 0.45 mm 2 to 1.0 mm 2 .

14. The battery cell according to claim 1, characterized in that, The tab in the first electrode sheet is a negative tab, and the cross-sectional area of the negative tab on the side close to the coating portion is 0.18 mm 2 to 1.0 mm 2 .

15. The battery cell according to claim 1, characterized in that, The electrode assembly is a stacked structure, and the first electrode tab and the second electrode tab are stacked along a thickness direction of the electrode assembly, The first electrode terminal is connected to the tab of the first electrode plate, and the area of the connection region between the first electrode terminal and the tab of the first electrode plate is 140 mm 2 to 420 mm 2 .

16. The battery cell according to claim 1, characterized in that, There are multiple first electrode terminals, The multiple first electrode terminals are located on both sides of the coated portion; or The multiple first electrode terminals are located on the same side of the coated portion.

17. The battery cell according to claim 1, wherein The outer shell assembly further includes a second electrode terminal disposed on the outer shell. The tab of the second electrode plate is used for electrically connecting the second electrode terminal and the coated portion of the second electrode plate. The area of the projection plane of the second electrode terminal along its own thickness direction is 200 mm 2 to 600 mm 2 .

18. The battery cell according to claim 1, characterized in that, The outer shell includes a housing and an end cap. The housing has a cuboid structure, the housing accommodates the electrode assembly, and the housing has an opening. The end cap covers the opening, and the first electrode terminal is provided on the end cap. The size of the projection plane of the first electrode terminal in the thickness direction of the battery cell in the thickness direction of the first electrode terminal itself is a first size, and the size of the end cap in the thickness direction of the battery cell is a second size. The ratio of the first size to the second size is greater than 0 and less than or equal to 0.

85.

19. The battery cell according to claim 18, characterized in that, The ratio of the first size to the second size is 0.40 to 0.

85.

20. The battery cell according to claim 1, characterized in that, The electrode assembly has a wound structure, and the first electrode sheet and the second electrode sheet are wound in one direction. In the direction from the coated portion to the end cap of the outer shell, the size of the coated portion of the first electrode sheet is 60 mm to 120 mm.

21. The battery cell according to claim 1, wherein, The electrode assembly has a stacked structure, and the first electrode sheet and the second electrode sheet are stacked in the thickness direction of the battery cell. In the direction from the coated portion to the end cap of the outer shell, the size of the coated portion of the first electrode sheet is 300 mm to 550 mm.

22. The battery cell according to claim 1, characterized in that, The electrode assembly has a wound structure, and the first electrode sheet and the second electrode sheet are wound in one direction. The projection plane of the first electrode terminal in the thickness direction of the first electrode terminal itself is circular.

23. The battery cell according to claim 1, characterized in that, The electrode assembly has a stacked structure, and the first electrode sheet and the second electrode sheet are stacked in the thickness direction of the battery cell. The projection plane of the first electrode terminal in the thickness direction of the first electrode terminal itself is rectangular.

24. The battery cell according to claim 1, characterized in that, The coated portion of the first electrode sheet includes a first straight section, and the coated portion of the second electrode sheet includes a second straight section. The first straight section and the second straight section are stacked in the thickness direction of the electrode assembly. The ratio of the number of tabs of the first electrode sheet to the number of the first straight sections of the first electrode sheet is 0.5 to 2. The battery cell further includes an electrolyte. The electrolyte includes an organic solvent. The organic solvent includes a chain carboxylic acid ester solvent. The mass content of the chain carboxylic acid ester solvent in the electrolyte is 6% to 65%.

25. The battery cell according to claim 24, characterized in that, The mass content of the chain carboxylic acid ester solvent in the electrolyte is 25% to 60%.

26. The battery cell according to claim 24 or 25, characterized in that, The ratio of the number of tabs of the second electrode sheet to the number of the second straight sections of the second electrode sheet is 0.5 to 2.

27. The battery cell according to claim 24, wherein, The electrode assembly has a wound structure, and the first electrode sheet and the second electrode sheet are wound in one direction. The first electrode sheet has a plurality of tabs.

28. The battery cell according to claim 27, wherein The ratio of the number of tabs of the first electrode sheet to the number of the first straight sections of the first electrode sheet is 0.5 to 1.

29. The battery cell according to claim 24, wherein, The electrode assembly has a stacked structure. The first electrode sheet and the second electrode sheet both have a plurality of sheets, and each first electrode sheet has at least one tab.

30. The battery cell according to claim 29, wherein The ratio of the number of tabs of the first electrode sheet to the number of the first straight sections of the first electrode sheet is 1 to 2.

31. The battery cell according to claim 1, wherein, The tab includes: a tab body connected to the coated portion; and A plurality of tab protrusions are all connected to one side of the tab body facing away from the coated portion, and there is a gap between adjacent tab protrusions. Each tab protrusion is used for electrically connecting with the electrode terminal.

32. The battery cell according to claim 1, wherein, The tab in the first electrode plate is a positive tab, and the thickness of the positive tab is 10 μm to 20 μm.

33. The battery cell according to claim 1, characterized in that, The tab in the first electrode plate is a negative tab, and the thickness of the negative tab is 4 μm to 10 μm.

34. The battery cell according to claim 24, characterized in that, The conductivity of the electrolyte at room temperature is 10.5 mS / cm to 20 mS / cm.

35. The battery cell according to claim 34, characterized in that, The conductivity of the electrolyte at room temperature is 15 mS / cm to 20 mS / cm.

36. The battery cell according to claim 24, wherein The chain carboxylic ester solvent includes the compound shown in Formula I. Formula I, In Formula I, R1 includes a hydrogen atom, a halogen atom, a C1-C5 alkyl group or a C1-C5 haloalkyl group. R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

37. The battery cell according to claim 36, wherein R1 includes a hydrogen atom, a halogen atom, a C1-C3 alkyl group or a C1-C3 haloalkyl group. R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group.

38. The battery cell according to claim 36 or 37, wherein The halogen atom includes a fluorine atom, and / or the haloalkyl group includes a fluoroalkyl group.

39. The battery cell according to claim 24, characterized in that, The chain carboxylic ester solvent includes one or more of the compounds shown in Formula I-1 to Formula I-8. 。 40. The battery cell according to claim 24, characterized in that, The organic solvent further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

41. The battery cell according to claim 40, wherein The mass content of the carbonate solvent in the electrolyte is 20% to 80%.

42. The battery cell according to claim 24, wherein The electrolyte further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive and a lithium salt additive.

43. The battery cell according to claim 42, wherein, The carbonate additive includes one or more of vinylene carbonate and fluoroethylene carbonate, and / or The sulfur-containing additive includes one or more of ethylene sulfate, bis(ethylene sulfate), butene sulfite, 1,3-propane sultone, ethylene sulfite and methylene methanedisulfonate, and / or The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate and lithium bis(oxalate) borate.

44. The battery cell according to claim 42 or 43, characterized in that, The mass content of the additive in the electrolyte is 1% to 10%.

45. The battery cell according to claim 24, wherein The electrolyte further includes a lithium salt, and the lithium salt includes one or more of a fluorosulfonylimide salt and lithium hexafluorophosphate.

46. The battery cell according to claim 45, characterized in that, The fluorosulfonylimide salt includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide.

47. The battery cell according to claim 46, characterized in that, The lithium salt includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate. The molar concentration of lithium bis(fluorosulfonyl)imide is 0.2 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate is 0.5 mol / L to 1.0 mol / L.

48. The battery cell according to claim 24, wherein The viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s; and / or The density of the electrolyte at room temperature is 1.05 g / mL to 1.35 g / mL.

49. The battery cell according to claim 1, characterized in that, The lithium-containing phosphate with olivine structure includes: phosphate particles, and a coating layer that coats the phosphate particles, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

50. The battery cell according to claim 49, wherein The phosphate particles comprise a compound of the general formula Li x1 A y1 Me a M b P 1-c X c Y z wherein 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.9 ≤ x1 + y1 ≤ 1.3, 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5, 0 ≤ c ≤ 0.5, 3 ≤ z ≤ 5, A comprises one or more of Na, K, Mg, Me comprises one or more of Mn, Fe, Co, Ni, M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X comprises one or more of S, Si, Cl, B, C, N, and Y comprises one or more of O, F.

51. The battery cell according to claim 49 or 50, characterized in that, The coating layer comprises a fast ion conductor with the general formula Li 3- d Fe 2-d M2 d (PO x2 ) y2 , where M2 comprises one or more elements of Ti, Zr, Hf, Ge, and Sn, 0 ≤ d ≤ 1, 0 < x2 < 5, and 0 < y2 < 4.

52. The battery cell according to claim 49, wherein, The graphitization degree of the lithium-containing phosphate with olivine structure is 0.15 to 0.

32.

53. The battery cell according to claim 52, wherein The graphitization degree of the lithium-containing phosphate with olivine structure is 0.19 to 0.

26.

54. The battery cell according to claim 49, characterized in that, The mass content of carbon element in the lithium-containing phosphate with olivine structure is 1% to 2%. The specific surface area of the lithium-containing phosphate with an olivine structure is 5 m 2 / g to 18 m 2 / g.

55. The battery cell according to claim 54, wherein The specific surface area of the lithium-containing phosphate with olivine structure is 7.5 m 2 / g to 14 m 2 / g.

56. The battery cell according to claim 1, characterized in that, The lithium-containing phosphate with olivine structure is granular, and its volume distribution particle size satisfies: 1 µm ≤ Dv50 ≤ 2 µm, 0.4 µm ≤ Dv10 ≤ 0.7 µm.

57. The battery cell according to claim 1, wherein, The lithium-containing phosphate with olivine structure is granular. The lithium-containing phosphate with olivine structure includes secondary particles, and the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm.

58. The battery cell according to claim 1, characterized in that, The negative electrode sheet includes a negative electrode active material, the negative electrode active material includes a carbon-based material, the carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%.

59. The battery cell according to claim 58, characterized in that, The graphite particles include: artificial graphite, including secondary particles, and a carbon coating layer coated on the surface of the artificial graphite.

60. The battery cell according to claim 59, wherein, Based on the mass of the graphite particles, the mass content of the carbon coating layer is 2% to 5%.

61. The battery cell according to claim 1, wherein The battery cell includes a housing that houses the electrode assembly. The housing includes steel, and the thickness of the housing is 0.1 mm to 0.5 mm.

62. The battery cell according to claim 61, wherein, The thickness of the housing is 0.2 mm to 0.35 mm.

63. A battery device, characterized in that, The battery device includes a plurality of battery cells as described in any one of claims 1 to 62, and the charging time of the battery device from 10% state of charge to 80% state of charge is 5 min to 10.5 min.

64. The battery device according to claim 63, wherein, The battery device includes a first busbar. The first busbar is electrically connected to the first electrode terminal in the battery cell, and the area of the connection region between the first electrode terminal and the first busbar is 60 mm 2 to 150 mm 2 .

65. The battery device according to claim 64, wherein, The first adapter of the battery cell is located between the first tab of the battery cell and the first electrode terminal. The projection plane of the connection area between the first adapter and the first tab along the thickness direction of the first electrode terminal is the first projection plane. The projection plane of the connection area between the first electrode terminal and the first busbar along the thickness direction of the first electrode terminal is the second projection plane, where the distance between the geometric center of the first projection plane and the geometric center of the second projection plane is 0 to 50 mm.

66. An electrical device, characterized in that, The electrical device includes a battery device as described in any one of claims 63 to 65.

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