Battery cells, battery devices, and power-consuming devices

Abstract

The present application relates to a battery cell, a battery device and an electrical device, wherein the battery cell comprises a housing assembly and an electrode assembly, wherein the housing assembly comprises a housing and a first electrode terminal arranged on the housing; the electrode assembly is accommodated in the housing, and the electrode assembly comprises a first electrode sheet and a second electrode sheet, wherein the first electrode sheet and the second electrode sheet each comprise a coating portion and a tab, wherein the coating portion comprises an active material layer, and the tab is not provided with an active material layer, wherein one of the first electrode sheet and the second electrode sheet is a positive electrode sheet and the other is a negative electrode sheet, wherein the active material layer in the positive electrode sheet comprises a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing phosphate with an olivine structure; the tab in the first electrode sheet is used to electrically connect the first electrode terminal and the coating portion in the first electrode sheet, and the area of ​​the projection surface of the first electrode terminal along its own thickness direction is 300 mm 2 Up to 500mm 2 This application can effectively improve the cycle performance and reliability of battery cells under fast charging conditions.

Description

[0001] This application claims priority to international application PCT / CN2024 / 109018, filed on July 31, 2024, entitled “Battery Cell, Battery Device, and Electrical Device,” the entire contents of which are incorporated herein by reference. Technical Field

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

[0003] Lithium-ion batteries, with their high capacity and long lifespan, are widely used in electronic devices such as mobile phones, laptops, electric bicycles, electric cars, electric aircraft, electric ships, and power tools. With the development of lithium-ion battery applications, higher requirements are being placed on lithium-ion battery performance, such as cycle performance and reliability. Summary of the Invention

[0004] The present application provides a battery cell, a battery device, and an electrical device, which can improve the cycle performance and reliability of the battery cell under fast charging conditions.

[0005] In the first aspect, the present application proposes a battery cell, which includes an electrode assembly and a shell assembly, the shell assembly including a shell and a first electrode terminal arranged on the shell; the electrode assembly is accommodated in the shell, the electrode assembly including a first electrode sheet and a second electrode sheet, the first electrode sheet and the second electrode sheet both including a coating portion and a tab, the coating portion including an active material layer, and the tab is not provided with an active material layer, wherein one of the first electrode sheet and the second electrode sheet is a positive electrode sheet and the other is a negative electrode sheet, the active material layer in the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a lithium phosphate containing an olivine structure; the tab in the first electrode sheet is used to electrically connect the first electrode terminal and the coating portion in the first electrode sheet, and the area of ​​the projection surface of the first electrode terminal along its own thickness direction is 200mm 2 Up to 600mm 2 , the charging time of the battery cell from 10% state of charge to 80% state of charge is 5min to 10.5min;

[0006] The first electrode terminal is used to connect to the first external busbar. The area of ​​the connection between the first electrode terminal and the first busbar is 60 mm. 2 Up to 150mm 2 .

[0007] Therefore, in the embodiment of the present application, on the one hand, the area of ​​the projection surface of the first electrode terminal is increased, and the area of ​​the projection surface of the first electrode terminal is greater than or equal to 200mm. 2, so that the contact area between the first electrode terminal and the first tab is not too small, the contact resistance between the first electrode terminal and the first tab can be reduced, the heat generated by the first electrode terminal is reduced, the temperature in the battery cell system is not too high, and the cycle stability and reliability of the active material are improved; even in the case of fast charging and high current density, the heat generated by the first electrode terminal is not too much, which is beneficial to improving the cycle stability of the active material; on the other hand, the positive electrode active material includes an olivine-structured lithium phosphate, which 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; and because the area of ​​the projected surface of the first electrode terminal is less than or equal to 600mm 2 The electrode terminals account for a relatively small proportion of the battery cell's weight, which helps improve the battery cell's weight energy density. The connection area between the first electrode terminal and the first busbar is within the aforementioned range. The connection area is relatively large, resulting in a larger weld area when laser welding is used. This reduces welding resistance, heat generation, and heat transfer into the battery cell, thereby improving the battery cell's cycling performance.

[0008] In some embodiments, the projection area of ​​the first electrode terminal is 300 mm 2 Up to 500mm 2 Therefore, the embodiments of the present application can improve the cycle performance and weight energy density of the battery cell.

[0009] In some embodiments, the tab in the first electrode sheet is directly connected to the first electrode terminal. This direct connection can shorten the current conduction path, reduce resistance in the current conduction path, reduce heat generation, and lower the temperature inside the battery cell, thereby further improving the cycle performance of the battery cell.

[0010] 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 also connected to the side of the housing facing the coating portion. This arrangement facilitates direct connection between the first electrode terminal and the first tab.

[0011] In some embodiments, the first electrode terminal includes a hollow supporting portion that accommodates at least a portion of a tab in the first electrode sheet, with an inner wall of the supporting portion connected to the tab in the first electrode sheet. Positioning at least a portion of the first tab in the supporting portion can reduce the internal space occupied by the first tab in the battery cell, increase the height of the first coating portion, and thus improve the volumetric energy density of the battery cell.

[0012] In some embodiments, the inner wall includes an end wall and a side wall, and the side wall is arranged around the end wall; the pole ear in the first pole piece is connected to the end wall; and / or the pole ear in the first pole piece is connected to the side wall.

[0013] In some embodiments, the battery cell includes a first adapter that connects the tab of the first electrode sheet to the first electrode terminal. The tab of the first electrode sheet is the first tab. The carrier portion not only accommodates the first tab but also enables connection to the first tab, thereby simplifying the structure of the first electrode terminal and facilitating its processing. It can also simplify the structure of the first tab, reduce redundancy, and lower the manufacturing cost of the first tab.

[0014] In some embodiments, the housing includes an electrode lead-out hole, and the first electrode terminal covers the electrode lead-out hole. The first electrode terminal is disposed on the side of the housing facing away from the coated portion. This structure ensures that the first electrode terminal substantially does not occupy space within the housing, thereby increasing space utilization within the housing, increasing the available space in the first coated portion, and improving the volumetric energy density of the battery cell.

[0015] 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. 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.

[0016] 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 tab is within the above range. 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.

[0017] In some embodiments, the first adapter is located between the first tab and the first electrode terminal; the projection of the connection area between the first adapter and the first tab along the thickness direction of the first electrode terminal is a first projection surface; the first electrode terminal is used to connect to an external first busbar, and the projection of the connection area between the first electrode terminal and the first busbar along the thickness direction of the first electrode terminal is a 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. This arrangement ensures a proper current conduction path between the first electrode terminal and the first tab, effectively reducing thermal resistance, reducing heat generation of the battery cell, and improving the cycle performance of the battery cell.

[0018] In some embodiments, the first adapter is a positive electrode adapter, and the thickness of the positive electrode adapter is 0.6 mm to 2.0 mm, and can be optionally 1.0 mm to 1.5 mm.

[0019] In some embodiments, the first adapter is a positive electrode adapter, and the cross-sectional area of ​​the positive electrode adapter perpendicular to its own thickness direction is 30 mm. 2 Up to 60mm 2 .

[0020] In some embodiments, the first adapter is a negative electrode adapter, and the thickness of the negative electrode adapter is 0.5 mm to 1.5 mm, or 0.6 mm to 1.2 mm.

[0021] In some embodiments, the first adapter is a negative electrode adapter, and the cross-sectional area of ​​the negative electrode adapter perpendicular to its own thickness direction is 24mm 2 Up to 60mm 2 .

[0022] In some embodiments, the tab in the first electrode piece is a positive electrode tab, and the cross-sectional area of ​​the positive electrode tab near the coating portion is 0.45 mm 2 to 1.0mm 2 .

[0023] In some embodiments, the tab in the first electrode piece is a negative electrode tab, and the cross-sectional area of ​​the negative electrode tab near the coating portion is 0.18 mm 2 to 1.0mm 2 .

[0024] In some embodiments, the electrode assembly is a laminated structure, the first electrode sheet and the second electrode sheet are stacked 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 area between the first electrode terminal and the tab of the first electrode sheet is 140 mm 2 Up to 420mm 2 , 210mm 2 Up to 350mm 2 .

[0025] In some embodiments, there are one or more first electrode terminals.

[0026] In some embodiments, the plurality of first electrode terminals are located on both sides of the coating portion.

[0027] In some embodiments, the plurality of first electrode terminals are located on the same side of the coating portion.

[0028] In some embodiments, the housing assembly further includes a second electrode terminal disposed on the housing, the tab in the second electrode piece is used to electrically connect the second electrode terminal and the coated portion in the second electrode piece, and the projection area of ​​the second electrode terminal along its own thickness direction is 200 mm. 2 Up to 600mm 2 When the area of ​​the projection surface 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.

[0029] In some embodiments, the housing includes a shell and an end cap. The shell is a rectangular parallelepiped structure that accommodates the electrode assembly and has an opening. The end cap covers the opening, and a first electrode terminal is disposed on the end cap. The projection of the first electrode terminal along its thickness direction in the thickness direction of the battery cell has a first dimension, and the dimension of the end cap in the thickness direction of the battery cell has 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 high area ratio of the first electrode terminal to the end cap facilitates improving the current carrying capacity of the first electrode terminal.

[0030] In some embodiments, the electrode assembly is a wound structure, the first electrode plate and the second electrode plate are wound in one direction, with the coated portion pointing in the direction of the end cover of the shell, and the size of the coated portion in the first electrode plate is 60 mm to 120 mm.

[0031] In some embodiments, the electrode assembly is a laminated structure, with the first electrode sheet and the second electrode sheet stacked along the thickness direction of the battery cell, with the coated portion pointing in the direction of the end cover of the shell, and the size of the coated portion in the first electrode sheet is 300 mm to 550 mm.

[0032] In some embodiments, the electrode assembly is a laminated structure, the first electrode sheet and the second electrode sheet are stacked along the thickness direction of the battery cell, and the projection surface of the first electrode terminal along its own thickness direction is a rectangle.

[0033] In some embodiments, the electrode assembly is a wound structure, the first electrode sheet and the second electrode sheet are wound in one direction, and the projection surface of the first electrode terminal along its own thickness direction is circular.

[0034] In some embodiments, the first electrode is a positive electrode.

[0035] In some embodiments, the first electrode is a negative electrode.

[0036] In some embodiments, a battery cell includes a housing assembly, an electrode assembly, and an electrolyte, wherein the electrode assembly and the electrolyte are contained in the housing assembly, and the housing assembly is provided with an electrode terminal; the electrode assembly includes a first electrode sheet, a second electrode sheet, and a separator located between the first electrode sheet and the second electrode sheet, wherein the first electrode sheet and the second electrode sheet each include a coating portion and an ear, wherein the coating portion is coated with an active material layer, and the ear is not coated with the active material layer; the polarities of the first electrode sheet and the second electrode sheet are opposite, and one of the first electrode sheet and the second electrode sheet is a positive electrode sheet, and the active material layer of the positive electrode sheet includes a positive active material layer. Materials, the positive electrode active material includes a lithium phosphate with an olivine structure; the electrode assembly is electrically connected to the electrode terminal through the electrode tab, wherein the coated portion of the first electrode sheet includes a first straight segment, the coated portion of the second electrode sheet includes a second straight segment, the first straight segment and the second straight segment are stacked along the thickness direction of the electrode assembly, the ratio of the number of the electrode tabs of the first electrode sheet to the number of the first straight segments of the first electrode sheet is 0.5 to 2, the electrolyte includes an organic solvent, 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%.

[0037] Therefore, the electrolyte in the embodiment of the present application includes the chain carboxylate solvent with the above-mentioned mass content. The conductivity of the solvent system is relatively high, which is conducive to the rapid migration of lithium ions and improves the rapid charging performance of the battery cell. Under the rapid charging system of the battery cell, the current density of the pole ear is usually large, resulting in increased heat generation, making the temperature in the battery cell high, which easily leads to the attenuation of the active material and the decomposition of the organic solvent in the electrolyte, thereby worsening the cycle. The positive electrode active material includes a lithium-containing phosphate with an olivine structure. The material has a stable structure during the charge and discharge process and is not prone to capacity attenuation, which is conducive to improving the cycle performance of the battery cell. At the same time, the first pole piece When the ratio of the number of tabs to the number of first straight sections of the first pole piece is within the above range, the current diversion capacity of the tabs can be increased, which can further improve the fast charging performance of the battery cell. However, since the connection area between the tabs and other components, such as the coating 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, and the stability of the electrolyte system and the stability of the active material are improved, which is beneficial to the improvement of the reliability of the battery cell and can improve the cycle performance. In addition, the tabs and the coating portion have more connection points, which can increase connection redundancy, such as welding redundancy, and effectively improve product yield. Therefore, the embodiments of the present application can improve the cycle performance and fast charging performance of the battery cell.

[0038] In some embodiments, the mass content of the chain carboxylate solvent in the electrolyte is 25% to 60%.

[0039] In some embodiments, the ratio of the number of tabs 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.

[0040] In some embodiments, the electrode assembly is a wound structure, the first electrode sheet and the second electrode sheet are wound in one direction, and the first electrode sheet has a plurality of electrode tabs.

[0041] In some embodiments, the ratio of the number of tabs 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.

[0042] 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 lug.

[0043] In some embodiments, the ratio of the number of tabs 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.

[0044] In some embodiments, the first electrode piece has multiple tabs, and the multiple tabs of the first electrode piece are arranged on the same side of the coating portion. The first tabs can be arranged on the same side of the first coating portion to increase welding redundancy and effectively improve product yield.

[0045] In some embodiments, the first pole piece has multiple tabs, each of which is disposed on either side of the coated portion. Embodiments of the present application can improve the cycling performance and fast charging performance of a battery cell. The first tab can share the current density of a single first pole piece. Especially when the first pole piece is relatively large, the current distribution within the first pole piece is more uniform, facilitating a uniform reaction and reducing impedance.

[0046] In some embodiments, the tab includes a tab body and multiple tab protrusions, the tab body is connected to the coating portion; the multiple 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.

[0047] Therefore, in the embodiment of the present application, the provision of multiple tab protrusions enables the first tab to have multiple connection sites. For example, when connecting the first tab to the first adapter, the multiple tab protrusions can be separately connected to different positions of the first adapter, such as by welding, which can increase the welding positions of the first tab and the first adapter, improve the welding yield, and enhance the stability of the connection between the two.

[0048] In some embodiments, the tab in the first pole piece is a positive electrode tab, and the thickness of the positive electrode tab is 10 μm to 20 μm.

[0049] When the thickness of the positive electrode tab is within the above range, the positive electrode tab has an excellent current carrying capacity, can reduce heat generation, and is beneficial to improving the fast charging performance of the battery cell.

[0050] In some embodiments, the tab in the first electrode sheet is a negative electrode tab, and the thickness of the negative electrode tab is 4 μm to 10 μm.

[0051] When the thickness of the negative electrode tab is within the above range, the negative electrode tab has a relatively excellent current carrying capacity, can reduce heat generation, and is beneficial to improving the fast charging performance of the battery cell.

[0052] In some embodiments, the conductivity of the electrolyte is 10.5 mS / cm to 20 mS / cm, optionally 15 mS / cm to 20 mS / cm.

[0053] When the conductivity of the electrolyte at room temperature is within the above range, the migration rate of lithium ions in the electrolyte is 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.

[0054] In some embodiments, the linear carboxylate solvent includes a compound represented by Formula I,

[0055] Formula I,

[0056] In Formula I,

[0057] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0058] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0059] Therefore, in the embodiment of the present application, the above-mentioned chain carboxylic acid ester solvent has a high conductivity, which is beneficial to improving the fast charging capability of the battery cell.

[0060] In some embodiments, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group.

[0061] In some embodiments, in some embodiments, R2 comprises C1 to C3 alkyl or C1 to C3 haloalkyl.

[0062] In some embodiments, the chain carboxylate solvent includes one or more compounds represented by formula I-1 to formula I-8.

[0063]

[0064] In some embodiments, the organic solvent further comprises a carbonate solvent, and the carbonate solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The use of the carbonate solvent and the chain carboxylate solvent in combination improves the conductivity of the electrolyte, facilitating the migration of lithium ions.

[0065] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0066] In some embodiments, the carbonate solvent content in the electrolyte is 20% to 80% by weight, and optionally 25.5% to 42.5% by weight. The above carbonate solvent content can further improve the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0067] In some embodiments, the electrolyte further includes additives, including one or more of carbonate additives, sulfur-containing additives, and lithium salt additives. These additives can improve the interfacial film properties on the positive and / or negative electrode sides, thereby enhancing the rapid charging performance of the battery cell and improving the cycling performance.

[0068] In some embodiments, the carbonate additive includes one or more of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0069] In some embodiments, the sulfur-containing additive includes one or more of vinyl sulfate DTD, vinyl disulfate 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, vinyl sulfite ES, and methylene disulfonate MMDS.

[0070] In some embodiments, the lithium salt additive includes one or more of lithium difluorophosphate LiPO2F2, lithium difluorooxalatoborate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bis(oxalatoborate) LiBOB.

[0071] In some embodiments, the additive content in the electrolyte is 1% to 10%, optionally 2% to 8%. The additive content above can effectively improve the interfacial film performance on the positive electrode side and / or the negative electrode side, thereby enhancing the fast charging performance of the battery cell and improving the cycling performance.

[0072] In some embodiments, the electrolyte further includes a lithium salt, including one or more of a fluorinated sulfonyl imide salt and lithium hexafluorophosphate (LiPF6). These lithium salts readily dissociate, facilitating rapid lithium ion migration. Furthermore, the electrolyte system is relatively stable and resistant to decomposition, enhancing the cycling performance of the battery cells.

[0073] In some embodiments, the fluorine-containing sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0074] 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 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.

[0075] In some embodiments, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate LiPF6 is 0.2 to 1.0, optionally 0.2 to 0.5.

[0076] In some embodiments, the electrolyte has a viscosity of 2.3 mPa·s to 3.5 mPa·s at room temperature. When the viscosity of the electrolyte is within this range, the migration rate of lithium ions in the electrolyte is 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.

[0077] In some embodiments, the electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature. When the electrolyte density is within this range, the migration rate of lithium ions in the electrolyte is 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.

[0078] In some embodiments, the olivine-structured lithium-containing phosphate includes phosphate particles and a coating layer, wherein the coating layer coats the phosphate particles and contains one or more elements selected from the group consisting of C, Fe, Ti, Zr, Hf, Ge, and Sn. The coating layer can enhance the conductivity of the olivine-structured lithium-containing phosphate, reduce the powder resistivity of the material, and facilitate the migration of lithium ions, thereby reducing heat generation in the battery cells.

[0079] 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 zCompounds 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, and Mg, Me comprises one or more of Mn, Fe, Co, and 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, and Ce, X comprises one or more of S, Si, Cl, B, C, and N, and Y comprises one or more of O and F. Olivine-structured lithium-containing phosphates have excellent cycle stability, which is beneficial for improving the cycle performance of battery cells.

[0080] In some embodiments, the coating layer comprises a Li 3-d Fe 2-d M2 d (PO x2 ) y2 The fast ion conductor M2 comprises one or more elements selected from Ti, Zr, Hf, Ge, and Sn, with 0≤d≤1, 0<x²<5, and 0<y²<4. Coating the phosphate particles with the fast ion conductor significantly increases the rate of lithium ion transport during multiple lithium insertions and extractions at the positive electrode, improving the ionic conductivity of the positive electrode active material, thereby increasing the specific capacity and, further, the energy density of the corresponding battery cell.

[0081] In some embodiments, the degree of graphitization of the positive electrode active material is 0.15 to 0.32, and optionally 0.19 to 0.26. When the degree of graphitization 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 generated by the positive electrode sheet, and thus reduce the heat generated by the battery cell.

[0082] In some embodiments, the mass content of carbon 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 5m 2 / g to 18m 2 / g; optional 7.5m 2 / g to 14m 2 / g.

[0083] Therefore, in the embodiment of the present application, the above-mentioned carbon element content combined with the material with the above-mentioned 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 conducive to the transmission of lithium ions at the phase interface.

[0084] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies the following conditions: 1µm ≤ Dv50 ≤ 2µm, and 0.4µm ≤ Dv10 ≤ 0.7µm. The relatively small particle size of the positive electrode active material shortens the lithium ion insertion and deintercalation pathway within the positive electrode active material, resulting in less heat generation. Furthermore, the particle size of the positive electrode active material is not excessively small, and agglomeration is substantially avoided during processing and preparation, resulting in stable performance of the positive electrode active material.

[0085] In some embodiments, the olivine-structured lithium-containing phosphate is in a granular form. The olivine-structured lithium-containing phosphate includes secondary particles formed by agglomeration of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm. The relatively small average particle size of the primary particles shortens the lithium ion insertion and deintercalation pathway in the positive electrode active material, resulting in less heat generation.

[0086] In some embodiments, the coated portion of the negative electrode sheet 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 92.0% to 94.5%.

[0087] When the graphitization degree of the graphite particles is within the above range, the graphite particles have excellent electrical conductivity, which can reduce the heat generation of the negative electrode sheet and the heat generation of the battery cell; and can improve the fast charging performance of the battery cell.

[0088] In some embodiments, the graphite particles include artificial graphite and amorphous carbon. The artificial graphite includes secondary particles formed by the aggregation of multiple primary particles. The amorphous carbon layer coats the surface of the artificial graphite. The amorphous carbon layer has a large number of end faces and defects, which increase the number of sites for lithium ion insertion and extraction. This improves the conductivity of the amorphous carbon layer, reduces the internal resistance of the negative electrode sheet, and reduces the heat generation of the battery cell.

[0089] In some embodiments, the mass content of the amorphous carbon layer is 2% to 5% based on the mass of the graphite particles. When the mass content of the amorphous carbon layer is within the above range, the internal resistance of the negative electrode plate can be further reduced, and the heat generation of the battery cell can be reduced.

[0090] In some embodiments, the coated portion of the negative electrode film layer in the negative electrode plate includes a first negative electrode film layer and a second negative electrode film layer, the first negative electrode film layer is arranged on the surface of the negative electrode current collecting portion, 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 away from the negative electrode current collecting portion, the carbon-based material in the second negative electrode film layer includes graphite particles, and 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.

[0091] Therefore, in the embodiment of the present application, there is a difference in the particle size of 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 the fast charging process, the overpotential of the second negative electrode film layer is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode film layer, while in the embodiment of the present application, the particle size of 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 plating on the surface of the negative electrode plate.

[0092] In some embodiments, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0093] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is more densely packed, thereby improving 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.

[0094] In some embodiments, the tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21g / cm 3 When the tap density of the carbon-based material in the first negative electrode film layer is within an appropriate range, the fast charging performance of the battery cell can be improved.

[0095] In some embodiments, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 Up to 1.25g / cm 3 When the tap density of the carbon-based material in the second negative electrode film layer is within an appropriate range, the energy density of the battery cell can be improved.

[0096] 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.

[0097] 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 transport can be reduced, thereby improving the fast charging performance of the battery cell.

[0098] In some embodiments, the first negative electrode film layer also includes a first lithium-containing binder, and the second negative electrode film layer also includes a second lithium-containing binder, and 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.

[0099] Therefore, in the embodiment 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 second lithium-containing binder provides the second negative electrode film layer with a relatively larger number of freely movable lithium ions, which can further improve the fast charging performance of the battery cell.

[0100] 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 rate of lithium ion insertion and extraction can be increased, thereby improving the fast charging performance of the battery cell.

[0101] In some embodiments, the mass content of lithium in the first lithium-containing binder is 3% to 10%, optionally 3% to 8%. When the mass content of lithium is within the above range, a relatively large number of lithium ions can be freely moved in the negative electrode film layer, which can further shorten the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increase the rate of lithium ion insertion and extraction, and improve the fast charging performance of the battery cell.

[0102] 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 in the second lithium-containing binder is within the above range, the rate of lithium ion insertion and extraction is increased, thereby improving the fast charging performance of the battery cell.

[0103] In some embodiments, the second lithium-containing binder has a lithium content of 3% to 10% by mass, and optionally 3% to 8% by mass. When the lithium content is within this range, a relatively large number of lithium ions can freely move within the negative electrode film layer, further shortening the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increasing the rate of lithium ion insertion and extraction, and improving the fast charging performance of the battery cell.

[0104] In some embodiments, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a hydroxyethyl acrylate monomer, and the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0105] Therefore, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, thereby improving the fast charging performance of the battery cell; and it is not easy to swell during the charging and discharging process, and the structure is stable, so that the cycle performance of the negative electrode film layer during the fast charging and discharging process is improved.

[0106] In some embodiments, the second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a hydroxyethyl acrylate monomer, and the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0107] Therefore, the lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, thereby improving the fast charging performance of the battery cell; and it is not easy to swell during the charging and discharging process, and the structure is stable, so that the cycle performance of the negative electrode film layer during the fast charging and discharging process is improved.

[0108] In some embodiments, the negative electrode active material further comprises a silicon-based material, wherein the silicon content of the silicon-based material is 0.3% to 10.0% by weight, based on the mass of the negative electrode active 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.

[0109] In some embodiments, the battery cell includes a separator, which includes a porous base film having a porosity of 20% to 70%. In the embodiments of the present application, when the porosity of the separator is within the above range, the migration ability of lithium ions in the separator can be improved, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation.

[0110] In some embodiments, the separator includes a porous base membrane having a porosity of 35% to 60%. In embodiments of the present application, when the porosity of the separator is within the above range, the migration of lithium ions through the separator can be enhanced, further reducing the internal resistance of the battery cell, thereby reducing heat generation.

[0111] In some embodiments, the base film has a thickness of 6 μm to 12 μm. When the base film thickness 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.

[0112] In some embodiments, the base film has a thickness of 6 μm to 9 μm. When the base film has a thickness 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.

[0113] In some embodiments, a separator includes a base film and a functional layer disposed on at least one side of the base film, the functional layer including a first functional layer and a second functional layer, the first functional layer being located on one side of the base film and including first inorganic particles, the second functional layer being located on the other side of the base film, the second functional layer including composite particles, the composite particles including second inorganic particles and a plurality of non-fluoropolymer particles, the second inorganic particles being attached to the surface of the non-fluoropolymer particles and / or dispersed within the non-fluoropolymer particles. The first and second functional layers have good heat resistance, thereby improving the heat resistance of the separator.

[0114] In some embodiments, the non-fluorinated polymer particles include acrylic copolymers, which have excellent bonding properties and high bonding stability with the base film.

[0115] 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 first inorganic particles can improve the heat resistance of the first functional layer.

[0116] 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 second inorganic particles can improve the heat resistance of the first functional layer.

[0117] 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.

[0118] 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, optionally 0.2 mm to 0.35 mm. When the housing thickness is within this range, the housing has high mechanical strength, which can improve the reliability and cycle performance of the battery cells. Furthermore, the housing occupies less space, leaving more space inside the housing, which helps to increase the energy density of the battery cells.

[0119] In some embodiments, the charging time of the battery cell from 10% state of charge to 80% state of charge is 5 minutes to 10.5 minutes. The charging speed of the battery cell is faster, which is more conducive to improving the fast charging capability.

[0120] In a second aspect, the present application proposes a battery device, which includes a plurality of battery cells according to any embodiment of the first aspect of the present application.

[0121] In some embodiments, the battery device can be charged from a 10% state of charge to an 80% state of charge in a time range of 5 to 10.5 minutes. The faster the charging speed of the battery device, the better the fast charging capability.

[0122] In a third aspect, the present application proposes an electrical device, which includes a battery device according to any embodiment of the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0123] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0124] Figure 1 A schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0125] Figure 2 An exploded schematic diagram of a battery cell provided in some embodiments of the present application;

[0126] Figure 3 A schematic structural diagram of an electrode assembly of a battery cell provided in some embodiments of the present application;

[0127] Figure 4 A schematic structural diagram of a first pole piece of a battery cell provided in some embodiments of the present application;

[0128] Figure 5 A schematic structural diagram of a second pole piece of a battery cell provided in some embodiments of the present application;

[0129] Figure 6 A schematic structural diagram of an electrode assembly of a battery cell provided in other embodiments of the present application;

[0130] Figure 7 A schematic structural diagram of a first pole piece of a battery cell provided in other embodiments of the present application;

[0131] Figure 8 A schematic structural diagram of a second pole piece of a battery cell provided in other embodiments of the present application;

[0132] Figure 9 A schematic cross-sectional structure diagram of a battery cell provided in some embodiments of the present application;

[0133] Figure 10 for Figure 9 The enlarged structural diagram of the battery cell shown at position I;

[0134] Figure 11 Schematic diagram of the cross-sectional structure of a battery cell provided in some other embodiments of the present application;

[0135] Figure 12 for Figure 11 The enlarged structural diagram of the battery cell shown at II;

[0136] Figure 13 Schematic diagram of an explosion of a battery cell provided in some other embodiments of the present application;

[0137] Figure 14 A schematic top view of a battery cell provided in some other embodiments of the present application;

[0138] Figure 15 A schematic structural diagram of an electrode assembly of a battery cell provided in some further embodiments of the present application;

[0139] Figure 16 A schematic structural diagram of an electrode assembly of a battery cell provided in some further embodiments of the present application;

[0140] Figure 17 A schematic structural diagram of an electrode assembly of a battery cell provided in some further embodiments of the present application;

[0141] Figure 18 A schematic structural diagram of an electrode assembly of a battery cell provided in some further embodiments of the present application;

[0142] Figure 19 Schematic diagram of the expansion of the first pole piece of the electrode assembly in the battery cell provided in other embodiments of the present application;

[0143] Figure 20 Schematic diagram of the expansion of the first pole piece of the electrode assembly in the battery cell provided in other embodiments of the present application;

[0144] Figure 21 A schematic structural diagram of a second pole piece of a battery cell provided in other embodiments of the present application;

[0145] Figure 22 A schematic diagram of the expanded structure of the first pole piece of a battery cell provided in other embodiments of the present application;

[0146] Figure 23 for Figure 22 The schematic diagram of the partial enlarged structure of the first pole piece at position A is shown;

[0147] Figure 24 A schematic diagram of the structure of a battery module provided in some embodiments of the present application;

[0148] Figure 25A schematic diagram of the structure of a battery pack provided in some embodiments of the present application;

[0149] Figure 26 It is a schematic diagram of the structure of an electrical device provided in some embodiments of the present application.

[0150] The drawings are not necessarily drawn to scale.

[0151] The following are the descriptions of the reference numerals:

[0152] 1. Electrical device; 2. Battery pack; 3. Controller; 4. Motor; 5. Box; 5a. First box portion; 5b. Second box portion; 5c. Accommodation space;

[0153] 6. Battery module; 61. First busbar; 62. Second busbar;

[0154] 7. Battery cells;

[0155] 10. Electrode assembly;

[0156] 111, first tab; 1111, tab body; 1112, tab protrusion; 111a, first gathered portion; 111b, second gathered portion;

[0157] 112, second tab;

[0158] 13. First pole piece; 131. First straight section; 132. First bent section; 130. First coating portion;

[0159] 14. Second pole piece; 141. Second straight section; 142. Second bent section; 140. Second coating portion;

[0160] 15. Isolation film;

[0161] 200, housing assembly;

[0162] 20. Housing; 201. Electrode lead-out hole; 21. Shell; 22. End cap;

[0163] 31. First electrode terminal; 311. Carrying portion; 3110. Inner wall; 3111. End wall; 3112. Side wall;

[0164] 33. Fixing parts;

[0165] 32. a second electrode terminal;

[0166] 41. First adapter; 42. Second adapter. DETAILED DESCRIPTION

[0167] Below, the embodiments of the battery cells, battery devices, and electrical devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be 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 description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0168] " Range " disclosed in this application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. 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 can all be expected: 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 abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0169] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0170] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0171] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0172] Due to the existence of resistance in the current conduction path, battery cells will inevitably generate heat during the cyclic charge and discharge process. For example, the electrode terminals are used to conduct the electrode assembly and the external circuit, and the electrode terminals will generate heat. This heat diffuses into the interior of the battery cell, causing the temperature inside the battery cell to increase, making the active material more susceptible to high-temperature decay, shortening the cycle life of the battery cell and deteriorating its reliability.

[0173] In view of this, the embodiment of the present application rationally designs the system of the battery cell. By adjusting the area of ​​the first electrode terminal in the battery cell so that the area of ​​the first electrode terminal is relatively large, the contact resistance can be effectively reduced, the temperature of the battery cell can be lowered, and the cycle stability of the active material can be improved, thereby improving the cycle life and reliability of the battery cell.

[0174] battery cells

[0175] In a first aspect, embodiments of the present application provide a battery cell.

[0176] like Figures 1 to 3 As shown, the battery cell 7 includes a shell assembly 200 and an electrode assembly 10, the shell assembly 200 includes a shell 20 and a first electrode terminal 31 provided on the shell 20; the electrode assembly 10 is accommodated in the shell 20, and the electrode assembly 10 includes a first electrode sheet 13 and a second electrode sheet 14, the first electrode sheet 13 and the second electrode sheet 14 both include a coating portion and a tab, the coating portion includes an active material layer, and the tab is not provided with an active material layer, wherein one of the first electrode sheet 13 and the second electrode sheet 14 is a positive electrode sheet and the other is a negative electrode sheet, the active material layer in the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a lithium phosphate containing an olivine structure; the tab in the first electrode sheet 13 is used to electrically connect the first electrode terminal 31 and the coating portion in the first electrode sheet 13, and the area of ​​the projection surface of the first electrode terminal 31 along its own thickness direction is 200mm 2 Up to 600mm 2 .

[0177] The housing assembly 200 has a storage space for accommodating 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 shell 21, the shell 21 has an opening, the end cap 22 covers the opening, and the first electrode terminal 31 is provided on the end cap 22. The shape of the shell 21 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, a shell 21 with a cylindrical structure can be selected; if the electrode assembly 10 has a rectangular structure, a shell 21 with a rectangular structure can be selected. Optionally, both the electrode assembly 10 and the shell 21 have a rectangular structure. The thickness direction of the first electrode terminal 31 is parallel to the thickness direction of the end cap 22.

[0178] The battery cell 7 is a physical structure with length, thickness and height. In the embodiment of the present application, the direction from the coating portion to the end cover 22 of the outer shell 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 coating portion to the end cover 22 of the outer shell 20. Figure 2 The Y direction shown in FIG. 7 represents the thickness direction of the battery cell 7, which is also parallel to the thickness direction of the electrode assembly 10. Figure 2 The Z direction shown indicates a direction from the coating portion toward the end cap 22 of the outer case 20 , and 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 W direction shown indicates a first direction, and the W direction, the Y direction, and the Z direction are perpendicular to each other.

[0179] The housing 21 of the battery cell 7 can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer shell 20 of the battery cell 7 can also be a soft package, such as a pouch-type soft package. The soft package can be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0180] In some embodiments, the base material of the housing 21 includes steel, which has high mechanical strength and is not easily deformed, thereby improving the reliability of the battery cell 7. In the embodiment of the present application, the base material refers to the material with the highest proportion in the housing 21.

[0181] When the shell 21 is a rectangular structure, the shell 21 includes two first shell portions 211 and two second shell portions 212. The two first shell portions 211 are arranged opposite to each other, and the two second shell portions 212 are arranged opposite to each other. The first shell portion 211 is connected between the two second shell portions 212, and the area of ​​the first shell portion 211 is larger than the area of ​​the second shell portion 212.

[0182] In some embodiments, the base material of the housing 21 includes steel, which has high mechanical strength and is not easily deformed, thereby improving the reliability and cycle performance of the battery cell. In the embodiments of this application, the base material refers to the material with the highest proportion in the housing 21.

[0183] Optionally, when the base material of the shell 21 includes steel, the thickness of the shell 21 is 0.1mm to 0.5mm, and optionally 0.2mm to 0.35mm. Exemplarily, the thickness of the shell 21 is 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, or a range consisting of any two of the above values. When the thickness of the shell 21 is within the above range, the mechanical strength of the shell 21 is higher, which can improve the reliability of the battery cell 7; and the shell 21 occupies less space, and the internal space of the shell 21 is more, which is conducive to improving the energy density of the battery cell 7.

[0184] In some embodiments, the base material of the housing 21 includes aluminum.

[0185] Optionally, when the base material of the shell includes aluminum, the thickness of the first shell portion 211 is less than or equal to the thickness of the second shell portion 212 .

[0186] Exemplarily, the thickness of the first shell portion 211 is 0.1 mm to 1.0 mm, optionally 0.3 mm to 0.8 mm. Exemplarily, the thickness of the first shell 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 consisting of any two of the above values.

[0187] The first shell portion 211 is thinner, so that the housing 21 occupies less space, which can further improve the energy density of the battery cell 7 .

[0188] Exemplarily, the thickness of the second shell portion 212 is 0.1 mm to 1.0 mm, and may be 0.5 mm to 0.8 mm. Exemplarily, the thickness of the second shell 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 consisting of any two of the above values.

[0189] The second shell portion 212 is thicker, which can improve the overall mechanical strength of the housing 21 and reduce the risk of deformation of the housing 21 .

[0190] In the embodiment of the present application, the projection surface of the first electrode terminal 31 along its own thickness direction refers to the thickness direction of the first electrode terminal 31 as the normal of the projection surface, that is, the projection surface is perpendicular to the thickness direction of the first electrode terminal 31, and the projection surface can represent the flow area of ​​the first electrode terminal 31.

[0191] The number of the first electrode terminals 31 can be one or more. When the number of the first electrode terminals 31 is multiple, the multiple first electrode terminals 31 can be used to connect the pole ears of the first electrode piece 13. The multiple first electrode terminals 31 enable the first electrode terminal 31 and the pole ears of the first electrode piece 13 to include multiple connection areas. Specifically, the first electrode piece 13 can be divided into multiple groups and welded to the corresponding first electrode terminals 31 respectively, thereby reducing the connection area of ​​a single first electrode terminal 31, such as the welding area, which can reduce the impedance of the connection and reduce the heat generation.

[0192] Multiple first electrode terminals 31 can be located on the same side of the coated portion or on both sides of the coated portion. When located on both sides of the coated portion, for example, on both sides of the coated portion along the Z direction, the current distribution behavior inside the electrode can be improved, the current distribution can be uniformed, and it is beneficial to further reduce the impedance; especially the impedance during fast charging can be effectively reduced.

[0193] The coated portion is a portion coated with active material, which can perform deintercalation of active ions during the charge and discharge process of the battery cell 7. The coated portion may include a current collecting portion and an active material layer arranged on at least one side of the current collecting portion; the tab is used to electrically connect the coated portion and the electrode terminal (for example, the first electrode terminal 31), and no active material is coated thereon.

[0194] In the embodiment of the present application, on the one hand, the projection area of ​​the first electrode terminal 31 is increased, and the projection area of ​​the first electrode terminal 31 is greater than or equal to 200mm 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, thereby improving the cycle stability of the active material; even in the case of fast charging with a high current density, the heat generated by the first electrode terminal 31 will not be too much, which is beneficial to improving the cycle stability and reliability of the active material; on the other hand, the positive electrode active material includes an olivine-structured lithium-containing phosphate, which 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 projected area of ​​the first electrode terminal 31 is less than or equal to 600mm 2 The electrode terminals account for a relatively small proportion of the weight of the battery cell 7 , which is beneficial to improving the weight energy density of the battery cell 7 .

[0195] Therefore, the embodiment of the present application can improve the cycle performance and weight energy density of the battery cell 7.

[0196] In the embodiment of the present application, the projection area of ​​the first electrode terminal 31 along its own thickness direction is 200 mm 2 Up to 600mm 2 , 300mm is optional 2 Up to 500mm 2 For example, the projection area of ​​the first electrode terminal 31 along the thickness direction of the end cover 22 is 200 mm. 2 , 220mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 420mm 2 , 450mm 2 , 480mm 2 , 500mm 2 , 520mm 2 , 550mm 2 , 580mm 2 , 600mm 2 Or a range consisting of any two of the above values.

[0197] When the area of ​​the projection surface 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.

[0198] In some embodiments, the housing assembly 200 further includes a second electrode terminal 32 disposed on the housing 20, and the tab in the second electrode piece 14 is used to electrically connect the coated portion in the second electrode piece 14 to the second electrode terminal 32. Optionally, the second electrode terminal 32 can be disposed on the end cap 22.

[0199] Optionally, the projection area of ​​the second electrode terminal 32 along its own thickness direction is 200 mm 2 Up to 600mm 2 , 300mm is optional 2 Up to 500mm 2 For example, the projection area of ​​the second electrode terminal 32 along its own thickness direction is 200 mm. 2 , 220mm 2 , 250mm 2 , 280mm 2, 300mm 2 , 320mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 420mm 2 , 450mm 2 , 480mm 2 , 500mm 2 , 520mm 2 , 550mm 2 , 580mm 2 , 600mm 2 Or a range consisting of any two of the above values.

[0200] When the area of ​​the projection surface of the second electrode terminal 32 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.

[0201] The first electrode sheet 13 and the second electrode sheet 14 have opposite polarities. When the first electrode sheet 13 is a positive electrode sheet, the second electrode sheet 14 is a negative electrode sheet, the first electrode terminal 31 is a positive electrode terminal, and the second electrode terminal 32 is a negative electrode terminal. Alternatively, when the first electrode sheet 13 is a negative electrode sheet, the second electrode sheet 14 is a positive electrode sheet, the first electrode terminal 31 is a negative electrode terminal, and the second electrode terminal 32 is a positive electrode terminal. The coated portion of the positive electrode sheet corresponds to the positive electrode coating portion, the tab corresponds to the positive electrode tab, and the active material layer corresponds to the positive electrode film layer containing positive electrode active material. The positive electrode coating portion includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector. The coated portion of the negative electrode sheet corresponds to the negative electrode coating portion, the tab corresponds to the negative electrode tab, and the active material layer corresponds to the negative electrode film layer containing negative electrode active material. The negative electrode coating portion includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector.

[0202] For example, the projection area of ​​the positive terminal along its thickness direction is 200 mm 2 Up to 600mm 2 Or the negative terminal's projection along its thickness is 200mm 2 Up to 600mm 2 Or the projection area of ​​the positive terminal along its own thickness direction is 200mm 2 Up to 600mm 2 ; and the negative terminal along its own thickness direction projection area is 200mm 2 Up to 600mm 2 .

[0203] The electrode assembly 10 may be a wound structure or a laminated structure. Optionally, the electrode assembly 10 further includes a separator 15 .

[0204] In order to more clearly illustrate this application, the electrode tab in the first pole piece 13 is defined as the first pole tab 111, and the coated portion in the first pole piece 13 is defined as the first coating portion 130; the electrode tab in the second pole piece 14 is defined as the second pole tab 112, and the coated portion in the second pole piece 14 is defined as the second coating portion 140.

[0205] like Figures 3 to 5 As shown, when the electrode assembly 10 is a wound structure, the first electrode sheet 13, the separator 15 and the second electrode sheet 14 are wound in one direction. Figure 4 Schematic diagram of the expansion of the first electrode piece 13 is shown, and the first electrode tab 111 is provided on one side or both sides of the first coating portion 130, and one side may be selected; Figure 5 The expanded schematic diagram of the second electrode piece 14 is shown. The second electrode tab 112 is provided on one side or both sides of the second coating portion 140 , and may be provided on one side.

[0206] In some embodiments, the dimension of the first electrode tab 111 on the side facing the first coating portion 130 along the first direction W is 30 mm to 50 mm, for example, 30 mm, 32 mm, 35 mm, 38 mm, 40 mm, 42 mm, 45 mm, 48 mm, 50 mm, or a range consisting of any two of the above values. Figure 4 P1 shown represents the dimension of the first electrode tab 111 facing the first coating portion 130 along the first direction W. When the dimension of the first electrode tab 111 meets the above range, the first electrode tab 111 has good current flow capacity, which is conducive to improving heat dissipation effect.

[0207] When the first electrode tab 111 is a positive electrode tab, for example, when the material of the positive electrode tab is aluminum, the cross-sectional area of ​​the first electrode tab 111 facing the first coating portion 130 is greater than or equal to 0.45 mm 2 The upper limit depends on the thickness of the first tab 111, and the cross section is parallel to the thickness direction of the positive tab. For example, the cross section area of ​​the first tab 111 is 0.45mm 2 , 0.48mm 2 , 0.50mm 2 , 0.52mm 2 , 0.55mm 2 , 0.58mm 2 , 0.60mm 2 , 0.65mm 2 , 0.70mm 2 , 0.75mm 2 , 0.80mm 2 , 0.85mm 2 , 0.90mm 2 , 0.95mm 2 , 1.0mm2 When the cross-sectional area of ​​the first tab 111 is within the above range, the first tab 111 has a stronger current-carrying capacity and is also conducive to rapid heat dissipation.

[0208] When the first electrode tab 111 is a negative electrode tab, for example, when the negative electrode tab is made of copper, the cross-sectional area of ​​the first electrode tab 111 facing the first coating portion 130 is greater than or equal to 0.18 mm 2 The upper limit depends on the thickness of the first tab 111, and the cross section is parallel to the thickness direction of the positive tab. For example, the cross section area of ​​the first tab 111 is 0.18mm 2 , 0.20mm 2 , 0.22mm 2 , 0.25mm 2 , 0.28mm 2 , 0.30mm 2 , 0.32mm 2 , 0.35mm 2 , 0.38mm 2 , 0.40mm 2 , 0.42mm 2 , 0.45mm 2 , 0.48mm 2 , 0.50mm 2 , 0.52mm 2 , 0.55mm 2 , 0.58mm 2 , 0.60mm 2 , 0.65mm 2 , 0.70mm 2 , 0.75mm 2 , 0.80mm 2 , 0.85mm 2 , 0.90mm 2 , 0.95mm 2 , 1.0mm 2 When the cross-sectional area of ​​the first tab 111 is within the above range, the first tab 111 has a stronger current-carrying capacity and is also conducive to rapid heat dissipation.

[0209] In some embodiments, the first coating portion 130 has a dimension of 60 mm to 120 mm in the direction from the coating portion toward the end cap 22 of the housing 20, i.e., in the Z direction of the battery cell 7. For example, the dimension of the first coating portion 130 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 consisting of any two of the above values. Figure 4P3 shown in FIG. 1 represents a dimension of the first coating portion 130 along the Z direction.

[0210] The height and length dimensions of the battery cell 7 are limited, and the energy density of the battery cell 7 can be improved by increasing the thickness dimension; and the thickness direction of the battery cell 7 is parallel to the width direction of the end cover 22. A thicker battery cell 7 is more conducive to setting a wider end cover 22, which is conducive to setting a large-sized first electrode terminal 31, thereby improving the overcurrent density of the first electrode terminal 31.

[0211] In some embodiments, the dimension of the side of the second electrode tab 112 facing the second coating portion 140 along the first direction W is 30 mm to 50 mm, for example, 30 mm, 32 mm, 35 mm, 38 mm, 40 mm, 42 mm, 45 mm, 48 mm, 50 mm, or a range consisting of any two of the above values. Figure 5 P2 shown represents the dimension of the second electrode tab 112 facing the second coating portion 140 along the first direction W. When the dimension of the second electrode tab 112 meets the above range, the second electrode tab 112 has good current flow capacity, which is conducive to improving heat dissipation effect.

[0212] In some embodiments, the second coating portion 140 has a dimension of 60 mm to 120 mm in the direction from the coating portion toward the end cap 22 of the housing 20, i.e., in the Z direction of the battery cell 7. For example, 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 consisting of any two of the foregoing values. Figure 5 P4 shown in FIG. 1 represents a dimension of the second coating portion 140 along the Z direction.

[0213] The height and length of the battery cell 7 are limited, and the energy density of the battery cell 7 can be improved by increasing the thickness. The thickness direction of the battery cell 7 is parallel to the width direction of the end cover 22. A thicker battery cell 7 is more conducive to setting a wider end cover 22, which is conducive to setting a large-sized second electrode terminal 32 and improving the overcurrent density of the second electrode terminal 32.

[0214] like Figures 6 to 8 As shown, when the electrode assembly 10 is a laminated structure, the first pole piece 13 is at least one piece, and can be optionally at least two pieces; the second pole piece 14 is at least one piece, and can be optionally at least two pieces; the isolation membrane 15 is at least one piece, and can be optionally at least two pieces, and the first pole piece 13, the isolation membrane 15 and the second pole piece 14 are stacked along the thickness direction Y of the battery cell 7. Figure 7 Schematic diagram of the structure of the first electrode piece 13 is shown, and the first electrode tab 111 is provided on one side or both sides of the first coating portion 130, and both sides may be selected; Figure 8 A schematic structural diagram of the second electrode piece 14 is shown. The second electrode tab 112 is provided on one side or both sides of the second coating portion 140 , optionally both sides.

[0215] In some embodiments, the dimension of the side of the first electrode tab 111 facing the first coating portion 130 along the first direction W is 30 mm to 80 mm, for example, 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 consisting of any two of the above values. Figure 7 P1 shown represents the dimension of the first electrode tab 111 facing the first coating portion 130 along the first direction W. When the dimension of the first electrode tab 111 meets the above range, the first electrode tab 111 has good current flow capacity, which is conducive to improving heat dissipation effect.

[0216] When the first electrode tab 111 is a positive electrode tab, for example, when the material of the positive electrode tab is aluminum, the cross-sectional area of ​​the first electrode tab 111 facing the first coating portion 130 is greater than or equal to 0.45 mm 2 The upper limit depends on the thickness of the first tab 111, and the cross section is parallel to the thickness direction of the positive tab. For example, the cross section area of ​​the first tab 111 is 0.45mm 2 , 0.48mm 2 , 0.50mm 2 , 0.52mm 2 , 0.55mm 2 , 0.58mm 2 , 0.60mm 2 , 0.65mm 2 , 0.70mm 2 , 0.75mm 2 , 0.80mm 2 , 0.85mm 2 , 0.90mm 2 , 0.95mm 2 , 1.0mm 2 When the cross-sectional area of ​​the first tab 111 is within the above range, the first tab 111 has a stronger current-carrying capacity and is also conducive to rapid heat dissipation.

[0217] When the first electrode tab 111 is a negative electrode tab, for example, when the negative electrode tab is made of copper, the cross-sectional area of ​​the first electrode tab 111 facing the first coating portion 130 is greater than or equal to 0.18 mm 2 The upper limit depends on the thickness of the first tab 111. The cross section is parallel to the thickness direction of the tab. For example, the cross section area of ​​the first tab 111 is 0.18mm 2, 0.20mm 2 , 0.22mm 2 , 0.25mm 2 , 0.28mm 2 , 0.30mm 2 , 0.32mm 2 , 0.35mm 2 , 0.38mm 2 , 0.40mm 2 , 0.42mm 2 , 0.45mm 2 , 0.48mm 2 , 0.50mm 2 , 0.52mm 2 , 0.55mm 2 , 0.58mm 2 , 0.60mm 2 , 0.65mm 2 , 0.70mm 2 , 0.75mm 2 , 0.80mm 2 , 0.85mm 2 , 0.90mm 2 , 0.95mm 2 , 1.0mm 2 When the cross-sectional area of ​​the first tab 111 is within the above range, the first tab 111 has a stronger current-carrying capacity and is also conducive to rapid heat dissipation.

[0218] In some embodiments, the first coating portion 130 has a dimension of 300 mm to 550 mm in the direction from the coating portion toward the end cap 22 of the housing 20, i.e., in the Z direction of the battery cell 7. For example, the dimension 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 consisting of any two of the foregoing values. Figure 7 P3 shown in FIG. 1 represents a dimension of the first coating portion 130 along the Z direction.

[0219] The height and length dimensions of the battery cell 7 are limited, and the energy density of the battery cell 7 can be improved by increasing the thickness dimension; and the thickness direction of the battery cell 7 is parallel to the width direction of the end cover 22. A thicker battery cell 7 is more conducive to setting a wider end cover 22, which is conducive to setting a large-sized first electrode terminal 31, thereby improving the overcurrent density of the first electrode terminal 31.

[0220] In some embodiments, the dimension of the side of the second electrode tab 112 facing the second coating portion 140 along the first direction W is 30 mm to 80 mm, for example, 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 consisting of any two of the above values. Figure 8 P2 shown represents the dimension of the second electrode tab 112 facing the second coating portion 140 along the first direction W. When the dimension of the second electrode tab 112 meets the above range, the second electrode tab 112 has good current flow capacity, which is conducive to improving heat dissipation effect.

[0221] In some embodiments, the size of the second coating portion 140 in the direction from the coating portion toward the end cap 22 of the housing 20, i.e., the Z direction of the battery cell 7, is 300 mm to 550 mm. For example, the size of the second coating portion 140 in the Z direction is 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, or a range consisting of any two of the above values. Figure 8 P4 shown in FIG. 1 represents a dimension of the second coating portion 140 along the Z direction.

[0222] The height and length of the battery cell 7 are limited, and the energy density of the battery cell 7 can be improved by increasing the thickness. The thickness direction of the battery cell 7 is parallel to the width direction of the end cover 22. A thicker battery cell 7 is more conducive to setting a wider end cover 22, which is conducive to setting a large-sized second electrode terminal 32 and improving the overcurrent density of the second electrode terminal 32.

[0223] The first electrode tab 111 and the first electrode terminal 31 can be directly or indirectly connected. When indirectly connected, the battery cell may further include a first adapter, which is located between the first electrode tab 111 and the first electrode terminal and is used to electrically connect the first electrode tab 111 and the first electrode terminal.

[0224] Next, a case where the first tab is directly connected to the first electrode terminal will be described.

[0225] like Figure 9 and Figure 10As shown, when the first tab 111 is directly connected to the first electrode terminal 31, this direct connection can shorten the current conduction path, reduce resistance along the current conduction path, reduce heat generation, and lower the temperature within the battery cell 7, thereby further improving the cycle performance of the battery cell 7. The first tab 111 and the first electrode terminal 31 can be electrically connected by welding, with the electrical connection location being the welding point between the first tab 111 and the first electrode terminal 31. The welding method is not limited, and can include, for example, laser welding or ultrasonic welding of the tabs into a single entity followed by laser welding. Depending on factors such as the location, angle, or structure of the weld, vertical welding, angled welding, lap welding, or edge sealing welding can be used. The first tab 111 and the first electrode terminal 31 can also be electrically connected using other methods, such as conductive nails or conductive adhesive.

[0226] In some embodiments, the housing 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 housing 20 facing the first coating portion 130 in the electrode assembly 10. Optionally, the end cap 22 includes an 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 facilitates direct connection between the first electrode terminal 31 and the first tab 111.

[0227] The first electrode terminal 31 can be a solid structure or a hollow structure, with the latter being optional. When the first electrode terminal 31 is a hollow structure, it occupies less weight, which helps improve the weight energy density of the battery cell. The first electrode tab 111 can be partially or completely contained within the hollow structure, saving space in the height of the battery cell 7 and helping improve the volumetric energy density of the battery cell 7. For example, when the first electrode terminal 31 is a hollow structure, the first electrode terminal 31 includes a hollow support portion 311. At least a portion of the first electrode tab 111 is disposed within the support portion 311 and connected to the inner wall 3110 of the support portion 311. In other examples, a portion of the first pole tab 111 is disposed within the carrying portion 311, but may not be connected to the inner wall 3110 of the carrying portion 311. For example, a portion of the first pole tab 111 is accommodated within the carrying portion 311, and the other portion is located outside the carrying 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 pole tab 111 and the first electrode terminal 31 is located on the surface of the first electrode terminal 31 facing the first coating portion 130.

[0228] The carrier portion 311 is a solid structure having a storage space and including an inner wall 3110. Disposing at least a portion of the first electrode tab 111 within the carrier portion 311 can reduce the internal space occupied by the first electrode tab 111 within the battery cell 7, increase the height of the first coating portion 130, and improve the volumetric energy density of the battery cell 7. Disposing at least a portion of the first electrode tab 111 within the carrier portion 311 means that the first electrode tab 111 can be fully accommodated within the storage space or partially accommodated within the carrier portion 311. The first pole lug 111 is mechanically connected to the inner wall 3110 of the supporting portion 311, which can realize the electrical connection between the first pole lug 111 and the first electrode terminal 31. Since the first pole lug 111 is accommodated in the supporting 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. Setting at least a portion of the first pole lug 111 in the supporting portion 311 can also reduce the internal space of the battery cell 7 occupied by the first pole lug 111, and can improve the volume energy density of the battery cell 7.

[0229] 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 along the thickness direction away from the first coating portion 130, or the end wall 3111 is connected to the side of the side wall 3112 along the thickness direction facing the first coating portion 130; 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.

[0230] The connection position between the first electrode tab 111 and the first electrode terminal 31 can be located on the end wall 3111, or on the side wall 3112, or on 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 supporting portion 311 not only has the function of accommodating the first electrode tab 111, but also can achieve connection with the first electrode tab 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 electrode tab 111, reduce the redundancy of the first electrode tab 111, and reduce the manufacturing cost of the first electrode tab 111.

[0231] There are multiple first electrode tabs 111, and the multiple first electrode tabs 111 are connected to the first coating part 130. The first electrode tabs 111 can be formed by die-cutting a structure that is not coated with active material. The multiple first electrode tabs 111 converge near the first coating part 130 to form a first gathered part 111a. The multiple first electrode tabs 111 are close to each other but not connected. It can be understood that there is a gap between the adjacent multiple first electrode tabs 111; the multiple first electrode tabs 111 converge and connect to form a second gathered part 111b away from the first coating part 130. The interlayer gap between the multiple first electrode tabs 111 is reduced, so that the fluffy multiple first electrode tabs 111 are connected into an integrated structure, for example, by welding or the like, or by conductive glue or the like to form an integrated structure, wherein the first gathered part 111a connects the second gathered part 111b and the first coating part 130.

[0232] Multiple first electrode tabs 111 converge near the first coating portion 130 to form a first gathered portion 111a, and multiple first electrode tabs 111 converge and connect to form a second gathered portion 111b away from the first coating portion 130, which means that the first gathered portion 111a and the second gathered portion 111b are arranged in sequence along the extension direction of the electrode tab sheet.

[0233] In the above technical solution, at least a portion of the second gathered portion 111b is accommodated within the supporting portion 311, facilitating the connection between the first electrode tab 111 and the first electrode terminal 31. This allows for full utilization of the space within the first electrode terminal 31, reduces the space occupied by the first electrode tab 111 within the housing 20, accommodates a larger first coating portion 130, and improves the volumetric energy density of the battery cell 7. The second gathered portion 111b may be connected to the end wall 3111 and / or connected to the side wall 3112.

[0234] Furthermore, at least a portion of the first folded portion 111 a is accommodated within the bearing portion 311 , which can further reduce the space occupied by the first electrode tab 111 within the housing 20 , accommodate a larger first coating portion 130 , and improve the volume energy density of the battery cell 7 .

[0235] Next, a case where the first tab is indirectly connected to the first electrode terminal will be described.

[0236] like Figures 11 to 13 As shown, when the first tab 111 is indirectly connected to the first electrode terminal 31 , the battery cell 7 may further include a first adapter 41 , which is located between the first tab 111 and the first electrode terminal 31 and is used to electrically connect the first tab 111 and the first electrode terminal 31 .

[0237] In some embodiments, the housing 20 includes an electrode lead-out hole 201, and the first electrode terminal 31 covers the electrode lead-out hole 201. The first electrode terminal 31 is connected to the side of the housing 20 facing away from the coating portion. Optionally, the end cap 22 includes an electrode lead-out hole 201, and the first electrode terminal 31 covers the electrode lead-out hole 201. The first electrode terminal 31 is also connected to the side of the end cap 22 facing away from the first coating portion 130. This structural form ensures that the first electrode terminal 31 substantially does not occupy space within the housing 21, which helps to increase space utilization within the housing 21, increase the available space in the first coating portion 130, and improve the volumetric energy density of the battery cell 7. Specifically, the first electrode terminal 31 is connected to the side of the end cap 22 facing away from the first coating portion 130. Optionally, the first electrode terminal 31 can be connected to the end cap 22 via a fixing member 33. For example, the fixing member 33 can be an insulating fixing member disposed on the periphery of the first electrode terminal 31 and located within 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 increase the connection area between the first electrode terminal 31 and the first electrode tab 111, increase the flow capacity, reduce the heat generation in the battery cell 7, and improve the cycle performance of the battery cell 7.

[0238] In some embodiments, the area of ​​the connection region between the first adapter 41 and the first electrode terminal 31 is 35 mm. 2 Up to 50mm 2 , for example 35mm 2 , 38mm 2 , 40mm 2 , 42mm 2 , 45mm 2 , 48mm 2 , 50mm 2 , or a range consisting of any two of the above values. Figure 13 S1 shown in the figure represents the connection area between the first adapter 41 and the first electrode terminal 31. When the two are welded, the connection area is the welding surface, and the area of ​​the connection area is the welding area.

[0239] 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 weld area is relatively large, which can reduce welding resistance, reduce heat generation, and improve the cycle performance of the battery cell 7.

[0240] In some embodiments, the area of ​​the connection region between the first adapter 41 and the first tab 111 is 80 mm. 2 Up to 160mm 2 , for example 80mm 2 , 90mm 2 , 100mm 2, 110mm 2 , 120mm 2 , 130mm 2 , 140mm 2 , 150mm 2 , 160mm 2 Or a range consisting of any two of the above values. Figure 13 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.

[0241] The area of ​​the connection region between the first adapter 41 and the first tab 111 is within the above range. 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 7.

[0242] In some embodiments, the first electrode terminal 31 is used to connect to the external first busbar, and the area of ​​the connection area between the first electrode terminal 31 and the first busbar is 60 mm. 2 Up to 150mm 2 , for example 60mm 2 , 65mm 2 , 70mm 2 , 75mm 2 , 80mm 2 , 90mm 2 , 100mm 2 , 110mm 2 , 120mm 2 , 130mm 2 , 140mm 2 , 150mm 22 Or a range consisting of any two of the above values. Figure 13 S3 shown represents a connection area between the first electrode terminal 31 and the first current bus bar. When the two are welded, the connection area is a welding surface.

[0243] The area of ​​the connection region between the first electrode terminal 31 and the first busbar is within the above range. 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 reduce heat transfer to the interior of the battery cell 7, thereby improving the cycle performance of the battery cell 7.

[0244] In some embodiments, the first adapter 41 is located between the first pole tab 111 and the first electrode terminal 31; the projection surface of the connection area between the first adapter 41 and the first pole tab 111 along the thickness direction of the first electrode terminal is the first projection surface; the first electrode terminal 31 is used to connect to the external first bus bar, and the projection surface 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 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, and can be 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 a range consisting of any two of the above values. Figure 13 Where L1 represents the distance between the geometric center of the first projection surface and the geometric center of the second projection surface.

[0245] The above configuration enables an appropriate current conduction path between the first electrode terminal 31 and the first electrode tab 111 , which can effectively reduce the heat generation resistance, reduce the heat generation of the battery cell 7 , and improve the cycle performance of the battery cell 7 .

[0246] In some embodiments, the first adapter 41 is a positive electrode adapter, and the thickness of the positive electrode adapter is 0.6 mm to 2.0 mm, and optionally 1.0 mm to 1.5 mm. For example, the thickness of the positive electrode 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 a range consisting of any two of the above values.

[0247] In the case where the first adapter 41 is a positive electrode adapter, for example, when the material of the positive electrode 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 The upper limit depends on the thickness of the battery cell 7. For example, the cross-sectional area of ​​the first adapter 41 is 30 mm 2 , 32mm 2 , 35mm 2 , 38mm 2 , 40mm 2 , 42mm 2 , 45mm 2 , 48mm 2 , 50mm 2 , 52mm 2 , 55mm 2 , 58mm 2 , 60mm 2Or it is a range formed by any two of the above values. When the cross-sectional area of ​​the first adapter 41 is within the above range, the first adapter 41 has a stronger current flow capacity and is also conducive to rapid heat dissipation.

[0248] When the thickness of the positive electrode adapter is within the above range, the conduction area of ​​the positive electrode adapter is relatively large, which can reduce the heat generation resistance and reduce the heat generation; and the thickness is appropriate, which is conducive to the connection between the positive electrode adapter and other components such as the first electrode tab 111 or the first electrode terminal 31. For example, during welding, the welding power requirement is appropriate and the welding quality is excellent.

[0249] In some embodiments, the first adapter 41 is a negative electrode adapter, and the thickness of the negative electrode adapter is 0.5 mm to 1.5 mm, and optionally 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 consisting of any two of the above values.

[0250] In the case where the first adapter 41 is a negative electrode adapter, for example, when the negative electrode adapter is made of 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 The upper limit depends on the thickness of the battery cell 7. For example, the cross-sectional area of ​​the first adapter 41 is 24mm 2 , 25mm 2 , 28mm 2 , 30mm 2 , 32mm 2 , 35mm 2 , 38mm 2 , 40mm 2 , 42mm 2 , 45mm 2 , 48mm 2 , 50mm 2 , 52mm 2 , 55mm 2 , 58mm 2 , 60mm 2 Or it is a range formed by any two of the above values. When the cross-sectional area of ​​the first adapter 41 is within the above range, the first adapter 41 has a stronger current flow capacity and is also conducive to rapid heat dissipation.

[0251] When the thickness of the negative electrode adapter is within the above range, the conduction area of ​​the negative electrode adapter is relatively large, which can reduce the heat generation resistance and reduce the heat generation; and the thickness is appropriate, which is conducive to the connection between the negative electrode adapter and other components such as the first electrode tab 111 or the first electrode terminal 31. For example, during welding, the welding power requirement is appropriate and the welding quality is excellent.

[0252] In some embodiments, the housing 20 includes a shell 21 and an end cap 22. The shell 21 is a rectangular parallelepiped structure that accommodates the electrode assembly 10 and has an opening. The end cap 22 covers the opening. The end cap 22 is provided with a first electrode terminal 31. The projection of the first electrode terminal 31 along its own thickness direction in the thickness direction of the battery cell 7 is a first dimension, and the dimension 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 a range consisting of any two of the above values. Figure 14 W1 shown in FIG. 2 represents a first dimension, and W2 represents a second dimension. The second dimension can also be understood as the width of the end cover 22 .

[0253] The first electrode terminal 31 occupies a relatively large area of ​​the end cover 22 , which is beneficial for improving the current-carrying capacity of the first electrode terminal 31 .

[0254] The structural arrangement and position arrangement of the second electrode terminal 32 may be the same as or similar to those of the first electrode terminal 31 , and will not be described in detail herein.

[0255] In some embodiments, the battery cell 7 further includes a second adapter 42 , which is located between the second electrode tab 112 and the second electrode terminal 32 and is configured to electrically connect the second electrode tab 112 and the second electrode terminal 32 .

[0256] In other embodiments, the second electrode tab 112 and the second electrode terminal 32 are directly connected.

[0257] In some embodiments, the first electrode terminal 31 and the second electrode terminal 32 may be spaced apart and disposed on the end cover 22 .

[0258] The structure of the second electrode tab 112 in the second electrode piece 14 is the same as that of the first electrode tab 111 in the first electrode piece 13 . For example, the second electrode tab 112 in the second electrode piece 14 may include multiple electrodes, which will not be described in detail here.

[0259] In the embodiment of the present application, the electrode assembly 10 may be a laminated electrode assembly 10 or a wound electrode assembly 10 .

[0260] When the electrode assembly 10 is a laminated structure, the first electrode sheet 13 , the separator and the second electrode sheet 14 are stacked along the thickness direction of the battery cell 7 , and the projection surface of the first electrode terminal 31 along its own thickness direction is a rectangle.

[0261] In some embodiments, the electrode assembly 10 is a laminated structure, the first electrode terminal 31 is connected to the first electrode tab 111 of the first electrode sheet, and the area of ​​the connection area between the first electrode terminal 31 and the first electrode tab 111 is 140 mm. 2 Up to 420mm 2 , 210mm 2 Up to 350mm 2 , for example 140mm 2 , 150mm 2 , 180mm 2 , 200mm 2 , 210mm 2 , 250mm 2 , 280mm 2 , 300mm 2 , 350mm 2 , 380mm 2 , 400mm 2 , 420mm 2 Or a range consisting of any two of the above values, the above setting makes the current conduction path between the first electrode terminal 31 and the first electrode tab 111 appropriate, which can effectively reduce the heat generation resistance, reduce the heat generation of the battery cell 7, and improve the cycle performance of the battery cell 7.

[0262] When the electrode assembly 10 is a wound structure, the first electrode sheet 13 , the separator, and the second electrode sheet 14 are wound in one direction, and the projection surface of the first electrode terminal 31 along its own thickness direction is circular.

[0263] like Figure 15 As shown, in some embodiments, the coated portion of the first electrode piece 13 includes a first straight segment 131, the coated portion of the second electrode piece 14 includes a second straight segment 141, the first straight segment 131 and the second straight segment 141 are stacked along the thickness direction Y of the electrode assembly 10, and the ratio of the number of electrode tabs of the first electrode piece 13 to the number of first straight segments 131 of the first electrode piece 13 is 0.5 to 2; the electrolyte includes an organic solvent, 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%.

[0264] The electrolyte includes the chain carboxylate solvent in the above-mentioned mass content. The solvent system has a high conductivity, which is conducive to the rapid migration of lithium ions and improves the fast charging performance of the battery cell 7;

[0265] In a fast-charging system for the battery cell 7, the current density at the tab is typically high, resulting in increased heat generation and a high temperature in the battery cell 7, which can easily lead to degradation of the active material and decomposition of the organic solvent in the electrolyte, worsening the cycle performance. However, the positive electrode active material comprises an olivine-structured lithium-containing phosphate, which has a stable structure during charge and discharge and is less susceptible to capacity degradation, thus improving the cycle performance of the battery cell 7.

[0266] At the same time, when the ratio of the number of tabs of the first pole piece 13 to the number of the first straight sections 131 of the first pole piece 13 is within the above range, the shunt capacity of the tabs can be increased, and the fast charging performance of the battery cell 7 can be further improved; however, since the connection area between the tabs and other components such as the coating 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, and the stability of the electrolyte system and the stability of the active material are improved, which is beneficial to the improvement of the reliability of the battery cell 7 and can improve the cycle performance; and there are more connection points between the tabs and the coating part, etc., which can increase connection redundancy such as welding redundancy, and effectively improve product yield.

[0267] Therefore, the embodiment of the present application can improve the cycle performance and fast charging performance of the battery cell 7.

[0268] The polarities of the first electrode piece 13 and the second electrode piece 14 are opposite. When the first electrode piece 13 is a positive electrode piece, the second electrode piece 14 is a negative electrode piece, the first electrode terminal 31 is a positive electrode terminal, and the second electrode terminal 32 is a negative electrode terminal; or when the first electrode piece 13 is a negative electrode piece, the second electrode piece 14 is a positive electrode piece, the first electrode terminal 31 is a negative electrode terminal, and the second electrode terminal 32 is a positive electrode terminal.

[0269] The coated portion in the positive electrode sheet corresponds to the positive electrode coating portion, 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 coating portion includes the positive electrode current collecting portion and the positive electrode film layer arranged on at least one side of the positive electrode current collecting portion. When the positive electrode coating portion includes a positive electrode straight section, the positive electrode straight section includes the positive electrode current collecting portion and the positive electrode film layer arranged on at least one side of the positive electrode current collecting portion.

[0270] The coated portion in the negative electrode sheet corresponds to the negative electrode coating portion, 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 coating portion includes a negative electrode current collecting portion and a negative electrode film layer arranged on at least one side of the negative electrode current collecting portion. When the negative electrode coating portion includes a negative electrode straight section, the negative electrode straight section includes a negative electrode current collecting portion and a negative electrode film layer arranged on at least one side of the negative electrode current collecting portion.

[0271] In the embodiment of the present application, the first electrode tab 111 electrically connects the first straight section 131 and the first electrode terminal 31. The ratio of the number of first electrode tabs 111 of the first electrode sheet 13 to the number of first straight sections 131 of the first electrode sheet 13 is 0.5 to 2, for example, 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 a range consisting of any two of the foregoing values. When the ratio of the number of first electrode tabs 111 of the first electrode sheet 13 to the number of first straight sections 131 of the first electrode sheet 13 is within the foregoing range, the number of first electrode tabs 111 is relatively large, which can improve the current diversion effect, reduce the overcurrent impedance between the first electrode tab 111 and the first straight section 131, reduce the overcurrent temperature rise, and thus reduce the temperature rise inside the battery cell 7.

[0272] In the embodiment of the present application, the electrode assembly 10 includes a second straight segment 141, which is stacked with the first straight segment 131, and is alternately stacked along the thickness direction Y of the electrode assembly 10. The second electrode tab 112 is used to electrically connect the second straight segment 141 and the second electrode terminal 32. Optionally, the battery cell 7 also includes a separator 15, and the first straight segment 131, the separator 15, and the second straight segment 141 are alternately stacked.

[0273] In some embodiments, the ratio of the number of second pole tabs 112 of the second pole piece 14 to the number of second straight sections 141 of the second pole piece 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 a range consisting of any two of the foregoing values. When the ratio of the number of second pole tabs 112 of the second pole piece 14 to the number of second straight sections 141 of the second pole piece 14 is 0.5 to 2, the number of second pole tabs 112 is relatively large, which can improve the current diversion effect, reduce the overcurrent impedance between the second pole tab 112 and the second straight section 141, reduce the overcurrent temperature rise, and thus reduce the temperature rise inside the battery cell 7.

[0274] When the number of the first pole tabs 111 and the second pole tabs 112 is the same, the overcurrent density of the single pole tabs 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 shunting effect, and improving the charge and discharge capacity of the battery cell 7.

[0275] In some embodiments, the first tab 111 is a positive electrode tab; the first straight segment 131 includes a positive electrode active material, which includes an olivine-structured lithium-containing phosphate for providing lithium ions. A relatively large number of positive electrode tabs improves current diversion, reduces the overcurrent impedance between the first tab 111 and the first straight segment 131, and reduces the overcurrent temperature rise, thereby lowering the temperature rise within the battery cell 7.

[0276] In some embodiments, the second electrode tab 112 is a negative electrode tab, and the second straight segment 141 includes a negative electrode active material, which includes a carbon-based material and is configured to receive lithium ions from the first straight segment 131 .

[0277] The electrode assembly 10 may be a wound-type electrode assembly 10 or a laminated-type electrode assembly 10 .

[0278] In the case where the electrode assembly 10 has 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 whole-piece structure, the second electrode sheet 14 can be a whole-piece structure, and the separator 15 can be a whole-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 electrode tabs 111. The second electrode sheet 14 includes a second coating portion 140 and a plurality of second electrode tabs 112.

[0279] After winding to form the electrode assembly 10, the first coating portion 130 of the first electrode sheet 13 may include a plurality of first straight sections 131 and a plurality of first bent sections 132. The first bent sections 132 and the first straight sections 131 are arranged along the winding direction of the electrode assembly 10, and the first bent sections 132 are connected to the first straight sections 131, and the first electrode tab 111 is connected to the first straight section 131. During the winding process of the electrode assembly 10, the first electrode sheet 13 can be wound half a circle to form a first straight section 131.

[0280] The second coating portion 140 of the second electrode sheet 14 may include a plurality of second straight sections 141 and a plurality of second bent sections 142. The second bent sections 142 and the second straight sections 141 are arranged along the winding direction of the electrode assembly 10, and the second bent sections 142 are connected to the second straight sections 141, and the second electrode tabs 112 are connected to the second straight sections 141. The first straight sections 131 and the second straight sections 141 are alternately stacked, and the first bent sections 132 and the second bent sections 142 are alternately stacked.

[0281] From the appearance, the electrode assembly 10 includes a straight area, a bent area, and an electrode tab. The straight area includes a first straight section 131 and a second straight section 141. The bent area includes a first bent section 132 and a second bent section 142.

[0282] When the electrode assembly 10 has a wound structure, the ratio of the number of first tabs 111 of the first electrode sheet 13 to the number of first straight sections 131 of the first electrode sheet 13 can be selected from 0.5 to 1, can be greater than 0.5 and less than 1, and can further be selected from 0.6 to 0.99. This can be further combined with a chain carboxylate solvent containing 6% to 65% by weight to improve the cycling performance and fast charging performance of the battery cell 7. For example, when the electrode assembly 10 has a wound structure, the ratio of the number of first tabs 111 of the first electrode sheet 13 to the number of first straight sections 131 of the first electrode sheet 13 can be 0.5, 0.55, 0.6, 0.7, 0.8, 0.9, 0.95, 0.99, 1, or a range consisting of any two of the foregoing values.

[0283] Figure 15 It shows a case where the ratio of the number of first pole tabs 111 of the first pole piece 13 to the number of first straight sections 131 of the first pole piece 13 is 0.5. One circle of the first pole piece 13 can form two first straight sections 131, and one of the two first straight sections 131 is connected to the first pole tab 111, which means that there is one first pole tab 111 on each of the two first straight sections 131, that is, one of the two first straight sections 131 is provided with the first pole tab 111, and the other first straight section 131 is not provided with the first pole tab 111, which can be converted to 0.5 first pole tabs 111 being provided on each first straight section 131.

[0284] Figure 16 It shows the case where the ratio of the number of first pole tabs 111 of the first pole piece 13 to the number of first straight sections 131 of the first pole piece 13 is 1. One circle of the first pole piece 13 can form two first straight sections 131, and each first straight section 131 is connected to a first pole tab 111. It can be converted that each first straight section 131 is provided with a first pole tab 111.

[0285] Figure 17It shows a case where the ratio of the number of first pole tabs 111 of the first pole piece 13 to the number of first straight sections 131 of the first pole piece 13 is greater than 0.5 and less than 1. The first pole piece 13 is wound multiple times, and each turn can form two first straight sections 131. One first pole tab 111 can be set on the two first straight sections 131 of at least one turn among the multiple turns, that is, one first pole tab 111 is set in one turn; two first pole tabs 111 can be set on the two first straight sections 131 of at least another turn among the multiple turns, that is, two first pole tabs 111 are set in one turn; in the electrode assembly 10, it can be converted that more than 0.5 and less than 1 first pole tab 111 are set on each first straight section 131.

[0286] When the battery cell 7 meets the above conditions, the electrical conductivity of the solvent system is relatively high, which is conducive to the rapid migration of lithium ions and can improve the fast charging performance of the battery cell 7; and the electrolyte system has an excellent protective effect on the negative electrode active material, which is conducive to the improvement of the cycle performance of the battery cell 7; when the ratio of the number of first pole ears 111 to the number of first straight sections 131 is within the above range, the shunt capacity of the first pole ear 111 can be increased, which is conducive to the uniform reaction of the first pole piece 13 and the reduction of impedance, and can further improve the fast charging performance of the battery cell 7, and can also increase the connection points between the first pole ear 111 and other components, increase welding redundancy, and effectively improve product yield; because the connection area between the first pole ear 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, thereby making the electrolyte system more stable, which is conducive to the improvement of the reliability of the battery cell 7 and can improve the cycle performance.

[0287] Optionally, the first pole piece 13 includes a plurality of first pole tabs 111 , and the first pole tabs 111 are located on at least one side of the first coating portion 130 .

[0288] The number of electrode assemblies 10 may be at least one, and may be at least two, such as two, three, four, etc. At least two electrode assemblies 10 may be stacked along a thickness direction Y of the electrode assembly 10 .

[0289] like Figures 18 to 21 As shown, when the electrode assembly 10 has a laminated structure, there may be multiple first electrode sheets 13 and multiple second electrode sheets 14, and each first electrode sheet 13 has a first straight section 131 and a first electrode tab 111. The first straight sections 131 of the multiple first electrode sheets 13 and the second straight sections 141 of the multiple second electrode sheets 14 are stacked along the thickness direction Y of the electrode assembly 10.

[0290] When the electrode assembly 10 is a laminated structure, the electrode assembly 10 includes a straight area in terms of appearance. Optionally, the electrode assembly 10 may also include a bent area. For example, when the isolation membrane 15 adopts a whole-piece structure, the isolation membrane 15 is bent multiple times and then stacked with the first electrode sheet 13 and the second electrode sheet 14 to form the electrode assembly 10, or when the negative electrode sheet adopts a whole-piece structure, the negative electrode sheet is bent multiple times and then stacked with the positive electrode sheet and the isolation membrane to form the electrode assembly. The following is an example in which the electrode assembly 10 only includes a straight area.

[0291] Structurally, the electrode assembly 10 includes a first electrode piece 13, a second electrode piece 14 and an isolation membrane 15. The isolation membrane 15 is arranged between the first electrode piece 13 and the second electrode piece 14. The first electrode piece 13, the isolation membrane 15 and the second electrode piece 14 are stacked.

[0292] There can be multiple first pole pieces 13 and multiple second pole pieces 14, each first pole piece 13 includes a first straight section 131 and a first pole ear 111, and the first pole ear 111 is connected to the first straight section 131; each second pole piece 14 includes a second straight section 141 and a second pole ear 112, and the second pole ear 112 is connected to the second straight section 141; multiple first straight sections 131 and multiple second straight sections 141 are alternately stacked along the thickness direction Y of the electrode assembly 10.

[0293] When the electrode assembly 10 has a laminated structure, the ratio of the number of first tabs 111 of the first electrode sheet 13 to the number of first straight sections 131 of the first electrode sheet 13 is 1 to 2, and can be greater than 1 and less than or equal to 2. The addition of a chain carboxylate solvent containing 6% to 65% by weight can effectively improve the performance of the battery cell 7. For example, when the electrode assembly 10 has a laminated structure, the ratio of the number of first tabs 111 of the first electrode sheet 13 to the number of first straight sections 131 of the first electrode sheet 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 consisting of any two of the above values.

[0294] When the ratio of the number of first pole tabs 111 of the first pole piece 13 to the number of first straight sections 131 of the first pole piece 13 is 1, it means that the first pole tabs 111 and the first straight sections 131 are arranged in a one-to-one correspondence, which can be converted to that each first straight section 131 is provided with a first pole tab 111. Figure 10 A schematic structural diagram is shown in which a first electrode tab 111 is provided on each first straight segment 131 .

[0295] When the ratio of the number of first pole tabs 111 of the first pole piece 13 to the number of first straight sections 131 of the first pole piece 13 is 2, it can be converted that two first pole tabs 111 are provided on each first straight section 131. In this case, a first pole tab 111 can be provided on each side of the first straight section 131. Figure 11 A schematic structural diagram is shown in which two first tabs 111 are provided on each first straight section 131 .

[0296] When the ratio of the number of first electrode tabs 111 of the first electrode sheet 13 to the number of first straight sections 131 of the first electrode sheet 13 is greater than 1 and less than or equal to 2, it can be converted into greater than 1 and less than or equal to 2 first electrode tabs 111 being provided on each first straight section 131. For example, the electrode assembly 10 includes two first electrode sheets 13, one of which is provided with one first electrode tab 111 and the other is provided with two first electrode tabs 111, which means that each first electrode sheet 13 is provided with 1.5 first electrode tabs 111.

[0297] When the battery cell 7 meets the above conditions, the electrical conductivity of the solvent system is relatively high, which is conducive to the rapid migration of lithium ions and can improve the fast charging performance of the battery cell 7; and the electrolyte system has an excellent protective effect on the negative electrode active material, which is conducive to the improvement of the cycle performance of the battery cell 7; the number of the first pole ears 111 is relatively large, which can increase the shunt capacity of the first pole ear 111, so that the shunt in the first straight section 131 is uniform, which can further improve the fast charging performance of the battery cell 7, and can also increase the connection points between the first pole ear 111 and other components, increase welding redundancy, and effectively improve product yield; since the connection area between the first pole ear 111 and other components is relatively large, it can reduce the overcurrent impedance and the overcurrent temperature rise, and the temperature rise in the battery cell 7 system will not be too high, thereby making the electrolyte system more stable, which is conducive to the improvement of the reliability of the battery cell 7 and can improve the cycle performance.

[0298] Optionally, when the ratio of the number of first pole lugs 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, there is an average of more than one first pole lug 111 arranged on the first straight section 131, and more than one first pole lug 111 can be respectively arranged on both sides of the first straight section 131. In this case, more than one first pole lug 111 can share the current density of a single first pole piece 13, especially when the area of ​​the first pole piece 13 is relatively large, the shunting inside the first pole piece 13 is more uniform, which is conducive to uniform reaction and reduces impedance.

[0299] Optionally, when the ratio of the number of first pole lugs 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 lug 111 on average on the first straight section 131, more than one first pole lug 111 can be arranged on the same side of the first straight section 131. In this case, welding redundancy can be increased, and product yield can be effectively improved.

[0300] The arrangement of the second electrode tabs 112 can be the same or similar to that of the first electrode tabs 111, and will not be described in detail herein. For example, the ratio of the number of second electrode tabs 112 of the second electrode sheet 14 to the number of second straight sections 141 of the second electrode sheet 14 is 1 to 2, and can be greater than 1 and less than or equal to 2.

[0301] When the electrode assembly 10 is a laminated structure, when the number of the first pole tabs 111 and the second pole tabs 112 are the same, the overcurrent density of a single pole tab 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.

[0302] 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 .

[0303] like Figure 22 and Figure 23 As shown, in some embodiments, the first tab 111 includes a tab body 1111 and a plurality of tab protrusions 1112. The plurality of tab protrusions 1112 are all connected to a side of the tab body 1111 facing away from the first coating portion 130, and a gap is formed between two adjacent tab protrusions 1112. Of course, the first tab 111 may also include only the tab body 1111. Figure 22 A schematic diagram of unfolding the first electrode sheet 13 in the wound electrode assembly 10 is shown.

[0304] The arrangement of multiple tab protrusions 1112 enables the first tab 111 to have multiple connection sites. For example, when connecting the first tab 111 to the first adapter 41, the multiple tab 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 tab 111 and the first adapter 41, improve the welding yield, and enhance the stability of the connection between the two.

[0305] 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.

[0306] In some embodiments, the first electrode tab 111 is a positive electrode tab, and the thickness of the positive electrode tab is 10μm to 20μm, optionally 10μm to 15μm. Exemplarily, the thickness of the positive electrode tab is 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or a range consisting of any two of the above values. When the thickness of the positive electrode tab is within the above range, the positive electrode tab has excellent current capacity, can reduce heat generation, and is conducive to improving the fast charging performance of the battery cell.

[0307] In some embodiments, the first electrode tab 111 is a negative electrode tab, and the thickness of the negative electrode tab is 4 μm to 10 μm, and optionally 4 μm to 6 μm. For example, the thickness of the negative electrode 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 consisting of any two of the above values. When the thickness of the negative electrode tab is within the above range, the negative electrode tab has an excellent current flow capacity, can reduce heat generation, and is conducive to improving the fast charging performance of the battery cell.

[0308] In the embodiments of the present application, the thickness of the tab has the meaning in the art and can be detected by using equipment and methods known in the art, for example, the thickness can be measured using a micrometer.

[0309] [Positive electrode]

[0310] The positive electrode sheet includes a positive current collector and a positive electrode film layer comprising a positive electrode active material and disposed on at least one surface of the positive current collector. For example, the positive current collector may have two opposing surfaces in its thickness direction, and the positive electrode film layer may be disposed on either or both of the two opposing surfaces of the positive current collector.

[0311] In the embodiment of the present application, the upper limit charging voltage and the discharge cut-off voltage of the battery cell vary according to the different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the upper limit charging voltage can be 3.65V and the discharge cut-off voltage can be 2.0V. For another example, when the phosphate material includes lithium manganese iron phosphate, the upper limit charging voltage can be 4.3V and the discharge cut-off voltage can be 2.0V.

[0312] The 100% state of charge (SOC) and 0% state of charge (SOC) of a battery cell are defined as follows:

[0313] The battery cell is charged at a constant current charge rate of 0.33C to the upper limit voltage of the battery, and then charged at a constant voltage to 0.05C, corresponding to the state of 100% SOC of the battery cell; the battery cell is discharged 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.

[0314] In some embodiments, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) is 2.50 g / cm 3 to 2.80g / cm 3 ; Optional 2.55g / cm 3 to 2.70g / cm 3 For example, when the battery cell is at 100% state of charge (SOC), the compaction density of the positive electrode film is 2.50 g / cm 3 , 2.52g / cm 3 , 2.55g / cm 3 , 2.56g / cm 3 , 2.57g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.62g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.72g / cm 3 , 2.75g / cm 3 , 2.78g / cm 3 , 2.80g / cm 3 Or a range consisting of any two of the above values.

[0315] 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 because the positive electrode active material in the positive electrode film layer is stacked relatively densely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0316] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200 mg / 1540.25 mm 2 Up to 370mg / 1540.25mm 2 ; Optional: 240mg / 1540.25mm 2 Up to 330mg / 1540.25mm 2 For example, the coating weight of the positive electrode film on one side is 200 mg / 1540.25 mm 2 、210mg / 1540.25mm 2 、220mg / 1540.25mm2 、230mg / 1540.25mm 2 、240mg / 1540.25mm 2 、250mg / 1540.25mm 2 、260mg / 1540.25mm 2 、270mg / 1540.25mm 2 、280mg / 1540.25mm 2 、290mg / 1540.25mm 2 、300mg / 1540.25mm 2 、310mg / 1540.25mm 2 、320mg / 1540.25mm 2 、330mg / 1540.25mm 2 、340mg / 1540.25mm 2 、350mg / 1540.25mm 2 、360mg / 1540.25mm 2 、370mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0317] When the single-sided coating weight of the positive electrode film layer is within the above range, the heat generated per unit area of ​​the positive electrode sheet will not be too large, and the energy density of the battery cell can be improved.

[0318] In the embodiments of the present application, the compaction density of the positive electrode film layer of a battery cell at 100% state of charge (SOC) has a meaning well known in the art. Specifically, the positive electrode sheet of a battery cell at 100% state of charge (SOC) is disassembled and the compaction density of the positive electrode film layer is measured. For example, a single-sided coated positive electrode sheet (if a double-sided coated sheet is used, the positive electrode film layer on one side may be wiped off first) is punched into small discs with an area of ​​S1. The discs are weighed and recorded as M1, and their thickness H1 is measured. The positive electrode film layer of the weighed positive electrode sheet is then wiped off, and 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 of the positive electrode sheet M1 - the weight of the positive electrode collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode sheet H1 - the thickness of the positive electrode collector H0, 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.

[0319] In some embodiments, the powder resistivity of the positive electrode active material is 1 Ω·cm to 27.5 Ω·cm; alternatively, less than or equal to 20 Ω·cm; alternatively, less than or equal to 11 Ω·cm. For example, the powder resistivity of the positive electrode active material may 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 a range consisting of any two of the above values.

[0320] The powder resistivity of the positive electrode active material is relatively low, which makes the resistance of the positive electrode sheet relatively low and the heat generation of the battery cell less.

[0321] In the embodiments of the present application, the powder resistivity of the material is well known in the art and can be tested using methods and equipment well known in the art, for example, using a PRCD1100 powder resistivity meter according to the test standard GB / T30835-2014.

[0322] In some embodiments, the powder compaction density of the positive electrode active material at 30,000 N is 2.46 g / cm 3 Up to 2.8 g / cm 3 For example, the powder compaction density of the positive electrode active material at 30000N is 2.46g / cm 3 , 2.47g / cm 3 , 2.48g / cm 3 , 2.49g / cm 3 , 2.5g / cm 3 , 2.51g / cm 3 , 2.55g / cm 3 , 2.58g / cm 3 , 2.60g / cm 3 , 2.65g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.72g / cm 3 , 2.75g / cm 3 , 2.78g / cm 3 , 2.80g / cm 3 Or a range consisting of any two of the above values.

[0323] When the powder compaction density of the positive electrode active material at 30,000 N is within the above range, 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 densely and the contact resistance between particles is smaller, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0324] In the embodiment of the present application, the powder compaction density of the material is a well-known meaning in the art and can be tested using methods and equipment known in the art. The test is performed 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 UTM7305 electronic pressure testing machine with a bottom area of ​​1.327 cm 2 The mold was pressurized to 3000 kg (equivalent to 30000 N), maintained for 30 seconds, then released and maintained for 10 seconds, and then the powder compaction density of the positive electrode active material under a force of 30000 N was recorded and calculated.

[0325] In some embodiments, the positive electrode active material has a charge capacity of 150 mAh / g to 170 mAh / g at a 0.1 C rate, optionally 157 mAh / g to 170 mAh / g. For example, the positive electrode active material has a charge capacity of 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 a range consisting of any two of the above values.

[0326] When the charge gram 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.

[0327] In the embodiment of the present application, the gram capacity of the active material has a meaning well known in the art and can be tested using equipment and methods well known in the art. The test method for the first coulombic efficiency and the first discharge specific capacity in Appendix G of the national standard GB / T 24533-2019 can be used. Metal lithium is used as the negative electrode and a sample electrode comprising the above-mentioned material is used as the positive electrode to assemble a half-button battery. Under the conditions of 23°C±2°C, the half-button battery is charged and discharged at a rate of 0.1C on a battery tester or other test equipment of equivalent performance to obtain the charge capacity, and then the capacity is divided by the mass of the active material of the electrode to obtain the charge gram capacity parameter.

[0328] In some embodiments, the mass proportion of the lithium-containing phosphate with an olivine structure in the positive electrode active material may be greater than or equal to 80% and less than or equal to 100%, and the positive electrode active material of the present application may be considered to be an olivine-structured lithium-containing phosphate system. When the mass proportion of the lithium-containing phosphate with an olivine structure is less than 100%, the positive electrode active material may also include a commonly used positive electrode active material, for example, including but not limited to at least one of a lithium-containing transition metal oxide and a lithium-containing phosphate. Examples of lithium-containing transition metal oxides may 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 lithium-containing phosphates may 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 iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0329] Optionally, the mass proportion of the lithium-containing phosphate with an olivine structure in the positive electrode active material is 100%.

[0330] In an embodiment of the present application, the lithium-containing phosphate with an olivine structure may be phosphate particles, or a material obtained by coating and modifying the phosphate particles. For example, the lithium-containing phosphate with an olivine structure includes phosphate particles and a coating layer, 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.

[0331] By coating the surface of the phosphate particles with a 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 the migration rate of lithium ions can be promoted, thereby improving the fast charging capability of the battery and reducing the heat generation of the battery cell.

[0332] 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 zCompounds 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, and Mg, Me comprises one or more of Mn, Fe, Co, and 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, and Ce, X comprises one or more of S, Si, Cl, B, C, and N, and Y comprises one or more of O and F. The phosphate particles have excellent cycling stability, which is beneficial for improving the cycling performance of battery cells.

[0333] Exemplarily, the phosphate particles include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The battery cells are accompanied by the deintercalation and consumption of active ions such as Li during the charge and discharge process, and the molar content of Li in the battery cells is different when discharged to different states. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc., the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li may change after charge and discharge cycles. In the enumeration of positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, etc. in the embodiment of the present application, the molar content of oxygen O is only a theoretical state value. Lattice oxygen release will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate. The above situations are all within the scope of protection of this application.

[0334] In some embodiments, the coating layer comprises a 3-d Fe 2-d M2 d (PO x2 ) y2 The fast ion conductor M2 includes one or more elements selected from Ti, Zr, Hf, Ge and Sn, 0≤d≤1, 0<x2<5, 0<y2<4.

[0335] Exemplarily, the fast ion conductor is a material having a NASICON structure, such as 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.

[0336] Fast ion conductors with a NASICON structure are materials with ultrafast ion conduction capabilities. They possess abundant three-dimensional lithium ion diffusion and transport channels, and exhibit advantages such as high ion conduction efficiency and strong structural stability during multiple lithium de- and intercalation processes. Coating phosphate particles with a fast ion conductor containing a NASICON structure can significantly increase the lithium ion transport rate at the positive electrode during multiple lithium de- and intercalation processes, improving the ionic conductivity of the positive electrode active material and the rapid charging capability of the battery cell. Furthermore, it can increase the specific capacity and the energy density of the corresponding battery cell.

[0337] In some embodiments, the coating layer further includes carbon.

[0338] The carbon element and the fast ion conductor can be arranged in layers. For example, the carbon element serves as an independent carbon coating layer, and the fast ion conductor serves 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 facing 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 facing away from the phosphate particles. Of course, the carbon element and the fast ion conductor can also be arranged in the same layer.

[0339] Optionally, a carbon coating can be formed by carbonizing an organic carbon source (e.g., glucose, polyethylene glycol, etc.) and coating the surface of the fast ion conductor layer. The carbon coating can partially or completely cover the fast ion conductor layer. The carbon coating can significantly improve the electronic conductivity of the phosphate particles, compensating for their poor electronic conductivity and increasing the energy density of the battery cell.

[0340] Specifically, the provision of the carbon coating layer enables the positive electrode active material of the present application to have the following advantages:

[0341] 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 delithiation 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.

[0342] 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 phase interface and improving the charging capacity of the battery cell.

[0343] Coating a carbon coating layer 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.

[0344] The cathode active material of this application, based on a lithium-containing phosphate, leverages the advantages of lithium-containing phosphates: low cost, high reliability, and excellent cycling stability. It also utilizes coating layers (fast ion conductor layer and carbon coating layer) to address their poor electronic and ionic conductivity. Battery cells prepared with this cathode active material can improve the energy density of the battery cells while maintaining excellent cycling performance.

[0345] In the embodiments of this application, the element content in the positive electrode active material has a meaning well known in the art and can be measured using equipment and methods well known in the art. For example, in accordance with EPA 6010D-2014, it can be measured by inductively coupled plasma atomic emission spectrometry (ICP-OES, Thermo ICAP7400). After discharging the battery cell to 0% state of charge (SOC), the positive electrode sheet is disassembled, cleaned with DMC, dried, and calcined at high temperature to remove impurities. Then, 0.4g of the positive electrode active material is weighed and 10ml (50% concentration) of aqua regia is added. The sample is then placed on a plate at 180°C for 30 minutes. After digestion on the plate, the volume is adjusted to 100ml, and quantitative analysis is performed using a standard curve method.

[0346] In some embodiments, the degree of graphitization of the positive electrode active material is 0.15 to 0.32, optionally 0.19 to 0.26. For example, the degree of graphitization 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 consisting of any two of the above values.

[0347] 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 battery cell.

[0348] In the embodiment of the present application, a higher degree of graphitization of the material indicates a lower degree of disorder, which can be tested according to the test standard JIS / K 0131-1996 X-ray diffraction analysis method general rules.

[0349] In some embodiments, the mass content of carbon 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.

[0350] Optionally, the mass content of carbon 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 14m 2 / g.

[0351] Illustratively, the mass content of carbon in the olivine-structured lithium-containing phosphate is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or a range consisting of any two of the above values.

[0352] For example, the specific surface area of ​​the lithium-containing phosphate with olivine structure is 5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g、15m 2 / g、16m 2 / g、17m 2 / g、18m 2 / g or a range consisting of any two of the above values.

[0353] 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 increasing the specific surface area of ​​the material, more conducive to effective contact between the electrolyte and phosphate particles, and conducive 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, it can significantly improve the conductivity of the lithium-containing phosphate with an olivine structure, which is beneficial to improving the ionic conductivity and electronic conductivity of the lithium-containing phosphate with an olivine structure, and can improve the rapid charging capability and energy density of the battery cell.

[0354] In the embodiments of the present application, the specific surface area of ​​the material has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, 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 using a Tri-Star 3020 specific surface area pore size analyzer produced by Micromeritics, USA.

[0355] 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.

[0356] Illustratively, the Dv50 of the positive electrode active material can be 1µm, 1.1µm, 1.15µm, 1.2µm, 1.25µm, 1.3µm, 1.35µm, 1.4µm, 1.45µm, 1.5µm, 1.55µm, 1.6µm, 1.65µm, 1.7µm, 1.75µm, 1.8µm, 1.85µm, 1.9µm, 1.95µm, 2µm, or a range consisting of any two of the above values.

[0357] For example, 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 consisting of any two of the above values.

[0358] The particle size of the positive electrode active material is relatively small, the lithium ion deintercalation path in the positive electrode active material is short, and the heat generation is less. Moreover, the particle size of the above-mentioned positive electrode active material is not too small, and basically no agglomeration will occur during the processing and preparation process, making the performance of the positive electrode active material stable.

[0359] In the embodiment of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% of the volume distribution, and the volume average particle size Dv10 of the material refers to the particle size corresponding to 10% of the volume distribution. It can be detected by equipment and methods known in the art. For example, the positive electrode active material is used as a sample, and the Dv50 and Dv10 of the particles are tested by a Mastersizer 2000E laser particle size analyzer according to the test standard GB / T 19077-2016.

[0360] When the positive electrode active material includes other materials in addition to the lithium-containing phosphate having an olivine structure, the volume distribution particle size of the positive electrode active material refers to the volume distribution particle size of all the positive electrode active materials.

[0361] In some embodiments, the olivine-structured lithium-containing phosphate is in a granular form, comprising secondary particles, each of which comprises a plurality of primary particles, and the average particle size of the primary particles is between 200 nm and 500 nm. For example, 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, or 500 nm, or a range consisting of any two of the foregoing values.

[0362] The average particle size of the primary particles is relatively small, the lithium ion deintercalation path in the positive electrode active material is shorter, and the heat generated is less.

[0363] In the embodiments of the present application, secondary particles refer to particles in an agglomerated state formed by the aggregation of two or more primary particles. Primary particles and secondary particles can be easily distinguished by experimental means (such as using a scanning electron microscope to take SEM images), and the average particle size of the primary particles can be obtained by testing in the scanning electron microscope SEM images. The SEM test parameters can be set to: an operating voltage (EHT) of 10.00 kV, an InLens detector, a working distance of 4.6 mm, and a magnification of 1000X.

[0364] In some embodiments, the positive electrode film layer further comprises one or more of a ternary material, lithium phosphate, lithium dihydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite. These materials can serve as lithium replenishers, which can replenish lithium ions in the positive electrode film layer, compensating for irreversible lithium ion loss within the system, increasing capacity, and thereby improving the energy density of the battery cell.

[0365] Optionally, the ternary material includes Li x3 A y3 Ni a3 Co b3 Mn c M3 (1-a3-b3-c3) Y3 z3 , wherein, 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 more of Na, K, and Mg, M3 includes one or more 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 more of O and F.

[0366] For example, 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 Co 0.15 Al 0.05 At least one of O2.

[0367] In some embodiments, the lithium supplement agent comprises 0.5% to 5% by weight of the positive electrode film layer, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of these values. When the lithium supplement agent comprises within the above range, it can replenish lithium ions in the positive electrode film layer, compensating for irreversible lithium ion loss in the system, increasing capacity, and thereby improving the energy density of the battery cell.

[0368] The lithium replenisher can be located in the same layer as the positive electrode active material, or in different layers. When the lithium replenisher and the positive electrode active material are located in different layers, the lithium replenisher can be located in the lithium replenisher layer, and the positive electrode active material can be located in the positive electrode active material layer. In other words, the positive electrode film layer includes a lithium replenisher layer and a positive electrode active material layer. The positive electrode active material layer can be arranged on at least one side of the positive electrode current collecting part, and the lithium replenisher layer can be located between the positive electrode active material layer and the positive electrode current collecting part. Alternatively, the lithium replenisher layer can be arranged on at least one side of the positive electrode current collecting part, and the positive electrode active material layer can be located between the lithium replenisher layer and the positive electrode current collecting part. Optionally, the lithium replenisher layer can be located between the positive electrode active material layer and the positive electrode current collecting part. During the cyclic charge and discharge process of the battery cell, the lithium replenisher in the lithium replenisher layer can be gradually released into the system to compensate for the lithium loss of the battery system.

[0369] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application does not particularly limit the type of positive electrode conductive agent. For example, the positive 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, the mass content of the positive electrode conductive agent is ≤5% based on the mass of the positive electrode film layer.

[0370] 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 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 fluorine-containing acrylic resin. In some embodiments, based on the mass of the positive electrode film layer, the mass content of the positive electrode binder is ≤5%.

[0371] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0372] In some embodiments, the ratio of the thickness of the positive current collector to the thickness of the positive electrode film layer on one side is 0.05 to 0.3. For example, the ratio of the thickness of the positive current collector to the thickness of the positive electrode film layer on one side 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 consisting of any two of the above values.

[0373] When the ratio of the thickness of the positive electrode current collecting portion to the thickness of the single-side positive electrode film layer is within the above range, the fast charging capability and energy density of the battery cell can be improved.

[0374] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 20 μm, 10 μm to 15 μm, or optionally 12 μm to 15 μm. For example, the thickness of the positive electrode 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 consisting of any two of the above values.

[0375] When the thickness of the positive electrode current collecting portion is within the above range, the positive electrode current collecting portion has a relatively excellent current flow capacity and can enable the battery cell to have a relatively high energy density.

[0376] In the embodiment of the present application, the thickness of the positive electrode film layer and the positive electrode current collecting portion has a meaning well known in the art and can be detected by using equipment and methods well known in the art. For example, a caliper is used to measure the thickness of the positive electrode sheet, the film layer on the surface of the positive electrode current collecting portion is removed, and the thickness of the positive electrode current collecting portion is measured with a caliper. 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 sheet minus the thickness of the positive electrode current collecting portion. 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 sheet minus the thickness of the positive electrode current collecting portion) / 2.

[0377] The positive electrode film is typically formed by coating a positive electrode slurry onto the positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP).

[0378] The positive electrode sheet does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the embodiments of the present application further includes a positive electrode conductive layer sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0379] In some embodiments, the positive electrode sheet further includes a positive electrode conductive layer, which 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 generated by the positive electrode sheet, and thus reduce the heat generated by the battery cell.

[0380] In some embodiments, the thickness of the positive electrode conductive layer is 0.5 μm to 2 μm. For example, 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 consisting of any two of the above values.

[0381] When the thickness of the positive electrode conductive layer is within the above range, the conductivity of the positive electrode sheet can be further improved, the heat generation of the positive electrode sheet can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can be improved.

[0382] In the embodiment of the present application, the thickness of the positive electrode conductive layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, for example, performing a tomographic scan on the positive electrode sheet to directly measure the thickness of the positive electrode conductive layer.

[0383] In some embodiments, the positive electrode conductive layer includes one or more of a positive electrode conductive agent and a positive electrode binder.

[0384] 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 consisting of any two of the above values.

[0385] Illustratively, 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 heat generation in the battery cell.

[0386] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%, illustratively, 50%, 60%, 65%, 70%, or a range consisting of any two of the above values.

[0387] Illustratively, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, polyacrylic acid, and a fluorine-containing acrylate resin. The positive electrode binder in the positive electrode conductive layer can improve the bonding performance between the positive electrode current collector and the positive electrode film layer, thereby improving the structural stability of the positive electrode sheet.

[0388] [Negative electrode]

[0389] The negative electrode sheet includes a negative current collector and a negative electrode film layer comprising a negative electrode active material and disposed on at least one surface of the negative current collector. For example, the negative current collector may have two opposing surfaces in its thickness direction, and the negative electrode film layer may be disposed on either or both of the two opposing surfaces of the negative current collector.

[0390] In some embodiments, the negative electrode layer has a compaction density of 1.15 g / cm2 at 100% state of charge. 3 to 1.36g / cm 3 ; Optional 1.25g / cm 3 to 1.36g / cm 3 For example, the compaction density of the negative electrode film layer of the battery cell at 100% charge state is 1.15g / cm 3 , 1.18g / cm 3 , 1.20g / cm 3 , 1.22g / cm 3 , 1.25g / cm 3 , 1.28g / cm 3 , 1.3g / cm 3 , 1.32g / cm 3 , 1.35g / cm3 , 1.36g / cm 3 Or a range consisting of any two of the above values.

[0391] When the compaction 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 because the negative electrode active material in the negative electrode film layer is stacked relatively densely, the contact resistance between particles is small, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0392] In the embodiment of the present application, the compaction density of the negative electrode film layer of the battery cell at 100% charge state has a meaning well known in the art and can be detected using equipment and methods well known in the art, and the detection method is the same as the compaction density test method of the positive electrode film layer mentioned above.

[0393] In some embodiments, the single-side coating weight of the negative electrode film layer is 90 mg / 1540.25 mm 2 Up to 170mg / 1540.25mm 2 , optional 110mg / 1540.25mm 2 Up to 150mg / 1540.25mm 2 For example, the coating weight of the negative electrode film on one side is 90 mg / 1540.25 mm 2 、92mg / 1540.25mm 2 、95mg / 1540.25mm 2 、96mg / 1540.25mm 2 、100mg / 1540.25mm 2 、102mg / 1540.25mm 2 、104mg / 1540.25mm 2 、105mg / 1540.25mm 2 、108mg / 1540.25mm 2 、110mg / 1540.25mm 2 、112mg / 1540.25mm 2 、114mg / 1540.25mm 2 、115mg / 1540.25mm 2 、116mg / 1540.25mm 2 、118mg / 1540.25mm 2 、120mg / 1540.25mm 2 、122mg / 1540.25mm 2 、125mg / 1540.25mm 2 、128mg / 1540.25mm 2、130mg / 1540.25mm 2 、132mg / 1540.25mm 2 、135mg / 1540.25mm 2 、137mg / 1540.25mm 2 、140mg / 1540.25mm 2 、142mg / 1540.25mm 2 、145mg / 1540.25mm 2 、148mg / 1540.25mm 2 、150mg / 1540.25mm 2 、152mg / 1540.25mm 2 、155mg / 1540.25mm 2 、160mg / 1540.25mm 2 、165mg / 1540.25mm 2 、170mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0394] When the single-side coating weight of the negative electrode film layer is within the above range, the heat generated per unit area of ​​the negative electrode sheet will not be too large, and the energy density of the battery cell can be improved.

[0395] In the embodiment of the present application, the single-sided coating weight of the negative electrode film layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, such as the single-sided coating weight test method of the film layer described above.

[0396] In some embodiments, the powder resistivity of the negative electrode active material is 0.005 Ω·cm to 0.043 Ω·cm, and may be 0.04 Ω·cm. For example, the powder resistivity of the negative electrode active material may 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 consisting of any two of the foregoing values.

[0397] The powder resistivity of the negative electrode active material is relatively low, which makes the resistance of the negative electrode sheet relatively low and the heat generation of the battery cell less.

[0398] In the embodiment of the present application, the powder resistivity of the negative electrode active material is well known in the art and can be detected using equipment and methods well known in the art, such as the powder resistivity test method of the positive electrode active material described above.

[0399] In some embodiments, the powder compaction density of the negative electrode active material under a pressure of 20,000 N is 1.5 g / cm 3 Up to 1.85g / cm 3 , optional 1.55g / cm 3 Up to 1.65g / cm 3 For example, the powder compaction density of the negative electrode active material under a pressure of 20,000 N is 1.5 g / cm 3 , 1.55g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 , 1.7g / cm 3 , 1.75g / cm 3 , 1.8g / cm 3 , 1.85g / cm 3 Or a range consisting of any two of the above values.

[0400] When the powder compaction density of the negative electrode active material at 20,000 N is within the above range, 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 densely and the contact resistance between particles is smaller, the resistance of the electrode sheet can be further reduced, thereby reducing heat generation.

[0401] In the embodiments of the present application, the powder compaction density of the material is a well-known meaning in the art and can be tested using methods and equipment known in the art in accordance with the test standard GB / T24533-2009. As an example, a certain amount of negative electrode active material is taken as a sample and placed in a UTM7305 electronic pressure testing machine with a bottom area of ​​1.327 cm 2 The mold was pressurized to 2000 kg (equivalent to 20000 N), maintained for 30 seconds, then released and maintained for 10 seconds, and then the powder compaction density of the negative electrode active material under a force of 20000 N was recorded and calculated.

[0402] In some embodiments, the negative electrode active material has a charge capacity in the range of 350 mAh / g to 480 mAh / g at a 0.1 C rate. For example, the negative electrode active material has a charge capacity in the range of 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 consisting of any two of the foregoing values.

[0403] When the charge gram 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.

[0404] In the embodiment of the present application, the charge gram capacity of the negative electrode active material at a rate of 0.1C has a meaning well known in the art and can be detected using equipment and methods well known in the art. The detection method is the same as the charge gram capacity test method of the positive electrode active material at a rate of 0.1C mentioned above.

[0405] In some embodiments, the negative electrode active material includes a carbon-based material. Carbon-based materials have high cycle stability and can improve the cycle performance of the battery cell. Optionally, the mass proportion 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%.

[0406] 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. The two are used in combination, and the cycle performance of the battery cell is relatively excellent.

[0407] Optionally, the carbon-based material includes graphite particles, and the graphite particles have a degree of graphitization of 92.0% to 94.5%. Exemplarily, the degree of graphitization of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5%, or a range consisting of any two of the foregoing values.

[0408] When the graphitization degree of the graphite particles is within the above range, the graphite particles have relatively excellent electrical conductivity, can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and can improve the fast charging performance of the battery cell.

[0409] In some embodiments, the graphite particles include artificial graphite and a carbon coating. The artificial graphite includes secondary particles, each of which includes a plurality of primary particles. The carbon coating is coated on the surface of the artificial graphite. The carbon in the carbon coating is primarily amorphous carbon. Amorphous carbon refers to a transitional carbon material with a very low degree of graphitization and crystallization, nearly an amorphous form (or lacking a fixed shape and periodic structural regularity). In this application, amorphous carbon refers to the product of carbonization of an organic carbon source.

[0410] Artificial graphite includes secondary particles. There are more migration paths for lithium ions in artificial graphite, and the migration paths in primary particles are shorter, which can improve the migration rate of lithium ions. The carbon coating has more end faces and defects, which increases the number of sites for lithium ion insertion and extraction, making the carbon coating more conductive, which can reduce the internal resistance of the negative electrode and reduce the heat generation of the battery cell.

[0411] Optionally, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. Exemplarily, the mass content of the carbon coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of the above values.

[0412] When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode plate can be further reduced, and the heat generation of the battery cell can be reduced.

[0413] In an embodiment of the present application, the graphite particles can be prepared by methods known in the art. For example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and forming a carbon coating layer on at least a portion of the surface of the artificial graphite particles after carbonization treatment.

[0414] Optionally, the organic carbon source includes one or more of coal tar, petroleum tar, phenolic resin, and coconut shell. Further, optionally, the organic carbon source includes petroleum tar. Optionally, the softening point of the coal tar or petroleum tar is below 250°C.

[0415] Optionally, the carbonization temperature is 700° C. to 1800° C. Optionally, the carbonization temperature is 1000° C. to 1300° C. When the carbonization temperature is within a suitable range, the organic carbon source can be carbonized and a coating layer containing amorphous carbon can be formed on at least a portion of the surface of the artificial graphite.

[0416] Optionally, the carbonization treatment time is 1 hour to 6 hours.

[0417] 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.

[0418] 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.

[0419] Optionally, based on the mass of the negative electrode active material, the mass content of silicon in the silicon-based material is 0.3% to 10.0%, optionally 1% to 6%. Exemplarily, the mass content of silicon 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 a range consisting of any two of the above values.

[0420] When the mass content of silicon in the silicon-based material is within the above range, the capacity of the negative electrode active material can be increased, thereby improving the energy density of the battery cell.

[0421] Alternatively, the silicon-based material may include at least one of elemental silicon, silicon oxide, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy material.

[0422] In some embodiments, the negative electrode active material may include at least one of a tin-based material and lithium titanate in addition to the aforementioned carbon-based material and optionally a silicon-based material. The tin-based material may include at least one of elemental tin, tin oxide, and a tin alloy.

[0423] The qualitative and quantitative properties of each substance or element in this application can be detected using appropriate equipment and methods known to those skilled in the art. The relevant detection methods can refer to domestic and international detection standards, domestic and international enterprise standards, etc., and those skilled in the art can also adapt certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. A single detection method can be used for qualitative or quantitative determination, or several detection methods can be used in combination for qualitative or quantitative determination.

[0424] For example, the present application may combine JIS / K0131-1996 General Rules for X-ray Diffraction Analysis Methods to perform X-ray powder diffraction testing and qualitative analysis on the negative electrode sheet or negative electrode active material.

[0425] Artificial graphite and natural graphite can be distinguished by the SEM cross-section taken by a scanning electron microscope (SEM). The SEM cross-section of natural graphite shows gaps between the flake structures, while the SEM cross-section of artificial graphite is dense and has no obvious gaps. They can also be distinguished by the XRD spectrum obtained by the X-ray diffraction method. The XRD spectrum of natural graphite shows obvious 2H phase and 3R phase, while the XRD spectrum of artificial graphite only shows 2H phase.

[0426] In the embodiment of the present application, the negative electrode film layer includes at least one film layer, which can be a single film layer or at least two film layers. Optionally, the negative electrode film layer includes at least two film layers.

[0427] In the case where 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. In the case of a single-layer film layer, the volume average particle size Dv50 of the negative electrode active material is 8.2μm to 13.5μm. Exemplarily, the volume average particle size Dv50 of the negative electrode active material is 8.2μm, 8.5μm, 8.8μm, 9μm, 9.2μm, 9.5μm, 9.8μm, 10μm, 10.2μm, 10.5μm, 10.8μm, 11μm, 11.2μm, 11.5μm, 11.8μm, 12μm, 12.2μm, 12.5μm, 12.8μm, 13μm, 13.2μm, 13.5μm or a range consisting of any two of the above values.

[0428] When the negative electrode film layer comprises at least two 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 may be located in one of the at least two film layers, or in at least two of the at least two film layers. The negative electrode film layer may include two film layers, three film layers, four film layers, or even more film layers.

[0429] 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 arranged on the surface of the negative electrode current collecting portion, 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 away from the negative electrode current collecting portion, the carbon-based material in the second negative electrode film layer includes graphite particles, and the graphite particles in the first negative electrode film layer and the graphite particles in the second negative electrode film layer may be the same or different.

[0430] The interface between the first negative electrode film layer and the second negative electrode film layer may be regular or irregular, and may optionally be irregular.

[0431] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0432] The negative electrode film comprises at least two layers, and layered coating can improve the rapid charging performance of the battery cell. In particular, when the first and second negative electrode film layers are different, the pores of the negative electrode film layers can be differentiated, reducing the tortuosity of lithium-ion transport and improving the rapid charging performance of the battery cell.

[0433] 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 for 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.

[0434] There is a difference in the particle size between 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 the fast charging process, the overpotential of the second negative electrode film layer is usually higher, and the bottleneck of fast charging mainly lies in the second negative electrode film layer. In the embodiment of the present application, the particle size of 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 plating on the surface of the negative electrode plate.

[0435] Optionally, the negative electrode active material in the first negative electrode film layer is in a granular form, and its volume average particle size Dv50 is 9.5 μm to 18.5 μm, and optionally 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 consisting 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 9.5 μm to 18.5 μm, and optionally 9.5 μm to 14.6 μm.

[0436] 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, the solid phase transmission path of lithium ions can be shortened and the fast charging performance can be improved; on the other hand, the material is not easy to agglomerate during the preparation process, which can improve the stability of the material.

[0437] Optionally, the negative electrode active material in the second negative electrode film layer is in a granular form, and a volume average particle size Dv50 thereof is 7.8 μm to 14.3 μm, and optionally 7.8 μm to 11.3 μm. Illustratively, 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 consisting 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 7.8 μm to 14.3 μm, and optionally 7.8 μm to 11.3 μm.

[0438] 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 easy to agglomerate during the preparation process, which can improve the stability of the material; on the other hand, the combination of the negative electrode active material in the second negative electrode film layer within the above volume average particle size range and the negative electrode active material in the first negative electrode film layer is conducive to constructing a 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.

[0439] In the embodiment of the present application, the volume average particle size Dv50 of the negative electrode active material has a meaning well known in the art and can be detected using equipment and methods well known in the art, and its detection method is the same as the volume average particle size Dv50 test method of the positive electrode active material mentioned above.

[0440] Optionally, the tap density of the carbon-based material in the first negative electrode film layer is less than or equal to the tap density of the carbon-based material in the second negative electrode film layer. The tap density can reflect the filling density of the active material in the film layer. When the tap density of the carbon-based material in the second negative electrode film layer is greater than the tap density of the carbon-based material in the first negative electrode film layer, the second negative electrode film layer is filled more densely, thereby improving the energy density of the battery cell. The first negative electrode film layer is filled relatively sparsely and has more abundant pores, which can improve the fast charging performance of the battery cell. When the negative electrode active material includes graphite particles, the tap density of the graphite particles in the first negative electrode film layer is less than or equal to the tap density of the graphite particles in the second negative electrode film layer.

[0441] Optionally, the tap density of the carbon-based material in the first negative electrode film layer is 0.82 g / cm 3 to 1.21g / cm3 , for example 0.82 g / cm 3 , 0.85g / cm 3 、0.88g / cm 3 , 0.90g / cm 3 , 0.92g / cm 3 , 0.95g / cm 3 , 0.98g / cm 3 , 1.00g / cm 3 , 1.05g / cm 3 、1.08g / cm 3 , 1.10g / cm 3 , 1.12g / cm 3 , 1.15g / cm 3 , 1.18g / cm 3 , 1.20g / cm 3 , 1.21g / cm 3 When the tap density of the carbon-based material in the first negative electrode film layer is within an appropriate range, the fast charging performance of the battery cell can be improved.

[0442] Optionally, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm 3 Up to 1.25g / cm 3 , for example 0.90g / cm 3 , 0.92g / cm 3 , 0.95g / cm 3 , 0.98g / cm 3 , 1.00g / cm 3 , 1.05g / cm 3 、1.08g / cm 3 , 1.10g / cm 3 , 1.12g / cm 3 , 1.15g / cm 3 , 1.18g / cm 3 , 1.20g / cm 3 , 1.21g / cm 3 , 1.22g / cm 3 , 1.23g / cm 3 , 1.24g / cm 3 , 1.25g / cm 3 When the tap density of the carbon-based material in the second negative electrode film layer is within an appropriate range, the energy density of the battery cell can be increased.

[0443] In the embodiments of this application, the tap density of a material is a term generally known in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a powder tap density tester, as described in GB / T 5162-2006. A Dandong Better BT-301 can be used as the tester.

[0444] 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, or 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 consisting of any two of the foregoing values. By adjusting the thickness ratio of the first negative electrode film layer to the second negative electrode film layer, the gradient porosity difference between the upper and lower layers can be further increased, reducing the tortuosity of lithium ion transport and improving the fast charging capability of the battery cell.

[0445] In some embodiments, after the battery cell undergoes 10 full charge cycles in the Beginning of Life (BOL) test, 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 consisting of any two of the foregoing values. When the thickness of the first negative electrode film layer is within the foregoing range, the gradient porosity difference between the first and second negative electrode film layers can be increased, thereby reducing the tortuosity of lithium ion transport and improving the fast charging capability of the battery cell.

[0446] In some embodiments, after the battery cell undergoes 10 full charge cycles in the Beginning of Life (BOL) test, 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 consisting of any two of the foregoing values. When the thickness of the second negative electrode film layer is within the foregoing range, the gradient porosity difference between the first and second negative electrode film layers can be increased, thereby reducing the tortuosity of lithium ion transport and improving the fast charging capability of the battery cell.

[0447] In the embodiment of the present application, for example, the battery charging upper limit voltage is 3.65V and the battery discharging cut-off voltage is 2.0V.

[0448] The BOL full charge test steps are as follows: at 25°C, charge the battery to 3.65V at a charge rate of 0.33C of the nominal capacity, then charge it to 0.05C at a constant voltage of 3.65V, let it stand for 10 minutes, then discharge it to 2.0V at a discharge rate of 0.33C, let it stand for 10 minutes. The above charge and discharge is one cycle, and the cycle is 10 circles. Then charge it to 3.65V at a charge rate of 0.33C of the nominal capacity, and then charge it to 0.05C at a constant voltage of 3.65V. In the BOL fully charged state, the negative electrode sheet is disassembled, and a cross-section in the thickness direction of the middle area of ​​the negative electrode sheet is observed using a tomographic scanning electron microscope. The first negative electrode film layer and the second negative electrode film layer are distinguished according to the interface between the two areas, and the thickness of the two is measured respectively. For example, the thickness of 10 positions of the first negative electrode film layer is measured respectively, and the average value thereof is calculated as the average value of the first negative electrode film layer; the thickness of 10 positions of the second negative electrode film layer is measured, and the average value thereof is calculated as the average value of the second negative electrode film layer.

[0449] In some embodiments, after a battery cell undergoes an end-of-life (EOL) full charge test, 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, or 70 μm, or a range consisting of any two of the foregoing values. When the thickness of the first negative electrode film layer is within the foregoing range, the first and second negative electrode film layers can be controlled to increase the gradient porosity difference between the upper and lower layers, thereby reducing the tortuosity of lithium ion transmission and improving the fast charging capability of the battery cell.

[0450] In some embodiments, after a battery cell undergoes an end-of-life (EOL) full charge test, 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 consisting of any two of the foregoing values. When the thickness of the second negative electrode film layer is within the foregoing range, the first negative electrode film layer and the second negative electrode film layer can be controlled to increase the gradient porosity difference between the upper and lower layers, thereby reducing the tortuosity of lithium ion transmission and improving the fast charging capability of the battery cell.

[0451] In the embodiment of the present application, for example, the battery charging upper limit voltage is 3.65V and the battery discharging cut-off voltage is 2.0V.

[0452] The EOL full charge test steps are as follows: at 60°C, charge the battery to 3.65V at a charge rate of 0.33C of the nominal capacity, then charge it to 0.05C at a constant voltage of 3.65V, let it stand for 10 minutes, and then discharge it to 2.0V at a discharge rate of 0.33C, let it stand for 10 minutes. The above charge and discharge cycle is one cycle, and the test is stopped when the battery capacity decays to 80% of the nominal capacity. Then, at 25°C, charge to 3.65V at a constant current of 0.33C and charge to 3.65V at a constant voltage of 0.05C, which is the EOL fully charged state. In the EOL fully charged state, disassemble the negative electrode sheet, and use a tomographic scanning electron microscope to observe the cross-section in the thickness direction of the middle area of ​​the negative electrode sheet. The first negative electrode film layer and the second negative electrode film layer are distinguished according to the interface between the two areas, and the thickness of the two is measured respectively. For example, the thickness of 10 positions of the first negative electrode film layer is measured respectively, and the average value thereof is calculated as the average value of the first negative electrode film layer. The thickness of 10 positions of the second negative electrode film layer is measured, and the average value thereof is calculated as the average value of the second negative electrode film layer.

[0453] In some embodiments, when the negative electrode film layer adopts a single-layer film layer (as distinguished from the double-layer film layer described above), 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 consisting of any two of the above values. The lithium element in the lithium-containing binder can exist in the form of ions, which can increase the number of freely 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 rate of lithium ion insertion and extraction, and improve the fast charging performance of the battery cell. Optionally, the negative electrode film layer may 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 (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS).

[0454] Optionally, the mass content of lithium in the lithium-containing binder is 3% to 10%. Exemplarily, the mass content of lithium in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two of the above values. The mass content of lithium is calculated based on the mass of the lithium-containing binder. When the mass content of lithium is within the above range, the number of lithium ions that can freely move in the negative electrode film layer is relatively large, which can further shorten the distance that lithium ions diffuse to the surface of the negative electrode film layer, increase the deintercalation rate of lithium ions, and improve the fast charging performance of the battery cell.

[0455] Exemplarily, the lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a hydroxyethyl acrylate monomer, wherein the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 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 hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0456] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, thereby improving the fast charging performance of the battery cell. In addition, it is not easy to swell during the charging and discharging process and has a stable structure, thereby improving the cycle performance of the negative electrode film layer during the fast charging and discharging process.

[0457] In other embodiments, when the negative electrode film layer comprises at least two film layers, the negative electrode film layer further comprises a lithium-containing binder.

[0458] 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, wherein 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.

[0459] The mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides the second negative electrode film layer with a relatively larger number of freely movable lithium ions, which can further improve the fast charging performance of the battery cell.

[0460] 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 consisting of any two of the above values. The lithium element in the first lithium-containing binder can exist in ionic form, which can increase the number of freely mobile lithium ions in the negative electrode film layer, shorten the distance lithium ions diffuse to the surface of the negative electrode film layer, increase the lithium ion deintercalation rate, and improve the fast charging performance of the battery cell.

[0461] Optionally, the mass content of lithium in the first lithium-containing binder is 3% to 10%, optionally 3% to 8%. Exemplarily, the mass content of lithium in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two of the above values. When the mass content of lithium is within the above range, a relatively large number of lithium ions can freely move in the negative electrode film layer, further shortening the distance for lithium ions to diffuse to the surface of the negative electrode film layer, increasing the rate of lithium ion insertion and extraction, and improving the fast charging performance of the battery cell.

[0462] Illustratively, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a hydroxyethyl acrylate monomer, wherein the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 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 hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0463] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, thereby improving the fast charging performance of the battery cell. In addition, it is not easy to swell during the charging and discharging process and has a stable structure, thereby improving the cycle performance of the negative electrode film layer during the fast charging and discharging process.

[0464] 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 a range consisting of any two of the above values. The lithium element in the second lithium-containing binder can exist in ionic form, which can increase the number of freely mobile lithium ions in the negative electrode film layer, shorten the distance lithium ions diffuse to the surface of the negative electrode film layer, increase the lithium ion deintercalation rate, and improve the fast charging performance of the battery cell.

[0465] The first lithium-containing binder and the second lithium-containing binder may be made of the same material or different materials.

[0466] Optionally, the mass content of lithium in the second lithium-containing binder is 3% to 10%, optionally 3% to 8%. Exemplarily, the mass content of lithium in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two of the above values. When the mass content of lithium is within the above range, the number of lithium ions that can freely move in the negative electrode film layer is relatively large, which can further shorten the distance that lithium ions diffuse to the surface of the negative electrode film layer, increase the rate of lithium ion insertion and extraction, and improve the fast charging performance of the battery cell.

[0467] Exemplarily, the second lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from a lithium acrylate monomer, an acrylonitrile monomer, an acrylamide monomer, and a hydroxyethyl acrylate monomer, wherein the molar ratio of the lithium acrylate monomer, the acrylonitrile monomer, the acrylamide monomer, and the 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 hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0468] The lithium-containing binder of the above material can provide a certain amount of lithium ions for the negative electrode film layer, thereby improving the fast charging performance of the battery cell. In addition, it is not easy to swell during the charging and discharging process and has a stable structure, thereby improving the cycle performance of the negative electrode film layer during the fast charging and discharging process.

[0469] 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), a water-soluble unsaturated resin SR-1B, a 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).

[0470] 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.

[0471] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of negative electrode conductive agent. For 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, the weight content of the negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0472] In some embodiments, the negative electrode film layer may further include a negative electrode binder. In some embodiments, the negative electrode binder has a mass content of ≤5% based on the total weight of the negative electrode film layer.

[0473] In some embodiments, the negative electrode film layer may also optionally include other additives. Examples of these additives include thickeners, dispersants, and the like, such as sodium carboxymethylcellulose (CMC-Na) and PTC thermistor materials. In some embodiments, the weight content of these additives is ≤ 2% based on the total weight of the negative electrode film layer.

[0474] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0475] In some embodiments, the thickness of the negative electrode current collector is 4 μm to 10 μm, optionally 4 μm to 6 μm. For example, 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 consisting of any two of the above values.

[0476] When the thickness of the negative electrode current collecting portion is within the above range, the negative electrode current collecting portion has a relatively excellent current flow capacity and can enable the battery cell to have a relatively high energy density.

[0477] In the embodiment of the present application, the thickness of the negative electrode current collector has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, a solvent is used to wash away the film layer on the surface of the negative electrode current collector, and the thickness of the negative electrode current collector is measured with a micrometer.

[0478] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0479] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a negative conductive layer sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0480] In some embodiments, the negative electrode plate further includes a negative electrode conductive layer, which is located between the negative electrode film layer and the negative electrode current collector. The negative electrode conductive layer can further improve the conductivity of the negative electrode plate, reduce the heat generated by the negative electrode plate, and thus reduce the heat generated by the battery cell.

[0481] In some embodiments, the thickness of the negative electrode conductive layer is 0.5 μm to 2 μm. For example, 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 consisting of any two of the above values.

[0482] When the thickness of the negative electrode conductive layer is within the above range, the conductivity of the negative electrode sheet can be further improved, the heat generation of the negative electrode sheet can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can be improved.

[0483] In the embodiment of the present application, the thickness of the negative electrode conductive layer has a meaning well known in the art and can be detected using equipment and methods well known in the art, and the test method for the negative electrode conductive layer mentioned above can be used.

[0484] 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 pole piece 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 and the negative electrode film layer, thereby improving the structural stability of the negative electrode pole piece.

[0485] In some embodiments, the negative electrode conductive layer may further include other additives, such as thickeners, sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0486] 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 consisting of any two of the above values.

[0487] Illustratively, 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.

[0488] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%, illustratively 60%, 65%, 70%, 75%, 80%, or a range consisting of any two of the above values.

[0489] Illustratively, the negative electrode binder includes one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0490] In some embodiments, the ratio CB of the capacity per unit area of ​​the negative electrode film layer to the capacity per unit area of ​​the positive electrode film layer in the battery cell is 1.05 to 1.30, and can optionally be 1.07 to 1.15. For example, the ratio CB of the capacity per unit area of ​​the negative electrode film layer to the capacity per unit area of ​​the positive electrode film layer 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 consisting of any two of the foregoing values.

[0491] When the ratio CB of the capacity per unit area of ​​the negative electrode film layer to the capacity per unit area of ​​the positive electrode film layer in the battery cell is within the above range, there are sufficient sites in the negative electrode film layer for lithium embedding, which can reduce the risk of lithium plating and is conducive to fast charging.

[0492] In the embodiment of the present application, the CB value has a well-known meaning in the art and can be detected using equipment and methods well-known in the art. For example, the capacity per unit area of ​​the negative electrode film layer and the capacity per unit area of ​​the positive electrode film layer are calculated respectively, and the ratio of the two is calculated to obtain the CB value.

[0493] Specifically, take the battery charging upper limit voltage as 3.65V and the battery discharging cut-off voltage as 2.0V as an example for explanation.

[0494] The capacity per unit area of ​​the positive electrode film layer refers to the actual lithium-removable capacity of the positive electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the positive electrode sheet is removed, and assembled into a CR2430 model semi-button battery with a positive electrode-lithium sheet. The area of ​​the positive electrode sheet used is amm 2 The electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC=3 / 5 / 2 (mass ratio), and then the assembled half-button battery is left to stand for 3 hours. The test is carried out at 25°C, and 0.1C is used to charge (Charge) in the voltage range of 2.0V to 3.65V to delithiate, and then 0.05C is used to discharge (Discharge) lithium to 2.0V, and the cycle is repeated twice. The discharge capacity of the second cycle is recorded as YmAh. The positive electrode sheet of the actual battery design is bmm long and cmm wide. The number of surfaces of the positive electrode active material coated on the positive electrode current collector is d. Then the capacity of the positive electrode film layer per unit area = Y / a*b*c*d.

[0495] Specifically, the capacity per unit area of ​​the negative electrode film layer refers to the actual lithium-insertable capacity of the negative electrode active material. The test method is as follows: disassemble the battery in a PRS340 / 11-119-11 Braun glove box, remove the negative electrode plate, and assemble it into a CR2430 model semi-button battery with a negative electrode-lithium plate. The area of ​​the negative electrode plate used is fmm 2 , where the electrolyte uses a solution of 1 mol / L LiPF6 in EC / EMC / DEC=3 / 5 / 2 (mass ratio), and then the assembled half-button battery is left to stand for 3 hours. The test is carried out at 25°C, and 0.1C is used to discharge (Discharge) in the voltage range of 2V-0V to insert lithium, and then 0.05C is used to charge (Discharge) to 2V for lithium removal, and the cycle is repeated twice. The discharge capacity of the second cycle is recorded as ZmAh. The actual battery design has a negative electrode sheet length of hmm and a width of imm. The number of surfaces of the negative electrode active material coated on the negative electrode current collector is d, then the negative electrode lithium insertion capacity = Z / f*h*i*d.

[0496] [Isolation film]

[0497] In the embodiment of the present application, the isolation membrane includes a base membrane with a porous structure.

[0498] In some embodiments, the base film comprises at least one of glass fiber, non-woven fabric, and polyolefin. The base film may be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0499] Optionally, the polyolefin includes at least one of polyethylene, polypropylene and polyvinylidene fluoride.

[0500] In some embodiments, the porosity of the base film is 20% to 70%, optionally 35% to 60%. Exemplarily, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range consisting of any two of the above values.

[0501] In the embodiment of the present application, when the porosity of the base film is within the above range, the migration ability of lithium ions in the separator can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0502] In the embodiments of this application, porosity refers to the percentage of the pore volume within the separator to the total volume of the separator. Porosity can be tested in accordance with the standard GB / T36363-2018, "Polyolefin Separators for Battery Cells." It should be noted that the actual testing process may vary slightly from the standard to obtain a more accurate test value, depending on instrument differences, test errors, and to minimize the impact of porosity testing.

[0503] In some embodiments, the base film has a thickness of 6 μm to 12 μm, optionally 6 μm to 9 μm. For example, the base film has a thickness of 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 a range consisting of any two of the above values.

[0504] 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.

[0505] In the embodiment of the present application, the isolation membrane may be a base membrane. Optionally, the isolation membrane further includes a functional layer disposed on at least one side of the base membrane. The functional layer may include inorganic particles to enhance the heat resistance of the isolation membrane. Optionally, the functional layer is disposed on both sides of the base membrane.

[0506] 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, the first functional layer includes first inorganic particles, the second functional layer is located on the other side of the base film, the second functional layer includes composite particles, the composite particles include second inorganic particles and multiple 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.

[0507] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the isolation film.

[0508] Optionally, the first functional layer may include a binder, optionally including at least one of a fluorine-containing binder or a polyacrylic binder, such as polyvinylidene fluoride.

[0509] 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 first inorganic particles can improve the heat resistance of the first functional layer.

[0510] In the embodiments of the present application, the thickness of the base film has a meaning well known in the art, and can be tested using the meanings and equipment well known in the art. For example, a newly prepared isolation membrane can be taken as a sample, or a battery cell that has been discharged (discharged to the lower cut-off voltage so that the battery's charged state is approximately 0% SOC) can be reversely disassembled, and the isolation membrane can be obtained from the battery cell. The isolation membrane is dried and used as a sample, and the isolation membrane is cut with 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 isolation membrane and its various layers.

[0511] The non-fluorinated polymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluorinated polymer particles include an acrylic copolymer. Optionally, the acrylic copolymer includes an acrylate-acrylonitrile-acrylamide-propylene copolymer. Acrylic copolymers have excellent bonding properties and high bonding stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as 35%:30%:15%:20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0512] 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, so that the composite particles have pores, which is conducive to the transmission of lithium ions and improves the ion conductivity of the separator. 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 more stable, which can improve the dynamic performance of the battery cell and improve the fast charging performance. Optionally, compared to the first functional layer, the second functional layer is arranged close to the negative electrode sheet. Since the composite particles are not easily deformed, the separator basically does not cause side effects such as extrusion on the negative electrode sheet, which stabilizes the dynamic performance of the negative electrode sheet. Accordingly, the first functional layer is arranged close to the positive electrode sheet.

[0513] 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. These second inorganic particles can enhance the heat resistance of the second functional layer and can form composite particles with non-fluoropolymers to further improve the cycle stability and dynamic performance of the separator, thereby improving the cycle performance and fast charging performance of the battery cell.

[0514] The average particle size of the second inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, 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 consisting 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.

[0515] In the embodiment of the present application, the average particle size of the second inorganic particles has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, after obtaining the isolation film and drying the isolation film as a sample, the isolation film is cut with 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 isolation film. The particle sizes of multiple, for example, 50, second inorganic particles are measured, and the average value is calculated as the average particle size of the second inorganic particles.

[0516] In some embodiments, the ionic conductivity of the separator is 0.3 mS / cm to 0.6 mS / cm. For example, 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 consisting of any two of the foregoing values.

[0517] 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, thereby improving the fast charging performance of the battery cell.

[0518] In the embodiments of the present application, the ionic conductivity of the isolation membrane has a meaning known in the art and can be detected using equipment and methods known in the art, for example,

[0519] Preparation of 2025 button cells for testing: In a vacuum glove box, a lithium sheet was placed in the negative electrode shell of the battery, and 150 μL of electrolyte was added thereto. The electrolyte was a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio). Then, an isolation membrane (area of ​​3.14 cm) was placed in the negative electrode shell of the battery. 2 , 12μm thick) to ensure close contact with the lithium sheet. 25μL of electrolyte was then added. Finally, a positive electrode sheet (the one described in Example 1 can be used) was placed on top and packaged. The assembled button cell was removed from the vacuum glove box and allowed to rest for 24 hours before the next test.

[0520] Test: On an electrochemical workstation, at 10 -1 ~10 6 The test is carried out in the frequency range of Hz to obtain the isolation membrane resistance Rb, and the ionic conductivity σ (unit: mS / cm) is calculated by the following formula:

[0521] σ=L / (R b ×S)

[0522] Where: R b is the isolation film resistance, L and S are the thickness and area of ​​the isolation film to be measured respectively.

[0523] [Electrolyte]

[0524] In some embodiments, the battery cell further includes an electrolyte.

[0525] During the charge and discharge process of a battery cell, active ions such as lithium ions are embedded and released back and forth between the positive electrode and the negative electrode, and the electrolyte plays the role of conducting active ions between the positive electrode and the negative electrode.

[0526] In an embodiment 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 may be 15 mS / cm to 20 mS / cm. For example, 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 a range consisting of any two of the above values.

[0527] When the conductivity of the electrolyte at room temperature is within the above range, the migration rate of lithium ions in the electrolyte is 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.

[0528] In the embodiment of the present application, the conductivity of the electrolyte at room temperature is ionic conductivity, which can be tested using equipment and methods known in the art, for example, by referring to the industry standard HG-T 4067-2015.

[0529] In some embodiments, the viscosity of the electrolyte at room temperature, such as 25° C., is 2.3 mPa·s to 3.5 mPa·s. For example, 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 consisting of any two of the foregoing values.

[0530] When the viscosity of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is 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.

[0531] In the embodiments of the present application, the viscosity of the electrolyte has a well-known meaning in the art and can be detected using equipment and methods well-known in the art, for example, it can be detected according to GB / T10247-2008.

[0532] In some embodiments, the density of the electrolyte at room temperature, e.g., 25° C., is between 1.05 g / mL and 1.35 g / mL. For example, 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 consisting of any two of the foregoing values.

[0533] When the density of the electrolyte is within the above range, the migration rate of lithium ions in the electrolyte is 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.

[0534] In the embodiments of the present application, the density of the electrolyte has a well-known meaning in the art and can be tested using equipment and methods well-known in the art, for example, by referring to GB / T 2013-2010.

[0535] The electrolyte includes an organic solvent and an electrolyte salt. The types of the organic solvent and the electrolyte salt are not particularly limited and can be selected according to actual needs.

[0536] In some embodiments, the organic solvent includes a linear carboxylate solvent, and the weight content of the linear carboxylate solvent in the electrolyte is 6% to 65%, and optionally 25% to 60%. Illustratively, the weight content of the linear carboxylate solvent is 6%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or a range consisting of any two of the foregoing values.

[0537] 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.

[0538] In some embodiments, the linear carboxylate solvent includes a compound represented by Formula I,

[0539] Formula I,

[0540] In Formula I,

[0541] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group,

[0542] R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

[0543] The above-mentioned chain carboxylic acid ester solvents have high electrical conductivity, which is beneficial to improving the fast charging capability of battery cells.

[0544] Alternatively, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group. Further alternatively, R1 includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a C1 to C2 haloalkyl group.

[0545] Alternatively, R2 comprises a C1 to C3 alkyl group or a C1 to C3 haloalkyl group. Further alternatively, R2 comprises a C1 to C2 alkyl group or a C1 to C2 haloalkyl group.

[0546] 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.

[0547] In each of 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.

[0548] Illustratively, the chain carboxylate solvent includes one or more compounds represented by formula I-1 to formula I-8.

[0549]

[0550] In some embodiments, the organic solvent further includes a carbonate solvent.

[0551] 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 use of the above carbonate solvent and the chain carboxylate solvent in combination improves the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0552] Further optionally, the mass content of the carbonate solvent in the electrolyte is 20% to 80%, optionally 25.5% to 42.5%. For example, 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 consisting of any two of the above values. The above mass content of carbonate solvent can further improve the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0553] Illustratively, 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%.

[0554] In some embodiments, the electrolyte further contains additives, which may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature power performance, etc.

[0555] In some embodiments, the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives, and optionally at least two of these additives. These additives can improve the interfacial film properties on the positive and / or negative electrode sides, thereby enhancing the fast charging performance of the battery cells and improving the cycling performance.

[0556] In some embodiments, the weight content of the additive in the electrolyte is 1% to 10%, optionally 2% to 8%, and further optionally 3.5% to 8%. For example, the weight content of the additive in the electrolyte is 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two of the above values.

[0557] The additives in 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.

[0558] Illustratively, the carbonate additive includes one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0559] For example, the sulfur-containing additive includes one or more of vinyl sulfate DTD, vinyl disulfate 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, vinyl sulfite ES, and methylene disulfonate MMDS.

[0560] Optionally, the lithium salt additive includes one or more of lithium difluorophosphate LiPO2F2, lithium difluorooxalatoborate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bis(oxalatoborate) LiBOB.

[0561] Optionally, the mass content of vinylene carbonate VC in the electrolyte is 0.5% to 9%, optionally 2% to 6%.

[0562] Optionally, the mass content of fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%, and optionally 0.5% to 3%.

[0563] 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%.

[0564] 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%.

[0565] In some embodiments, the electrolyte salt includes a lithium salt, which includes one or more of a fluorinated sulfonyl imide salt and lithium hexafluorophosphate (LiPF6). These lithium salts are easily dissociated, facilitating rapid lithium ion migration. Furthermore, the electrolyte system is relatively stable and resistant to decomposition, thereby improving the cycling performance of the battery cell.

[0566] Optionally, the fluorine-containing sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide LiFSI and lithium bis(trifluoromethanesulfonyl)imide LiTFSI.

[0567] 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.

[0568] Illustratively, 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.

[0569] For example, 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.

[0570] For example, 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.

[0571] Optionally, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.2 to 1.0, and optionally 0.2 to 0.5. Exemplarily, the ratio of the molar concentration of lithium bis(fluorosulfonyl)imide to the molar concentration of lithium hexafluorophosphate (LiPF6) is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range consisting of any two of the foregoing values.

[0572] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt concentrations in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the inorganic components / lithium salt concentrations in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis methods in accordance with the standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods". In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, the 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 battery's state of charge is approximately 0% SOC) can be reversely disassembled, and the free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography analysis methods.

[0573] In the embodiments of the present application, the types and contents of organic components in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, qualitative and quantitative analysis of organic components in the electrolyte can be performed by gas chromatography with reference to GB / T9722-2006, "General Rules for Gas Chromatography of Chemical Reagents." In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, free electrolyte from a fresh battery can be taken as a sample, or a battery that has been fully discharged (discharged to the lower cutoff voltage so that the battery's state of charge is approximately 0%) can be disassembled in reverse, and free electrolyte obtained from the battery can be used as a sample for detection using ion chromatography.

[0574] In the embodiment of the present application, after quantitative and qualitative detection of each component in the electrolyte, the components are classified, and the chain carboxylate solvent and carbonate solvent (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate) are used as components of the organic solvent. The mass content of each component is calculated based on the mass of the electrolyte as 100%.

[0575] Carbonate additives (such as vinylene carbonate, fluoroethylene carbonate), sulfur-containing additives and lithium salt additives are used as additives for the electrolyte. The mass content of each component is calculated based on the mass of the electrolyte being 100%.

[0576] In some embodiments, the battery cell satisfies the following conditions: 2.45g / Ah ≤ d / A ≤ 3.5g / Ah, optionally 2.45g / Ah ≤ d / A ≤ 3.3g / 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. For example, d / A can be 3.5g / Ah, 3.3g / Ah, 3.2g / Ah, 3.0g / Ah, 2.8g / Ah, 2.5g / Ah, 2.45g / Ah, or a range consisting of any two of the foregoing values.

[0577] d / A can reflect the electrolyte's ability to retain liquid. When d / A is within the above range, the electrolyte can better wet the positive and negative electrodes, and can increase the migration rate of lithium ions in the liquid phase, which is beneficial to improving the fast charging capability of the battery cell.

[0578] In the embodiment of the present application, the d / A of the battery cell can be understood as the liquid retention coefficient, which can be tested using equipment and methods known in the art. For example, it can be described in accordance with GB / T31486-2015 "Electrical Performance Requirements and Test Methods for Power Batteries for Electric Vehicles", taking the battery charging upper limit voltage of 3.65V and the battery discharge cut-off voltage of 2.0V as an example.

[0579] At 25°C, charge a battery cell at 0.33C to 3.65V, then charge it at a constant voltage to 0.05C, and then discharge it at a constant current of 0.33C to 2.0V. The discharged capacity A is used as the denominator, and the battery cell is weighed as M0. The positive electrode sheet, negative electrode sheet, separator, and electrolyte, with the free electrolyte contained in a bag, are then disassembled and baked in a 60°C oven for at least 4 hours (including but not limited to the positive electrode sheet, negative electrode sheet, separator, and other mechanical parts of the disassembled battery cell that contribute to M0). The total weight of the battery cell is then weighed as M1, with the weight difference between M0 and M1 as the numerator. The liquid retention coefficient is equal to the weight difference d between M0 and M1 divided by the capacity A.

[0580] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process and / or a lamination process.

[0581] like Figure 24 As shown, in some embodiments of the present application, the battery cells 7 according to the embodiments of the present application can be assembled into a battery module 6. The number of battery cells 7 contained 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.

[0582] If there are multiple battery cells 7, they can be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections within the battery cells 7. Multiple battery cells 7 can be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 7 is housed within the housing of the battery module 6. Alternatively, multiple battery cells 7 can be first connected in series, in parallel, or in a hybrid connection to form a battery module 6, and then the battery modules 6 are further connected in series, in parallel, or in a hybrid connection to form a single unit and housed within the housing. Optionally, the battery module 6 may further include a housing portion having a storage space, and the multiple battery cells 7 are housed within the storage space.

[0583] In some embodiments, the battery device may include a first bus bar 61 and a second bus bar 62 , wherein the first bus bar 61 is used to electrically connect the first electrode terminals, and the second bus bar 62 is used to electrically connect the second electrode terminals.

[0584] like Figure 25 As shown, in some embodiments, the battery modules 6 can also be assembled into a battery pack 2. The number of battery modules 6 contained in the battery pack 2 can be adjusted according to the application and capacity of the battery pack. The battery device herein can be a battery module 6 or a battery pack 2.

[0585] The battery pack 2 may include a housing 5 and a plurality of battery modules 6 disposed within the housing 5. The housing 5 includes a first housing portion 5a and a second housing portion 5b. The housing 5 defines a receiving space 5c. The first housing portion 5a covers the second housing portion 5b and forms an enclosed space for receiving the battery modules 6. The plurality of battery modules 6 may be arranged in any manner within the housing 5.

[0586] The first housing portion 5a and the second housing portion 5b overlap each other, and together they define a storage space 5c for accommodating the battery cells. The second housing portion 5b can be a hollow structure with one end open. The first housing portion 5a is a plate-like structure, and the first housing portion 5a overlaps the open side of the second housing portion 5b to form the housing 5 with the storage space 5c. Alternatively, both the first housing portion 5a and the second housing portion 5b can be hollow structures with one end open, and the open side of the first housing portion 5a overlaps the open side of the second housing portion 5b to form the housing 5 with the storage space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0587] In order to improve the sealing performance after the first box body portion 5a and the second box body portion 5b are connected, a sealing member, such as a sealant, a sealing ring, etc., may also be provided between the first box body portion 5a and the second box body portion 5b.

[0588] Assuming that the first box portion 5a covers the top of the second box portion 5b, the first box portion 5a can also be called an upper box cover, and the second box portion 5b can also be called a lower box.

[0589] 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% state of charge (SOC), the temperature of the external environment of the battery pack 2 is, for example, room temperature, 30°C.

[0590] In some embodiments, during the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge (SOC) to 80% state of charge (SOC), the temperature of the external environment of the battery pack 2 is 30° C.

[0591] In some embodiments, the charging process of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge to 80% state of charge includes multiple charging steps, and 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% state of charge, such as 1% state of charge, 1.5% state of charge, 2% state of charge, 2.5% state of charge, 3% state of charge, 3.5% state of charge, 4% state of charge, 4.5% state of charge, 5% state of charge, or a range consisting of any two of the above values.

[0592] The battery pack 2 or any battery cell constituting the battery pack 2 includes multiple charging steps from a 10% state of charge to a 40% state of charge. 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 of 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a value in the range consisting of any two of the above values.

[0593] For example, the charging step of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% to 80% can be performed as follows:

[0594] Charge from 10% SOC to 15% SOC at 5.0C constant current.

[0595] Charge from 15% SOC to 20% SOC at 5.0C constant current.

[0596] Charge from 20% SOC to 25% SOC at 5.0C constant current.

[0597] Charge from 25% SOC to 30% SOC at 5.0C constant current.

[0598] Charge from 30% SOC to 35% SOC at 5.0C constant current.

[0599] Charge from 35% SOC to 40% SOC at 5.0C constant current.

[0600] Charge from 40% SOC to 45% SOC at 4.6C constant current.

[0601] Charge from 45% SOC to 50% SOC at 4.3C constant current.

[0602] Charge from 50% SOC to 55% SOC at 4.0C constant current.

[0603] Charge from 55% SOC to 60% SOC at 3.7C constant current.

[0604] Charge from 60% SOC to 65% SOC at 3.4C constant current.

[0605] Charge from 65% SOC to 70% SOC at 3.1C constant current.

[0606] Charge from 70% SOC to 75% SOC at 2.9C constant current.

[0607] Charge from 75% SOC to 80% SOC at 2.7C constant current.

[0608] 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 minutes, and can be optionally 5 minutes to 10.5 minutes. The temperature of the external environment of the battery pack 2 at 10% state of charge is, for example, room temperature of 30° C. Exemplarily, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 10.5 minutes, 10 minutes, 9.5 minutes, 9 minutes, 8.5 minutes, 8 minutes, 7.5 minutes, 7 minutes, 6.5 minutes, 6 minutes, 5.5 minutes, 5 minutes, or a range consisting of any two of the above values.

[0609] In some embodiments, the volumetric energy density of the battery cell is 390Wh / L to 500Wh / L, optionally 410Wh / L to 470Wh / L. For example, the volumetric energy density of the battery cell is 390Wh / L, 400Wh / L, 410Wh / L, 420Wh / L, 430Wh / L, 440Wh / L, 450Wh / L, 460Wh / L, 470Wh / L, 480Wh / L, 490Wh / L, 500Wh / L, or a range consisting of any two of the foregoing values. The volumetric energy density of the battery cell is relatively high.

[0610] In the embodiments of the present application, the volume energy density of a battery cell has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, the battery charging upper limit voltage is 3.65V and the battery discharge cut-off voltage is 2.0V.

[0611] Place the battery cell at 25°C, charge at a constant current of 0.33C to 3.65V, then charge at a constant voltage to 0.05C, and discharge at a constant current of 0.33C to 2.0V. Record the discharge capacity A0 at this time, unit: Ah. Use calipers to measure the length, width, and height of the battery cell (generally calculated based on the battery casing size, excluding the electrode terminal height and the insulating film outside the casing), calculate the volume of the single battery V0, unit L, and the volume energy density of the battery cell VED = (A0 × discharge platform voltage) / V0, unit Wh / L.

[0612] In some embodiments, the battery cell has a gravimetric energy density of 175 Wh / Kg to 210 Wh / Kg. For example, the gravimetric 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 a range consisting of any two of these values. The volumetric energy density of the battery cell is relatively high.

[0613] In the embodiments of the present application, the weight energy density of a battery cell has a meaning well known in the art and can be detected using equipment and methods well known in the art. For example, the battery charging upper limit voltage is 3.65V and the battery discharge cut-off voltage is 2.0V.

[0614] Place the battery cell at 25°C, charge it to 3.65V at a constant current of 0.33C, and then charge it to 0.05C at a constant voltage; discharge it to 2.0V at a constant current of 0.33C, and record the discharge capacity A0 at this time, in Ah; use a card to measure the mass of the electrode assembly in the battery cell and calculate the weight energy density of the battery cell, in Wh / Kg.

[0615] Electrical devices

[0616] According to a second aspect of the embodiments of the present application, there is provided an electrical device, which includes a battery device according to the embodiments of the present application, such as a battery cell, a battery module, or a battery pack. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for 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, 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 vehicle, or an extended-range vehicle. The spacecraft includes an airplane, a rocket, a space shuttle, and a spacecraft. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool, and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator, and an electric planer. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0617] The electrical device can select battery cells, battery modules or battery packs according to its usage requirements.

[0618] Figure 26 1 is a schematic diagram of an exemplary electric device 1. The electric device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device 1, a battery pack or battery module may be used.

[0619] A battery pack 2 is disposed within the electrical device 1. The battery pack 2 can be located at the bottom, top, or rear of the electrical device 1. The battery pack 2 can be used to power the electrical device 1. For example, the battery pack 2 can serve as the operating power source of the electrical device 1 or 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.

[0620] The electric 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, to meet the power requirements of the electric device 1 during startup, navigation, and driving.

[0621] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0622] The following charging methods can be selected for the charging process of the electrical device:

[0623] Charge from 10% SOC to 15% SOC at 5.0C constant current.

[0624] Charge from 15% SOC to 20% SOC at 5.0C constant current.

[0625] Charge from 20% SOC to 25% SOC at 5.0C constant current.

[0626] Charge from 25% SOC to 30% SOC at 5.0C constant current.

[0627] Charge from 30% SOC to 35% SOC at 5.0C constant current.

[0628] Charge from 35% SOC to 40% SOC at 5.0C constant current.

[0629] Charge from 40% SOC to 45% SOC at 4.6C constant current.

[0630] Charge from 45% SOC to 50% SOC at 4.3C constant current.

[0631] Charge from 50% SOC to 55% SOC at 4.0C constant current.

[0632] Charge from 55% SOC to 60% SOC at 3.7C constant current.

[0633] Charge from 60% SOC to 65% SOC at 3.4C constant current.

[0634] Charge from 65% SOC to 70% SOC at 3.1C constant current.

[0635] Charge from 70% SOC to 75% SOC at 2.9C constant current.

[0636] Charge from 75% SOC to 80% SOC at 2.7C constant current.

[0637] In some embodiments, the charging time of the electric device from 10% state of charge to 80% state of charge is less than or equal to 10.5 minutes, and can be optionally 5 minutes to 10.5 minutes. The ambient temperature 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 minutes, 10 minutes, 9.5 minutes, 9 minutes, 8.5 minutes, 8 minutes, 7.5 minutes, 7 minutes, 6.5 minutes, 6 minutes, 5.5 minutes, 5 minutes, or a range consisting of any two of the above values.

[0638] Example

[0639] The following examples describe the disclosure of the present invention in more detail. These examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0640] Example 1-1

[0641] 1. Preparation of positive electrode sheet

[0642] The positive electrode sheet includes a positive current collecting part, a positive conductive layer on the positive current collecting part and a positive film layer. The positive current collecting part is an aluminum foil with the same thickness as the positive electrode tab. The positive conductive layer on the positive current collecting part is a film layer formed by mixing the positive conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride (PVDF) and the solvent N-methylpyrrolidone NMP evenly and then coating it on the surface of the current collecting part. The thickness is 1μm. 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%.

[0643] The positive electrode film layer includes a positive electrode slurry (the solvent is N-methylpyrrolidone NMP) uniformly coated on the surface of the positive electrode conductive layer, and a film layer formed after drying and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF) and a conductive agent acetylene black in a weight ratio of 97:2:1.

[0644] The positive electrode active material includes lithium iron phosphate and a coating layer, which is coated on the surface of the lithium iron phosphate and includes lithium iron titanium phosphate (Li2FeTi(PO4)3) and amorphous carbon. The Dv50 of the positive electrode active material is 1.6μm and the Dv10 is 0.64μm.

[0645] The single-sided coating weight of the positive electrode film is 290mg / 1540.25mm 2 .

[0646] 2. Preparation of negative electrode sheet

[0647] The negative electrode sheet includes a negative electrode current collector, a negative electrode conductive layer on the negative electrode current collector, and a negative electrode film layer. The negative electrode current collector is a copper foil with the same thickness as the negative electrode tab. The negative electrode conductive layer on the negative electrode current collector is a film layer formed by uniformly mixing a negative electrode conductive agent, superconducting carbon, a negative electrode binder, styrene-butadiene rubber (SBR), a thickener, sodium carboxymethyl cellulose (CMC-Na), and solvent water, and then coating the mixture on the surface of the negative electrode current collector. The thickness is 1 μm. The mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0648] The negative electrode film layer includes a film layer formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode conductive layer, drying, and cold pressing.

[0649] The single-sided coating weight of the negative electrode film is 135mg / 1540.25mm 2 .

[0650] 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 electrode conductive layer, and the second negative electrode film layer is located on the surface of the first negative electrode film layer.

[0651] The first negative electrode film layer includes graphite particles in a mass ratio of 96.5:0.5:0.5:1.5:1, a conductive agent acetylene black, a first lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer), a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose; the mass content of lithium element in the first lithium-containing binder is 4.8%; the Dv50 of the graphite particles is 11.3μm, and the graphite particles include artificial graphite and an amorphous carbon layer. The amorphous carbon layer is coated on the surface of the artificial graphite, and the mass content of the amorphous carbon is 3.5%.

[0652] The second negative electrode film layer includes graphite particles in a mass ratio of 97.5:0.5:0.5:0.5:1, a conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer), a negative electrode binder styrene-butadiene rubber, and a thickener sodium carboxymethyl cellulose; the mass content of lithium element in the second lithium-containing binder is 4.8%; the Dv50 of the graphite particles is 11.3μm, and the graphite particles include artificial graphite and an amorphous carbon layer. The amorphous carbon layer is coated on the surface of the artificial graphite, and the mass content of amorphous carbon is 3.5%.

[0653] 3. Isolation film

[0654] The isolation film includes a base film, which is a 7 μm polyethylene film layer with a porosity of 42%.

[0655] 4. Preparation of electrolyte

[0656] The electrolyte includes an organic solvent, lithium salt and additives.

[0657] The organic solvent includes 48.5% of a chain carboxylate solvent (ethyl acetate) and 32.5% of a carbonate solvent (24.5% of ethylene carbonate EC, 8% of dimethyl carbonate). The mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0658] Based on the mass of the electrolyte, the mass content of the additive is 6.5%, which includes vinylene carbonate VC, fluoroethylene carbonate FEC, vinyl sulfite ES and lithium difluorooxalatoborate LiDFOB in a mass ratio of 5:0.5:0.5:0.5.

[0659] The lithium salt includes 1 mol / L lithium hexafluorophosphate LiPF6.

[0660] The conductivity of the electrolyte at room temperature is 16.4 mS / cm.

[0661] 5. Preparation of battery cells

[0662] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation. The electrode assembly is obtained through a winding process. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, and shaping, a battery cell is obtained. The compaction density of the positive electrode film layer at 100% SOC is 2.60 / cm 3 The compaction density of the negative electrode film at 100% SOC is 1.25g / cm 3 .

[0663] Comparative Example 1-1

[0664] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the projected area of ​​the positive terminal and the projected area of ​​the negative terminal were adjusted.

[0665] Example 1-2 to Example 1-8

[0666] A battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 was that the size of the weld print area and the weld print position were adjusted.

[0667] The specific parameters of the embodiments and comparative examples are shown in Table 1 and Table 2.

[0668] Performance Testing

[0669] 1. Lithium deposition area test of battery cells

[0670] At 60°C, the battery cell was charged at a constant current of 1C to a charge cut-off voltage of 3.65V, and then discharged at a constant current of 1C to 2.0V. This was a charge and discharge cycle. After 200 cycles, the battery was fully charged to 100% SOC according to the corresponding charging strategy. The negative electrode in the battery pack was disassembled, the negative electrode was unfolded, the decomposition area (gray-white area) was observed, and the decomposition area was measured.

[0671] 2. Number of cycles of battery cells until SOH reaches 70%

[0672] At 30°C, charge and discharge the battery cells repeatedly until the cycle capacity retention (Cn / C0 × 100%) reaches 70%. Record the number of cycles. A higher number of cycles indicates better cycling performance.

[0673] The charging process includes the following steps:

[0674] Charge from 0% SOC to 5% SOC at 5.0C constant current;

[0675] Charge from 5% SOC to 10% SOC at 5.0C constant current;

[0676] Charge from 10% SOC to 15% SOC at 5.0C constant current;

[0677] Charge from 15% SOC to 20% SOC at 5.0C constant current;

[0678] Charge from 20% SOC to 25% SOC at 5.0C constant current;

[0679] Charge from 25% SOC to 30% SOC at 5.0C constant current;

[0680] Charge from 30% SOC to 35% SOC at 5.0C constant current;

[0681] Charge from 35% SOC to 40% SOC at 5.0C constant current;

[0682] Charge from 40% SOC to 45% SOC at 4.6C constant current;

[0683] Charge from 45% SOC to 50% SOC at 4.3C constant current;

[0684] Charge from 50% SOC to 55% SOC at 4.0C constant current;

[0685] Charge from 55% SOC to 60% SOC at 3.7C constant current;

[0686] Charge from 60% SOC to 65% SOC at 3.4C constant current;

[0687] Charge from 65% SOC to 70% SOC at 3.1C constant current;

[0688] Charge from 70% SOC to 75% SOC at 2.9C constant current;

[0689] Charge from 75% SOC to 80% SOC at 2.7C constant current;

[0690] Charge from 80% SOC to 85% SOC at 1.8C constant current;

[0691] Charge from 85% SOC to 90% SOC at 1.3C constant current;

[0692] Charge from 90% SOC to 95% SOC at 0.7C constant current;

[0693] Charge from 95% SOC to 98% SOC at 0.33C constant current;

[0694] Charge from 98% SOC to 100% SOC at 0.1C constant current.

[0695] The cut-off voltage of the last charging step in the above charging steps is 3.65V.

[0696] The discharge strategy is as follows: discharge at a constant current of 0.33C to a cut-off voltage, for example, 2.0V.

[0697] The test results are shown in Table 3.

[0698] Table 1

[0699]

[0700] In Table 1, L1 represents the distance between the projection of the weld mark area between the positive electrode adapter and the positive electrode tab along the thickness direction of the positive terminal and the projection of the weld mark area between the positive terminal and the positive bus bar along the thickness direction of the positive terminal.

[0701] Table 2

[0702]

[0703] In Table 2, L1 represents the distance between the projection of the weld mark area between the negative electrode adapter and the negative electrode tab along the thickness direction of the negative terminal and the projection of the weld mark area between the negative terminal and the negative bus bar along the thickness direction of the negative terminal.

[0704] Table 3

[0705]

[0706] In Table 1, the charging time of the battery cells in each embodiment and comparative example at 10% SOC to 80% SOC is less than or equal to 10.5 minutes.

[0707] In Comparative Example 1, the projection area of ​​the positive terminal and the negative terminal along their own thickness direction is small, resulting in more heat generated near the terminals and poor cycle stability of the active material; and the current density is too high, which easily causes lithium deposition.

[0708] In the embodiment of the present application, the projection area of ​​the positive terminal along its own thickness direction is 200 mm. 2 Up to 600mm 2 and / or the negative terminal has a projection area of ​​200 mm along its own thickness direction 2 Up to 600mm 2 ; This results in less heat generated near the terminals, higher cycle stability of the active material, less prone to lithium plating, improved reliability of use, and the ability to maintain a certain weight energy density.

[0709] Example 2-1

[0710] A battery cell was prepared using a method similar to that of Example 1-1. The difference from Example 1-1 was that a lamination process was used to prepare an electrode assembly, and thus a battery cell was prepared.

[0711] Comparative Example 2-1 and Example 2-2

[0712] A battery cell was prepared using a method similar to that of Example 2-1. The difference from Example 2-1 was that the projection areas of the positive terminal and the negative terminal were adjusted.

[0713] Test results

[0714] Table 4

[0715]

[0716] In Table 4, the charging time of the battery cells in each embodiment and comparative example at 10% SOC to 80% SOC is less than or equal to 10.5 minutes.

[0717] In Comparative Example 2-1, the projection area of ​​the positive terminal and the negative terminal along their own thickness direction is large, for example, greater than 600 mm. 2 , lithium plating is not easy to occur, but its weight energy density is reduced.

[0718] In the embodiment of the present application, the projection area of ​​the positive terminal along its own thickness direction is 200 mm. 2 Up to 600mm 2 and / or the negative terminal has a projection area of ​​200 mm along its own thickness direction 2 Up to 600mm 2; This results in less heat generated near the terminals, higher cycle stability of the active material, less prone to lithium plating, improved reliability of use, and the ability to maintain a certain weight energy density.

[0719] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises: a housing assembly comprising a housing and a first electrode terminal disposed on the housing; and An electrode assembly is housed in the housing, the electrode assembly comprising a first electrode piece and a second electrode piece, the first electrode piece and the second electrode piece each comprising a coating portion and an electrode tab, the coating portion comprising an active material layer, and the electrode tab is not provided with an active material layer, wherein: One of the first electrode sheet and the second electrode sheet is a positive electrode sheet, and the other is a negative electrode sheet. The active material layer in the positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure. The tab in the first electrode sheet is used to electrically connect the first electrode terminal and the coating portion in the first electrode sheet. The projection area of ​​the first electrode terminal along its thickness direction is 300 mm. 2 Up to 500mm 2 , the charging time of the battery cell from 10% state of charge to 80% state of charge is 5 minutes to 10.5 minutes; The first electrode terminal is used to connect to the first external busbar. The area of ​​the connection between the first electrode terminal and the first busbar is 60 mm. 2 Up to 150mm 2 .

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

3. The battery cell according to claim 2, characterized in that: 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 further connected to a side of the outer shell facing the coating portion.

4. The battery cell according to claim 2 or 3, characterized in that: The first electrode terminal includes a carrying portion with a hollow structure, wherein the carrying portion accommodates at least a portion of the tab of the first electrode piece, and an inner wall of the carrying portion is connected to the tab of the first electrode piece.

5. The battery cell according to claim 4, characterized in that The inner wall includes an end wall and a side wall, and the side wall is arranged around the end wall; The pole tab in the first pole piece is connected to the end wall; and / or the pole tab in the first pole piece is connected to the side wall.

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

7. The battery cell according to claim 6, characterized in that 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 disposed on a side of the outer shell away from the coating portion.

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

9. The battery cell according to claim 6, characterized in that: The area of ​​the connection between the first adapter and the first tab is 80 mm 2 Up to 160mm 2 .

10. The battery cell according to claim 6, characterized in that The first adapter is located between the first tab and the first electrode terminal; A projection surface of a connection area between the first adapter and the first tab along a thickness direction of the first electrode terminal is a first projection surface; The first electrode terminal is used to connect to an external first busbar, and a projection surface of a connection area between the first electrode terminal and the first busbar along a thickness direction of the first electrode terminal is a second projection surface, wherein, 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.

11. The battery cell according to claim 6, characterized in that The first adapter is a positive electrode adapter, and the 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 30mm 2 Up to 60mm 2 .

12. The battery cell according to claim 6, characterized in that The first adapter is a negative electrode adapter, and the 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 24mm 2 Up to 60mm 2 .

13. The battery cell according to claim 1, characterized in that The tab in the first pole piece is a positive tab, and the cross-sectional area of ​​the positive tab close to the coating portion is 0.45 mm 2 to 1.0mm 2 .

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

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

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

17. The battery cell according to claim 1, characterized in that The housing assembly further includes a second electrode terminal disposed on the housing. The tab in the second electrode piece is used to electrically connect the second electrode terminal and the coating portion in the second electrode piece. The projection area of ​​the second electrode terminal along its own thickness direction is 200 mm. 2 Up to 600mm 2 .

18. The battery cell according to claim 1, characterized in that The housing includes a shell and an end cover. The shell is a rectangular parallelepiped structure. The shell accommodates the electrode assembly and has an opening. The end cover covers the opening. The first electrode terminal is provided on the end cover. The projection of the first electrode terminal along its own thickness direction has a first size in the thickness direction of the battery cell, the end cover has a second size in the thickness direction of the battery cell, and 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 A ratio of the first dimension to the second dimension is 0.40 to 0.

85.

20. The battery cell according to claim 1, characterized in that The electrode assembly is a wound structure, and the first electrode sheet and the second electrode sheet are wound in one direction. From the coated portion toward the end cover of the housing, the size of the coated portion in the first pole piece is 60 mm to 120 mm.

21. The battery cell according to claim 1, characterized in that The electrode assembly is a laminated structure, wherein the first electrode sheet and the second electrode sheet are stacked along the thickness direction of the battery cell. From the coated portion toward the end cover of the housing, the size of the coated portion in the first pole piece is 300 mm to 550 mm.

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

23. The battery cell according to claim 1, characterized in that The electrode assembly is a laminated structure, the first electrode sheet and the second electrode sheet are stacked along the thickness direction of the battery cell, and the projection surface of the first electrode terminal along its own thickness direction is a rectangle.

24. The battery cell according to claim 1, characterized in that The coated portion of the first pole piece includes a first straight segment, the coated portion of the second pole piece includes a second straight segment, the first straight segment and the second straight segment are stacked along the thickness direction of the electrode assembly, and the ratio of the number of the pole tabs of the first pole piece to the number of the first straight segments of the first pole piece is 0.5 to 2. The battery cell further includes an electrolyte, the electrolyte includes an organic solvent, the organic solvent includes a chain carboxylate solvent, and the mass content of the chain carboxylate 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 the pole tabs of the second pole piece to the number of the second straight sections of the second pole piece is 0.5 to 2.

27. The battery cell according to claim 24, characterized in that The electrode assembly is a wound structure, the first pole piece and the second pole piece are wound in one direction, and the first pole piece has a plurality of pole tabs.

28. The battery cell according to claim 27, characterized in that The ratio of the number of the pole tabs of the first pole piece to the number of the first straight sections of the first pole piece is 0.5 to 1.

29. The battery cell according to claim 24, characterized in that The electrode assembly is a laminated structure, and there are multiple first pole pieces and multiple second pole pieces, and each of the first pole pieces has at least one pole lug.

30. The battery cell according to claim 29, characterized in that The ratio of the number of the pole tabs of the first pole piece to the number of the first straight sections of the first pole piece is 1 to 2.

31. The battery cell according to claim 1, characterized in that The tab comprises: a tab body connected to the coating portion; and A plurality of tab protrusions are connected to a side of the tab body facing away from the coating portion, and a gap is provided between two adjacent tab protrusions. Each tab protrusion is used to be electrically connected to the electrode terminal.

32. The battery cell according to claim 1, characterized in that The tab in the first pole piece is a positive pole tab, and the thickness of the positive pole tab is 10 μm to 20 μm.

33. The battery cell according to claim 1, characterized in that The tab in the first pole piece is a negative electrode tab, and the thickness of the negative electrode 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, characterized in that The chain carboxylate solvent includes a compound shown in Formula I, Formula I, In Formula I, R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group, R2 includes C1 to C5 alkyl or C1 to C5 halogenated alkyl.

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

38. The battery cell according to claim 36 or 37, characterized in that: 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 carboxylate solvent includes one or more compounds represented by formula I-1 to formula I-8, 。 40. The battery cell according to claim 24, wherein: 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, characterized in that The mass content of the carbonate solvent in the electrolyte is 20% to 80%.

42. The battery cell according to claim 24, characterized in that The electrolyte further includes additives, and the additives include one or more of carbonate additives, sulfur-containing additives, and lithium salt additives.

43. The battery cell according to claim 42, characterized in that The carbonate additive includes one or more of vinylene carbonate, fluoroethylene carbonate, and / or The sulfur-containing additive includes one or more of vinyl sulfate, vinyl disulfate, butylene sulfite, 1,3-propane sultone, vinyl sulfite, methylene disulfonate, and / or The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium bis(oxalatoborate).

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

45. The battery cell according to claim 24, characterized in that The electrolyte further includes a lithium salt, and the lithium salt includes one or more of a fluorine-containing sulfonyl imide salt and lithium hexafluorophosphate.

46. ​​The battery cell according to claim 45, characterized in that The fluorine-containing sulfonyl imide salt includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)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 the lithium bis(fluorosulfonyl)imide is 0.2 mol / L to 0.5 mol / L, and the molar concentration of the lithium hexafluorophosphate is 0.5 mol / L to 1.0 mol / L.

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

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

50. The battery cell according to claim 49, characterized in that The phosphate particles include a general formula of Li x1 A y1 Me a M b P 1-c X c Y z A 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.

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

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

32.

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

26.

54. The battery cell according to claim 49, characterized in that The mass content of carbon 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 5m 2 / g to 18m 2 / g.

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

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

57. The battery cell according to claim 1, characterized in that The lithium-containing phosphate with an olivine structure is in a granular form and includes secondary particles. The secondary particles include a plurality of primary particles. 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 The carbon coating layer is coated on the surface of the artificial graphite.

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

61. The battery cell according to claim 1, characterized in that The battery cell includes a case that accommodates the electrode assembly, the case includes steel, and the thickness of the case is 0.1 mm to 0.5 mm.

62. The battery cell according to claim 61, characterized in that The thickness of the shell is 0.2 mm to 0.35 mm.

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

64. The battery device according to claim 63, characterized in that 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 area between the first electrode terminal and the first busbar is 60 mm 2 Up to 150mm 2 .

65. The battery device according to claim 64, characterized in that The first adapter of the battery cell is located between the first tab of the battery cell and the first electrode terminal; A projection surface of a connection area between the first adapter and the first tab along a thickness direction of the first electrode terminal is a first projection surface; 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 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 claimed in any one of claims 63 to 65.

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