Battery cell, battery device and electric device

Abstract

The present application relates to a battery cell, a battery device and an electric device. The battery cell comprises a casing assembly and an electrode assembly, wherein the casing assembly comprises a casing and a first electrode terminal arranged on the casing; the electrode assembly is accommodated in the casing and comprises a first electrode sheet and a second electrode sheet; the first electrode sheet and the second electrode sheet each comprise a coated portion and a tab, the coated portion comprises an active material layer, and the tab is not provided with an active material layer; 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 comprises a positive electrode active material, which comprises lithium-containing phosphate of an olivine structure; and the tab in the first electrode sheet is configured to electrically connect the first electrode terminal to the coated portion in the first electrode sheet, and the area of the projected surface of the first electrode terminal in its own direction of thickness ranges from 200 mm2 to 600 mm2. The present application can effectively improve the cycle performance and usage reliability of the battery cell under the condition of fast charging.

Description

Battery cell, battery device and power consuming device TECHNICAL FIELD

[0001] The present application relates to a battery cell, a battery device and a power consuming device. BACKGROUND

[0002] Lithium ion batteries have high capacity and long life, and are widely used in electronic devices such as mobile phones, notebook computers, electric vehicles, electric cars, electric planes, electric ships and electric tools, etc. With the development of the application field of lithium ion batteries, higher requirements are put forward for the performance of lithium ion batteries, such as cycle performance and use reliability.

[0003] SUMMARY

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

[0005] In a first aspect, the present application provides a battery cell, the battery cell comprising an electrode assembly and a housing assembly, the housing assembly comprising a housing and a first electrode terminal disposed on the housing; the electrode assembly is accommodated in the housing, the electrode assembly comprising a first electrode tab and a second electrode tab, the first electrode tab and the second electrode tab each comprising a coated portion and a tab, the coated portion comprising an active material layer, the tab being free of the active material layer, wherein one of the first electrode tab and the second electrode tab is a positive electrode tab, and the other is a negative electrode tab, the active material layer in the positive electrode tab comprising a positive electrode active material, the positive electrode active material comprising a lithium-containing phosphate with an olivine structure; the tab in the first electrode tab is used to electrically connect the first electrode terminal and the coated portion in the first electrode tab, the area of the projection surface of the first electrode terminal along its own thickness direction is 200mm 2 to 600mm 2 , and the charging time of the battery cell from 10% state of charge to 80% state of charge is 5min to 10.5min.

[0006] Therefore, in the embodiments 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 2The contact area of the first electrode terminal and the first tab is not too small, the contact resistance of 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, the cycle stability and use reliability of the active material are improved; even in the case of fast charging large current density, the heat generated by the first electrode terminal is not too much, which is beneficial to improve the cycle stability of the active material; on the other hand, the positive active material includes lithium-containing phosphate with olivine structure, which is stable in structure during charging and discharging, and is not easy to cause capacity attenuation, which is beneficial to further improve the cycle performance of the battery cell; and the area of the projection surface of the first electrode terminal is less than or equal to 600mm 2 The weight proportion of the electrode terminal in the battery cell is relatively small, which is beneficial to improve the weight energy density of the battery cell.

[0007] In some embodiments, the area of the projection surface of the first electrode terminal is 300mm 2 to 500mm 2 . Thus, the embodiments of the present application can improve the cycle performance and weight energy density of the battery cell.

[0008] In some embodiments, the tab in the first electrode tab is directly connected to the first electrode terminal. Direct connection can shorten the current conduction path, reduce the resistance on the current conduction path, reduce the heat generation, and reduce the temperature in the battery cell, thereby further improving the cycle performance of the battery cell.

[0009] In some embodiments, the 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 the side of the shell facing the coated part. The above arrangement is beneficial to the direct connection of the first electrode terminal and the first tab.

[0010] In some embodiments, the first electrode terminal includes a bearing part with a hollow structure, the bearing part contains at least part of the tab in the first electrode tab, and the inner wall of the bearing part is connected to the tab in the first electrode tab. Arranging at least part of the first tab in the bearing part can reduce the internal space of the battery cell occupied by the first tab, improve the available space in height of the first coated part, and improve the volume energy density of the battery cell.

[0011] In some embodiments, the inner wall includes an end wall and a side wall, the side wall is arranged outside the end wall; the tab in the first electrode tab is connected to the end wall; and / or the tab in the first electrode tab is connected to the side wall.

[0012] In some embodiments, the battery cell comprises a first adapter connecting the tab of the first pole piece and the first electrode terminal. The carrier not only has the function of accommodating the first tab, but also can realize the connection with the first tab, so that the structure of the first electrode terminal can be simplified, and the processing of the first electrode terminal is facilitated; the structure of the first tab can also be simplified, the redundancy of the first tab is reduced, and the manufacturing cost of the first tab is reduced.

[0013] In some embodiments, the shell comprises an electrode lead-out hole, the first electrode terminal covers the electrode lead-out hole, and the first electrode terminal is arranged on the side of the shell away from the coating part. This kind of structure form makes the first electrode terminal basically not occupy the space inside the shell, which is beneficial to increase the space utilization rate inside the shell, increase the available space of the first coating part, and improve the volume energy density of the battery cell.

[0014] In some embodiments, the area of the connection region between the first adapter and the first electrode terminal is 35mm 2 to 50mm 2 . The area of the connection region between the first adapter and the first electrode terminal is in the above range, the area of the connection region is relatively large, when laser welding is used, the welding mark area is relatively large, which can reduce the welding resistance, reduce heat generation, and improve the cycle performance of the battery cell.

[0015] In some embodiments, the area of the connection region between the first adapter and the first tab is 80mm 2 to 160mm 2 . The area of the connection region between the first adapter and the first tab is in the above range, the area of the connection region is relatively large, when laser welding is used, the welding mark area is relatively large, which can reduce the welding resistance, reduce heat generation, and improve the cycle performance of the battery cell.

[0016] In some embodiments, the first electrode terminal is used to connect with the first busbar outside, and the area of the connection region between the first electrode terminal and the first busbar is 60mm 2 to 150mm 2 . The area of the connection region between the first electrode terminal and the first busbar is in the above range, the area of the connection region is relatively large, when laser welding is used, the welding mark area is relatively large, which can reduce the welding resistance, reduce heat generation, reduce the heat transfer amount to the inside of the battery cell, 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; a projection of a connection area of the first tab with the first electrode terminal along a thickness direction of the first electrode terminal is a first projection area; the first electrode terminal is configured to connect with a first busbar outside the battery cell; a projection of a connection area of the first electrode terminal with the first busbar along the thickness direction of the first electrode terminal is a second projection area, wherein a distance between a geometric center of the first projection area and a geometric center of the second projection area is 0-50 mm. The above arrangement properly configures the current conduction path between the first electrode terminal and the first tab, effectively reduces the heat generation resistance, reduces the heat generation of the battery cell, and improves 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 0.6-2.0 mm, optionally 1.0-1.5 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 the thickness direction thereof is 30-60 mm 2 . 2 .

[0020] In some embodiments, the first adapter is a negative electrode adapter, and the thickness of the negative electrode adapter is 0.5-1.5 mm, 0.6-1.2 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 the thickness direction thereof is 24-60 mm 2 . 2 .

[0022] In some embodiments, the tab in the first tab is a positive electrode tab, and the cross-sectional area of the positive electrode tab close to one side of the coated portion is 0.45-1.0 mm 2 . 2 .

[0023] In some embodiments, the tab in the first tab is a negative electrode tab, and the cross-sectional area of the negative electrode tab close to one side of the coated portion is 0.18-1.0 mm 2 . 2 .

[0024] In some embodiments, the electrode assembly is a stacked structure, the first tab and the second tab are stacked along the thickness direction of the electrode assembly, the first electrode terminal is connected with the tab of the first tab, and the area of the connection area of the first electrode terminal with the tab of the first tab is 140-420 mm 2 . 2 . 2 . 2 .

[0025] In some embodiments, the first electrode terminal is one or more.

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

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

[0028] In some embodiments, the first electrode terminals located on the same side of the coated portion are at least two.

[0029] In some embodiments, the housing assembly further comprises a second electrode terminal disposed on the housing, the tab in the second electrode terminal is used to electrically connect the second electrode terminal and the coated portion in the second tab, and the area of the projection of the second electrode terminal along its own thickness direction is 200mm 2 to 600mm 2 . When the area of the projection of the second electrode terminal along its own thickness direction is in the above range, the cycle performance and energy density of the battery monomer can be effectively improved.

[0030] In some embodiments, the housing comprises a shell and an end cover, the shell is a cuboid structure, the shell accommodates the electrode assembly, and the shell has an opening, the end cover covers the opening, and the first electrode terminal is disposed on the end cover; the size of the projection of the first electrode terminal along its own thickness direction in the thickness direction of the battery monomer is a first size, the size of the end cover in the thickness direction of the battery monomer is a second size, and the ratio of the first size to the second size is greater than 0 and less than or equal to 0.85, and can be 0.40 to 0.85. The first electrode terminal has a high area ratio on the end cover, which is beneficial to improve the overcurrent capacity of the first electrode terminal.

[0031] In some embodiments, the electrode assembly is a wound structure, the first tab and the second tab are wound in one direction, and in the direction from the coated portion to the end cover of the housing, the size of the coated portion in the first tab is 60mm to 120mm.

[0032] In some embodiments, the electrode assembly is a stacked structure, the first tab and the second tab are stacked in the thickness direction of the battery monomer, and in the direction from the coated portion to the end cover of the housing, the size of the coated portion in the first tab is 300mm to 550mm.

[0033] In some embodiments, the electrode assembly is a stacked structure, the first tab and the second tab are stacked in the thickness direction of the battery monomer, and the projection of the first electrode terminal along its own thickness direction is a rectangle.

[0034] In some embodiments, the electrode assembly is in a roll structure, the first electrode tab and the second electrode tab are rolled in one direction, and a projection of the first electrode terminal on a thickness direction of the first electrode terminal is circular.

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

[0036] In some embodiments, the first electrode tab is a negative electrode tab.

[0037] In some embodiments, the battery cell includes a housing assembly, an electrode assembly, and an electrolyte, the electrode assembly and the electrolyte are contained in the housing assembly, the housing assembly is provided with an electrode terminal; the electrode assembly includes a first electrode tab, a second electrode tab, and a separator film between the first electrode tab and the second electrode tab, the first electrode tab and the second electrode tab each include a coated portion and a tab, the coated portion is coated with an active material layer, and the tab is not coated with the active material layer; the first electrode tab and the second electrode tab have opposite polarities, one of the first electrode tab and the second electrode tab is a positive electrode tab, the active material layer of the positive electrode tab includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate with an olivine structure; the electrode assembly is electrically connected to the electrode terminal through the tab, wherein the coated portion of the first electrode tab includes a first flat section, the coated portion of the second electrode tab includes a second flat section, the first flat section and the second flat section are stacked in a thickness direction of the electrode assembly, a ratio of a number of the tabs of the first electrode tab to a number of the first flat sections of the first electrode tab is 0.5 to 2, the electrolyte includes an organic solvent, the organic solvent includes a chain carboxylic acid ester solvent, and a mass content of the chain carboxylic acid ester solvent in the electrolyte is 6% to 65%.

[0038] Therefore, in the embodiments of the present application, the electrolyte includes the chain carboxylate solvent with the above mass content, the conductivity of the solvent system is high, which is beneficial to the rapid migration of lithium ions and improves the rapid charging performance of the battery cell; in the rapid charging system of the battery cell, the current density of the tab is usually large, which leads to an increase in heat generation, so that the temperature in the battery cell is high, which easily leads to the attenuation of the active material and the decomposition of the organic solvent in the electrolyte, and deteriorates the cycle; the positive active material includes the lithium-containing phosphate with olivine structure, which is stable in structure during the charging and discharging process and is not easy to attenuate the capacity, which is beneficial to improving the cycle performance of the battery cell; at the same time, when the ratio of the number of the tabs of the first tab and the number of the first flat sections of the first tab is in the above range, the shunt capacity of the tab can be increased, and the rapid charging performance of the battery cell can be further improved; however, since the connection area of the tab and other components such as the coating part is relatively large, the overcurrent impedance can be effectively reduced, the overcurrent temperature rise is reduced, the temperature rise in the battery cell is not too high, the stability of the electrolyte system and the stability of the active material are improved, which is beneficial to the improvement of the use reliability of the battery cell and can improve the cycle performance; and the connection sites of the tab and the coating part are more, which can increase the connection redundancy such as welding redundancy, and effectively improve the product yield. Therefore, the embodiments of the present application can improve the cycle performance and the rapid charging performance of the battery cell.

[0039] In some embodiments, the mass content of the chain carboxylate solvent in the electrolyte is 25% to 60%.

[0040] In some embodiments, the ratio of the number of the tabs of the second tab to the number of the second flat sections of the second tab is 0.5 to 2. The embodiments of the present application can improve the cycle performance and the rapid charging performance of the battery cell.

[0041] In some embodiments, the electrode assembly is a wound structure, the first tab and the second tab are wound in one direction, and the first tab has a plurality of tabs.

[0042] In some embodiments, the ratio of the number of the tabs of the first tab to the number of the first flat sections of the first tab is 0.5 to 1. The embodiments of the present application can improve the cycle performance and the rapid charging performance of the battery cell.

[0043] In some embodiments, the electrode assembly is a stacked structure, the first tab and the second tab each have a plurality, and each first tab has at least one tab.

[0044] In some embodiments, the ratio of the number of the tabs of the first tab to the number of the first flat sections of the first tab is 1 to 2. The embodiments of the present application can improve the cycle performance and the rapid charging performance of the battery cell.

[0045] In some embodiments, the first tab has a plurality of tab ears, and the plurality of tab ears of the first tab are arranged on the same side of the coated portion. The first tab ears can be arranged on the same side of the first coated portion, which can increase the welding redundancy and effectively improve the product yield.

[0046] In some embodiments, the first tab has a plurality of tab ears, and the plurality of tab ears of the first tab are arranged on the same side of the coated portion. The first tab ears can be arranged on the same side of the first coated portion, which can increase the welding redundancy and effectively improve the product yield.

[0047] In some embodiments, the tab includes a tab body and a plurality of tab protrusions, the tab body is connected to the coated portion, and the plurality of tab protrusions are connected to one side of the tab body away from the coated portion, and there is a gap between adjacent two tab protrusions, and each tab protrusion is used to be electrically connected to the electrode terminal.

[0048] Thus, in the embodiments of the present application, the plurality of tab protrusions are arranged, so that the first tab has a plurality of connection sites, for example, when the first tab is connected to the first adapter, the plurality of tab protrusions can be respectively connected, for example, welded, to different positions of the first adapter, which can increase the welding positions of the first tab and the first adapter, improve the welding yield, and improve the stability of the connection between the first tab and the first adapter.

[0049] In some embodiments, the tab in the first tab is a positive tab, and the thickness of the positive tab is 10-20 μm.

[0050] When the thickness of the positive tab is in the above range, the overcurrent capacity of the positive tab is relatively excellent, which can reduce the heat generation and is beneficial to improve the rapid charging performance of the battery monomer.

[0051] In some embodiments, the tab in the first tab is a negative tab, and the thickness of the negative tab is 4-10 μm.

[0052] When the thickness of the negative tab is in the above range, the overcurrent capacity of the negative tab is relatively excellent, which can reduce the heat generation and is beneficial to improve the rapid charging performance of the battery monomer.

[0053] In some embodiments, the conductivity of the electrolyte is 10.5-20 mS / cm, which can be 15-20 mS / cm.

[0054] When the conductivity of the electrolyte at room temperature is in the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery monomer, thereby reducing the heat generation and improving the rapid charging performance of the battery monomer.

[0055] In some embodiments, the chain carboxylate solvent includes a compound shown in Formula I,

[0056] In Formula I,

[0057] R1 includes a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group,

[0058] R2 includes a C1-C5 alkyl group or a C1-C5 haloalkyl group.

[0059] Therefore, the chain carboxylate solvent described above in the embodiments of the present application has a high conductivity, which is beneficial to improving the rapid charging capability of the battery cell.

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

[0061] In some embodiments, R2 includes a C1-C3 alkyl group or a C1-C3 haloalkyl group.

[0062] In some embodiments, the chain carboxylate solvent includes one or more of a compound shown in Formula I-1 to a compound shown in Formula I-8,

[0063] In some embodiments, the organic solvent further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The combination of the carbonate solvent and the chain carboxylate solvent described above improves the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0064] In some embodiments, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate.

[0065] In some embodiments, the mass content of the carbonate solvent in the electrolyte is 20% to 80%, which can be 25.5% to 42.5%. The carbonate solvent in the mass content described above further improves the conductivity of the electrolyte, which is beneficial to the migration of lithium ions.

[0066] In some embodiments, the electrolyte further includes an additive, and the additive includes one or more of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The additive described above improves the performance of the interface film on the positive electrode side and / or the negative electrode side, which is beneficial to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0067] In some embodiments, the carbonate additive includes one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0068] In some embodiments, the sulfur-containing additive includes one or more of vinyl sulfonate DTD, bis vinyl sulfonate 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methyl methylene disulfonate MMDS.

[0069] In some embodiments, the lithium salt additive includes one or more of lithium difluorophosphate LiPO2F2, lithium difluoro(oxalato)borate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bis(oxalato)borate LiBOB.

[0070] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, and optionally 2% to 8%. The additive in the above mass content can effectively improve the performance of the interface film on the positive electrode side and / or the negative electrode side, which is conducive to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0071] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes one or more of a fluorine-containing sulfimide salt and lithium hexafluorophosphate LiPF6. The lithium salt is easy to dissociate, which is conducive to the rapid migration of lithium ions; and the electrolyte system is relatively stable and is not easy to decompose, which can improve the cycle performance of the battery cell.

[0072] In some embodiments, the fluorine-containing sulfimide salt includes one or more of lithium bisfluorosulfimide LiFSI and lithium bis(trifluoromethylsulfonyl)imide LiTFSI.

[0073] In some embodiments, the lithium salt includes lithium bisfluorosulfimide LiFSI and lithium hexafluorophosphate LiPF6, the molar concentration of lithium bisfluorosulfimide 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.

[0074] In some embodiments, the ratio of the molar concentration of lithium bisfluorosulfimide to the molar concentration of lithium hexafluorophosphate LiPF6 is 0.2 to 1.0, and optionally 0.2 to 0.5.

[0075] In some embodiments, the viscosity of the electrolyte at room temperature is 2.3 mPa·s to 3.5 mPa·s. When the viscosity of the electrolyte is in the above range, the migration rate of lithium ions in the electrolyte is higher, which can further reduce the internal resistance of the battery cell, thereby reducing the heat generation, and can improve the rapid charging performance of the battery cell.

[0076] In some embodiments, the electrolyte density at room temperature is between 1.05 g / mL and 1.35 g / mL. When the electrolyte density is within this range, the migration rate of lithium ions in the electrolyte is higher, which can further reduce the internal resistance of the battery cells, thereby reducing heat generation and improving the fast charging performance of the battery cells.

[0077] In some embodiments, the olivine-structured lithium phosphate comprises phosphate particles and a coating layer. The coating layer coats the phosphate particles and contains one or more elements selected from C, Fe, Ti, Zr, Hf, Ge, and Sn. By coating the surface, the conductivity of the olivine-structured lithium phosphate can be improved, the powder resistivity of the material can be reduced, and the migration rate of lithium ions can be facilitated, thereby reducing the heat generation of the battery cell.

[0078] In some embodiments, the phosphate particles comprise the general formula Li x1 A y1 Me a M b P 1-c X c Y z The compound contains olivine-structured lithium phosphates, 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 including one or more of Na, K, and Mg, Me including one or more of Mn, Fe, Co, and Ni, M including 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 including one or more of S, Si, Cl, B, C, and N, and Y including one or more of O and F. The olivine-structured lithium phosphate exhibits superior cycle stability, which is beneficial for improving the cycle performance of battery cells.

[0079] In some embodiments, the coating layer includes a general formula 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, where 0 ≤ d ≤ 1, 0 < x2 < 5, and 0 < y2 < 4. Coating the phosphate particles with the fast ion conductor can significantly improve the lithium-ion transport rate during multiple lithium intercalation / deintercalation at the positive electrode, enhance the ionic conductivity of the positive electrode active material, thereby increasing the specific capacity and, further, improving the energy density of the corresponding battery cell.

[0080] In some embodiments, the graphitization degree of the positive electrode active material is 0.15-0.32, or 0.19-0.26. When the graphitization degree of the positive electrode active material is in the above range, the conductivity of the positive electrode active material is improved, and the heat generation of the positive electrode plate is reduced, thereby reducing the heat generation of the battery cell.

[0081] In some embodiments, the mass content of carbon in the lithium-containing olivine-structured phosphate is 1%-2%, and the specific surface area of the lithium-containing olivine-structured phosphate is 5 m 2 / g to 18 m 2 / g, or 7.5 m 2 / g to 14 m 2 / g.

[0082] Therefore, the material with the above mass content of carbon and the above specific surface area is more conducive to the effective contact between the electrolyte and the lithium-containing olivine-structured phosphate in the core, and is conducive to the transmission of lithium ions at the phase interface.

[0083] In some embodiments, the volume distribution particle size of the positive electrode active material satisfies 1 μm≤Dv50≤2 μm and 0.4 μm≤Dv10≤0.7 μm. The particle size of the positive electrode active material is relatively small, the lithium ion deintercalation path in the positive electrode active material is short, and the heat generation is less. Moreover, the particle size of the positive electrode active material is not too small, and agglomeration basically does not occur in the process of preparation, so that the performance of the positive electrode active material is stable.

[0084] In some embodiments, the lithium-containing olivine-structured phosphate is in a granular form, and the lithium-containing olivine-structured phosphate includes secondary particles formed by agglomeration of primary particles, and the average particle size of the primary particles is 200 nm-500 nm. The average particle size of the primary particles is relatively small, the lithium ion deintercalation path in the positive electrode active material is short, and the heat generation is less.

[0085] In some embodiments, the coated part in the negative electrode plate includes a negative electrode film layer, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes a carbon-based material, and the carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is 92.0%-94.5%.

[0086] When the graphitization degree of the graphite particles is in the above range, the conductivity of the graphite particles is excellent, the heat generation of the negative electrode plate is reduced, the heat generation of the battery cell is reduced, and the rapid charging performance of the battery cell is improved.

[0087] In some embodiments, the graphite particles include artificial graphite and amorphous carbon, the artificial graphite includes secondary particles formed by aggregation of primary particles, and the amorphous carbon layer is coated on the surface of the artificial graphite. The amorphous carbon layer has more end faces and defects, so that the number of sites capable of deintercalating lithium ions is increased, and the conductivity of the amorphous carbon layer is excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0088] 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 in the above range, the internal resistance of the negative electrode sheet can be further reduced, and the heat generation of the battery cell can be reduced.

[0089] In some embodiments, the coated portion of the negative electrode film layer in the negative electrode sheet 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 collector, the carbon-based material in the first negative electrode film layer includes graphite particles, the second negative electrode film layer is connected to the side of the first negative electrode film layer away from the negative electrode current collector, 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.

[0090] Therefore, in the embodiments of the present application, the particle sizes in the first negative electrode film layer and the second negative electrode film layer are different, which can improve the rapid charging performance of the battery cell. Specifically, during rapid charging, the overpotential of the second negative electrode film layer is usually high, and the bottleneck of rapid charging is mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and improve the problem of lithium extraction on the surface of the negative electrode sheet.

[0091] In some embodiments, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0092] 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 filled more densely, so that the energy density of the battery cell is improved, and the first negative electrode film layer is relatively sparse in filling, and the pores are more abundant, which can improve the rapid charging performance of the battery cell.

[0093] 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 1.21 g / cm 3 . When the tap density of the carbon-based material in the first negative electrode film layer is in a suitable range, the rapid charging performance of the battery cell can be improved.

[0094] In some embodiments, the tap density of the carbon-based material in the second negative electrode film layer is 0.90 g / cm3to 1.25 g / cm3. 3 to 1.25 g / cm3. 3 When the tap density of the carbon-based material in the second negative electrode film layer is within the appropriate range, the energy density of the battery cell can be improved.

[0095] 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 rapid charging performance can be improved.

[0096] 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 rapid charging performance of the battery cell can be improved by reducing the tortuosity of lithium ion transmission.

[0097] In some embodiments, the first negative electrode film layer further comprises a first lithium-containing binder, and the second negative electrode film layer further comprises 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.

[0098] Thus, in the embodiments of the present application, the mass content of the second lithium-containing binder in the second negative electrode film layer is relatively high, and the second lithium-containing binder provides a relatively large number of freely movable lithium ions for the second negative electrode film layer, which can further improve the rapid charging performance of the battery cell.

[0099] 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 deintercalation rate of lithium ions can be improved, and the rapid charging performance of the battery cell can be improved.

[0100] In some embodiments, the mass content of lithium in the first lithium-containing binder is 3% to 10%, and optionally 3% to 8%. When the mass content of lithium is within the above range, the number of freely movable lithium ions in the negative electrode film layer can be relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0101] 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 deintercalation rate of lithium ions is improved, and the rapid charging performance of the battery cell is improved.

[0102] In some embodiments, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, or optionally 3% to 8%. When the mass content of lithium element is in the above range, the number of lithium ions that can freely move in the negative electrode film layer is relatively large, the distance of lithium ion diffusion to the surface of the negative electrode film layer is further shortened, the deintercalation rate of lithium ions is improved, and the rapid charging performance of the battery cell is improved.

[0103] In some embodiments, the first lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0104] Thus, the lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and is not prone to swelling during the charging and discharging process, and has a stable structure, so that the cycle performance of the negative electrode film layer during rapid charging and discharging is improved.

[0105] In some embodiments, the second lithium-containing binder comprises a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, the lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer is derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%.

[0106] Thus, the lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and is not prone to swelling during the charging and discharging process, and has a stable structure, so that the cycle performance of the negative electrode film layer during rapid charging and discharging is improved.

[0107] In some embodiments, the negative electrode active material further comprises a silicon-based material, and the mass content of silicon element in the silicon-based material is 0.3% to 10.0%, based on the mass of the negative electrode active material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell.

[0108] In some embodiments, the battery cell comprises a separator film, the separator film comprises a base film with a porous structure, and the base film has a porosity of 20% to 70%. When the porosity of the separator film is within the above range, the migration ability of lithium ions in the separator film is improved, and the internal resistance of the battery cell is further reduced, thereby reducing heat generation.

[0109] In some embodiments, the separator film comprises a base film with a porous structure, and the base film has a porosity of 35% to 60%. When the porosity of the separator film is within the above range, the migration ability of lithium ions in the separator film is improved, and the internal resistance of the battery cell is further reduced, thereby reducing heat generation.

[0110] In some embodiments, the base film has a thickness of 6 μm to 12 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell is further reduced, thereby reducing heat generation.

[0111] In some embodiments, the base film has a thickness of 6 μm to 9 μm. When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell is further reduced, thereby reducing heat generation.

[0112] In some embodiments, the separator film comprises a base film and a functional layer disposed on at least one side of the base film, the functional layer comprises 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 comprises first inorganic particles, the second functional layer is located on the other side of the base film, and the second functional layer comprises composite particles, the composite particles comprise second inorganic particles and a plurality of non-fluoropolymer particles, the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles. The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator film.

[0113] In some embodiments, the non-fluoropolymer particles comprise an acrylate copolymer. The acrylate copolymer has excellent adhesion, and has high adhesion stability with the base film.

[0114] In some embodiments, the first inorganic particles comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0115] In some embodiments, the second inorganic particles comprise one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above second inorganic particles can improve the heat resistance of the first functional layer.

[0116] In some embodiments, the average particle size of the second inorganic particles is between 5 nm and 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 compressive modulus of the composite particles.

[0117] In some embodiments, the base material of the casing includes steel, and the thickness of the casing is 0.1 mm to 0.5 mm, optionally 0.2 mm to 0.35 mm. A casing thickness within this range results in higher mechanical strength, improving the reliability and cycle performance of the battery cell; furthermore, the casing occupies less space, allowing for more internal space, which is beneficial for increasing the energy density of the battery cell.

[0118] In some implementations, the charging time for a single battery cell from 10% state of charge to 80% state of charge is 5 to 10.5 minutes. The faster charging speed of the battery cell is more conducive to improving fast charging capability.

[0119] Secondly, this application proposes a battery device comprising a plurality of battery cells according to any embodiment of the first aspect of this application.

[0120] In some implementations, the charging time for the battery device from 10% state of charge to 80% state of charge is 5 to 10.5 minutes. A faster charging speed improves the device's fast-charging capability.

[0121] Thirdly, this application proposes an electrical device, which includes the battery device according to any embodiment of the second aspect of this application. Attached Figure Description

[0122] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0123] Figure 1 is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0124] Figure 2 is an exploded schematic diagram of a battery cell provided in some embodiments of this application;

[0125] Figure 3 is a schematic diagram of the structure of the electrode assembly of a battery cell provided in some embodiments of this application;

[0126] Figure 4 is a schematic diagram of the structure of the first electrode of a battery cell provided in some embodiments of this application;

[0127] Figure 5 is a schematic diagram of the structure of the second electrode of a battery cell provided in some embodiments of this application;

[0128] FIG. 6 is a structural schematic diagram of an electrode assembly of a battery cell according to some embodiments of the present application;

[0129] FIG. 7 is a structural schematic diagram of a first electrode tab of a battery cell according to some embodiments of the present application;

[0130] FIG. 8 is a structural schematic diagram of a second electrode tab of a battery cell according to some embodiments of the present application;

[0131] FIG. 9 is a cross-sectional structural schematic diagram of a battery cell according to some embodiments of the present application;

[0132] FIG. 10 is an enlarged structural schematic diagram of the battery cell of FIG. 9 at I;

[0133] FIG. 11 is a cross-sectional structural schematic diagram of a battery cell according to some embodiments of the present application;

[0134] FIG. 12 is an enlarged structural schematic diagram of the battery cell of FIG. 11 at II;

[0135] FIG. 13 is an exploded schematic diagram of a battery cell according to some embodiments of the present application;

[0136] FIG. 14 is a top view structural schematic diagram of a battery cell according to some embodiments of the present application;

[0137] FIG. 15 is a structural schematic diagram of an electrode assembly of a battery cell according to some embodiments of the present application;

[0138] FIG. 16 is a structural schematic diagram of an electrode assembly of a battery cell according to some embodiments of the present application;

[0139] FIG. 17 is a structural schematic diagram of an electrode assembly of a battery cell according to some embodiments of the present application;

[0140] FIG. 18 is a structural schematic diagram of an electrode assembly of a battery cell according to some embodiments of the present application;

[0141] FIG. 19 is an unfolded schematic diagram of a first electrode tab of an electrode assembly of a battery cell according to some embodiments of the present application;

[0142] FIG. 20 is an unfolded schematic diagram of a first electrode tab of an electrode assembly of a battery cell according to some embodiments of the present application;

[0143] FIG. 21 is a structural schematic diagram of a second electrode tab of a battery cell according to some embodiments of the present application;

[0144] FIG. 22 is an unfolded structural schematic diagram of a first electrode tab of a battery cell according to some embodiments of the present application;

[0145] FIG. 23 is a partially enlarged structural schematic view of the first tab shown in FIG. 22 at A;

[0146] FIG. 24 is a structural schematic view of a battery module according to some embodiments of the present application;

[0147] FIG. 25 is a structural schematic view of a battery pack according to some embodiments of the present application;

[0148] FIG. 26 is a structural schematic view of an electric device according to some embodiments of the present application.

[0149] The accompanying drawings are not necessarily drawn to scale.

[0150] The reference signs are explained as follows: 1, electric device; 2, battery pack; 3, controller; 4, motor; 5, case; 5a, first case portion; 5b, second case portion; 5c, accommodation space; 6, battery module; 61, first busbar; 62, second busbar; 7, battery cell; 10, electrode assembly; 111, first tab; 1111, tab body; 1112, tab protrusion; 111a, first folding portion; 111b, second folding portion; 112, second tab; 13, first tab; 131, first flat section; 132, first bent section; 130, first coating portion; 14, second tab; 141, second flat section; 142, second bent section; 140, second coating portion; 15, separator; 200, housing assembly; 20, housing; 201, electrode lead-out hole; 21, case body; 22, end cover; 31, first electrode terminal; 311, bearing portion; 3110, inner wall; 3111, end wall; 3112, side wall; 33, fixing member; 32, second electrode terminal; 41, first adapter; 42, second adapter. DETAILED DESCRIPTION

[0151] Hereinafter, embodiments of the battery cell, battery device, and electric device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed explanations are omitted. For example, there are cases where detailed explanations of matters that are well known, repeated explanations of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following explanations are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0152] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the same, wherein each sub-range includes each integer between (and herein called "a range") the upper and lower limit of that sub-range. For example, a range of "1 to 10" is intended to include any and all sub-ranges between (and the end points of) the minimum of 1 and the maximum of 10, that is, any one of 1 to 3, 4 to 6, 7 to 9, and 10 to 10, as well as 3 to 6, 7 to 10, etc. Further, a range, such as "a to b", where a and b are integers, is intended to include any and all integer ranges between (and the end points of) the minimum of a and the maximum of b, that is, any one of 1 to 10, 2 to 10, 3 to 10, etc. In this application, the use of "at least one" means "one or more", i.e. one or more than one. In addition, the use of "optionally" with respect to any statement in this application means that each and every one of the values and / or conditions so specified are optionally present, and the entity so specified is optionally present. All ranges disclosed herein are meant to be shorthand for describing all possible sub-ranges falling within the range; for example, a range of 0 to 10 is meant to include any and all sub-ranges between (and including) the minimum of 0 and the maximum of 10, that is, any one of 1 to 10, 3 to 7, 0 to 3, 5 to 6, etc. In this application, the use of "at least one" means "one or more", i.e. one or more than one. In addition, the use of "optionally" with respect to any statement in this application means that each and every one of the values and / or conditions so specified are optionally present, and the entity so specified is optionally present. All ranges disclosed herein are meant to be shorthand for describing all possible sub-ranges falling within the range; for example, a range of 0 to 10 is meant to include any and all sub-ranges between (and including) the minimum of 0 and the maximum of 10, that is, any one of 1 to 10, 3 to 7, 0 to 3, 5 to 6, etc.

[0153] If not specifically explained, all the embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0154] If not specifically explained, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0155] If not specifically explained, all the steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, it is mentioned that the method can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0156] Due to the resistance in the current conduction path, heat is inevitably generated in the battery monomer during the cycle charging and discharging process. For example, the electrode terminal is used to conduct the electrode assembly and the external circuit, and the electrode terminal generates heat. Part of the heat diffuses to the inside of the battery monomer, so that the temperature inside the battery monomer increases, the active material is more prone to high-temperature attenuation, and the cycle life of the battery monomer is shortened and the use reliability is deteriorated.

[0157] Therefore, in the embodiments of the present application, the system of the battery cell is reasonably designed, the area of the first electrode terminal in the battery cell is adjusted, 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 reduced, the cycle stability of the active material can be improved, and thus the cycle life and use reliability of the battery cell can be improved.

[0158] Battery cell

[0159] In a first aspect, the embodiments of the present application provide a battery cell.

[0160] As shown in FIGS. 1-3, the battery cell 7 includes a housing assembly 200 and an electrode assembly 10. The housing assembly 200 includes a housing 20 and a first electrode terminal 31 disposed on the housing 20. The electrode assembly 10 is accommodated in the housing 20 and includes a first electrode tab 13 and a second electrode tab 14. The first electrode tab 13 and the second electrode tab 14 each include a coated portion and a tab. The coated portion includes an active material layer. The tab does not include an active material layer. One of the first electrode tab 13 and the second electrode tab 14 is a positive electrode tab, and the other is a negative electrode tab. The active material layer in the positive electrode tab includes a positive active material. The positive active material includes a lithium-containing phosphate with an olivine structure. The tab in the first electrode tab 13 is used to electrically connect the first electrode terminal 31 and the coated portion in the first electrode tab 13. The area of the projection of the first electrode terminal 31 along the thickness direction of the first electrode terminal 31 is 200 mm 2 to 600 mm 2 .

[0161] The housing assembly 200 has an accommodation space for accommodating the electrode assembly 10. In some embodiments, the housing assembly 200 includes the housing 20. The housing 20 includes an end cover 22 and a shell 21. The shell 21 has an opening, and the end cover 22 covers the opening. The first electrode terminal 31 is disposed on the end cover 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 is a cylindrical structure, a cylindrical shell 21 can be selected. If the electrode assembly 10 is a cuboid structure, a cuboid shell 21 can be selected. Alternatively, the electrode assembly 10 and the shell 21 are both cuboid structures. The thickness direction of the first electrode terminal 31 is parallel to the thickness direction of the end cover 22.

[0162] The battery cell 7 is a solid structure with length, thickness and height. In the embodiments of the present application, the direction from the coating part to the end cover 22 of the 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 part to the end cover 22 of the shell 20. The Y direction shown in FIG. 2 represents the thickness direction of the battery cell 7, which is also parallel to the thickness direction of the electrode assembly 10. The Z direction shown in FIG. 2 represents the direction from the coating part to the end cover 22 of the shell 20, which is parallel to the thickness direction of the end cover 22 and also parallel to the thickness direction of the first electrode terminal 31. The W direction shown in FIG. 2 represents the first direction, and the W direction, the Y direction and the Z direction are perpendicular to each other.

[0163] The shell 21 of the battery cell 7 can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The shell 20 of the battery cell 7 can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0164] In some embodiments, the base material of the shell 21 includes steel, which has high mechanical strength and is not easy to deform, thereby improving the use reliability of the battery cell 7. In the embodiments of the present application, the base material refers to the material with the highest proportion in the shell 21.

[0165] When the shell 21 is a cuboid structure, the shell 21 includes two first shell parts 211 and two second shell parts 212, the two first shell parts 211 are oppositely arranged, the two second shell parts 212 are oppositely arranged, the first shell part 211 is connected between the two second shell parts 212, and the area of the first shell part 211 is greater than the area of the second shell part 212.

[0166] In some embodiments, the base material of the shell 21 includes steel, which has high mechanical strength and is not easy to deform, thereby improving the use reliability and cycle performance of the battery cell. In the embodiments of the present application, the base material refers to the material with the highest proportion in the shell 21.

[0167] Optionally, when the base material of the shell 21 includes steel, the thickness of the shell 21 is 0.1 mm to 0.5 mm, which can be 0.2 mm to 0.35 mm. For example, the thickness of the shell 21 is 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm or a range formed by any two of the above values. When the thickness of the shell 21 is in the above range, the mechanical strength of the shell 21 is high, which can improve the use reliability of the battery cell 7; and the shell 21 occupies less space, and the internal space of the shell 21 is large, which is beneficial to improve the energy density of the battery cell 7.

[0168] In some embodiments, the base material of the shell 21 comprises aluminum.

[0169] Optionally, when the base material of the shell comprises aluminum, the thickness of the first shell portion 211 is less than or equal to the thickness of the second shell portion 212.

[0170] Exemplarily, the thickness of the first shell portion 211 is 0.1mm to 1.0mm, optionally 0.3mm to 0.8mm. Exemplarily, the thickness of the first shell portion 211 is 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1.0mm, or a range between any two of the above values.

[0171] The thickness of the first shell portion 211 is relatively thin, so that the shell 21 occupies less space, which can further improve the energy density of the battery monomer 7.

[0172] Exemplarily, the thickness of the second shell portion 212 is 0.1mm to 1.0mm, optionally 0.5mm to 0.8mm. Exemplarily, the thickness of the second shell portion 212 is 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1.0mm, or a range between any two of the above values.

[0173] The thickness of the second shell portion 212 is relatively thick, which can improve the mechanical strength of the shell 21 as a whole and reduce the risk of deformation of the shell 21.

[0174] In the embodiments of the present application, the projection plane of the first electrode terminal 31 along the thickness direction thereof is a normal line of the thickness direction of the first electrode terminal 31, i.e., the projection plane is perpendicular to the thickness direction of the first electrode terminal 31, and the projection plane can represent the flow area of the first electrode terminal 31.

[0175] The number of the first electrode terminals 31 can be one or more. When the number of the first electrode terminals 31 is more than one, the plurality of first electrode terminals 31 can be used to connect the tabs of the first tab 13. The plurality of first electrode terminals 31 can make the first electrode terminals 31 and the tabs of the first tab 13 include a plurality of connection areas. Specifically, the first tab 13 can be divided into a plurality of groups, and each group can be welded to a corresponding first electrode terminal 31. In this way, the connection area, for example, the welding area, of a single first electrode terminal 31 can be reduced, the impedance at the connection can be reduced, and the heat generation can be reduced.

[0176] The plurality of first electrode terminals 31 can be located on the same side of the coated portion or on both sides of the coated portion. When the plurality of first electrode terminals 31 are located on both sides of the coated portion, for example, on both sides of the coated portion in the Z direction, the internal current distribution behavior of the tab can be improved, the current distribution can be uniformized, and the impedance can be further reduced, especially the impedance during fast charging can be effectively reduced.

[0177] The coated portion is a portion coated with an active material, and can be used for deintercalation of active ions during charging and discharging of the battery monomer 7. The coated portion can 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 for electrically connecting the coated portion and the electrode terminal (for example, the first electrode terminal 31), and is not coated with an active material.

[0178] In the embodiments of the present application, on the one hand, the area of the projection of the first electrode terminal 31 is increased, and the area of the projection of the first electrode terminal 31 is greater than or equal to 200mm 2 , so that the contact area of the first electrode terminal 31 and the first tab 111 is not too small, the contact resistance of the first electrode terminal 31 and the first tab 111 can be reduced, the heat generated by the first electrode terminal 31 can be reduced, the temperature in the system of the battery monomer 7 can not be too high, and the cycle stability of the active material can be improved. Even in the case of fast charging with a large current density, the heat generated by the first electrode terminal 31 will not be too much, which is beneficial to improve the cycle stability and use reliability of the active material. On the other hand, the positive active material includes lithium-containing olivine phosphate, which has a stable structure during charging and discharging and is not prone to capacity decay, which is beneficial to further improve the cycle performance of the battery monomer 7. In addition, the area of the projection of the first electrode terminal 31 is less than or equal to 600mm 2 , the weight proportion of the electrode terminal in the battery monomer 7 is relatively small, which is beneficial to improve the weight energy density of the battery monomer 7.

[0179] Therefore, the embodiments of the present application can improve the cycle performance and weight energy density of the battery monomer 7.

[0180] In the embodiments of the present application, the area of the projection of the first electrode terminal 31 along the thickness direction of the first electrode terminal 31 is 200mm2 to 600 mm 2 , optionally 300 mm 2 to 500 mm 2 . Exemplarily, the area of the projection of the first electrode terminal 31 along the thickness direction of the end cap 22 is 200 mm 2 , 220 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2 , 350 mm 2 , 380 mm 2 , 400 mm 2 , 420 mm 2 , 450 mm 2 , 480 mm 2 , 500 mm 2 , 520 mm 2 , 550 mm 2 , 580 mm 2 , 600 mm 2 or a range between any two of the above values.

[0181] When the area of the projection of the first electrode terminal 31 along the thickness direction thereof is within the above range, the cycle performance and energy density of the battery cell 7 can be effectively improved.

[0182] In some embodiments, the housing assembly 200 further comprises a second electrode terminal 32 disposed on the housing 20, and the tab in the second electrode tab 14 is configured to electrically connect the coated portion in the second electrode tab 14 and the second electrode terminal 32. Optionally, the second electrode terminal 32 can be disposed on the end cap 22.

[0183] Optionally, the area of the projection of the second electrode terminal 32 along the thickness direction thereof is 200 mm 2 to 600 mm 2 , optionally 300 mm 2 to 500 mm 2 . Exemplarily, the area of the projection of the second electrode terminal 32 along the thickness direction thereof is 200 mm 2 , 220 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 320 mm 2 , 350 mm 2 , 380 mm 2 , 400 mm 2 , 420 mm 2 , 450 mm2 480mm 2 500mm 2 520mm 2 550mm 2 580mm 2 600mm 2 or a range between any two of the above values.

[0184] When the area of the projection of the second electrode terminal 32 along the thickness direction of the second electrode terminal 32 is within the above range, the cycle performance and the energy density of the battery monomer 7 can be effectively improved.

[0185] The first electrode tab 13 and the second electrode tab 14 have opposite polarities. When the first electrode tab 13 is a positive electrode tab, the second electrode tab 14 is a negative electrode tab, the first electrode terminal 31 is a positive electrode terminal, and the second electrode terminal 32 is a negative electrode terminal. Or when the first electrode tab 13 is a negative electrode tab, the second electrode tab 14 is a positive electrode tab, the first electrode terminal 31 is a negative electrode terminal, and the second electrode terminal 32 is a positive electrode terminal. The coated part in the positive electrode tab corresponds to a positive electrode coated part, the tab corresponds to a positive electrode tab, the active material layer corresponds to a positive electrode film layer containing a positive electrode active material, and the positive electrode coated part includes a positive electrode current collecting part and a positive electrode film layer arranged on at least one side of the positive electrode current collecting part. The coated part in the negative electrode tab corresponds to a negative electrode coated part, the tab corresponds to a negative electrode tab, the active material layer corresponds to a negative electrode film layer containing a negative electrode active material, and the negative electrode coated part includes a negative electrode current collecting part and a negative electrode film layer arranged on at least one side of the negative electrode current collecting part.

[0186] For example, the area of the projection of the positive electrode terminal along the thickness direction of the positive electrode terminal is 200mm 2 to 600mm 2 . Or the area of the projection of the negative electrode terminal along the thickness direction of the negative electrode terminal is 200mm 2 to 600mm 2 . Or the area of the projection of the positive electrode terminal along the thickness direction of the positive electrode terminal is 200mm 2 to 600mm 2 ; and the area of the projection of the negative electrode terminal along the thickness direction of the negative electrode terminal is 200mm 2 to 600mm 2 .

[0187] The electrode assembly 10 can be a winding type structure or a stacking type structure, and optionally, the electrode assembly 10 further includes a separator film 15.

[0188] In order to more clearly illustrate the present application, the tab in the first electrode tab 13 is defined as the first tab 111, and the coated part in the first electrode tab 13 is defined as the first coated part 130. The tab in the second electrode tab 14 is defined as the second tab 112, and the coated part in the second electrode tab 14 is defined as the second coated part 140.

[0189] As shown in FIGS. 3-5, when the electrode assembly 10 is in a jelly-roll structure, the first tab 13, the separator 15, and the second tab 14 are wound in one direction. FIG. 4 shows an unfolded view of the first tab 13, and the first lug 111 is disposed on one side or both sides of the first coated portion 130, and optionally on one side. FIG. 5 shows an unfolded view of the second tab 14, and the second lug 112 is disposed on one side or both sides of the second coated portion 140, and optionally on one side.

[0190] In some embodiments, the dimension of the first lug 111 along the first direction W on the side facing the first coated portion 130 is 30-50 mm, for example, 30 mm, 32 mm, 35 mm, 38 mm, 40 mm, 42 mm, 45 mm, 48 mm, 50 mm, or a range defined by any two of the above values. FIG. 4 shows P1 representing the dimension of the first lug 111 along the first direction W on the side facing the first coated portion 130. When the dimension of the first lug 111 is within the above range, the first lug 111 has good flow capacity, which is beneficial to improve the heat dissipation effect.

[0191] In the case where the first lug 111 is a positive lug, for example, the material of the positive lug is aluminum, the cross-sectional area of the side of the first lug 111 facing the first coated portion 130 is greater than or equal to 0.45 mm 2 , and the upper limit depends on the thickness dimension of the first lug 111, and the cross-section is parallel to the thickness direction of the positive lug. For example, the cross-sectional area of the first lug 111 is 0.45 mm 2 , 0.48 mm 2 , 0.50 mm 2 , 0.52 mm 2 , 0.55 mm 2 , 0.58 mm 2 , 0.60 mm 2 , 0.65 mm 2 , 0.70 mm 2 , 0.75 mm 2 , 0.80 mm 2 , 0.85 mm 2 , 0.90 mm 2 , 0.95 mm 2 , 1.0 mm 2 , or a range defined by any two of the above values. When the cross-sectional area of the first lug 111 is within the above range, the flow capacity of the first lug 111 is strong, which is also beneficial to rapid heat dissipation.

[0192] In the case where the first lug 111 is a negative lug, for example, the material of the negative lug is copper, the cross-sectional area of the side of the first lug 111 facing the first coated portion 130 is greater than or equal to 0.18 mm2 The upper limit depends on the thickness dimension of the first tab 111, and the cross section is parallel to the thickness direction of the positive electrode tab. For example, the cross-sectional area of the first tab 111 is 0.18 mm 2 , 0.20 mm 2 , 0.22 mm 2 , 0.25 mm 2 , 0.28 mm 2 , 0.30 mm 2 , 0.32 mm 2 , 0.35 mm 2 , 0.38 mm 2 , 0.40 mm 2 , 0.42 mm 2 , 0.45 mm 2 , 0.48 mm 2 , 0.50 mm 2 , 0.52 mm 2 , 0.55 mm 2 , 0.58 mm 2 , 0.60 mm 2 , 0.65 mm 2 , 0.70 mm 2 , 0.75 mm 2 , 0.80 mm 2 , 0.85 mm 2 , 0.90 mm 2 , 0.95 mm 2 , 1.0 mm 2 or a range formed by any two of the above values. When the cross-sectional area of the first tab 111 is within the above range, the first tab 111 has a stronger flow capacity, which is also conducive to rapid heat dissipation.

[0193] In some embodiments, the first coating portion 130 has a dimension of 60 mm to 120 mm in the direction of the end cover 22 of the shell 20, i.e., the Z direction of the battery cell 7. Exemplarily, the first coating portion 130 has a dimension of 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 formed by any two of the above values in the Z direction. P3 shown in FIG. 4 represents the dimension of the first coating portion 130 in the Z direction.

[0194] 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, and a thicker battery cell 7 is more conducive to the setting of a wider end cover 22, thereby facilitating the setting of a large-size first electrode terminal 31 and improving the flow density of the first electrode terminal 31.

[0195] In some embodiments, the dimension of the second tab 112 along the first direction W on the side facing the second coating portion 140 is 30-50 mm, for example 30 mm, 32 mm, 35 mm, 38 mm, 40 mm, 42 mm, 45 mm, 48 mm, 50 mm, or a range defined by any two of the above values. P2 shown in FIG. 5 represents the dimension of the second tab 112 along the first direction W on the side facing the second coating portion 140. When the dimension of the second tab 112 meets the above range, the second tab 112 has good flow capacity, which is conducive to improving the heat dissipation effect.

[0196] In some embodiments, the dimension of the second coating portion 140 in the direction of the end cover 22 of the shell 20, i.e. the Z direction of the battery cell 7, is 60-120 mm. 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 defined by any two of the above values. P4 shown in FIG. 5 represents the dimension of the second coating portion 140 along the Z direction.

[0197] 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, and a thicker battery cell 7 is more conducive to setting a wider end cover 22, thereby facilitating the setting of a large-size second electrode terminal 32 and improving the flow density of the second electrode terminal 32.

[0198] As shown in FIGS. 6-8, when the electrode assembly 10 is a laminated structure, the first tab 13 is at least one piece, which can be at least two pieces; the second tab 14 is at least one piece, which can be at least two pieces; and the isolation film 15 is at least one piece, which can be at least two pieces. The first tab 13, the isolation film 15, and the second tab 14 are stacked along the thickness direction Y of the battery cell 7. FIG. 7 shows a structural schematic diagram of the first tab 13, and the first tab 111 is arranged on one side or both sides of the first coating portion 130, which can be on both sides. FIG. 8 shows a structural schematic diagram of the second tab 14, and the second tab 112 is arranged on one side or both sides of the second coating portion 140, which can be on both sides.

[0199] In some embodiments, the dimension of the first tab 111 along the first direction W on the side facing the first coating portion 130 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 between any two of the above values. FIG. 7 shows P1 representing the dimension of the first tab 111 along the first direction W on the side facing the first coating portion 130. When the dimension of the first tab 111 is within the above range, the first tab 111 has good flow capacity, which is beneficial to improve the heat dissipation effect.

[0200] In the case where the first tab 111 is a positive electrode tab, for example, the material of the positive electrode tab is aluminum, the cross-sectional area of the first tab 111 on the side facing the first coating portion 130 is greater than or equal to 0.45 mm 2 , the upper limit of which depends on the thickness dimension of the first tab 111, and the cross-section is parallel to the thickness direction of the positive electrode tab. For example, the cross-sectional area of the first tab 111 is 0.45 mm 2 , 0.48 mm 2 , 0.50 mm 2 , 0.52 mm 2 , 0.55 mm 2 , 0.58 mm 2 , 0.60 mm 2 , 0.65 mm 2 , 0.70 mm 2 , 0.75 mm 2 , 0.80 mm 2 , 0.85 mm 2 , 0.90 mm 2 , 0.95 mm 2 , 1.0 mm 2 , or a range between any two of the above values. When the cross-sectional area of the first tab 111 is within the above range, the flow capacity of the first tab 111 is strong, which is also beneficial to rapid heat dissipation.

[0201] In the case where the first tab 111 is a negative electrode tab, for example, the material of the negative electrode tab is copper, the cross-sectional area of the first tab 111 on the side facing the first coating portion 130 is greater than or equal to 0.18 mm 2 , the upper limit of which depends on the thickness dimension of the first tab 111, and the cross-section is parallel to the thickness direction of the tab. For example, the cross-sectional area of the first tab 111 is 0.18 mm 2 , 0.20 mm 2 , 0.22 mm 2 , 0.25 mm 2 , 0.28 mm 2 , 0.30 mm2 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 or a range between any two of the above values. The cross-sectional area of the first tab 111 is within the above range, the first tab 111 has a stronger flow capacity, which is also conducive to rapid heat dissipation.

[0202] In some embodiments, the first coating portion 130 has a dimension of 300mm to 550mm in the direction of the coating portion pointing to the end cover 22 of the shell 20, i.e., the Z direction of the battery cell 7. Exemplarily, the first coating portion 130 has a dimension of 300mm, 350mm, 400mm, 450mm, 500mm, 550mm or a range between any two of the above values in the Z direction. P3 shown in FIG. 7 represents the dimension of the first coating portion 130 in the Z direction.

[0203] 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, and a thicker battery cell 7 is more conducive to setting a wider end cover 22, thereby facilitating the setting of a large-size first electrode terminal 31 and improving the flow density of the first electrode terminal 31.

[0204] In some embodiments, the dimension of the second tab 112 along the first direction W on the side facing the second coating portion 140 is 30-80 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 defined by any two of the above values. P2 shown in FIG. 8 represents the dimension of the second tab 112 along the first direction W on the side facing the second coating portion 140. When the dimension of the second tab 112 meets the above range, the second tab 112 has good flow capacity, which is conducive to improving the heat dissipation effect.

[0205] In some embodiments, the dimension of the second coating portion 140 in the direction of the end cover 22 of the shell 20, i.e., the Z direction of the battery cell 7, is 300-550 mm. For example, the dimension of the second coating portion 140 along the Z direction is 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, or a range defined by any two of the above values. P4 shown in FIG. 8 represents the dimension of the second coating portion 140 along the Z direction.

[0206] 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, and a thicker battery cell 7 is more conducive to a wider end cover 22, which is conducive to a large-size second electrode terminal 32 and improves the flow density of the second electrode terminal 32.

[0207] The first tab 111 and the first electrode terminal 31 can be directly connected or indirectly connected. In the case of indirect connection, the battery cell can further include a first adapter between the first tab 111 and the first electrode terminal, for electrically connecting the first tab 111 and the first electrode terminal.

[0208] Next, the case where the first tab and the first electrode terminal are directly connected is described.

[0209] As shown in FIG. 9 and FIG. 10, in the case where the first tab 111 is directly connected to the first electrode terminal 31, the direct connection can shorten the current conduction path, reduce the resistance on the current conduction path, reduce the amount of heat generated, and reduce 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, and the electrical connection position is the welding position of the first tab 111 and the first electrode terminal 31; the welding method is not limited, for example, it can be laser welding or first ultrasonic welding to make the tab into a solid body and then laser welding, and according to the position, angle, or structure of the welding site, vertical welding or inclined welding can be selected, as well as lap welding or edge welding. The first tab 111 and the first electrode terminal 31 can also be electrically connected in other ways, such as by using conductive nails or conductive glue.

[0210] 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 and is further connected to the side of the housing 20 facing the first coated portion 130 in the electrode assembly 10. Alternatively, the end cover 22 includes an electrode lead-out hole 201, and the first electrode terminal 31 is arranged on the end cover 22 and is further connected to the side of the end cover 22 facing the first coated portion 130. The above arrangement facilitates the direct connection of the first electrode terminal 31 and the first tab 111.

[0211] The first electrode terminal 31 can be a solid structure or a hollow structure, and is preferably a hollow structure. When the first electrode terminal 31 is a hollow structure, it occupies less weight, which is beneficial to improving the weight energy density of the battery cell. Part or all of the first tab 111 can be received in the hollow structure, thereby saving the height space of the battery cell 7 and improving the volume 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 bearing portion 311 having a hollow structure, and at least part of the first tab 111 is arranged in the bearing portion 311 and connected to the inner wall 3110 of the bearing portion 311. In other examples, part of the first tab 111 is arranged in the bearing portion 311 but can not be connected to the inner wall 3110 of the bearing portion 311, for example, part of the first tab 111 is received in the bearing portion 311, and the other part is located outside the bearing portion 311 and connected to the surface of the first electrode terminal 31 facing the first coated portion 130, and the electrical connection position of the first tab 111 and the first electrode terminal 31 is located on the surface of the first electrode terminal 31 facing the first coated portion 130.

[0212] The bearing part 311 is a solid structure with a containing space and includes an inner wall 3110. At least part of the first tab 111 is arranged in the bearing part 311, which can reduce the internal space of the battery monomer 7 occupied by the first tab 111, improve the available space of the first coating part 130 in height, and improve the volumetric energy density of the battery monomer 7. At least part of the first tab 111 arranged in the bearing part 311 means that the first tab 111 can be entirely contained in the containing space, or can be partially contained in the bearing part 311. The first tab 111 is mechanically connected with the inner wall 3110 of the bearing part 311, which can realize the electrical connection of the first tab 111 and the first electrode terminal 31. Since the first tab 111 is contained in the bearing part 311, the area of the electrical connection between the first tab 111 and the first electrode terminal 31 can be relatively large, which can reduce the difficulty of electrical connection, improve the reliability and stability of electrical connection, and reduce the risk of foreign matter falling from welding to the first coating part 130 during the connection, such as welding, of the first tab 111 and the first electrode terminal 31, which can optimize the interface of the tab. Arranging at least part of the first tab 111 in the bearing part 311 can also reduce the internal space of the battery monomer 7 occupied by the first tab 111, and improve the volumetric energy density of the battery monomer 7.

[0213] 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. The end wall 3111 and the side wall 3112 surround to form the bearing part 311. For example, the end wall 3111 is connected to one side of the side wall 3112 in the thickness direction, the end wall 3111 is connected to the side of the side wall 3112 away from the first coating part 130 in the thickness direction, or the end wall 3111 is connected to the side of the side wall 3112 facing the first coating part 130 in the thickness direction. Of course, the end wall 3111 can also be connected to both sides of the side wall 3112 in the thickness direction. A through hole is formed in the side wall 3112 or the end wall 3111 to facilitate the introduction of the first tab 111 into the bearing part 311.

[0214] The connection position of the first 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. Through the mechanical structure connection, the electrical connection is realized, so that the bearing part 311 not only has the function of containing the first tab 111, but also can realize the connection with the first tab 111, thereby simplifying the structure of the first electrode terminal 31 and facilitating the processing of the first electrode terminal 31. The structure of the first tab 111 can also be simplified, the redundancy of the first tab 111 can be reduced, and the manufacturing cost of the first tab 111 can be reduced.

[0215] The first tab 111 is provided in a plurality, and the plurality of first tabs 111 are connected with the first coating part 130. The first tab 111 can be formed by die cutting a structure without coating an active material. The plurality of first tabs 111 converge to form a first gathering part 111a at a position close to the first coating part 130. The plurality of first tabs 111 converge to each other but are not connected. It can be understood that there is a gap between the adjacent plurality of first tabs 111. The plurality of first tabs 111 converge and are connected to form a second gathering part 111b at a position away from the first coating part 130. The interlayer gap between the plurality of first tabs 111 is reduced, so that the plurality of first tabs 111 in a fluffy state are connected into an integrated structure, for example, by welding or the like. The integrated structure can also be formed by conductive adhesive or the like. The first gathering part 111a is connected to the second gathering part 111b and the first coating part 130.

[0216] The plurality of first tabs 111 converge to form the first gathering part 111a at a position close to the first coating part 130. The plurality of first tabs 111 converge and are connected to form the second gathering part 111b at a position away from the first coating part 130, which means that the first gathering part 111a and the second gathering part 111b are sequentially arranged along the extension direction of the tab sheet.

[0217] In the above technical solution, at least part of the second gathering part 111b is accommodated in the bearing part 311, which facilitates the connection of the first tab 111 and the first electrode terminal 31, can make full use of the space inside the first electrode terminal 31, reduce the occupied space of the first tab 111 inside the shell 20, accommodate a larger size of the first coating part 130, and improve the volumetric energy density of the battery monomer 7. The second gathering part 111b can be connected with the end wall 3111 and / or the second gathering part 111b is connected with the side wall 3112.

[0218] Further, at least part of the first gathering part 111a is accommodated in the bearing part 311, which can further reduce the occupied space of the first tab 111 inside the shell 20, accommodate a larger size of the first coating part 130, and improve the volumetric energy density of the battery monomer 7.

[0219] Next, the indirect connection between the first tab and the first electrode terminal is described.

[0220] As shown in FIGS. 11 to 13, in the case of indirect connection between the first tab 111 and the first electrode terminal 31, the battery monomer 7 can further include a first adapter 41 located between the first tab 111 and the first electrode terminal 31 for electrically connecting the first tab 111 and the first electrode terminal 31.

[0221] In some embodiments, the shell 20 comprises an electrode lead-out hole 201, the first electrode terminal 31 covers the electrode lead-out hole 201, and the first electrode terminal 31 is connected to the side of the shell 20 away from the coating part. Alternatively, the end cover 22 comprises 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 end cover 22 away from the first coating part 130. In this structure, the first electrode terminal 31 does not substantially occupy the space inside the shell 21, which is conducive to increasing the space utilization inside the shell 21, increasing the available space of the first coating part 130, and improving the volumetric energy density of the battery monomer 7. Specifically, the first electrode terminal 31 is connected to the side of the end cover 22 away from the first coating part 130. Alternatively, the first electrode terminal 31 can be connected to the end cover 22 by a fixing member 33, for example, the fixing member 33 can be an insulating fixing member, which is arranged on the outer periphery of the first electrode terminal 31 and located inside the electrode lead-out hole 201. In this structure, the first electrode terminal 31 can be solid, which is conducive to increasing the connection area of the first electrode terminal 31 and the first tab 111, increasing the overcurrent capacity, reducing the heat generation in the battery monomer 7, and improving the cycle performance of the battery monomer 7.

[0222] In some embodiments, the area of the connection region between the first adapter 41 and the first electrode terminal 31 is 35mm 2 to 50mm 2 , for example, 35mm 2 , 38mm 2 , 40mm 2 , 42mm 2 , 45mm 2 , 48mm 2 , 50mm 2 , or a range composed of any two of the above values. S1 shown in FIG. 13 represents the connection region between the first adapter 41 and the first electrode terminal 31. When welding is used, the connection region is the welding surface, and the area of the connection region is the welding area.

[0223] The area of the connection region between the first adapter 41 and the first electrode terminal 31 is relatively large within the above range, which makes the welding area relatively large when laser welding is used, reduces the welding resistance and heat generation, and improves the cycle performance of the battery monomer 7.

[0224] In some embodiments, the area of the connection region between the first adapter 41 and the first tab 111 is 80mm 2 to 160mm 2 , for example, 80mm 2 , 90mm 2 , 100mm 2 , 110mm2 , 120 mm 2 , 130 mm 2 , 140 mm 2 , 150 mm 2 , 160 mm 2 or a range formed by any two of the above values. S2 shown in FIG. 13 represents a connection region of the first adapter 41 and the first tab 111. When welding is used, the connection region is a welding surface, and the area of the connection region is a welding area.

[0225] The area of the connection region of the first adapter 41 and the first tab 111 is within the above range, and the area of the connection region is relatively large. When laser welding is used, the welding area is relatively large, which can reduce the welding resistance, reduce heat generation, and improve the cycle performance of the battery monomer 7.

[0226] In some embodiments, the first electrode terminal 31 is used to connect with an external first busbar, and the area of the connection region of the first electrode terminal 31 and the first busbar is 60 mm 2 to 150 mm 2 , for example, 60 mm 2 , 65 mm 2 , 70 mm 2 , 75 mm 2 , 80 mm 2 , 90 mm 2 , 100 mm 2 , 110 mm 2 , 120 mm 2 , 130 mm 2 , 140 mm 2 , 150 mm 22 or a range formed by any two of the above values. S3 shown in FIG. 13 represents a connection region of the first electrode terminal 31 and the first busbar. When welding is used, the connection region is a welding surface.

[0227] The area of the connection region of the first electrode terminal 31 and the first busbar is within the above range, and the area of the connection region is relatively large. When laser welding is used, the welding area is relatively large, which can reduce the welding resistance, reduce heat generation, reduce the amount of heat transfer to the inside of the battery monomer 7, and improve the cycle performance of the battery monomer 7.

[0228] In some embodiments, the first adapter 41 is located between the first tab 111 and the first electrode terminal 31; the projection of the connecting region of the first adapter 41 with the first tab 111 along the thickness direction of the first electrode terminal 31 is a first projection plane; the first electrode terminal 31 is configured to connect with an external first busbar, and the projection of the connecting region of the first electrode terminal 31 with the first busbar along the thickness direction of the first electrode terminal 31 is a second projection plane, wherein the distance between the geometric center of the first projection plane and the geometric center of the second projection plane is 0-50 mm, which can be 2-50 mm, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 mm or a range formed by any two of the above values. In FIG. 13, L1 represents the distance between the geometric center of the first projection plane and the geometric center of the second projection plane.

[0229] The above arrangement makes the current conduction path between the first electrode terminal 31 and the first tab 111 appropriate, which can effectively reduce the heat generation resistance, reduce the heat generation of the battery monomer 7, and improve the cycle performance of the battery monomer 7.

[0230] In some embodiments, the first adapter 41 is a positive electrode adapter, and the thickness of the positive electrode adapter is 0.6-2.0 mm, which can be 1.0-1.5 mm. For example, the thickness of the positive electrode adapter is 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.10, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5 mm or a range formed by any two of the above values.

[0231] 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 monomer 7 is greater than or equal to 30 mm 2 , the upper limit of which depends on the thickness of the battery monomer 7. For example, the cross-sectional area of the first adapter 41 is 30 mm 2 , 32 mm 2 , 35 mm 2 , 38 mm 2 , 40 mm 2 , 42 mm 2 , 45 mm 2 , 48 mm 2 , 50 mm 2 , 52 mm 2 , 55 mm 2 , 58 mm 2 , 60 mm 2or a range 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 strong flow capacity, which is also conducive to rapid heat dissipation.

[0232] When the thickness of the positive adapter is within the above range, the flow area of the positive adapter is relatively large, which can reduce the heat generation resistance and reduce the heat generation amount. Moreover, the thickness is appropriate, which is conducive to the connection of the positive adapter and other components such as the first tab 111 or the first electrode terminal 31, for example, when welding, the welding power requirement is appropriate, and the welding quality is excellent.

[0233] In some embodiments, the first adapter 41 is a negative adapter, and the thickness of the negative adapter is 0.5 mm to 1.5 mm, which can be 0.6 mm to 1.2 mm. For example, the thickness of the negative 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 formed by any two of the above values.

[0234] In the case where the first adapter 41 is a negative adapter, for example, when the material of the negative adapter is copper, the cross-sectional area of the first adapter 41 parallel to the thickness direction of the battery monomer 7 is greater than or equal to 24 mm 2 , and the upper limit depends on the thickness dimension of the battery monomer 7. For example, the cross-sectional area of the first adapter 41 is 24 mm 2 , 25 mm 2 , 28 mm 2 , 30 mm 2 , 32 mm 2 , 35 mm 2 , 38 mm 2 , 40 mm 2 , 42 mm 2 , 45 mm 2 , 48 mm 2 , 50 mm 2 , 52 mm 2 , 55 mm 2 , 58 mm 2 , 60 mm 2 , or a range 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 strong flow capacity, which is also conducive to rapid heat dissipation.

[0235] When the thickness of the negative adapter is in the above range, the flow area of the negative adapter is relatively large, the heat generation resistance can be reduced, and the heat generation amount can be reduced. In addition, the thickness is appropriate, which is beneficial to the connection of the negative adapter and other components such as the first tab 111 or the first electrode terminal 31, for example, in welding, the welding power requirement is appropriate, and the welding quality is excellent.

[0236] In some embodiments, the shell 20 includes a housing 21 and an end cover 22, the housing 21 is a cuboid structure, the housing 21 accommodates the electrode assembly 10, and the housing 21 has an opening, the end cover 22 covers the opening, and the first electrode terminal 31 is arranged on the end cover 22; the projection of the first electrode terminal 31 in the thickness direction of the battery monomer 7 along the thickness direction of the first electrode terminal 31 is a first size, the size of the end cover 22 in the thickness direction of the battery monomer 7 is a second size, and the ratio of the first size to the second size is greater than 0 and less than or equal to 0.85, which can be 0.40 to 0.85. Exemplarily, the ratio of the first size to the second size 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 composed of any two of the above values. W1 in FIG. 14 represents the first size, and W2 represents the second size, which can also be understood as the width of the end cover 22.

[0237] The area ratio of the first electrode terminal 31 on the end cover 22 is high, which is beneficial to improve the overcurrent capacity of the first electrode terminal 31.

[0238] The structure and position of the second electrode terminal 32 can be the same as or similar to those of the first electrode terminal 31, which will not be described here.

[0239] In some embodiments, the battery monomer 7 further includes a second adapter 42, which is located between the second tab 112 and the second electrode terminal 32 and is used for electrically connecting the second tab 112 and the second electrode terminal 32.

[0240] In other embodiments, the second tab 112 and the second electrode terminal 32 are directly connected.

[0241] In some embodiments, the first electrode terminal 31 and the second electrode terminal 32 can be arranged at intervals on the end cover 22.

[0242] The structure of the second tab 112 in the second tab 14 is the same as that of the first tab 111 in the first tab 13, for example, the second tab 112 in the second tab 14 can include multiple, which will not be described here.

[0243] In the embodiments of the present application, the electrode assembly 10 can be a laminated electrode assembly 10 or a wound electrode assembly 10.

[0244] In the case where the electrode assembly 10 is a stacked structure, the first electrode tab 13, the separator, and the second electrode tab 14 are stacked in the thickness direction of the battery cell 7, and the projection of the first electrode terminal 31 in the thickness direction of the first electrode terminal 31 is a rectangle.

[0245] In some embodiments, the electrode assembly 10 is a stacked structure, the first electrode terminal 31 is connected to the first tab, i.e., the first tab 111, and the area of the connection region of the first electrode terminal 31 and the first tab 111 is 140 mm 2 to 420 mm 2 , for example, 210 mm 2 to 350 mm 2 , for example, 140 mm 2 , 150 mm 2 , 180 mm 2 , 200 mm 2 , 210 mm 2 , 250 mm 2 , 280 mm 2 , 300 mm 2 , 350 mm 2 , 380 mm 2 , 400 mm 2 , 420 mm 2 or a range formed by any two of the above values. The above settings make the current conduction path between the first electrode terminal 31 and the first tab 111 appropriate, 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 the case where the electrode assembly 10 is a wound structure, the first electrode tab 13, the separator, and the second electrode tab 14 are wound in one direction, and the projection of the first electrode terminal 31 in the thickness direction of the first electrode terminal 31 is a circle.

[0247] As shown in FIG. 15, in some embodiments, the coated portion of the first electrode tab 13 includes a first flat section 131, the coated portion of the second electrode tab 14 includes a second flat section 141, the first flat section 131 and the second flat section 141 are stacked in the thickness direction Y of the electrode assembly 10, and the ratio of the number of the tabs of the first electrode tab 13 to the number of the first flat sections 131 of the first electrode tab 13 is 0.5 to 2; 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%.

[0248] The electrolyte includes the chain carboxylate solvent in the above mass content. The solvent system has a high conductivity, which is conducive to the rapid migration of lithium ions and improves the rapid charging performance of the battery cell 7.

[0249] In the fast charging system of the battery cell 7, the current density of the tab is usually large, which leads to an increase in heat generation, so that the temperature in the battery cell 7 is high, which is easy to cause the attenuation of the active material and the decomposition of the organic solvent in the electrolyte, and deteriorate the cycle; and the positive active material includes lithium-containing phosphate with olivine structure, which is stable in structure during charging and discharging, and is not easy to cause capacity attenuation, which is beneficial to improve the cycle performance of the battery cell 7.

[0250] At the same time, when the ratio of the number of tabs of the first tab 13 to the number of first flat sections 131 of the first tab 13 is in the above range, the shunt capacity of the tab can be increased, and the fast charging performance of the battery cell 7 can be further improved; but because the connection area of the tab and other components such as the coating part is relatively large, the overcurrent impedance can be effectively reduced, the overcurrent temperature rise is reduced, so that the temperature rise in the battery cell 7 will not be too high, the stability of the electrolyte system and the stability of the active material are improved, which is beneficial to improve the use reliability of the battery cell 7, and can improve the cycle performance; and the connection sites of the tab and the coating part are more, which can increase the connection redundancy such as welding redundancy, and effectively improve the product yield.

[0251] Therefore, the embodiments of the present application can improve the cycle performance and fast charging performance of the battery cell 7.

[0252] The polarity of the first tab 13 and the second tab 14 is opposite, when the first tab 13 is a positive tab, the second tab 14 is a negative tab, the first electrode terminal 31 is a positive terminal, and the second electrode terminal 32 is a negative terminal; or when the first tab 13 is a negative tab, the second tab 14 is a positive tab, the first electrode terminal 31 is a negative terminal, and the second electrode terminal 32 is a positive terminal.

[0253] The coating part in the positive tab corresponds to the positive coating part, the tab corresponds to the positive tab, the active material layer corresponds to the positive film layer containing the positive active material, the positive coating part includes the positive current collecting part and the positive film layer arranged on at least one side of the positive current collecting part, and when the positive coating part includes the positive flat section, the positive flat section includes the positive current collecting part and the positive film layer arranged on at least one side of the positive current collecting part.

[0254] The coating part in the negative tab corresponds to the negative coating part, the tab corresponds to the negative tab, the active material layer corresponds to the negative film layer containing the negative active material, the negative coating part includes the negative current collecting part and the negative film layer arranged on at least one side of the negative current collecting part, and when the negative coating part includes the negative flat section, the negative flat section includes the negative current collecting part and the negative film layer arranged on at least one side of the negative current collecting part.

[0255] In the embodiments of the present application, the first tab 111 is electrically connected to the first flat section 131 and the first electrode terminal 31, and the ratio of the number of the first tabs 111 of the first tab 13 to the number of the first flat sections 131 of the first tab 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 formed by any two of the above values. When the ratio of the number of the first tabs 111 of the first tab 13 to the number of the first flat sections 131 of the first tab 13 is in the above range, the number of the first tabs 111 is relatively large, which can improve the shunt effect, reduce the overcurrent impedance between the first tab 111 and the first flat section 131, reduce the overcurrent temperature rise, and make the temperature rise inside the battery monomer 7 lower.

[0256] In the embodiments of the present application, the electrode assembly 10 includes a second flat section 141, the second flat section 141 and the first flat section 131 are stacked, and are alternately stacked along the thickness direction Y of the electrode assembly 10, and the second tab 112 is used to electrically connect the second flat section 141 and the second electrode terminal 32. Optionally, the battery monomer 7 further includes a separation film 15, and the first flat section 131, the separation film 15, and the second flat section 141 are alternately stacked.

[0257] In some embodiments, the ratio of the number of the second tabs 112 of the second tab 14 to the number of the second flat sections 141 of the second tab 14 is 0.5 to 2, for example, 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 formed by any two of the above values. When the ratio of the number of the second tabs 112 of the second tab 14 to the number of the second flat sections 141 of the second tab 14 is 0.5 to 2, the number of the second tabs 112 is relatively large, which can improve the shunt effect, reduce the overcurrent impedance between the second tab 112 and the second flat section 141, reduce the overcurrent temperature rise, and make the temperature rise inside the battery monomer 7 lower.

[0258] When the number of the first tabs 111 and the number of the second tabs 112 are the same, the overcurrent density of a single tab is the same, the performance is matched more excellent, which is beneficial to improve the uniformization reaction of the battery monomer 7, improve the shunt effect, and improve the charge and discharge capacity of the battery monomer 7.

[0259] In some embodiments, the first tab 111 is a positive electrode tab; the first flat section 131 comprises a positive electrode active material, the positive electrode active material comprising a lithium-containing phosphate with an olivine structure for providing lithium ions. The relatively large number of positive electrode tabs can improve the shunting effect, reduce the overcurrent impedance between the first tab 111 and the first flat section 131, reduce the overcurrent temperature rise, and thus reduce the temperature rise inside the battery cell 7.

[0260] In some embodiments, the second tab 112 is a negative electrode tab; the second flat section 141 comprises a negative electrode active material, the negative electrode active material comprising a carbon-based material for receiving lithium ions from the first flat section 131.

[0261] The electrode assembly 10 can be a wound electrode assembly 10 or a stacked electrode assembly 10.

[0262] In the case of a wound electrode assembly 10, the electrode assembly 10 comprises a first electrode sheet 13, a second electrode sheet 14, and a separator 15, the first electrode sheet 13 can be in a whole sheet structure, the second electrode sheet 14 can be in a whole sheet structure, and the separator 15 can be in a whole sheet structure. The separator 15 is arranged between the first electrode sheet 13 and the second electrode sheet 14, and 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 comprises a first coating portion 130 and a plurality of first tabs 111. The second electrode sheet 14 comprises a second coating portion 140 and a plurality of second tabs 112.

[0263] After the electrode assembly 10 is wound, the first coating portion 130 of the first electrode sheet 13 can comprise a plurality of first flat sections 131 and a plurality of first bent sections 132. The first bent sections 132 are arranged along the winding direction of the electrode assembly 10 and connected to the first flat sections 131. The first tabs 111 are connected to the first flat sections 131. During the winding process of the electrode assembly 10, one winding cycle of the first electrode sheet 13 can form one first flat section 131.

[0264] The second coating portion 140 of the second electrode sheet 14 can comprise a plurality of second flat sections 141 and a plurality of second bent sections 142. The second bent sections 142 are arranged along the winding direction of the electrode assembly 10 and connected to the second flat sections 141. The second tabs 112 are connected to the second flat sections 141. The first flat sections 131 and the second flat sections 141 are alternately stacked, and the first bent sections 132 and the second bent sections 142 are alternately stacked.

[0265] From the appearance, the electrode assembly 10 includes flat regions and bent regions as well as tabs. The flat regions include first flat sections 131 and second flat sections 141. The bent regions include first bent sections 132 and second bent sections 142.

[0266] In the case where the electrode assembly 10 is in a jelly-roll structure, the ratio of the number of the first tabs 111 of the first electrode tab 13 to the number of the first flat sections 131 of the first electrode tab 13 can be selected to be 0.5 to 1, can be selected to be greater than 0.5 and less than 1, and can be further selected to be 0.6 to 0.99. It can further cooperate with a chain carboxylic acid ester solvent with a mass content of 6% to 65% to improve the cycle performance and fast charging performance of the battery monomer 7. Exemplarily, in the case where the electrode assembly 10 is in a jelly-roll structure, the ratio of the number of the first tabs 111 of the first electrode tab 13 to the number of the first flat sections 131 of the first electrode tab 13 is 0.5, 0.55, 0.6, 0.7, 0.8, 0.9, 0.95, 0.99, 1, or a range composed of any two of the above values.

[0267] FIG. 15 shows the case where the ratio of the number of the first tabs 111 of the first electrode tab 13 to the number of the first flat sections 131 of the first electrode tab 13 is 0.5. One winding of the first electrode tab 13 can form two first flat sections 131, and one of the two first flat sections 131 is connected with a first tab 111. This means that there is one first tab 111 corresponding to two first flat sections 131, i.e., one of the two first flat sections 131 is provided with a first tab 111, and the other first flat section 131 is not provided with a first tab 111. This can be converted to 0.5 first tabs 111 provided on each first flat section 131.

[0268] FIG. 16 shows the case where the ratio of the number of the first tabs 111 of the first electrode tab 13 to the number of the first flat sections 131 of the first electrode tab 13 is 1. One winding of the first electrode tab 13 can form two first flat sections 131, and each of the first flat sections 131 is connected with a first tab 111. This can be converted to one first tab 111 provided on each first flat section 131.

[0269] FIG. 17 shows a case where the ratio of the number of the first tabs 111 to the number of the first flat sections 131 of the first tab 13 is greater than 0.5 and less than 1, the first tab 13 is wound multiple turns, each turn can form two first flat sections 131, one first tab 111 can be arranged on the two first flat sections 131 of at least one of the multiple turns, i.e., one first tab 111 is arranged per turn; two first tabs 111 can be arranged on the two first flat sections 131 of at least another of the multiple turns, i.e., two first tabs 111 are arranged per turn; and the electrode assembly 10 can have greater than 0.5 and less than 1 first tab 111 per first flat section 131.

[0270] When the battery cell 7 meets the above conditions, the solvent system has a high electrical conductivity, which is conducive to the rapid migration of lithium ions and can improve the rapid charging performance of the battery cell 7; and the electrolyte system has excellent protection effect on the negative active material, which is conducive to the improvement of the cycle performance of the battery cell 7; when the ratio of the number of the first tabs 111 to the number of the first flat sections 131 is in the above range, the shunt capacity of the first tab 111 can be increased, which is conducive to the uniformization of the reaction of the first tab 13 and the reduction of impedance, and can further improve the rapid charging performance of the battery cell 7, and can also increase the connection sites of the first tab 111 with other components, increase the welding redundancy, and effectively improve the product yield; since the connection area of the first tab 111 with other components is relatively large, the overcurrent impedance can be reduced, the overcurrent temperature rise can be reduced, the temperature rise in the battery cell 7 system will not be too high, so that the electrolyte system is more stable, which is conducive to the improvement of the use reliability of the battery cell 7 and can improve the cycle performance.

[0271] Optionally, the number of the first tabs 111 in the first tab 13 is multiple, and the first tabs 111 are located on at least one side of the first coating part 130.

[0272] The electrode assembly 10 can be provided as at least one, and can be provided as at least two, for example, two, three, four, etc., and can be provided as two. The at least two electrode assemblies 10 can be stacked along the thickness direction Y of the electrode assembly 10.

[0273] As shown in FIGS. 18-21, when the electrode assembly 10 is a laminated structure, the first tab 13 can have multiple, and the second tab 14 can have multiple, each first tab 13 has a first flat section 131 and a first tab 111. The first flat sections 131 of the multiple first tabs 13 and the second flat sections 141 of the multiple second tabs 14 are stacked along the thickness direction Y of the electrode assembly 10.

[0274] In the case that the electrode assembly 10 is a laminated structure, the electrode assembly 10 includes a flat region in appearance, and optionally, the electrode assembly 10 can also include a bent region, for example, when the separator film 15 adopts a whole sheet structure, the separator film 15 is bent multiple times to form the electrode assembly 10 with the first electrode sheet 13 and the second electrode sheet 14 stacked, or when the negative electrode sheet adopts a whole sheet structure, the negative electrode sheet is bent multiple times to form the electrode assembly with the positive electrode sheet and the separator film stacked; next, taking the case that the electrode assembly 10 only includes a flat region as an example for description.

[0275] In terms of structure, the electrode assembly 10 includes the first electrode sheet 13, the second electrode sheet 14, and the separator film 15, the separator film 15 is arranged between the first electrode sheet 13 and the second electrode sheet 14, and the first electrode sheet 13, the separator film 15, and the second electrode sheet 14 are stacked.

[0276] The first electrode sheet 13 can have multiple, and the second electrode sheet 14 can have multiple, each first electrode sheet 13 includes a first flat section 131 and a first tab 111, the first tab 111 is connected with the first flat section 131; each second electrode sheet 14 includes a second flat section 141 and a second tab 112, the second tab 112 is connected with the second flat section 141; multiple first flat sections 131 and multiple second flat sections 141 are alternately stacked in the thickness direction Y of the electrode assembly 10.

[0277] In the case that the electrode assembly 10 is a laminated structure, the ratio of the number of the first tabs 111 of the first electrode sheet 13 to the number of the first flat sections 131 of the first electrode sheet 13 is 1 to 2, and optionally, is greater than 1 and less than or equal to 2; in combination with the chain carboxylic acid ester solvent with a mass content of 6% to 65%, the performance of the battery monomer 7 can be effectively improved. Exemplarily, in the case that the electrode assembly 10 is a laminated structure, the ratio of the number of the first tabs 111 of the first electrode sheet 13 to the number of the first flat sections 131 of the first electrode sheet 13 is 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a range composed of any two of the above values.

[0278] In the case that the ratio of the number of the first tabs 111 of the first electrode sheet 13 to the number of the first flat sections 131 of the first electrode sheet 13 is 1, it means that the first tab 111 and the first flat section 131 are arranged one by one, which can be converted as one first tab 111 is arranged on each first flat section 131. FIG. 10 shows a structural schematic diagram in which one first tab 111 is arranged on each first flat section 131.

[0279] When the ratio of the number of the first tabs 111 of the first tab sheet 13 to the number of the first flat sections 131 of the first tab sheet 13 is 2, it can be converted that two first tabs 111 are arranged on each first flat section 131, and in this case, one first tab 111 can be arranged on each side of the first flat section 131. FIG. 11 shows a schematic diagram of a structure in which two first tabs 111 are arranged on each first flat section 131.

[0280] When the ratio of the number of the first tabs 111 of the first tab sheet 13 to the number of the first flat sections 131 of the first tab sheet 13 is greater than 1 and less than or equal to 2, it can be converted that greater than 1 and less than or equal to 2 first tabs 111 are arranged on each first flat section 131. For example, the electrode assembly 10 includes two first tab sheets 13, one of which is provided with one first tab 111, and the other of which is provided with two first tabs 111, which is converted to 1.5 first tabs 111 per first tab sheet 13.

[0281] When the battery cell 7 meets the above conditions, the solvent system has a relatively high conductivity, which is beneficial to the rapid migration of lithium ions and can improve the rapid charging performance of the battery cell 7; and the electrolyte system has a relatively excellent protection effect on the negative active material, which is beneficial to the improvement of the cycle performance of the battery cell 7; the number of the first tabs 111 is relatively large, which can increase the shunt capacity of the first tabs 111, make the internal shunt of the first flat section 131 uniform, further improve the rapid charging performance of the battery cell 7, and also increase the connection sites of the first tabs 111 and other components, increase the welding redundancy, and effectively improve the product yield; since the connection area of the first tabs 111 and other components is relatively large, the overcurrent impedance can be reduced, the overcurrent temperature rise can be reduced, the temperature rise in the battery cell 7 system will not be too high, so that the electrolyte system is more stable, which is beneficial to the improvement of the use reliability of the battery cell 7 and can improve the cycle performance.

[0282] Optionally, when the ratio of the number of the first tabs 111 of the first tab sheet 13 to the number of the first flat sections 131 of the first tab sheet 13 is greater than 1, it is converted that greater than 1 first tab 111 is arranged on the first flat section 131 on average, and greater than 1 first tab 111 can be arranged on each side of the first flat section 131, in which case, greater than 1 first tab 111 can share the current density of a single first tab sheet 13, especially when the area of the first tab sheet 13 is relatively large, the internal shunt of the first tab sheet 13 is relatively uniform, which is beneficial to the homogenization reaction and reduces the impedance.

[0283] Optionally, when the ratio of the number of the first tabs 111 to the number of the first flat sections 131 of the first tab 13 is greater than 1, and the average number of the first tabs 111 on the first flat section 131 is greater than 1, more than one first tab 111 can be arranged on the same side of the first flat section 131, which can increase the welding redundancy and effectively improve the product yield.

[0284] The arrangement of the second tabs 112 can be the same as or similar to that of the first tabs 111, which will not be repeated here. For example, the ratio of the number of the second tabs 112 to the number of the second flat sections 141 of the second tab 14 is 1 to 2, which can be greater than 1 and less than or equal to 2.

[0285] When the electrode assembly 10 is in a stacked structure, and the number of the first tabs 111 and the second tabs 112 is the same, the overcurrent density of a single tab is the same, the performance is matched more excellent, which is beneficial to improve the uniform reaction of the battery monomer 7, improve the shunt effect, and improve the charge and discharge capacity of the battery monomer 7.

[0286] Regardless of whether the electrode assembly 10 is in a wound structure or a stacked structure, the first tabs 111 are connected to at least one side of the first coating part 130.

[0287] As shown in FIGS. 22 and 23, 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 connected to the side of the tab body 1111 away from the first coating part 130, and there is a gap between adjacent two tab protrusions 1112. Of course, the first tab 111 can also only include the tab body 1111. FIG. 22 shows a schematic diagram of the first tab 13 in the electrode assembly 10 in a wound structure.

[0288] The plurality of tab protrusions 1112 are arranged so that the first tab 111 has a plurality of connection sites. For example, when the first tab 111 is connected to the first adapter 41, the plurality of tab protrusions 1112 can be respectively connected, for example, welded, to different positions of the first adapter 41, which can increase the welding position of the first tab 111 and the first adapter 41, improve the welding yield, and improve the stability of the connection between them.

[0289] The structure of the second tab 112 can be the same as or similar to that of the first tab 111, which will not be repeated here.

[0290] In some embodiments, the first tab 111 is a positive electrode tab, and the thickness of the positive electrode tab is 10-20 μm, and optionally 10-15 μm. For example, the thickness of the positive electrode tab is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or a range defined by any two of the above values. When the thickness of the positive electrode tab is within the above range, the overcurrent capacity of the positive electrode tab is excellent, the heat generation is reduced, and the rapid charging performance of the battery cell is improved.

[0291] In some embodiments, the first tab 111 is a negative electrode tab, and the thickness of the negative electrode tab is 4-10 μm, and optionally 4-6 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 defined by any two of the above values. When the thickness of the negative electrode tab is within the above range, the overcurrent capacity of the negative electrode tab is excellent, the heat generation is reduced, and the rapid charging performance of the battery cell is improved.

[0292] In the embodiments of the present application, the thickness of the tab is the meaning in the art, which can be detected by detecting devices and methods known in the art, for example, the thickness measured by a micrometer.

[0293] [Positive electrode tab]

[0294] The positive electrode tab includes a positive electrode current collector and a positive electrode film layer including a positive electrode active material disposed on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0295] In the embodiments of the present application, the charging upper limit voltage and the discharging cut-off voltage of the battery cell are different according to different positive electrode active materials. For example, when the phosphate material includes lithium iron phosphate, the charging upper limit voltage can be 3.65 V, and the discharging cut-off voltage can be 2.0 V. For another example, when the phosphate material includes lithium manganese iron phosphate, the charging upper limit voltage can be 4.3 V, and the discharging cut-off voltage can be 2.0 V.

[0296] The 100% state of charge (SOC) and the 0% state of charge (SOC) of the battery cell are defined as follows:

[0297] The battery monomer is charged to the upper limit voltage of the battery at a constant current charging rate of 0.33C, and then charged to 0.05C at a constant voltage, corresponding to the state of 100% SOC of the battery monomer; the battery monomer is discharged to the cut-off voltage at a constant current discharge rate of 0.33C, corresponding to the state of 0% SOC of the battery monomer.

[0298] In some embodiments, the compaction density of the positive electrode film layer of the battery monomer at 100% state of charge SOC is 2.50g / cm 3 to 2.80g / cm 3 ; and optionally 2.55g / cm 3 to 2.70g / cm 3 . For example, the compaction density of the positive electrode film layer of the battery monomer at 100% state of charge SOC is 2.50g / 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 formed by any two of the above values.

[0299] When the compaction density of the positive electrode film layer is in the above range, it is beneficial to improve the energy density of the battery monomer; and because the positive electrode active material in the positive electrode film layer is packed more tightly, the contact resistance between particles is smaller, which can further reduce the resistance of the pole piece and thus reduce the heat generation.

[0300] In some embodiments, the single-sided coating weight of the positive electrode film layer is 200mg / 1540.25mm 2 to 370mg / 1540.25mm 2 ; and optionally 240mg / 1540.25mm 2 to 330mg / 1540.25mm 2 . For example, the single-sided coating weight of the positive electrode film layer is 200mg / 1540.25mm 2 , 210mg / 1540.25mm 2 , 220mg / 1540.25mm2 230 mg / 1540.25 mm 2 240 mg / 1540.25 mm 2 250 mg / 1540.25 mm 2 260 mg / 1540.25 mm 2 270 mg / 1540.25 mm 2 280 mg / 1540.25 mm 2 290 mg / 1540.25 mm 2 300 mg / 1540.25 mm 2 310 mg / 1540.25 mm 2 320 mg / 1540.25 mm 2 330 mg / 1540.25 mm 2 340 mg / 1540.25 mm 2 350 mg / 1540.25 mm 2 360 mg / 1540.25 mm 2 370 mg / 1540.25 mm 2 or a range formed by any two of the above values.

[0301] When the single-side coating weight of the positive electrode film layer is within the above range, the heat generation per unit area of the positive electrode tab will not be too large, and the energy density of the battery cell can be improved.

[0302] In the embodiments of the present application, the compaction density of the positive electrode film layer of the battery cell at 100% state of charge (SOC) is a meaning known in the art, that is, the positive electrode tab is disassembled from the battery cell at 100% state of charge (SOC), and the compaction density of the positive electrode film layer is measured, for example, a single-side coated positive electrode tab (if it is a double-side coated tab, the positive electrode film layer on one side can be wiped off first), is punched into a small disc with an area of S1, weighed, recorded as M1, and its thickness H1 is measured. Then the positive electrode film layer of the above weighed positive electrode tab is wiped off, the weight of the positive electrode current collector is weighed, recorded as M0, and its thickness H0 is measured. The single-side coating weight of the positive electrode film layer = (the weight of the positive electrode tab M1 - the weight of the positive electrode current collector M0) / S1, the thickness of the positive electrode film layer = the thickness of the positive electrode tab H1 - the thickness of the positive electrode current collector H0, and the compaction density of the positive electrode film layer = the single-side coating weight of the positive electrode film layer / the thickness of the positive electrode film layer.

[0303] In some embodiments, the powder resistivity of the positive electrode active material is 1 Ω·cm to 27.5 Ω·cm; optionally, less than or equal to 20 Ω·cm; optionally, less than or equal to 11 Ω·cm. Illustratively, the powder resistivity of the positive electrode active material can be 27.5 Ω·cm, 20 Ω·cm, 19 Ω·cm, 18 Ω·cm, 17 Ω·cm, 16 Ω·cm, 15 Ω·cm, 14 Ω·cm, 13 Ω·cm, 12 Ω·cm, 11 Ω·cm, 10 Ω·cm, 9 Ω·cm, 8 Ω·cm, 7 Ω·cm, 6 Ω·cm, 5 Ω·cm, 4 Ω·cm, 3 Ω·cm, 2 Ω·cm, 1 Ω·cm, or a range defined by any two of the foregoing values.

[0304] The relatively low powder resistivity of the positive electrode active material results in a relatively low resistance of the positive electrode tab, and less heat generation of the battery cell.

[0305] In the embodiments of the present application, the powder resistivity of the material is the meaning known in the art, and can be detected by the methods and devices known in the art, for example, according to the test standard GB / T30835-2014, using PRCD1100 powder resistivity meter for testing.

[0306] In some embodiments, the powder compaction density of the positive electrode active material under 30000N is 2.46g / cm 3 to 2.8g / cm 3 . Illustratively, the powder compaction density of the positive electrode active material under 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 defined by any two of the foregoing values.

[0307] When the powder compaction density of the positive electrode active material at 30000N is in the above range, the energy density of the battery cell can be improved, and the positive electrode active material in the positive electrode film layer can be more closely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation.

[0308] In the embodiments of the present application, the powder compaction density of the material is the meaning known in the art, which can be detected by the methods and devices known in the art according to the test standard GB / T24533-2009. For example, a certain amount of positive electrode active material is taken as a sample, added into a mold with a bottom area of 1.327cm 2 of a UTM7305 electronic pressure testing machine, pressurized to 3000kg (equivalent to 30000N), pressure maintained for 30s, then pressure released, maintained for 10s, then the powder compaction density of the positive electrode active material under the action of 30000N is recorded and calculated.

[0309] In some embodiments, the charge gram capacity of the positive electrode active material at 0.1C rate is 150mAh / g to 170mAh / g, which can be selected as 157mAh / g to 170mAh / g. For example, the charge gram capacity of the positive electrode active material at 0.1C rate is 150mAh / g, 151mAh / g, 152mAh / g, 153mAh / g, 154mAh / g, 155mAh / g, 156mAh / g, 157mAh / g, 158mAh / g, 159mAh / g, 160mAh / g, 161mAh / g, 162mAh / g, 163mAh / g, 164mAh / g, 165mAh / g, 166mAh / g, 167mAh / g, 168mAh / g, 169mAh / g, 170mAh / g or a range consisting of any two of the above values.

[0310] When the charge gram capacity of the positive electrode active material at 0.1C rate is in the above range, the energy density of the battery cell is relatively high.

[0311] In the embodiments of the present application, the gram capacity of the active material is the meaning known in the art, which can be tested by the devices and methods known in the art. The test method of the first coulomb efficiency and the first discharge specific capacity in the national standard GB / T 24533-2019 Appendix G is used, lithium metal is used as the negative electrode, the sample electrode sheet containing the above material is used as the positive electrode, and a half-button type battery is assembled. Under the condition of 23℃±2℃, the half-button type battery is placed on a battery tester or other test equipment with the same performance, and the button capacity is obtained by 0.1C rate charge-discharge, and then the capacity is divided by the mass of the active material of the electrode sheet to obtain the charge gram capacity parameter.

[0312] In some embodiments, the mass ratio of the olivine-structured lithium-containing phosphate in the positive electrode active material can be greater than or equal to 80% and less than or equal to 100%, and the positive electrode active material of the present application can be considered to be an olivine-structured lithium-containing phosphate system. When the mass ratio of the olivine-structured lithium-containing phosphate is less than 100%, the positive electrode active material can further include commonly used positive electrode active materials, such as at least one of a lithium-containing transition metal oxide and a lithium-containing phosphate. Examples of the lithium-containing transition metal oxide can include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and a modified compound of each thereof. Examples of the lithium-containing phosphate can include, but are not limited to, at least one of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite of lithium manganese iron phosphate and carbon.

[0313] Optionally, the mass ratio of the olivine-structured lithium-containing phosphate in the positive electrode active material is 100%.

[0314] In the embodiments of the present application, the olivine-structured lithium-containing phosphate can be a phosphate particle or a material obtained after coating modification, for example, the olivine-structured lithium-containing phosphate includes a phosphate particle and a coating layer, the coating layer is coated on the surface of the phosphate particle, and the coating layer contains one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

[0315] The phosphate particle is coated with the coating layer on the surface, which can improve the electrical conductivity of the olivine-structured lithium-containing phosphate, reduce the powder resistivity of the material, and be beneficial to the migration rate of lithium ions, improve the rapid charging capability of the battery, and reduce the heat generation of the battery cell.

[0316] In some embodiments, the phosphate particle includes a general formula of Li x1 A y1 Me a M b P 1-c X c Y zLi1-x1-y1-a-b-c-d Me x1 A y1 X a B b M c X d (PO4)z Y wherein, 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A comprises one or more of Na, K, Mg, Me comprises one or more of Mn, Fe, Co, Ni, M comprises one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, X comprises one or more of S, Si, Cl, B, C, N, and Y comprises one or more of O, F. The phosphate particles have excellent cycle stability, which is conducive to improving the cycle performance of the battery monomer.

[0317] Exemplarily, the phosphate particles comprise one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. During the charging and discharging process of the battery monomer, active ions such as Li are deintercalated and consumed, and the molar content of Li is different when the battery monomer is discharged to different states. In the enumeration of the positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4, the molar content of Li is the initial state of the material, that is, the state before feeding, and the positive electrode active material is applied to the battery system. After charging and discharging cycles, the molar content of Li may change. In the enumeration of the positive electrode active materials LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4 in the embodiments of the present application, the molar content of oxygen O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen O to change. In practice, the molar content of oxygen O will fluctuate, and the above-mentioned situations are all within the protection scope of the present application.

[0318] In some embodiments, the coating layer comprises a fast ion conductor of the general formula Li 3-d Fe 2-d M2 d (PO x2 ) y2 , M2 comprises one or more of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0

[0319] Exemplarily, the fast ion conductor is a material having a NASICON structure, for example, comprising one or more of lithium titanium iron phosphate Li2FeTi(PO4)3, lithium zirconium iron phosphate Li2FeZr(PO4)3, and lithium tin iron phosphate Li2FeSn(PO4)3.

[0320] The fast ion conductor with NASICON structure is a material with super-fast ion conduction ability, has abundant three-dimensional lithium ion diffusion and transmission channels, and has the advantages of high ion conduction efficiency, strong structural stability, etc. in the process of multiple delithiation and lithium intercalation. Coating the fast ion conductor containing the NASICON structure on the surface of the phosphate particles can significantly improve the transmission rate of lithium ions in the positive electrode end during multiple delithiation and lithium intercalation, improve the ion conductivity of the positive electrode active material, and improve the rapid charging capacity of the battery monomer. In addition, it can also improve the specific capacity and the energy density of the corresponding battery monomer.

[0321] In some embodiments, the coating layer further comprises elemental carbon.

[0322] The elemental carbon and the fast ion conductor can be arranged in layers, for example, the elemental carbon as an independent carbon coating layer and the fast ion conductor 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, i.e., the fast ion conductor layer is located on the side of the carbon coating layer away from the phosphate particles. Alternatively, the fast ion conductor layer can be coated on the surface of the phosphate particles, and the carbon coating layer is located on the surface of the fast ion conductor layer, i.e., the carbon coating layer is located on the side of the fast ion conductor layer away from the phosphate particles. Of course, the elemental carbon and the fast ion conductor can also be arranged in the same layer.

[0323] Optionally, the carbon coating layer can be coated on the surface of the fast ion conductor layer by a carbonization process of an organic carbon source (e.g., glucose, polyethylene glycol, etc.). The carbon coating layer can partially coat the fast ion conductor layer or completely coat the fast ion conductor layer. The arrangement of the carbon coating layer can significantly improve the electronic conductivity of the phosphate particles, compensate for the poor electronic conduction performance of the phosphate particles, and improve the energy density of the battery monomer.

[0324] Specifically, the arrangement of the carbon coating layer provides the following advantages for the positive electrode active material of the application:

[0325] The carbon coating layer in the positive electrode active material of the application provides a suitable channel for the transmission of electrons, which can significantly improve the conduction rate of electrons during multiple delithiation and lithium intercalation, improve the electronic conductivity of the lithium-containing phosphate, improve the charging capacity of the corresponding battery monomer, and also improve the energy density.

[0326] The carbon coating layer of the positive electrode active material of the application has a loose and porous structure, which enables the electrolyte to fully and effectively contact the lithium-containing phosphate, thereby improving the transmission rate of lithium ions at the phase interface and improving the charging capacity of the battery monomer.

[0327] Coating a carbon coating layer on the surface of the lithium-containing phosphate not only improves the conductivity of the lithium-containing phosphate, but also improves the structural stability of the positive electrode active material, effectively alleviates the iron dissolution phenomenon of the positive electrode active material during long-term storage and cycle use of the battery monomer, thereby improving the cycle life of the battery monomer.

[0328] The positive electrode active material of the present application takes the lithium-containing phosphate as the base material, fully utilizes the advantages of low cost, high reliability and good cycle stability of the lithium-containing phosphate, and solves the disadvantages of poor electronic conductivity and ionic conductivity by using the coating layer (fast ion conductor layer and carbon coating layer). The battery monomer prepared from the positive electrode active material of the present application can improve the energy density of the battery monomer under the premise of excellent cycle performance.

[0329] In the embodiments of the present application, the content of elements in the positive electrode active material is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, referring to EPA 6010D-2014, testing by inductively coupled plasma atomic emission spectrometry, and measuring by plasma atomic emission (ICP-OES, instrument model: Thermo ICAP7400). After disassembling the positive electrode sheet from the battery monomer discharged to 0% state of charge SOC, washing and drying with DMC, and removing impurities by high temperature calcination, 0.4g of the positive electrode active material is weighed, 10ml (50% concentration) aqua regia is added thereto. Then it is placed on a 180℃ flat plate for 30min. After digestion on the flat plate, it is diluted to a volume of 100mL, and the standard curve method is used for quantitative testing.

[0330] In some embodiments, the graphitization degree of the positive electrode active material is 0.15 to 0.32, which can be optionally 0.19 to 0.26. Illustratively, the graphitization degree of the positive electrode active material is 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32 or a range composed of any two of the above values.

[0331] When the graphitization degree of the positive electrode active material is in the above range, it is beneficial to improve the conductivity of the positive electrode active material and reduce the heat generation of the positive electrode sheet, thereby reducing the heat generation of the battery monomer.

[0332] In the embodiments of the present application, the higher the graphitization degree of the material, the lower the degree of disorder, which can be tested according to the test standard JIS / K 0131-1996 X-ray diffraction analysis method general rules.

[0333] In some embodiments, the mass content of carbon element in the lithium-containing olivine-structured phosphate is 1% to 2%, and the specific surface area of the lithium-containing olivine-structured phosphate is 5m 2 / g to 18m 2 / g.

[0334] Optionally, the mass content of carbon element in the lithium-containing olivine-structured phosphate is 1% to 2%, and the specific surface area of the lithium-containing olivine-structured phosphate is 7.5m 2 / g to 14m 2 / g.

[0335] Illustratively, the mass content of carbon element in the lithium-containing olivine-structured 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 composed of any two of the above values.

[0336] Illustratively, the specific surface area of the lithium-containing olivine-structured phosphate 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 composed of any two of the above values.

[0337] The carbon element mainly exists in the form of a carbon coating layer in the coating layer, and the carbon coating layer is loose and porous, which is conducive to improving the specific surface area of the material, and is more conducive to the effective contact between the electrolyte and the phosphate particles, and is conducive to the transmission of lithium ions at the phase interface. In addition, when the mass content of the carbon element is in the above range, the conductivity of the lithium-containing olivine-structured phosphate can be significantly improved, which is conducive to improving the ionic conductivity and electronic conductivity of the lithium-containing olivine-structured phosphate, and can improve the rapid charging capacity and energy density of the battery cell.

[0338] In the embodiments of the present application, the specific surface area of the material is in the meaning known in the art and can be detected by using the devices and methods known in the art, for example, according to the test standard GB / T 19587-2017, taking the positive electrode active material as the sample, and testing the specific surface area by using a Tri-Star 3020 type specific surface area pore size analyzer of the Micromeritics company in the United States.

[0339] 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.

[0340] Exemplarily, the Dv50 of the positive electrode active material can be 1 μm, 1.1 μm, 1.15 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, 1.5 μm, 1.55 μm, 1.6 μm, 1.65 μm, 1.7 μm, 1.75 μm, 1.8 μm, 1.85 μm, 1.9 μm, 1.95 μm, 2 μm, or a range formed by any two of the above values.

[0341] Exemplarily, the Dv10 of the positive electrode active material can 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 formed by any two of the above values.

[0342] The particle size of the positive electrode active material is relatively small, the lithium ion deintercalation lithium path in the positive electrode active material is short, the heat production is less, and the particle size of the positive electrode active material is not too small, and agglomeration basically does not occur in the process of preparation, so that the performance of the positive electrode active material is stable.

[0343] In the embodiments of the present application, the volume average particle size Dv50 of the material refers to the particle size corresponding to 50% in the volume distribution, and the volume average particle size Dv10 of the material refers to the particle size corresponding to 10% in the volume distribution, which can be detected by using the devices and methods known in the art, for example, taking the positive electrode active material as the sample, according to the test standard GB / T 19077-2016, and testing the Dv50 and Dv10 of the particles by using a Mastersizer 2000E type laser particle size analyzer.

[0344] When the positive electrode active material includes not only the lithium-containing phosphate with olivine structure but also other materials, 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.

[0345] In some embodiments, the lithium-containing olivine-structured phosphate is in a particulate form, the lithium-containing olivine-structured phosphate comprises secondary particles, the secondary particles comprise a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 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, 500 nm, or a range defined by any two of the above values.

[0346] The average particle size of the primary particles is relatively small, the lithium ion deintercalation path in the positive electrode active material is short, and the heat generation is less.

[0347] In the embodiments of the present application, the secondary particle refers to an agglomerated particle formed by two or more primary particles. The primary particles and the secondary particles can be easily distinguished by experimental means (e.g., using a scanning electron microscope to take SEM images), and the average particle size of the primary particles can be obtained by SEM testing. The SEM testing parameters can be set as follows: working voltage (EHT) is 10.00 kV, InLens detector is used, working distance is 4.6 mm, and magnification is 1000X.

[0348] In some embodiments, the positive electrode film layer further comprises one or more of a ternary material, lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium manganite, lithium tartrate, trilithium citrate, lithium nickelate, and lithium ferrite. The above-mentioned materials can act as a lithium supplement, which can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, improve the capacity, and thus improve the energy density of the battery cell.

[0349] Optionally, the ternary material comprises Li x3 A y3 Ni a3 Co b3 Mn c M3(1-a3-b3-c3)Y3 z3 wherein 0

[0350] Exemplarily, the ternary material includes at least one of 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 O2.

[0351] In some embodiments, the mass content of the lithium supplement agent in the positive electrode film layer is 0.5% to 5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range between any two of the above values. When the mass content of the lithium supplement agent is in the above range, the lithium supplement agent can supplement lithium ions for the positive electrode film layer, make up for the irreversible loss of lithium ions in the system, and improve the capacity, thereby improving the energy density of the battery cell.

[0352] The lithium supplement agent can be located in the same layer as the positive electrode active material, or can be located in different layers. When the lithium supplement agent and the positive electrode active material are located in different layers, the lithium supplement agent can be located in a lithium supplement layer, and the positive electrode active material can be located in a positive electrode active material layer, in other words, the positive electrode film layer includes the lithium supplement layer and the positive electrode active material layer. The positive electrode active material layer can be arranged on at least one side of the positive electrode current collector, and the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector. Alternatively, the lithium supplement layer can be arranged on at least one side of the positive electrode current collector, and the positive electrode active material layer can be located between the lithium supplement layer and the positive electrode current collector. Alternatively, the lithium supplement layer can be located between the positive electrode active material layer and the positive electrode current collector, and the lithium supplement agent in the lithium supplement layer can be gradually released into the system to make up for the loss of lithium in the battery system during the cyclic charging and discharging of the battery cell.

[0353] In some embodiments, the positive electrode film layer can further optionally include a positive electrode conductive agent. The type of positive electrode conductive agent is not particularly limited in the embodiments of the present application, and as an example, the positive electrode conductive agent includes at least one of super conductive 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.

[0354] In some embodiments, the positive electrode film layer can further optionally include a positive electrode binder. The embodiments of the present application do not have particular limitations on the type of positive electrode binder, and as an example, the positive electrode binder can include at least one of polyvinylidene fluoride, polytetrafluoroethylene, a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, a polyacrylic acid, and a fluorine-containing acrylic ester-based resin. In some embodiments, the mass content of the positive electrode binder is ≤ 5% based on the mass of the positive electrode film layer.

[0355] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. As an example of the metal foil, at least one foil of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy can be employed. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material of the metal material layer can include at least one of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer can include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0356] In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05 to 0.3. As an example, the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, or a range defined by any two of the aforementioned values.

[0357] When the ratio of the thickness of the positive electrode current collector to the thickness of the single-sided positive electrode film layer is within the aforementioned range, the rapid charging capability and the energy density of the battery cell can be improved.

[0358] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 20 μm, 10 μm to 15 μm, and can optionally be 12 μm to 15 μm. As an 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 defined by any two of the aforementioned values.

[0359] When the thickness of the positive electrode current collector is within the aforementioned range, the overcurrent capability of the positive electrode current collector is excellent, and the battery cell can have a high energy density.

[0360] In the embodiments of the present application, the thickness of the positive electrode film layer and the positive electrode current collector is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, the thickness of the positive electrode tab is measured by using a micrometer, the thickness of the positive electrode current collector is measured by removing the film layer on the surface of the positive electrode current collector, 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 tab minus the thickness of the positive electrode current collector, and 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 tab minus the thickness of the positive electrode current collector) / 2.

[0361] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0362] The positive electrode tab does not exclude other additional functional layers except the positive electrode film layer. For example, in some embodiments, the positive electrode tab of the embodiments of the present application further comprises a positive electrode conductive layer arranged between the positive electrode current collector and the positive electrode film layer and arranged on the surface of the positive electrode current collector. In some other embodiments, the positive electrode tab of the embodiments of the present application further comprises a protective layer arranged on the surface of the positive electrode film layer.

[0363] In some embodiments, the positive electrode tab further comprises a positive electrode conductive layer arranged 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 tab and reduce the heat generation of the positive electrode tab, thereby reducing the heat generation of the battery cell.

[0364] 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 formed by any two of the above values.

[0365] When the thickness of the positive electrode conductive layer is in the above range, the conductivity of the positive electrode tab can be further improved, the heat generation of the positive electrode tab can be reduced, thereby reducing the heat generation of the battery cell, and the energy density of the battery cell can be improved.

[0366] In the embodiments of the present application, the thickness of the positive electrode conductive layer is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, the thickness of the positive electrode conductive layer is directly measured by tomography of the positive electrode tab.

[0367] In some embodiments, the positive electrode conductive layer comprises one or more of a positive electrode conductive agent and a positive electrode binder.

[0368] Optionally, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 30% to 50%. Illustratively, the mass content of the positive electrode conductive agent is 30%, 35%, 40%, 45%, 50%, or a range consisting of any two of the aforementioned values.

[0369] Illustratively, the positive electrode conductive agent includes one or more of super-p, 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 tab and reducing the heat generation of the battery cell.

[0370] Optionally, the mass content of the positive electrode binder in the positive electrode conductive layer is 50% to 70%. Illustratively, the mass content of the positive electrode binder is 50%, 60%, 65%, 70%, or a range consisting of any two of the aforementioned values.

[0371] 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, a polyacrylic acid, and a fluorine-containing acrylic ester resin. The positive electrode binder in the positive electrode conductive layer can improve the adhesion between the positive electrode current collector and the positive electrode film layer, thereby improving the structural stability of the positive electrode tab.

[0372] [Positive electrode tab]

[0373] The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0374] In some embodiments, the compaction density of the negative electrode film layer is 1.15 g / cm 3 to 1.36 g / cm 3 , optionally 1.25 g / cm 3 to 1.36 g / cm 3 , at 100% state of charge of the battery cell. Illustratively, the compaction density of the negative electrode film layer is 1.15 g / cm 3 , 1.18 g / cm 3 , 1.20 g / cm 3 , 1.22 g / cm 3 , 1.25 g / cm 3 , 1.28 g / cm 3 , 1.3 g / cm 3 , 1.32 g / cm 3 , 1.35 g / cm3 1.36 g / cm3 3 or a range consisting of any two of the aforementioned numerical values.

[0375] The compaction density of the negative electrode film layer in the above range is beneficial to improve the energy density of the battery cell; and since the negative electrode active material in the negative electrode film layer is packed more closely, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing the heat generation.

[0376] In the embodiments of the present application, the compaction density of the negative electrode film layer of the battery cell at 100% state of charge is a meaning known in the art, which can be detected by using devices and methods known in the art, and the detection method is as follows:

[0377] In some embodiments, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm2 2 to 170 mg / 1540.25 mm2 2 , and optionally 110 mg / 1540.25 mm2 2 to 150 mg / 1540.25 mm2 2 Exemplarily, the single-sided coating weight of the negative electrode film layer is 90 mg / 1540.25 mm2 2 , 92 mg / 1540.25 mm2 2 , 95 mg / 1540.25 mm2 2 , 96 mg / 1540.25 mm2 2 , 100 mg / 1540.25 mm2 2 , 102 mg / 1540.25 mm2 2 , 104 mg / 1540.25 mm2 2 , 105 mg / 1540.25 mm2 2 , 108 mg / 1540.25 mm2 2 , 110 mg / 1540.25 mm2 2 , 112 mg / 1540.25 mm2 2 , 114 mg / 1540.25 mm2 2 , 115 mg / 1540.25 mm2 2 , 116 mg / 1540.25 mm2 2 , 118 mg / 1540.25 mm2 2 , 120 mg / 1540.25 mm2 2 , 122 mg / 1540.25 mm2 2 , 125 mg / 1540.25 mm2 2 , 128 mg / 1540.25 mm2 2130 mg / 1540.25 mm 2 132 mg / 1540.25 mm 2 135 mg / 1540.25 mm 2 137 mg / 1540.25 mm 2 140 mg / 1540.25 mm 2 142 mg / 1540.25 mm 2 145 mg / 1540.25 mm 2 148 mg / 1540.25 mm 2 150 mg / 1540.25 mm 2 152 mg / 1540.25 mm 2 155 mg / 1540.25 mm 2 160 mg / 1540.25 mm 2 165 mg / 1540.25 mm 2 170 mg / 1540.25 mm 2 or a range between any two of the above values.

[0378] When the single-side coating weight of the negative electrode film layer is within the above range, the heat generation per unit area of the negative electrode tab will not be too large, and the energy density of the battery monomer can be improved.

[0379] In the embodiments of the present application, the single-side coating weight of the negative electrode film layer has the meaning known in the art, and can be detected by using the devices and methods known in the art, and the detection method is as described in the foregoing single-side coating weight test method of the film layer.

[0380] In some embodiments, the powder resistivity of the negative active material is 0.005 Ω·cm to 0.043 Ω·cm, and can be 0.04 Ω·cm. Illustratively, the powder resistivity of the negative active material can be 0.043 Ω·cm, 0.04 Ω·cm, 0.035 Ω·cm, 0.03 Ω·cm, 0.025 Ω·cm, 0.02 Ω·cm, 0.015 Ω·cm, 0.01 Ω·cm, 0.005 Ω·cm, or a range between any two of the above values.

[0381] The relatively low powder resistivity of the negative active material makes the resistance of the negative electrode tab relatively low, and the battery monomer generates less heat.

[0382] In the embodiments of the present application, the powder resistivity of the negative active material has the meaning known in the art, and can be detected by using the devices and methods known in the art, and the detection method is as described in the foregoing powder resistivity test method of the positive active material.

[0383] In some embodiments, the powder compaction density of the negative active material under a pressure of 20000 N is 1.5 g / cm 3 to 1.85 g / cm 3 , optionally 1.55 g / cm 3 to 1.65 g / cm 3 . For example, the powder compaction density of the negative active material under a pressure of 20000 N is 1.5 g / cm 3 , 1.55 g / cm 3 , 1.6 g / cm 3 , 1.65 g / cm 3 , 1.7 g / cm 3 , 1.75 g / cm 3 , 1.8 g / cm 3 , 1.85 g / cm 3 , or a range defined by any two of the above values.

[0384] When the powder compaction density of the negative active material under a pressure of 20000 N is within the above range, the energy density of the battery cell can be improved, and the negative active material in the negative film layer can be more closely packed, the contact resistance between particles is smaller, which can further reduce the resistance of the electrode sheet, thereby reducing heat generation.

[0385] In the embodiments of the present application, the powder compaction density of the material is the meaning known in the art, which can be detected by the methods and devices known in the art according to the test standard GB / T24533-2009. For example, a certain amount of negative active material is taken as a sample, added to a mold with a bottom area of 1.327 cm 2 of a UTM7305 electronic pressure testing machine, pressurized to 2000 kg (equivalent to 20000 N), hold for 30 s, then release the pressure, keep for 10 s, then record and calculate the powder compaction density of the negative active material under the action of 20000 N force.

[0386] In some embodiments, the charge gram capacity of the negative active material at a rate of 0.1 C is 350 mAh / g to 480 mAh / g. For example, the charge gram capacity of the negative active material at a rate of 0.1 C is 350 mAh / g, 355 mAh / g, 360 mAh / g, 365 mAh / g, 370 mAh / g, 375 mAh / g, 380 mAh / g, 385 mAh / g, 390 mAh / g, 395 mAh / g, 400 mAh / g, 410 mAh / g, 420 mAh / g, 430 mAh / g, 440 mAh / g, 450 mAh / g, 460 mAh / g, 470 mAh / g, 480 mAh / g, or a range defined by any two of the above values.

[0387] When the charged gram capacity of the negative active material at the 0.1C rate is in the above range, the energy density of the battery cell is relatively high.

[0388] In the embodiments of the present application, the charged gram capacity of the negative active material at the 0.1C rate is in the meaning known in the art, which can be detected by using the equipment and method known in the art, and the detection method is as the charged gram capacity test method of the positive active material at the 0.1C rate as described above.

[0389] In some embodiments, the negative active material comprises a carbon-based material, which has high cycle stability and can improve the cycle performance of the battery cell. Optionally, the mass fraction of the carbon-based material in the negative active material can be greater than or equal to 80% and less than or equal to 100%.

[0390] The positive active material of the present application is mainly a lithium-containing phosphate system with an olivine structure, and the negative active material is mainly a carbon-based material system. The two are used together, and the cycle performance of the battery cell is relatively excellent.

[0391] Optionally, the carbon-based material comprises graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%. For example, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5% or a range composed of any two of the above values.

[0392] When the graphitization degree of the graphite particles is in the above range, the conductive performance of the graphite particles is relatively excellent, which can reduce the heat generation of the negative electrode sheet, reduce the heat generation of the battery cell, and improve the rapid charging performance of the battery cell.

[0393] In some embodiments, the graphite particles comprise artificial graphite and a carbon coating layer, the artificial graphite comprises secondary particles, the secondary particles comprise a plurality of primary particles, and the carbon coating layer is coated on the surface of the artificial graphite. The carbon in the carbon coating layer is mainly amorphous carbon, which refers to a transition state carbon material with a very low degree of graphitization and crystallization, and an approximate amorphous state (or a structure with no fixed shape and periodicity). In the present application, amorphous carbon refers to the product after carbonization treatment of an organic carbon source.

[0394] The artificial graphite comprises secondary particles, the migration path of lithium ions in the artificial graphite is relatively more, and the migration path in the primary particles is relatively short, which can improve the migration rate of lithium ions, the carbon coating layer has more end faces and defects, so that the number of sites capable of deintercalating lithium ions is more, and the conductivity of the carbon coating layer is relatively excellent, which can reduce the internal resistance of the negative electrode sheet and the heat generation of the battery cell.

[0395] Optionally, the mass content of the carbon coating layer is 2% to 5% based on the mass of the graphite particles. Illustratively, the mass content of the carbon coating layer is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range between any two of the above values.

[0396] When the mass content of the carbon coating layer is within the above range, the internal resistance of the negative electrode sheet can be further reduced, and the heat generation of the battery cell can be reduced.

[0397] In the embodiments 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 then forming a carbon coating layer on at least part of the surface of the artificial graphite particles after carbonization treatment.

[0398] Optionally, the organic carbon source includes one or more of coal tar pitch, petroleum pitch, phenolic resin, and coconut shell. Further optionally, the organic carbon source includes petroleum pitch. Optionally, the softening point of the coal tar pitch and the petroleum pitch is 250°C or lower.

[0399] Optionally, the carbonization treatment temperature is 700°C to 1800°C. Optionally, the carbonization treatment temperature is 1000°C to 1300°C. When the carbonization treatment temperature is within the appropriate range, the organic carbon source can be carbonized, and a coating layer containing amorphous carbon can be formed on at least part of the surface of the artificial graphite.

[0400] Optionally, the carbonization treatment time is 1h to 6h.

[0401] In some embodiments, the carbon-based material can further include natural graphite. Specifically, the carbon-based material can include graphite particles, or the carbon-based material can include graphite particles and natural graphite. Optionally, the carbon-based material is graphite particles.

[0402] In some embodiments, the negative electrode active material can further include a silicon-based material. The introduction of the silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell.

[0403] Optionally, the silicon element in the silicon-based material has a mass content of 0.3% to 10.0%, or 1% to 6%, based on the mass of the negative active material. For example, the silicon element in the silicon-based material has a mass content of 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 defined by any two of the above values.

[0404] The silicon element in the silicon-based material has a mass content in the above range, which can improve the capacity of the negative active material, and thus improve the energy density of the battery cell.

[0405] Optionally, the silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

[0406] In some embodiments, the negative active material can include at least one of tin-based material and lithium titanate in addition to the above-mentioned carbon-based material and optional silicon-based material. The tin-based material can include at least one of elemental tin, tin oxide, and tin alloy material.

[0407] The qualitative and quantitative detection of each substance or element in the present application can be performed by using suitable devices and methods known to those skilled in the art, and the relevant detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards, etc., and those skilled in the art can also adaptively change certain detection steps / instrument parameters, etc. from the perspective of detection accuracy to obtain more accurate detection results. One detection method can be used for qualitative or quantitative determination, or several detection methods can be used jointly for qualitative or quantitative determination.

[0408] For example, the negative electrode sheet or the negative active material can be subjected to X-ray powder diffraction test and qualitative analysis by JIS / K0131-1996 X-ray Diffraction Analysis Method General.

[0409] Artificial graphite and natural graphite can be distinguished by SEM cross-sectional SEM images taken by scanning electron microscope SEM, there are gaps between flaky structures in the SEM cross-sectional image of natural graphite, the SEM cross-sectional image of artificial graphite is dense and has no obvious gap, or distinguished by XRD spectrum obtained by X-ray diffraction method, there are obvious 2H phase and 3R phase in the XRD spectrum of natural graphite, and there is only 2H phase in the XRD spectrum of artificial graphite.

[0410] The negative electrode film layer in the embodiments of the present application includes at least one film layer, which can be a single layer film or at least two layers of film. Optionally, the negative electrode film layer includes at least two layers of film.

[0411] In the case of a single layer film, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally, a silicon-based material. In the case of a single layer film, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm to 13.5 μm. Illustratively, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, or a range defined by any two of the above values.

[0412] In the case of at least two layers of film, the negative electrode active material in the negative electrode film layer includes a carbon-based material, and optionally, a silicon-based material, which can be in one of the at least two layers of film or in at least two of the at least two layers of film. The negative electrode film layer can include two layers of film, three layers of film, four layers of film, or even more layers of film.

[0413] In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, the first negative electrode film layer is disposed on the surface of the negative electrode current collector, the carbon-based material in the first negative electrode film layer includes graphite particles, the second negative electrode film layer is connected to the side of the first negative electrode film layer away from the negative electrode current collector, 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 can be the same or different.

[0414] The interface of the first negative electrode film layer and the second negative electrode film layer can be regular or irregular, and is optionally irregular.

[0415] Optionally, the carbon-based material in the first negative electrode film layer further includes natural graphite.

[0416] The negative electrode film layer includes at least two layers of film, and the layered coating is conducive to improving the rapid charging performance of the battery cell. In particular, when the first negative electrode film layer and the second negative electrode film layer are different, the pore difference of the negative electrode film layer can be constructed, the tortuosity of lithium ion transmission is reduced, and the rapid charging performance of the battery cell is improved.

[0417] Optionally, the volume average particle size Dv50 of the negative active material in the first negative electrode film layer is greater than or equal to the volume average particle size Dv50 of the negative active material in the second negative electrode film layer. Further optionally, the volume average particle size Dv50 of the negative active material in the first negative electrode film layer is greater than the volume average particle size Dv50 of the negative active material in the second negative electrode film layer, which is conducive to improving the compaction density of the negative electrode film layer. When the negative active material comprises 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.

[0418] The difference in particle size in the first negative electrode film layer and the second negative electrode film layer can improve the rapid charging performance of the battery monomer. Specifically, during rapid charging, the overpotential of the second negative electrode film layer is generally high, and the bottleneck of rapid charging is mainly in the second negative electrode film layer. In the embodiments of the present application, the particle size in the second negative electrode film layer is relatively small, which can shorten the solid-phase transmission path of lithium ions, improve the rapid charging performance, and improve the problem of lithium extraction on the surface of the negative electrode sheet.

[0419] Optionally, the negative active material in the first negative electrode film layer is in the form of particles, and the volume average particle size Dv50 thereof is 9.5 μm to 18.5 μm, which can be 9.5 μm to 14.6 μm. Exemplarily, the volume average particle size of the negative 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 formed by any two of the above values. When the first negative electrode film layer comprises 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, which can be 9.5 μm to 14.6 μm.

[0420] When the volume average particle size Dv50 of the negative 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 rapid charging performance can be improved. On the other hand, the material is not prone to agglomeration during preparation, which can improve the stability of the material.

[0421] Optionally, the volume average particle size Dv50 of the negative active material in the second negative film layer is 7.8 μm to 14.3 μm, or 7.8 μm to 11.3 μm. For example, the volume average particle size Dv50 of the negative 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 defined by any two of the above values. When the second negative film layer comprises graphite particles, the volume average particle size Dv50 of the graphite particles in the second negative film layer is 7.8 μm to 14.3 μm, or 7.8 μm to 11.3 μm.

[0422] When the volume average particle size Dv50 of the negative active material in the second negative film layer is within the above range, on the one hand, the solid-phase transmission path of lithium ions can be shortened, and the rapid charging performance can be improved. On the other hand, the material is less likely to agglomerate during preparation, and the stability of the material can be improved. On the other hand, the negative active material in the second negative film layer and the negative active material in the first negative film layer cooperate to facilitate the construction of a gradient pore difference between the second negative film layer and the first negative film layer, reduce the tortuosity of lithium ion transmission, and improve the rapid charging performance of the battery cell.

[0423] In the embodiments of the present application, the volume average particle size Dv50 of the negative active material has the meaning known in the art, and can be detected by using the devices and methods known in the art. The detection method is as described above in the volume average particle size Dv50 test method of the positive active material.

[0424] Optionally, the tap density of the carbon-based material in the first negative film layer is less than or equal to the tap density of the carbon-based material in the second negative 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 film layer is greater than the tap density of the carbon-based material in the first negative film layer, the second negative film layer is more densely filled, so that the energy density of the battery cell is improved, and the first negative film layer is relatively sparse in filling, and the pores are more abundant, which can improve the rapid charging performance of the battery cell. When the negative active material comprises graphite particles, the tap density of the graphite particles in the first negative film layer is less than or equal to the tap density of the graphite particles in the second negative film layer.

[0425] Optionally, the tap density of the carbon-based material in the first negative film layer is 0.82 g / cm 3Up to 1.21 g / cm 3 For example, 0.82 g / cm³ 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 1.10 g / cm 3 1.12 g / cm 3 1.15g / cm 3 1.18 g / cm 3 1.20g / cm 3 1.21 g / cm 3 Or it can be a range consisting of any two of the above values. When the tap density of the carbon-based material in the first negative electrode film is within a suitable range, it can improve the fast charging performance of the battery cell.

[0426] Optionally, the tap density of the carbon-based material in the second negative electrode film is 0.90 g / cm³. 3 Up to 1.25 g / cm 3 For example, 0.90 g / cm³ 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 1.10 g / cm 3 1.12 g / cm 3 1.15g / cm 3 1.18 g / cm 3 1.20g / cm 3 1.21 g / cm 3 1.22g / cm 3 1.23g / cm 3 1.24 g / cm 3 1.25g / cm 3 Or it can be a range consisting of any two of the above values. When the tap density of the carbon-based material in the second negative electrode film is within a suitable range, it can improve the energy density of the battery cell.

[0427] In the embodiments of the present application, the tap density of the material is the meaning known in the art, which can be measured by instruments and methods known in the art. For example, GB / T 5162-2006 can be referred to, and a powder tap density tester can be used for measurement. The testing instrument can be Dandong Bitai BT-301.

[0428] Optionally, the ratio of the thickness of the second negative electrode film layer to the thickness of the first negative electrode film layer is 3:7 to 7:3, and optionally 4:6 to 6:4. For example, 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 formed by any two of the above values. By adjusting the thickness ratio of the first negative electrode film layer and the second negative electrode film layer, the gradient pore difference between the upper and lower layers can be further increased, the tortuosity of lithium ion transmission can be reduced, and the rapid charging capacity of the battery cell can be improved.

[0429] In some embodiments, after the battery cell is subjected to a full charge test cycle for 10 cycles at the beginning of life (BOL), the thickness of the first negative electrode film layer is 15 μm to 65 μm, for example, 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 formed by any two of the above values. When the thickness of the first negative electrode film layer is in the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be increased, the tortuosity of lithium ion transmission can be reduced, and the rapid charging capacity of the battery cell can be improved.

[0430] In some embodiments, after the battery cell is subjected to a full charge test cycle for 10 cycles at the beginning of life (BOL), the thickness of the second negative electrode film layer is 15 μm to 65 μm, for example, 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 formed by any two of the above values. When the thickness of the second negative electrode film layer is in the above range, the gradient pore difference between the first negative electrode film layer and the second negative electrode film layer can be adjusted and increased, the tortuosity of lithium ion transmission can be reduced, and the rapid charging capacity of the battery cell can be improved.

[0431] In the embodiments of the present application, for example, the upper limit voltage of battery charging is 3.65 V, and the discharge cut-off voltage of the battery is 2.0 V.

[0432] The BOL full charge test procedure is as follows: at 25°C, charge at a rate of 0.33C of the nominal capacity of the battery to 3.65V, then charge at a constant voltage of 3.65V to 0.05C, stand for 10 min, then discharge at a rate of 0.33C to 2.0V, stand for 10 min, the above one charge-discharge is one cycle, cycle 10 times, then charge at a rate of 0.33C of the nominal capacity of the battery to 3.65V, then charge at a constant voltage of 3.65V to 0.05C, which is the BOL full charge state, in the BOL full charge state, disassemble the negative electrode sheet, use a scanning electron microscope to observe the cross section in the thickness direction of the middle region of the negative electrode sheet, distinguish the two regions according to the interface between the first negative electrode film layer and the second negative electrode film layer, and measure the thicknesses of the two regions respectively, for example, measure the thicknesses of 10 positions of the first negative electrode film layer respectively, calculate the average value as the average value of the first negative electrode film layer, and measure the thicknesses of 10 positions of the second negative electrode film layer, calculate the average value as the average value of the second negative electrode film layer.

[0433] In some embodiments, after the battery cell is subjected to the End Of Life (EOL) full charge test, the thickness of the first negative electrode film layer is 15-70 μm, for example, 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 above values. When the thickness of the first negative electrode film layer is in the above range, the first negative electrode film layer and the second negative electrode film layer can regulate the increase of the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transmission, and improve the rapid charging capacity of the battery cell.

[0434] In some embodiments, after the battery cell is subjected to the End Of Life (EOL) full charge test, the thickness of the second negative electrode film layer is 15-70 μm, for example, 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 above values. When the thickness of the second negative electrode film layer is in the above range, the first negative electrode film layer and the second negative electrode film layer can regulate the increase of the gradient pore difference between the upper and lower layers, reduce the tortuosity of lithium ion transmission, and improve the rapid charging capacity of the battery cell.

[0435] In the embodiments 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.

[0436] The EOL full charge test procedure is as follows: at 60°C, charge to 3.65V at a charging rate of 0.33C of the nominal capacity of the battery, then charge to 0.05C at a constant voltage of 3.65V, stand for 10min, then discharge to 2.0V at a discharging rate of 0.33C, stand for 10min, the above one charge-discharge is one cycle, until the battery capacity decays to 80% of the nominal capacity to stop the test. Then charge to 3.65V at a constant current of 0.33C at 25°C, and charge to 3.65V at a constant voltage of 0.05C, which is the EOL full charge state. In the EOL full charge state, the negative electrode sheet is disassembled, and the thickness direction cross section of the middle region of the negative electrode sheet is observed using a scanning electron microscope. The first negative electrode film layer and the second negative electrode film layer are distinguished according to the interface, and the thicknesses of the two regions are measured, for example, the thicknesses of 10 positions of the first negative electrode film layer are measured, and the average value is calculated as the average value of the first negative electrode film layer. The thicknesses of 10 positions of the second negative electrode film layer are measured, and the average value is calculated as the average value of the second negative electrode film layer.

[0437] In some embodiments, in the case of using a single-layer film layer (different from the above-mentioned double-layer film layer) for the negative electrode film layer, the negative electrode film layer further comprises 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%. Illustratively, the mass content of the lithium-containing binder relative to the mass of the negative electrode film layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range composed of any two of the above values. The lithium element in the lithium-containing binder can exist in ionic form, which can increase the number of lithium ions that can move freely in the negative electrode film layer, shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, increase the de-intercalation rate of lithium ions, and improve the rapid charging performance of the battery monomer. Optionally, the negative electrode film layer can further comprise a negative electrode binder, for example, the negative electrode binder comprises at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0438] Optionally, the mass content of lithium element in the lithium-containing binder is 3% to 10%. Illustratively, the mass content of lithium element in the lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two of the above values. When the mass content of lithium element 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 of lithium ion diffusion to the surface of the negative electrode film layer, improve the deintercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0439] Illustratively, the lithium-containing binder includes lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer, and the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and hydroxyethyl acrylate monomer is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0440] The lithium-containing binder of the above material can provide a certain number of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and is not prone to swelling during charging and discharging, has a stable structure, and improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0441] In some other embodiments, when the negative electrode film layer includes at least two film layers, the negative electrode film layer further includes a lithium-containing binder.

[0442] 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, 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. 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.

[0443] 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 a relatively large number of lithium ions that can freely move in the second negative electrode film layer, which can further improve the rapid charging performance of the battery cell.

[0444] 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%. Illustratively, 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 defined by any two of the foregoing. The lithium element in the first lithium-containing binder can exist in the form of ions, can increase the number of lithium ions that move freely in the negative electrode film layer, can shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, can increase the deintercalation rate of lithium ions, and can improve the rapid charging performance of the battery cell.

[0445] Optionally, the mass content of the lithium element in the first lithium-containing binder is 3% to 10%, or 3% to 8%. Illustratively, the mass content of the lithium element in the first lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range defined by any two of the foregoing. When the mass content of the lithium element is in the foregoing range, the number of lithium ions that move freely in the negative electrode film layer can be relatively large, the distance of lithium ion diffusion to the surface of the negative electrode film layer can be further shortened, the deintercalation rate of lithium ions can be increased, and the rapid charging performance of the battery cell can be improved.

[0446] Illustratively, the first lithium-containing binder includes a lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer derived from lithium acrylate monomers, acrylonitrile monomers, acrylamide monomers, and hydroxyethyl acrylate monomers, and the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 30% to 50%: 15% to 45%: 5% to 20%: 20% to 35%. For example, the molar ratio of the lithium acrylate monomers, the acrylonitrile monomers, the acrylamide monomers, and the hydroxyethyl acrylate monomers is 35%: 30%: 15%: 20%, or 40%, 20%, 10%, 30%, or 45%, 15%, 20%, 20%, etc.

[0447] The lithium-containing binder of the foregoing material can provide a certain number of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and not easily swell during the charging and discharging process, thereby improving the structural stability and the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0448] 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%. Illustratively, 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 defined by any two of the foregoing. The lithium element in the second lithium-containing binder can exist in ionic form, which can increase the number of lithium ions that move freely in the negative electrode film layer, shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, increase the de-intercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0449] The first lithium-containing binder and the second lithium-containing binder can be made of the same material or different materials.

[0450] Optionally, the mass content of lithium element in the second lithium-containing binder is 3% to 10%, or 3% to 8%. Illustratively, the mass content of lithium element in the second lithium-containing binder is 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range defined by any two of the foregoing. When the mass content of lithium element is within the foregoing range, the number of lithium ions that move freely in the negative electrode film layer can be relatively large, which can further shorten the distance of lithium ion diffusion to the surface of the negative electrode film layer, increase the de-intercalation rate of lithium ions, and improve the rapid charging performance of the battery cell.

[0451] Illustratively, the second lithium-containing binder includes lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, which is derived from lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer, and 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%. 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.

[0452] The lithium-containing binder described above can provide a certain number of lithium ions for the negative electrode film layer, improve the rapid charging performance of the battery cell, and is not prone to swelling during charging and discharging, has a stable structure, and thus improves the cycle performance of the negative electrode film layer during rapid charging and discharging.

[0453] In some embodiments, the first negative electrode film layer further comprises a negative electrode binder, and the second negative electrode film layer further comprises 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 comprises at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0454] 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.

[0455] In some embodiments, the negative electrode film layer further optionally comprises a negative electrode conductive agent. The type of the negative electrode conductive agent is not particularly limited in the embodiments of the present application, and as an example, the negative electrode conductive agent can comprise at least one of super conductive 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 negative electrode conductive agent is ≤5% based on the total weight of the negative electrode film layer.

[0456] In some embodiments, the negative electrode film layer further optionally comprises a negative electrode binder. In some embodiments, the mass content of the negative electrode binder is ≤5% based on the total weight of the negative electrode film layer.

[0457] In some embodiments, the negative electrode film layer further optionally comprises other auxiliary agents. As an example, the other auxiliary agents can comprise thickening agents, dispersants, etc., such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass content of the other auxiliary agents is ≤2% based on the total weight of the negative electrode film layer.

[0458] In some embodiments, the negative electrode current collector can adopt a metal foil or a composite current collector. As an example of the metal foil, at least one foil of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy can be adopted. The composite current collector can comprise a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material in the metal material layer can comprise at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can comprise at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0459] In some embodiments, the thickness of the negative current collector is 4 μm to 10 μm, which can be 4 μm to 6 μm. For example, the thickness of the negative current collector is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 10 μm, or a range defined by any two of the above values.

[0460] When the thickness of the negative current collector is within the above range, the overcurrent capacity of the negative current collector is excellent, and the battery cell has a high energy density.

[0461] In the embodiments of the present application, the thickness of the negative current collector has the meaning known in the art, and can be detected by using the devices and methods known in the art, for example, the solvent is used to wash the film layer on the surface of the negative current collector, and the thickness of the negative current collector is measured by using a micrometer.

[0462] The negative film layer is usually formed by coating the negative slurry on the negative current collector, drying, and cold pressing. The negative slurry is usually formed by dispersing the negative active material, the optional conductive agent, the optional binder, and other optional additives in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0463] The negative electrode sheet does not exclude other additional functional layers in addition to the negative film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further comprises a negative conductive layer arranged between the negative current collector and the negative film layer and on the surface of the negative current collector. In some other embodiments, the negative electrode sheet of the embodiments of the present application further comprises a protective layer covering the surface of the negative film layer.

[0464] In some embodiments, the negative electrode sheet further comprises a negative conductive layer between the negative film layer and the negative current collector. The negative conductive layer can further improve the conductivity of the negative electrode sheet and reduce the heat generation of the negative electrode sheet, thereby reducing the heat generation of the battery cell.

[0465] In some embodiments, the thickness of the negative conductive layer is 0.5 μm to 2 μm. For example, the thickness of the negative 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 defined by any two of the above values.

[0466] When the thickness of the negative 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.

[0467] In the embodiments of the present application, the thickness of the negative electrode conductive layer is in the meaning known in the art, can be detected by using the devices and methods known in the art, and the test method of the negative electrode conductive layer is as described above.

[0468] In some embodiments, the negative electrode conductive layer comprises one or more of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent in the negative electrode conductive layer can improve the conductivity of the negative electrode conductive layer, thereby improving the conductivity of the negative electrode sheet, reducing the heat generation of the battery cell, and the negative electrode binder in the negative electrode conductive layer can improve the adhesion between the negative electrode current collector and the negative electrode film layer, thereby improving the structural stability of the negative electrode sheet.

[0469] In some embodiments, the negative electrode conductive layer can further optionally comprise other auxiliary agents. As an example, the other auxiliary agents can include thickening agents, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0470] Optionally, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 20% to 40%. Exemplarily, the mass content of the negative electrode conductive agent is 20%, 25%, 30%, 35%, 40%, or a range composed of any two of the above values.

[0471] Exemplarily, the negative electrode conductive agent comprises one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0472] Optionally, the mass content of the negative electrode binder in the negative electrode conductive layer is 60% to 80%. Exemplarily, the mass content of the negative electrode binder is 60%, 65%, 70%, 75%, 80%, or a range composed of any two of the above values.

[0473] Exemplarily, the negative electrode binder comprises one or more of styrene butadiene rubber SBR, water-soluble unsaturated resin SR-1B, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan.

[0474] In some embodiments, the ratio CB of the capacity of the unit area of the negative electrode film layer to the capacity of the unit area of the positive electrode film layer in the battery cell is 1.05 to 1.30, which can be optionally 1.07 to 1.15. Exemplarily, the ratio CB of the capacity of the unit area of the negative electrode film layer to the capacity of the 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 composed of any two of the above values.

[0475] When the ratio CB of the capacity of the unit area of the negative electrode film layer to the capacity of the unit area of the positive electrode film layer in the battery cell is in the above range, there are sufficient sites in the negative electrode film layer for lithium intercalation, which can reduce the risk of lithium precipitation and is beneficial to fast charging.

[0476] In the embodiments of the present application, the CB value is of the meaning known in the art and can be detected by using the devices and methods known in the art, for example, the capacity of the unit area of the negative electrode film layer and the capacity of the unit area of the positive electrode film layer are calculated respectively, and the ratio of the two is calculated to obtain the CB value.

[0477] Specifically, taking the battery charging upper limit voltage of 3.65V and the battery discharging cut-off voltage of 2.0V as examples,

[0478] The capacity of the unit area of the positive electrode film layer refers to the actual de-lithium 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 taken, and a CR2430 type half-button battery of positive electrode-lithium sheet is assembled. The area of the positive electrode sheet used is a mm 2 , wherein the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), then the assembled half-button battery is placed for 3h, the test is carried out at 25℃, 0.1C is used to charge (Charge) de-lithium in the voltage range of 2.0V to 3.65V, then 0.05C is used to discharge (Discharge) lithium intercalation to 2.0V, and the cycle is 2 times. The discharge capacity of the second cycle is taken as Y mAh. The actual battery design positive electrode sheet length is b mm, the width is c mm, and the number of positive electrode active material coated on the positive electrode current collector is d. Then the capacity of the unit area of the positive electrode film layer = Y / a*b*c*d.

[0479] Specifically, the capacity of the unit area of the negative electrode film layer refers to the actual lithium intercalation capacity of the negative electrode active material. The test method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the negative electrode sheet is taken, and a CR2430 type half-button battery of negative electrode-lithium sheet is assembled. The area of the negative electrode sheet used is f mm 2 , wherein the electrolyte is a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), then the assembled half-button battery is placed for 3h, the test is carried out at 25℃, 0.1C is used to charge (Charge) de-lithium in the voltage range of 2.0V to 3.65V, then 0.05C is used to discharge (Discharge) lithium intercalation to 2.0V, and the cycle is 2 times. The discharge capacity of the second cycle is taken as Y mAh. The actual battery design positive electrode sheet length is b mm, the width is c mm, and the number of positive electrode active material coated on the positive electrode current collector is d. Then the capacity of the unit area of the positive electrode film layer = Y / a*b*c*d.

[0480] [Separation film]

[0481] In the embodiments of the present application, the separator film comprises a base film with a porous structure.

[0482] In some embodiments, the base film comprises at least one of glass fiber, non-woven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the base film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0483] Optionally, the polyolefin comprises at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0484] In some embodiments, the porosity of the base film is 20% to 70%, and optionally 35% to 60%. For example, the porosity of the base film is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range between any two of the above values.

[0485] When the porosity of the base film is within the above range in the embodiments of the present application, the migration ability of lithium ions in the separator film can be improved, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0486] In the embodiments of the present application, the porosity refers to the percentage of the volume of the pores in the separator film to the total volume of the separator film. The porosity can be tested according to the standard GB / T 36363-2018 “Polyolefin Separator for Battery Cell”. It should be noted that, in the actual testing process, the testing process can be slightly different from the standard in order to obtain more accurate test values, in view of the differences in testing instruments, testing errors, and the like.

[0487] In some embodiments, the thickness of the base film is 6 μm to 12 μm, and optionally 6 μm to 9 μm. For example, the thickness of the base film is 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, or a range between any two of the above values.

[0488] When the thickness of the base film is within the above range, the migration path of lithium ions in the base film is shorter, and the internal resistance of the battery cell can be further reduced, thereby reducing heat generation.

[0489] In the embodiments of the present application, the separator film can be the base film. Optionally, the separator film further comprises a functional layer disposed on at least one side of the base film, and the functional layer can comprise inorganic particles to improve the heat resistance of the separator film. Optionally, the functional layer is disposed on both sides of the base film.

[0490] 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 the first inorganic particles, the second functional layer is located on the other side of the base film, and the second functional layer includes the composite particles, the composite particles include the second inorganic particles and the plurality of non-fluoropolymer particles, and the second inorganic particles are attached to the surface of the non-fluoropolymer particles and / or dispersed in the interior of the non-fluoropolymer particles.

[0491] The first functional layer and the second functional layer have good heat resistance, which can improve the heat resistance of the separator film.

[0492] Optionally, the first functional layer can include a binder, and optionally at least one of a fluorine-containing binder or a polyacrylic acid binder, such as polyvinylidene fluoride.

[0493] Optionally, the first inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. The above first inorganic particles can improve the heat resistance of the first functional layer.

[0494] In the embodiments of the present application, the thickness of the base film has the meaning known in the art, and can be detected using the meaning and equipment known in the art. For example, a newly prepared separator film can be taken as a sample, or a battery cell that has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) is disassembled in reverse, a separator film is obtained from the battery cell, and the separator film is dried and taken as a sample. The separator film is cut off using an ion beam cutting instrument to form a cross section, and then the thickness of the cross section of the separator film and each layer thereof is measured using a scanning electron microscope.

[0495] The non-fluoropolymer particles in the second functional layer refer to polymers that are non-fluorinated polymers. For example, the non-fluoropolymer particles include an acrylate copolymer. Optionally, the acrylate copolymer includes an acrylate-acrylonitrile-acrylamide-propylene copolymer. The acrylate copolymer has excellent bonding performance, and has high bonding stability with the base film. The molar ratio of each monomer in the copolymer can be any ratio, such as a molar ratio of 35%:30%:15%:20%, or 40%:20%:10%:30%, or 45%:15%:20%:20%, etc.

[0496] The second inorganic particles in the composite particles make it difficult for the non-fluoropolymer particles to adhere to each other due to high-temperature treatment in the granulation process, so that the composite particles have pores, which is beneficial to the transmission of lithium ions, improves the ion conductivity of the isolation film, and the second inorganic particles can also improve the compression modulus of the composite particles. In the charging and discharging process, the composite particles are less likely to deform, making the structure of the isolation film more stable, which can improve the kinetic performance of the battery monomer and improve the rapid charging performance. Optionally, compared with the first functional layer, the second functional layer is arranged close to the negative electrode plate. Due to the fact that the composite particles are less likely to deform, the isolation film is less likely to cause side effects such as extrusion to the negative electrode plate, so that the kinetic performance of the negative electrode plate is stable. Correspondingly, the first functional layer is arranged close to the positive electrode plate.

[0497] Optionally, the second inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide. Optionally, the second inorganic particles include silicon oxide. The above-mentioned second inorganic particles can improve the heat resistance of the second functional layer, and can form composite particles with non-fluoropolymers, further improving the cycle stability and kinetic performance of the isolation film, and improving the cycle performance and rapid charging performance of the battery monomer.

[0498] The average particle size of the second inorganic particles is 5 nm to 100 nm, optionally 10 nm to 100 nm, and optionally 5 nm to 20 nm. Illustratively, the average particle size of the second inorganic particles is 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or a range composed of any two of the above values. When the average particle size of the second inorganic particles is in the above range, it is beneficial to improve the heat resistance and compression modulus of the composite particles.

[0499] In the embodiments of the present application, the average particle size of the second inorganic particles has the meaning known in the art and can be detected by using devices and methods known in the art. For example, after obtaining the isolation film, the isolation film is dried as a sample, the isolation film is cut off using an ion beam cutter to form a cross section, and then the particle size of the second inorganic particles in the isolation film is measured using a scanning electron microscope. The particle sizes of a plurality of, for example, 50, second inorganic particles are measured, and the average value thereof is calculated as the average particle size of the second inorganic particles.

[0500] In some embodiments, the ion conductivity of the separator film is 0.3 mS / cm to 0.6 mS / cm. Exemplarily, the ion conductivity of the separator film 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 between any two of the above values.

[0501] When the ion conductivity of the separator film is in the above range, the migration ability of lithium ions of the separator film can be further improved, and the rapid charging performance of the battery cell can be improved.

[0502] In the embodiments of the present application, the ion conductivity of the separator film is in the meaning known in the art, and can be detected by using the devices and methods known in the art, for example,

[0503] Preparation of 2025 type button cell for testing: in a vacuum glove box, lithium sheet was put into the negative electrode shell, 150 μL of electrolyte was added, the electrolyte was a solution of 1 mol / L LiPF6 in EC / EMC / DEC = 3 / 5 / 2 (mass ratio), and then the separator film (area of 3.14 cm 2 , thickness of 12 μm) was put to make it close to the lithium sheet, 25 μL of electrolyte was added, and finally the positive electrode sheet (the positive electrode sheet can be the positive electrode sheet in Example 1) was placed thereon, and then the button cell was packaged. The assembled button cell was taken out from the vacuum glove box and placed for 24 h for the next step of testing.

[0504] Test: in an electrochemical workstation, the test was carried out in the frequency range of 10 -1 ~ 10 6 Hz, the resistance Rb of the separator film was obtained, and the ion conductivity σ (unit: mS / cm) was calculated by the following formula, σ = L / (R b × S)

[0505] Wherein: R b is the resistance of the separator film, and L and S are the thickness and area of the separator film to be tested, respectively.

[0506] [Electrolyte]

[0507] In some embodiments, the battery cell further comprises an electrolyte.

[0508] During the charging and discharging process of the battery cell, active ions such as lithium ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet, and the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0509] In the embodiments of the present application, the conductivity of the electrolyte at room temperature, for example, 25°C, is 10.5 mS / cm to 20 mS / cm, which can 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 formed by any two of the above values.

[0510] When the conductivity of the electrolyte at room temperature is in 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 the heat generation and improving the rapid charging performance of the battery cell.

[0511] In the embodiments of the present application, the conductivity of the electrolyte at room temperature is ionic conductivity, which can be detected by using the devices and methods known in the art, for example, by referring to the industry standard HG-T 4067-2015.

[0512] In some embodiments, the viscosity of the electrolyte at room temperature, for example, 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 formed by any two of the above values.

[0513] When the viscosity of the electrolyte is in 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 the heat generation and improving the rapid charging performance of the battery cell.

[0514] In the embodiments of the present application, the viscosity of the electrolyte is the meaning known in the art, which can be detected by using the devices and methods known in the art, for example, by referring to GB / T 10247-2008.

[0515] In some embodiments, the electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature, for example 25°C. For example, the electrolyte has a density of 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 defined by any two of the above values.

[0516] When the electrolyte has a density in 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 the heat generation and improving the rapid charging performance of the battery cell.

[0517] In the embodiments of the present application, the density of the electrolyte has the meaning known in the art and can be detected by using the devices and methods known in the art, for example, by referring to GB / T 2013-2010.

[0518] 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 the actual needs.

[0519] In some embodiments, the organic solvent includes a chain carboxylate solvent, and the mass content of the chain carboxylate solvent in the electrolyte is 6% to 65%, which can be selected as 25% to 60%. For example, the mass content of the chain carboxylate solvent is 6%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or a range defined by any two of the above values.

[0520] When the mass content of the chain carboxylate solvent is in the above range, the viscosity of the electrolyte system is relatively small, which is beneficial to the migration of lithium ions.

[0521] In some embodiments, the chain carboxylate solvent includes a compound represented by Formula I,

[0522] In Formula I,

[0523] R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 halogenated alkyl group,

[0524] R2 includes a C1 to C5 alkyl group or a C1 to C5 halogenated alkyl group.

[0525] The chain carboxylate solvent described above has a high conductivity, which is beneficial to improving the rapid charging capacity of the battery cell.

[0526] Alternatively, R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 halogenated alkyl group. Further alternatively, R1 includes a hydrogen atom, a halogen atom, a C1 to C2 alkyl group, or a C1 to C2 halogenated alkyl group.

[0527] Optionally, R2 comprises C1 to C3 alkyl or C1 to C3 haloalkyl. Further optionally, R2 comprises C1 to C2 alkyl or C1 to C2 haloalkyl.

[0528] In each of the above embodiments, the halogen atom comprises one or more of fluorine atom, chlorine atom, bromine atom and iodine atom, and optionally, the halogen atom comprises fluorine atom.

[0529] In each of the above embodiments, the haloalkyl comprises one or more of fluoroalkyl, chloroalkyl, bromoalkyl and iodoalkyl, and optionally, the haloalkyl comprises fluoroalkyl.

[0530] Exemplarily, the chain carboxylic acid ester solvent comprises one or more of compounds shown in formula I-1 to formula I-8,

[0531] In some embodiments, the organic solvent further comprises a carbonate solvent.

[0532] Optionally, the carbonate solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. Further optionally, the carbonate solvent comprises one or more of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate. The combination of the carbonate solvent and the chain carboxylic acid ester solvent improves the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0533] Further optionally, the mass content of the carbonate solvent in the electrolyte is 20% to 80%, and optionally 25.5% to 42.5%. Exemplarily, the mass content of the carbonate solvent in the electrolyte is 20%, 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 42.5%, 45%, 48%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or a range between any two of the above values. The carbonate solvent with the above mass content further improves the conductivity of the electrolyte at room temperature, which is beneficial to the migration of lithium ions.

[0534] Exemplarily, the carbonate solvent comprises one or more of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, and the mass content of the carbonate solvent is 20% to 80%.

[0535] In some embodiments, the electrolyte further comprises an additive, which can include a negative electrode film-forming additive, a positive electrode film-forming additive, and an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, and the like.

[0536] In some embodiments, the additive comprises one or more, optionally at least two, of a carbonate additive, a sulfur-containing additive, and a lithium salt additive. The additive is capable of improving the performance of the interface film on the positive electrode side and / or the negative electrode side, which is beneficial to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0537] In some embodiments, the mass content of the additive in the electrolyte is 1% to 10%, optionally 2% to 8%, and further optionally 3.5% to 8%. Illustratively, the mass content of the additive in the electrolyte is 1%, 2%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two of the foregoing values.

[0538] The additive in the above mass content is capable of effectively improving the performance of the interface film on the positive electrode side and / or the negative electrode side, which is beneficial to improving the rapid charging performance of the battery cell and improving the cycle performance.

[0539] Illustratively, the carbonate additive comprises one or more of vinylene carbonate VC and fluoroethylene carbonate FEC.

[0540] Illustratively, the sulfur-containing additive comprises one or more of vinyl sulfite DTD, bis vinyl sulfite 2-DTD, butylene sulfite BS, 1,3-propane sultone PS, ethylene sulfite ES, and methyl methylene disulfite MMDS.

[0541] Optionally, the lithium salt additive comprises one or more of lithium difluorophosphate LiPO2F2, lithium difluoro oxalate borate LiDFOB, lithium tetrafluoroborate LiBF4, and lithium bisoxalate borate LiBOB.

[0542] Optionally, the mass content of the vinylene carbonate VC in the electrolyte is 0.5% to 9%, and optionally 2% to 6%.

[0543] Optionally, the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%, and optionally 0.5% to 3%.

[0544] Optionally, the mass content of the vinylene carbonate VC in the electrolyte is 0.5% to 9%, and the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.1% to 4%.

[0545] Further optionally, the mass content of the vinylene carbonate VC in the electrolyte is 2% to 6%, and the mass content of the fluoroethylene carbonate FEC in the electrolyte is 0.5% to 3%.

[0546] In some embodiments, the electrolyte salt comprises a lithium salt, the lithium salt comprises one or more of a fluorine-containing sulfimide salt and lithium hexafluorophosphate LiPF6. The above lithium salt is easy to dissociate, is conducive to the rapid migration of lithium ions, and the electrolyte system is relatively stable and is not easy to decompose, which can improve the cycle performance of the battery cell.

[0547] Optionally, the fluorine-containing sulfimide salt comprises one or more of lithium bisfluorosulfimide LiFSI and lithium bis(trifluoromethylsulfonyl)imide LiTFSI.

[0548] Optionally, the lithium salt comprises lithium bisfluorosulfimide LiFSI and lithium hexafluorophosphate LiPF6, the molar concentration of lithium bisfluorosulfimide 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.

[0549] Illustratively, the molar concentration of lithium bisfluorosulfimide LiFSI is 0.4 mol / L to 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.7 mol / L.

[0550] Illustratively, the molar concentration of lithium bisfluorosulfimide LiFSI is 0.5 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.5 mol / L.

[0551] Illustratively, the molar concentration of lithium bisfluorosulfimide LiFSI is 0.2 mol / L, and the molar concentration of lithium hexafluorophosphate LiPF6 is 0.8 mol / L.

[0552] Optionally, the ratio of the molar concentration of lithium bisfluorosulfimide LiFSI to the molar concentration of lithium hexafluorophosphate LiPF6 is 0.2 to 1.0, and optionally 0.2 to 0.5. Illustratively, the ratio of the molar concentration of lithium bisfluorosulfimide LiFSI 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 composed of any two of the above values.

[0553] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt in the electrolyte are in the meanings known in the art, and can be detected by using the devices and methods known in the art, for example, the qualitative or quantitative analysis of the inorganic components / lithium salt in the electrolyte can be performed by ion chromatography according to the standard JY / T020-1996 "General Ion Chromatography Analysis Method". In the embodiments of the present application, the newly prepared electrolyte can be taken as the sample, the free electrolyte of the fresh battery can be taken as the sample, or the free electrolyte obtained from the battery which has been discharged to the lower limit cut-off voltage so that the charged state of the battery is about 0% SOC can be taken as the sample, and the ion chromatography analysis method is used for detection.

[0554] In the embodiments of the present application, the types and contents of the organic components in the electrolyte are in the meanings known in the art, and can be detected by using the devices and methods known in the art, for example, the qualitative and quantitative analysis of the organic components in the electrolyte can be performed by gas chromatography according to the standard GB / T9722-2006 "General Gas Chromatography Method for Chemical Reagents". In the embodiments of the present application, the newly prepared electrolyte can be taken as the sample, the free electrolyte of the fresh battery can be taken as the sample, or the free electrolyte obtained from the battery which has been discharged to the lower limit cut-off voltage so that the charged state of the battery is about 0% SOC can be taken as the sample, and the ion chromatography analysis method is used for detection.

[0555] In the embodiments of the present application, after the quantitative and qualitative detection of each component in the electrolyte, each component is classified, the chain carboxylic acid ester solvent, the carbonate solvent (for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate) is taken as the component of the organic solvent, and the mass content of each component is calculated based on 100% of the mass of the electrolyte.

[0556] The carbonate additive (for example, vinylene carbonate, fluoroethylene carbonate), the sulfur-containing additive and the lithium salt additive are taken as the additive of the electrolyte, and the mass content of each component is calculated based on 100% of the mass of the electrolyte.

[0557] In some embodiments, the battery cell satisfies: 2.45 g / Ah≤d / A≤3.5 g / Ah, which can be optionally 2.45 g / Ah≤d / A≤3.3 g / Ah, wherein d represents the mass of the electrolyte in the battery cell, in unit of g, and A represents the rated capacity of the battery cell, in unit of Ah. Exemplarily, d / A can be 3.5 g / Ah, 3.3 g / Ah, 3.2 g / Ah, 3.0 g / Ah, 2.8 g / Ah, 2.5 g / Ah, 2.45 g / Ah or a range composed of any two of the above values.

[0558] The d / A can reflect the liquid retention capability of the electrolyte. When the d / A is in the above range, the electrolyte can have a good infiltration effect on the positive electrode plate and the negative electrode plate, and can improve the migration rate of lithium ions in the liquid phase, which is beneficial to improving the rapid charging capability of the battery cell.

[0559] In the embodiments of the present application, the d / A of the battery cell can be understood as a liquid retention coefficient, which can be detected by using devices and methods known in the art. For example, according to GB / T31486-2015 “Power Accumulator for Electric Vehicles: Electrical Performance Requirements and Test Methods”, the upper limit voltage of battery charging is 3.65V, and the discharge cut-off voltage of the battery is 2.0V.

[0560] At 25°C, the battery cell is charged to 3.65V at 0.33C, then constant voltage charged to 0.05C, and then discharged to 2.0V at 0.33C to obtain the discharged capacity A as the denominator. The battery cell is weighed as M0, and then the positive electrode plate, the negative electrode plate, the separator and the electrolyte are disassembled, and the free electrolyte is in a bag. All the solid components are placed in a 60°C oven for more than 4 hours (including but not limited to the positive electrode plate, the negative electrode plate, the separator, and other mechanical parts of the disassembled battery cell contributing to M0), and then all the components of the battery cell are weighed as M1. The weight difference between M0 and M1 is taken as the numerator. The liquid retention coefficient is equal to the value obtained by dividing the weight difference between M0 and M1 by the capacity A.

[0561] In some embodiments, the positive electrode plate, the separator and the negative electrode plate can be made into an electrode assembly by a winding process and / or a stacking process.

[0562] As shown in FIG. 24, in some embodiments of the present application, the battery cell 7 according to the embodiments of the present application can be assembled into a battery module 6. The number of battery cells 7 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.

[0563] If the battery cell 7 is multiple, the multiple battery cells 7 can be connected in series or in parallel or in a mixed connection. The mixed connection means that there are both series connection and parallel connection among the multiple battery cells 7. The multiple battery cells 7 can be directly connected in series or in parallel or in a mixed connection, and then the whole of the multiple battery cells 7 is accommodated in the accommodation part of the battery module 6. Of course, the multiple battery cells 7 can be first connected in series or in parallel or in a mixed connection to form the battery module 6, and then the multiple battery modules 6 are connected in series or in parallel or in a mixed connection to form a whole, which is accommodated in the accommodation part. Alternatively, the battery module 6 can further include an accommodation part having an accommodation space, and the multiple battery cells 7 are accommodated in the accommodation space.

[0564] In some embodiments, the battery device can include a first busbar 61 for electrically connecting the first electrode terminal and a second busbar 62 for electrically connecting the second electrode terminal.

[0565] As shown in FIG. 25, in some embodiments, the above-mentioned battery module 6 can also be assembled into a battery 2, and the number of battery modules 6 contained in the battery 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.

[0566] The battery pack 2 can include a box 5 and a plurality of battery modules 6 arranged in the box 5. The box 5 includes a first box part 5a and a second box part 5b, and has a containing space 5c. The first box part 5a is used to cover the second box part 5b and form a closed space for containing the battery modules 6. The plurality of battery modules 6 can be arranged in the box 5 in any manner.

[0567] The first box part 5a and the second box part 5b are mutually covered, and together define the containing space 5c for containing the battery cells. The second box part 5b can be a hollow structure with one end open, and the first box part 5a can be a plate-shaped structure, which covers the open side of the second box part 5b to form the box 5 with the containing space 5c. Alternatively, the first box part 5a and the second box part 5b can both be hollow structures with one side open, and the open side of the first box part 5a covers the open side of the second box part 5b to form the box 5 with the containing space 5c. Of course, the first box part 5a and the second box part 5b can have various shapes, such as a cylinder or a cuboid.

[0568] To improve the sealing performance of the first box part 5a and the second box part 5b after being connected, a sealing member such as sealing glue or a sealing ring can be arranged between the first box part 5a and the second box part 5b.

[0569] Suppose the first box part 5a covers the top of the second box part 5b, the first box part 5a can also be referred to as an upper box cover, and the second box part 5b can also be referred to as a lower box.

[0570] 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 in which the battery pack 2 is located is, for example, 30°C.

[0571] 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 in which the battery pack 2 is located is 30°C.

[0572] In some embodiments, the battery pack 2 or any battery cell constituting the battery pack 2 includes a plurality of charging steps during charging from 10% state of charge to 80% state of charge, and the maximum state of charge of any charging step in the plurality of charging steps is less than or equal to 5% state of charge, for example, 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 between any two of the above values.

[0573] The battery pack 2 or any battery cell constituting the battery pack 2 includes a plurality of charging steps during charging from 10% state of charge to 40% state of charge, and for any charging step, the charging can be performed at any rate between 5C and 10C, and the charging rate corresponding to each charging step can be any value in the range of 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, 8.5C, 9C, 9.5C, 10C, or a range between any two of the above values.

[0574] For example, the charging steps of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% to 80% can be performed as follows:

[0575] charging from 10% SOC to 15% SOC at 5.0C constant current,

[0576] charging from 15% SOC to 20% SOC at 5.0C constant current,

[0577] charging from 20% SOC to 25% SOC at 5.0C constant current,

[0578] charging from 25% SOC to 30% SOC at 5.0C constant current,

[0579] charging from 30% SOC to 35% SOC at 5.0C constant current,

[0580] charging from 35% SOC to 40% SOC at 5.0C constant current,

[0581] charging from 40% SOC to 45% SOC at 4.6C constant current,

[0582] charging from 45% SOC to 50% SOC at 4.3C constant current,

[0583] charging from 50% SOC to 55% SOC at 4.0C constant current,

[0584] charging from 55% SOC to 60% SOC at 3.7C constant current,

[0585] charging from 60% SOC to 65% SOC at 3.4C constant current,

[0586] charging from 65% SOC to 70% SOC at 3.1C constant current,

[0587] charging from 70% SOC to 75% SOC at 2.9C constant current,

[0588] charging from 75% SOC to 80% SOC at 2.7C constant current.

[0589] In some embodiments, the charging time of the battery pack 2 or any battery cell constituting the battery pack 2 from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, optionally 5 min to 10.5 min, and the temperature of the external environment of the battery pack 2 at 10% state of charge is room temperature, for example, 30°C. For example, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min, or a range consisting of any two of the above values.

[0590] In some embodiments, the volumetric energy density of the battery cell is 390 Wh / L to 500 Wh / L, optionally 410 Wh / L to 470 Wh / L. For example, the volumetric energy density of the battery cell is 390 Wh / L, 400 Wh / L, 410 Wh / L, 420 Wh / L, 430 Wh / L, 440 Wh / L, 450 Wh / L, 460 Wh / L, 470 Wh / L, 480 Wh / L, 490 Wh / L, 500 Wh / L, or a range consisting of any two of the above values. The volumetric energy density of the battery cell is high.

[0591] In the embodiments of the present application, the volumetric energy density of the battery cell is the meaning known in the art, which can be detected by using the devices and methods known in the art. For example, taking 3.65V as the upper limit voltage of battery charging and 2.0V as the cut-off voltage of battery discharging as an example,

[0592] The battery cell is placed at 25°C, charged to 3.65V at 0.33C constant current, then charged at constant voltage to 0.05C, discharged to 2.0V at 0.33C constant current, and the discharge capacity A0 at this time is recorded, unit: Ah. The length, width, and height of the battery cell are measured by using a caliper (generally calculated based on the size of the shell of the battery, excluding the height of the electrode terminal, and excluding the insulating film outside the shell), the volume V0 of the battery cell is calculated, unit: L, and the volumetric energy density VED of the battery cell is (A0 x discharge platform voltage) / V0, unit: Wh / L.

[0593] In some embodiments, the battery cell has a weight energy density of 175 Wh / Kg to 210 Wh / Kg. For example, the battery cell has a weight energy density of 175 Wh / Kg, 180 Wh / Kg, 185 Wh / Kg, 190 Wh / Kg, 200 Wh / Kg, 210 Wh / Kg, or a range defined by any two of the above values. The battery cell has a high volume energy density.

[0594] In the embodiments of the present application, the weight energy density of the battery cell is in the meaning known in the art, and can be detected by using the devices and methods known in the art. For example, the battery is charged to a voltage of 3.65 V and discharged to a voltage of 2.0 V.

[0595] The battery cell is charged to 3.65 V at a constant current of 0.33 C and then charged to 0.05 C at a constant voltage. The battery cell is discharged to 2.0 V at a constant current of 0.33 C, and the discharge capacity A0 is recorded, in Ah. The mass of the electrode assembly in the battery cell is measured by using a card, and the weight energy density of the battery cell is calculated, in Wh / Kg.

[0596] Electric device

[0597] The second aspect of the embodiments of the present application provides an electric device. The electric device includes the battery device of the embodiments of the present application, such as a battery cell, a battery module, or a battery pack. The battery cell, the battery module, or the battery pack can be used as a power source of the electric device, or can be used as an energy storage unit of the electric device. The electric device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, and an electric tool, etc. The vehicle can be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile can be a pure electric vehicle, a hybrid electric vehicle, or a range extended electric vehicle, etc. The spacecraft includes an airplane, a rocket, a space shuttle, and a spacecraft, etc. The electric toy includes a fixed or mobile electric toy, such as a game machine, an electric automobile toy, an electric ship toy, and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling 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 electric drill, a concrete vibrator, and an electric planer, etc. The embodiments of the present application do not specially limit the above electric device.

[0598] The electric device can select the battery cell, the battery module, or the battery pack according to the use requirement.

[0599] FIG. 26 is a schematic diagram of an electric device 1 as an example. The electric device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the electric device 1, a battery pack or a battery module can be used.

[0600] The inside of the electric device 1 is provided with a battery pack 2, which can be arranged at the bottom or head or tail of the electric device 1. The battery pack 2 can be used for power supply of the electric device 1, for example, the battery pack 2 can be used as the operating power supply of the electric device 1, and also can be used as the driving power supply of the electric device 1, instead of or partially instead of fuel or natural gas to provide driving power for the electric device 1.

[0601] The electric device 1 can also include a controller 3 and a motor 4, the controller 3 is used to control the battery pack 2 to supply power for the motor 4, for example, for the working power demand of the electric device 1 during starting, navigation and driving.

[0602] As another example of the electric device can be a mobile phone, a tablet computer, a notebook computer, etc. The electric device generally requires thinning, and can use a battery monomer as a power supply.

[0603] The charging process of the electric device can select the following charging mode:

[0604] Charging from 10% SOC to 15% SOC at 5.0C constant current,

[0605] Charging from 15% SOC to 20% SOC at 5.0C constant current,

[0606] Charging from 20% SOC to 25% SOC at 5.0C constant current,

[0607] Charging from 25% SOC to 30% SOC at 5.0C constant current,

[0608] Charging from 30% SOC to 35% SOC at 5.0C constant current,

[0609] Charging from 35% SOC to 40% SOC at 5.0C constant current,

[0610] Charging from 40% SOC to 45% SOC at 4.6C constant current,

[0611] Charging from 45% SOC to 50% SOC at 4.3C constant current,

[0612] Charging from 50% SOC to 55% SOC at 4.0C constant current,

[0613] Charging from 55% SOC to 60% SOC at 3.7C constant current,

[0614] Charging from 60% SOC to 65% SOC at 3.4C constant current,

[0615] Charging from 65% SOC to 70% SOC at 3.1C constant current,

[0616] Charge from 70% SOC to 75% SOC at 2.9C constant current,

[0617] Charge from 75% SOC to 80% SOC at 2.7C constant current.

[0618] In some embodiments, the charging time of the electrical device from 10% state of charge to 80% state of charge is less than or equal to 10.5 min, optionally 5 min to 10.5 min, and the temperature of the external environment of the battery pack 2 at 10% state of charge is 30°C. Illustratively, the charging time of the battery pack 2 from 10% state of charge to 80% state of charge is 10.5 min, 10 min, 9.5 min, 9 min, 8.5 min, 8 min, 7.5 min, 7 min, 6.5 min, 6 min, 5.5 min, 5 min, or a range formed by any two of the above values.

[0619] Embodiment

[0620] The following examples further describe the present embodiments in more detail. These examples are provided only for illustrating the present embodiments and various modifications and changes can be made within the scope of the present embodiments. Unless otherwise stated, all parts, percentages and ratios reported herein are based upon the mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used without further purification, and the instruments used in the examples are commercially available.

[0621] Example 1-1

[0622] 1. Preparation of the positive electrode tab

[0623] The positive electrode tab includes a positive electrode current collector, a positive electrode conductive layer on the positive electrode current collector, and a positive electrode film layer. The positive electrode current collector is an aluminum foil, and the thickness of the aluminum foil is the same as the thickness of the positive electrode tab. The positive electrode conductive layer on the positive electrode current collector is a film layer formed by uniformly mixing a positive electrode conductive agent, superconducting carbon, and a positive electrode binder, polyvinylidene fluoride (PVDF), and a solvent, N-methyl pyrrolidone (NMP), and coating the mixture on the surface of the current collector. The thickness of the positive electrode conductive layer is 1 μm. The mass content of the positive electrode conductive agent in the positive electrode conductive layer is 40%, and the mass content of the positive electrode binder is 60%.

[0624] The positive electrode film layer includes a film layer formed by uniformly coating a positive electrode slurry (the solvent is N-methyl pyrrolidone (NMP)) on the surface of the positive electrode conductive layer, and 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.

[0625] The positive electrode active material includes lithium iron phosphate and a coating layer, the coating layer is coated on the surface of the lithium iron phosphate, the coating layer includes lithium iron titanium phosphate Li2FeTi(P04)3 and amorphous carbon. The Dv50 of the positive electrode active material is 1.6 μm, and the Dv10 is 0.64 μm.

[0626] The single-side coating weight of the positive electrode film layer is 290 mg / 1540.25 mm 2 .

[0627] 2. Preparation of the negative electrode tab

[0628] The negative electrode tab 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, the thickness of the copper foil is the same as the thickness of 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, a negative electrode binder, a thickening agent, and a solvent, and then coating the mixture on the surface of the negative electrode current collector, and the thickness of the film layer 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 thickening agent in the negative electrode conductive layer is 5%.

[0629] The negative electrode film layer includes a film layer formed by uniformly coating a negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode conductive layer, and then drying and cold pressing.

[0630] The single-side coating weight of the negative electrode film layer is 135 mg / 1540.25 mm 2 .

[0631] 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.

[0632] The first negative electrode film layer includes graphite particles, 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 thickening agent sodium carboxymethyl cellulose, and the mass ratio of the above components is 96.5:0.5:0.5:1.5:1. The mass content of lithium in the first lithium-containing binder is 4.8%. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and an amorphous carbon layer. The amorphous carbon layer is coated on the surface of the artificial graphite, and the mass content of the amorphous carbon is 3.5%.

[0633] The second negative electrode film layer comprises graphite particles, conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer), negative electrode binder styrene butadiene rubber, and thickening agent sodium carboxymethyl cellulose, with a mass ratio of 97.5:0.5:0.5:0.5:1; the mass content of lithium in the second lithium-containing binder is 4.8%; the Dv50 of the graphite particles is 11.3 μm; the graphite particles comprise artificial graphite and an amorphous carbon layer, and the amorphous carbon layer is coated on the surface of the artificial graphite, with a mass content of 3.5%.

[0634] 3. Separation film

[0635] The separation film comprises a base film, which is a 7 μm polyethylene film layer with a porosity of 42%.

[0636] 4. Preparation of electrolyte

[0637] The electrolyte comprises an organic solvent, a lithium salt, and an additive.

[0638] The organic solvent comprises 48.5% chain carboxylate solvents (ethyl acetate) and 32.5% carbonate solvents (24.5% ethylene carbonate EC, 8% dimethyl carbonate), and the mass content of each component in the organic solvent is calculated based on the mass of the electrolyte.

[0639] The additive has a mass content of 6.5% based on the mass of the electrolyte, and comprises vinylene carbonate VC, fluoroethylene carbonate FEC, ethylene sulfite ES, and lithium difluoro(oxalato)borate LiDFOB in a mass ratio of 5:0.5:0.5:0.5.

[0640] The lithium salt comprises 1 mol / L lithium hexafluorophosphate LiPF6.

[0641] The electrolyte has an electrical conductivity of 16.4 mS / cm at room temperature.

[0642] 5. Preparation of battery cell

[0643] The above positive electrode sheet, separation film, and negative electrode sheet are stacked in order with the separation film between the positive electrode sheet and the negative electrode sheet to play a separation role, and an electrode assembly is obtained through a winding process; the electrode assembly is placed in an outer packaging shell, electrolyte is injected after drying, and a battery cell is obtained through processes such as vacuum packaging, standing, formation, and shaping, with a compacted density of the positive electrode film layer being 2.60 g / cm 3 at 100% SOC and a compacted density of the negative electrode film layer being 1.25 g / cm 3 at 100% SOC.

[0644] Comparative Example 1-1

[0645] A battery cell was prepared in a similar manner to Example 1, except that the area of the projection surface of the positive electrode terminal and the area of the projection surface of the negative electrode terminal were adjusted.

[0646] Examples 1-2 to 1-8

[0647] A battery cell was prepared in a similar manner to Example 1, except that the size of the weld mark area of the welding part and the position of the weld mark were adjusted.

[0648] The specific parameters of the examples and comparative examples are shown in Tables 1 and 2.

[0649] Performance test

[0650] 1. Lithium precipitation area test of battery cell

[0651] At 60°C, the battery cell was charged at 1C constant current to a charge cut-off voltage of 3.65V, and then discharged at 1C constant current to 2.0V, which was one charge-discharge cycle; after 200 cycles, the negative electrode sheet in the battery pack was disassembled, the negative electrode sheet was unfolded, the lithium precipitation area (gray-white area) was observed, and the lithium precipitation area was measured.

[0652] 2. Cycle number of battery cell to 70% SOH

[0653] At 30°C, the battery cell was subjected to charge-discharge cycles until the cycle capacity retention rate (i.e. Cn / C0x100%) was 70%, and the cycle number was recorded. The more the cycle number, the better the cycle performance of the battery cell.

[0654] The charging step comprises the following steps:

[0655] charging from 0% SOC to 5% SOC at 5.0C constant current;

[0656] charging from 5% SOC to 10% SOC at 5.0C constant current;

[0657] charging from 10% SOC to 15% SOC at 5.0C constant current;

[0658] charging from 15% SOC to 20% SOC at 5.0C constant current;

[0659] charging from 20% SOC to 25% SOC at 5.0C constant current;

[0660] charging from 25% SOC to 30% SOC at 5.0C constant current;

[0661] charging from 30% SOC to 35% SOC at 5.0C constant current;

[0662] charged from 35% SOC to 40% SOC at 5.0 C;

[0663] charged from 40% SOC to 45% SOC at 4.6 C;

[0664] charged from 45% SOC to 50% SOC at 4.3 C;

[0665] charged from 50% SOC to 55% SOC at 4.0 C;

[0666] charged from 55% SOC to 60% SOC at 3.7 C;

[0667] charged from 60% SOC to 65% SOC at 3.4 C;

[0668] charged from 65% SOC to 70% SOC at 3.1 C;

[0669] charged from 70% SOC to 75% SOC at 2.9 C;

[0670] charged from 75% SOC to 80% SOC at 2.7 C;

[0671] charged from 80% SOC to 85% SOC at 1.8 C;

[0672] charged from 85% SOC to 90% SOC at 1.3 C;

[0673] charged from 90% SOC to 95% SOC at 0.7 C;

[0674] charged from 95% SOC to 98% SOC at 0.33 C;

[0675] charged from 98% SOC to 100% SOC at 0.1 C.

[0676] The end voltage of the last charging step in the above charging steps is 3.65 V.

[0677] The discharge strategy is as follows: discharged at 0.33 C to an end voltage of, for example, 2.0 V.

[0678] The test results are shown in Table 3.

[0679] Table 1

[0680] In Table 1, L1 represents the distance between the projected face of the soldered region of the positive electrode tab and the positive electrode lug in the thickness direction of the positive electrode terminal and the projected face of the soldered region of the positive electrode terminal and the positive electrode bus member in the thickness direction of the positive electrode terminal.

[0681] Table 2

[0682] In Table 2, L1 represents the distance between the projection plane of the soldered region of the negative tab and the negative tab along the thickness direction of the negative terminal and the projection plane of the soldered region of the negative terminal and the negative bus along the thickness direction of the negative terminal.

[0683] Table 3

[0684] In Table 1, the charging time of the battery cell in each example and the comparative example is less than or equal to 10.5 min at 10% SOC to 80% SOC.

[0685] In Comparative Example 1, the area of the projection plane of the positive terminal and the negative terminal along the thickness direction thereof is small, so that more heat is generated near the terminal, the cycle stability of the active material is poor, and the current density is too large, so that lithium precipitation is prone to occur.

[0686] In the examples of the present application, the area of the projection plane of the positive terminal along the thickness direction thereof is 200 mm 2 to 600 mm 2 ; and / or the area of the projection plane of the negative terminal along the thickness direction thereof is 200 mm 2 to 600 mm 2 ; so that less heat is generated near the terminal, the cycle stability of the active material is high, and lithium precipitation is not prone to occur, the use reliability is improved, and a certain weight energy density can be maintained.

[0687] Example 2-1

[0688] The battery cell was prepared by a method similar to that of Example 1-1, except that the electrode assembly was prepared by a lamination process, and the battery cell was prepared therefrom.

[0689] Comparative Example 2-1 and Example 2-2

[0690] The battery cell was prepared by a method similar to that of Example 2-1, except that the area of the projection plane of the positive terminal and the negative terminal was adjusted.

[0691] Test Results

[0692] Table 4

[0693] In Table 4, the charging time of the battery cell in each example and the comparative example is less than or equal to 10.5 min at 10% SOC to 80% SOC.

[0694] In Comparative Example 2-1, the area of the projection plane of the positive terminal and the negative terminal along the thickness direction thereof is large, for example, greater than 600 mm 2The lithium precipitation is not easy to occur, but the weight energy density is reduced.

[0695] The area of the projection surface of the positive electrode terminal along the thickness direction of the positive electrode terminal is 200mm 2 to 600mm 2 ; and / or the area of the projection surface of the negative electrode terminal along the thickness direction of the negative electrode terminal is 200mm 2 to 600mm 2 ; so that the heat generated near the terminal is less, the cycle stability of the active material is higher, the lithium precipitation is not easy to occur, the use reliability is improved, and a certain weight energy density can be maintained.

[0696] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be interpreted as a limitation of the present application, and the embodiments can be changed, replaced and modified without departing from the spirit, principles and scope of the present application.

Claims

1. A battery cell, comprising: a housing assembly including a housing and a first electrode terminal provided to the housing; and an electrode assembly accommodated in the housing, the electrode assembly including a first tab and a second tab, each of the first tab and the second tab including a coated portion including an active material layer and a tab not provided with the active material layer, wherein one of the first tab and the second tab is a positive electrode tab, and the other is a negative electrode tab, the active material layer in the positive electrode tab includes a positive electrode active material including a lithium-containing phosphate having an olivine structure, and the tab in the first tab is used to electrically connect the first electrode terminal and the coated portion in the first tab, The area of the projection of the first electrode terminal along the thickness direction thereof is 200mm 2 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.

2. The battery cell of claim 1, wherein, The area of the projection face of the first electrode terminal is 300mm 2 up to 500mm 2 .

3. The battery cell of claim 1 or 2, wherein, the tab in the first tab is directly connected to the first electrode terminal.

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

5. The battery cell of claim 3 or 4, wherein, the first electrode terminal includes a carrier portion having a hollow structure, the carrier portion accommodates at least a portion of the tab in the first tab, and an inner wall of the carrier portion is connected to the tab in the first tab. 6.The battery cell according to claim 5, wherein the inner wall includes an end wall and a side wall, the side wall is provided around the end wall, the tab in the first tab is connected to the end wall, and / or the tab in the first tab is connected to the side wall. 7.The battery cell according to claim 1 or 2, comprising a first adapter connecting the tab of the first tab and the first electrode terminal.

8. The battery cell of claim 7, wherein, the housing includes an electrode lead-out hole, the first electrode terminal covers the electrode lead-out hole, and the first electrode terminal is provided to a side of the housing facing away from the coated portion.

9. The battery cell of claim 7 or 8, wherein, The area of the connecting region of the first adapter and the first electrode terminal is 35mm 2 to 50mm 2 .

10. The battery cell of any one of claims 7-9, wherein, An area of a connection region of the first lug and the first adapter is 80mm 2 to 160mm 2 .

11. The battery cell of any one of claims 7-10, wherein, The first electrode terminal is used to be connected with an external first bus member, and an area of a connection region of the first electrode terminal with the first bus member is 60mm 2 to 150mm 2 . 12.The battery cell according to any one of claims 7 to 11, wherein the first adapter is located between the first tab and the first electrode terminal, a projection plane of a connection region of the first adapter to the first tab along a thickness direction of the first electrode terminal is a first projection plane, the first electrode terminal is used to connect to a first busbar outside, a projection plane of a connection region of the first electrode terminal to the first busbar along the thickness direction of the first electrode terminal is a second projection plane, and wherein a distance between a geometric center of the first projection plane and a geometric center of the second projection plane is 0 to 50 mm.

13. The battery cell of any one of claims 7-12, wherein, the first adapter is a positive electrode adapter, a thickness of the positive electrode adapter is 0.6 mm to 2.0 mm; and / or The cross-sectional area of the positive electrode adapter perpendicular to the thickness direction thereof is 30 mm 2 to 60 mm 2 .

14. The battery cell of any one of claims 7-12, wherein, the first adapter is a negative electrode adapter, a thickness of the negative electrode adapter is 0.5 mm to 1.5 mm; and / or The cross-sectional area of the negative electrode adapter perpendicular to the thickness direction thereof is 24 mm 2 up to 60 mm 2 .

15. The battery cell of any one of claims 1-14, wherein, The tab in the first tab sheet is a positive electrode tab, and a cross-sectional area of the positive electrode tab close to one side of the coated portion is 0.45 mm 2 to 1.0 mm 2 .

16. The battery cell of any one of claims 1-14, wherein, The tab in the first tab sheet is a negative electrode tab, and the cross-sectional area of the negative electrode tab close to one side of the coated portion is 0.18mm 2 to 1.0mm 2 .

17. The battery cell of any one of claims 1-16, wherein, the electrode assembly is a stacked structure, the first tab and the second tab are stacked along a thickness direction of the electrode assembly, The first electrode terminal and the tab of the first tab piece are connected, and the area of the connection region of the first electrode terminal and the tab of the first tab piece is 140 mm 2 to 420 mm 2 .

18. The battery cell of any one of claims 1-17, wherein, the first electrode terminal is a plurality of, the plurality of first electrode terminals are located on both sides of the coated portion; or the plurality of first electrode terminals are located on the same side of the coated portion.

19. The battery cell of claim 17 or 18, wherein, The first electrode terminal is at least two on the same side of the coating part.

20. The battery cell of any one of claims 1-19, wherein, The housing assembly further includes a second electrode terminal disposed at the housing, a tab in the second tab is used to electrically connect the second electrode terminal and the coated portion in the second tab, and the projection area of the second electrode terminal along the projection surface in the thickness direction thereof is 200mm 2 to 600mm 2 .

21. The battery cell of any one of claims 1-20, wherein, The shell comprises a housing and an end cover, the housing is a cuboid structure, the housing contains the electrode assembly, and the housing has an opening, the end cover covers the opening, and the first electrode terminal is arranged on the end cover; The size of the projection of the first electrode terminal along its own thickness direction in the thickness direction of the battery cell is a first size, the size of the end cover in the thickness direction of the battery cell is a second size, and the ratio of the first size to the second size is greater than 0 and less than or equal to 0.

85.

22. The battery cell of claim 21, wherein, The ratio of the first size to the second size is 0.40 to 0.

85.

23. The battery cell of any one of claims 1-22, wherein, The electrode assembly is a wound structure, the first and second pole pieces are wound in one direction, In the direction from the coating part to the end cover of the shell, the size of the coated part of the first pole piece is 60mm to 120mm.

24. The battery cell of any one of claims 1-22, wherein, The electrode assembly is a stacked structure, the first and second pole pieces are stacked in the thickness direction of the battery cell, In the direction from the coating part to the end cover of the shell, the size of the coated part of the first pole piece is 300mm to 550mm.

25. The battery cell of any one of claims 1-24, wherein, The electrode assembly is a wound structure, the first and second pole pieces are wound in one direction, and the projection of the first electrode terminal along its own thickness direction is circular.

26. The battery cell of any one of claims 1-24, wherein, The electrode assembly is a stacked structure, the first and second pole pieces are stacked in the thickness direction of the battery cell, and the projection of the first electrode terminal along its own thickness direction is rectangular.

27. The battery cell of any one of claims 1 to 26, wherein, The first pole piece is a positive pole piece; or the first pole piece is a negative pole piece.

28. The battery cell of any one of claims 1-27, wherein, The coated part of the first pole piece comprises a first flat section, the coated part of the second pole piece comprises a second flat section, the first flat section and the second flat section are stacked in the thickness direction of the electrode assembly, and the ratio of the number of tabs of the first pole piece to the number of first flat sections of the first pole piece is 0.5 to 2, The battery cell further comprises an electrolyte, the electrolyte comprises an organic solvent, the organic solvent comprises a chain carboxylate solvent, and the mass content of the chain carboxylate solvent in the electrolyte is 6% to 65%.

29. The battery cell of claim 28, wherein, The mass content of the chain carboxylate solvent in the electrolyte is 25% to 60%.

30. The battery cell of claim 28 or 29, wherein, The ratio of the number of tabs of the second pole piece to the number of second flat sections of the second pole piece is 0.5 to 2.

31. The battery cell of any one of claims 28-30, wherein, The electrode assembly is a wound structure, the first and second pole pieces are wound in one direction, and the first pole piece has a plurality of tabs.

32. The battery cell of claim 31, wherein, The ratio of the number of tabs of the first pole piece to the number of first flat sections of the first pole piece is 0.5 to 1.

33. The battery cell of any one of claims 28-30, wherein, The electrode assembly is a stacked structure, and the first and second pole pieces each have a plurality of tabs, and each of the first pole pieces has at least one tab.

34. The battery cell of claim 33, wherein, The ratio of the number of tabs of the first pole piece to the number of first flat sections of the first pole piece is 1 to 2.

35. The battery cell of any one of claims 1-34, wherein, The tab includes: a tab body connected to the coated portion; and a plurality of tab protrusions each connected to a side of the tab body away from the coated portion, and having a gap between adjacent tab protrusions, each of the tab protrusions being configured to be electrically connected to the electrode terminal.

36. The battery cell of any one of claims 1-35, wherein, The tab in the first tab sheet is a positive electrode tab, and the thickness of the positive electrode tab is 10 μm to 20 μm.

37. The battery cell of any one of claims 1-35, wherein, The tab in the first tab sheet is a negative electrode tab, and the thickness of the negative electrode tab is 4 μm to 10 μm.

38. The battery cell of any one of claims 1-37, wherein, The electrolyte has an electrical conductivity of 10.5 mS / cm to 20 mS / cm at room temperature.

39. The battery cell of claim 38, wherein, The electrolyte has an electrical conductivity of 15 mS / cm to 20 mS / cm at room temperature.

40. The battery cell of any one of claims 1-39, wherein, The chain carboxylate-based solvent includes a compound represented by Formula I, In formula I, R1 includes a hydrogen atom, a halogen atom, a C1 to C5 alkyl group, or a C1 to C5 haloalkyl group, R2 includes a C1 to C5 alkyl group or a C1 to C5 haloalkyl group.

41. The battery cell of claim 40, wherein: R1 includes a hydrogen atom, a halogen atom, a C1 to C3 alkyl group, or a C1 to C3 haloalkyl group, R2 includes a C1 to C3 alkyl group or a C1 to C3 haloalkyl group.

42. The battery cell of claim 40 or 41, wherein: The halogen atom includes a fluorine atom, and / or the haloalkyl group includes a fluoroalkyl group.

43. The battery cell of any one of claims 28-42, wherein, The chain carboxylate-based solvent includes one or more of compounds represented by Formula I-1 to Formula I-8, 44. The battery cell of any one of claims 28-43, wherein, The organic solvent further includes a carbonate-based solvent, and the carbonate-based solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

45. The battery cell of claim 44, wherein, The carbonate-based solvent has a mass content of 20% to 80% in the electrolyte.

46. The battery cell of any one of claims 28-45, wherein, The electrolyte further includes an additive, and the additive includes one or more of a carbonate-based additive, a sulfur-containing additive, and a lithium salt-based additive.

47. The battery cell of claim 46, wherein, The carbonate-based additive includes one or more of vinylene carbonate and fluoroethylene carbonate, and / or The sulfur-containing additive includes one or more of vinyl sulfates, bis vinyl sulfates, butylene sulfite, 1,3-propane sultone, vinyl sulfite, and methylidene methylene sulfite, and / or The lithium salt-based additive includes one or more of lithium difluorophosphate, lithium difluoro oxalate borate, lithium tetrafluoroborate, and lithium bis-oxalate borate.

48. The battery cell of claim 46 or 47, wherein, The additive has a mass content of 1% to 10% in the electrolyte.

49. The battery cell of any one of claims 28-48, wherein, The electrolyte further includes a lithium salt, and the lithium salt includes one or more of a fluorine-containing sulfimide salt and lithium hexafluorophosphate.

50. The battery cell of claim 49, wherein, The fluorine-containing sulfimide salt includes one or more of lithium bis-fluorosulfimide and lithium bis-trifluoromethylsulfonamide.

51. The battery cell of claim 50, wherein, The lithium salt includes lithium bis-fluorosulfimide and lithium hexafluorophosphate, the molar concentration of the lithium bis-fluorosulfimide 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.

52. The battery cell of any one of claims 28 to 51, wherein: The electrolyte has a viscosity of 2.3 mPa s to 3.5 mPa s at room temperature; and / or The electrolyte has a density of 1.05 g / mL to 1.35 g / mL at room temperature.

53. The battery cell of any one of claims 1-52, wherein, The lithium-containing phosphate of olivine structure includes: phosphate particles, and phosphate particles, and a coating layer that coats the phosphate particles, the coating layer containing one or more elements of C, Fe, Ti, Zr, Hf, Ge, and Sn.

54. The battery cell of claim 53, wherein, The phosphate particles include a compound of a general formula of Li x1 A y1 Me a M b P 1-c X c Y z , wherein 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.9≤x1+y1≤1.3, 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5, 0≤c≤0.5, 3≤z≤5, A includes one or more of Na, K, Mg, Me includes one or more of Mn, Fe, Co, 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, Ce, X includes one or more of S, Si, Cl, B, C, N, and Y includes one or more of O, F.

55. The battery cell of claim 53 or 54, wherein, The coating layer includes a general formula of Li 3-d Fe 2- d M2 d (PO x2 ) y2 a fast ion conductor, M2 includes one or more elements of Ti, Zr, Hf, Ge, and Sn, 0≤d≤1, 0 56. The battery cell of any one of claims 53-55, wherein, The graphitization degree of the olivine-structure lithium-containing phosphate is 0.15 to 0.

32.

57. The battery cell of claim 56, wherein, The graphitization degree of the olivine-structure lithium-containing phosphate is 0.19 to 0.

26.

58. The battery cell of any one of claims 53-57, wherein, The mass content of carbon element in the olivine-structure lithium-containing phosphate is 1% to 2%, The lithium-containing phosphate of olivine structure has a specific surface area of 5 m 2 / g to 18 m 2 / g.

59. The battery cell of claim 58, wherein, The lithium-containing phosphate of olivine structure has a specific surface area of 7.5 m 2 / g to 14 m 2 / g.

60. The battery cell of any one of Claims 1-59, wherein, The olivine-structure lithium-containing phosphate is in a particulate form, and the volume distribution particle size satisfies 1 μm≤Dv50≤2 μm, 0.4 μm≤Dv10≤0.7 μm.

61. The battery cell of any one of claims 1-60, wherein, The olivine-structure lithium-containing phosphate is in a particulate form, and the olivine-structure lithium-containing phosphate includes secondary particles, and the secondary particles include a plurality of primary particles, and the average particle size of the primary particles is 200 nm to 500 nm.

62. The battery cell of any one of claims 1-61, wherein, The negative electrode tab includes a negative electrode active material, and the negative electrode active material includes a carbon-based material, and the carbon-based material includes graphite particles, and the graphitization degree of the graphite particles is 92.0% to 94.5%.

63. The battery cell of claim 62, wherein, The graphite particles include: artificial graphite including secondary particles, and a carbon coating layer coated on the surface of the artificial graphite.

64. The battery cell of claim 63, wherein, Based on the mass of the graphite particles, the mass content of the carbon coating layer is 2% to 5%.

65. The battery cell of any one of claims 1 to 64, comprising a casing that houses the electrode assembly, the casing comprising steel, the thickness of the casing being 0.1 mm to 0.5 mm.

66. The battery cell of claim 65, wherein, The thickness of the casing is 0.2 mm to 0.35 mm.

67. A battery device comprising a plurality of battery cells as recited in any one of claims 1 to 66, the battery device having a charging time of 5 min to 10.5 min from 10% state of charge to 80% state of charge.

68. The battery device of claim 67, comprising a first bus member, The first bus bar is electrically connected with a first electrode terminal in the battery monomer, and an area of a connection region of the first bus bar with the first electrode terminal is 60mm 2 to 150mm 2 .

69. The battery device of claim 68, wherein, the first adapter of the battery cell is located between the first tab of the battery cell and the first electrode terminal; the projection area of the connection area of the first adapter and the first tab along the thickness direction of the first electrode terminal is a first projection area; the projection area of the connection area of the first electrode terminal and the first bus member along the thickness direction of the first electrode terminal is a second projection area, wherein the distance between the geometric center of the first projection area and the geometric center of the second projection area is 0 to 50 mm.

70. An electric device comprising the battery device of any one of claims 67 to 69.

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