Battery cells, battery devices, and electrical equipment

Abstract

The present application discloses a battery cell, a battery device, and an electrical equipment. The battery cell includes a positive electrode sheet and a negative electrode sheet, the positive electrode sheet includes a positive electrode coating portion and a positive electrode tab, the negative electrode sheet includes a negative electrode coating portion and a negative electrode tab, the positive electrode coating portion includes a positive electrode straight section, the negative electrode coating portion includes a negative electrode straight section, the positive electrode straight section and the negative electrode straight section are stacked along the thickness direction of the electrode assembly, the number of positive electrode tabs is n1, the number of positive electrode straight sections is n2, and the ratio of n1 to n2 is 3 / 4-1. The adapter plate includes an end face close to the side wall of the shell, and a first gap is formed between the end face and the inner wall of the side wall for accommodating the positive electrode tab. The size of the first gap is 2.5mm-8mm. Along the height direction of the battery cell, the adapter plate has a surface facing the electrode assembly, and a second gap is formed between the surface and the edge of the negative electrode active material layer for accommodating the positive electrode tab. The size of the second gap is 4.5mm-7.5mm.

Description

[0001] This application claims priority to PCT international application No. PCT / CN2025 / 092196, filed on April 29, 2025, entitled “Battery Cell, Battery Device, and Electrical Equipment,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of batteries, and in particular, to battery cells, battery devices, and electrical equipment. Background Art

[0003] Currently, market developments indicate that batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. As battery applications continue to expand, market demand is also growing. However, current battery cells cannot achieve both fast charging performance and energy density. Summary of the Invention

[0004] The present application provides a battery cell, the battery cell comprising a housing assembly and an electrode assembly, the electrode assembly being accommodated in the housing assembly, the housing assembly comprising a shell and a cover assembly, the cover assembly covering the shell, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, the cover assembly comprising a cover and an electrode terminal; wherein,

[0005] The positive electrode sheet includes a positive electrode coating portion and a positive electrode tab, wherein the positive electrode coating portion is coated with a positive electrode active material layer, wherein the positive electrode active material layer includes a lithium-containing phosphate; the negative electrode sheet includes a negative electrode coating portion and a negative electrode tab, wherein the negative electrode coating portion is coated with a negative electrode active material layer, wherein the negative electrode active material layer includes graphite; and the positive electrode tab and the negative electrode tab are both electrically connected to the electrode terminal via an adapter sheet;

[0006] The positive electrode coating portion includes a positive electrode straight segment, and the negative electrode coating portion includes a negative electrode straight segment. The positive electrode straight segments and the negative electrode straight segments are stacked along the thickness direction of the electrode assembly. The number of the positive electrode tabs is n1, and the number of the positive electrode straight segments is n2. The ratio of n1 to n2 is 3 / 4-1, and the range of n1 is 110-220, and the unit is: piece;

[0007] The adapter sheet is a sheet-shaped conductive part, the shell assembly includes a shell, the positive electrode tab includes a bending portion and a welding portion, along the thickness direction of the battery cell, the adapter sheet includes an end face close to the side wall of the shell, and a first gap is formed between the end face and the inner wall of the side wall for accommodating the positive electrode tab, wherein the size of the first gap is 2.5mm-8mm; along the height direction of the battery cell, the adapter sheet has a surface facing the electrode assembly, and a second gap is formed between the surface and the edge of the negative electrode active material layer for accommodating the positive electrode tab, wherein the size of the second gap is 4.5mm-7.5mm.

[0008] The battery cell proposed in this application can increase the area of ​​active material and the energy density of the battery cell by controlling the size of the first gap and the second gap within an appropriate range. At the same time, it can reduce the probability of an increase in the interlayer spacing between the pole pieces due to the insertion of the folded pole ear into the active material layer, thereby improving the cycle performance of the battery cell under fast charging conditions.

[0009] According to some embodiments of the present application, along the height direction of the battery cell, the positive electrode tab extends from the positive electrode straight section, and the negative electrode tab extends from the negative electrode straight section. This increases the area ratio of the active area on the positive and negative electrode tabs, thereby improving the energy density of the battery cell.

[0010] According to some embodiments of the present application, the size of the adapter plate along the height direction of the battery cell is 0.6 mm to 2 mm, thereby reducing the space occupied by the adapter plate in the height direction of the battery cell.

[0011] According to some embodiments of the present application, the adapter sheet has a size of 15 mm to 60 mm along the thickness direction of the battery cell, thereby reducing heat generation under fast charging conditions and improving the cycle life of the battery cell.

[0012] According to some embodiments of the present application, the welding portion of the positive electrode tab and the adapter are welded to form a welding area, and the area of ​​the welding area is 10mm 2 -40mm 2 Thus, the firmness of the welding between the adapter and the tab is improved.

[0013] According to some embodiments of the present application, the battery cell has a size of 120 mm to 350 mm along its width, 80 mm to 120 mm along its height, and 25 mm to 80 mm along its thickness, thereby increasing the energy density of the battery cell.

[0014] According to some embodiments of the present application, along the width direction of the positive electrode sheet, the positive electrode tab includes a hollow foil area and an inorganic coating area, and the inorganic coating area is located between the positive electrode coating portion and the hollow foil area, wherein:

[0015] The hollow foil area is used to electrically connect to the electrode terminal. The inorganic coating area includes an inorganic coating, which includes inorganic particles and a binder. Along the width of the positive electrode sheet, the size of the inorganic coating occupies 1 / 15 to 1 / 4 of the size of the positive electrode tab. This reduces the probability of direct contact between the positive electrode tab and the negative electrode sheet, reducing the risk of short circuit between the positive and negative electrodes.

[0016] According to some embodiments of the present application, the coating portion includes an active area and an inactive area, the positive electrode active material layer is located in the active area, and the inactive area is located between the inorganic coating area and the active area and connected to the inorganic coating area and the active area. The inactive area has a size of 1.5 mm to 3 mm along the width of the positive electrode tab. This reduces the probability of direct contact between the positive electrode tab and the negative electrode tab, and reduces the risk of short circuit between the positive and negative electrodes.

[0017] According to some embodiments of the present application, the thickness of the positive electrode current collector accounts for 5.5%-8% of the thickness of the positive electrode plate. As a result, a thinner positive electrode current collector can reduce the space occupied, improve the space utilization of the active area, and increase the energy density of the battery cell.

[0018] According to some embodiments of the present application, the porosity of the positive electrode sheet is 25%-30%, thereby increasing the content of the positive electrode active material and improving the transmission rate of lithium ions.

[0019] According to some embodiments of the present application, the coating weight of the positive electrode active material layer on one side is 0.26 g / 1540.25 mm 2 -0.33g / 1540.25mm 2 This increases the energy density of the battery cell.

[0020] According to some embodiments of the present application, the coating weight of the positive electrode active material layer on one side is 0.28 g / 1540.25 mm 2 -0.32g / 1540.25mm 2 This increases the energy density of the battery cell.

[0021] According to some embodiments of the present application, the compaction density of the positive electrode active material layer is 2.3 g / cm 3 -2.65g / cm 3 This increases the energy density of the battery cell.

[0022] According to some embodiments of the present application, the compaction density of the positive electrode active material layer is 2.45 g / cm 3 -2.58g / cm 3 This increases the energy density of the battery cell.

[0023] According to some embodiments of the present application, the lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate, thereby improving the cycle performance of the battery cell.

[0024] According to some embodiments of the present application, the lithium-containing phosphate includes lithium iron phosphate, and the average particle size of the lithium iron phosphate primary particles is 300 nm to 800 nm, thereby shortening the lithium ion deintercalation path and increasing the lithium ion deintercalation rate.

[0025] According to some embodiments of the present application, the lithium iron phosphate includes a doping element, wherein the doping element includes one or more of V, Ti, Mg, and Nb. This improves the structural stability of the lithium-containing phosphate, increases the diffusion rate of lithium ions, and improves the cycling performance and charge-discharge performance of the battery cell.

[0026] According to some embodiments of the present application, based on the total mass of the positive electrode active material layer, the mass proportion of the V element is 0.02%-0.2%, the mass proportion of the Ti element is 0.03%-0.2%, the mass proportion of the Mg element is 0.02%-0.1%, and the mass proportion of the Nb element is 0.02%-0.2%. This improves the structural stability of the lithium-containing phosphate, increases the diffusion rate of lithium ions, and improves the cycle performance and charge-discharge performance of the battery cell.

[0027] According to some embodiments of the present application, the negative electrode plate includes a negative electrode current collector, and the thickness of the negative electrode current collector is 2.5%-6% of the thickness of the negative electrode plate. A thinner negative electrode current collector can reduce the space occupied, improve the utilization rate of the active area, and increase the energy density of the battery cell.

[0028] According to some embodiments of the present application, the coating weight of the negative electrode active material layer on one side is 0.12 g / 1540.25 mm 2 -0.15g / 1540.25mm 2 This increases the energy density of the battery cell.

[0029] According to some embodiments of the present application, the coating weight of the negative electrode active material layer on one side is 0.125 g / 1540.25 mm 2 -0.14g / 1540.25mm 2 This increases the energy density of the battery cell.

[0030] According to some embodiments of the present application, the compaction density of the negative electrode active material layer is 1.3 g / cm 3 -1.52g / cm 3 This increases the energy density of the battery cell.

[0031] According to some embodiments of the present application, the porosity of the negative electrode sheet is 25%-30%, thereby increasing the content of the negative electrode active material and improving the transmission rate of lithium ions.

[0032] According to some embodiments of the present application, the carbon material includes graphite, the graphite includes secondary particles, and at least a portion of the surface of the secondary particles has amorphous carbon. This improves the electronic and ion conductivity of the graphite, thereby helping to improve the fast charging performance of the battery cell.

[0033] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite is 7 μm-12 μm. This can shorten the solid phase migration path of lithium ions and improve the fast charging capability of the battery cell.

[0034] According to some embodiments of the present application, the graphite has a degree of graphitization of 90%-94%, thereby improving the ion conductivity and electron conductivity of the graphite and enhancing the rate performance of the battery.

[0035] According to some embodiments of the present application, the battery cell further comprises an electrolyte, wherein the electrolyte comprises at least one of a carbonate solvent and a carboxylate solvent, thereby improving the ionic conductivity of the electrolyte and the fast charging performance of the battery cell.

[0036] According to some embodiments of the present application, the carbonate solvent accounts for 20% to 75% of the total mass of the electrolyte, thereby improving the ionic conductivity of the electrolyte while reducing the viscosity of the electrolyte at low temperatures.

[0037] According to some embodiments of the present application, the carboxylate solvent accounts for 10% to 35% of the total mass of the electrolyte, thereby reducing the risk of electrolyte gassing under high temperature conditions and improving the high-temperature cycle life of the battery cells.

[0038] According to some embodiments of the present application, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Therefore, the above carbonate solvents have a high dielectric constant and can improve the ionic conductivity of the electrolyte.

[0039] According to some embodiments of the present application, the carboxylate solvent comprises R1-COO-R2, where R1 comprises any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and R2 comprises any one of a C1-C5 alkyl group or a C1-C5 haloalkyl group. As a result, these carboxylate solvents have a relatively low molecular weight, which can reduce the viscosity of the electrolyte and improve the ionic conductivity of the electrolyte.

[0040] According to some embodiments of the present application, the carboxylate solvent includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate, thereby reducing the viscosity of the electrolyte and improving the ionic conductivity of the electrolyte.

[0041] According to some embodiments of the present application, the electrolyte further comprises an electrolyte salt comprising a lithium fluorinated sulfonyl imide and lithium hexafluorophosphate, with the electrolyte salt comprising 12% to 18% of the total mass of the electrolyte. This improves the ionic conductivity of the electrolyte while reducing HF generation and SEI film corrosion.

[0042] According to some embodiments of the present application, the mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide is (1.2-3):1.

[0043] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass of the lithium hexafluorophosphate accounts for 4%-14%.

[0044] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the fluorinated lithium sulfonyl imide is 4%-8%.

[0045] By setting the contents of lithium hexafluorophosphate and lithium fluorinated sulfonyl imide within the above ranges, the ionic conductivity of the electrolyte is improved while the generation of HF is reduced, thereby reducing the corrosion of the SEI film.

[0046] According to some embodiments of the present application, the electrolyte further includes additives, including one or more of carbonate additives, sultone additives, lithium salt additives, and phosphate additives. This forms a stable interface film on the electrode surface, reduces interfacial impedance, and improves the fast-charging performance of the battery cell.

[0047] According to some embodiments of the present application, the additive accounts for 0.1% to 5% of the total mass of the electrolyte, thereby forming a stable interface film on the electrode surface, reducing the interface impedance and improving the fast charging performance of the battery cell.

[0048] According to some embodiments of the present application, the electrolyte includes the carbonate additive and the phosphate additive, and the combined mass of the carbonate additive and the phosphate additive is 0.1%-0.5% based on the total mass of the electrolyte. This forms a stable SEI film, preventing side reactions caused by solvent molecules contacting the interface and degrading the battery life.

[0049] According to some embodiments of the present application, the carbonate additive includes vinylene carbonate, and the phosphate additive includes tris(trimethylsilyl)phosphate. Based on the total mass of the electrolyte, the combined mass of the carbonate additive and the phosphate additive accounts for 0.1%-0.5%. This allows for the formation of a SEI film of moderate thickness on the material surface, maintaining interfacial stability while minimizing increases in internal resistance.

[0050] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bis(oxalatoborate), and lithium fluorosulfonate. This forms a stable SEI film on the negative electrode surface, reducing side reactions between the electrolyte and the electrode surface.

[0051] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate, and the weight of the lithium salt additive accounts for 0.02%-0.5% of the total weight of the electrolyte. This improves the SEI impedance and enhances power performance.

[0052] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate, and the weight of the lithium salt additive accounts for 0.1%-0.5% of the total weight of the electrolyte. This improves the impedance of the SEI film and enhances power performance.

[0053] According to some embodiments of the present application, the conductivity of the electrolyte at room temperature is 10mS / cm-14mS / cm, thereby increasing the migration rate of lithium ions and improving the fast charging performance of the battery cell.

[0054] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0055] The third aspect of the present application provides an electrical device, comprising the battery cell provided by the first aspect of the present application or the battery device provided by the second aspect of the present application, wherein the battery cell or the battery device provides electrical energy for the electrical device.

[0056] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0058] Figure 1 It is a schematic structural diagram of an electrode assembly according to one embodiment of the present application.

[0059] Figure 2 It is a schematic structural diagram of an electrode assembly according to another embodiment of the present application.

[0060] Figure 3 It is a schematic structural diagram of an electrode assembly according to another embodiment of the present application.

[0061] Figure 4 It is a schematic structural diagram of a battery cell according to one embodiment of the present application.

[0062] Figure 5 yes Figure 4 Cross-sectional view of the battery cell in the thickness direction.

[0063] Figure 6 yes Figure 5 A partial magnified view of the middle circle area.

[0064] Figure 7 It is a schematic structural diagram of an adapter sheet according to one embodiment of the present application.

[0065] Figure 8 This is a schematic diagram of the positional relationship among the positive electrode active material layer, the negative electrode active material layer, the inorganic coating layer, and the positive electrode tab in one embodiment of the present application.

[0066] Figure 9 It is a schematic diagram of an electrical device according to one embodiment of the present application.

[0067] Description of reference numerals:

[0068] 1 Battery cell; 2 Electrode terminal; 6 Adapter; 61 End face; 62 Surface; X Battery cell height direction; Y Battery cell thickness direction; Z Battery cell width direction; 20 Shell; 21 Inner wall of side wall; 10 Electrode assembly; 111 Positive electrode tab; 1111 Bend; 1112 Welding portion; 112 Negative electrode tab; 13 Positive electrode sheet; 131 Positive electrode straight section; 132 Positive electrode curved section; 14 Negative electrode sheet; 141 Negative electrode straight section; 142 Negative electrode curved section; 15 Separator; 101 Positive electrode active material layer; 201 Negative electrode active material layer; 2010 Edge of negative electrode active material layer; 301 Inorganic coating; 112 Empty foil area; F1 Positive electrode sheet width direction; F2 Positive electrode sheet length direction; 30 First electrode assembly; 40 Second electrode assembly. DETAILED DESCRIPTION

[0069] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0070] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0071] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0072] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0073] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0074] Currently, market developments indicate that batteries are increasingly being used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. As battery applications continue to expand, market demand is also growing.

[0075] The present application proposes a battery cell, which can improve the shunting capacity of the tabs by increasing the number of tabs, reduce the heat generation of the battery cell under fast charging conditions, and improve the cycle performance of the battery cell under fast charging conditions. In order to meet the demand for fast current transmission and the assembly requirements of the battery pack with high energy density, the tabs can be arranged to extend from the pole pieces along the height direction of the battery cell and electrically connected to the electrode terminals on the cover assembly, which makes the tabs bend in the height direction of the battery cell to form a "folded tab" state. Therefore, it is necessary to reserve space between the electrode assembly and the electrode terminal to accommodate the bent folded tabs. When the number of tabs increases, the reserved space needs to be increased, which will result in a decrease in the utilization rate of the shell space by the active material layer and a loss of the energy density of the battery cell. The present application forms a first gap between the end face of the adapter plate close to the side wall of the shell and the inner wall of the side wall of the shell. The first gap is used to accommodate the folded pole ear, which can reduce the reserved space (second gap) between the electrode assembly and the electrode terminal in the height direction of the battery cell. By limiting the sizes of the first gap and the second gap within a suitable range, on the one hand, the space occupied by the folded pole ear in the height direction of the battery cell can be reduced, and the energy density of the battery cell can be improved; on the other hand, the probability of the folded pole ear being inserted into the pole piece can be reduced, the occurrence of short circuit can be reduced, and the interlayer spacing between the pole pieces due to the insertion of the pole ear can be prevented from increasing, thereby reducing the impact on the cycle performance of the battery cell.

[0076] The battery cells proposed in this application can be used in electrical devices that use the battery cells as power sources or various energy storage systems that use the battery cells as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0077] In a first aspect, the present application provides a battery cell, the battery cell comprising a housing assembly and an electrode assembly, the electrode assembly being housed in the housing assembly, the housing assembly comprising a shell and a cover assembly, the cover assembly covering the shell, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, the cover assembly comprising a cover plate and an electrode terminal; wherein:

[0078] The positive electrode sheet includes a positive electrode coating portion and a positive electrode tab, wherein the positive electrode coating portion is coated with a positive electrode active material layer, wherein the positive electrode active material layer includes a lithium-containing phosphate; the negative electrode sheet includes a negative electrode coating portion and a negative electrode tab, wherein the negative electrode coating portion is coated with a negative electrode active material layer, wherein the negative electrode active material layer includes graphite; and the positive electrode tab and the negative electrode tab are both electrically connected to the electrode terminal via an adapter sheet;

[0079] The positive electrode coating portion includes a positive electrode straight segment, and the negative electrode coating portion includes a negative electrode straight segment. The positive electrode straight segments and the negative electrode straight segments are stacked along the thickness direction of the electrode assembly. The number of the positive electrode tabs is n1, and the number of the positive electrode straight segments is n2. The ratio of n1 to n2 is 3 / 4-1, and the range of n1 is 110-220, and the unit is: piece;

[0080] refer to Figure 5 and Figure 6 The adapter sheet 6 is a sheet-shaped conductive member, and the positive electrode tab 111 includes a bending portion 1111 and a welding portion 1112. Along the thickness direction Y of the battery cell, the adapter sheet 6 includes an end face 61 close to the side wall of the shell 20, and a first gap is formed between the end face 61 and the inner wall 21 of the side wall for accommodating the positive electrode tab 111, wherein the size of the first gap is 2.5mm-8mm; along the height direction X of the battery cell, the adapter sheet 6 has a surface 62 facing the electrode assembly, and a second gap is formed between the surface 62 and the edge 2010 of the negative electrode active material layer for accommodating the positive electrode tab 111, wherein the size of the second gap is 4.5mm-7.5mm.

[0081] As an example, the first gap d1 may be 2.5 mm, 3.5 mm, 4.5 mm, 5.5 mm, 6.5 mm, 7.5 mm, 8 mm, etc., or may be within a range consisting of any of the above values.

[0082] As an example, the second gap d2 may be 4.5 mm, 5.5 mm, 6.5 mm, 7.5 mm, etc., or may be within a range consisting of any of the above values.

[0083] In the present application, the battery cell is cut to obtain a cross section of the battery cell along its thickness direction, and the cross section is tested by computed tomography (CT) to measure the sizes of d1 and d2.

[0084] refer to Figure 1When the electrode assembly 10 is a wound electrode assembly, the positive electrode sheet 13, the negative electrode sheet 14, and the separator 15 are each a whole piece structure, and the separator 15 is arranged between the positive electrode sheet 13 and the negative electrode sheet 14. The positive electrode sheet 13, the separator 15, and the negative electrode sheet 15 are wound in one direction to form an electrode assembly.

[0085] After winding to form the electrode assembly 10, the positive electrode sheet 13 includes a positive electrode coating portion, which includes a plurality of positive electrode straight sections 131 and a plurality of positive electrode curved sections 132. The positive electrode straight sections 131 and the positive electrode curved sections 132 are arranged along the winding direction of the electrode assembly 10, and the positive electrode straight sections 131 and the positive electrode curved sections 132 are connected, and the positive electrode tab 111 is connected to the positive electrode straight sections 131.

[0086] The negative electrode sheet 14 includes a negative electrode coating portion, which includes multiple negative electrode straight sections 141 and multiple negative electrode curved sections 142. The negative electrode straight sections 141 and the negative electrode curved sections 142 are arranged along the winding direction of the electrode assembly, and the negative electrode straight sections 141 and the negative electrode curved sections 142 are connected, and the negative electrode tab 112 is connected to the negative electrode straight sections 141.

[0087] The positive electrode straight sections 131 and the negative electrode straight sections 141 are alternately stacked, and the positive electrode curved sections 132 and the negative electrode curved sections 142 are alternately stacked.

[0088] From the perspective of the electrode assembly's appearance, the electrode assembly includes a straight region, a bent region, and an electrode tab. The straight region includes a positive straight segment 131 and a negative straight segment 141 , and the bent region includes a positive bent segment 132 and a negative bent segment 142 .

[0089] When the electrode assembly is a wound electrode assembly, the ratio of n1 to n2 is 3 / 4-1, for example, it can be 3 / 4, 0.85, 0.9, 1, etc., or can be a range consisting of any of the above values.

[0090] refer to Figure 1 , the ratio of n1 to n2 is 1, and the positive electrode sheet 13 can be wound one circle to form two positive straight sections 131 , and each positive straight section 131 is connected to a positive electrode tab 111 .

[0091] refer to Figure 2 , the ratio of n1 to n2 is 3 / 4, the positive electrode sheet 13 is wound multiple times, each turn can form two positive straight sections, and only one of the two positive straight sections 131 of at least one turn in the multiple turns is provided with a positive electrode ear 111, and the two positive straight sections 131 formed by the other turns are both provided with a positive electrode ear 111. The ratio of the number of positive electrode ears 111 to the number of positive straight sections 131 in the electrode assembly 10 is 3 / 4.

[0092] For wound electrode assemblies, when the ratio of n1 to n2 is greater than 3 / 4 and less than 1, the positive electrode tabs can be preferentially arranged on the inner ring's straight positive electrode segments. For example, when the number of straight positive electrode segments is 152 and the number of positive electrode tabs is 114, after the wound electrode assembly is formed, each of the 76 straight positive electrode segments on the inner ring is provided with a positive electrode tab, and each of the 76 straight positive electrode segments on the outer ring is provided with a positive electrode tab. The positive electrode tabs on the outer ring need to be bent and welded to the adapter. The positive electrode tabs on the outer ring must be longer than those on the inner ring to ensure welding to the adapter after folding. By reducing the number of positive electrode tabs on the outer ring, the risk of the outer ring tabs being inserted between the electrode layers due to excessive length and easy folding is reduced while meeting the tab overcurrent capacity, thereby improving the cycling performance of the battery cell.

[0093] When the electrode assembly is a laminated electrode assembly, the electrode assembly includes multiple positive electrode sheets and multiple negative electrode sheets. The positive electrode sheets have positive straight sections, and the negative electrode sheets have negative straight sections. The positive straight sections and the negative straight sections are stacked along the thickness direction of the electrode assembly.

[0094] When the electrode assembly is a laminated electrode assembly, the electrode assembly includes a straight area in terms of appearance. Optionally, the electrode assembly may also include a bent area. For example, when the isolation membrane adopts a whole-piece structure, the isolation membrane is bent multiple times and then stacked with the positive electrode sheet and the negative electrode sheet to form an electrode assembly; or when the negative electrode sheet adopts a whole-piece structure, the negative electrode sheet is bent multiple times and then stacked with the positive electrode sheet and the isolation membrane to form an electrode assembly.

[0095] The following description takes the example that the electrode assembly only includes the straight area.

[0096] refer to Figure 3 Structurally, the electrode assembly 10 includes a positive electrode sheet 13, a negative electrode sheet 14 and a separator 15. The separator 15 is arranged between the positive electrode sheet 13 and the negative electrode sheet 14. The positive electrode sheet 13, the separator 15 and the negative electrode sheet 14 are stacked.

[0097] refer to Figure 3 , the ratio of n1 to n2 is 1, the positive electrode ear and the positive electrode sheet are set in one-to-one correspondence, and a positive electrode ear is set on each positive straight section.

[0098] As an example, whether it is a wound electrode assembly or a laminated electrode assembly, n1 can be 110, 130, 150, 170, 190, 200, 220, etc., or can be a range consisting of any of the above values.

[0099] In this application, the number of electrode assemblies within a battery cell can be 1, 2, or 4, etc., and n1 refers to the total number of positive electrode tabs contained in all electrode assemblies within the battery cell. For example, when there is 1 electrode assembly, n1 refers to the total number of positive electrode tabs contained in one electrode assembly; when there are 2 electrode assemblies, n1 refers to the total number of positive electrode tabs contained in both electrode assemblies; and when there are 4 electrode assemblies, n1 refers to the total number of positive electrode tabs contained in all four electrode assemblies.

[0100] refer to Figure 4 The height direction X, width direction Z and thickness direction Y of the battery cell 1 are shown in the figure.

[0101] refer to Figure 5 In order to improve the energy density of the battery cell, the battery cell 1 includes a first electrode assembly 30 and a second electrode assembly 40. The two electrode assemblies are arranged side by side in the thickness direction Y of the battery cell. The two electrode assemblies are electrically connected to the electrode terminal 2 through the adapter 6. Taking the positive electrode tab as an example, the positive electrode tab 111 is electrically connected to the electrode terminal 2 through the adapter 6.

[0102] The battery cell proposed in this application can increase the area of ​​active material and the energy density of the battery cell by controlling the size of the first gap and the second gap within an appropriate range. At the same time, it can reduce the probability of an increase in the interlayer spacing between the pole pieces due to the insertion of the folded pole ear into the active material layer, thereby improving the cycle performance of the battery cell under fast charging conditions.

[0103] According to some embodiments of the present application, along the height direction of the battery cell, the positive electrode tab extends from the positive electrode straight section, and the negative electrode tab extends from the negative electrode straight section.

[0104] Specifically, for a wound electrode assembly and a laminated electrode assembly, the direction in which the positive electrode tab extends from the positive electrode straight section is the height direction of the battery cell. For example, for a laminated electrode assembly, the height direction X of the battery cell is as follows: Figure 4 As shown. That is, the height direction X of the battery cell corresponds to the width direction of the positive electrode sheet, and the width direction Z of the battery cell corresponds to the length direction of the positive electrode sheet. The positive electrode tab extends from the positive straight section along the width direction of the positive electrode sheet, and the negative electrode tab extends from the negative straight section along the width direction of the negative electrode sheet. Compared with the positive electrode tab extending from the positive straight section along the length direction of the positive electrode sheet and the negative electrode tab extending from the negative straight section along the length direction of the negative electrode sheet, this can increase the area ratio of the active area on the positive and negative electrode sheets, thereby improving the energy density of the battery cell.

[0105] According to some embodiments of the present application, the size of the adapter sheet along the height direction of the battery cell may be 0.6mm-2mm. Figure 5 and Figure 6 , along the height direction X of the battery cell, the size of the adapter sheet is the thickness of the adapter sheet. By making the thickness of the adapter sheet within the above range, on the one hand, the space occupied by the adapter sheet in the height direction of the battery cell can be reduced, thereby improving the energy density of the battery cell; on the other hand, the current capacity of the adapter sheet can be improved, thereby reducing the heat generation of the battery cell under fast charging conditions and improving the cycle life of the battery cell under fast charging conditions.

[0106] In the present application, the battery cell is cut along the thickness direction to obtain a cross section, and the size of the adapter in the height direction of the battery cell is measured by CT.

[0107] As an example, along the height direction of the battery cell, the size of the adapter plate may be 0.6 mm, 0.8 mm, 1 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2 mm, etc., or may be a range consisting of any of the above values.

[0108] According to some embodiments of the present application, along the thickness direction of the battery cell, reference Figure 7 The adapter plate 6 has a dimension c, which satisfies a range of 15 mm to 60 mm. Specifically, the dimension of the adapter plate in the thickness direction of the battery cell is the width of the adapter plate. By ensuring that the width of the adapter plate is within the above range, a larger welding area can be provided when welding the adapter plate to the tab, thereby increasing the area of ​​the welding area and improving the strength of the weld.

[0109] As an example, the size of the adapter in the thickness direction of the battery cell can be 15 mm, 25 mm, 35 mm, 45 mm, 55 mm, 60 mm, etc., or can be a range consisting of any of the above values.

[0110] According to some embodiments of the present application, reference Figure 6 The welding portion 1112 of the positive electrode tab 111 and the adapter 6 are welded to form a welding area, and the area of ​​the welding area is 10mm 2 -40mm 2 . Thus, the firmness of welding is improved.

[0111] In this application, the side length of the welding area can be measured by a soft ruler with an accuracy of 0.1 mm, and calculated by a mathematical formula based on the graphics of the welding area.

[0112] According to some embodiments of the present application, reference Figure 4Along the width direction Z of the battery cell, the size of the battery cell is 120mm-350mm, along the height direction X of the battery cell, the size of the battery cell is 80mm-120mm, and along the thickness direction Y of the battery cell, the size of the battery cell is 25mm-80mm.

[0113] As an example, along the width direction of the battery cell, the size of the battery cell may be 120 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, etc., or may be a range consisting of any of the above values.

[0114] As an example, along the height direction of the battery cell, the size of the battery cell may be 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, etc., or may be within a range consisting of any of the above values.

[0115] As an example, along the thickness direction of the battery cell, the size of the battery cell can be 25mm, 45mm, 65mm, 75mm, 80mm, etc., or can be a range consisting of any of the above values.

[0116] According to some embodiments of the present application, along the width direction of the positive electrode sheet, the positive electrode tab includes a hollow foil area and an inorganic coating area, and the inorganic coating area is located between the positive electrode coating portion and the hollow foil area, wherein:

[0117] The empty foil area is used to electrically connect to the electrode terminal, the inorganic coating area includes an inorganic coating, and the inorganic coating includes the inorganic particles and the adhesive. Along the width direction of the positive electrode sheet, the size of the inorganic coating accounts for 1 / 15-1 / 4 of the size of the positive electrode tab.

[0118] The positive electrode coating portion of the positive electrode current collector includes an active area and an inactive area, the positive electrode active material layer is located in the active area, the inactive area is located between the inorganic coating area and the active area, and is connected to the inorganic coating area and the active area, wherein the size of the inactive area along the width direction of the positive electrode sheet is 1.5 mm-3 mm.

[0119] The inactive area includes an inorganic coating layer, and the inorganic coating layer includes inorganic particles and a binder.

[0120] refer to Figure 8 The width direction F1 of the positive electrode sheet and the length direction F2 of the positive electrode sheet are shown in the figure. Figure 8The relationship between the sizes of the positive electrode active material layer 101, the inorganic coating 301, the positive electrode tab 111 on the positive electrode collector, and the negative electrode active material layer 201 on the negative electrode collector is shown. The positive electrode tab 111 includes a hollow foil area 112 and an inorganic coating area. The inorganic coating area includes an inorganic coating 301. The width of the inorganic coating 301 in the inactive area of ​​the positive electrode coating portion in the width direction F1 of the positive electrode sheet is d, and 1.5mm≤d≤3mm.

[0121] When the positive electrode tab is connected to the electrode terminal, it will bend in the height direction of the battery cell to form a "folded tab" state, that is, the empty foil area of ​​the tab will be bent in the height direction of the battery cell, thereby improving the utilization rate of the positive and negative electrode sheets in the shell height and improving the energy density of the battery cell. However, this method of compressing the tab bending in height can easily cause the root of the positive electrode tab or the bent part of the positive electrode tab to be inserted into the negative electrode active material area, resulting in a short circuit in the battery, such as Figure 6 As shown in the circled area, the bent positive electrode tab 111 is easily inserted into the negative electrode active material area, resulting in an increase in the distance between the electrode layers, which causes a safety risk. The present application provides an inorganic coating 301 between the positive electrode active layer 101 and the positive electrode tab 111, and controls the width d of the inorganic coating 301. This can reduce the probability of the positive electrode tab directly contacting the negative electrode when bent, thereby reducing the risk of short circuit between the positive and negative electrodes.

[0122] refer to Figure 8 The dimension of the inorganic coating 301 on the positive electrode tab 111 in the width direction F1 of the positive electrode sheet is a, and the dimension of the positive electrode tab 111 in the width direction F1 of the positive electrode sheet is b. A / b can be 1 / 15-1 / 4. By making a / b within the above range, while reducing the direct contact between the positive electrode tab and the negative electrode sheet, sufficient size can be reserved for the empty foil area to be welded with the adapter sheet, thereby improving the firmness of the welding.

[0123] As an example, d may be 1.5 mm, 2 mm, 2.5 mm, 3 mm, etc., or may be a range consisting of any of the above values.

[0124] As an example, a / b may be 1 / 15, 1 / 12, 1 / 10, 1 / 8, 1 / 6, 1 / 4, etc., or may be a range consisting of any of the above values.

[0125] According to some embodiments of the present application, along the width direction F1 of the positive electrode sheet, the dimension a of the inorganic coating 301 of the positive electrode tab 111 is 2 mm-7.5 mm, and the dimension b of the positive electrode tab 111 is 25 mm-45 mm.

[0126] As an example, a can be 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7.5 mm, etc., or can be a range consisting of any of the above values.

[0127] As an example, b can be 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, etc., or can be a range consisting of any of the above values.

[0128] According to some embodiments of the present application, along the width direction of the positive electrode sheet, the size of the negative electrode active material layer is larger than the size of the active area, and the size of the negative electrode active material layer is smaller than the sum of the size of the active area and the size of the inactive area. Figure 8 Along the width direction F1 of the positive electrode sheet, the size of the negative electrode active material layer 201 is larger than that of the positive electrode active material layer 101, and the size of the negative electrode active material layer 201 is smaller than the sum of the size of the positive electrode active material layer 101 and the size of the inorganic coating 301 in the inactive area. This allows the trimmed edge of the negative electrode sheet to fall onto the inorganic coating, preventing burrs from the trimmed edge of the sheet from piercing the separator and forming an electrical connection with the positive electrode sheet.

[0129] According to some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector, and the thickness of the positive electrode current collector is 5.5%-8% of the thickness of the positive electrode sheet. By reducing the space occupied by the positive electrode current collector, the space utilization rate of the active area is improved, and the energy density of the battery cell is increased.

[0130] The thickness of the positive electrode current collector refers to the dimension of the positive electrode current collector in the thickness direction of the battery cell. As an example, the thickness of the positive electrode current collector accounts for 5.5%, 6.5%, 7.5%, 8%, etc. of the thickness of the positive electrode sheet, or can be any range of the above values.

[0131] According to some embodiments of the present application, the porosity of the positive electrode sheet is 25%-30%. Therefore, by ensuring that the porosity of the positive electrode sheet is within the above range, on the one hand, the mass ratio of the positive electrode active material layer can be increased; on the other hand, the transmission rate of lithium ions can be increased, thereby improving the fast charging performance of the battery cell.

[0132] In this application, the porosity test method of the positive electrode sheet is as follows: place the sample cup containing the sample in a true density tester, close the test system, introduce helium according to the procedure, detect the pressure of the gas in the sample chamber and the expansion chamber, and then calculate the true volume according to Bohr's law (PV=nRT) to obtain the porosity of the sample to be tested.

[0133] According to some embodiments of the present application, the single-sided coating weight of the positive electrode active material layer is 0.26 g / 1540.25 mm 2 -0.33g / 1540.25mm2 .

[0134] This application provides a method for testing the coating weight of the positive electrode active material layer: A battery cell is disassembled to remove the positive electrode sheet. For example, a single-sided coated positive electrode sheet (if a double-sided coated sheet is used, the positive electrode active material layer on one side can be wiped off first) is punched into small discs with an area of ​​S1. These discs are weighed and recorded as M1. The positive electrode active material layer of the weighed positive electrode sheet is then wiped off, and the weight of the positive electrode current collector is weighed and recorded as M0. The single-sided coating weight of the positive electrode active material layer = (M1 - M0) / S1.

[0135] As an example, the coating weight of the positive electrode active material layer on one side may be 0.26 g / 1540.25 mm 2 、0.28g / 1540.25mm 2 、0.3g / 1540.25mm 2 、0.31g / 1540.25mm 2 、0.33g / 1540.25mm 2 etc., or can be within the range of any of the above numerical values.

[0136] According to some embodiments of the present application, the single-sided coating weight of the positive electrode active material layer is 0.28 g / 1540.25 mm 2 -0.32g / 1540.25mm 2 .

[0137] According to some embodiments of the present application, the compaction density of the positive electrode active material layer is 2.3 g / cm 3 -2.65g / cm 3 .

[0138] The present application provides a method for testing the compaction density of the positive electrode active material layer: place the battery cell at 25°C, let it stand for 2 hours, charge it to 3.65V at a constant current of 1 / 3C, charge it to 0.05C at a constant voltage of 3.65V, let it stand for 2 hours, and then discharge it to 2.0V at a rate of 0.33C. The battery cell is disassembled to remove the positive electrode sheet, for example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode active material layer on one side can be wiped off first), punched into small discs with an area of ​​S1, weighed, recorded as M1, and its thickness H1 is measured. Then wipe off the positive electrode active material layer of the weighed positive electrode sheet, weigh the weight of the positive electrode collector, record it as M0, and measure its thickness H0. The single-side coating weight of the positive electrode active material layer = (M1-M0) / S1, the thickness of the positive electrode active material layer = H1-H0, and the compaction density of the positive electrode active material layer = the single-side coating weight of the positive electrode active material layer / the thickness of the positive electrode active material layer.

[0139] As an example, the compaction density of the positive electrode active material layer can be 2.3 g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 , 2.6g / cm 3 , 2.65g / cm 3 etc., or can be within the range of any of the above numerical values.

[0140] According to some embodiments of the present application, the compaction density of the positive electrode active material layer is 2.45 g / cm 3 -2.58g / cm 3 .

[0141] According to some embodiments of the present application, the lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

[0142] According to some embodiments of the present application, the lithium-containing phosphate includes lithium iron phosphate, and the average particle size of the lithium iron phosphate primary particles is 300nm-800nm. As a result, the average particle size of the primary particles is relatively small, and the lithium ion deintercalation path in the positive electrode active material is shortened, which can increase the lithium ion deintercalation rate and improve the fast charging performance of the battery cell.

[0143] The average particle size of the primary particles can refer to the test methods known in the art. Specifically for the present application, the following test method can be referred to: use plasma to cut the positive electrode sheet along its thickness direction to obtain a cross-section of the positive electrode sheet, observe it under an appropriate magnification using a scanning electron microscope (SEM), and randomly select at least 50 primary particles. The average particle size of a single primary particle = (the longest diameter of a single particle + the shortest diameter of a single particle) / 2. The average value of the selected primary particles is the average particle size of the primary particles.

[0144] As an example, the average particle size of the lithium iron phosphate primary particles can be 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, etc., or can be within a range consisting of any of the above values.

[0145] According to some embodiments of the present application, the lithium iron phosphate includes a doping element, wherein the doping element includes one or more of V, Ti, Mg, and Nb. By doping the lithium iron phosphate with these elements, iron dissolution can be reduced, the rate of lithium ion insertion and extraction can be increased, the power performance of the battery can be improved, and the compaction density of the positive electrode active material layer can be improved.

[0146] According to some embodiments of the present application, based on the total mass of the positive electrode active material layer, the mass proportion of the V element is 0.02%-0.2%, the mass proportion of the Ti element is 0.03%-0.2%, the mass proportion of the Mg element is 0.02%-0.1%, and the mass proportion of the Nb element is 0.02%-0.2%.

[0147] As an example, the mass proportion of the V element is 0.02%, 0.05%, 0.1%, 0.15%, 0.2%, etc., or can be a range consisting of any of the above values.

[0148] As an example, the mass proportion of the Ti element is 0.03%, 0.05%, 0.1%, 0.15%, 0.2%, etc., or can be a range consisting of any of the above values.

[0149] As an example, the mass proportion of the Mg element is 0.02%, 0.05%, 0.1%, etc., or can be a range consisting of any of the above values.

[0150] As an example, the mass proportion of the Nb element is 0.02%, 0.05%, 0.1%, 0.15%, 0.2%, etc., or can be a range consisting of any of the above values.

[0151] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0152] In some embodiments, the positive electrode active material layer may further optionally include a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0153] In some embodiments, the positive electrode active material layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0154] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0155] According to some embodiments of the present application, the negative electrode plate includes a negative electrode current collector, and the thickness of the negative electrode current collector is 2.5%-6% of the thickness of the negative electrode plate. By reducing the space occupied by the negative electrode current collector, the utilization rate of the active material in the internal space of the housing can be improved, thereby increasing the energy density of the battery cell.

[0156] As an example, the thickness of the negative electrode current collector is 2.5%, 3.5%, 4.5%, 5.5%, 6% of the thickness of the negative electrode sheet, or can be a range consisting of any of the above values.

[0157] According to some embodiments of the present application, the coating weight of the negative electrode active material layer on one side is 0.12 g / 1540.25 mm 2 -0.15g / 1540.25mm 2 .

[0158] This application provides a method for testing the coating weight of the negative electrode active material layer: Disassemble the battery cell to remove the negative electrode sheet. For example, take a negative electrode sheet coated on one side (if it is coated on both sides, wipe off the negative electrode active material layer on one side first). Punch it into small discs with an area of ​​S2, weigh them, and record them as M3. Then wipe off the negative electrode active material layer of the weighed negative electrode sheet, weigh the negative electrode current collector, and record them as M2. The single-sided coating weight of the negative electrode active material layer = (M3 - M2) / S2.

[0159] As an example, the coating weight of the negative electrode active material layer on one side may be 0.12 g / 1540.25 mm 2 、0.13g / 1540.25mm 2 、0.14g / 1540.25mm 2 、0.15g / 1540.25mm 2 etc., or can be within the range of any of the above numerical values.

[0160] According to some specific embodiments of the present application, the coating weight of the negative electrode active material layer on one side can be 0.125g / 1540.25mm 2 -0.14g / 1540.25mm 2 .

[0161] According to some embodiments of the present application, the compaction density of the negative electrode active material layer is 1.3 g / cm 3 -1.52g / cm 3 This increases the energy density of the battery cell.

[0162] The present application provides a method for testing the compaction density of the negative electrode active material layer: charge to 3.65V at a constant current of 1 / 3C, charge to 0.05C at a constant voltage of 3.65V, place the battery cell at 25°C, let it stand for 2h, and then discharge it to 2.0V at a rate of 0.33C. The battery cell is disassembled to remove the negative electrode pole piece, for example, a single-sided coated negative electrode pole piece (if it is a double-sided coated pole piece, the negative electrode active material layer on one side can be wiped off first), punched into small discs with an area of ​​S2, weighed, recorded as M3, and its thickness H3 is measured. Then wipe off the negative electrode active material layer of the weighed negative electrode pole piece, weigh the weight of the negative electrode current collector, record it as M2, and measure its thickness H2. The single-side coating weight of the negative electrode active material layer = (M3-M2) / S2, the thickness of the negative electrode active material layer = H3-H2, and the compaction density of the negative electrode active material layer = the single-side coating weight of the negative electrode active material layer / the thickness of the negative electrode active material layer.

[0163] As an example, the compaction density of the negative electrode active material layer may be 1.3 g / cm 3 , 1.35g / cm 3 , 1.4g / cm 3 , 1.45g / cm 3 , 1.52g / cm 3 etc., or can be within the range of any of the above numerical values.

[0164] According to some embodiments of the present application, the porosity of the negative electrode sheet is 25%-30%, thereby increasing the content of the negative electrode active material, increasing the energy density of the battery cell, and improving the transmission rate of lithium ions.

[0165] In this application, the porosity of the negative electrode sheet can be tested by referring to the following method: place the sample cup containing the sample in a true density tester, close the test system, introduce helium according to the procedure, detect the pressure of the gas in the sample chamber and the expansion chamber, and then calculate the true volume according to Bohr's law (PV=nRT) to obtain the porosity of the negative electrode sheet.

[0166] As an example, the porosity of the negative electrode sheet may be 25%, 26%, 27%, 28%, 29%, 30%, etc., or may be within a range consisting of any of the above values.

[0167] According to some embodiments of the present application, the carbon material includes graphite, the graphite includes secondary particles, and at least a portion of the surface of the secondary particles has amorphous carbon.

[0168] In the present application, secondary particles refer to particles formed by the aggregation of two or more primary particles.

[0169] In this article, amorphous carbon refers to a transitional carbon material with a very low degree of graphitization and crystallization, nearly amorphous (or lacking a fixed shape and periodic structural regularity). In this application, amorphous carbon refers to the product of carbonization of an organic carbon source, which has a large number of end faces and defects and a high number of lithium ion sites.

[0170] Secondary particles can increase the migration rate of lithium ions, improve the transmission performance of lithium ions, facilitate the embedding and extraction of lithium ions, and help improve the ion conductivity of the material. Amorphous carbon can also improve the conductivity of graphite secondary particles. The secondary particles in the inner core and the coating layer of amorphous carbon jointly improve the electronic and ion conductivity of the material, which helps to improve the fast charging performance of the battery cell.

[0171] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite is 7 μm-12 μm.

[0172] Therefore, the volume average particle size of graphite is smaller, which can shorten the solid phase migration path of lithium ions and improve the fast charging capability of the battery cell. At the same time, by making the volume average particle size within the above range, the side reaction between the graphite negative electrode and the electrolyte can also be reduced.

[0173] In this application, Dv50 refers to the particle size at which the cumulative volume distribution percentage reaches 50%. For example, it can be measured using a laser particle size analyzer (Malvern Master Size 2000) with reference to the standard GB / T 19077-2016 / ISO 13320:2009. The specific testing process is as follows: the battery cell is discharged to 0% SOC, then the negative electrode is disassembled and removed. A certain amount of powder on the electrode is scraped with a blade. This is then washed with deionized water and repeatedly shaken for 5-10 times. After drying, it is sintered in a tube furnace at 400°C for 2 hours. After sintering, an appropriate amount of the sample to be tested (the sample concentration should be 8%-12% obscuration) is taken, deionized water is added, and ultrasonic dispersion is performed to ensure complete dispersion of the sample. The sample is then measured in accordance with the GB / T19077-2016 / ISO 13320:2009 standard.

[0174] According to some embodiments of the present application, the graphite has a degree of graphitization of 90%-94%, thereby improving the ion conductivity and electron conductivity of the graphite and enhancing the rate performance of the battery.

[0175] In this application, the graphitization degree of graphite can be tested by referring to the following method: disassemble the battery cell to obtain the negative electrode sheet, scrape off the powder on the negative electrode sheet, and test it according to the following steps: Pretreatment: weigh according to the ratio of carbon: silicon = 5:1, and then grind it in a clean mortar for 50 minutes to ensure uniform mixing; 2. Sample preparation: The powder obtained above is placed in a sample trough with a depth of 0.5mm and a diameter of 25mm, and the sample is prepared according to the flat sample preparation method; 3. Test: On the X-ray diffractometer, within the range of a starting angle of 52° and an ending angle of 58°, a step length of 0.00836° and a step length of 0.3s are used for scanning tests; 4. Calculate the degree of graphitization based on the test 002 crystal plane interlayer spacing (d002)

[0176] In order to improve the fast charging performance of battery cells, this application also optimizes the electrolyte.

[0177] According to some embodiments of the present application, the battery cell further comprises an electrolyte, wherein the electrolyte comprises at least one of a carbonate solvent and a carboxylate solvent, thereby increasing the conductivity of the electrolyte and improving the fast charging performance of the battery cell.

[0178] In this application, the organic components of the electrolyte can refer to GB / T9722-2023 "General Rules for Gas Chromatography of Chemical Reagents", and the solvent of the electrolyte is qualitatively and quantitatively analyzed by gas chromatography.

[0179] According to some embodiments of the present application, the carbonate solvent may comprise 20% to 75% of the total mass of the electrolyte. Thus, the carbonate solvent has a higher dielectric constant, which can improve the ionic conductivity of the electrolyte and reduce the viscosity of the electrolyte at low temperatures.

[0180] As an example, based on the total mass of the electrolyte, the mass proportion of the carbonate solvent can be 20%, 24%, 35%, 55%, 60%, 65%, 75%, etc., or can be a range consisting of any of the above values.

[0181] According to some embodiments of the present application, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0182] According to some specific embodiments of the present application, the mass proportion of the carboxylate solvent is 10%-35% based on the total mass of the electrolyte. By setting the content of the carboxylate solvent within the above range, on the one hand, the viscosity of the electrolyte can be reduced, the internal resistance of the battery cell can be reduced, the migration rate of lithium ions can be increased, and the fast charging performance of the battery cell can be improved; on the other hand, the risk of gassing of the electrolyte under high temperature conditions can be reduced, and the high-temperature cycle life of the battery cell can be increased, thereby obtaining a battery cell with both excellent fast charging performance and high-temperature cycle life.

[0183] As an example, based on the total mass of the electrolyte, the mass proportion of the carboxylate solvent can be 10%, 20%, 30%, 35%, etc., or can be a range consisting of any of the above values.

[0184] According to some embodiments of the present application, the carboxylate solvent comprises R1-COO-R2, where R1 comprises any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, or a C1-C5 haloalkyl group, and R2 comprises any one of a C1-C5 alkyl group or a C1-C5 haloalkyl group. These carboxylate solvents have a relatively low molecular weight and can improve the ionic conductivity of the electrolyte, thereby enhancing the fast-charging performance of the battery cells.

[0185] According to some embodiments of the present application, the carboxylate solvent includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

[0186] According to some embodiments of the present application, the electrolyte further comprises an electrolyte salt comprising a fluorinated lithium sulfonyl imide and lithium hexafluorophosphate, with the mass of the electrolyte salt accounting for 12%-18% of the total mass of the electrolyte. By simultaneously adding lithium hexafluorophosphate and a fluorinated lithium sulfonyl imide to the electrolyte and controlling the content of the electrolyte salt, the ionic conductivity of the electrolyte can be improved while reducing the generation of HF during battery cycling and storage, reducing the electrolyte solvent and the solvent consumption rate, and thereby extending the life of the battery cells.

[0187] In this application, the test of the content of lithium fluorinated sulfonyl imide and lithium hexafluorophosphate can refer to the standard JY / T020-2002 "General Rules for Ion Chromatography Analysis Methods". For example, a freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery can be taken as a sample, or a battery cell that has been fully discharged (discharged to the discharge cut-off voltage so that the battery cell has a charge state of approximately 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell is used as a sample for testing using the ion chromatography method. The inorganic ion chromatogram is tested, and the corresponding inorganic species are compared based on the chromatographic peak position. The corresponding inorganic ion content percentage is calculated based on the peak area, and then the mass proportion of the fluorinated sulfonyl imide and the mass proportion of the lithium hexafluorophosphate are calculated.

[0188] According to some embodiments of the present application, the mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide is (1.2-3):1. By ensuring that the mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide is within this range, on the one hand, HF generation is reduced, corrosion of the SEI film is reduced, electrolyte consumption is reduced, and the cycle performance of the battery cell is improved; on the other hand, the viscosity of the electrolyte is reduced, the lithium ion transmission rate is increased, and the fast charging performance of the battery cell is improved.

[0189] As an example, the mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide can be 1.2:1, 1.5:1, 2:1, 2.5:1, 3:1, etc., or can be within a range consisting of any of the above values.

[0190] According to some embodiments of the present application, the mass percentage of the lithium hexafluorophosphate may be 4%-14% based on the total mass of the electrolyte, for example, 4%, 6%, 8%, 10%, 12%, 14%, or any range thereof.

[0191] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the fluorinated sulfonyl imide lithium can be 4%-8%, for example, it can be 4%, 5%, 6%, 7%, 8%, etc., or it can be a range consisting of any of the above values.

[0192] According to some embodiments of the present application, the fluorine-containing lithium sulfonyl imide includes one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium perfluorobutylsulfonyl imide, thereby reducing the generation of HF and the corrosion of the SEI film.

[0193] As an example, according to some embodiments of the present application, the electrolyte further includes additives, and the additives include one or more of carbonate additives, sultone additives, lithium salt additives, and phosphate additives.

[0194] In this application, carbonate and sultone additives can form a stable interfacial film on the electrode surface, reducing side reactions between the electrolyte and the electrode surface and improving the cycle life of the battery cell. Lithium salt additives can improve the impedance of the SEI film and enhance the power performance of the battery cell. Phosphate additives can increase the solubility and ionic conductivity of the electrolyte and enhance the diffusion rate of lithium ions.

[0195] According to some embodiments of the present application, the additive accounts for 0.1% to 5% of the total mass of the electrolyte, thereby forming a stable interface film while reducing interface impedance.

[0196] As an example, based on the total mass of the electrolyte, the mass proportion of the additive can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, etc., or can be a range consisting of any of the above values.

[0197] According to some embodiments of the present application, the electrolyte includes the carbonate additive and the phosphate additive, and the combined mass percentage of the carbonate additive and the phosphate additive is 0.1%-0.5% based on the total mass of the electrolyte. This allows for the formation of a stable interface film on the electrode surface, reducing side reactions between the electrolyte and the electrode surface and improving the cycle life of the battery cell.

[0198] As an example, the sum of the mass proportions of the carbonate additive and the phosphate additive may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc., or may be within a range consisting of any of the above values.

[0199] According to some embodiments of the present application, the carbonate additive includes vinylene carbonate, and the phosphate additive includes tris(trimethylsilyl)phosphate. Based on the total mass of the electrolyte, the mass ratio of the carbonate additive to the phosphate additive is 0.1%-0.5%. This allows for the formation of a stable interface film on the electrode surface, reducing side reactions between the electrolyte and the electrode surface and improving the cycle life of the battery cell.

[0200] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bis(oxalatoborate), and lithium fluorosulfonate, based on the total mass of the electrolyte. Thus, the aforementioned lithium salt additives can form a stable SEI film on the negative electrode surface, reducing side reactions between the electrolyte and the electrode surface, reducing electrolyte decomposition, and reducing gassing of the battery cells under high temperature conditions.

[0201] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate, and the weight percentage of the lithium salt additive can be 0.02%-0.5% based on the total weight of the electrolyte. This improves the SEI film formation and reduces internal resistance.

[0202] As an example, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate. Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive can be 0.02%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc., or can be a range consisting of any of the above values.

[0203] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate. Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.1%-0.5%.

[0204] It should be noted that as the battery cells are charged and discharged, when the amount of carbonate additives, sultone additives, lithium salt additives, and phosphate additives added is small, and the additives in the electrolyte will be consumed during the formation and charge-discharge cycle to generate relevant components in the SEI film and / or CEI film, after disassembling the battery cells to obtain the electrolyte, when the content of carbonate additives, sultone additives, lithium salt additives, and phosphate additives is tested by gas chromatography, the content may be 0.

[0205] Furthermore, regarding the addition of certain substances, such as additives, to the electrolyte, the content of additives in the battery cell electrolyte is related to the formation process, different battery life cycles, or different battery storage conditions due to the additives' role in film formation on the surface of the active material. Therefore, the additive content in a freshly prepared electrolyte may differ from that in an electrolyte obtained by reverse disassembling a battery cell. However, those skilled in the art can determine the approximate content range of the relevant substances in the fresh electrolyte based on the performance level of the battery cell (such as the number of cycles) and residual content. Similarly, those skilled in the art can also determine the approximate content range of the corresponding non-freshly prepared (i.e., after reverse disassembly) electrolyte based on the content of the freshly prepared additives, the performance requirements for the battery cell, the storage environment, etc.

[0206] Therefore, the additive content mentioned in the technical solution of the present application can be the content of the additive actively added to the fresh electrolyte, or it can be the content of the residual additive detected by reverse detection based on the actual battery status.

[0207] According to some embodiments of the present application, the conductivity of the electrolyte at room temperature may be 10 mS / cm-14 mS / cm, thereby increasing the lithium ion migration rate and improving the fast charging performance of the battery cell.

[0208] As an example, the conductivity of the electrolyte at room temperature can be 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, etc., or can be a range consisting of any of the above values.

[0209] In this application, after disassembling the battery cells to obtain the electrolyte, a conductivity meter is used. The conductivity of the electrolyte at room temperature can be tested with reference to HG-T 4067-2015.

[0210] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0211] The third aspect of the present application provides an electrical device, comprising the battery cell provided by the first aspect of the present application or the battery device provided by the second aspect of the present application, wherein the battery cell or the battery device provides electrical energy for the electrical device.

[0212] The power-consuming device includes at least one of the battery cells, battery modules, or battery packs provided herein. The battery cells, battery modules, or battery packs can serve as either a power source or an energy storage unit for the power-consuming device. The power-consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, and energy storage systems.

[0213] As the electrical equipment, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0214] Figure 9 This is an example of an electric device. This electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the electric device, a battery pack or battery module can be used.

[0215] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0216] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0217] Example 1

[0218] 1. Preparation of positive electrode sheet

[0219] The positive electrode sheet includes a positive electrode collector, a positive electrode active material layer and a positive electrode conductive layer. The positive electrode active material layer is arranged on both sides of the positive electrode collector. The positive electrode conductive layer is located between the positive electrode collector and the positive electrode active material layer. The positive electrode collector is aluminum foil.

[0220] The positive conductive layer on the positive current collector is a film layer formed by evenly mixing the positive electrode conductive agent superconducting carbon, the positive electrode binder polyvinylidene fluoride PVDF and the solvent N-methylpyrrolidone (NMP), and then coating it on the surface of the positive electrode collector and drying it. The thickness is 1μm. The mass content of the positive electrode conductive agent in the positive conductive layer is 45%, and the mass content of the positive electrode binder is 55%.

[0221] The positive electrode active material layer includes a film layer formed by uniformly coating the positive electrode slurry (solvent is NMP) on the surface of the positive electrode conductive layer, drying, and cold pressing. The positive electrode active material layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black in a mass ratio of 97:1.8:1.2.

[0222] The positive electrode active material includes lithium iron phosphate particles, which are doped with the elements V, Ti, Mg, and Nb. Based on the total mass of the positive electrode active material layer, V accounts for 0.09% by weight, Ti accounts for 0.04% by weight, Nb accounts for 0.02% by weight, and Mg accounts for 0.04% by weight. The average particle size of the primary particles of the lithium iron phosphate material is 400nm.

[0223] The single-side coating weight of the positive electrode active material layer is 0.3g / 1540.25mm 2 .

[0224] The compacted density of the positive electrode active material layer is 2.54 g / cm 3 .

[0225] The size of the positive electrode active material layer along the height direction of the battery cell is 89 mm, and the size of the positive electrode active material layer along the width direction of the battery cell is 200.5 mm.

[0226] 2. Preparation of negative electrode sheet

[0227] The negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer and a negative electrode conductive layer. The negative electrode active material layer is arranged on both sides of the negative electrode current collector. The negative electrode conductive layer is located between the negative electrode current collector and the negative electrode active material layer. The negative electrode current collector is copper foil.

[0228] The negative electrode conductive layer on the negative electrode current collector is a film layer formed by evenly mixing the negative electrode conductive agent superconducting carbon, the negative electrode binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC-Na) and the solvent water, and then coating it on the surface of the negative electrode current collector and drying it. The thickness is 1 μm, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 30%, the mass content of the negative electrode binder in the negative electrode conductive layer is 65%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0229] The negative electrode active material layer includes a film layer formed by uniformly coating the negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode conductive layer, drying, and cold pressing.

[0230] The negative electrode active material layer includes a negative electrode active material with a mass ratio of 96.8:0.7:1.5:1, a conductive agent acetylene black, a negative electrode binder styrene butadiene rubber, and a thickener sodium carboxymethyl cellulose. The graphite particles include artificial graphite particles, the surface of the artificial graphite has amorphous carbon, and the Dv50 of the graphite particles is 10.2 μm.

[0231] The dimension of the negative electrode active material layer along the height direction of the battery cell is 90 mm, and the dimension of the negative electrode active material layer along the width direction of the battery cell is 202 mm.

[0232] The single-side coating weight of the negative electrode active material layer is 0.137 g / 1540.25 mm 2 .

[0233] The compaction density of the negative electrode active material layer is 1.43 g / cm 3 .

[0234] 3. Isolation film

[0235] The separator includes a base film, the base film includes a 7 μm polyethylene film layer and a porosity of 42%;

[0236] The side of the base film facing the positive electrode has a first coating layer and a second coating layer, and the side of the base film facing the negative electrode has only the second coating layer, and the thickness of the second coating layer on both sides of the base film is the same;

[0237] The first coating layer includes polyacrylate and aluminum oxide particles dispersed on the polyacrylate. The first coating layer is a film layer formed by applying the first slurry to one side of the base film. The thickness of the first coating layer is 2 μm, and the average particle size of the aluminum oxide particles is 0.8 μm. The first coating layer includes aluminum oxide particles and a binder polyacrylate.

[0238] The second coating is a composite particle formed by polyacrylate and polyvinylidene fluoride (PVDF) particles dispersed on the polyacrylate. The second coating is a film layer formed by applying the second slurry on the base film (or the first coating). The average particle size of the PVDF particles is 200nm. The second slurry includes polyacrylate and PVDF particles. The total thickness of the two layers of the second coating is 1μm.

[0239] 4. Electrolyte

[0240] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), a chain carboxylate solvent ethyl acetate and a carbonate solvent (including dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC)) were mixed to obtain an organic solvent. Electrolyte salts and additives were dissolved in the above solvents and mixed evenly to obtain an electrolyte.

[0241] Based on the total mass of the electrolyte, the mass proportion of ethyl acetate is 16%, the mass proportion of carbonate solvent is 65%, among which the mass ratio of DMC, EC and EMC is 35:35:10.

[0242] The additives include vinylene carbonate (VC), (tris(trimethylsilyl) phosphate) (TMSP), lithium tetrafluoroborate (LiBF4), lithium fluorosulfonate, and lithium difluorooxalatoborate (LiDFOB). Based on the total mass of the electrolyte, the mass proportion of VC is 2%, the mass proportion of TMSP is 0.5%, the mass proportion of LiBF4 is 0.5%, the mass proportion of lithium fluorosulfonate is 0.5%, and the mass proportion of LiDFOB is 0.5%.

[0243] The electrolyte salts include lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6). Based on the total mass of the electrolyte, LiFSI accounts for 10% by weight and LiPF6 accounts for 5% by weight. The electrolyte conductivity at room temperature is 13mS / cm.

[0244] 5. Preparation of battery cells

[0245] refer to Figure 3 , stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, to obtain a laminated electrode assembly, and place the two electrode assemblies in a housing assembly, refer to Figure 5The two electrode assemblies are placed side by side across the thickness of the battery cell, with the positive and negative terminals located on the cover. After baking, the electrolyte is injected and the battery cell is produced through vacuum packaging, resting, formation, and shaping. The cell measures 104.8mm in height, 208.3mm in width, and 50.5mm in thickness.

[0246] It should be noted that, along the height direction of the battery cell, the size of the battery cell does not include the height of the electrode terminal exposed outside the cover plate.

[0247] refer to Figure 5 The size d1 of the first gap in the battery cell is 5.5 mm, the size d2 of the second gap is 5 mm, the size of the adapter sheet in the height direction of the battery cell is 1 mm, and the size of the adapter sheet in the thickness direction of the battery cell is 38.3 mm. The number n1 of all positive electrode tabs in the battery cell is 152, and the number n2 of positive straight sections is 152, n1 / n2=1. After the laminated electrode assembly is formed, a positive electrode tab is provided on each positive straight section.

[0248] Performance Testing

[0249] 1. Volumetric energy density

[0250] At room temperature, the battery cell is charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage of 3.65V to 0.05C, and allowed to stand for 30 minutes; it is discharged at a constant current of 0.33C to 2.0V, and the discharge capacity A0 at this time is recorded in Ah; the length, width, and height of the battery cell are measured with a caliper, and the volume of the battery cell V0 is calculated in L; the volume energy density of the battery cell VED = (A0 × discharge platform voltage) / V0, in Wh / L.

[0251] 2. Cycle performance under fast charging conditions

[0252] Charge from 0% SOC to 10% SOC at 0.5C constant current;

[0253] Afterwards, illustratively, the step of charging the battery device or any battery cell constituting the battery device from 10% SOC to 80% SOC may be performed as follows:

[0254] Charge from 10% SOC to 15% SOC at 5.0C constant current;

[0255] Charge from 15% SOC to 20% SOC at 4.6C constant current;

[0256] Charge from 20% SOC to 35% SOC at 4.2C constant current;

[0257] Charge from 35% SOC to 45% SOC at 3.8C constant current;

[0258] Charge from 45% SOC to 50% SOC at 3.6C constant current;

[0259] Charge from 50% SOC to 60% SOC at 3.4C constant current;

[0260] Charge from 60% SOC to 70% SOC at 3.0C constant current;

[0261] Charge from 70% SOC to 75% SOC at 2.8C constant current;

[0262] Charge from 75% SOC to 80% SOC at 2.4C constant current;

[0263] Then charge from 80% SOC to 100% SOC at 0.5C constant current;

[0264] After fully charged, discharge at 1C to 2.5V.

[0265] Repeat the above steps until the capacity decays to 80% SOH of the initial capacity, and count the number of cycles.

[0266] Example 2

[0267] The positive electrode sheet, the negative electrode sheet, the preparation method of the electrolyte, the size of the first gap in the battery cell, the size of the second gap, the size of the adapter in the thickness direction and the width direction of the battery cell, and the size of the battery cell are the same as in Example 1, except that, Figure 1 In the process of preparing battery cells, the electrode assembly is stacked in the order of positive electrode sheet, separator, and negative electrode sheet, and then wound to form a wound electrode assembly. Figure 5 Two electrode assemblies are placed in the housing assembly, namely the first electrode assembly 30 and the second electrode assembly 40. The first electrode assembly 30 and the second electrode assembly 40 are arranged side by side in the thickness direction Y of the battery cell. The number n1 of all positive electrode tabs in the battery cell is 114, the number n2 of positive electrode straight sections is 152, n1 / n2=0.75, and the arrangement of the positive electrode tabs is as follows:

[0268] The first electrode assembly 30 and the second electrode assembly 40 contain 76 positive straight segments and 57 positive electrode tabs, respectively. On the 38 positive straight segments of the first electrode assembly 30 close to the second electrode assembly 40, a positive electrode tab is set on every two positive straight segments. On the 38 positive straight segments of the first electrode assembly 30 away from the second electrode assembly 40, a positive electrode tab is set on each positive straight segment.

[0269] The second electrode assembly 40 is close to the 38 positive straight segments of the first electrode assembly 30, and a positive electrode tab is set on every two positive straight segments. The second electrode assembly 40 is away from the 38 positive straight segments of the first electrode assembly 30, and a positive electrode tab is set on each positive straight segment.

[0270] Example 3

[0271] The positive electrode sheet, the negative electrode sheet, the preparation method of the electrolyte, the size of the first gap in the battery cell, the size of the second gap, the size of the adapter in the thickness direction and the width direction of the battery cell, and the size of the battery cell are the same as in Example 1, except that, Figure 1 In the process of preparing battery cells, the electrode assembly is stacked in the order of positive electrode sheet, separator, and negative electrode sheet, and then wound to form a wound electrode assembly. Figure 5 Two electrode assemblies are placed in the housing assembly, namely the first electrode assembly 30 and the second electrode assembly 40. The first electrode assembly 30 and the second electrode assembly 40 are arranged side by side in the thickness direction Y of the battery cell. The number n1 of all positive electrode tabs in the battery cell is 134, the number n2 of positive electrode straight sections is 152, n1 / n2=0.88, and the arrangement of the positive electrode tabs is as follows:

[0272] The first electrode assembly 30 and the second electrode assembly 40 contain 76 positive straight segments and 67 positive electrode tabs, respectively. On the 18 positive straight segments of the first electrode assembly 30 close to the second electrode assembly 40, a positive electrode tab is set on every two positive straight segments. On the 58 positive straight segments of the first electrode assembly 30 away from the second electrode assembly 40, a positive electrode tab is set on each positive straight segment.

[0273] The second electrode assembly 40 is close to the 18 positive straight segments of the first electrode assembly 30, and a positive electrode tab is set on every two positive straight segments. The second electrode assembly 40 is away from the 58 positive straight segments of the first electrode assembly 30, and a positive electrode tab is set on each positive straight segment.

[0274] Example 4

[0275] The positive electrode sheet, the negative electrode sheet, the preparation method of the electrolyte, the size of the first gap in the battery cell, the size of the second gap, the size of the adapter in the thickness direction and the width direction of the battery cell, and the size of the battery cell are the same as in Example 1, except that, Figure 1 In the process of preparing battery cells, the electrode assembly is stacked in the order of positive electrode sheet, separator, and negative electrode sheet, and then wound to form a wound electrode assembly. Figure 5Two electrode assemblies are placed in the outer shell assembly, namely the first electrode assembly 30 and the second electrode assembly 40. The first electrode assembly 30 and the second electrode assembly 40 are arranged side by side in the thickness direction Y of the battery cell. The number n1 of all positive electrode tabs in the battery cell is 152, the number n2 of positive straight sections is 152, n1 / n2=1, and the positive electrode tabs are arranged in such a way that each positive straight section is provided with a positive electrode tab.

[0276] Comparative Example 1

[0277] The positive electrode sheet, the negative electrode sheet, the preparation method of the electrolyte, the size of the first gap in the battery cell, the size of the second gap, the size of the adapter in the thickness direction and the width direction of the battery cell, and the size of the battery cell are the same as in Example 1, except that, Figure 1 In the process of preparing battery cells, the electrode assembly is stacked in the order of positive electrode sheet, separator, and negative electrode sheet, and then wound to form a wound electrode assembly. Figure 5 Two electrode assemblies are placed in the outer shell assembly, namely the first electrode assembly 30 and the second electrode assembly 40. The first electrode assembly 30 and the second electrode assembly 40 are arranged side by side in the thickness direction Y of the battery cell. The number n1 of all positive electrode tabs in the battery cell is 76, and the number n2 of positive straight segments is 152. n1 / n2=0.5. The positive electrode tabs are arranged in such a way that after the wound electrode assembly is formed, a positive electrode tab is arranged on every two positive straight segments.

[0278] The detailed differences and test results of the battery cells in Examples 1 to 4 and Comparative Example 1 are shown in Table 1.

[0279] Table 1

[0280]

[0281] It can be seen from Table 1 that when the sizes of the first gap and the second gap are within the range specified in the present application, whether it is a wound electrode assembly or a laminated electrode assembly, by making the number of positive electrode tabs and the number of positive electrode straight sections within the range specified in the present application, the shunt capacity of the positive electrode tabs can be improved under fast charging conditions, the heat generation of the battery cell can be reduced, and the cycle performance of the battery cell can be improved.

[0282] If the ratio of n1 to n2 is too small, the insufficient current capacity of the positive electrode tab under fast charging conditions will increase internal resistance and heat generation, and reduce the cycle performance of the battery cell.

[0283] Whether it is a laminated electrode assembly or a wound electrode assembly, when the ratio of n1 to n2 is greater than 1, multiple tabs need to be provided in the width direction of the battery cell, and the tabs will interfere with the explosion-proof valve, adapter, etc.

[0284] The preparation method of the battery cell is the same as that of Example 1, except that the size of the first gap d1 = 0, the size of the second gap d2 = 9 mm, and the size of the adapter in the thickness direction of the battery cell is 49.3 mm.

[0285] Example 6

[0286] The preparation method of the battery cell is the same as that of Example 1, except that the size of the first gap d1 = 2.5 mm, the size of the second gap d2 = 6 mm, and the size of the adapter in the thickness direction of the battery cell is 44.3 mm.

[0287] Example 7

[0288] The preparation method of the battery cell is the same as that of Example 1, except that the size of the first gap d1 = 8 mm, the size of the second gap d2 = 4.8 mm, and the size of the adapter in the thickness direction of the battery cell is 33.3 mm.

[0289] Comparative Example 3

[0290] The preparation method of the battery cell is the same as that of Example 1, except that the size of the first gap d1 = 2.5 mm, the size of the second gap d2 = 4.8 mm, and the size of the adapter in the thickness direction of the battery cell is 29.3 mm.

[0291] The detailed differences and test results of the battery cells in Comparative Example 2, Comparative Example 3, Example 1, Example 6, and Example 7 are shown in Table 2.

[0292] Table 2

[0293]

[0294] When the shell size is constant, the size of the first gap can be adjusted by adjusting the size of the adapter in the thickness direction of the battery cell. As the size of the first gap increases, the first gap can accommodate the bent tab, and the size of the second gap can be reduced. As can be seen in Table 2, by ensuring that the sizes of the first gap and the second gap are both within the scope of protection of this application, space can be provided to accommodate the bent tab, increasing the area of ​​the active material area and improving the energy density of the battery cell. At the same time, when used with an adapter of appropriate size, the current flow capacity of the adapter under fast charging conditions is improved, heat generation is reduced, and internal resistance is lowered, thereby improving the cycle life of the battery cell under fast charging conditions.

[0295] If the size of the first gap is too small, a larger second gap needs to be provided to accommodate the folded tab, which will reduce the utilization rate of the active material in the shell space and lose the energy density of the battery cell.

[0296] If the size of the first gap is too large, the size of the adapter in the thickness direction of the battery cell will become smaller, which will reduce the welding area between the adapter and the folded ear, reduce the current capacity of the adapter, increase the internal resistance of the battery cell, and reduce the cycle performance of the battery cell under fast charging conditions.

[0297] It should be noted that when the shell size is constant, the size of the first gap can be adjusted by adjusting the size of the adapter plate; when the size of the adapter plate is constant, the size of the first gap can also be adjusted by adjusting the size of the shell in the thickness direction of the battery cell.

[0298] Comparative Example 4

[0299] The preparation method of the battery cell is the same as that of Example 1, except that the size of the second gap d2 is 4 mm.

[0300] Example 8

[0301] The preparation method of the battery cell is the same as that of Example 1, except that the size of the second gap d2 is 7.5 mm.

[0302] Comparative Example 5

[0303] The preparation method of the battery cell is the same as that of Example 1, except that the size of the second gap d2 is 10 mm.

[0304] The detailed differences and test results of the battery cells in Example 1, Comparative Example 4, Comparative Example 5, and Example 8 are shown in Table 3.

[0305] Table 3

[0306]

[0307] It can be seen from Table 3 that when the ratio of n1 to n2 and the size of the first gap are within the range specified in this application, a battery cell with both higher energy density and better cycle performance can be obtained by making the size of the second gap within the range specified in this application.

[0308] If the size of the second gap is too small, the space reserved for the folded tab is small, the positive electrode tab and the pole piece are in contact and compressed, the interlayer spacing between the pole pieces becomes larger, the lithium ion transmission resistance increases, and the cycle performance of the battery cell is reduced.

[0309] If the size of the second gap is too large, the utilization rate of the active material in the housing space will be reduced, resulting in a loss of energy density of the battery cell.

[0310] Example 9

[0311] The preparation method of the battery cell is the same as that of Example 1, except that the dimension of the adapter in the thickness direction of the battery cell is 0.4 mm.

[0312] Example 10

[0313] The preparation method of the battery cell is the same as that of Example 1, except that the dimension of the adapter in the thickness direction of the battery cell is 0.6 mm.

[0314] Example 11

[0315] The preparation method of the battery cell is the same as that of Example 1, except that the dimension of the adapter in the thickness direction of the battery cell is 2 mm.

[0316] Example 12

[0317] The preparation method of the battery cell is the same as that of Example 1, except that the dimension of the adapter in the thickness direction of the battery cell is 4 mm.

[0318] The detailed differences and test results of the battery cells in Examples 1 and 9 to 12 are shown in Table 4.

[0319] Table 4

[0320]

[0321] It can be seen from Table 4 that when the ratio of n1 and n2, the size of the first gap, and the size of the second gap are within the range specified in this application, by making the size of the adapter in the height direction of the battery cell within the range specified in this application, the space occupied by the adapter in the shell can be reduced, and at the same time, the cross-sectional area of ​​the adapter is increased, and the current flow capacity of the adapter is improved, thereby obtaining a battery cell with both higher energy density and better cycle performance.

[0322] Example 13

[0323] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of ethyl acetate is 9%, and the mass proportion of the carbonate additive is 72%.

[0324] Example 14

[0325] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of ethyl acetate is 10%, and the mass proportion of the carbonate additive is 71%.

[0326] Example 15

[0327] The preparation method of the battery cell is the same as that of Example 1, except that, based on the total mass of the electrolyte, the mass proportion of ethyl acetate is 35%, and the mass proportion of the carbonate additive is 46%.

[0328] The detailed differences and test results of the battery cells in Example 1, Example 13, and Example 15 are shown in Table 5.

[0329] Table 5

[0330]

[0331] Table 5 shows that when the ratio of n1 to n2, the size of the first gap, and the size of the second gap are within the ranges specified in this application, the cycling performance of the battery cell under fast-charging conditions can be further optimized by adjusting the content of carboxylate and carbonate solvents in the electrolyte. Carboxylate solvents have a low molecular weight and can reduce the viscosity of the electrolyte, increase the migration rate of lithium ions, and improve the fast-charging performance of the battery cell.

[0332] Example 16

[0333] The preparation method of the battery monomer is the same as that of Example 1, except that the mass proportion of the carbonate solvent is 66%, the mass proportion of LiPF6 is 7%, the mass proportion of LiFSI is 7%, and the mass ratio of LiPF6 to LiFSI is 1:1.

[0334] Example 17

[0335] The preparation method of the battery monomer is the same as that of Example 1, except that the mass proportion of the carbonate solvent is 67.17%, the mass proportion of LiPF6 is 7%, the mass proportion of LiFSI is 5.83%, and the mass ratio of LiPF6 to LiFSI is 1.2:1.

[0336] Example 18

[0337] The preparation method of the battery monomer is the same as that of Example 1, except that the mass proportion of the carbonate solvent is 64%, the mass proportion of LiPF6 is 12%, the mass proportion of LiFSI is 4%, and the mass ratio of LiPF6 to LiFSI is 3:1.

[0338] Example 19

[0339] The preparation method of the battery monomer is the same as that of Example 1, except that the mass proportion of the carbonate solvent is 64.25%, the mass proportion of LiPF6 is 12%, the mass proportion of LiFSI is 3.75%, and the mass ratio of LiPF6 to LiFSI is 3.2:1.

[0340] The detailed differences and test results of the battery cells in Examples 1 and 16 to 19 are shown in Table 6.

[0341] Table 6

[0342]

[0343] It can be seen from Table 6 that when the ratio of n1 and n2, the size of the first gap, and the size of the second gap are within the range specified in this application, by making the mass ratio of LiPF6 and LiFSI in the electrolyte within a certain range, the lithium ion transmission rate can be increased and the cycle performance of the battery cell under fast charging conditions can be improved.

[0344] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that: The invention comprises a housing assembly and an electrode assembly, wherein the electrode assembly is accommodated in the housing assembly, the housing assembly comprises a shell and a cover assembly, the cover assembly covers the shell, the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet, and the cover assembly comprises a cover and an electrode terminal; wherein, The positive electrode sheet includes a positive electrode coating portion and a positive electrode tab, wherein the positive electrode coating portion is coated with a positive electrode active material layer, wherein the positive electrode active material layer includes a lithium-containing phosphate; the negative electrode sheet includes a negative electrode coating portion and a negative electrode tab, wherein the negative electrode coating portion is coated with a negative electrode active material layer, wherein the negative electrode active material layer includes graphite; and the positive electrode tab and the negative electrode tab are both electrically connected to the electrode terminal via an adapter sheet; The positive electrode coating portion includes a positive electrode straight segment, and the negative electrode coating portion includes a negative electrode straight segment. The positive electrode straight segments and the negative electrode straight segments are stacked along the thickness direction of the electrode assembly. The number of the positive electrode tabs is n1, and the number of the positive electrode straight segments is n2. The ratio of n1 to n2 is 3 / 4-1, and the range of n1 is 110-220, and the unit is: piece; The adapter plate is a sheet-shaped conductive member. Along the thickness direction of the battery cell, the adapter plate includes an end surface close to the side wall of the shell. A first gap is formed between the end surface and the inner wall of the side wall for accommodating the positive electrode tab, wherein the size of the first gap is 2.5 mm-8 mm; Along the height direction of the battery cell, the adapter plate has a surface facing the electrode assembly, and a second gap is formed between the surface and the edge of the negative electrode active material layer for accommodating the positive electrode tab, wherein the size of the second gap is 4.5mm-7.5mm.

2. The battery cell according to claim 1, wherein: Along the height direction of the battery cell, the positive electrode tab extends from the positive electrode straight section, and the negative electrode tab extends from the negative electrode straight section.

3. The battery cell according to claim 1, wherein: Along the height direction of the battery cell, the size of the adapter plate is 0.6mm-2mm.

4. The battery cell according to claim 1, wherein: Along the thickness direction of the battery cell, the size of the adapter plate is 15mm-60mm.

5. The battery cell according to claim 1, characterized in that The positive electrode tab includes a bending portion and a welding portion. The welding portion of the positive electrode tab and the adapter are welded to form a welding area. The area of ​​the welding area is 10 mm 2 -40mm 2 .

6. The battery cell according to claim 1, characterized in that The size of the battery cell is 120 mm to 350 mm along the width direction of the battery cell, 80 mm to 120 mm along the height direction of the battery cell, and 25 mm to 80 mm along the thickness direction of the battery cell.

7. The battery cell according to claim 1, characterized in that Along the width direction of the positive electrode sheet, the positive electrode tab includes a hollow foil area and an inorganic coating area, and the inorganic coating area is located between the positive electrode coating portion and the hollow foil area, wherein: The empty foil area is used to electrically connect to the electrode terminal, the inorganic coating area includes an inorganic coating, and the inorganic coating includes inorganic particles and an adhesive. Along the width direction of the positive electrode sheet, the size of the inorganic coating accounts for 1 / 15-1 / 4 of the size of the positive electrode tab.

8. The battery cell according to claim 7, characterized in that The positive electrode coating portion includes an active area and an inactive area, the positive electrode active material layer is located in the active area, the inactive area is located between the inorganic coating area and the active area, and is connected to the inorganic coating area and the active area, wherein the size of the inactive area along the width direction of the positive electrode plate is 1.5mm-3mm.

9. The battery cell according to claim 1, characterized in that The positive electrode sheet includes a positive electrode current collector, and the thickness of the positive electrode current collector is 5.5%-8% of the thickness of the positive electrode sheet.

10. The battery cell according to claim 1, characterized in that The porosity of the positive electrode sheet is 25%-30%.

11. The battery cell according to claim 1, characterized in that The single-side coating weight of the positive electrode active material layer is 0.26 g / 1540.25 mm 2 -0.33g / 1540.25mm 2 .

12. The battery cell according to claim 1, wherein The single-side coating weight of the positive electrode active material layer is 0.28 g / 1540.25 mm 2 -0.32g / 1540.25mm 2 .

13. The battery cell according to claim 1, characterized in that The compaction density of the positive electrode active material layer is 2.3 g / cm 3 -2.65g / cm 3 .

14. The battery cell according to claim 1, characterized in that The compaction density of the positive electrode active material layer is 2.45 g / cm 3 -2.58g / cm 3 .

15. The battery cell according to claim 1, characterized in that The lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

16. The battery cell according to claim 1, characterized in that The lithium-containing phosphate includes lithium iron phosphate, and the average particle size of the lithium iron phosphate primary particles is 300nm-800nm.

17. The battery cell according to claim 16, characterized in that The lithium iron phosphate includes doping elements, and the doping elements include one or more of V, Ti, Mg, and Nb.

18. The battery cell according to claim 17, characterized in that Based on the total mass of the positive electrode active material layer, the mass proportion of the V element is 0.02%-0.2%, the mass proportion of the Ti element is 0.03%-0.2%, the mass proportion of the Mg element is 0.02%-0.1%, and the mass proportion of the Nb element is 0.02%-0.2%.

19. The battery cell according to claim 1, characterized in that The negative electrode plate includes a negative electrode current collector, and the thickness of the negative electrode current collector is 2.5%-6% of the thickness of the negative electrode plate.

20. The battery cell according to claim 1, characterized in that The coating weight of the negative electrode active material layer on one side is 0.12 g / 1540.25 mm 2 -0.15g / 1540.25mm 2 .

21. The battery cell according to claim 1, characterized in that The coating weight of the negative electrode active material layer on one side is 0.125 g / 1540.25 mm 2 -0.14g / 1540.25mm 2 .

22. The battery cell according to claim 1, characterized in that The compaction density of the negative electrode active material layer is 1.3 g / cm 3 -1.52g / cm 3 .

23. The battery cell according to claim 1, characterized in that The porosity of the negative electrode plate is 25%-30%.

24. The battery cell according to claim 1, characterized in that The graphite includes secondary particles having amorphous carbon on at least a portion of the surface of the secondary particles.

25. The battery cell according to claim 1, characterized in that The volume average particle size Dv50 of the graphite is 7 μm-12 μm.

26. The battery cell according to claim 1, characterized in that The graphitization degree of the graphite is 90%-94%.

27. The battery cell according to claim 1, characterized in that The battery cell further includes an electrolyte, and the electrolyte includes at least one of a carbonate solvent and a carboxylate solvent.

28. The battery cell according to claim 27, characterized in that Based on the total mass of the electrolyte, the mass proportion of the carbonate solvent is 20%-75%.

29. The battery cell according to claim 27, characterized in that Based on the total mass of the electrolyte, the mass proportion of the carboxylate solvent is 10%-35%.

30. The battery cell according to claim 27, wherein: The carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

31. The battery cell according to claim 27, characterized in that The carboxylate solvent includes R1-COO-R2, R1 includes any one of a hydrogen atom, a halogen atom, a C1-C5 alkyl group, and a C1-C5 halogenated alkyl group, and R2 includes any one of a C1-C5 alkyl group and a C1-C5 halogenated alkyl group.

32. The battery cell according to claim 27, wherein: The carboxylate solvent includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

33. The battery cell according to claim 27, characterized in that The electrolyte further includes an electrolyte salt, which includes fluorinated lithium sulfonyl imide and lithium hexafluorophosphate. Based on the total mass of the electrolyte, the mass of the electrolyte salt accounts for 12%-18%.

34. The battery cell according to claim 33, characterized in that The mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide is (1.2-3):

1.

35. The battery cell according to claim 33, characterized in that Based on the total mass of the electrolyte, the mass of the lithium hexafluorophosphate accounts for 4%-14%.

36. The battery cell according to claim 33, characterized in that Based on the total mass of the electrolyte, the mass proportion of the fluorinated lithium sulfonyl imide is 4%-8%.

37. The battery cell according to claim 27, characterized in that The electrolyte further includes additives, and the additives include one or more of carbonate additives, sultone additives, lithium salt additives, and phosphate additives.

38. The battery cell according to claim 37, characterized in that Based on the total mass of the electrolyte, the mass proportion of the additive is 0.1%-5%.

39. The battery cell according to claim 37, characterized in that The electrolyte includes the carbonate additive and the phosphate additive. Based on the total mass of the electrolyte, the sum of the mass proportions of the carbonate additive and the phosphate additive is 0.1%-0.5%.

40. The battery cell according to claim 37, wherein: The carbonate additive includes vinylene carbonate, and the phosphate additive includes tris(trimethylsilyl)phosphate. Based on the total mass of the electrolyte, the mass proportion of the carbonate additive and the phosphate additive is 0.1%-0.5%.

41. The battery cell according to claim 37, characterized in that The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bis(oxalatoborate), and lithium fluorosulfonate.

42. The battery cell according to claim 37, wherein: The lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate. Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.02%-0.5%.

43. The battery cell according to claim 37, characterized in that The lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate. Based on the total mass of the electrolyte, the mass proportion of the lithium salt additive is 0.1%-0.5%.

44. The battery cell according to claim 27, characterized in that The conductivity of the electrolyte is 10mS / cm-14mS / cm at room temperature.

45. A battery device, characterized in that: The battery device comprises the battery cell according to any one of claims 1 to 44, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

46. ​​An electrical device, characterized in that: The battery cell according to any one of claims 1 to 44 or the battery device according to claim 45 is included, and the battery cell or the battery device provides electrical energy for the electrical device.

Images