Battery cells, battery devices, and electrical equipment

Abstract

This application discloses a battery cell, a battery device, and an electrical device. The battery cell includes a laminated electrode assembly and a housing. Along the height of the battery cell, the dimensions of the positive electrode active material layer account for 83%-88% of the dimensions of the housing. Along the height of the battery cell, the difference between the dimensions of the negative electrode active material layer and the positive electrode active material layer is OH1, 1.5mm≤OH1≤3.3mm. Along the height of the battery cell, the difference between the dimensions of the separator and the negative electrode active material layer is OH3, 3mm≤OH3≤10mm. This battery cell can reduce the probability of shorting between the positive and negative electrode sheets, reduce battery self-discharge, minimize capacity loss, and improve the high-temperature storage life of the battery cell.

Description

[0001] This application claims priority to PCT international application PCT / CN2025 / 092193, entitled “Battery Cell, Battery Device, and Electrical Equipment,” filed on April 29, 2025, the entire contents of which are incorporated by reference into this application. 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 energy density and safety performance under fast-charging conditions. Summary of the Invention

[0004] In a first aspect, the present application provides a battery cell, comprising a laminated electrode assembly and a housing, wherein the housing defines a receiving cavity, the laminated electrode assembly is disposed within the receiving cavity, and the laminated electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet;

[0005] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes a lithium-containing phosphate, and the positive electrode current collector includes a coating portion and a tab portion. The positive electrode active material layer is disposed on at least one surface of the coating portion. Along the height direction of the battery cell, the tab portion extends from the coating portion. Along the height direction of the battery cell, the size of the positive electrode active material layer accounts for 83%-88% of the size of the housing;

[0006] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. Along the height direction of the battery cell, the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1, and satisfies 1.5 mm ≤ OH1 ≤ 3.3 mm.

[0007] Along the height direction of the battery cell, a difference between a size of the separator and a size of the negative electrode active material layer is OH3, and 3 mm ≤ OH3 ≤ 10 mm is satisfied.

[0008] The battery cell proposed in this application achieves a high energy density by controlling the difference in dimensions between the negative and positive active material layers in the height direction of the battery cell, as well as the ratio of the positive active material layer to the housing size within an appropriate range. Furthermore, to reduce the probability of short circuits caused by misalignment of the positive and negative electrode sheets, a separator of appropriate dimensions is used. By ensuring that the difference in dimensions between the separator and the negative active material layer in the height direction of the battery cell is within an appropriate range, the probability of short circuits between the positive and negative electrode sheets is reduced, thereby reducing battery self-discharge, capacity loss, and extending the high-temperature storage life of the battery cell.

[0009] According to some embodiments of the present application, along the width direction of the battery cell, the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH2, OH2>OH1, and the width direction is perpendicular to the height direction. This improves the energy density of the battery cell.

[0010] According to some embodiments of the present application, 1.5 mm ≤ OH2 ≤ 3.5 mm, thereby increasing the energy density of the battery cell.

[0011] According to some embodiments of the present application, along the width direction of the battery cell, the size of the positive electrode active material layer accounts for 95%-97.5% of the size of the shell, thereby increasing the area of ​​the active region and improving the energy density of the battery cell.

[0012] According to some embodiments of the present application, 1.5 mm ≤ OH1 ≤ 2.5 mm, thereby increasing the energy density of the battery cell.

[0013] According to some embodiments of the present application, the separator includes a base film and a coating disposed on at least one side of the base film. The coating includes a binder and fluorine-containing organic particles, and the total thickness of the coating is 3 μm to 7 μm. This improves the bonding effect with the positive and negative electrode sheets, reduces the probability of misalignment of the positive and negative electrode sheets, and improves the safety of the battery cell.

[0014] According to some embodiments of the present application, the fluorine-containing organic particles include polyvinylidene fluoride particles, and the average particle size of the polyvinylidene fluoride particles is 10nm-100nm. Therefore, the smaller average particle size of the polyvinylidene fluoride particles can improve the adhesion of the separator to the positive and negative electrode sheets, reducing the risk of misalignment of the positive and negative electrode sheets.

[0015] According to some embodiments of the present application, the coating includes: a first coating layer, disposed on at least one side of the base film, comprising a first binder and first inorganic particles; and a second coating layer, disposed on a side of the first coating layer away from the base film, or disposed on a side of the base film, comprising a second binder and the fluorine-containing organic particles. This improves the thermal stability of the separator and its adhesion to the positive and negative electrode sheets.

[0016] According to some embodiments of the present application, the thickness of the first coating layer disposed on one side of the base film is 1 μm-3 μm, thereby improving the high temperature resistance of the isolation film.

[0017] According to some embodiments of the present application, the second coating layer further comprises composite particles comprising second inorganic particles and a non-fluoropolymer, wherein the second inorganic particles are attached to the surface of the non-fluoropolymer and / or dispersed within the non-fluoropolymer. This improves the heat resistance of the second coating layer, further improving the heat resistance of the separator.

[0018] According to some embodiments of the present application, the first inorganic particles and the second inorganic particles independently include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

[0019] According to some embodiments of the present application, the average particle size of the first inorganic particles and the second inorganic particles is 5 nm-200 nm.

[0020] According to some embodiments of the present application, the average particle size of the first inorganic particles and the second inorganic particles is 10 nm-100 nm.

[0021] According to some embodiments of the present application, the average particle size of the first inorganic particles and the second inorganic particles is 10 nm-20 nm.

[0022] Thus, by setting the average particle diameters of the first inorganic particles and the second inorganic particles within the above range, the heat resistance and compression modulus of the separator are improved.

[0023] According to some embodiments of the present application, the non-fluorine polymer includes an acrylic copolymer.

[0024] According to some embodiments of the present application, the acrylic ester copolymer includes an acrylic ester-acrylonitrile-acrylamide-propylene copolymer, thereby improving the heat resistance of the isolation film.

[0025] According to some embodiments of the present application, the base film includes at least one of a polyethylene base film or a polypropylene base film, and the thickness of the base film is 5 μm to 9 μm. This shortens the migration path of lithium ions in the base film, reduces the internal resistance of the battery cell, and reduces heat generation.

[0026] According to some embodiments of the present application, the porosity of the separator is 40%-55%, thereby increasing the migration rate of lithium ions in the separator, reducing the internal resistance of the battery cell, and reducing heat generation.

[0027] According to some embodiments of the present application, along the height direction of the battery cell, the tab portion includes a hollow foil area and an inorganic coating area, the inorganic coating area being located between the coating portion and the hollow foil area, wherein the hollow foil area is used to electrically connect to the electrode terminal, and the inorganic coating area includes a first inorganic coating layer, which includes the first inorganic particles and a third adhesive. Along the height direction of the battery cell, the size of the first inorganic coating layer accounts for 1 / 15 to 1 / 4 of the size of the tab portion. This reduces the probability of direct contact between the positive tab and the negative electrode sheet, and reduces the risk of short circuit between the positive and negative electrodes.

[0028] According to some embodiments of the present application, along the height direction of the battery cell, the size of the inorganic coating area of ​​the tab portion is 2mm-7.5mm, and the size of the tab portion is 25mm-45mm. This reduces the probability of direct contact between the positive tab and the negative electrode, and reduces the risk of short circuit between the positive and negative electrodes.

[0029] According to some embodiments of the present application, along the height direction of the battery cell, 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 of ​​the tab portion and the active area, and is connected to the inorganic coating area and the active area. The size of the inactive area along the height direction of the battery cell is 1.5 mm to 3 mm. This allows the trimmed edge of the negative electrode sheet to fall on the inactive area, preventing burrs on the trimmed edge of the sheet from piercing the separator and forming an electrical connection with the positive electrode sheet.

[0030] According to some embodiments of the present application, the inactive area includes a second inorganic coating layer, which includes the first inorganic particles and the third binder. This reduces the probability of direct contact between the positive electrode tab and the negative electrode tab, thereby reducing the risk of short circuit between the positive and negative electrodes.

[0031] According to some embodiments of the present application, along the height direction of the battery cell, 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 sizes of the active area and the inactive area. This improves the energy density of the battery cell while reducing the risk of short circuit between the positive and negative electrodes.

[0032] 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 / 1540.25mm 2 This increases the energy density of the battery cell.

[0033] According to some embodiments of the present application, the single-sided coating weight of the positive electrode active material layer is 0.29 g / 1540.25 mm 2 -0.31g / 1540.25mm 2 This increases the energy density of the battery cell.

[0034] 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.

[0035] According to some embodiments of the present application, the compaction density of the positive electrode active material layer is 2.45 g / cm 3 -2.6g / cm 3 This increases the energy density of the battery cell.

[0036] According to some embodiments of the present application, the single-sided coating weight of the negative electrode active material layer is 0.12 g / 1540.25 mm 2 -0.18g / 1540.25mm 2 This increases the energy density of the battery cell.

[0037] According to some embodiments of the present application, the single-sided coating weight of the negative electrode active material layer is 0.125 g / 1540.25 mm 2 -0.16g / 1540.25mm 2 This increases the energy density of the battery cell.

[0038] 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.

[0039] According to some embodiments of the present application, the compaction density of the negative electrode active material layer is 1.35 g / cm 3 -1.5g / cm 3 This increases the energy density of the battery cell.

[0040] According to some embodiments of the present application, the negative electrode active material layer includes: a first negative electrode active material layer, disposed on at least one side of the negative electrode current collector, comprising a first negative electrode active material; and a second negative electrode active material layer, disposed on a side of the first negative electrode active material layer away from the negative electrode current collector, comprising a second negative electrode active material. The first negative electrode active material and the second negative electrode active material each independently comprise graphite, and the average particle size of the graphite in the first negative electrode active material layer is greater than the average particle size of the graphite in the second negative electrode active material layer. This improves the fast charging performance and energy density of the battery cell.

[0041] According to some embodiments of the present application, the thickness of the second negative electrode active material layer accounts for 30%-70% of the thickness of the negative electrode active material layer, thereby improving the fast charging performance of the battery cell.

[0042] According to some embodiments of the present application, the average particle size of the graphite in the first negative electrode active material layer is 7 μm-18 μm, and the average particle size of the graphite in the second negative electrode active material layer is 6 μm-10 μm. This improves the fast charging performance and energy density of the battery cell.

[0043] According to some embodiments of the present application, the graphite includes secondary particles, at least part of the surface of which 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.

[0044] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite is 7 μm-15 μm, thereby shortening the solid phase migration path of lithium ions and improving the fast charging capability of the battery cell.

[0045] 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.

[0046] According to some embodiments of the present application, the negative electrode active material layer further comprises a silicon-based material, and the mass proportion of silicon is 0.5%-10% based on the total mass of the negative electrode active material layer, thereby increasing the energy density of the battery cell.

[0047] According to some embodiments of the present application, the silicon-based material includes a silicon-carbon material, thereby taking into account both the energy density and the cycle performance of the battery cell.

[0048] 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.

[0049] 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.

[0050] 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 Mg, V, Ti, and Nb. By doping the lithium iron phosphate with these elements, iron dissolution can be reduced, the lithium ion insertion and extraction rate 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.

[0051] 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%. By doping the lithium iron phosphate with the above elements, iron dissolution can be reduced, the lithium ion deintercalation rate 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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%.

[0061] 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%.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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 interface film on the electrode surface, reduces interfacial impedance, and improves the fast-charging performance of the battery cell.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] According to some embodiments of the present application, the lithium salt additive includes one or more of lithium difluorooxalatoborate, lithium tetrafluoroborate, and lithium fluorosulfonate, with the weight percentage of the lithium salt additive being 0.1%-0.5%. This improves the impedance of the SEI film and enhances power performance.

[0070] According to some embodiments of the present application, the conductivity of the electrolyte at room temperature is 10 mS / cm-13.5 mS / cm, thereby increasing the migration rate of lithium ions and improving the fast charging performance of the battery cell.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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

[0075] 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:

[0076] Figure 1 Schematic diagram of a battery cell according to one embodiment of the present application.

[0077] Figure 2 Schematic diagram of the size relationship between the negative electrode active material layer and the positive electrode active material layer in one embodiment of the present application.

[0078] Figure 3 Schematic diagram of the size relationship between the separator and the negative electrode active material layer in one embodiment of the present application.

[0079] Figure 4 Schematic diagram of an isolation membrane according to one embodiment of the present application.

[0080] Figure 5 is a schematic diagram of an isolation membrane according to another embodiment of the present application.

[0081] Figure 6 is a schematic diagram of an isolation membrane according to another embodiment of the present application.

[0082] Figure 7 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 electrode lug portion according to one embodiment of the present application.

[0083] Figure 8 Schematic diagram of a negative electrode sheet according to one embodiment of the present application.

[0084] Figure 9 It is a schematic diagram of an electrical device according to one embodiment of the present application.

[0085] Description of reference numerals:

[0086] 10 battery cell; 201 positive electrode active material layer; 202 second inorganic coating layer; 11 pole ear portion; 111 first inorganic coating layer; 112 empty foil area; 101 negative electrode active material layer; 12 negative electrode current collector; 102 first negative electrode active material layer; 103 second negative electrode active material layer; 3 isolation membrane; 311 base membrane; 30 coating layer; 312 first coating layer; 313 second coating layer; 6 cover plate. DETAILED DESCRIPTION

[0087] 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.

[0088] 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.

[0089] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The present application proposes a battery cell, in which the positive electrode sheet and the negative electrode sheet are stacked. Compared with the winding arrangement, the stacked arrangement of the electrode sheets can make better use of the space in the thickness direction of the battery shell, thereby improving the energy density of the battery cell. In order to simultaneously meet the needs of fast current transmission and the assembly requirements of improving the energy density of the battery pack, the tabs are arranged to extend from the electrode sheets along the height direction of the battery cell. However, when the positive electrode tabs are electrically connected to the electrode terminals, they will 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 terminals to accommodate the bent tabs, thereby avoiding the bent tabs from being inserted into the active layer area of ​​the electrode sheet and causing an internal short circuit. However, this "redundant space" arrangement is bound to result in a reduction in the utilization rate of the shell space by the active material layer, thereby losing the energy density of the battery cell. The present application can increase the area of ​​the positive active area and the energy density of the battery cell by controlling the size of the positive electrode active material layer relative to the size of the shell. However, compared with the wound electrode assembly, the laminated electrode assembly is composed of multiple sheets stacked together, and the laminated sheets are prone to misalignment during the lamination process. In addition, during the long-term cycle of the battery cell, the expansion of the electrode sheet (mainly the expansion of the negative electrode) is also more likely to cause the electrode sheets to be misaligned with each other. The expansion of the fast-charging battery cell may be more obvious. After the electrode sheet is misaligned, the positive and negative electrode overlap will continue to self-discharge, resulting in a gradual decrease in the available capacity of the battery and deterioration in the storage performance of the battery. The heat accumulation caused by the short circuit will also cause thermal runaway. The present application reduces the risk of short circuit between the positive and negative electrodes, reduces self-discharge, reduces capacity attenuation, and improves the high-temperature storage life of the battery by increasing the difference between the size of the isolation membrane and the size of the negative electrode active material layer in the height direction of the battery cell, as well as the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer.

[0094] 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.

[0095] The battery cell provided in the present application includes a laminated electrode assembly and a housing, wherein the housing defines a receiving cavity, the laminated electrode assembly is disposed in the receiving cavity, and the laminated electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet;

[0096] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes a lithium-containing phosphate, and the positive electrode current collector includes a coating portion and a tab portion. The positive electrode active material layer is disposed on at least one surface of the coating portion. Along the height direction of the battery cell, the tab portion extends from the coating portion. Along the height direction of the battery cell, the size of the positive electrode active material layer accounts for 83%-88% of the size of the housing;

[0097] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. Along the height direction of the battery cell, the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1, and satisfies 1.5 mm ≤ OH1 ≤ 3.3 mm.

[0098] Along the height direction of the battery cell, a difference between a size of the separator and a size of the negative electrode active material layer is OH3, and 3 mm ≤ OH3 ≤ 10 mm is satisfied.

[0099] refer to Figure 1 The height, width and thickness directions of the battery cell 10 proposed in this application are as follows: Figure 1 shown.

[0100] refer to Figure 2 The dimension of the negative electrode active material layer 101 along the height direction of the battery cell is OH 11 The size of the positive electrode active material layer 201 along the height direction of the battery cell is OH 21 OH1=OH 11 -OH 21 , 1.5mm≤OH1≤3.3mm.

[0101] As an example, OH1 may be 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.3 mm, etc., or may be a range consisting of any of the above values.

[0102] According to some specific embodiments of the present application, 1.5 mm ≤ OH1 ≤ 2.5 mm.

[0103] In the present application, along the height direction of the battery cell, the size of the positive electrode active material layer accounts for 83%-88% of the size of the shell, for example, it can be 83%, 84%, 85%, 86%, 87%, 88%, etc., or can be a range composed of any of the above numerical values.

[0104] In this application, reference Figure 1The shell includes side walls, bottom walls and cover plate 6. When measuring the shell size, in order to avoid the situation where the size of the shell cavity and the outside are measured differently due to the wall thickness, the shell size H1 is based on the size measured from the outside of the battery cell, that is, Figure 1 The distance between the bottom wall and the cover plate 6 formed in the height direction of the battery cell is the distance between the outer surface of the bottom wall and the outer surface of the cover plate, and does not include the height formed by the raised electrode terminals on the cover plate 6.

[0105] Along the height direction of the battery cell, a difference between a size of the separator and a size of the negative electrode active material layer is OH3, and 3 mm ≤ OH3 ≤ 10 mm is satisfied.

[0106] refer to Figure 3 , along the height direction of the battery cell, the size of the isolation film 3 is OH 31 , the size of the negative electrode active material layer 101 is OH 11 OH3=OH 31 -OH 11 .

[0107] As an example, OH3 can be 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc., or can be a range consisting of any of the above values.

[0108] In the present application, the size of the negative electrode active material layer, the size of the positive electrode active material layer, and the size of the separator can be measured by a film ruler.

[0109] The battery cell proposed in this application achieves a high energy density by controlling the difference in dimensions between the negative and positive active material layers in the height direction of the battery cell, as well as the ratio of the positive active material layer to the housing size within an appropriate range. Furthermore, to reduce the risk of short circuits caused by misalignment of the positive and negative electrode sheets, a separator of appropriate dimensions is used, ensuring that the difference in dimensions between the separator and the negative active material layer in the height direction of the battery cell is within an appropriate range. This reduces the probability of short circuits between the positive and negative electrode sheets, reduces battery self-discharge, minimizes capacity loss, and improves the high-temperature storage life of the battery cell.

[0110] According to some embodiments of the present application, along the width direction of the battery cell, the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH2, OH2>OH1, and the width direction is perpendicular to the height direction.

[0111] Specifically, refer to Figure 2 , along the width direction of the battery cell, the size of the negative electrode active material layer 101 is OH 12The size of the positive electrode active material layer 201 is OH 22 OH2=OH 12 -OH 22 OH2>OH1, and the width direction is perpendicular to the height direction. Therefore, by making OH2>OH1, that is, the overhang in the width direction is greater than the overhang in the height direction, the probability of short circuit caused by misalignment of the positive and negative electrodes can be reduced while reducing the impact on the energy density of the battery cell.

[0112] According to some embodiments of the present application, 1.5 mm ≤ OH2 ≤ 3.5 mm. For example, the range can be 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, or any range of the aforementioned values. This reduces the probability of positive and negative electrode short circuits while increasing the active area and improving the energy density of the battery cell.

[0113] According to some embodiments of the present application, along the width direction of the battery cell, the size of the positive electrode active material layer accounts for 95%-97.5% of the size of the shell.

[0114] refer to Figure 1 The housing includes side walls, a bottom wall, and a cover plate 6. When measuring the housing dimensions, to avoid differences in the dimensions of the inner and outer shells due to wall thickness, the housing dimension H2 is measured from the outside of the battery cell. This refers to the distance between the outer surfaces of two opposing side walls along the width of the battery cell. By ensuring that the dimensions of the positive electrode active material layer are within this range, the active area can be increased, thereby improving the energy density of the battery cell.

[0115] As an example, the size of the positive electrode active material layer accounts for 95%, 95.5%, 96%, 96.5%, 97%, or 97.5% of the size of the shell.

[0116] According to some embodiments of the present application, the isolation film includes a base film and a coating disposed on at least one side of the base film, the coating includes a binder and fluorine-containing organic particles, and the total thickness of the coating is 3 μm-7 μm.

[0117] refer to Figure 4 The separator 3 includes a base film 311 and a coating 30 located on at least one side of the base film 311. The total thickness of the coating 30 can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or any range thereof. This improves the adhesion of the separator to the positive and negative electrode sheets, reducing the probability of misalignment of the positive and negative electrode sheets.

[0118] In the present application, the isolation film can be cut along its thickness direction by plasma, the coating layer can be identified under a scanning electron microscope (SEM), and the thickness of the coating layer can be measured.

[0119] According to some embodiments of the present application, the fluorine-containing organic particles include polyvinylidene fluoride particles, and the average particle size of the polyvinylidene fluoride particles is 10 nm-100 nm.

[0120] For laminated electrode assemblies, the electrodes are prone to expansion during the cycle of battery cells. The average particle size of polyvinylidene fluoride particles is small and the specific surface area is large, which can improve the bonding effect of the separator to the positive and negative electrodes and reduce the risk of misalignment of the positive and negative electrodes.

[0121] In the present application, the average particle size of the polyvinylidene fluoride particles can be tested by referring to methods known in the art. For example, the following method can be referred to: the isolation film is cut along its thickness direction by plasma to obtain a cross section, 50 polyvinylidene fluoride particles are randomly selected by SEM, and the average particle size of a single polyvinylidene fluoride particle = (the longest diameter of a single particle + the shortest diameter of a single particle) / 2. The average value of the average particle sizes of the 50 polyvinylidene fluoride particles is the average particle size of the polyvinylidene fluoride particles.

[0122] As an example, the average particle size of the polyvinylidene fluoride particles can be 10 nm, 30 nm, 50 nm, 70 nm, 85 nm, 100 nm, etc., or can be within a range consisting of any of the above values.

[0123] According to some embodiments of the present application, reference Figure 5 The coating 30 includes: a first coating 312, which is arranged on at least one side of the base film 311, and the first coating 312 includes a first binder and first inorganic particles; a second coating 313, which is arranged on a side of the first coating 312 away from the base film 311, and the second coating 313 includes a second binder and the fluorine-containing organic particles.

[0124] According to some embodiments of the present application, reference Figure 6 The coating 30 includes: a first coating 312, which is arranged on one side of the base film 311, and the first coating 312 includes a first binder and first inorganic particles; a second coating 313, which is arranged on the other side of the base film 311 along the thickness direction and the side of the first coating 312 away from the base film 311, and the second coating 313 includes a second binder and the fluorine-containing organic particles.

[0125] When the isolation membrane includes only a first coating layer, the first coating layer on the isolation membrane faces the positive electrode plate. This is because the positive electrode has a high voltage, and the isolation membrane base membrane close to the positive electrode side is easily oxidized under high voltage. By making the first coating layer face the positive electrode plate, the oxidation of the base membrane by the positive electrode can be reduced.

[0126] The battery cell proposed in this application has a small overhang of the negative electrode active material layer and the positive electrode active material layer in the height direction of the battery cell. Once the positive and negative electrodes are short-circuited, heat accumulation will occur. By providing a first coating and a second coating on the base film, on the one hand, the thermal stability of the isolation film can be improved; on the other hand, the adhesion to the positive and negative electrode sheets can be improved, reducing the probability of dislocation of the positive and negative electrode sheets.

[0127] According to some embodiments of the present application, the thickness of the first coating layer disposed on one side of the base film is 1 μm-3 μm, thereby improving the high temperature resistance of the isolation film.

[0128] In the present application, the thickness of the first coating layer can be measured using a Mahr thickness gauge. Specifically, the total thickness of the isolation membrane is measured using the Mahr thickness gauge. After ultrasonic cleaning removes the coating layer, the thickness of the base membrane is measured. The difference between the two values ​​is the thickness of the coating layer. Alternatively, a scanning electron microscope can be used to photograph a cross section along the thickness direction of the isolation membrane and measure the thickness of the base membrane and coating layer.

[0129] As an example, the thickness of the first coating layer on one side of the base film may be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, etc., or may be within a range consisting of any of the above values.

[0130] According to some embodiments of the present application, the second coating layer further comprises composite particles comprising second inorganic particles and a non-fluoropolymer, wherein the second inorganic particles are attached to the surface of the non-fluoropolymer and / or dispersed within the non-fluoropolymer. Specifically, the composite particles can replace some of the fluorine-containing organic particles in the second coating layer, thereby improving the heat resistance of the second coating layer and further improving the heat resistance of the separator.

[0131] According to some embodiments of the present application, the first inorganic particles and the second inorganic particles independently include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

[0132] According to some embodiments of the present application, the average particle size of the first and second inorganic particles is 5 nm to 200 nm. By setting the average particle size of the first and second inorganic particles within the above range, the heat resistance and compression modulus of the isolation film can be improved.

[0133] In the present application, the average particle size of the first inorganic particles can be tested by methods known in the art. For example, the test can be carried out by referring to the following method: use plasma to cut the isolation membrane along its thickness direction to obtain a cross-section of the isolation membrane along the thickness direction, observe it through SEM at an appropriate magnification, and randomly select at least 50 first inorganic particles. The average particle size of a single first inorganic particle = (the longest diameter of a single particle + the shortest diameter of a single particle) / 2, and the average value of the average particle sizes of the 50 first inorganic particles is the average particle size of the first inorganic particles.

[0134] As an example, the average particle size of the first inorganic particles may be 5 nm, 10 nm, 30 nm, 50 nm, 70 nm, 85 nm, 100 nm, etc., or may be within a range consisting of any of the above values.

[0135] According to some specific embodiments of the present application, the average particle size of the first inorganic particles is 10 nm-100 nm.

[0136] According to some specific embodiments of the present application, the average particle size of the first inorganic particles is 10 nm-20 nm.

[0137] According to some embodiments of the present application, the non-fluorine polymer includes an acrylic copolymer.

[0138] According to some embodiments of the present application, the acrylic ester copolymer includes an acrylic ester-acrylonitrile-acrylamide-propylene copolymer, thereby improving the heat resistance of the isolation film.

[0139] According to some embodiments of the present application, the base film includes at least one of a polyethylene base film or a polypropylene base film, and the base film has a thickness of 5 μm to 9 μm. By ensuring that the base film thickness is within this range, the migration path of lithium ions in the base film can be shortened, reducing the internal resistance of the battery cell and reducing heat generation.

[0140] As an example, the thickness of the base film may be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, etc., or may be within a range consisting of any of the above values.

[0141] According to some embodiments of the present application, the porosity of the separator is 40%-55%. By setting the porosity of the separator within the above range, the migration rate of lithium ions in the separator can be increased, the internal resistance of the battery cell can be reduced, and heat generation can be reduced.

[0142] In this application, porosity refers to the percentage of the pore volume within the separator to the total volume of the separator. Porosity can be measured with reference to the standard GB / T 36363-2018, "Polyolefin Separators for Battery Cells." It should be noted that the actual testing process may vary slightly from the standard to obtain a more accurate test value, depending on instrument differences, test errors, and to minimize the impact of porosity on the test.

[0143] According to some embodiments of the present application, along the height direction of the battery cell, the pole ear portion includes a hollow foil area and an inorganic coating area, and the inorganic coating area is located between the coating portion and the hollow foil area, wherein:

[0144] The empty foil area is used to electrically connect to the electrode terminal. The inorganic coating area includes a first inorganic coating, which includes the first inorganic particles and a third adhesive. Along the height direction of the battery cell, the size of the first inorganic coating accounts for 1 / 15-1 / 4 of the size of the pole ear.

[0145] Along the height direction of the battery cell, the 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, and the inactive area is located between the inorganic coating area and the active area of ​​the pole ear portion, and is connected to the inorganic coating area and the active area, wherein along the height direction of the battery cell, the size of the inactive layer area is 1.5mm-3mm.

[0146] The inactive area includes a second inorganic coating layer, and the second inorganic coating layer includes the first inorganic particles and the third binder.

[0147] refer to Figure 7 , Figure 7 The relationship between the sizes of the positive electrode active material layer 201 on the positive electrode current collector, the second inorganic coating layer 202, the pole ear portion 11 on the positive electrode current collector, and the negative electrode active material layer 101 on the negative electrode current collector in the height direction of the battery cell is shown. The pole ear portion 11 includes a hollow foil area 112 and an inorganic coating area. The inorganic coating area includes a first inorganic coating layer 111. The width of the second inorganic coating layer 202 in the height direction of the battery cell is d, 1mm≤d≤2.5mm.

[0148] When the positive electrode ear is connected to the electrode terminal, it will bend in the height direction of the shell to form a "folded ear" state, that is, the empty foil area of ​​the ear will be bent in the height direction of the battery cell, thereby improving the utilization rate of the positive and negative electrode sheets at the height of the shell and improving the energy density of the battery cell. However, this method of compressing the ear bend in height can easily cause the root of the positive electrode ear or the bent part of the positive electrode ear to be inserted into the negative electrode active material area, causing a short circuit in the battery and posing a safety risk. The present application provides a second inorganic coating between the active area and the ear, and controls the width d of the second inorganic coating 202, thereby reducing the probability of direct contact between the positive electrode ear and the negative electrode sheet and reducing the risk of positive and negative short circuit.

[0149] refer to Figure 7 The dimension of the first inorganic coating 111 in the height direction of the battery cell is a, and the dimension of the pole ear portion 11 in the height direction of the battery cell is b. A / b can be 1 / 15-1 / 4. By making a / b within the above range, the direct contact between the aluminum foil and the negative electrode sheet can be reduced while reserving sufficient size for the empty foil area to be welded with the adapter sheet, thereby improving the firmness of the welding.

[0150] As an example, d may be 1 mm, 1.5 mm, 2 mm, 2.5 mm, etc., or may be a range consisting of any of the above values.

[0151] 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.

[0152] According to some embodiments of the present application, along the height direction of the battery cell, the size of the inorganic coating area of ​​the pole lug portion is 2 mm-7.5 mm, and the size of the pole lug portion is 25 mm-45 mm.

[0153] As an example, the size of the inorganic coating area may be 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7.5 mm, etc., or may be a range consisting of any of the above values.

[0154] As an example, the size of the pole lug portion may be 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, etc., or may be within a range consisting of any of the above values.

[0155] According to some embodiments of the present application, along the height direction of the battery cell, 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 7, along the height direction of the battery cell, the size of the negative electrode active material layer 101 is larger than the size of the positive electrode active material layer 201, and the size of the negative electrode active material layer 101 is smaller than the sum of the size of the positive electrode active material layer 201 and the size of the second inorganic coating 202. In this way, the cut edge of the negative electrode plate can be placed on the inorganic coating to prevent the burrs of the cut edge of the plate from piercing the separator and forming an electrical connection with the positive electrode plate. According to some embodiments of the present application, the coating weight of a single side of the positive electrode active material layer is 0.26g / 1540.25mm 2 -0.33g / 1540.25mm 2 This increases the energy density of the battery cell.

[0156] 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.

[0157] 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.

[0158] According to some embodiments of the present application, the coating weight of the positive electrode active material layer on one side may be 0.29 g / 1540.25 mm 2 -0.31g / 1540.25mm 2 .

[0159] According to some embodiments of the present application, the compaction density of the positive electrode active material layer can be 2.3 g / cm 3 -2.65g / cm 3 This increases the energy density of the battery cell.

[0160] 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.

[0161] 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.

[0162] According to some specific embodiments of the present application, the compaction density of the positive electrode active material layer can be 2.45 g / cm 3 -2.6g / cm 3 .

[0163] According to some embodiments of the present application, the coating weight of the negative electrode active material layer on one side may be 0.12 g / 1540.25 mm 2 -0.18g / 1540.25mm 2 This increases the energy density of the battery cell.

[0164] 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.

[0165] 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, 0.16g / 1540.25mm 2 、0.17g / 1540.25mm 2 , 0.18g / 1540.25mm, etc., or can be a range composed of any of the above values. 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 -0.16g / 1540.25mm 2 .

[0166] According to some embodiments of the present application, the compaction density of the negative electrode active material layer can be 1.3 g / cm 3 -1.52g / cm 3 This increases the energy density of the battery cell.

[0167] 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.

[0168] As an example, the compaction density of the negative electrode active material layer can 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.

[0169] According to some specific embodiments of the present application, the compaction density of the negative electrode active material layer is 1.35 g / cm 3 -1.5g / cm 3 .

[0170] According to some embodiments of the present application, reference Figure 8 The negative electrode active material layer 101 includes: a first negative electrode active material layer 102, which is disposed on at least one side of the negative electrode current collector 12 and includes a first negative electrode active material; a second negative electrode active material layer 103, which is disposed on a side of the first negative electrode active material layer 102 away from the negative electrode current collector 12 and includes a second negative electrode active material;

[0171] The first negative electrode active material and the second negative electrode active material each independently include graphite. The average particle size of the graphite in the first negative electrode active material layer 102 is greater than the average particle size of the graphite in the second negative electrode active material layer 103 .

[0172] The negative electrode active material layers are arranged in layers, and the average particle size of the graphite in the first negative electrode active material layer is larger than the average particle size of the graphite in the second negative electrode active material layer. The average particle size of the graphite in the first negative electrode active material layer is larger, and the porosity of the first negative electrode active material layer is larger, which can increase the transmission rate of lithium ions; the average particle size of the graphite in the second negative electrode active material layer is smaller, the specific surface area is larger, and there are more active sites, which can increase the embedding amount of lithium ions, thereby taking into account the fast charging performance and energy density of the battery cell.

[0173] In the present application, the average particle size of graphite can be tested with reference to methods known in the art. For example, the following method can be used: use plasma to cut the negative electrode sheet along its thickness direction to obtain a cross-section of the negative electrode sheet along the thickness direction, observe it through SEM at an appropriate magnification, and randomly select at least 50 graphite particles. The average particle size of a single graphite particle = (the longest diameter of a single particle + the shortest diameter of a single particle) / 2, and the average value of the average particle sizes of the 50 graphite particles is the average particle size of the graphite particles.

[0174] According to some embodiments of the present application, the first negative electrode active material layer includes artificial graphite or one or both of artificial graphite and natural graphite.

[0175] According to some embodiments of the present application, the second negative electrode active material layer includes artificial graphite or one or both of artificial graphite and natural graphite.

[0176] According to some embodiments of the present application, the thickness of the second negative electrode active material layer accounts for 30%-70% of the thickness of the negative electrode active material layer. For example, it can be 30%, 40%, 50%, 60%, 70%, etc., or any range thereof. This balances the fast charging performance and energy density of the battery cell.

[0177] According to some embodiments of the present application, the average particle size of the graphite in the first negative electrode active material layer is 7 μm-18 μm, and the average particle size of the graphite in the second negative electrode active material layer is 6 μm-10 μm.

[0178] As an example, the average particle size of the graphite in the first negative active material layer may be 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 18 μm, etc., or may be within a range consisting of any of the above values.

[0179] As an example, the average particle size of the graphite in the first negative electrode active material layer may be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc., or may be within a range consisting of any of the above values.

[0180] According to some embodiments of the present application, the graphite includes secondary particles, and at least a portion of the surface of the secondary particles has amorphous carbon.

[0181] In the present application, secondary particles refer to particles formed by the aggregation of two or more primary particles.

[0182] 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.

[0183] 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.

[0184] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite is 7 μm-15 μm.

[0185] 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.

[0186] In this application, Dv50 refers to the particle size at which the cumulative volume distribution percentage reaches 50%, as measured, for example, using a laser particle size analyzer (Malvern Master Size 2000) in accordance with 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, then rinsed with deionized water and repeatedly shaken for 5-10 times. After drying, the sample 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 GB / T 19077-2016 / ISO 13320:2009.

[0187] As an example, the volume average particle size Dv50 of the graphite may be 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, etc., or may be within a range consisting of any of the above values.

[0188] According to some embodiments of the present application, the graphite has a degree of graphitization of 90%-94%.

[0189] This improves the ion conductivity and electron conductivity of graphite, and improves the rate performance of the battery.

[0190] In this application, the test method for the degree of graphitization of graphite can be referred to: disassemble the battery cell to obtain the negative electrode sheet, scrape off the powder on the negative electrode sheet, and test 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 0.5 mm and a diameter of 25 mm, and the sample is prepared according to the flat plate 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 scanning test is performed with a step length of 0.00836° and a step length of 0.3s per step; 4. Calculate the degree of graphitization based on the test 002 crystal plane interlayer spacing (d002).

[0191] According to some embodiments of the present application, the negative electrode active material layer further comprises a silicon-based material, and the mass proportion of silicon is 0.5%-10% based on the total mass of the negative electrode active material layer, thereby increasing the energy density of the battery cell.

[0192] In the present application, the mass content of silicon in the negative electrode active material layer has a meaning well known in the art and can be detected by equipment and methods well known in the art. For example, the negative electrode plate is placed in a solvent such as water for immersion, the negative electrode active material is separated from the negative electrode current collector, and the various substances in the negative electrode film layer are obtained by filtration. The test sample is used as a test sample using an ICAP7400 model inductively coupled plasma-emission spectrometer of Thermo Fisher Scientific, USA, with reference to GB / T30902-2014 standard to obtain the silicon content.

[0193] As an example, the mass proportion of silicon element can be 0.5%, 1%, 3%, 5%, 7%, 9%, 10%, etc., or can be a range consisting of any of the above values.

[0194] According to some embodiments of the present application, the silicon-based material includes a silicon-carbon material, thereby increasing the energy density of the battery cell and reducing the volume expansion of silicon through the carbon material, thereby improving the cycle performance of the battery cell.

[0195] 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.

[0196] 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-800 nm.

[0197] As a result, the average particle size of the primary particles is relatively small, and the deintercalation path of lithium ions in the positive electrode active material is shorter, which can increase the deintercalation rate of lithium ions and improve the fast charging performance of the battery cell.

[0198] In this application, the test method for the average particle size of primary particles 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 through 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, and the average value of the selected primary particles is the average particle size of the primary particles.

[0199] 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.

[0200] 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.

[0201] According to some embodiments of the present application, 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%.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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.).

[0207] 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.

[0208] 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.

[0209] 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.

[0210] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper 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 (copper, copper 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.).

[0211] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0212] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0213] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0214] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0215] In order to improve the fast charging performance of battery cells, this application also optimizes the electrolyte.

[0216] 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.

[0217] In this application, the testing of relevant substances in 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.

[0218] 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.

[0219] 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.

[0220] 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.

[0221] According to some specific embodiments of the present application, the mass proportion of the carboxylate solvent is 10%-60% 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.

[0222] As an example, based on the total mass of the electrolyte, the mass proportion of the carboxylate solvent can be 10%, 20%, 30%, 40%, 50%, 60%, etc., or can be a range consisting of any of the above values.

[0223] According to some specific embodiments of the present application, the mass proportion of the carboxylate solvent can be 15%-35% based on the total mass of the electrolyte, thereby improving the high-temperature cycle life of the battery cell.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] 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.

[0236] In this application, the relevant components of the electrolyte can refer to GB / T9722-2023 "General Rules for Gas Chromatography of Chemical Reagents", and the additives of the electrolyte are qualitatively and quantitatively analyzed by gas chromatography.

[0237] 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.

[0238] 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, reduces side reactions between the electrolyte and the electrode surface, and improves the cycle life of the battery cell.

[0239] 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.

[0240] 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 and the phosphate additive is 0.1%-0.5%. This can form a stable interface film on the electrode surface, reduce side reactions between the electrolyte and the electrode surface, and improve the cycle life of the battery cell.

[0241] 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. Thus, these 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 in the battery cell under high temperature conditions.

[0242] 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.

[0243] 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.

[0244] 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 mass proportion of the lithium salt additive is 0.1%-0.5%.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] According to some embodiments of the present application, the conductivity of the electrolyte at room temperature may be 10 mS / cm-13.5 mS / cm, thereby increasing the lithium ion migration rate and improving the fast charging performance of the battery cell.

[0249] 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, 13.5 mS / cm, etc., or can be a range consisting of any of the above values.

[0250] 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.

[0251] 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.

[0252] 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.

[0253] 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.

[0254] As the electrical equipment, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0255] 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.

[0256] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0257] 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.

[0258] Example 1

[0259] 1. Preparation of positive electrode sheet

[0260] 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.

[0261] 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 current collector and drying it. The thickness is 1μm. The mass content of the positive electrode conductive agent in the positive conductive layer is 46%, and the mass content of the positive electrode binder is 54%.

[0262] 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 97.5:1.5:1.

[0263] 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 0.07% by weight, Ti accounts for 0.06% by weight, Nb accounts for 0.03% by weight, and Mg accounts for 0.05% by weight. The average particle size of the primary particles of the lithium iron phosphate material is 400nm.

[0264] The single-side coating weight of the positive electrode active material layer is 0.3g / 1540.25mm 2 .

[0265] The compacted density of the positive electrode active material layer is 2.54 g / cm 3 .

[0266] In the height direction of the battery cell, the size of the second inorganic coating layer is 2 mm, the size of the first inorganic coating layer is 3 mm, and the size of the electrode tab is 30 mm.

[0267] 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.

[0268] 2. Preparation of negative electrode sheet

[0269] 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.

[0270] 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 29%, the mass content of the negative electrode binder in the negative electrode conductive layer is 66%, and the mass content of the thickener in the negative electrode conductive layer is 5%.

[0271] 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.

[0272] The negative electrode active material layer includes a negative electrode active material with a mass ratio of 96.8:0.5:1.8:0.9, 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, the mass content of carbon element is 3.5%, and the Dv50 of the graphite particles is 10.2 μm.

[0273] The dimension of the negative electrode active material layer along the height direction of the battery cell is 91 mm, and the dimension of the negative electrode active material layer along the width direction of the battery cell is 203 mm.

[0274] The single-side coating weight of the negative electrode active material layer is 0.137 mg / 1540.25 mm 2 .

[0275] The compaction density of the negative electrode active material layer is 1.43 g / cm 3 .

[0276] 3. Isolation film

[0277] The separator includes a base film and coatings provided on both sides of the base film. The base film includes a 7μm polyethylene film layer with a porosity of 42%. The separator has a size of 99mm in the height direction of the battery cell.

[0278] The coating comprises a first coating and a second coating, wherein the first coating comprises polyacrylate and aluminum oxide particles dispersed on the polyacrylate, the first coating being a film layer formed by applying the first slurry to one side of the base film, having a thickness of 2 μm and an average particle size of the aluminum oxide particles of 0.8 μm; wherein the first slurry comprises aluminum oxide particles and a binder polyacrylate;

[0279] The second coating is a composite particle formed by polyacrylate and polyvinylidene fluoride (PVDF) particles dispersed on the polyacrylate. The second functional layer is a film layer formed by coating the second slurry on the other side of the base film. The thickness is 1μm, and the average particle size of the PVDF particles is 200nm. The second slurry includes polyacrylate and PVDF particles.

[0280] The height dimension of the separator in the battery cell direction is 95 mm, and that of OH3 is 4 mm.

[0281] 4. Preparation of Electrolyte

[0282] 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.

[0283] 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.

[0284] 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%.

[0285] 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.

[0286] 5 Preparation of battery cells

[0287] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to provide isolation, to obtain a laminated electrode assembly. The electrode assembly is placed in a housing, on which positive and negative terminals are provided. After baking, the electrolyte is injected, and the battery is vacuum packaged, allowed to stand, formed, and shaped to obtain a battery cell. Figure 1 Along the height direction of the battery cell, the size of the battery cell is 104.8 mm, along the width direction of the battery cell, the size of the battery cell is 208.3 mm, and along the thickness direction of the battery cell, the size of the battery cell is 50.5 mm.

[0288] Performance Testing

[0289] 1. Energy density

[0290] The battery cell was placed at 25°C, 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; discharged at a constant current of 0.33C to 2.0V, and the discharge capacity A0 at this time was recorded in Ah; the length, width, and height of the battery cell were measured with a caliper, and the volume V0 of the battery cell was calculated in L; the volume energy density of the battery cell, VED, was calculated as (A0 × discharge platform voltage) / V0 in Wh / L.

[0291] 2. High temperature storage life

[0292] At 25°C, charge the battery cell at a constant current of 0.33C to the cut-off voltage (such as 3.8V), then charge it at a constant voltage to ≤0.05C, then discharge it at a constant current of 0.33C to the cut-off voltage (such as 2.0V), and the discharge capacity is C0; then charge the battery cell at a constant current of 0.33C to the cut-off voltage (such as 3.8V), then charge it at a constant voltage to ≤0.05C, and store it in a temperature box at 45°C. After a certain number of days of storage, take out the battery cell and discharge it at 0.33C to the cut-off voltage. Then charge the battery cell at a constant current of 0.33C to the cut-off voltage (such as 3.8V), then charge it at a constant voltage of ≤0.05C, and then discharge it at a constant current of 0.33C to the cut-off voltage (such as 2.0V), and record the discharge capacity C2. Record the value of C2 / C1×100%. When the value is greater than 80%, continue to store it for 30 days until C2 / C1×100%≤80%. Add the total storage days of the battery cell.

[0293] 3. Cycle performance under fast charging

[0294] Charge from 0% SOC to 10% SOC at 0.5C constant current;

[0295] 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:

[0296] Charge from 10% SOC to 15% SOC at 5.0C constant current;

[0297] Charge from 15% SOC to 20% SOC at 4.6C constant current;

[0298] Charge from 20% SOC to 35% SOC at 4.2C constant current;

[0299] Charge from 35% SOC to 45% SOC at 3.8C constant current;

[0300] Charge from 45% SOC to 50% SOC at 3.6C constant current;

[0301] Charge from 50% SOC to 60% SOC at 3.4C constant current;

[0302] Charge from 60% SOC to 70% SOC at 3.0C constant current;

[0303] Charge from 70% SOC to 75% SOC at 2.8C constant current;

[0304] Charge from 75% SOC to 80% SOC at 2.4C constant current;

[0305] Then charge from 80% SOC to 100% SOC at 0.5C constant current;

[0306] After fully charged, discharge at 1C to 2.5V.

[0307] Repeat the above steps until the capacity decays to 80% SOH of the initial capacity, and count the number of cycles.

[0308] Example 2

[0309] The preparation method of the battery cell is the same as that of Example 1. Along the height direction of the battery cell, the size of the positive electrode active material layer is 87 mm, and the size of the positive electrode active material layer accounts for 83% of the size of the shell. The size of the negative electrode active material layer is 89 mm, and the size of the separator is 93 mm.

[0310] Example 3

[0311] The preparation method of the battery cell is the same as that of Example 1. Along the height direction of the battery cell, the size of the positive electrode active material layer is 92.2 mm, and the size of the positive electrode active material layer accounts for 88% of the size of the shell. The size of the negative electrode active material layer is 94.2 mm, and the size of the isolation membrane is 98.2 mm.

[0312] Comparative Example 1

[0313] The preparation method of the battery cell is the same as that of Example 1. Along the height direction of the battery cell, the size of the positive electrode active material layer is 83.8 mm, and the size of the positive electrode active material layer accounts for 80% of the size of the shell. The size of the negative electrode active material layer is 85.8 mm, and the size of the isolation membrane is 89.8 mm.

[0314] Comparative Example 2

[0315] The preparation method of the battery cell is the same as that of Example 1. Along the height direction of the battery cell, the size of the positive electrode active material layer is 96.4 mm, and the size of the positive electrode active material layer accounts for 92% of the size of the shell. The size of the negative electrode active material layer is 98.4 mm, and the size of the isolation membrane is 102.4 mm.

[0316] The detailed differences and test results of the battery cells in Examples 1 to 3, Comparative Example 1, and Comparative Example 2 are shown in Table 1.

[0317] Table 1

[0318]

[0319] It can be seen from Table 1 that when the sizes of OH1 and OH3 are within the range specified in this application, by adjusting the size of the positive electrode active material layer, the ratio of the size of the positive electrode active material layer to the size of the shell can be adjusted to obtain a battery cell with higher energy density and better high-temperature storage life.

[0320] If the ratio of the size of the positive electrode active material layer to the size of the shell is too small, the utilization rate of the positive electrode active material in the space inside the shell is low, which will reduce the energy density of the battery cell.

[0321] If the size of the positive electrode active material layer accounts for too large a proportion of the size of the shell, although the energy density of the battery cell can be improved, the probability of positive and negative electrode overlap will increase after the positive and negative electrodes are misaligned. The overlap of the positive and negative electrodes will cause self-discharge, loss of battery cell capacity, and reduction of high-temperature storage life.

[0322] Comparative Example 3

[0323] The preparation method of the battery cell is the same as that of Example 1, except that, along the height direction of the battery cell, the size of the positive electrode active material layer is 90 mm, the size of the positive electrode active material layer accounts for 85.8% of the size of the shell, and OH1 is 1 mm.

[0324] Example 4

[0325] The preparation method of the battery cell is the same as that of Example 1, except that, along the height direction of the battery cell, the size of the positive electrode active material layer is 89.5 mm, the size of the positive electrode active material layer accounts for 85.4% of the size of the shell, and OH1 is 1.5 mm.

[0326] Example 5

[0327] The preparation method of the battery cell is the same as that of Example 1, except that, along the height direction of the battery cell, the size of the positive electrode active material layer is 87.7 mm, the size of the positive electrode active material layer accounts for 83.6% of the size of the shell, and OH1 is 3.3 mm.

[0328] Comparative Example 4

[0329] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode active material layer along the height direction of the battery cell is 87 mm, the size of the positive electrode active material layer accounts for 83% of the size of the shell, and OH1 is 4 mm.

[0330] The detailed differences and test results of the battery cells in Example 4, Example 5, Comparative Example 3, and Comparative Example 4 are shown in Table 2.

[0331] Table 2

[0332]

[0333] It can be seen from Table 2 that when the ratio of the size of the positive electrode active material layer to the size of the shell and the size of OH3 are within the range specified in this application, the size of OH1 can be adjusted by adjusting the size of the positive electrode active material layer. By making OH1 within the range specified in this application, a battery cell with both higher energy density and better high-temperature storage life can be obtained.

[0334] If OH1 is too small, the probability of overlap after the positive and negative poles are misaligned increases, which will cause self-discharge and loss of capacity, thereby reducing the high-temperature storage life of the battery cell.

[0335] If OH1 is too large, the size of the positive electrode active material layer is reduced, resulting in a loss of energy density of the battery cell.

[0336] Comparative Example 5

[0337] The preparation method of the battery cell is the same as that of Example 1, except that, along the height direction of the battery cell, the size of the positive electrode active material layer is 92 mm, the size of the positive electrode active material layer accounts for 87.8% of the shell size, the size of the negative electrode active material layer is 94 mm, the size of the isolation membrane is 96 mm, and the OH3 is 2 mm.

[0338] Example 6

[0339] The preparation method of the battery cell is the same as that of Example 1, except that, along the height direction of the battery cell, the size of the positive electrode active material layer is 91 mm, the size of the positive electrode active material layer accounts for 86.8% of the shell size, the size of the negative electrode active material layer is 93 mm, the size of the isolation membrane is 96 mm, and OH3 is 3 mm.

[0340] Example 7

[0341] The preparation method of the battery cell is the same as that of Example 1, except that, along the height direction of the battery cell, the size of the positive electrode active material layer is 87 mm, the size of the positive electrode active material layer accounts for 83% of the shell size, the size of the negative electrode active material layer is 89 mm, the size of the isolation membrane is 99 mm, and the OH3 is 10 mm.

[0342] Comparative Example 6

[0343] The preparation method of the battery cell is the same as that of Example 1, except that, along the height direction of the battery cell, the size of the positive electrode active material layer is 85 mm, the size of the positive electrode active material layer accounts for 81% of the shell size, the size of the negative electrode active material layer is 87 mm, the size of the isolation membrane is 99 mm, and the OH3 is 12 mm.

[0344] The detailed differences and test results of the battery cells in Example 1, Comparative Example 5, Comparative Example 6, Example 7, and Example 8 are shown in Table 3.

[0345] Table 3

[0346]

[0347] As shown in Table 3, when the ratio of the positive electrode active material layer to the housing size and the size of OH1 are within the range specified in this application, the size of OH3 can be adjusted by adjusting the size of the negative electrode active material layer. By ensuring that OH3 is within the range specified in this application, a battery cell with both high energy density and excellent high-temperature storage life can be obtained.

[0348] If OH3 is too small, although the energy density of the battery cell is high, the difference between the size of the isolation membrane and the size of the negative electrode active material layer is small, which increases the probability of overlap between the positive and negative electrodes. After the positive and negative electrodes are overlapped, self-discharge occurs, the available capacity gradually decreases, and the high-temperature storage life of the battery cell is reduced.

[0349] If OH3 is too large, although it can reduce the probability of positive and negative electrode overlap and increase the high-temperature storage life of the battery cell, it will reduce the utilization rate of the active material in the shell space and lose the energy density of the battery cell.

[0350] Example 8

[0351] The preparation method of the battery cell is the same as that of Example 1, except that, along the width direction of the battery cell, the size of the positive electrode active material layer is 193.7 mm, the size of the positive electrode active material layer accounts for 93% of the shell size, and the size of the negative electrode active material layer is 196.2 mm.

[0352] Example 9

[0353] The preparation method of the battery cell is the same as that of Example 1, except that, along the width direction of the battery cell, the size of the positive electrode active material layer is 197.9 mm, the size of the positive electrode active material layer accounts for 95% of the shell size, and the size of the negative electrode active material layer is 200.4 mm.

[0354] Example 10

[0355] The preparation method of the battery cell is the same as that of Example 1, except that, along the width direction of the battery cell, the size of the positive electrode active material layer is 203.1 mm, the size of the positive electrode active material layer accounts for 97.5% of the shell size, and the size of the negative electrode active material layer is 205.6 mm.

[0356] Example 11

[0357] The preparation method of the battery cell is the same as that of Example 1, except that, along the width direction of the battery cell, the size of the positive electrode active material layer is 204.1 mm, the size of the positive electrode active material layer accounts for 98% of the shell size, and the size of the negative electrode active material layer is 206.6 mm.

[0358] The detailed differences and test results of the battery cells in Examples 1, 8, and 11 are shown in Table 4.

[0359] Table 4

[0360]

[0361] It can be seen from Table 4 that when the ratio of the size of the positive electrode active material layer to the size of the shell, and the sizes of OH1 and OH3 are within the range specified in this application, the energy density of the battery cell can be further improved by adjusting the ratio of the size of the positive electrode active material layer to the size of the shell in the width direction of the battery cell. By making the ratio of the size of the positive electrode active material layer to the size of the shell within the protection scope of this application, the utilization rate of the active material in the space inside the shell can be improved, and OH2 can be made within a suitable range, thereby reducing the probability of overlap between the positive and negative electrodes and improving the high-temperature storage performance of the battery cell.

[0362] Example 12

[0363] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode active material layer along the width direction of the battery cell is 202 mm, the ratio of the positive electrode active material layer size to the shell size is 97%, and OH2 is 1 mm.

[0364] Example 13

[0365] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode active material layer along the width direction of the battery cell is 201.5 mm, the ratio of the positive electrode active material layer size to the shell size is 96.7%, and OH2 is 1.5 mm.

[0366] Example 14

[0367] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode active material layer along the width direction of the battery cell is 199.5 mm, the ratio of the positive electrode active material layer size to the shell size is 95.8%, and OH2 is 3.5 mm.

[0368] Example 15

[0369] The preparation method of the battery cell is the same as that of Example 1, except that the size of the positive electrode active material layer along the width direction of the battery cell is 198 mm, the ratio of the positive electrode active material layer size to the shell size is 95.1%, and OH2 is 5 mm.

[0370] The detailed differences and test results of the battery cells in Examples 1 and 12 to 15 are shown in Table 5.

[0371] Table 5

[0372]

[0373] It can be seen from Table 5 that when the ratio of the size of the positive electrode active material layer to the size of the shell, and the sizes of OH1 and OH3 are within the range specified in this application, by further controlling OH2 within the protection scope of this application, the utilization rate of the active material in the internal space of the shell can be improved while reducing the probability of overlap between the positive and negative electrodes, reducing the reduction in capacity due to self-discharge, and obtaining a battery cell with both higher energy density and better high-temperature storage life.

[0374] Example 16

[0375] 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 5%, and the mass proportion of the carbonate solvent is 75.5%.

[0376] Example 17

[0377] 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 solvent is 70.5%.

[0378] Example 18

[0379] 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 solvent is 45.5%.

[0380] The detailed differences and test results of the battery cells in Example 1 and Example 16 to Example 18 are shown in Table 6.

[0381] Table 6

[0382]

[0383] It can be seen from Table 6 that when the ratio of the size of the positive electrode active material layer to the size of the shell and the sizes of OH1 and OH3 are within the range specified in this application, by controlling the mass proportion of the carboxylic acid ester solvent in the electrolyte so that it is within the protection scope of this application, the ionic conductivity of the electrolyte can be improved, while reducing the gas production of the battery cell under high temperature conditions and improving the cycle performance of the battery cell under fast charging conditions.

[0384] Example 19

[0385] 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 LiPF6 is 7.5%, the mass proportion of LiFSI is 7.5%, and the mass ratio of LiPF6 to LiFSI is 1:1.

[0386] Example 20

[0387] 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 LiPF6 is 8.18%, the mass proportion of LiFSI is 6.82%, and the mass ratio of LiPF6 to LiFSI is 1.2:1.

[0388] Example 21

[0389] 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 LiPF6 is 11.25%, the mass proportion of LiFSI is 3.75%, and the mass ratio of LiPF6 to LiFSI is 3:1.

[0390] Example 22

[0391] 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 LiPF6 is 12%, the mass proportion of LiFSI is 3%, and the mass ratio of LiPF6 to LiFSI is 4:1.

[0392] The detailed differences and test results of the battery cells in Examples 1 and 19 to 22 are shown in Table 7.

[0393] Table 7

[0394]

[0395] It can be seen from Table 7 that when the ratio of the size of the positive electrode active material layer to the size of the shell and the sizes of OH1 and OH3 are within the range specified in this application, by adjusting the content of LiPF6 and LiFSI in the electrolyte, the lithium ion migration rate can be improved due to the higher conductivity of LiFSI, thereby improving the cycle performance of the battery cell under fast charging conditions.

[0396] 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 laminated electrode assembly comprises a laminated electrode assembly and a housing, wherein the housing defines a housing cavity, the laminated electrode assembly is disposed in the housing cavity, and the laminated electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet; The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes a lithium-containing phosphate. The positive electrode current collector includes a coating portion and a tab portion. The positive electrode active material layer is disposed on at least one surface of the coating portion, and the tab portion extends from the coating portion. Along the height direction of the battery cell, the size of the positive electrode active material layer accounts for 83%-88% of the size of the housing. The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. Along the height direction of the battery cell, the size of the negative electrode active material layer is larger than the size of the positive electrode active material layer. The difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH1, and satisfies 1.5 mm ≤ OH1 ≤ 3.3 mm. Along the height direction of the battery cell, the size of the separator is larger than the size of the negative electrode active material layer, the difference between the size of the separator and the size of the negative electrode active material layer is OH3, and 3mm≤OH3≤10mm is satisfied. Along the width direction of the battery cell, the size of the negative electrode active material layer is larger than that of the positive electrode active material layer, and the difference between the size of the negative electrode active material layer and the size of the positive electrode active material layer is OH2, 1.5mm≤OH2≤3.5mm.

2. The battery cell according to claim 1, wherein: OH2>OH1.

3. The battery cell according to claim 1, wherein: Along the width direction of the battery cell, the size of the positive electrode active material layer accounts for 95% to 97.5% of the size of the shell.

4. The battery cell according to claim 1, wherein: 1.5mm≤OH1≤2.5mm.

5. The battery cell according to claim 1, characterized in that The isolation film includes a base film and a coating layer provided on at least one side of the base film. The coating layer includes a binder and fluorine-containing organic particles. The total thickness of the coating layer is 3 μm-7 μm.

6. The battery cell according to claim 5, characterized in that The fluorine-containing organic particles include polyvinylidene fluoride particles, and the average particle size of the polyvinylidene fluoride particles is 10 nm-100 nm.

7. The battery cell according to claim 5 or 6, characterized in that: The coating comprises: a first coating layer, the first coating layer being disposed on at least one side of the base film, the first coating layer comprising a first binder and first inorganic particles; The second coating layer is arranged on a side of the first coating layer away from the base film, or the second coating layer is arranged on a side of the base film, and the second coating layer includes a second binder and the fluorine-containing organic particles.

8. The battery cell according to claim 7, characterized in that The thickness of the first coating layer disposed on one side of the base film is 1 μm to 3 μm.

9. The battery cell according to claim 7, characterized in that The second coating layer further includes composite particles. The composite particles include second inorganic particles and a non-fluoropolymer. The second inorganic particles are attached to the surface of the non-fluoropolymer and / or dispersed inside the non-fluoropolymer.

10. The battery cell according to claim 9, characterized in that: The first inorganic particles and the second inorganic particles independently include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide.

11. The battery cell according to claim 9, characterized in that The average particle diameter of the first inorganic particles and the second inorganic particles is 5 nm to 200 nm.

12. The battery cell according to claim 9, characterized in that The average particle diameter of the first inorganic particles and the second inorganic particles is 10 nm to 100 nm.

13. The battery cell according to claim 9, characterized in that The average particle size of the first inorganic particles and the second inorganic particles is 10 nm to 20 nm.

14. The battery cell according to claim 9, characterized in that The non-fluorine polymer includes an acrylic copolymer.

15. The battery cell according to claim 14, characterized in that The acrylic ester copolymer includes an acrylic ester-acrylonitrile-acrylamide-propylene copolymer.

16. The battery cell according to claim 5, characterized in that The base film includes at least one of a polyethylene base film and a polypropylene base film, and the thickness of the base film is 5 μm-9 μm.

17. The battery cell according to claim 1, characterized in that The porosity of the isolation membrane is 40%-55%.

18. The battery cell according to claim 1, characterized in that Along the height direction of the battery cell, the tab portion includes a hollow foil area and an inorganic coating area, wherein the inorganic coating area is located between the coating portion and the hollow foil area. The empty foil area is used to electrically connect to the electrode terminal. The inorganic coating area includes a first inorganic coating, which includes first inorganic particles and a third adhesive. Along the height direction of the battery cell, the size of the first inorganic coating accounts for 1 / 15-1 / 4 of the size of the pole ear.

19. The battery cell according to claim 18, characterized in that Along the height direction of the battery cell, the size of the inorganic coating area of ​​the pole lug portion is 2 mm-7.5 mm, and the size of the pole lug portion is 25 mm-45 mm.

20. The battery cell according to claim 18, characterized in that Along the height direction of the battery cell, the 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 of ​​the pole ear portion, and is connected to the inorganic coating area and the active area. The size of the inactive area is 1.5mm-3mm.

21. The battery cell according to claim 20, characterized in that The inactive area includes a second inorganic coating layer, and the second inorganic coating layer includes the first inorganic particles and the third binder.

22. The battery cell according to claim 20 or 21, characterized in that: Along the height direction of the battery cell, 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.

23. The battery cell according to claim 1, characterized in that 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 .

24. The battery cell according to claim 1, characterized in that The coating weight of the positive electrode active material layer on one side is 0.29 g / 1540.25 mm 2 -0.31g / 1540.25mm 2 .

25. 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 .

26. 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 -2.6g / cm 3 .

27. 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 -0.18g / 1540.25mm 2 .

28. 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 -0.16g / 1540.25mm 2 .

29. 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 .

30. The battery cell according to claim 1, wherein The compaction density of the negative electrode active material layer is 1.35 g / cm 3 -1.5g / cm 3 .

31. The battery cell according to claim 1, characterized in that The negative electrode active material layer includes: a first negative electrode active material layer, the first negative electrode active material layer being disposed on at least one side of the negative electrode current collector, the first negative electrode active material layer comprising a first negative electrode active material; a second negative electrode active material layer, the second negative electrode active material layer being disposed on a side of the first negative electrode active material layer away from the negative electrode current collector, the second negative electrode active material layer comprising a second negative electrode active material; The first negative electrode active material and the second negative electrode active material each independently include graphite, and an average particle size of the graphite in the first negative electrode active material layer is larger than an average particle size of the graphite in the second negative electrode active material layer.

32. The battery cell according to claim 31, characterized in that The thickness of the second negative electrode active material layer accounts for 30% to 70% of the thickness of the negative electrode active material layer.

33. The battery cell according to claim 31, characterized in that The average particle size of the graphite in the first negative electrode active material layer is 7 μm to 18 μm, and the average particle size of the graphite in the second negative electrode active material layer is 6 μm to 10 μm.

34. The battery cell according to claim 31, characterized in that The graphite includes secondary particles having amorphous carbon on at least a portion of the surface of the secondary particles.

35. The battery cell according to claim 31, characterized in that The volume average particle size Dv50 of the graphite is 7 μm-15 μm.

36. The battery cell according to claim 31, characterized in that The graphitization degree of the graphite is 90%-94%.

37. The battery cell according to claim 1, characterized in that The negative electrode active material layer further includes a silicon-based material. Based on the total mass of the negative electrode active material layer, the mass proportion of silicon element is 0.5%-10%.

38. The battery cell according to claim 37, characterized in that The silicon-based material includes a silicon-carbon material.

39. The battery cell according to claim 1, wherein: 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.

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

41. The battery cell according to claim 40, characterized in that The lithium iron phosphate includes doping elements, and the doping elements include one or more of Mg, V, Ti, and Nb.

42. The battery cell according to claim 41, 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%.

43. 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.

44. The battery cell according to claim 43, characterized in that Based on the total mass of the electrolyte, the mass proportion of the carbonate solvent is 20%-75%.

45. The battery cell according to claim 43, characterized in that Based on the total mass of the electrolyte, the mass proportion of the carboxylate solvent is 10%-35%.

46. ​​The battery cell according to claim 43, characterized in that The carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

47. The battery cell according to claim 43, 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.

48. The battery cell according to claim 43, characterized in that The carboxylate solvent includes one or more of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

49. The battery cell according to claim 43, 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%.

50. The battery cell according to claim 49, characterized in that The mass ratio of the lithium hexafluorophosphate to the fluorinated lithium sulfonyl imide is (1.2-3):

1.

51. The battery cell according to claim 49, characterized in that Based on the total mass of the electrolyte, the mass of the lithium hexafluorophosphate accounts for 4%-14%.

52. The battery cell according to claim 50, characterized in that Based on the total mass of the electrolyte, the mass proportion of the fluorinated lithium sulfonyl imide is 4%-8%.

53. The battery cell according to claim 43, 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.

54. The battery cell according to claim 53, characterized in that Based on the total mass of the electrolyte, the mass proportion of the additive is 0.1%-5%.

55. The battery cell according to claim 53, 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%.

56. The battery cell according to claim 53, characterized in that 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%.

57. The battery cell according to claim 53, characterized in that The lithium salt additive includes one or more of lithium difluorophosphate, lithium difluorooxalatoborate, lithium tetrafluoroborate, lithium bis(oxalatoborate), and lithium fluorosulfonate.

58. The battery cell according to claim 53, 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 0.02%-0.5%.

59. The battery cell according to claim 53, 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%.

60. The battery cell according to claim 43, characterized in that The conductivity of the electrolyte is 10 mS / cm-13.5 mS / cm at room temperature.

61. 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.

62. A battery device, characterized in that: The battery device comprises the battery cell according to any one of claims 1 to 61, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

63. An electrical device, characterized in that: The battery cell according to any one of claims 1 to 61 or the battery device according to claim 62 is included, and the battery cell or the battery device provides electrical energy for the electrical device.

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