Battery monomer, battery device and electric equipment

Abstract

The invention discloses a battery monomer, a battery device and electric equipment, and belongs to the technical field of batteries. The battery monomer comprises a positive pole piece, a negative pole piece, electrolyte and a packaging bag, the positive pole piece comprises a positive current collector, a positive film layer and an insulating layer, the positive current collector comprises a positive main body part and a positive tab, the positive main body part comprises a coating area and a transition area, the transition area is located at at least one end of the coating area in the first direction, the positive film layer is arranged on at least one side surface of the coating area, and the insulating layer comprises a first part; the first part is arranged on at least one side surface of the transition area; the negative pole piece comprises a negative pole film layer, the edge of the negative pole film layer exceeds the edge, close to the positive pole lug, of the first part in the first direction, and a chamfer structure is arranged at the joint of the first edge and the second edge of the negative pole piece; and the ionic conductivity of the electrolyte is 8.5 ms / cm to 20 ms / cm, so that the reliability and the cycle performance of the battery monomer can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and more specifically, to a battery cell, a battery device, and an electrical device. Background Art

[0002] The new energy industry is attracting more and more attention. In the new energy industry, battery technology is an important factor in its development.

[0003] The development of battery technology requires consideration of multiple design factors, such as energy density, cycle life, service life, capacity, fast charging performance, and reliability. Providing a battery cell with high reliability and good cycle performance is a pressing technical challenge. Summary of the Invention

[0004] The present application is made in view of the above-mentioned problems, and its object is to provide a battery cell with high reliability and good cycle performance.

[0005] In order to achieve the above objectives, the present application provides a battery cell, a battery device, and an electrical device.

[0006] In a first aspect, a battery cell is provided, comprising: a negative electrode sheet, an electrolyte and a packaging bag, wherein the positive electrode sheet, the negative electrode sheet and the electrolyte are contained in the packaging bag; the positive electrode sheet comprises a positive electrode current collector, a positive electrode film layer and an insulating layer, the positive electrode current collector comprises a positive electrode main body and a positive electrode ear, the positive electrode ear protrudes from the positive electrode main body along a first direction, the positive electrode main body comprises a coating area and a transition area, along the first direction, the transition area is located at at least one end of the coating area, the positive electrode film layer is arranged on at least one side surface of the coating area, the insulating layer comprises a first part, the first A portion is arranged on at least one side surface of the transition zone; the negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one side surface of the negative electrode current collector, and along the first direction, the edge of the negative electrode film layer exceeds the edge of the first portion close to the positive electrode ear; wherein, a chamfer structure is provided at the connection between the first edge and the second edge of the negative electrode plate, the first edge extends along the first direction, and the second edge extends along the second direction, and the first direction and the second direction are perpendicular to the thickness direction of the negative electrode plate; the ionic conductivity of the electrolyte is 8.5ms / cm to 20ms / cm.

[0007] In the embodiment of the present application, by providing a chamfer structure at the connection between the first side and the second side of the negative electrode plate, the risk of the negative electrode plate squeezing the packaging bag, causing damage to the packaging bag, and electrolyte leakage can be reduced; in addition, by providing the edge of the negative electrode film layer beyond the edge of the first part of the insulating layer close to the positive electrode tab, the risk of the positive electrode plate squeezing the packaging bag, causing damage to the packaging bag, and electrolyte leakage can be reduced, and at the same time, there is no need to provide a chamfer structure for the positive electrode plate. By providing the ionic conductivity of the electrolyte to be 8.5ms / cm to 20ms / cm, it is beneficial to improve the transmission speed of lithium ions, thereby compensating for the problem of lithium plating caused by the edge of the negative electrode film layer exceeding the edge of the positive electrode film layer and the edge of the first part of the insulating layer close to the positive electrode tab, and thus helping to improve the cycle performance of the battery cell. Therefore, the embodiment of the present application can take into account both the reliability of the battery cell and the cycle performance of the battery cell.

[0008] In some embodiments, the electrolyte has an ionic conductivity of 12 ms / cm to 16 ms / cm.

[0009] When the ionic conductivity of the electrolyte is greater than or equal to 12ms / cm, it is beneficial to improve the transmission speed of lithium ions, thereby reducing the risk of lithium plating, and the battery cell has better cycle performance; when the ionic conductivity of the electrolyte is less than or equal to 16ms / cm, it is beneficial to reduce gas production in the battery cell, thereby reducing the adverse effect of gas production on cycle performance.

[0010] In some embodiments, along the first direction, a dimension of the first portion is 1 mm to 3 mm.

[0011] When the size of the first part along the first direction is greater than or equal to 1 mm, the insulating layer can effectively block the burrs, which is beneficial to reducing the risk of the burrs of the positive electrode sheet overlapping with the negative electrode sheet or puncturing the isolation membrane, and the battery cell has higher reliability; when the size of the first part along the first direction is less than or equal to 3 mm, it is beneficial to improve the energy density of the battery cell.

[0012] In some embodiments, the insulating layer has an average thickness of 10 μm to 50 μm.

[0013] When the average thickness of the insulating layer is greater than or equal to 10 μm, the insulating layer can effectively block burrs, which is beneficial to reducing the risk of burrs on the positive electrode sheet overlapping with the negative electrode sheet or puncturing the isolation membrane, and the battery cell has higher reliability; when the average thickness of the insulating layer is less than or equal to 50 μm, it is beneficial to improve the energy density of the battery cell.

[0014] In some embodiments, along the first direction, a dimension of the edge of the negative electrode film layer extending beyond a region of the first portion close to the edge of the positive electrode tab is 0.5 mm to 3 mm.

[0015] When the size of the area where the edge of the negative electrode film layer exceeds the edge of the first part close to the edge of the positive electrode tab along the first direction is greater than or equal to 0.5 mm, it is convenient to prepare the chamfered structure, which is beneficial to reducing the complexity of preparing the negative electrode plate; when the size of the area where the edge of the negative electrode film layer exceeds the edge of the first part close to the edge of the positive electrode tab along the first direction is less than or equal to 3 mm, it is beneficial to reduce the risk of lithium plating, thereby helping to improve the cycle performance of the battery cell.

[0016] In some embodiments, along the first direction, the dimensions of the chamfered structure are smaller than the dimensions of the region where the edge of the negative electrode film extends beyond the first portion and is near the edge of the positive electrode tab. This facilitates the fabrication of the chamfered structure and helps reduce the risk of the negative electrode sheet squeezing the packaging bag, causing leakage.

[0017] In some embodiments, the chamfered structure has a dimension along the first direction of 0.5 mm to 1.5 mm. When the dimension along the first direction of the chamfered structure is greater than or equal to 0.5 mm, this helps reduce the risk of the negative electrode sheet squeezing the packaging bag, causing leakage. When the dimension along the first direction of the chamfered structure is less than or equal to 1.5 mm, this helps increase the energy density of the battery cell.

[0018] In some embodiments, a size of the chamfered structure along the second direction is greater than a size of the chamfered structure along the first direction.

[0019] When the sealing position of the packaging bag of the battery cell is parallel to the second direction, the edge of the packaging bag in the second direction is more susceptible to greater pressure than the edge in the first direction. By setting the chamfer structure to have a larger dimension along the second direction than along the first direction, it is beneficial to reduce the risk of the negative electrode sheet squeezing the packaging bag and causing leakage of the packaging bag.

[0020] In some embodiments, a dimension of the chamfered structure along the second direction is 0.5 mm to 3 mm.

[0021] When the size of the chamfered structure along the second direction is greater than or equal to 0.5 mm, it is beneficial to reduce the risk of the negative electrode sheet squeezing the packaging bag and causing leakage of the packaging bag; when the size of the chamfered structure along the second direction is less than or equal to 3 mm, it is convenient for processing the chamfered structure, which is beneficial to reducing the preparation complexity of the chamfered structure.

[0022] In some embodiments, the chamfered structure is a rounded structure, which is helpful in further reducing the risk of the packaging bag being broken when subjected to a force such as squeezing, thereby improving the reliability of the battery cell.

[0023] In some embodiments, the rounded corner structure is a concave structure, which is helpful in further reducing the risk of the packaging bag being broken when subjected to a force such as squeezing, thereby improving the reliability of the battery cell.

[0024] In some embodiments, the insulating layer further includes a second portion, the second portion being connected to the first portion and disposed on at least one side of a portion of the positive electrode tab. This further enhances protection against burrs and improves battery reliability.

[0025] In some embodiments, the negative electrode plate includes a negative electrode tab, and along the first direction, the negative electrode tab and the positive electrode tab are opposite to each other. This structural arrangement is conducive to preparing a battery cell with a larger length direction.

[0026] In some embodiments, the battery cell includes an electrode assembly, which includes the positive electrode sheet and the negative electrode sheet; the packaging bag includes two packaging films, the electrode assembly is located between the two packaging films, and the edges of the two packaging films are connected to each other to form a sealing portion; the battery cell also includes an electrode lead, which passes through between the two packaging films and is electrically connected to the electrode assembly.

[0027] The battery cell of this structure is a soft-pack battery cell. By connecting two packaging films, a closed space can be formed inside the battery cell to accommodate the positive electrode sheet, negative electrode sheet and electrolyte; by electrically connecting the electrode lead to the electrode assembly, it is convenient to draw out the current.

[0028] In some embodiments, the packaging film includes an insulating protective layer, a metal layer, and an insulating connecting layer. The insulating connecting layer is disposed on the surface of the metal layer facing the electrode assembly, while the insulating protective layer is disposed on the surface of the metal layer facing away from the electrode assembly. This seals the electrode assembly and electrolyte for protection while also providing a certain degree of flexibility to cushion the battery cells from compression and vibration.

[0029] In some embodiments, the electrolyte includes a solvent, and the solvent includes at least one of a linear carbonate and a linear carboxylate. The solvent has a relatively low viscosity, and the electrolyte including the solvent has a relatively low viscosity, which facilitates the transport of lithium ions, thereby improving the fast-charging performance of the battery cell.

[0030] In some embodiments, the linear carbonate includes at least one of dimethyl carbonate and ethyl methyl carbonate, and the linear carboxylate includes at least one of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate. These solvents have relatively low viscosities, and the electrolyte containing these solvents has relatively low viscosities, which facilitates the transport of lithium ions and thus improves the fast-charging performance of the battery cells.

[0031] In some embodiments, based on the total mass of the electrolyte, the sum of the mass contents of the linear carbonate and the linear carboxylate is 10% to 90%.

[0032] When the sum of the mass contents of linear carbonates and linear carboxylates is greater than or equal to 10% based on the total mass of the electrolyte, the electrolyte has a lower viscosity, which is conducive to the transmission of lithium ions, and the battery cell has better fast charging performance; when the sum of the mass contents of linear carbonates and linear carboxylates is less than or equal to 90% based on the total mass of the electrolyte, the gas production of linear carbonates and linear carboxylates in the battery cell can be reduced, thereby reducing the risk of the generated gas accumulating between the isolation membrane and the positive electrode sheet and the negative electrode sheet, reducing the risk of lithium plating, and helping to improve the cycle performance of the battery cell.

[0033] In some embodiments, the sum of the mass contents of the linear carbonate and the linear carboxylate is 40% to 80% based on the total mass of the electrolyte. Thus, the sum of the mass contents of the linear carbonate and the linear carboxylate is within a suitable range, allowing the battery cell to achieve both good fast-charging performance and good cycling performance.

[0034] In some embodiments, the solvent further comprises a cyclic carbonate. Cyclic carbonate has a good ability to dissociate lithium ions. The combination of cyclic carbonate with at least one of linear carbonate and linear carboxylate facilitates the transport of lithium ions in the electrolyte, thereby reducing the risk of lithium plating and improving the cycle performance of the battery cell.

[0035] In some embodiments, the ratio of the mass of the electrolyte to the capacity of the battery cell is 2.8 g / Ah to 3.5 g / Ah. In this way, the electrolyte has good wettability on the positive and negative electrode sheets, which is conducive to the transmission of lithium ions, thereby reducing the risk of lithium plating and improving the cycle performance of the battery cell.

[0036] In some embodiments, the ratio of the mass of the electrolyte to the capacity of the battery cell is 3.0 g / Ah to 3.2 g / Ah. Thus, the electrolyte has good wettability with the positive and negative electrode sheets, which is beneficial for the transmission of lithium ions, thereby reducing the risk of lithium plating and improving the cycle performance of the battery cell.

[0037] In some embodiments, the single-side density of the positive electrode sheet is 0.33g / 1540.25mm 2 Up to 0.45g / 1540.25mm 2 .

[0038] The single-side density of the positive electrode sheet is greater than or equal to 0.33g / 1540.25mm 2 In the case of , it is beneficial to improve the energy density of the battery cell; when the single side density of the positive electrode is less than or equal to 0.45g / 1540.25mm 2 Under such circumstances, it is beneficial to the transmission of lithium ions and to improving the fast charging performance of battery cells.

[0039] In some embodiments, the compaction density of the positive electrode sheet is 2.3 g / cm 3 Up to 2.65g / cm 3 .

[0040] The compaction density of the positive electrode is greater than or equal to 2.3g / cm 3 In the case of the battery cell having a higher energy density; the compaction density of the positive electrode sheet is less than or equal to 2.65g / cm 3 In this case, it is convenient for the transmission of lithium ions, which is beneficial to improving the fast charging performance of battery cells.

[0041] In some embodiments, the compaction density of the positive electrode sheet is 2.45 g / cm 3 Up to 2.6g / cm 3 This is beneficial for balancing the energy density and fast charging performance of battery cells.

[0042] In some embodiments, the single-side density of the negative electrode sheet is 0.15g / 1540.25mm 2 Up to 0.22g / 1540.25mm 2 .

[0043] The single-side density of the negative electrode is greater than or equal to 0.15g / 1540.25mm 2 In the case of , it is beneficial to improve the energy density of the battery cell; when the single side density of the negative electrode is less than or equal to 0.22g / 1540.25mm 2 Under such circumstances, it is beneficial to the transmission of lithium ions and to improving the fast charging performance of battery cells.

[0044] In some embodiments, the compaction density of the negative electrode sheet is 1.3 g / cm 3 to 1.52g / cm 3 .

[0045] The compaction density of the negative electrode is greater than or equal to 1.3g / cm3 In the case of the negative electrode, the battery cell has a higher energy density; the compaction density of the negative electrode is less than or equal to 1.52g / cm 3 Under such circumstances, it is convenient for the transmission of lithium ions, which is beneficial to improving the fast charging performance of battery cells.

[0046] In some embodiments, the compaction density of the negative electrode sheet is 1.35 g / cm 3 Up to 1.5g / cm 3 In this way, the negative electrode sheet has a suitable compaction density, which is conducive to taking into account both the energy density and fast charging performance of the battery cell.

[0047] In some embodiments, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate. The lithium-containing phosphate has good structural stability, and the battery cell including the lithium-containing phosphate has good cycle performance.

[0048] In some embodiments, the average longest diameter of the primary particles of the lithium phosphate is 300 nm to 800 nm. In this way, the escape path of lithium ions has an appropriate distance, which is beneficial to improving the power performance of the battery cell.

[0049] In some embodiments, the lithium-containing phosphate includes a lithium-containing phosphate matrix and a carbon coating layer covering at least a portion of the surface of the lithium-containing phosphate matrix. The carbon coating layer is beneficial for improving the conductivity of the lithium-containing phosphate and facilitating the utilization of the capacity of the battery cell.

[0050] In some embodiments, the lithium-phosphate matrix includes lithium iron phosphate, which is doped with at least one of Al, V, and Ti. These doping elements are beneficial for improving the conductivity and other properties of the lithium-phosphate, thereby maximizing the capacity of the battery cell. Furthermore, these doping elements are beneficial for increasing the compaction density of the positive electrode sheet, thereby increasing the energy density of the battery cell.

[0051] In some embodiments, based on the total mass of the lithium-containing phosphate, the mass content of Al is 200 ppm to 2500 ppm, the mass content of V is 300 ppm to 2000 ppm, and the mass content of Ti is 1500 ppm to 3500 ppm. These doping elements help improve the conductivity and other properties of the lithium-containing phosphate, thereby facilitating the utilization of the battery cell's capacity. Furthermore, these doping elements also help increase the compaction density of the positive electrode sheet, thereby improving the energy density of the battery cell.

[0052] In some embodiments, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite, and at least a portion of the surface of the graphite has a coating layer, the coating layer including amorphous carbon. This facilitates rapid embedding of lithium ions into the graphite, thereby improving the fast charging performance of the battery cell.

[0053] In some embodiments, the coating layer has a thickness of 100 nm to 500 nm. Thus, the coating layer has a suitable thickness to facilitate the insertion and transmission of lithium ions, which is beneficial to improving the fast charging performance of the battery cell.

[0054] In some embodiments, the graphite includes secondary particles, which facilitates the transmission of lithium ions and helps improve the fast charging performance of the battery cell.

[0055] In some embodiments, the graphite has a degree of graphitization of 90% to 94%. Having an appropriate degree of graphitization not only helps the graphite have a suitable specific capacity, but also allows the side reactions in the battery cells to be controlled within a suitable range, thereby ensuring a suitable capacity and cycle life for the battery cells.

[0056] In some embodiments, the volume average particle size Dv50 of the graphite is 15 μm to 25 μm. In this way, the particle size of the graphite is within a suitable range, which is beneficial to improving the compaction density of the negative electrode sheet, thereby improving the energy density of the battery cell.

[0057] In some embodiments, the volume average particle size Dv50 of the graphite is 16 μm to 20 μm. In this way, the particle size of the graphite is within a suitable range, which is beneficial to improving the compaction density of the negative electrode sheet, thereby improving the energy density of the battery cell.

[0058] In some embodiments, the electrolyte includes an additive, wherein the additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone. These additives facilitate film formation at the negative electrode, reducing side reactions at the negative electrode, thereby improving the cycle life, kinetics, and other properties of the battery cell.

[0059] In some embodiments, the weight content of the additive is less than or equal to 5% based on the total weight of the electrolyte. The above additive has a suitable weight content, which is beneficial to improving the cycle life, dynamics and other properties of the battery cell.

[0060] In some embodiments, the additive has a mass content of 0.5% to 3% based on the total mass of the electrolyte. The additive has a suitable mass content, which is beneficial for improving the cycle life, dynamics and other properties of the battery cell.

[0061] In a second aspect, a battery device is provided, comprising the battery cell according to the first aspect and any embodiment thereof.

[0062] In some embodiments, the battery device includes: a box body; a plurality of battery cells, the plurality of battery cells are accommodated in the box body, the plurality of battery cells are stacked along a third direction, the rated capacity of each battery cell is greater than or equal to 100Ah, the surface of each battery cell includes a first surface and a second surface, the area of the first surface is greater than the area of the second surface, and the first surfaces of the plurality of battery cells are relatively arranged along the third direction; a thermal management component for adjusting the temperature of the plurality of battery cells, the thermal management component and the second surfaces of the plurality of battery cells are relatively arranged along a fourth direction, and the fourth direction is perpendicular to the third direction.

[0063] In this embodiment, the rated capacity of each battery cell is greater than or equal to 100Ah. A large amount of heat will be generated during the charging and discharging process of the battery cell. By matching the thermal management component with the battery cell, it is beneficial to control the temperature of the battery cell and reduce the risk of excessive temperature of the battery cell.

[0064] In some embodiments, the battery device further includes a fixing adhesive disposed between the thermal management component and the battery cell, the fixing adhesive being used to fix the battery cell to the thermal management component, thereby facilitating the fixation between the battery cell and the thermal management component.

[0065] In some embodiments, the fixing adhesive is directly connected to the packaging bag, which is beneficial for improving the energy density of the battery device.

[0066] In some embodiments, the battery device further includes a housing that houses at least one battery cell, and the fixing adhesive is directly connected to a wall of the housing. The housing facilitates better heat dissipation from the battery cell, thereby reducing the temperature of the battery cell.

[0067] In a third aspect, an electrical device is provided, comprising the battery cell of the first aspect and any embodiment thereof, or the battery device of the second aspect and any embodiment thereof, wherein the battery cell or battery device is used to store or provide electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0069] Figure 1 A schematic diagram of a positive electrode sheet according to an embodiment of the present application; Figure 2 A schematic diagram of a positive electrode sheet from another perspective according to an embodiment of the present application; Figure 3 A schematic diagram of the coordination of the positive electrode sheet and the negative electrode sheet according to an embodiment of the present application; Figure 4 A schematic diagram of a negative electrode sheet according to an embodiment of the present application; Figure 5 A schematic diagram of a negative electrode sheet from another perspective according to an embodiment of the present application; Figure 6 A schematic diagram of a battery cell according to an embodiment of the present application; Figure 7 A schematic diagram of a negative electrode sheet according to another embodiment of the present application; Figure 8 A schematic diagram of a negative electrode sheet according to another embodiment of the present application; Figure 9 A schematic diagram of a battery cell according to an embodiment of the present application; Figure 10 A schematic diagram of a battery device according to an embodiment of the present application; Figure 11 A schematic diagram of the cooperation between a battery cell and a thermal management component according to an embodiment of the present application; Figure 12 A schematic diagram of the cooperation between a battery cell and a thermal management component according to another embodiment of the present application; Figure 13 A schematic diagram of a battery module according to an embodiment of the present application; Figure 14 A schematic diagram of a vehicle according to an embodiment of the present application.

[0070] Reference numerals: 5: Positive electrode sheet; 50: Positive electrode current collector; 501: Positive electrode body; 502: Positive electrode tab; 5011: Coating area; 5012: Transition area; 51: Positive electrode film; 52: Insulating layer; 521: First part; 522: Second part; 6: Negative electrode sheet; 60: Negative electrode current collector; 601: Negative electrode body; 602: Negative electrode tab; 61: Negative electrode film; 611: First edge; 612: Second edge; 62: Chamfered junction Structure; 10: Battery device; 30: Controller; 40: Motor; 11: Housing; 111: First housing portion; 112: Second housing portion; 33: Electrode assembly; 310: Packaging film; 321: Electrode lead; 301: First surface; 302: Second surface; 91: Thermal management component; 92: Fixing glue; 80: Battery module; 801: Housing; 8011: First wall; 8012: Second wall; 8013: Third wall. DETAILED DESCRIPTION

[0071] The embodiments of the battery cells, battery devices, and electrical equipment of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary lengthiness in the following description and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0072] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0073] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0074] 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.

[0075] 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), which means 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), which means 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.

[0076] This application aims to develop a battery cell with high reliability and good cycle performance. In a soft-pack battery cell, the packaging bag of the battery cell is used to contain the positive electrode sheet, negative electrode sheet, electrolyte, etc. During the use and transportation of the battery cell, the packaging bag may be squeezed, impacted, and other impacts, which may cause the packaging bag to rupture, thereby increasing the risk of electrolyte leakage from the packaging bag, which is not conducive to improving the reliability of the battery cell.

[0077] In view of this, the embodiment of the present application provides a battery cell, comprising: a positive electrode sheet, a negative electrode sheet, an electrolyte and a packaging bag for accommodating the positive electrode sheet, the negative electrode sheet and the electrolyte; the positive electrode sheet comprises a positive electrode collector, a positive electrode film layer and an insulating layer, the positive electrode collector comprises a positive electrode body and a positive electrode ear, the positive electrode ear protrudes from the positive electrode body along a first direction, the positive electrode body comprises a coating area and a transition area, along the first direction, the transition area is located at at least one end of the coating area, the positive electrode film layer is arranged on at least one side surface of the coating area, and the insulating layer comprises a first part, the first part is arranged on at least one side surface of the transition zone; the negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one side surface of the negative electrode current collector, along the first direction, the edge of the negative electrode film layer exceeds the edge of the first part close to the positive electrode ear, and a chamfer structure is provided at the connection between the first side and the second side of the negative electrode plate, the first side extends along the first direction, and the second side extends along the second direction, and the first direction and the second direction are perpendicular to the thickness direction of the negative electrode plate; the ionic conductivity of the electrolyte is 8.5ms / cm to 20ms / cm.

[0078] In the embodiment of the present application, by providing a chamfer structure at the connection between the first side and the second side of the negative electrode plate, the risk of the negative electrode plate squeezing the packaging bag, causing damage to the packaging bag, and electrolyte leakage can be reduced; in addition, by providing the edge of the negative electrode film layer along the first direction beyond the edge of the first part of the insulating layer close to the positive electrode tab, the risk of the positive electrode plate squeezing the packaging bag, causing damage to the packaging bag, and electrolyte leakage can be reduced. At the same time, there is no need to provide a chamfer structure for the positive electrode plate, which solves the problem of needing to perform chamfer design on both the positive and negative electrode plates at the same time, and reduces the cost of process manufacturing. By setting the ionic conductivity of the electrolyte to 8.5ms / cm to 20ms / cm, it is beneficial to improve the transmission speed of lithium ions, thereby compensating for the "reservoir" effect caused by the edge of the negative electrode film layer exceeding the edge of the positive electrode film layer and the edge of the first part of the insulating layer, and the problem of lithium plating caused by the "reservoir" effect, which is beneficial to improving the cycle performance of the battery cell. Therefore, the embodiment of the present application can take into account both the reliability of the battery cell and the cycle performance of the battery cell.

[0079] The "reservoir" effect is explained as follows. The area where the edge of the negative electrode film layer extends beyond the edge of the positive electrode film layer and the edge of the first portion of the insulating layer can be called the overhang region, and the area where the negative electrode film layer overlaps with the positive electrode film layer can be called the main area of the negative electrode film layer. However, the provision of the overhang region will lead to a "reservoir" effect. The "reservoir" effect also leads to the risk of lithium plating, which is not conducive to improving the reliability of the battery cell. Because the amount of lithium inserted in the overhang region is lower than that in the main area of the negative electrode film layer, there is a potential difference between the overhang region and the main area of the negative electrode film layer. The lithium ions in the main area of the negative electrode film layer spontaneously migrate to the overhang region. As the charge and discharge cycles proceed, the lithium concentration in the overhang region continues to increase. After multiple charge and discharge cycles, when the battery cell is discharged again, all the lithium ions in the main area of the negative electrode film layer are released, while not all the lithium ions in the overhang region are released. The lithium ion concentration in the overhang region is higher than that in the main area of the negative electrode film layer. The lithium ions in the overhang region migrate to the boundary between the negative electrode film layer and the overhang region, resulting in an increase in the lithium ion concentration at the boundary. When charging again, the risk of lithium plating at the boundary increases.

[0080] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0081] The battery cells may be lithium-ion batteries.

[0082] During the charging process of the battery cell, lithium ions are released from the positive electrode active material, moved and embedded in the negative electrode; while during the discharging process, lithium ions are released from the negative electrode, moved and embedded in the positive electrode active material.

[0083] It should be understood that the "embedding" process described in this application refers to the process in which lithium ions are embedded in the positive electrode active material or the negative electrode due to an electrochemical reaction, and the "extraction" process described in this application refers to the process in which lithium ions are extracted from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0084] Typically, a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. Next, the battery cell provided in this application and the various parts of the battery cell are introduced.

[0085] [Battery Cell] An embodiment of the present application provides a battery cell, comprising: a positive electrode sheet, a negative electrode sheet, a packaging bag, and an electrolyte.

[0086] Figure 1 Schematic diagram of a positive electrode sheet according to an embodiment of the present application. Figure 2 This is a schematic diagram of another perspective of the positive electrode sheet of an embodiment of the present application. Figure 1 and Figure 2 As shown, the positive electrode sheet 5 includes a positive electrode current collector 50 , a positive electrode film layer 51 and an insulating layer 52 .

[0087] The positive electrode current collector 50 includes a positive electrode main body 501 and a positive electrode tab 502. The positive electrode tab 502 protrudes from the positive electrode main body 501 along a first direction. Figure 1 and Figure 2 The x direction in .

[0088] The positive electrode body 501 includes a coating region 5011 and a transition region 5012. Along a first direction, the transition region 5012 is located at at least one end of the coating region 5011. The positive electrode film 51 is disposed on at least one side of the coating region 5011. The insulating layer 52 includes a first portion 521 disposed on at least one side of the transition region 5012.

[0089] As an example, along the first direction, transition regions 5012 are provided at both ends of the coating region 5011 , and an insulating layer 52 is provided on at least one surface of the transition region 5012 .

[0090] As another example, along the first direction, only one end of the coating region 5011 close to the positive electrode tab 502 is provided with a transition region 5012 , and at least one side surface of the transition region 5012 is provided with an insulating layer 52 .

[0091] Figure 3 This is a schematic diagram of the coordination of the positive electrode sheet and the negative electrode sheet according to an embodiment of the present application. Figure 4 Schematic diagram of a negative electrode sheet according to an embodiment of the present application. Figure 5 This is a schematic diagram of another perspective of the negative electrode sheet of an embodiment of the present application. Figures 3 to 5 As shown, the negative electrode plate 6 includes a negative electrode current collector 60 and a negative electrode film layer 61 arranged on at least one side surface of the negative electrode current collector 60. Along the first direction, the edge of the negative electrode film layer 61 exceeds the edge of the first part 521 close to the positive electrode ear. A chamfer structure 62 is provided at the connection between the first side 611 and the second side 612 of the negative electrode plate 6. The first side 611 extends along the first direction and the second side 612 extends along the second direction. The second direction and the first direction are both perpendicular to the thickness direction of the negative electrode plate 6.

[0092] The first direction and the second direction are different. As an example, the first direction is perpendicular to the second direction. As another example, the angle between the first direction and the second direction is greater than 0° and less than 90°.

[0093] As an example, only along the first direction, the edge of the negative electrode film layer 61 exceeds the edge of the first portion 521 .

[0094] As another example, along the first direction and the second direction, the edge of the negative electrode film layer 61 exceeds the edge of the first portion 521. The second direction can be Figure 3 y direction in .

[0095] The edge of the negative electrode film layer 61 exceeds the edge of the first portion 521 . This can be understood as, on the xoy plane, the projection of the negative electrode film layer 61 covers and exceeds the projection of the first portion 521 .

[0096] As an example, the negative electrode plate includes two first edges 611 and two second edges 612 , the two first edges 611 are arranged opposite to each other along the second direction, the two second edges 612 are arranged opposite to each other along the first direction, and the first edges 611 and the second edges 612 are connected.

[0097] A chamfer structure 62 is provided at the connection between the first side 611 and the second side 612, wherein the chamfer structure 62 can be a rounded chamfer, a right-angle chamfer, or a compound chamfer, wherein the compound chamfer can be a chamfer combining an arc and a straight line.

[0098] Figure 6 This is a schematic diagram of a battery cell according to an embodiment of the present application. Figure 6 As shown, the battery cell 3 includes a packaging bag 31 , in which the positive electrode sheet 5 , the negative electrode sheet 6 and the electrolyte are contained.

[0099] The packaging bag 31 can be made of a flexible material, such as an aluminum-plastic film. When subjected to a force (e.g., compression), the packaging bag 31 ruptures and contacts the negative electrode sheet, increasing the risk of the packaging bag rupturing due to the corners of the negative electrode sheet. Providing a chamfered structure 62 at the junction of the first edge 611 and the second edge 612 of the negative electrode sheet 6 reduces the risk of interference between the negative electrode sheet and the packaging bag. This reduces the risk of the negative electrode sheet 6 squeezing the packaging bag, causing damage to the packaging bag and electrolyte leakage, thereby improving the reliability of the battery cell.

[0100] Arranging the edge of the negative electrode film layer 61 to extend beyond the edge of the first portion 521 of the insulating layer 52 near the positive electrode tab can reduce the risk of the positive electrode sheet 5 squeezing the packaging bag, causing damage to the packaging bag and electrolyte leakage. It also eliminates the need to provide a chamfered structure on the positive electrode sheet 5, thereby reducing the complexity of battery cell production while maintaining the reliability of the battery cell. In addition, because the first portion 521 is closer to the edge of the positive electrode sheet than the positive electrode film layer 51 along the first direction, the edge of the negative electrode film layer 61 will extend beyond the edge of the first portion 521 and also beyond the edge of the positive electrode film layer 51. This allows for more space in the negative electrode sheet to accommodate lithium ions released from the positive electrode sheet, which helps reduce the risk of lithium plating.

[0101] The ionic conductivity of the electrolyte is 8.5 ms / cm to 20 ms / cm, for example, 8.5 ms / cm, 9 ms / cm, 9.5 ms / cm, 10 ms / cm, 11 ms / cm, 12 ms / cm, 12.5 ms / cm, 13 ms / cm, 14 ms / cm, 15 ms / cm, 15.5 ms / cm, 16 ms / cm, 17 ms / cm, 18 ms / cm, 19 ms / cm, 20 ms / cm or any value within the above range.

[0102] Although the edge of the negative electrode film layer 61 extends beyond the edge of the first portion 521 of the insulating layer 52 near the positive electrode tab, which is beneficial for reducing the risk of lithium plating, as the battery cell is charged and discharged, due to the influence of the "reservoir" effect (the explanation of the "reservoir" effect can be found above and will not be repeated here), there is a risk of lithium plating at the boundary between the area where the edge of the negative electrode film layer 61 extends beyond the edge of the first portion 521 and the area where the negative electrode film layer 61 overlaps with the positive electrode film layer 51, which is not conducive to further improving the cycle performance of the battery cell. By setting the ionic conductivity of the electrolyte to 8.5ms / cm to 20ms / cm, it is beneficial to increase the transmission speed of lithium ions, thereby compensating for the problem of lithium plating caused by the edge of the negative electrode film layer 61 extending beyond the edge of the positive electrode film layer 51 and the edge of the first portion 521 of the insulating layer 52, thereby improving the cycle performance of the battery cell.

[0103] In the embodiment of the present application, the ionic conductivity of the electrolyte can be measured in the following manner.

[0104] For example, after disassembling the battery cell to obtain the electrolyte, the ionic conductivity of the electrolyte to be tested is then tested using a conductivity meter in accordance with HG / T 4067-2015: approximately 100 ml of the sample to be tested is taken into a dry, clean, corrosion-resistant sample bottle, and sealed in a constant temperature water bath at 25±0.5°C. When the temperature of the sample to be tested is constant, the sample bottle cap is replaced with a rubber stopper with an electrode inserted. When the temperature is within the range of 25±0.5°C, the data is read, which is the ionic conductivity of the sample to be tested.

[0105] In the embodiment of the present application, by providing a chamfer structure 62 at the connection between the first side 611 and the second side 612 of the negative electrode plate 6, the risk of the negative electrode plate 6 squeezing the packaging bag, causing damage to the packaging bag, and electrolyte leakage can be reduced. In addition, by providing the edge of the negative electrode film layer 61 along the first direction beyond the edge of the first portion 521 of the insulating layer 52 close to the positive electrode tab, the risk of the positive electrode plate 5 squeezing the packaging bag, causing damage to the packaging bag, and electrolyte leakage can be reduced, while there is no need to provide a chamfer structure 62 on the positive electrode plate 5. By setting the ionic conductivity of the electrolyte to 8.5ms / cm to 20ms / cm, it is beneficial to improve the transmission speed of lithium ions, thereby compensating for the problem of lithium plating caused by the edge of the negative electrode film layer 61 exceeding the edge of the positive electrode film layer 51 and the edge of the first portion 521 of the insulating layer 52, and thus helping to improve the cycle performance of the battery cell. Therefore, the embodiment of the present application can take into account both the reliability and cycle performance of the battery cell.

[0106] In some embodiments, the electrolyte has an ionic conductivity of 12 ms / cm to 16 ms / cm.

[0107] When the ionic conductivity of the electrolyte is greater than or equal to 12ms / cm, it is beneficial to improve the transmission speed of lithium ions, thereby reducing the risk of lithium plating, and the battery cell has better cycle performance; when the ionic conductivity of the electrolyte is less than or equal to 16ms / cm, it is beneficial to reduce the gas production of the battery cell, thereby reducing the adverse effect of gas production on cycle performance.

[0108] In some embodiments, along the first direction, the first portion 521 has a size of 1 mm to 3 mm.

[0109] Along the first direction, a dimension D1 of the first portion 521 may be 1 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3 mm, or any value within the above range.

[0110] The size of the first portion 521 along the first direction may be an average size. For example, the lengths of the first portion 521 at multiple locations in the first direction are tested, and then the average value is taken as D1.

[0111] As an example, the first portion 521 has a rectangular shape.

[0112] During the preparation of positive electrode sheets, for example, during the preparation of positive electrode tabs by cutting or during the cutting of a large positive electrode sheet into two sheets, burrs are often generated. The provision of the insulating layer 52 can play a certain role in blocking burrs, for example, reducing the risk of burrs overlapping the negative electrode sheet and reducing the risk of burrs puncturing the separator.

[0113] When the size of the first part 521 along the first direction is greater than or equal to 1 mm, the insulating layer 52 can effectively block the burrs, which is beneficial to reducing the risk of the burrs of the positive electrode plate 5 overlapping with the negative electrode plate 6 or puncturing the isolation membrane, and the battery cell has higher reliability; when the size of the first part 521 along the first direction is less than or equal to 3 mm, it is beneficial to improve the energy density of the battery cell.

[0114] In some embodiments, the average thickness of the insulating layer 52 is 10 μm to 50 μm.

[0115] The average thickness of the insulating layer 52 is the thickness on one side.

[0116] The average thickness D2 of the insulating layer 52 may be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any value within the above range.

[0117] As an example, the thickness of the insulating layer at multiple positions (for example, 10 positions) is measured along the first direction using a scanning electron microscope (SEM), and the average value of the multiple thicknesses is taken as the average thickness D2 of the insulating layer.

[0118] When the average thickness of the insulating layer 52 is greater than or equal to 10 μm, the insulating layer 52 can effectively block burrs, which is beneficial to reducing the risk of burrs on the positive electrode plate 5 overlapping with the negative electrode plate 6 or puncturing the isolation membrane, and the battery cell has higher reliability; when the average thickness of the insulating layer 52 is less than or equal to 50 μm, it is beneficial to improve the energy density of the battery cell.

[0119] As an example, the insulating layer 52 has the same or almost the same thickness at various locations.

[0120] As another example, there is a partially fused region between the insulating layer 52 and the positive electrode film layer 51. This fused region may be caused by the flow of the slurry during the coating process of the positive electrode film layer slurry and the insulating layer slurry. In this case, the average thickness of the insulating layer 52 refers to the average thickness of the non-fused region.

[0121] As another example, there is an overlapping area between the insulating layer 52 and the positive electrode film layer 51, wherein in the overlapping area, the insulating layer 52 is located on the surface of the positive electrode film layer 51. In this case, the average thickness of the insulating layer 52 refers to the average thickness of the non-overlapping area.

[0122] As another example, there is a gap between the insulating layer 52 and the positive electrode film layer 51. That is, there is an area on the positive electrode body that is not coated with either the insulating layer or the positive electrode film layer.

[0123] In some embodiments, there may be both an overlapping region and a gap between the insulating layer 52 and the positive electrode film layer 51. For example, along one end of the first direction, there is an overlapping region between the insulating layer 52 and the positive electrode film layer 51; along the other end of the first direction, there is a gap between the insulating layer 52 and the positive electrode film layer 51.

[0124] In some embodiments, along the first direction, the edge of the negative electrode film layer 61 extends beyond the edge of the first portion 521 near the positive electrode tab by 0.5 mm to 3 mm.

[0125] Along the first direction, the dimension H of the area where the edge of the negative electrode film layer 61 extends beyond the edge of the first part 521 close to the positive electrode tab can be 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm, 3mm or any value within the above range.

[0126] When the size of the area where the edge of the negative electrode film layer 61 exceeds the edge of the first part 521 close to the positive electrode tab along the first direction is greater than or equal to 0.5 mm, it is convenient to prepare the chamfered structure 62, which is beneficial to reducing the preparation complexity of the negative electrode plate 6; when the size of the area where the edge of the negative electrode film layer 61 exceeds the edge of the first part 521 close to the positive electrode tab along the first direction is less than or equal to 3 mm, it is beneficial to reduce the risk of lithium plating, thereby improving the cycle performance of the battery cell.

[0127] In some embodiments, along the first direction, the size of the chamfered structure 62 is smaller than the size of the area where the edge of the negative electrode film layer 61 extends beyond the edge of the first portion 521 near the positive electrode tab. This facilitates the preparation of the chamfered structure 62 and helps reduce the risk of the negative electrode sheet 6 squeezing the packaging bag and causing leakage.

[0128] In some embodiments, a dimension of the chamfered structure along the first direction is 0.5 mm to 1.5 mm.

[0129] A dimension A of the chamfered structure along the first direction may be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, or any value within the above range.

[0130] When the size of the chamfered structure along the first direction is greater than or equal to 0.5 mm, it is beneficial to reduce the risk of the negative electrode sheet squeezing the packaging bag and causing leakage of the packaging bag; when the size of the chamfered structure along the first direction is less than or equal to 1.5 mm, it is beneficial to improve the energy density of the battery cell.

[0131] In some embodiments, the dimension of the chamfered structure 62 along the second direction is greater than the dimension of the chamfered structure 62 along the first direction.

[0132] When the sealing position of the packaging bag of the battery cell is parallel to the second direction (for example, the packaging bag is sealed along the second direction), the edge of the packaging bag in the second direction is more susceptible to greater pressure than the edge in the first direction. By setting the size of the chamfered structure 62 in the second direction to be larger than the size in the first direction, it is helpful to reduce the risk of the negative electrode sheet 6 squeezing the packaging bag and causing leakage of the packaging bag.

[0133] In some embodiments, the dimension of the chamfered structure 62 along the second direction is 0.5 mm to 3 mm.

[0134] A dimension B of the chamfered structure 62 along the second direction may be 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3 mm, or any value within the above range.

[0135] When the size of the chamfered structure 62 along the second direction is greater than or equal to 0.5 mm, it is beneficial to reduce the risk of the negative electrode plate 6 squeezing the packaging bag and causing leakage of the packaging bag; when the size of the chamfered structure 62 along the second direction is less than or equal to 3 mm, it is convenient to process the chamfered structure 62, which is beneficial to reduce the preparation complexity of the chamfered structure 62.

[0136] In some embodiments, the chamfered structure 62 is a rounded structure, which can be an inwardly concave structure or an outwardly convex structure.

[0137] In the embodiment of the present application, the chamfer structure 62 is a rounded structure, which is smoother and helps to further reduce the risk of the packaging bag being broken when subjected to forces such as squeezing, thereby helping to improve the reliability of the battery cell.

[0138] Figure 7 This is a schematic diagram of a negative electrode sheet according to another embodiment of the present application. Figure 7 As shown, the chamfered structure 62 is a rounded structure, and the rounded structure is an outwardly convex structure.

[0139] In some embodiments, the rounded corner structure is a concave structure. Thus, compared with a convex structure, the concave rounded corner structure is beneficial for providing more space for the packaging bag to avoid the packaging bag, which is beneficial for further reducing the risk of the packaging bag being ruptured when subjected to forces such as squeezing, thereby improving the reliability of the battery cell.

[0140] Figure 8 This is a schematic diagram of a negative electrode sheet according to another embodiment of the present application. Figure 8 As shown, the chamfered structure 62 can also be a chamfered right-angle structure. The angle between the extension lines of the first side and the second side can be any value other than 90°, such as 30°, 45°, or 60°.

[0141] In some embodiments, the insulating layer 52 further includes a second portion 522, which is connected to the first portion 521 and is disposed on at least one side of a portion of the positive electrode tab 502. This further enhances the protection against burrs and improves the reliability of the battery cell.

[0142] In some embodiments, an insulating layer 52 is provided at both ends of the positive electrode body 501 along the first direction. The insulating layer 52 close to the positive electrode tab includes a first portion 521 and a second portion 522 , and the insulating layer 52 away from the positive electrode tab includes only the first portion.

[0143] In some embodiments, the negative electrode sheet 6 includes a negative electrode tab 602. Along the first direction, the negative electrode tab 602 is opposite to the positive electrode tab 502. This structural arrangement is conducive to preparing a battery cell with a larger length.

[0144] In some embodiments, the negative electrode current collector 60 of the negative electrode sheet 6 includes a negative electrode body 601 and a negative electrode tab 602 . The negative electrode tab 602 protrudes from the negative electrode body 601 along a first direction. At least one side of the negative electrode body 601 is coated with a negative electrode film layer 61 .

[0145] In some embodiments, the negative electrode sheet 6 includes a negative electrode tab 602. Along the first direction, the negative electrode tab 602 is opposite to the positive electrode tab 502. This structural arrangement is conducive to preparing a battery cell with a larger length.

[0146] In some embodiments, along the first direction, the negative electrode tab 602 may also be disposed on the same side as the positive electrode tab 502 .

[0147] Figure 9A schematic diagram of a battery cell according to an embodiment of the present application. In some embodiments, for example, Figure 9 As shown, the battery cell 3 includes an electrode assembly 33, which includes a positive electrode sheet and a negative electrode sheet; the packaging bag 31 includes two packaging films 310, the electrode assembly is located between the two packaging films 310, and the edges of the two packaging films 310 are connected to each other to form a sealing portion; the battery cell 3 also includes an electrode lead 321, which passes between the two packaging films 310 and is electrically connected to the electrode assembly 33.

[0148] As an example, the battery cell includes two electrode leads, one is a positive lead for electrically connecting to the positive electrode tab 502 of the electrode assembly 33; and the other is a negative lead for electrically connecting to the negative electrode tab 602 of the electrode assembly 33.

[0149] The battery cell of this structure is a soft-pack battery cell. By connecting two packaging films, a closed space can be formed inside the battery cell to accommodate the positive electrode sheet, negative electrode sheet and electrolyte; by electrically connecting the electrode lead to the electrode assembly, it is convenient to draw out the current.

[0150] In some embodiments, the packaging film 310 includes an insulating protective layer, a metal layer, and an insulating connecting layer. The insulating connecting layer is disposed on the surface of the metal layer facing the electrode assembly, while the insulating protective layer is disposed on the surface of the metal layer facing away from the electrode assembly. This seals the electrode assembly and electrolyte for protection while also providing a certain degree of flexibility to cushion the battery cells from compression and vibration.

[0151] In some embodiments, the material of the insulating protection layer may include nylon, the material of the metal layer may include aluminum or steel, and the material of the insulating connection layer may include polypropylene.

[0152] In some embodiments, the packaging film may be an aluminum-plastic film, and the positive electrode sheet and the negative electrode sheet are accommodated in the space formed by the aluminum-plastic film. The battery cell of this structure is a soft-pack battery cell.

[0153] Aluminum-plastic film is a multi-layer composite flexible packaging material consisting of an outer layer of a polymer (such as nylon or polyester), an intermediate layer of an aluminum film (such as aluminum foil), and an inner layer of a polymer (such as polypropylene or polyethylene). Compared to aluminum or steel shells, battery cells made from aluminum-plastic film are known as soft-pack batteries.

[0154] In some embodiments, a battery cell includes multiple positive electrode sheets 5 and multiple negative electrode sheets 6, which are stacked. This structure is a stacked battery cell, which helps improve the space utilization of the battery cell, thereby having a higher energy density.

[0155] In some embodiments, a battery cell includes a positive electrode sheet and multiple negative electrode sheets, a positive electrode sheet includes multiple positive straight sections and multiple positive bent sections, the positive straight sections are connected to the positive bent sections, and the multiple positive straight sections and multiple negative electrode sheets are stacked.

[0156] In some embodiments, a battery cell includes multiple positive electrode sheets and one negative electrode sheet, one negative electrode sheet includes multiple negative straight sections and multiple negative bent sections, the negative straight sections and the negative bent sections are connected, and the multiple negative bent sections and the multiple positive electrode sheets are stacked.

[0157] In a battery cell in which negative electrode sheets and positive electrode sheets are stacked, the battery cell includes an electrode assembly, which includes a negative electrode sheet, a positive electrode sheet and a separator. The electrode assembly has basically no or no bending area. The battery cell of this structure can also be called a stacked battery cell.

[0158] In some embodiments, the material of the insulating layer includes inorganic particles and a binder, the inorganic particles include at least one of aluminum oxide, boehmite, and magnesium oxide, and the binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and vinylidene fluoride-chlorotrifluoroethylene copolymer.

[0159] The inorganic particles have certain insulating properties and can play a role in blocking burrs. The binder can bond the inorganic particles to the surface of the positive electrode current collector, thereby facilitating the bonding of the insulating layer and the positive electrode current collector.

[0160] In some embodiments, the insulating layer 52 is made of an organic material (e.g., an organic insulating layer), and the organic material includes at least one of polyacrylate and polyvinylidene fluoride. These materials all have good insulation properties, effectively preventing short circuits, thereby improving the reliability of the battery cell.

[0161] In some embodiments, the electrolyte includes a solvent, and the solvent includes at least one of a linear carbonate and a linear carboxylate.

[0162] The linear carbonates may have the general formula RO-CO-OR', wherein R and R' are substituted or unsubstituted alkyl groups.

[0163] As an example, the linear carbonate may include at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0164] The linear carboxylic acid ester may have the general formula R1-COO-R2, wherein R1 and R2 may be substituted or unsubstituted alkyl groups.

[0165] As an example, the linear carboxylic acid ester may include at least one of methyl acetate, ethyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

[0166] Linear carbonates and linear carboxylates have relatively low viscosities, and the electrolyte comprising the above solvents has relatively low viscosity, which is beneficial to the transmission of lithium ions, thereby improving the fast charging performance of the battery cell.

[0167] In some embodiments, the linear carbonate includes at least one of dimethyl carbonate and ethyl methyl carbonate, and the linear carboxylic acid ester includes at least one of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate. These solvents have relatively low viscosities, and the electrolyte containing these solvents also has relatively low viscosities, which facilitates the transport of lithium ions and thus improves the fast-charging performance of the battery cells.

[0168] In some embodiments, the sum of the mass contents of the linear carbonate and the linear carboxylate, based on the total mass of the electrolyte, is 10% to 90%, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any value within the foregoing range.

[0169] When the sum of the mass contents of linear carbonates and linear carboxylates is greater than or equal to 10% based on the total mass of the electrolyte, the electrolyte has a lower viscosity, which is conducive to the transmission of lithium ions, and the battery cell has better fast charging performance; when the sum of the mass contents of linear carbonates and linear carboxylates is less than or equal to 90% based on the total mass of the electrolyte, the gas production of linear carbonates and linear carboxylates in the battery cell can be reduced, thereby reducing the risk of the generated gas accumulating between the isolation membrane and the positive electrode plate 5 and the negative electrode plate 6, reducing the risk of lithium plating, and helping to improve the cycle performance of the battery cell.

[0170] In some embodiments, the sum of the mass contents of the linear carbonate and the linear carboxylate is 40% to 80% based on the total mass of the electrolyte. Thus, the sum of the mass contents of the linear carbonate and the linear carboxylate is within a suitable range, allowing the battery cell to achieve both good fast-charging performance and good cycling performance.

[0171] In some embodiments, the solvent further comprises a cyclic carbonate.

[0172] The cyclic carbonate may include at least one of ethylene carbonate (EC) and propylene carbonate (PC).

[0173] Cyclic carbonates have a good ability to dissociate lithium ions. By combining cyclic carbonates with at least one of linear carbonates and linear carboxylates, the transmission of lithium ions in the electrolyte is facilitated, thereby reducing the risk of lithium plating and improving the cycle performance of battery cells.

[0174] In the embodiment of the present application, the type and content of the organic components in the electrolyte can be detected using equipment and methods known in the art. For example, reference can be made to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" to perform qualitative and quantitative analysis of the organic solvent in the electrolyte by gas chromatography.

[0175] In the embodiment of the present application, after quantitative and qualitative detection of each component in the electrolyte, the composition and mass content of the solvent and lithium salt based on the mass of the electrolyte can be determined.

[0176] In some embodiments, the electrolyte solution includes an electrolyte salt including lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0177] Lithium bis(fluorosulfonyl)imide has a good ability to dissociate lithium ions. By combining lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, the electrolyte has a higher ionic conductivity, which is beneficial to the transmission of lithium ions, reduces the risk of lithium plating, and improves the cycle performance of battery cells.

[0178] In some embodiments, based on the total mass of the electrolyte, the sum of the mass contents of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide is 12% to 20%, for example, it can be 12%, 13%, 15%, 16%, 18%, 19%, 20% or any value within the above range.

[0179] When the sum of the mass contents of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide based on the total mass of the electrolyte is greater than or equal to 12%, the electrolyte has a higher ionic conductivity, facilitates the transmission of lithium ions, is beneficial to reducing the risk of lithium plating, and improves the cycle performance of the battery cell; when the sum of the mass contents of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide based on the total mass of the electrolyte is less than or equal to 20%, the electrolyte has a more suitable viscosity, facilitates the transmission of lithium ions, and is beneficial to improving the fast charging performance of the battery cell.

[0180] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide is 1.2 to 9, for example, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 4, 5, 6, 7, 8, 9, or any value within the foregoing ranges. Thus, the electrolyte has high ionic conductivity, facilitates the transport of lithium ions, helps reduce the risk of lithium plating, and improves the cycling performance of the battery cell.

[0181] In some embodiments, the electrolyte salt includes one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0182] In the embodiment of the present application, the types and contents of the inorganic components / lithium salt concentrations in the electrolyte are well known in the art and can be detected using equipment and methods well known in the art. For example, the inorganic components / lithium salt concentrations in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis method with reference to standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods".

[0183] In the embodiments of the present application, a freshly prepared electrolyte can be taken as a sample, the free electrolyte of a fresh battery cell can be taken as a sample, or a battery cell that has been fully discharged (discharged to the lower cut-off voltage so that the battery's state of charge is approximately 0% SOC) can be disassembled in reverse and the free electrolyte obtained from the battery cell can be used as a sample.

[0184] In some embodiments, the ratio of the mass of the electrolyte to the capacity of the battery cell is 2.8 g / Ah to 3.5 g / Ah, for example, 2.8 g / Ah, 2.9 g / Ah, 3.0 g / Ah, 3.1 g / Ah, 3.2 g / Ah, 3.3 g / Ah, 3.4 g / Ah, 3.5 g / Ah, or any value within the above range. In this way, the electrolyte has good wettability on the positive electrode sheet 5 and the negative electrode sheet 6, which is beneficial to the transmission of lithium ions, thereby reducing the risk of lithium plating and improving the cycle performance of the battery cell.

[0185] In some embodiments, the ratio of the mass of the electrolyte to the capacity of the battery cell is 3.0 g / Ah to 3.2 g / Ah. In this way, the electrolyte has good wettability for the positive electrode sheet 5 and the negative electrode sheet 6, which is conducive to the transmission of lithium ions, thereby reducing the risk of lithium plating and improving the cycle performance of the battery cell.

[0186] In some embodiments, the single-side density of the positive electrode sheet 5 is 0.33g / 1540.25mm 2 Up to 0.45g / 1540.25mm 2 , for example, it can be 0.33g / 1540.25mm 2 、0.34g / 1540.25mm 2 、0.36g / 1540.25mm 2 、0.38g / 1540.25mm 2 、0.40g / 1540.25mm 2 、0.41g / 1540.25mm 2 、0.42g / 1540.25mm 2 , 0.43g / 1540.25mm 2, 0.44g / 1540.25mm 2 , 0.45g / 1540.25mm 2 Or any value within the above range.

[0187] The density of the single side of the positive electrode sheet 5 is greater than or equal to 0.33g / 1540.25mm 2 In the case of , it is beneficial to improve the energy density of the battery cell; when the single side density of the positive electrode sheet 5 is less than or equal to 0.45g / 1540.25mm 2 Under such circumstances, it is beneficial to the transmission of lithium ions and to improving the fast charging performance of battery cells.

[0188] In some embodiments, the compaction density of the positive electrode sheet 5 is 2.3 g / cm 3 Up to 2.65g / cm 3 .

[0189] In the embodiment of the present application, the compaction density of the positive electrode sheet is the compaction density when the state of charge (SOC) of the battery cell is 0%. The compaction density of the positive electrode sheet can be 2.3g / cm 3 , 2.32g / cm 3 , 2.35g / cm 3 , 2.36g / cm 3 , 2.38g / cm 3 , 2.4g / cm 3 , 2.42g / cm 3 , 2.45g / cm 3 , 2.48g / cm 3 , 2.5g / cm 3 , 2.52g / cm 3 , 2.55g / cm 3 , 2.58g / cm 3 , 2.6g / cm 3 , 2.62g / cm 3 , 2.65g / cm 3 Or any value within the above range.

[0190] The compaction density of the positive electrode sheet can be measured as follows. At 25°C, the battery cell is discharged at a constant current of 0.33C to 2.0V to obtain a battery cell with 0% SOC. Afterwards, the positive electrode sheet and the negative electrode sheet are removed from the battery cell, and the thickness of the electrode sheet and the thickness of the current collector are measured respectively. The electrode sheet is punched into a small disc with an area of S1 (if it is a double-sided coated electrode sheet, the film layer on one side can be wiped off first), and its weight is weighed and recorded as M1. Then, the film layer of the weighed electrode sheet is wiped off, and the weight of the current collector is weighed and recorded as M0. The single-side density = (M1-M0) / S1. Compacted density = single-side density / (electrode sheet thickness-current collector thickness). In addition, the compaction density of the negative electrode sheet can also be measured according to the above method.

[0191] The compaction density of the positive electrode sheet 5 is greater than or equal to 2.3 g / cm 3 In the case of the battery cell having a higher energy density; the compaction density of the positive electrode sheet 5 is less than or equal to 2.65g / cm 3 In this case, it is convenient for the transmission of lithium ions, which is beneficial to improving the fast charging performance of battery cells.

[0192] In some embodiments, the compaction density of the positive electrode sheet 5 is 2.45 g / cm 3 Up to 2.6g / cm 3 This is beneficial for balancing the energy density and fast charging performance of battery cells.

[0193] In some embodiments, the single-side density of the negative electrode sheet 6 is 0.15g / 1540.25mm 2 Up to 0.22g / 1540.25mm 2 .

[0194] The single side density of the negative electrode sheet can be 0.15g / 1540.25mm 2 、0.16g / 1540.25mm 2 、0.17g / 1540.25mm 2 、0.18g / 1540.25mm 2 、0.19g / 1540.25mm 2 , 0.20g / 1540.25mm 2 , 0.21g / 1540.25mm 2 、0.22g / 1540.25mm 2 Or any value within the above range.

[0195] The single side density of the negative electrode sheet 6 is greater than or equal to 0.15g / 1540.25mm 2In the case of , it is beneficial to improve the energy density of the battery cell; when the single side density of the negative electrode sheet 6 is less than or equal to 0.22g / 1540.25mm 2 Under such circumstances, it is beneficial to the transmission of lithium ions and to improving the fast charging performance of battery cells.

[0196] In some embodiments, the compaction density of the negative electrode sheet 6 is 1.3 g / cm 3 to 1.52g / cm 3 .

[0197] In the embodiment of the present application, the compaction density of the negative electrode sheet is the compaction density when the state of charge (SOC) of the battery cell is 0%. The compaction density of the negative electrode sheet can be 1.3g / cm 3 , 1.32g / cm 3 , 1.35g / cm 3 , 1.38g / cm 3 , 1.4g / cm 3 , 1.42g / cm 3 , 1.45g / cm 3 , 1.48g / cm 3 , 1.5g / cm 3 , 1.52g / cm 3 Or any value within the above range.

[0198] The compaction density of the negative electrode sheet 6 is greater than or equal to 1.3 g / cm 3 In the case of the battery cell having a higher energy density; the compaction density of the negative electrode sheet 6 is less than or equal to 1.52g / cm 3 Under such circumstances, it is convenient for the transmission of lithium ions, which is beneficial to improving the fast charging performance of battery cells.

[0199] In some embodiments, the compaction density of the negative electrode sheet 6 is 1.35 g / cm 3 Up to 1.5g / cm 3 In this way, the negative electrode plate 6 has a suitable compaction density, which is conducive to taking into account both the energy density and fast charging performance of the battery cell.

[0200] In some embodiments, the positive electrode film layer 51 includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate.

[0201] Lithium-containing phosphates may refer to lithium-containing transition metal phosphates with an olivine structure, and may include, for example, lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their modified forms. Modifications may be performed by doping or surface modification. For example, in doping modification, elements such as titanium may be added to lithium iron phosphate; in surface modification, a coating may be applied to the surface of the lithium iron phosphate.

[0202] The lithium phosphate has good structural stability, and the battery monomer containing the lithium phosphate has good cycle performance.

[0203] In some embodiments, the average longest diameter of the primary particles of the lithium phosphate is between 300 nm and 800 nm, for example, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, or any value within the foregoing ranges. This provides an appropriate distance for the escape path of lithium ions, thereby improving the power performance of the battery cell.

[0204] In the examples of this application, a primary particle refers to the smallest unit of a particle within a certain observation range. A primary particle may contain any form of defects, but it is impossible to further define smaller particles within a primary particle. Primary particles may aggregate under physical forces such as van der Waals forces, but this aggregation is easily disaggregated by external forces such as ultrasound, stirring, and roller pressing, ensuring that the primary particles remain the primary component of the positive electrode active material in the film layer.

[0205] The longest diameter of the lithium-containing phosphate refers to the longest straight line passing through the center point of the lithium-containing phosphate and extending to the periphery of the particle.

[0206] In the embodiment of the present application, the average value of the longest diameter can be measured as follows.

[0207] The battery cells were disassembled to obtain the positive electrode sheets. The sheets were then cut along their thickness to expose the longitudinal section of the positive electrode film. Scanning electron microscopy (SEM) was then performed on the longitudinal section of the positive electrode film to determine the longest diameter of the lithium-containing phosphate. As an example, 30 lithium-containing phosphate particles were randomly selected from the longitudinal section of the positive electrode film, and the longest diameters of the 30 particles were measured and averaged.

[0208] In some embodiments, the lithium-containing phosphate includes a lithium-containing phosphate matrix and a carbon coating layer covering at least a portion of the surface of the lithium-containing phosphate matrix. The carbon coating layer is beneficial for improving the conductivity of the lithium-containing phosphate and facilitating the utilization of the capacity of the battery cell.

[0209] In some embodiments, the lithium-phosphate matrix includes lithium iron phosphate, which is doped with at least one of Al, V, and Ti. These doping elements are beneficial for improving the conductivity and other properties of the lithium-phosphate, thereby maximizing the capacity of the battery cell. Furthermore, these doping elements are beneficial for increasing the compaction density of the positive electrode sheet 5, thereby increasing the energy density of the battery cell.

[0210] In some embodiments, based on the total mass of the lithium-containing phosphate, the mass content of Al is 200 ppm to 2500 ppm, the mass content of V is 300 ppm to 2000 ppm, and the mass content of Ti is 1500 ppm to 3500 ppm. With appropriate mass contents of these doping elements, the battery cell has high energy density, capacity, and cycle performance.

[0211] Based on the total mass of the lithium-containing phosphate, the mass content of Al may be 200 ppm, 300 ppm, 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2400 ppm, 2500 ppm, or any value within the above ranges; the mass content of V may be 300 ppm, 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, or any value within the above ranges; and the mass content of Ti may be 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2400 ppm, 2500 ppm, 2800 ppm, 3000 ppm, 3200 ppm, 3500 ppm, or any value within the above ranges.

[0212] The elements in the positive electrode active material and the content of each element can be determined by using an argon ion cross-section polisher (model JEOLIB-19530CP) and a scanning electron microscope (model Zeiss Sigma 300) (equipped with an X-ray energy dispersive spectrometer (EDS, model Oxford Energy Dispersive Spectrometer OXFord X-Max-50mm2)).

[0213] As an example, at 25°C, a battery cell was discharged at a constant current of 0.33C to 2.0V, resulting in a 0% SOC. The positive electrode sheet was then removed from the battery cell, and a longitudinal cross-section of the positive electrode film layer was obtained using an ion cross-section polisher. A scanning electron microscope was used to scan the cross-section of the positive electrode active material particles, and the various elements and their contents were tested.

[0214] In some embodiments, the lithium phosphate-containing positive electrode active material includes at least one of LiFePO 4 , LiMnPO 4 , LiNiPO 4 , and LiCoPO 4 . The lithium phosphate-containing positive electrode active material has high structural stability, which helps to improve the cycle life of the battery cell.

[0215] The battery cells are accompanied by Li deintercalation and consumption during the charge and discharge process. The molar content of Li in the positive electrode active material is different when the battery cells are discharged to different states. In the list of positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li will change after the charge and discharge cycle. In the list of positive electrode active materials in this application, the molar content of O is only the ideal state value. Lattice oxygen release will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0216] In some embodiments, the negative electrode film layer 61 includes a negative electrode active material, the negative electrode active material including graphite, and at least a portion of the graphite surface having a coating layer including amorphous carbon. This facilitates rapid embedding of lithium ions into the graphite, thereby improving the fast charging performance of the battery cell.

[0217] In some embodiments, the coating layer has a thickness of 100 nm to 500 nm, for example, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or any value within the foregoing range. Thus, the coating layer has an appropriate thickness to facilitate the insertion and transport of lithium ions, thereby improving the fast charging performance of the battery cell.

[0218] In some embodiments, the graphite includes secondary particles, which facilitates the transmission of lithium ions and helps improve the fast charging performance of the battery cell.

[0219] In some embodiments, the graphite has a degree of graphitization of 90% to 94%, for example, 90%, 91%, 92%, 93%, 94%, or any value within the aforementioned range. Thus, graphite having an appropriate degree of graphitization not only helps the graphite have a relatively suitable specific capacity, but also allows the side reactions in the battery cell to be controlled within an appropriate range, thereby achieving a relatively suitable capacity and cycle life for the battery cell.

[0220] In some embodiments, the volume average particle size Dv50 of the graphite is 15 μm to 25 μm. In this way, the particle size of the graphite is within a suitable range, which is beneficial to improving the compaction density of the negative electrode sheet 6 and thus improving the energy density of the battery cell.

[0221] The volume average particle size (Dv50) of graphite represents the particle size corresponding to the 50% cumulative volume distribution percentage of graphite. It can be measured using instruments and methods known in the art. As an example, a battery cell is disassembled to obtain a negative electrode sheet. The negative electrode film layer of the negative electrode sheet is scraped off to obtain a powder of the negative electrode film layer. The powder of the negative electrode film layer is then added to water and stirred, filtered, and dried to obtain graphite. The particle size distribution is then conveniently measured using a laser particle size analyzer, referring to the laser diffraction method for particle size distribution according to GB / T 19077-2016. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0222] The volume average particle size Dv50 of the graphite can be 115μm, 15.2μm, 15.5μm, 15.8μm, 16μm, 16.2μm, 16.5μm, 16.8μm, 17μm, 17.2μm, 17.5μm, 17.8μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm or any value within the above range.

[0223] In some embodiments, the volume average particle size Dv50 of the graphite is 16 μm to 20 μm. In this way, the particle size of the graphite is within a suitable range, which is beneficial to improving the compaction density of the negative electrode sheet 6 and thus the energy density of the battery cell.

[0224] In some embodiments, the electrolyte includes additives, including at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propane sultone (PS). These additives facilitate film formation at the negative electrode, reducing side reactions at the negative electrode, thereby improving the cycle life, kinetics, and other performance of the battery cell.

[0225] In some embodiments, the weight content of the additive is less than or equal to 5% based on the total weight of the electrolyte, and may be, for example, 5%, 4.8%, 4.5%, 4.2%, 4%, 3.8%, 3.5%, 3%, 2.8%, 2.5%, 2%, 1.8%, 1.5%, 1.2%, 1%, 0.8%, 0.5%, or any value within the foregoing ranges. The appropriate weight content of the additive is beneficial for improving the cycle life, dynamics, and other properties of the battery cell.

[0226] In some embodiments, the additives may be present in an amount of 0.5% to 3% by weight based on the total weight of the electrolyte. The additives may have an appropriate weight content to improve the cycle life, dynamics, and other properties of the battery cell.

[0227] In some embodiments, the battery cell also includes an isolation membrane, which is arranged between the positive electrode plate 5 and the negative electrode plate 6. The isolation membrane includes a base membrane, and the thickness of the base membrane is 5μm to 9μm, for example, it can be 5μm, 6μm, 7μm, 8μm, 8.5μm, 9μm or any value within the above range.

[0228] When the thickness of the base film is greater than or equal to 5μm, the isolation membrane has higher strength, which can reduce the risk of lithium dendrites piercing the isolation membrane and causing short circuit in the battery cell; when the thickness of the base film is less than or equal to 9μm, it is beneficial to reduce the space occupied by the isolation membrane, and the battery cell has a higher energy density.

[0229] In some embodiments, the porosity of the separator is 40% to 55%, for example, 40%, 42%, 45%, 48%, 50%, 52%, 55%, or any value within the above range. This facilitates the electrolyte's infiltration into the separator, facilitating the transfer of lithium ions and thus reducing the risk of lithium plating, resulting in better cycle performance for the battery cell.

[0230] [Battery device] An embodiment of the present application provides a battery device, comprising the battery cell of any of the above embodiments.

[0231] Figure 10 FIG. 1 is a schematic diagram of a battery device according to an embodiment of the present application. Figure 10 As shown, the battery device 10 of the embodiment of the present application may include multiple battery cells 3 to meet different power requirements. The shape of the battery cells 3 of the embodiment of the present application can be set according to the actual application. For example, the battery cells 3 can be cylindrical, rectangular, or other shapes, but the embodiment of the present application is not limited to this.

[0232] The battery device 10 of the embodiment of the present application may further include a box body 11, which may be used to accommodate a plurality of battery cells 3. The interior of the box body 11 of the embodiment of the present application is a hollow structure, and a plurality of battery cells 3 are accommodated in the box body 11. The box body 11 may include two parts, which are respectively referred to as a first box body part 111 and a second box body part 112, and the first box body part 111 and the second box body part 112 are snapped together. The shapes of the first box body part 111 and the second box body part 112 may be determined according to the shapes of the components accommodated therein, for example, they may be determined according to the shape of the combination of the plurality of battery cells 3 accommodated therein, and at least one of the first box body part 111 and the second box body part 112 may have an opening. For example, as Figure 10As shown, the first and second housing portions 111, 112 can both be hollow cuboids, each with one open face. The opening of the first and second housing portions 111, 112 are arranged opposite each other, and the first and second housing portions 111, 112 are interlocked to form a housing 11 having a closed chamber, which can be used to accommodate multiple battery cells 3. The multiple battery cells 3 are connected in parallel, series, or in a mixed combination and then placed in the housing 11 formed by the interlocking of the first and second housing portions 111, 112.

[0233] For example, unlike Figure 10 As shown, only one of the first and second housing portions 111, 112 may be a hollow rectangular parallelepiped with an opening, while the other may be a plate-shaped structure to cover the opening. For example, if the second housing portion 112 is a hollow rectangular parallelepiped structure with an opening and the first housing portion 111 is a plate-shaped structure, the first housing portion 111 covers the opening of the second housing portion 112 to form a housing 11 having a closed chamber, which can be used to accommodate multiple battery cells 3.

[0234] Figure 11 This is a schematic diagram of the cooperation between a battery cell and a thermal management component according to an embodiment of the present application. Figure 12 This is a schematic diagram of another embodiment of the present application of the battery cell and the thermal management component. In some embodiments, combined with Figures 10 to 12 As shown, the battery device includes: a box body 11; a plurality of battery cells 3, the plurality of battery cells 3 are accommodated in the box body 11, the plurality of battery cells 3 are stacked along a third direction, the rated capacity of each battery cell is greater than or equal to 100Ah, the surface of each battery cell includes a first surface 301 and a second surface 302, the area of the first surface is greater than the area of the second surface, and the first surfaces of the plurality of battery cells are relatively arranged along the third direction; a thermal management component 91, used to adjust the temperature of the plurality of battery cells, the thermal management component and the second surfaces of the plurality of battery cells are relatively arranged along a fourth direction, and the fourth direction is perpendicular to the third direction.

[0235] The third direction can be Figure 11 and Figure 12 The fourth direction can be the X direction Figure 11 and Figure 12 The Z direction in .

[0236] Each battery cell 3 may include two first surfaces 301 and two second surfaces 302 . The two first surfaces 301 are opposite to each other along the X direction, and the two second surfaces 302 are opposite to each other along the second direction.

[0237] As an example, the first surface 301 is the surface with the largest surface area of the battery cell.

[0238] As an example, the electrode terminals of the battery cell 3 are disposed on the first surface 301 .

[0239] In this embodiment, the rated capacity of each battery cell is greater than or equal to 100Ah. A large amount of heat will be generated during the charging and discharging process of the battery cell. By matching the thermal management component with the battery cell, it is beneficial to control the temperature of the battery cell and reduce the risk of excessive temperature of the battery cell.

[0240] In some embodiments, the battery device further includes a fixing glue 92 disposed between the thermal management component and the battery cell, and the fixing glue is used to fix the battery cell to the thermal management component, thereby facilitating the fixation between the battery cell and the thermal management component.

[0241] In some embodiments, for example, Figure 11 As shown, the fixing glue 92 is directly connected to the packaging bag. In other words, the fixing glue 92 is directly connected to the packaging bag of the battery cell 3, which is beneficial to improving the energy density of the battery device.

[0242] In this embodiment, the fixing glue 92 is directly connected to the packaging bag, and the battery cells in the battery device are arranged one after another, so the components for fixing the multiple battery cells together can be omitted.

[0243] Figure 13 Schematic diagram of a battery module according to an embodiment of the present application. In some embodiments, for example, Figure 12 and Figure 13 As shown, the battery device further includes a housing 801, which houses at least one battery cell, and the fixing glue 92 is directly connected to the shell wall of the housing 801. The configuration of the housing 801 facilitates better heat dissipation in the battery cell, which helps to reduce the temperature of the battery cell.

[0244] In this embodiment, the battery device includes at least one battery module 80 , and the battery module 80 includes a housing 801 and a plurality of battery cells.

[0245] As an example, the housing 801 has a U-shape. For example, the housing 801 includes a first wall 8011, a second wall 8012, and a third wall 8013. The second wall 8012 is connected to the first wall 8011 and the third wall 8013 at both ends of the extension direction. As an example, the first wall 8011 and the third wall 8013 extend along the Z direction, and the second wall 8012 extends along the X direction.

[0246] As an example, the fixing glue 92 is directly connected to the first wall 8011 and the third wall 8013 of the accommodating shell 801 .

[0247] [Electrical equipment] An embodiment of the present application provides an electrical device, including a battery cell in any of the above embodiments, or a battery device in any of the above embodiments, wherein the battery cell or the battery device is used to store or provide electrical energy.

[0248] The technical solutions described in the embodiments of this application are applicable to various electrical devices using battery devices.

[0249] Electrical equipment can be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and electric tools, etc. Vehicles can be fuel vehicles, gas vehicles, or new energy vehicles. New energy vehicles can be pure electric vehicles, hybrid vehicles, or extended-range vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical equipment.

[0250] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle as an example.

[0251] For example, Figure 14 As shown, it is a schematic diagram of a vehicle according to an embodiment of the present application. Vehicle 1 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor 40, a controller 30 and a battery device 10 can be provided inside the vehicle 1. The controller 30 is used to control the battery device 10 to power the motor 40. For example, a battery device 10 can be provided at the bottom, front or rear of the vehicle 1. The battery device 10 can be used to power the vehicle 1. For example, the battery device 10 can be used as an operating power source for the vehicle 1, for the circuit system of the vehicle 1, for example, for the working power requirements of the vehicle 1 during startup, navigation and operation. In another embodiment of the present application, the battery device 10 can not only serve as an operating power source for the vehicle 1, but also as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0252] [Positive electrode] 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 base layer and a metal layer formed on at least one surface of the polymer base layer. 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.).

[0253] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.1 Al 0.05 O2) and its modified compounds, etc. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0254] The battery is accompanied by Li deintercalation and consumption during the charge and discharge process. The molar content of Li in the positive electrode active material is different when the battery is discharged to different states. In the list of positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li will change after the charge and discharge cycle. In the list of positive electrode active materials in this application, the molar content of O is only the ideal state value. Lattice oxygen release will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0255] In some embodiments, the positive electrode film layer further includes a binder. As an 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.

[0256] In some embodiments, the positive electrode film layer further includes a conductive agent. As an 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.

[0257] [Negative electrode] In some embodiments, the negative electrode current collector may be a metal foil or a composite negative electrode current collector. The negative electrode current collector may be copper foil. The composite negative electrode current collector may be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0258] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material includes graphite, and may also include at least one of the following materials: soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0259] The negative electrode film layer may also optionally include a binder. For example, the binder may include at least one of styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC-Na), water-soluble unsaturated resin SR-1B, water-based acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0260] The negative electrode film layer may further optionally 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.

[0261] In one embodiment, the negative electrode sheet can be prepared by forming a negative electrode slurry from the aforementioned components used to prepare the negative electrode sheet. For example, the negative electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., deionized water) to form the negative electrode slurry. The negative electrode slurry is then coated onto the negative electrode current collector. After drying and cold pressing, the negative electrode sheet is obtained.

[0262] [Isolator] The separator is used to separate the positive electrode sheet from the negative electrode sheet. The present application has no particular limitation on the type of separator. For example, any well-known porous structure separator with good chemical and mechanical stability can be selected.

[0263] In one embodiment, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0264] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0265] [Example] Example 1 (1) Preparation of negative electrode sheet The negative electrode active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were thoroughly stirred in a deionized water solvent system at a mass ratio of 96.5:0.5:2:1 to obtain a negative electrode slurry. The negative electrode slurry was evenly coated on both sides of the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain the negative electrode sheet. The volume average particle size Dv50 of the artificial graphite was 18μm. When the battery cell was at 0% SOC, the compaction density of the negative electrode film layer was 1.4g / cm 3 The single-side density of the negative electrode film is 0.17g / 1540.25mm 2 .

[0266] A chamfered structure is provided at the connection between the first side and the second side of the negative electrode plate. Along the first direction, the dimension A of the chamfered structure is 1 mm, and along the second direction, the dimension B of the chamfered structure is 1.5 mm.

[0267] (2) Preparation of positive electrode sheet The positive electrode active material lithium iron phosphate, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an N-methylpyrrolidone (NMP) solvent system in a mass ratio of 97:1.0:2.0 to obtain a positive electrode slurry; the inorganic particles of aluminum oxide and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an N-methylpyrrolidone (NMP) solvent system to obtain an insulating slurry; the above-mentioned positive electrode slurry and insulating slurry are respectively and evenly coated on the two side surfaces of the positive electrode current collector aluminum foil to obtain a positive electrode sheet with a positive electrode film layer and an insulating layer, and the tabs are cut to obtain a positive electrode sheet.

[0268] The positive electrode current collector comprises a positive electrode main body and a positive electrode tab, with the positive electrode tab protruding from the main body along a first direction. The positive electrode main body comprises a coating region and a transition region, with the transition region located between the coating region and the positive electrode tab. The positive electrode film is disposed on both sides of the coating region, and an insulating layer is disposed at both ends of the positive electrode film along the first direction. The insulating layer proximal to the positive electrode tab along the first direction comprises a first portion and a second portion, with the first portion disposed on both sides of the coating region and the second portion disposed on both sides of a portion of the positive electrode tab, with the first and second portions connected. Along the first direction, the width D1 of the first portion is 2 mm, and the average thickness D2 of the insulating layer is 30 μm.

[0269] Along the first direction, a dimension H of the first portion of the negative electrode film layer extending beyond the insulating layer is 1.5 mm.

[0270] When the battery cell is at 0% SOC, the compaction density of the positive electrode film is 2.5g / cm 3 The single-side density of the positive electrode film is 0.38g / 1540.25mm 2 .

[0271] (3) Preparation of electrolyte In an argon atmosphere glove box (H2O content <10ppm, O2 content <1ppm), the electrolyte salt lithium hexafluorophosphate LiPF6 and lithium bis(fluorosulfonyl)imide were dissolved in a mixed system of organic solvents dimethyl carbonate (DMC), ethyl acetate (EA), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) in a mass ratio of 2:1, and vinylene carbonate (VC) was added and stirred evenly.

[0272] Based on the total mass of the electrolyte, the mass content of LiPF6 is 9.6%, the mass content of LIFSI is 4.8%; the mass content of dimethyl carbonate DMC is 16.3%, the mass content of ethyl acetate EA is 32.5%, the mass content of ethyl methyl carbonate EMC is 8.6%, the mass content of ethylene carbonate EC is 24.8%, and the mass content of vinylene carbonate VC is 3.4%.

[0273] (4) Isolation film The isolation film includes a base film, which is a polyethylene (PE) film with a thickness of 7 μm.

[0274] (5) Preparation of battery cells The positive electrode sheet, separator and negative electrode sheet are stacked according to the lamination preparation process, so that the separator is placed between the positive and negative electrode sheets to isolate the positive and negative electrode sheets. The electrode assembly is placed in an aluminum-plastic film and the electrolyte is injected. After vacuum packaging, standing, formation, shaping and other processes, a battery cell is obtained.

[0275] Example 2-3 The difference between Example 2-3 and Example 1 is that: along the first direction, the size H of the first portion of the negative electrode film layer extending beyond the insulating layer is different.

[0276] Examples 4-5 The difference between Embodiment 4-5 and Embodiment 1 is that the width D1 of the first portion of the insulating layer is different along the first direction.

[0277] Examples 6-7 The difference between Example 6-7 and Example 1 is that the average thickness D2 of the insulating layer is different.

[0278] Examples 8-11 The difference between Examples 8-11 and Example 1 is that the ionic conductivity of the electrolyte is different.

[0279] In Example 8, based on the total mass of the electrolyte, the mass content of LiPF6 is 9.6%, the mass content of LIFSI is 4.8%; the mass content of dimethyl carbonate DMC is 8.6%, the mass content of ethyl methyl carbonate EMC is 41.1%, the mass content of ethylene carbonate EC is 32.5%, and the mass content of vinylene carbonate VC is 3.4%.

[0280] In Example 9, based on the total mass of the electrolyte, the mass content of LiPF6 is 9.6%, the mass content of LIFSI is 4.8%; the mass content of dimethyl carbonate DMC is 24.8%, the mass content of ethyl acetate is 16.3%, the mass content of ethyl methyl carbonate EMC is 24.8%, the mass content of ethylene carbonate EC is 16.3%, and the mass content of vinylene carbonate VC is 3.4%.

[0281] In Example 10, based on the total mass of the electrolyte, the mass content of LiPF6 is 9.6%, the mass content of LIFSI is 4.8%; the mass content of dimethyl carbonate DMC is 8.6%, the mass content of ethyl acetate is 41%, the mass content of ethyl methyl carbonate EMC is 4.4%, the mass content of ethylene carbonate EC is 28.2%, and the mass content of vinylene carbonate VC is 3.4%.

[0282] In Example 11, based on the total mass of the electrolyte, the mass content of LiPF6 is 9.6%, the mass content of LIFSI is 4.8%; the mass content of ethyl acetate is 75.4%, the mass content of ethylene carbonate EC is 6.8%, and the mass content of vinylene carbonate VC is 3.4%.

[0283] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the connection between the first side and the second side of the negative electrode plate is not provided with a chamfer structure.

[0284] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that along the first direction, the negative electrode film layer does not extend beyond the first portion of the insulating layer, and H is 0.

[0285] Comparative Example 3 Comparative Example 3 differs from Example 1 in that the ionic conductivity of the electrolyte is less than 8.5 ms / cm. Based on the total mass of the electrolyte, the mass content of LiPF6 is 9.6%, the mass content of LIFSI is 4.8%, the mass content of ethyl methyl carbonate (EMC) is 49.6%, the mass content of diethyl carbonate (DEC) is 8.6%, the mass content of ethylene carbonate (EC) is 24%, and the mass content of vinylene carbonate (VC) is 3.4%.

[0286] Comparative Example 4 Comparative Example 4 differs from Example 1 in that the ionic conductivity of the electrolyte is greater than 20 ms / cm. Based on the total mass of the electrolyte, the mass content of LiPF6 is 9.6%, the mass content of LIFSI is 4.8%, the mass content of ethyl acetate EA is 79.6%, the mass content of ethylene carbonate EC is 2.6%, and the mass content of vinylene carbonate VC is 3.4%.

[0287] Table 1 Data of Examples and Comparative Examples

[0288] In Table 1, H is the size of the area where the edge of the negative electrode film layer exceeds the edge of the positive electrode tab in the first part along the first direction; D1 is the size of the first part along the first direction; and D2 is the average thickness of the insulating layer.

[0289] Table 2 Data of some examples

[0290] Table 3 Data of some examples

[0291] In the embodiment of the present application, the cycle performance of the battery cell is reflected by the number of cycles in which the discharge capacity of the battery cell decays to 80% of the first-cycle discharge capacity. The more cycles, the better the cycle performance of the battery cell. The reliability of the battery cell is reflected by whether the battery cell leaks, wherein the leakage of the battery cell can be reflected by the thickness increase rate of the battery cell after heating at 60°C.

[0292] As shown in Examples 1-11 and Comparative Examples 1-4, by setting the edge of the negative electrode film layer to extend beyond the edge of the first part, a chamfered structure is provided at the connection between the first side and the second side of the negative electrode plate, and the ionic conductivity of the electrolyte is 8.5ms / cm to 20ms / cm, the battery cell can have both good cycle performance and high reliability.

[0293] In combination with Examples 1-3, the dimension H of the area where the edge of the negative electrode film layer exceeds the edge of the first portion along the first direction is set to 0.5 mm to 3 mm, and the battery cell can have better cycle performance, higher energy density and higher reliability.

[0294] In combination with Example 1 and Examples 4-5, the dimension D1 of the first portion of the insulating layer along the first direction is set to 1 mm to 3 mm, and the battery cell can have better cycle performance, higher energy density and higher reliability.

[0295] As shown in Example 1 and Examples 6-7, the thickness of the insulating layer is set to 10 μm to 50 μm, and the battery cell can have good cycle performance, high energy density and high reliability.

[0296] As shown in Example 1 and Examples 8-11, the ionic conductivity of the electrolyte is 8.5 ms / cm to 20 ms / cm, and the battery cell can have both good cycle performance and high reliability.

[0297] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

[0298] The following is a brief introduction to the test methods for the physical and chemical parameters and performance parameters involved in the embodiments of this application. It should be understood that the following test methods are only examples, and other test methods known in the art can also be used for testing.

[0299] 1. Cyclic performance test At 45°C, charge the battery cell at a constant current of 0.5C to 3.65V, then charge it at a constant voltage to 0.05C, let it stand for 10 minutes, and then discharge it at a constant current of 1C to 2.0V. This is one charge and discharge cycle, and record the first-cycle discharge capacity. Let it stand for 10 minutes and repeat the above charge and discharge cycle until the discharge capacity of the battery cell decays to 80% of the first-cycle discharge capacity. Stop the test and record the number of cycles.

[0300] 2. Leakage test At 25°C, the thickness of the battery cell is measured as H0. Place the battery cell on a metal plate at 60°C for heating. After 2 hours, the thickness of the battery cell is measured as H1. If the thickness increase rate (H1-H0) / H0 is less than 5%, leakage is determined.

[0301] In this test method, if the thickness increase rate is too small, it indicates that the packaging bag is damaged and there is a risk of electrolyte leakage.

[0302] 3. Energy density test At 25°C, charge the battery cell at a constant current of 0.33C to a cut-off voltage of 3.65V, then charge at a constant voltage of ≤0.05C, and then discharge at a constant current of 0.33C to a cut-off voltage of 2.0V. Record the discharge energy E0 and discharge capacity C0. Measure the cell dimensions (maximum outer contour length, width, and thickness) and calculate the cell volume V0. The energy density of the battery cell is E0 / V0, expressed in Wh / L.

[0303] 4. Self-discharge test At 25±2℃, the battery cell is adjusted to 30% SOC state by discharge mode. After standing for 12 hours, the initial voltage V0 is recorded. At the same temperature, it is continued to stand for 48 hours and the end voltage V1 is recorded. The self-discharge K value = (V0-V1) / 48, and the unit of K value is mV / h.

Claims

1. A battery cell, characterized in that: include: A positive electrode sheet, a negative electrode sheet, an electrolyte and a packaging bag, wherein the positive electrode sheet, the negative electrode sheet and the electrolyte are contained in the packaging bag; The positive electrode sheet includes a positive electrode current collector, a positive electrode film layer, and an insulating layer. The positive electrode current collector includes a positive electrode main body and a positive electrode tab. The positive electrode tab protrudes from the positive electrode main body along a first direction. The positive electrode main body includes a coating area and a transition area. Along the first direction, the transition area is located at at least one end of the coating area. The positive electrode film layer is provided on at least one side surface of the coating area. The insulating layer includes a first portion, and the first portion is provided on at least one side surface of the transition area. The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one side surface of the negative electrode current collector, and along the first direction, the edge of the negative electrode film layer exceeds the edge of the first portion close to the positive electrode tab; wherein, A chamfered structure is provided at the connection between the first side and the second side of the negative electrode sheet, the first side extends along the first direction, the second side extends along the second direction, and the first direction and the second direction are perpendicular to the thickness direction of the negative electrode sheet; The ionic conductivity of the electrolyte is 8.5 ms / cm to 20 ms / cm.

2. The battery cell according to claim 1, wherein: The ionic conductivity of the electrolyte is 12 ms / cm to 16 ms / cm.

3. The battery cell according to claim 1, wherein: Along the first direction, a size of the first portion is 1 mm to 3 mm.

4. The battery cell according to claim 1, wherein: The average thickness of the insulating layer is 10 μm to 50 μm.

5. The battery cell according to claim 1, characterized in that Along the first direction, a dimension of the edge of the negative electrode film layer extending beyond the edge of the first portion close to the positive electrode tab is 0.5 mm to 3 mm.

6. The battery cell according to claim 1, characterized in that Along the first direction, the size of the chamfered structure is smaller than the size of a region where the edge of the negative electrode film layer extends beyond the first portion and is close to the edge of the positive electrode tab.

7. The battery cell according to claim 1, characterized in that A dimension of the chamfered structure along the first direction is 0.5 mm to 1.5 mm.

8. The battery cell according to claim 1, wherein: A size of the chamfered structure along the second direction is greater than a size of the chamfered structure along the first direction.

9. The battery cell according to claim 1, characterized in that A dimension of the chamfered structure along the second direction is 0.5 mm to 3 mm.

10. The battery cell according to claim 1, characterized in that The chamfered structure is a rounded structure.

11. The battery cell according to claim 10, characterized in that The rounded corner structure is a concave structure.

12. The battery cell according to claim 1, wherein The insulating layer further includes a second portion, which is connected to the first portion and is disposed on at least one side surface of a partial region of the positive electrode tab.

13. The battery cell according to claim 1, characterized in that The negative electrode sheet includes a negative electrode tab, and along the first direction, the negative electrode tab is opposite to the positive electrode tab.

14. The battery cell according to claim 1, characterized in that The battery cell includes an electrode assembly, and the electrode assembly includes the positive electrode sheet and the negative electrode sheet; The packaging bag includes two packaging films, the electrode assembly is located between the two packaging films, and the edges of the two packaging films are connected to each other to form a sealing portion; The battery cell further includes an electrode lead passing through between the two packaging films and electrically connected to the electrode assembly.

15. The battery cell according to claim 14, characterized in that The packaging film includes an insulating protective layer, a metal layer and an insulating connecting layer. The insulating connecting layer is arranged on a surface of the metal layer facing the electrode assembly, and the insulating protective layer is arranged on a surface of the metal layer away from the electrode assembly.

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

17. The battery cell according to claim 16, characterized in that The linear carbonate includes at least one of dimethyl carbonate and ethyl methyl carbonate, and the linear carboxylic acid ester includes at least one of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

18. The battery cell according to claim 16, characterized in that Based on the total mass of the electrolyte, the sum of the mass contents of the linear carbonate and the linear carboxylic acid ester is 10% to 90%.

19. The battery cell according to claim 18, characterized in that Based on the total mass of the electrolyte, the sum of the mass contents of the linear carbonate and the linear carboxylic acid ester is 40% to 80%.

20. The battery cell according to claim 16, wherein: The solvent also includes cyclic carbonates.

21. The battery cell according to claim 1, characterized in that The ratio of the mass of the electrolyte to the capacity of the battery cell is 2.8 g / Ah to 3.5 g / Ah.

22. The battery cell according to claim 21, characterized in that The ratio of the mass of the electrolyte to the capacity of the battery cell is 3.0 g / Ah to 3.2 g / Ah.

23. The battery cell according to claim 1, characterized in that The single-side density of the positive electrode sheet is 0.33g / 1540.25mm 2 Up to 0.45g / 1540.25mm 2 .

24. The battery cell according to claim 1, characterized in that The compaction density of the positive electrode sheet is 2.3 g / cm 3 Up to 2.65g / cm 3 .

25. The battery cell according to claim 24, characterized in that The compaction density of the positive electrode sheet is 2.45 g / cm 3 Up to 2.6g / cm 3 .

26. The battery cell according to claim 1, characterized in that The single-side density of the negative electrode sheet is 0.15g / 1540.25mm 2 Up to 0.22g / 1540.25mm 2 .

27. The battery cell according to claim 1, characterized in that The compaction density of the negative electrode sheet is 1.3 g / cm 3 to 1.52g / cm 3 .

28. The battery cell according to claim 27, characterized in that The compaction density of the negative electrode sheet is 1.35 g / cm 3 Up to 1.5g / cm 3 .

29. The battery cell according to claim 1, characterized in that The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate.

30. The battery cell according to claim 29, characterized in that The average value of the longest diameter of the primary particles of the lithium phosphate is 300 nm to 800 nm.

31. The battery cell according to claim 30, characterized in that The lithium-containing phosphate includes a lithium-containing phosphate matrix and a carbon coating layer that covers at least a portion of the surface of the lithium-containing phosphate matrix.

32. The battery cell according to claim 31, characterized in that The lithium-containing phosphate matrix includes lithium iron phosphate, and the lithium iron phosphate is doped with at least one of Al, V, and Ti.

33. The battery cell according to claim 32, characterized in that Based on the total mass of the lithium-containing phosphate, the mass content of Al is 200 ppm to 2500 ppm, the mass content of V is 300 ppm to 2000 ppm, and the mass content of Ti is 1500 ppm to 3500 ppm.

34. The battery cell according to claim 1, characterized in that The negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite, at least a portion of the surface of the graphite has a coating layer, and the coating layer includes amorphous carbon.

35. The battery cell according to claim 34, characterized in that The thickness of the coating layer is 100 nm to 500 nm.

36. The battery cell according to claim 34, characterized in that The graphite includes secondary particles.

37. The battery cell according to claim 34, characterized in that The graphite has a degree of graphitization of 90% to 94%.

38. The battery cell according to claim 34, characterized in that The volume average particle size Dv50 of the graphite is 15 μm to 25 μm.

39. The battery cell according to claim 38, characterized in that The volume average particle size Dv50 of the graphite is 16 μm to 20 μm.

40. The battery cell according to claim 1, wherein The electrolyte includes an additive, and the additive includes at least one of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone.

41. The battery cell according to claim 40, characterized in that Based on the total mass of the electrolyte, the mass content of the additive is less than or equal to 5%.

42. The battery cell according to claim 41, characterized in that The mass content of the additive is 0.5% to 3% based on the total mass of the electrolyte.

43. A battery device, characterized in that: include: A plurality of battery cells according to any one of claims 1-42.

44. The battery device according to claim 43, characterized in that The battery device comprises: Box; a plurality of battery cells, the plurality of battery cells being accommodated in the box, the plurality of battery cells being stacked along a third direction, the rated capacity of each battery cell being greater than or equal to 100 Ah, the surface of each battery cell including a first surface and a second surface, the area of the first surface being greater than the area of the second surface, and the first surfaces of the plurality of battery cells being arranged opposite to each other along the third direction; A thermal management component is used to adjust the temperature of the plurality of battery cells. The thermal management component is arranged opposite to the second surfaces of the plurality of battery cells along a fourth direction, and the fourth direction is perpendicular to the third direction.

45. The battery device according to claim 44, characterized in that The battery device further includes a fixing glue, which is disposed between the thermal management component and the battery cell, and is used to fix the battery cell to the thermal management component.

46. The battery device according to claim 45, characterized in that The fixing glue is directly connected to the packaging bag.

47. The battery device according to claim 45, characterized in that The battery device further includes a housing shell, wherein the housing shell accommodates at least one battery cell, and the fixing glue is directly connected to a shell wall of the housing shell.

48. An electrical device, characterized in that: include: A plurality of battery cells according to any one of claims 1-42, or a battery device according to any one of claims 43-47, wherein the battery cells or the battery device are used to store or provide electrical energy.

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