Battery cells, battery devices, electrical equipment

Abstract

A battery cell, a battery device, and an electrical appliance belong to the field of battery technology. The battery cell includes: a positive electrode, a negative electrode, an electrolyte, and a packaging bag; the positive electrode includes a positive current collector, a positive electrode film, and an insulating layer; the positive current collector includes a positive electrode body and a positive electrode tab; the positive electrode body includes a coating area and a transition area; along a first direction, the transition area is located at at least one end of the coating area; the positive electrode film is disposed on at least one side surface of the coating area; the insulating layer includes a first portion disposed on at least one side surface of the transition area; the negative electrode includes a negative electrode film; along the first direction, the edge of the negative electrode film extends beyond the edge of the first portion near the positive electrode tab; a chamfered structure is provided at the connection between the first and second sides of the negative electrode; the electrolyte has an ionic conductivity of 8.5 mS / cm to 20 mS / cm, which can improve the reliability and cycle performance of the battery cell.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery cell, a battery device, and an electrical appliance. Background Technology

[0002] The new energy industry is attracting increasing attention. Within this industry, battery technology is a crucial factor in its development.

[0003] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, service life, capacity, fast charging performance, and reliability. How to provide a battery cell with high reliability and good cycle performance is a technical problem that urgently needs to be solved. Summary of the Invention

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

[0005] To achieve the above objectives, this application provides a battery cell, a battery device, and an electrical appliance.

[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 within the packaging bag; the positive electrode sheet includes a positive current collector, a positive electrode film layer, and an insulating layer, the positive current collector includes a positive electrode body portion and a positive electrode tab, the positive electrode tab protruding from the positive electrode body portion along a first direction, the positive electrode body portion including a coating region and a transition region, the transition region being located at at least one end of the coating region along the first direction, the positive electrode film layer being disposed on at least one side surface of the coating region, and the insulating layer including a first portion, the first portion being... The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side surface of the negative current collector. Along the first direction, the edge of the negative electrode film layer extends beyond the edge of the first portion near the positive electrode tab. The connection between the first and second sides of the negative electrode sheet is provided with a chamfer structure. The first side extends along the first direction, and the second side extends along the second direction. The first and second directions 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.

[0007] In this embodiment, by providing a chamfered structure at the connection between the first and second sides of the negative electrode sheet, the risk of damage to the packaging bag and electrolyte leakage caused by the negative electrode sheet squeezing the packaging bag can be reduced. Furthermore, by extending the edge of the negative electrode film beyond the edge of the first portion of the insulating layer near the positive electrode tab, the risk of damage to the packaging bag and electrolyte leakage caused by the positive electrode sheet squeezing the packaging bag can be reduced, while eliminating the need for a chamfered structure on the positive electrode sheet. By setting the ionic conductivity of the electrolyte to 8.5 ms / cm to 20 ms / cm, the lithium-ion transport speed is improved, thereby compensating for the lithium plating problem caused by the edge of the negative electrode film extending beyond the edge of the positive electrode film and the edge of the first portion of the insulating layer near the positive electrode tab, thus improving the cycle performance of the battery cell. Therefore, this embodiment can balance the reliability and 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 12 ms / cm, it is beneficial to improve the lithium-ion transport speed, thereby reducing the risk of lithium plating and resulting in better cycle performance of the battery cell. When the ionic conductivity of the electrolyte is less than or equal to 16 ms / cm, it is beneficial to reduce gas production in the battery cell, thereby reducing the adverse effects of gas production on cycle performance.

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

[0011] When the dimension of the first part along the first direction is greater than or equal to 1 mm, the insulating layer can effectively block burrs, which helps reduce the risk of burrs on the positive electrode overlapping with the negative electrode or puncturing the separator, resulting in higher reliability of the battery cell. When the dimension of the first part along the first direction is less than or equal to 3 mm, it helps to improve the energy density of the battery cell.

[0012] In some embodiments, the average thickness of the insulating layer is 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 helps reduce the risk of burrs on the positive electrode overlapping with the negative electrode or puncturing the separator, resulting in higher reliability of the battery cell. When the average thickness of the insulating layer is less than or equal to 50 μm, it helps to improve the energy density of the battery cell.

[0014] In some embodiments, along the first direction, the area of ​​the negative electrode film layer extending beyond the edge of the first portion near the edge of the positive electrode tab has a size of 0.5 mm to 3 mm.

[0015] When the area of ​​the negative electrode film extending beyond the edge of the first part near the edge of the positive electrode tab along the first direction is greater than or equal to 0.5 mm, it facilitates the fabrication of the chamfered structure and helps reduce the fabrication complexity of the negative electrode sheet. When the area of ​​the negative electrode film extending beyond the edge of the first part near the edge of the positive electrode tab along the first direction is less than or equal to 3 mm, it helps reduce the risk of lithium plating and thus helps improve the cycle performance of the battery cell.

[0016] In some embodiments, along the first direction, the size of the chamfered structure is smaller than the size of the region where the edge of the negative electrode film extends beyond the first portion near the edge of the positive electrode tab. This facilitates the fabrication of the chamfered structure, thereby reducing the risk of leakage from the packaging bag caused by the negative electrode sheet compressing the packaging bag.

[0017] In some embodiments, the chamfered structure has a dimension of 0.5 mm to 1.5 mm along the first direction. When the dimension 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 leakage from the packaging bag caused by the negative electrode sheet squeezing the packaging bag; when the dimension 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.

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

[0019] When the sealing position of the battery cell packaging bag 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 a chamfer structure with a dimension in the second direction that is larger than that in the first direction, it is beneficial to reduce the risk of leakage caused by the negative electrode sheet squeezing the packaging bag.

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

[0021] When the dimension of the chamfered structure along the second direction is greater than or equal to 0.5 mm, it helps to reduce the risk of leakage from the packaging bag caused by the negative electrode sheet squeezing the packaging bag; when the dimension of the chamfered structure along the second direction is less than or equal to 3 mm, it facilitates the processing of the chamfered structure and helps to reduce the complexity of the chamfered structure preparation.

[0022] In some embodiments, the chamfered structure is a rounded corner structure. This helps to further reduce the risk of the packaging bag breaking when subjected to forces such as compression, thereby improving the reliability of the battery cell.

[0023] In some embodiments, the rounded corner structure is a concave structure. This helps to further reduce the risk of the packaging bag breaking when subjected to forces such as compression, thereby improving the reliability of the battery cell.

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

[0025] In some embodiments, the negative electrode sheet includes a negative electrode tab, and the negative electrode tab and the positive electrode tab are opposite each other along the first direction. This structural arrangement is advantageous for manufacturing battery cells with larger dimensions in the length direction.

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

[0027] The battery cell with this structure is a pouch cell. The connection of two packaging films can form a sealed space inside the battery cell to accommodate the positive electrode, negative electrode and electrolyte. By electrically connecting the electrode leads to the electrode assembly, it is easy 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, and the insulating protective layer is disposed on the surface of the metal layer away from the electrode assembly. This design not only seals the electrode assembly and electrolyte for protection but also provides a degree of flexibility to cushion the battery cells when subjected to compression or vibration.

[0029] In some embodiments, the electrolyte includes a solvent, which includes at least one of linear carbonates and linear carboxylic acid esters. The solvent has a low viscosity, and the electrolyte including the solvent has a low viscosity, which is beneficial for lithium-ion transport, 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 carboxylic acid ester includes at least one of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate. The solvents described above have low viscosity, and the electrolyte containing these solvents has low viscosity, which is beneficial for lithium-ion transport, thereby improving the fast-charging performance of the battery cells.

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

[0032] When the total mass content of linear carbonate and linear carboxylic acid ester is greater than or equal to 10% based on the total mass of the electrolyte, the electrolyte has a lower viscosity, which is beneficial for lithium-ion transport, and the battery cell has better fast-charging performance. When the total mass content of linear carbonate and linear carboxylic acid ester is less than or equal to 90% based on the total mass of the electrolyte, the gas production of linear carbonate and linear carboxylic acid ester in the battery cell can be reduced, thereby reducing the risk of gas accumulation between the separator and the positive and negative electrode plates, reducing the risk of lithium plating, and improving the cycle performance of the battery cell.

[0033] In some embodiments, the sum of the mass contents of the linear carbonate and the linear carboxylic acid ester is 40% to 80% based on the total mass of the electrolyte. This provides a suitable range for the sum of the mass contents of the linear carbonate and the linear carboxylic acid ester, allowing the battery cell to achieve both good fast-charging performance and good cycle performance.

[0034] In some embodiments, the solvent further includes cyclic carbonates. Cyclic carbonates have a good ability to dissociate lithium ions. By combining cyclic carbonates with at least one of linear carbonates and linear carboxylic esters, the transport of lithium ions in the electrolyte is facilitated, 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. This provides good wettability of the electrolyte to both the positive and negative electrode plates, which is beneficial for lithium-ion transport, 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. This provides good wettability of the electrolyte to both the positive and negative electrode plates, which is beneficial for lithium-ion transport, thereby reducing the risk of lithium plating and improving the cycle performance of the battery cell.

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

[0038] The density on one side of the positive electrode sheet is greater than or equal to 0.33 g / 1540.25 mm. 2 Under these conditions, it is beneficial to improve the energy density of the battery cell; when the density of one side of the positive electrode is less than or equal to 0.45g / 1540.25mm. 2 Under these conditions, it is beneficial for lithium-ion transport and helps improve the fast-charging performance of individual battery cells.

[0039] In some embodiments, the compaction density of the positive electrode sheet is 2.3 g / cm³. 3 Up to 2.65 g / cm 3 .

[0040] The compaction density of the positive electrode sheet is greater than or equal to 2.3 g / cm³. 3 Under these conditions, the battery cell has a high energy density; and the compaction density of the positive electrode is less than or equal to 2.65 g / cm³. 3 In this case, it facilitates the transport of lithium ions, which is beneficial to improving the fast charging performance of individual battery cells.

[0041] In some embodiments, the compaction density of the positive electrode sheet is 2.45 g / cm³. 3 Up to 2.6 g / cm 3 This approach helps to balance the energy density of individual battery cells and their fast-charging performance.

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

[0043] The density on one side of the negative electrode sheet is greater than or equal to 0.15 g / 1540.25 mm. 2 Under these conditions, it is beneficial to improve the energy density of the battery cell; when the density of one side of the negative electrode is less than or equal to 0.22g / 1540.25mm. 2 Under these conditions, it is beneficial for lithium-ion transport and helps improve the fast-charging performance of individual battery cells.

[0044] In some embodiments, the compaction density of the negative electrode sheet is 1.3 g / cm³. 3 Up to 1.52 g / cm 3 .

[0045] The compaction density of the negative electrode sheet is greater than or equal to 1.3 g / cm³.3 Under these conditions, the battery cell has a high energy density; and the compaction density of the negative electrode sheet is less than or equal to 1.52 g / cm³. 3 In this case, it facilitates the transport of lithium ions, which is beneficial to improving the fast charging performance of individual battery cells.

[0046] In some embodiments, the compaction density of the negative electrode sheet is 1.35 g / cm³. 3 Up to 1.5g / cm 3 In this way, the negative electrode sheet has a suitable compaction density, which is beneficial for balancing the energy density and fast charging performance of the battery cell.

[0047] In some embodiments, the positive electrode film layer comprises a positive electrode active material, which includes a lithium phosphate. Lithium phosphate exhibits good structural stability, and battery cells containing lithium phosphate demonstrate good cycle performance.

[0048] In some embodiments, the average longest diameter of the primary particles containing lithium phosphate is between 300 nm and 800 nm. This provides a suitable distance for the lithium ion extraction path, which is beneficial for 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 that at least partially covers the surface of the lithium-containing phosphate matrix. The carbon coating layer helps to improve the conductivity of the lithium-containing phosphate, facilitating the utilization of the battery cell's capacity.

[0050] In some embodiments, the lithium phosphate matrix comprises 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 improving the capacity of the battery cell. Furthermore, these doping elements also help increase the compaction density of the positive electrode, thus improving the energy density of the battery cell.

[0051] In some embodiments, based on the total mass of the lithium 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. The doping elements at these concentrations are beneficial for improving the conductivity and other properties of the lithium phosphate, thereby improving the capacity of the battery cell. Furthermore, the doping elements at these concentrations also help to increase the compaction density of the positive electrode, thereby improving the energy density of the battery cell.

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

[0053] In some embodiments, the thickness of the coating layer is between 100 nm and 500 nm. This coating layer has a suitable thickness, facilitating lithium-ion insertion and transport, and improving the fast-charging performance of the battery cell.

[0054] In some embodiments, the graphite comprises secondary particles. This facilitates lithium-ion transport and improves the fast-charging performance of individual battery cells.

[0055] In some embodiments, the graphite has a graphitization degree of 90% to 94%. This results in graphite with a suitable graphitization degree, which is beneficial for achieving a suitable specific capacity and for controlling side reactions within the battery cell within a suitable range, thereby enabling the battery cell to have a suitable capacity and cycle life.

[0056] In some embodiments, the volume average particle size Dv50 of the graphite is 15 μm to 25 μm. This appropriate range of graphite particle size is beneficial for increasing 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. This appropriate range of graphite particle size is beneficial for increasing the compaction density of the negative electrode sheet, thereby improving the energy density of the battery cell.

[0058] In some embodiments, the electrolyte includes additives, including at least one selected from vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sulpholactone. These additives facilitate film formation at the negative electrode, reduce side reactions at the negative electrode, and thus improve the cycle life, kinetics, and other performance characteristics of the battery cell.

[0059] In some embodiments, the mass content of the additive is less than or equal to 5% based on the total mass of the electrolyte. The appropriate mass content of the additive is beneficial for improving the cycle life, kinetics, and other performance characteristics of the battery cells.

[0060] In some embodiments, the additive content is 0.5% to 3% by mass, based on the total mass of the electrolyte. The appropriate mass content of the additive is beneficial for improving the cycle life, kinetics, and other performance characteristics of the battery cells.

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

[0062] In some embodiments, the battery device includes: a housing; a plurality of battery cells housed within the housing, the plurality of battery cells being stacked along a third direction, each battery cell having a rated capacity greater than or equal to 100 Ah, each battery cell having a surface including a first surface and a second surface, the area of ​​the first surface being greater than the area of ​​the second surface, the first surfaces of the plurality of battery cells being disposed opposite to each other along the third direction; and a thermal management component for regulating the temperature of the plurality of battery cells, the thermal management component being disposed opposite to the second surfaces of the plurality of battery cells along a fourth direction, the fourth direction being perpendicular to the third direction.

[0063] In this embodiment, the rated capacity of each battery cell is greater than or equal to 100Ah. During the charging and discharging process of the battery cell, a lot of heat will be generated. 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 the battery cell temperature being too high.

[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. This facilitates the fixing of the battery cell to the thermal management component.

[0065] In some embodiments, the adhesive is directly attached to the packaging bag. This helps to improve the energy density of the battery device.

[0066] In some embodiments, the battery device further includes a housing containing at least one of the battery cells, the adhesive being directly attached to the wall of the housing. The housing facilitates better heat dissipation from the battery cells, thus helping to reduce the temperature of the battery cells.

[0067] Thirdly, an electrical device is provided, comprising a battery cell as described in the first aspect and any of the embodiments thereof, or a battery device as described in the second aspect and any of the embodiments thereof, wherein the battery cell or battery device is used to store or provide electrical energy. Attached Figure Description

[0068] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0069] Figure 1 This is a schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0070] Figure 2 This is a schematic diagram of the positive electrode sheet of one embodiment of this application from another perspective;

[0071] Figure 3 This is a schematic diagram of the positive and negative electrode plates in accordance with an embodiment of this application.

[0072] Figure 4 This is a schematic diagram of the negative electrode sheet according to an embodiment of this application;

[0073] Figure 5 This is a schematic diagram of the negative electrode sheet according to an embodiment of this application from another perspective;

[0074] Figure 6 This is a schematic diagram of a battery cell according to an embodiment of this application;

[0075] Figure 7 This is a schematic diagram of the negative electrode sheet according to another embodiment of this application;

[0076] Figure 8 This is a schematic diagram of the negative electrode sheet according to another embodiment of this application;

[0077] Figure 9 This is a schematic diagram of a battery cell according to an embodiment of this application;

[0078] Figure 10 This is a schematic diagram of a battery device according to an embodiment of this application;

[0079] Figure 11 This is a schematic diagram illustrating the interaction between a battery cell and a thermal management component according to an embodiment of this application;

[0080] Figure 12 This is a schematic diagram illustrating the interaction between a battery cell and a thermal management component according to another embodiment of this application;

[0081] Figure 13 This is a schematic diagram of a battery module according to an embodiment of this application;

[0082] Figure 14 This is a schematic diagram of a vehicle according to an embodiment of this application.

[0083] Figure label:

[0084] 5: Positive electrode sheet; 50: Positive current collector; 501: Positive electrode body; 502: Positive electrode tab; 5011: Coated area; 5012: Transition area; 51: Positive electrode film; 52: Insulating layer; 521: First part; 522: Second part; 6: Negative electrode sheet; 60: Negative current collector; 601: Negative electrode body; 602: Negative electrode tab; 61: Negative electrode film; 611: First side; 612: Second side; 62: Chamfered junction Structure; 10: Battery device; 30: Controller; 40: Motor; 11: Housing; 111: First housing section; 112: Second housing section; 33: Electrode assembly; 310: Packaging film; 321: Electrode lead; 301: First surface; 302: Second surface; 91: Thermal management component; 92: Fixing adhesive; 80: Battery module; 801: Housing; 8011: First wall; 8012: Second wall; 8013: Third wall. Detailed Implementation

[0085] Embodiments of the battery cell, battery device, and electrical appliance of this application have been described in detail with appropriate reference to the accompanying drawings; however, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0086] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0087] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0088] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0089] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0090] This application aims to develop a battery cell with high reliability and good cycle performance. In pouch cell batteries, the packaging bag is used to contain the positive electrode, negative electrode, electrolyte, etc. During the use and transportation of the battery cell, the packaging bag may be subjected to compression, collision, etc., and there is a risk of the packaging bag breaking, which increases the risk of electrolyte leakage from the packaging bag, thus hindering the improvement of the battery cell's reliability.

[0091] In view of this, embodiments of this application provide a battery cell, including: a positive electrode sheet, a negative electrode sheet, an electrolyte, and a packaging bag for containing the positive electrode sheet, the negative electrode sheet, and the electrolyte; the positive electrode sheet includes a positive current collector, a positive electrode film layer, and an insulating layer; the positive current collector includes a positive electrode body portion and a positive electrode tab; the positive electrode tab protrudes from the positive electrode body portion along a first direction; the positive electrode body portion 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 disposed on at least one side surface of the coating area; the insulating layer includes a first... The first part is disposed on at least one side surface of the transition region; the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side surface of the negative current collector. Along the first direction, the edge of the negative electrode film layer extends beyond the edge of the first part near the positive electrode tab. A chamfer 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, and the second side extends along the second direction. 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.

[0092] In this embodiment, by providing a chamfered structure at the connection between the first and second sides of the negative electrode sheet, the risk of damage to the packaging bag and electrolyte leakage caused by the negative electrode sheet squeezing the packaging bag can be reduced. Furthermore, by providing an edge of the negative electrode film layer extending beyond the first portion of the insulating layer near the positive electrode tab along the first direction, the risk of damage to the packaging bag and electrolyte leakage caused by the positive electrode sheet squeezing the packaging bag can be reduced, while eliminating the need for a chamfered structure on the positive electrode sheet. This solves the problem of requiring simultaneous chamfering design on both the positive and negative electrode sheets, reducing manufacturing costs. By setting the ionic conductivity of the electrolyte to 8.5 ms / cm to 20 ms / cm, the lithium-ion transport speed is improved, thereby compensating for the "reservoir" effect caused by the negative electrode film layer edge extending beyond the positive electrode film layer edge and the first portion edge of the insulating layer, as well as the lithium plating problem caused by the "reservoir" effect, thus improving the cycle performance of the battery cell. Therefore, this embodiment can balance the reliability and cycle performance of the battery cell.

[0093] The "reservoir" effect is explained as follows: The region where the edge of the negative electrode film extends beyond the edge of the positive electrode film and the edge of the first part of the insulating layer can be called the overhang region. The region where the negative and positive electrode films overlap can be called the main region of the negative electrode film. However, the presence of the overhang region leads to the "reservoir" effect, which also increases the risk of lithium plating and is detrimental to the reliability of the battery cell. Because the lithium intercalation amount in the overhang region is lower than that in the main region of the negative electrode film, a potential difference exists between the overhang region and the main region of the negative electrode film. Lithium ions in the main region of the negative electrode film spontaneously migrate to the overhang region, and the lithium concentration in the overhang region increases continuously with charge-discharge cycles. After multiple charge-discharge cycles, when the battery cell discharges again, all the lithium ions in the main region of the negative electrode film are released, while not all of the lithium ions in the overhang region are released. The lithium ion concentration in the overhang region is higher than that in the main region of the negative electrode film, and the lithium ions in the overhang region migrate to the boundary between the negative electrode film and the overhang region, resulting in an increase in the lithium ion concentration at the boundary. During recharging, the risk of lithium plating at the boundary increases.

[0094] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0095] The battery cell can be a lithium-ion battery.

[0096] During the charging process of a single battery cell, lithium ions are released from the positive electrode active material, move and embed into the negative electrode; while during the discharging process, lithium ions are released from the negative electrode, move and embed into the positive electrode active material.

[0097] It should be understood that the “intercalation” process described in this application refers to the process by which lithium ions are intercalated 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 by which lithium ions are extracted from the positive electrode active material or the negative electrode due to an electrochemical reaction.

[0098] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. The following section describes the battery cell and its components provided in this application.

[0099] [Battery cell]

[0100] This application provides a battery cell, including: a positive electrode, a negative electrode, a packaging bag, and an electrolyte.

[0101] Figure 1 This is a schematic diagram of the positive electrode sheet according to an embodiment of this application. Figure 2 This is a schematic diagram of the positive electrode sheet according to an embodiment of this application from another perspective. (In conjunction with...) Figure 1 and Figure 2 As shown, the positive electrode 5 includes a positive current collector 50, a positive electrode film layer 51, and an insulating layer 52.

[0102] The positive electrode current collector 50 includes a positive electrode body portion 501 and a positive electrode tab 502, the positive electrode tab 502 protruding from the positive electrode body portion 501 along a first direction. The first direction can be... Figure 1 and Figure 2 The x-direction in the middle.

[0103] 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 layer 51 is disposed on at least one side surface of the coating region 5011, and the insulating layer 52 includes a first portion 521, which is disposed on at least one side surface of the transition region 5012.

[0104] As an example, along the first direction, a transition region 5012 is provided at both ends of the coating region 5011, and an insulating layer 52 is provided on at least one side surface of the transition region 5012.

[0105] As another example, along the first direction, only one end of the coating area 5011 near the positive electrode tab 502 is provided with a transition area 5012, and at least one side surface of the transition area 5012 is provided with an insulating layer 52.

[0106] Figure 3This is a schematic diagram illustrating the combination of the positive and negative electrode plates according to an embodiment of this application. Figure 4 This is a schematic diagram of the negative electrode sheet according to an embodiment of this application. Figure 5 This is a schematic diagram from another perspective of the negative electrode sheet according to an embodiment of this application. (In conjunction with...) Figures 3 to 5 As shown, the negative electrode sheet 6 includes a negative electrode current collector 60 and a negative electrode film layer 61 disposed 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 extends beyond the edge of the first portion 521 near the positive electrode tab. A chamfer structure 62 is provided at the connection between the first side 611 and the second side 612 of the negative electrode sheet 6. The first side 611 extends along the first direction, and the second side 612 extends along the second direction. Both the second direction and the first direction are perpendicular to the thickness direction of the negative electrode sheet 6.

[0107] 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°.

[0108] As an example, only along the first direction, the edge of the negative electrode film layer 61 extends beyond the edge of the first portion 521.

[0109] As another example, along both the first and second directions, the edge of the negative electrode film layer 61 extends beyond the edge of the first portion 521. The second direction can be... Figure 3 y direction in .

[0110] The edge of the negative electrode film layer 61 extends beyond the edge of the first part 521. This can be understood as the projection of the negative electrode film layer 61 covering and extending beyond the projection of the first part 521 on the xoy plane.

[0111] As an example, the negative electrode includes two first sides 611 and two second sides 612, the two first sides 611 are arranged opposite each other along a second direction, the two second sides 612 are arranged opposite each other along a first direction, and the first sides 611 and the second sides 612 are connected.

[0112] A chamfer structure 62 is provided at the connection between the first side 611 and the second side 612. The chamfer structure 62 can be a rounded chamfer, a right-angle chamfer, or a composite chamfer. The composite chamfer can be a chamfer that combines a circular arc and a straight line.

[0113] Figure 6 This is a schematic diagram of a battery cell according to an embodiment of this application. (In conjunction with...) Figure 6 As shown, the battery cell 3 includes a packaging bag 31, and the positive electrode 5, the negative electrode 6 and the electrolyte are contained in the packaging bag 31.

[0114] The packaging bag 31 can be made of a flexible material, such as aluminum-plastic film. When subjected to force (e.g., compression), the packaging bag 31 may break and come into contact with the negative electrode plate, thus the corners of the negative electrode plate pose a significant risk of the packaging bag breaking. By providing a chamfered structure 62 at the connection between the first side 611 and the second side 612 of the negative electrode plate 6, the risk of interference between the negative electrode plate and the packaging bag can be reduced. This reduces the risk of damage to the packaging bag and electrolyte leakage caused by the negative electrode plate 6 compressing the packaging bag, thus improving the reliability of the battery cell.

[0115] By extending the edge of the negative electrode film layer 61 beyond the edge of the first portion 521 of the insulating layer 52, which is closer to the edge of the positive electrode tab, the risk of damage to the packaging bag and electrolyte leakage caused by the positive electrode sheet 5 squeezing the packaging bag can be reduced. Furthermore, it eliminates the need for a chamfered structure on the positive electrode sheet 5, thus reducing the manufacturing complexity of the battery cell while maintaining its reliability. 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, and the edge of the negative electrode film layer 61 extends beyond both the edge of the first portion 521 and the edge of the positive electrode film layer 51, the negative electrode sheet has more space to accommodate lithium ions released from the positive electrode sheet, which helps reduce the risk of lithium plating.

[0116] The ionic conductivity of the electrolyte is from 8.5 ms / cm to 20 ms / cm, for example, it can be 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.

[0117] Although the edge of the negative electrode film 61 extending beyond the edge of the first portion 521 of the insulating layer 52 near the positive electrode tab helps reduce the risk of lithium plating, with the charge-discharge cycles of the battery cell, due to 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 61 extends beyond the edge of the first portion 521 and the area where the negative electrode film 61 overlaps with the positive electrode film 51. This is detrimental to further improving the cycle performance of the battery cell. By setting the ionic conductivity of the electrolyte to 8.5 ms / cm to 20 ms / cm, it is beneficial to improve the lithium ion transport speed, thereby compensating for the lithium plating problem caused by the edge of the negative electrode film 61 extending beyond the edge of the positive electrode film 51 and the edge of the first portion 521 of the insulating layer 52, thus improving the cycle performance of the battery cell.

[0118] In the embodiments of this application, the ionic conductivity of the electrolyte can be measured in the following ways.

[0119] For example, after disassembling a battery cell to obtain the electrolyte, the ionic conductivity of the electrolyte is tested using a conductivity meter according to HG / T 4067-2015: Take about 100 ml of the sample to be tested in a dry, clean, corrosion-resistant sample bottle, seal it and place it in a constant temperature water bath at 25±0.5 ℃. When the temperature of the sample to be tested is constant, replace the bottle cap with a rubber stopper with an electrode inserted. When the temperature is within the range of 25±0.5 ℃, read the data, which is the ionic conductivity of the sample to be tested.

[0120] In this embodiment, by providing a chamfered structure 62 at the connection between the first side 611 and the second side 612 of the negative electrode 6, the risk of damage to the packaging bag and electrolyte leakage caused by the negative electrode 6 squeezing the packaging bag can be reduced. Furthermore, by providing an edge along the first direction where the edge of the negative electrode film 61 extends beyond the first portion 521 of the insulating layer 52 near the edge of the positive electrode tab, the risk of damage to the packaging bag and electrolyte leakage caused by the positive electrode 5 squeezing the packaging bag can be reduced, while eliminating the need for a chamfered structure 62 on the positive electrode 5. By setting the ionic conductivity of the electrolyte to 8.5 ms / cm to 20 ms / cm, the lithium-ion transport speed is improved, thereby compensating for the lithium plating problem caused by the edge of the negative electrode film 61 extending beyond the edge of the positive electrode film 51 and the edge of the first portion 521 of the insulating layer 52, thus improving the cycle performance of the battery cell. Therefore, this embodiment can balance the reliability and cycle performance of the battery cell.

[0121] In some embodiments, the ionic conductivity of the electrolyte is from 12 ms / cm to 16 ms / cm.

[0122] When the ionic conductivity of the electrolyte is greater than or equal to 12 ms / cm, it is beneficial to improve the lithium-ion transport speed, thereby reducing the risk of lithium plating and resulting in better cycle performance of the battery cell. When the ionic conductivity of the electrolyte is less than or equal to 16 ms / cm, it is beneficial to reduce gas production in the battery cell, thereby reducing the adverse effect of gas production on cycle performance.

[0123] In some embodiments, the size of the first portion 521 is 1 mm to 3 mm along the first direction.

[0124] Along the first direction, the dimension D1 of the first part 521 can be 1mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm, 3mm or any value within the above range.

[0125] The dimension of the first part 521 along the first direction can be an average dimension. For example, the length of the first part 521 in the first direction is tested at multiple locations, and then the average value is taken as D1.

[0126] As an example, the first part 521 has a rectangular shape.

[0127] During the preparation of the positive electrode sheet, such as when preparing the positive electrode tab by cutting or when cutting a large positive electrode sheet into two positive electrode sheets, burrs are usually generated. The insulating layer 52 can play a certain role in blocking burrs, for example, reducing the risk of burrs overlapping with the negative electrode sheet and reducing the risk of burrs puncturing the separator.

[0128] When the dimension of the first part 521 along the first direction is greater than or equal to 1 mm, the insulating layer 52 can effectively block burrs, which helps reduce the risk of burrs on the positive electrode 5 overlapping with or puncturing the separator on the negative electrode 6, and the battery cell has high reliability. When the dimension of the first part 521 along the first direction is less than or equal to 3 mm, it helps to improve the energy density of the battery cell.

[0129] In some embodiments, the average thickness of the insulating layer 52 is 10 μm to 50 μm.

[0130] The average thickness of the insulating layer 52 is the thickness on one side.

[0131] The average thickness D2 of the insulating layer 52 can be 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm or any value within the above range.

[0132] As an example, along the first direction, the thickness of the insulating layer at multiple locations (e.g., 10 locations) is measured using a scanning electron microscope (SEM), and the average of the multiple thicknesses is taken as the average thickness D2 of the insulating layer.

[0133] 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 helps reduce the risk of burrs on the positive electrode 5 overlapping with or puncturing the separator on the negative electrode 6, resulting in higher reliability of the battery cell. When the average thickness of the insulating layer 52 is less than or equal to 50 μm, it helps to improve the energy density of the battery cell.

[0134] As an example, the insulating layer 52 has the same or nearly the same thickness at various locations.

[0135] As another example, there is a partial fusion region between the insulating layer 52 and the positive electrode film layer 51. This fusion region may be caused by the flow of the slurry during the coating process of the positive electrode film layer and the insulating layer. In this case, the average thickness of the insulating layer 52 refers to the average thickness of the non-fusion region.

[0136] As another example, there is an overlapping region between the insulating layer 52 and the positive electrode film layer 51, wherein the insulating layer 52 is located on the surface of the positive electrode film layer 51 in the overlapping region. In this case, the average thickness of the insulating layer 52 refers to the average thickness of the non-overlapping region.

[0137] As another example, there is a gap between the insulating layer 52 and the positive electrode film layer 51. That is, there are areas on the positive electrode body that are neither coated with an insulating layer nor with a positive electrode film layer.

[0138] In some embodiments, there may be both overlapping regions and gaps between the insulating layer 52 and the positive electrode film layer 51. For example, there may be an overlapping region between the insulating layer 52 and the positive electrode film layer 51 at one end along the first direction, and a gap between the insulating layer 52 and the positive electrode film layer 51 at the other end along the first direction.

[0139] In some embodiments, along the first direction, the area of ​​the negative electrode film layer 61 extending beyond the edge of the first portion 521 near the edge of the positive electrode tab has a size of 0.5 mm to 3 mm.

[0140] Along the first direction, the size H of the region where the edge of the negative electrode film layer 61 extends beyond the edge of the first portion 521 near the edge of 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.

[0141] When the area of ​​the negative electrode film layer 61 extending beyond the edge of the first portion 521 near the positive electrode tab along the first direction is greater than or equal to 0.5 mm, it facilitates the fabrication of the chamfered structure 62 and helps reduce the fabrication complexity of the negative electrode sheet 6. When the area of ​​the negative electrode film layer 61 extending beyond the edge of the first portion 521 near the positive electrode tab along the first direction is less than or equal to 3 mm, it helps reduce the risk of lithium plating and thus helps improve the cycle performance of the battery cell.

[0142] In some embodiments, along the first direction, the size of the chamfered structure 62 is smaller than the size of the region where the edge of the negative electrode film layer 61 extends beyond the edge of the first portion 521 near the edge of the positive electrode tab. This facilitates the fabrication of the chamfered structure 62, thereby helping to reduce the risk of leakage from the packaging bag caused by the negative electrode sheet 6 squeezing the packaging bag.

[0143] In some embodiments, the chamfer structure has a dimension of 0.5 mm to 1.5 mm along the first direction.

[0144] The dimension A of the chamfer structure along the first direction can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm or any value within the above range.

[0145] When the dimension of the chamfered structure along the first direction is greater than or equal to 0.5 mm, it helps to reduce the risk of leakage from the packaging bag caused by the negative electrode sheet squeezing the packaging bag; when the dimension of the chamfered structure along the first direction is less than or equal to 1.5 mm, it helps to improve the energy density of the battery cell.

[0146] 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.

[0147] When the sealing position of the battery cell packaging bag is parallel to the second direction (e.g., 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 chamfer structure 62 to be larger in the second direction than in the first direction, it is beneficial to reduce the risk of leakage caused by the negative electrode sheet 6 squeezing the packaging bag.

[0148] In some embodiments, the chamfer structure 62 has a dimension of 0.5 mm to 3 mm along the second direction.

[0149] The dimension B of the chamfer structure 62 along the second direction 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.

[0150] When the dimension 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 leakage of the packaging bag caused by the negative electrode sheet 6 squeezing the packaging bag; when the dimension 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 and it is beneficial to reduce the complexity of the preparation of the chamfered structure 62.

[0151] In some embodiments, the chamfer structure 62 is a rounded corner structure, which can be a concave structure or a convex structure.

[0152] In this embodiment, the chamfer structure 62 is a rounded corner structure, which is smoother and helps to further reduce the risk of the packaging bag breaking when subjected to squeezing or other forces, thereby improving the reliability of the battery cell.

[0153] Figure 7 This is a schematic diagram of the negative electrode sheet according to another embodiment of this application. (In conjunction with...) Figure 7 As shown, the chamfer structure 62 is a rounded corner structure, and the rounded corner structure is an outward convex structure.

[0154] In some embodiments, the rounded corner structure is a concave structure. This concave rounded corner structure, compared to an outward-convex structure, provides more space to avoid the packaging bag, further reducing the risk of the packaging bag breaking under pressure or other forces, thereby improving the reliability of the battery cell.

[0155] Figure 8 This is a schematic diagram of the negative electrode sheet according to another embodiment of this application. (In conjunction with...) Figure 8 As shown, the chamfered structure 62 can also be a right-angled structure. The angle between the extensions of the first and second sides can be any value other than 90°, such as 30°, 45°, or 60°.

[0156] 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 surface of a portion region of the positive electrode tab 502. This further enhances the protection against burrs, resulting in higher reliability of the battery cell.

[0157] In some embodiments, the positive electrode body portion 501 is provided with an insulating layer 52 at both ends along the first direction. The insulating layer 52 near the positive electrode tab includes a first portion 521 and a second portion 522, while the insulating layer 52 away from the positive electrode tab only includes the first portion.

[0158] In some embodiments, the negative electrode 6 includes a negative electrode tab 602, which is opposite to the positive electrode tab 502 along a first direction. This structural arrangement is advantageous for fabricating battery cells with larger dimensions in the length direction.

[0159] In some embodiments, the negative current collector 60 of the negative electrode sheet 6 includes a negative electrode body portion 601 and a negative electrode tab 602. The negative electrode tab 602 protrudes from the negative electrode body portion 601 along a first direction, and at least one side surface of the negative electrode body portion 601 is coated with a negative electrode film layer 61.

[0160] In some embodiments, the negative electrode 6 includes a negative electrode tab 602, which is opposite to the positive electrode tab 502 along a first direction. This structural arrangement is advantageous for fabricating battery cells with larger dimensions in the length direction.

[0161] In some embodiments, the negative electrode tab 602 may also be disposed on the same side as the positive electrode tab 502 along the first direction.

[0162] Figure 9This is a schematic diagram of a battery cell according to an embodiment of this application. In some embodiments, for example, combined with Figure 9 As shown, the battery cell 3 includes an electrode assembly 33, which includes a positive electrode and a negative electrode; 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 part; the battery cell 3 also includes an electrode lead 321, which passes through the two packaging films 310 and is electrically connected to the electrode assembly 33.

[0163] As an example, the battery cell includes two electrode leads: a positive lead for electrical connection to the positive tab 502 of the electrode assembly 33, and a negative lead for electrical connection to the negative tab 602 of the electrode assembly 33.

[0164] The battery cell with this structure is a pouch cell. The connection of two packaging films can form a sealed space inside the battery cell to accommodate the positive electrode, negative electrode and electrolyte. By electrically connecting the electrode leads to the electrode assembly, it is easy to draw out the current.

[0165] 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, and the insulating protective layer is disposed on the surface of the metal layer away from the electrode assembly. In this way, the electrode assembly and electrolyte can be sealed for protection, while also having a certain degree of flexibility to provide cushioning when the battery cell is subjected to compression or vibration.

[0166] In some embodiments, the material of the insulating protective layer may include nylon, the material of the metal layer may include aluminum or steel, and the material of the insulating connecting layer may include polypropylene.

[0167] In some embodiments, the packaging film can be an aluminum-plastic film, with the positive and negative electrode sheets housed within the space formed by the aluminum-plastic film. The battery cell with this structure is a pouch cell.

[0168] Aluminum-plastic film is a multi-layered composite flexible packaging material, which can be formed by laminating an outer layer of polymer (such as nylon or polyester), an intermediate layer of aluminum film (such as aluminum foil), and an inner layer of polymer (such as polypropylene or polyethylene). Compared with aluminum or steel shells, the battery cells made from aluminum-plastic film are soft-pack battery cells.

[0169] In some embodiments, a single battery cell includes multiple positive electrode plates 5 and multiple negative electrode plates 6, which are stacked together. This structure makes the battery cell a stacked battery cell, which is beneficial for improving the space utilization of the battery cell, thereby giving the battery cell a higher energy density.

[0170] In some embodiments, a single battery cell includes a positive electrode and multiple negative electrode plates. The positive electrode includes multiple straight positive segments and multiple bent positive segments. The straight positive segments are connected to the bent positive segments, and the multiple straight positive segments and multiple negative electrode plates are stacked.

[0171] In some embodiments, a battery cell includes a plurality of positive electrode plates and a negative electrode plate. The negative electrode plate includes a plurality of straight negative electrode sections and a plurality of bent negative electrode sections. The straight negative electrode sections and the bent negative electrode sections are connected, and the plurality of bent negative electrode sections and the plurality of positive electrode plates are stacked.

[0172] In a battery cell with stacked negative and positive electrodes, the battery cell includes an electrode assembly, which includes a negative electrode, a positive electrode, and a separator. The electrode assembly has little or no bending area. This type of battery cell can also be called a stacked battery cell.

[0173] In some embodiments, the insulating layer material includes inorganic particles and a binder. The inorganic particles include at least one of alumina, boehmite, and magnesium oxide. 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-trifluorochloroethylene copolymer.

[0174] Inorganic particles have a certain degree of insulation and can block burrs. The binder can bond the inorganic particles to the surface of the positive current collector, thereby facilitating the bonding between the insulating layer and the positive current collector.

[0175] In some embodiments, the insulating layer 52 is made of an organic material (e.g., an organic insulating layer), including at least one of polyacrylate and polyvinylidene fluoride. These materials all possess good insulating properties, which helps to prevent short circuits and thus improves the reliability of the battery cell.

[0176] In some embodiments, the electrolyte includes a solvent, which includes at least one of linear carbonates and linear carboxylic acid esters.

[0177] Linear carbonates can have the general formula RO-CO-OR', where R and R' are substituted or unsubstituted alkyl groups.

[0178] As an example, linear carbonates may include at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0179] Linear carboxylic acid esters can have the general formula R1-COO-R2, where R1 and R2 can be substituted or unsubstituted alkyl groups.

[0180] As an example, linear carboxylic acid esters may include at least one of methyl acetate, ethyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

[0181] Linear carbonates and linear carboxylic esters have low viscosity, and electrolytes containing these solvents also have low viscosity, which is beneficial for lithium-ion transport and thus helps improve the fast-charging performance of battery cells.

[0182] 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. The solvents described above have low viscosity, and the electrolyte containing these solvents has low viscosity, which is beneficial for lithium-ion transport, thereby improving the fast-charging performance of the battery cells.

[0183] In some embodiments, the sum of the mass contents of linear carbonates and linear carboxylic acid esters, based on the total mass of the electrolyte, is 10% to 90%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any value within the range above.

[0184] When the total mass content of linear carbonate and linear carboxylic acid ester is greater than or equal to 10% based on the total mass of the electrolyte, the electrolyte has a lower viscosity, which is beneficial for lithium-ion transport, and the battery cell has better fast-charging performance. When the total mass content of linear carbonate and linear carboxylic acid ester is less than or equal to 90% based on the total mass of the electrolyte, the gas production of linear carbonate and linear carboxylic acid ester in the battery cell can be reduced, thereby reducing the risk of gas accumulation between the separator and the positive electrode 5 and the negative electrode 6, reducing the risk of lithium plating, and improving the cycle performance of the battery cell.

[0185] In some embodiments, the sum of the mass contents of linear carbonate and linear carboxylic acid ester is 40% to 80% based on the total mass of the electrolyte. This provides a suitable range for the sum of the mass contents of linear carbonate and linear carboxylic acid ester, allowing the battery cell to achieve both good fast-charging performance and cycle performance.

[0186] In some embodiments, the solvent also includes cyclic carbonates.

[0187] Cyclic carbonates may include at least one of ethylene carbonate (EC) and propylene carbonate (PC).

[0188] Cyclic carbonates have a good ability to dissociate lithium ions. By combining cyclic carbonates with at least one of linear carbonates and linear carboxylic esters, it is beneficial to the transport of lithium ions in the electrolyte, thereby reducing the risk of lithium plating and improving the cycle performance of battery cells.

[0189] In the embodiments of this application, the types and contents of organic components in the electrolyte can be detected using equipment and methods known in the art. For example, the organic solvents in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents".

[0190] In the embodiments of this 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 electrolyte mass can be determined.

[0191] In some embodiments, the electrolyte comprises an electrolyte salt, which includes lithium hexafluorophosphate and lithium difluorosulfonylimide.

[0192] Lithium difluorosulfonylimide has a good ability to dissociate lithium ions. By combining lithium hexafluorophosphate and lithium difluorosulfonylimide, the electrolyte has a high ionic conductivity, which is conducive to the transport of lithium ions, reduces the risk of lithium plating, and improves the cycle performance of the battery cell.

[0193] In some embodiments, the total mass content of lithium hexafluorophosphate and lithium difluorosulfonylimide, based on the total mass of the electrolyte, is 12% to 20%, for example, it can be 12%, 13%, 15%, 16%, 18%, 19%, 20% or any value within the above range.

[0194] When the total mass content of lithium hexafluorophosphate and lithium difluorosulfonylimide is greater than or equal to 12% based on the total mass of the electrolyte, the electrolyte has a high ionic conductivity, which facilitates lithium-ion transport, helps reduce the risk of lithium plating, and improves the cycle performance of the battery cell. When the total mass content of lithium hexafluorophosphate and lithium difluorosulfonylimide is less than or equal to 20% based on the total mass of the electrolyte, the electrolyte has a suitable viscosity, which facilitates lithium-ion transport and helps improve the fast-charging performance of the battery cell.

[0195] In some embodiments, the mass ratio of lithium hexafluorophosphate to lithium difluorosulfonylimide is from 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 range above. This results in an electrolyte with high ionic conductivity, facilitating lithium-ion transport, reducing the risk of lithium plating, and improving the cycle performance of the battery cells.

[0196] In some embodiments, the electrolyte salt includes one of lithium hexafluorophosphate and lithium difluorosulfonylimide.

[0197] In the embodiments of this application, the types and contents of inorganic components / lithium salt concentrations in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the concentrations of inorganic components / lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis using the standard JY / T020-1996 "General Rules for Ion Chromatography Analysis".

[0198] In the embodiments of this application, a freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery cell can be used as a sample, or a battery cell that has been completely discharged (discharged to the lower limit cutoff voltage so that the battery's state of charge is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell can be used as a sample.

[0199] In some embodiments, the ratio of electrolyte mass to battery cell capacity is between 2.8 g / Ah and 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. This provides good wettability of the electrolyte to the positive electrode 5 and the negative electrode 6, which is beneficial for lithium-ion transport, thereby reducing the risk of lithium plating and improving the cycle performance of the battery cell.

[0200] In some embodiments, the ratio of electrolyte mass to battery cell capacity is 3.0 g / Ah to 3.2 g / Ah. This provides good wettability of the electrolyte to the positive electrode 5 and negative electrode 6, which is beneficial for lithium-ion transport, thereby reducing the risk of lithium plating and improving the cycle performance of the battery cell.

[0201] In some embodiments, the density of one side of the positive electrode 5 is 0.33 g / 1540.25 mm. 2 Up to 0.45g / 1540.25mm 2 For example, it could 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 20.44g / 1540.25mm 2 0.45g / 1540.25mm 2 Or any value within the above range.

[0202] The density on one side of the positive electrode 5 is greater than or equal to 0.33 g / 1540.25 mm. 2 Under these conditions, it is beneficial to improve the energy density of the battery cell; when the density of one side of the positive electrode 5 is less than or equal to 0.45g / 1540.25mm. 2 Under these conditions, it is beneficial for lithium-ion transport and helps improve the fast-charging performance of individual battery cells.

[0203] In some embodiments, the compaction density of the positive electrode 5 is 2.3 g / cm³. 3 Up to 2.65 g / cm 3 .

[0204] In this embodiment, 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 2.3 g / cm³. 3 2.32 g / cm 3 2.35g / cm 3 2.36 g / cm 3 2.38g / cm 3 2.4g / cm 3 2.42 g / cm 3 2.45g / cm 3 2.48 g / cm 3 2.5g / cm 3 2.52g / cm 3 2.55g / cm 3 2.58g / cm 3 2.6g / cm 3 2.62 g / cm 3 2.65g / cm 3 Or any value within the above range.

[0205] 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. Then, the positive and negative electrode sheets are removed from the battery cell, and the thickness of the electrode sheet and the current collector are measured respectively. The electrode sheet is then cut into small circular pieces 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 recorded as M1. Then, the film layer of the weighed electrode sheet is wiped off, and the weight of the current collector is recorded as M0. The density of one side is calculated as (M1 - M0) / S1. The compaction density is calculated as: density of one side / (electrode sheet thickness - current collector thickness). Furthermore, the compaction density of the negative electrode sheet can also be measured using the same method.

[0206] The compaction density of the positive electrode 5 is greater than or equal to 2.3 g / cm³. 3 Under these conditions, the battery cell has a high energy density; the compaction density of the positive electrode 5 is less than or equal to 2.65 g / cm³. 3 In this case, it facilitates the transport of lithium ions, which is beneficial to improving the fast charging performance of individual battery cells.

[0207] In some embodiments, the compaction density of the positive electrode 5 is 2.45 g / cm³. 3 Up to 2.6 g / cm 3 This approach helps to balance the energy density of individual battery cells and their fast-charging performance.

[0208] In some embodiments, the density of one side of the negative electrode 6 is 0.15 g / 1540.25 mm. 2 Up to 0.22g / 1540.25mm 2 .

[0209] The density of the negative electrode sheet on one side 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.

[0210] The density on one side of the negative electrode 6 is greater than or equal to 0.15 g / 1540.25 mm. 2Under these conditions, it is beneficial to improve the energy density of the battery cell; when the density of one side of the negative electrode 6 is less than or equal to 0.22g / 1540.25mm. 2 Under these conditions, it is beneficial for lithium-ion transport and helps improve the fast-charging performance of individual battery cells.

[0211] In some embodiments, the compaction density of the negative electrode sheet 6 is 1.3 g / cm³. 3 Up to 1.52 g / cm 3 .

[0212] In this embodiment, 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 1.3 g / cm³. 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.

[0213] The compaction density of the negative electrode sheet 6 is greater than or equal to 1.3 g / cm³. 3 Under these conditions, the battery cell has a high energy density; the compaction density of the negative electrode 6 is less than or equal to 1.52 g / cm³. 3 In this case, it facilitates the transport of lithium ions, which is beneficial to improving the fast charging performance of individual battery cells.

[0214] In some embodiments, the compaction density of the negative electrode sheet 6 is 1.35 g / cm³. 3 Up to 1.5g / cm 3 In this way, the negative electrode sheet 6 has a suitable compaction density, which is beneficial for balancing the energy density and fast charging performance of the battery cell.

[0215] In some embodiments, the positive electrode film 51 includes a positive electrode active material, which includes a lithium phosphate.

[0216] Lithium-containing phosphates can refer to lithium-containing transition metal phosphates with an olivine structure, such as lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their modified forms. The modification can be either doping or surface modification. For example, in doping modification, elements such as titanium can be doped into lithium iron phosphate; in surface modification, a coating layer can be applied to the surface of lithium iron phosphate.

[0217] Lithium phosphates have good structural stability, and lithium phosphate-containing battery cells have good cycle performance.

[0218] In some embodiments, the average longest diameter of the primary particles containing lithium phosphate is between 300 nm and 800 nm, for example, it can be 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 above range. This ensures that the lithium ion extraction path has a suitable distance, which is beneficial for improving the power performance of the battery cell.

[0219] In the embodiments of this application, a primary particle refers to the smallest unit of a particle within a certain observation range. A primary particle may contain defects of any form, 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 such aggregation is easily disaggregated under external forces such as ultrasound, stirring, and rolling, so that the main constituent morphology of the positive electrode active material in the film layer is still primary particles.

[0220] The longest diameter of a lithium phosphate is the longest straight line that passes through the center point of the lithium phosphate and extends to the outer periphery of the particle.

[0221] In the embodiments of this application, the average value of the longest diameter can be measured in the following manner.

[0222] The battery cell is disassembled to obtain the positive electrode sheet. The positive electrode sheet is cut along its thickness to expose the longitudinal section of the positive electrode film. The longest diameter of the lithium phosphate-containing particles is determined by scanning electron microscopy (SEM) of the longitudinal section of the positive electrode film. As an example, 30 lithium phosphate-containing particles are randomly selected from the longitudinal section image of the positive electrode film, and the longest diameter of each of the 30 particles is measured and averaged.

[0223] In some embodiments, the lithium phosphate includes a lithium phosphate matrix and a carbon coating layer that at least partially covers the surface of the lithium phosphate matrix. The carbon coating layer helps to improve the conductivity of the lithium phosphate, facilitating the utilization of the battery cell's capacity.

[0224] 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 improving the capacity of the battery cell. Furthermore, these doping elements also help increase the compaction density of the positive electrode 5, thereby improving the energy density of the battery cell.

[0225] In some embodiments, based on the total mass of lithium 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 suitable mass contents of the aforementioned doping elements, the battery cell exhibits high energy density, capacity, and cycle performance.

[0226] Based on the total mass of lithium phosphate, the mass content of Al can be 200ppm, 300ppm, 500ppm, 800ppm, 1000ppm, 1200ppm, 1500ppm, 1800ppm, 2000ppm, 2200ppm, 2400ppm, 2500ppm or any value within the above range; the mass content of V can be 300ppm, 500ppm, 800ppm, 1000ppm, 1200ppm, 1500ppm, 1800ppm, 2000ppm or any value within the above range; and the mass content of Ti can be 1500ppm, 1800ppm, 2000ppm, 2200ppm, 2400ppm, 2500ppm, 2800ppm, 3000ppm, 3200ppm, 3500ppm or any value within the above range.

[0227] The elements and their contents in the positive electrode active material can be determined 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 X-Max-50mm2)).

[0228] As an example, the battery cell was discharged at a constant current of 0.33C to 2.0V at 25°C to obtain a battery cell with 0% SOC. Then, the positive electrode was removed from the battery cell, and a longitudinal cross-section of the positive electrode film was obtained using an ion section polisher. The cross-section of the positive electrode active material particles was then scanned using a scanning electron microscope to test the elements and their content.

[0229] In some embodiments, the lithium phosphate-containing cathode active material includes at least one of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4. The aforementioned lithium phosphate-containing cathode active materials exhibit high structural stability, which helps to improve the cycle life of individual battery cells.

[0230] During the charging and discharging process, lithium (Li) undergoes insertion / extraction and consumption within a single battery cell. The molar content of Li in the positive electrode active material varies depending on the discharge state of the cell. In the examples of positive electrode active materials in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar content of Li changes when the positive electrode active material is applied to the battery system. Similarly, the molar content of O in the examples of positive electrode active materials in this application is only an ideal value. Oxygen release from the crystal lattice causes changes in the molar content of O, resulting in fluctuations in the actual molar content of O.

[0231] In some embodiments, the negative electrode film 61 includes a negative electrode active material, which includes graphite, and at least a portion of the surface of the graphite has a coating layer comprising amorphous carbon. This facilitates the rapid intercalation of lithium ions into the graphite, thereby improving the fast-charging performance of the battery cell.

[0232] In some embodiments, the thickness of the coating layer is from 100 nm to 500 nm, for example, it can be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm or any value within the above range. This coating layer has a suitable thickness, facilitating lithium-ion insertion and transport, and improving the fast-charging performance of the battery cell.

[0233] In some embodiments, the graphite comprises secondary particles. This facilitates lithium-ion transport and improves the fast-charging performance of individual battery cells.

[0234] In some embodiments, the graphitization degree of graphite is 90% to 94%, for example, it can be 90%, 91%, 92%, 93%, 94% or any value within the above range. Thus, graphite with a suitable graphitization degree is beneficial for achieving a suitable specific capacity and for controlling side reactions in the battery cell within a suitable range, thereby resulting in a battery cell with suitable capacity and cycle life.

[0235] In some embodiments, the volume average particle size Dv50 of graphite is 15 μm to 25 μm. This appropriate range of graphite particle size is beneficial for increasing the compaction density of the negative electrode sheet 6, thereby improving the energy density of the battery cell.

[0236] The volume average particle size (Dv50) of graphite represents the particle size corresponding to a cumulative volume distribution percentage of 50%, and can be determined using instruments and methods known in the art. As an example, a battery cell is disassembled to obtain the negative electrode sheet. The negative electrode film layer is scraped off to obtain powder of the negative electrode film layer. This powder is then mixed with water, filtered, and dried to obtain graphite. Subsequently, the particle size is conveniently determined using a laser particle size analyzer according to GB / T19077-2016, Laser Diffraction Method for Particle Size Distribution. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0237] The volume average particle size Dv50 of 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.

[0238] In some embodiments, the volume average particle size Dv50 of graphite is 16 μm to 20 μm. This appropriate range of graphite particle size is beneficial for increasing the compaction density of the negative electrode sheet 6, thereby improving the energy density of the battery cell.

[0239] In some embodiments, the electrolyte includes additives, including at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propane sulpholactone (PS). These additives facilitate film formation at the negative electrode, reduce side reactions at the negative electrode, and thus improve the cycle life, kinetics, and other performance characteristics of the battery cell.

[0240] In some embodiments, based on the total mass of the electrolyte, the mass content of the additive is less than or equal to 5%, for example, it can be 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 above range. The above-mentioned additives have suitable mass content, which is beneficial to improving the cycle life, kinetics, and other performance characteristics of the battery cells.

[0241] In some embodiments, the additive content is 0.5% to 3% by mass, based on the total mass of the electrolyte. The appropriate mass content of the additive is beneficial for improving the cycle life, kinetics, and other performance characteristics of the battery cells.

[0242] In some embodiments, the battery cell further includes a separator membrane disposed between the positive electrode 5 and the negative electrode 6. The separator membrane includes a base film with a thickness of 5 μm to 9 μm, for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 8.5 μm, 9 μm or any value within the above range.

[0243] When the thickness of the base film is greater than or equal to 5 μm, the separator has high strength, which can reduce the risk of lithium dendrites puncturing the separator and causing internal short circuits in the battery cell; when the thickness of the base film is less than or equal to 9 μm, it is beneficial to reduce the space occupied by the separator, and the battery cell has high energy density.

[0244] In some embodiments, the porosity of the separator is 40% to 55%, for example, it can be 40%, 42%, 45%, 48%, 50%, 52%, 55% or any value within the above range. This facilitates the wetting of the separator by the electrolyte, which is beneficial for lithium ion transport, thereby reducing the risk of lithium plating and resulting in better cycle performance of the battery cell.

[0245] [Battery Device]

[0246] This application provides a battery device, including the battery cell in any of the above embodiments.

[0247] Figure 10 This is a schematic diagram of a battery device according to an embodiment of this application. For example, such as... Figure 10 As shown, the battery device 10 of this application embodiment may include a plurality of battery cells 3 to meet different power usage requirements. The shape of the battery cell 3 in this application embodiment can be set according to actual application. For example, the battery cell 3 can be cylindrical, or it can be cuboid or other shapes, and this application embodiment is not limited to this.

[0248] The battery device 10 of this embodiment may further include a housing 11, which can be used to accommodate multiple battery cells 3. The housing 11 of this embodiment has a hollow interior, and the multiple battery cells 3 are accommodated within the housing 11. The housing 11 may include two parts, referred to herein as a first housing portion 111 and a second housing portion 112, which are fastened together. The shapes of the first housing portion 111 and the second housing portion 112 can be determined according to the shape of the components housed inside, for example, according to the shape of the combination of the multiple battery cells 3 housed inside. At least one of the first housing portion 111 and the second housing portion 112 has an opening. For example, as... Figure 10As shown, the first housing portion 111 and the second housing portion 112 can both be hollow cuboids with one open side each. The openings of the first housing portion 111 and the second housing portion 112 are opposite to each other, and the first housing portion 111 and the second housing portion 112 are interlocked to form a housing 11 with a closed chamber, which can be used to accommodate multiple battery cells 3. The multiple battery cells 3 are connected in parallel, series, or mixed and placed inside the housing 11 formed by the interlocking of the first housing portion 111 and the second housing portion 112.

[0249] For example, unlike Figure 10 As shown, either the first housing portion 111 or the second housing portion 112 may have only one hollow cuboid with an opening, while the other is plate-shaped to cover the opening. Taking the second housing portion 112 as a hollow cuboid with one opening and the first housing portion 111 as a plate-shaped example, then the first housing portion 111 covers the opening of the second housing portion 112 to form a housing 11 with a closed chamber, which can be used to accommodate multiple battery cells 3.

[0250] Figure 11 This is a schematic diagram illustrating the interaction between a single battery cell and a thermal management component according to an embodiment of this application. Figure 12 This is a schematic diagram illustrating the interaction between a battery cell and a thermal management component according to another embodiment of this application. In some embodiments, combined with Figures 10 to 12 As shown, the battery device includes: a housing 11; a plurality of battery cells 3, which are housed within the housing 11 and stacked along a third direction, each battery cell having a rated capacity greater than or equal to 100 Ah, each battery cell having a surface including a first surface 301 and a second surface 302, the area of ​​the first surface being greater than the area of ​​the second surface, the first surfaces of the plurality of battery cells being arranged opposite each other along a third direction; and a thermal management component 91 for regulating the temperature of the plurality of battery cells, the thermal management component being arranged opposite to the second surfaces of the plurality of battery cells along a fourth direction, the fourth direction being perpendicular to the third direction.

[0251] The third direction can be Figure 11 and Figure 12 In the X direction, the fourth direction can be Figure 11 and Figure 12 The Z direction in the equation.

[0252] Each battery cell 3 may include two first surfaces 301 and two second surfaces 302, with the two first surfaces 301 facing each other along the X direction and the two second surfaces 302 facing each other along the second direction.

[0253] As an example, the first surface 301 is the surface with the largest surface area of ​​the battery cell.

[0254] As an example, the electrode terminals of the battery cell 3 are disposed on the first surface 301.

[0255] In this embodiment, the rated capacity of each battery cell is greater than or equal to 100Ah. During the charging and discharging process of the battery cell, a lot of heat will be generated. 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 the battery cell temperature being too high.

[0256] In some embodiments, the battery device further includes a retaining adhesive 92 disposed between the thermal management component and the battery cell, which is used to fix the battery cell to the thermal management component. This facilitates the fixation between the battery cell and the thermal management component.

[0257] In some embodiments, such as Figure 11 As shown, the adhesive 92 is directly attached to the packaging bag. In other words, the adhesive 92 is directly connected to the packaging bag of the battery cell 3, which helps to improve the energy density of the battery device.

[0258] In this embodiment, the adhesive 92 is directly attached to the packaging bag, and the battery cells in the battery device are arranged one on top of the other, which eliminates the need for a component that fixes multiple battery cells together.

[0259] Figure 13 This is a schematic diagram of a battery module according to an embodiment of this application. In some embodiments, such as... Figure 12 and Figure 13 As shown, the battery device also includes a housing 801, which houses at least one battery cell, and adhesive 92 is directly attached to the wall of the housing 801. The housing 801 facilitates better heat dissipation from the battery cell, which helps to reduce the temperature of the battery cell.

[0260] In this embodiment, the battery device includes at least one battery module 80, which includes a housing 801 and a plurality of battery cells.

[0261] As an example, the housing 801 has a U-shaped form. For instance, the housing 801 includes a first wall 8011, a second wall 8012, and a third wall 8013, with the two ends of the second wall 8012 extending in the direction of extension connected to the first wall 8011 and the third wall 8013, respectively. As an example, the first wall 8011 and the third wall 8013 extend in the Z direction, and the second wall 8012 extends in the X direction.

[0262] As an example, the adhesive 92 is directly attached to the first wall 8011 and the third wall 8013 of the housing 801.

[0263] [Electrical Equipment]

[0264] This application provides an electrical device, including a battery cell or a battery device as described in any of the above embodiments, wherein the battery cell or battery device is used to store or provide electrical energy.

[0265] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use battery devices.

[0266] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical equipment.

[0267] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0268] For example, such as Figure 14 The diagram shown is a schematic representation of a vehicle according to one embodiment of this application. Vehicle 1 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A motor 40, a controller 30, and a battery device 10 can be installed inside vehicle 1. The controller 30 controls the battery device 10 to supply power to the motor 40. For example, the battery device 10 can be installed at the bottom, front, or rear of vehicle 1. The battery device 10 can be used to power vehicle 1. For example, the battery device 10 can serve as the operating power source for vehicle 1, for example, to meet the electrical system requirements of vehicle 1, such as for starting, navigation, and operation. In another embodiment of this application, the battery device 10 can not only serve as the operating power source for vehicle 1 but also as the driving power source for vehicle 1, replacing or partially replacing gasoline or natural gas to provide driving power for vehicle 1.

[0269] [Positive electrode plate]

[0270] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0271] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As an example, the positive electrode active material may include one or more of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional 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 include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.1 Al 0.05 One or more of the following: O2) and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0272] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption. The molar content of Li in the positive electrode active material varies depending on the discharge state. In the examples of positive electrode active materials in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. After charge-discharge cycles, the molar content of Li changes when the positive electrode active material is applied to the battery system. Similarly, the molar content of O in the examples of positive electrode active materials in this application is only an ideal value. Oxygen release from the crystal lattice causes changes in the molar content of O, and the actual molar content of O will fluctuate.

[0273] 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), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0274] In some embodiments, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0275] [Negative electrode plate]

[0276] In some embodiments, the negative electrode current collector can be a metal foil or a composite negative electrode current collector. The negative electrode current collector can be a copper foil. The composite negative electrode current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0277] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be any negative electrode active material known in the art for use in batteries. 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, etc. The silicon-based material may 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 may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0278] The negative electrode film layer may also optionally include a binder. As an example, the binder may include at least one of styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC-Na), water-soluble unsaturated resin SR-1B, waterborne 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).

[0279] The negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0280] In one embodiment, the negative electrode sheet can be prepared by forming a negative electrode slurry using the components described above. 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 a negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained.

[0281] [Isolation Component]

[0282] The separator is used to separate the positive electrode and the negative electrode. This application does not impose any particular restrictions on the type of separator; for example, any known porous membrane with good chemical and mechanical stability can be selected.

[0283] In one embodiment, the material of the separator may include one or more of glass fiber, nonwoven 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.

[0284] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0285] [Example]

[0286] Example 1

[0287] (1) Preparation of negative electrode sheet

[0288] Artificial graphite (anode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) (thickener) 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 then uniformly coated onto both sides of the copper foil (anode current collector), followed by drying, cold pressing, and slitting to obtain the negative electrode sheet. The artificial graphite had a volume average particle size (Dv50) of 18 μm, and the compaction density of the negative electrode film was 1.4 g / cm³ when the battery cell was at 0% SOC. 3 The single-sided density of the negative electrode film is 0.17 g / 1540.25 mm. 2 .

[0289] The connection between the first and second sides of the negative electrode sheet is provided with a chamfer structure. The dimension A of the chamfer structure is 1 mm along the first direction and the dimension B of the chamfer structure is 1.5 mm along the second direction.

[0290] (2) Preparation of positive electrode sheet

[0291] Lithium iron phosphate (LiFePO4), carbon black (CNY), and polyvinylidene fluoride (PVDF) (PVDF) (PVDF) were mixed thoroughly in an N-methylpyrrolidone (NMP) solvent system at a mass ratio of 97:1.0:2.0 to obtain a positive electrode slurry. Inorganic alumina particles and PVDF (PVDF) were mixed thoroughly in an N-methylpyrrolidone (NMP) solvent system to obtain an insulating slurry. The positive electrode slurry and the insulating slurry were uniformly coated on both sides of the positive electrode current collector aluminum foil to obtain a positive electrode sheet with a positive electrode film layer and an insulating layer. The electrode tabs were then cut to obtain the positive electrode sheet.

[0292] The positive current collector includes a positive electrode body and a positive electrode tab, with the positive electrode tab protruding from the body along a first direction. The positive electrode body includes a coating area and a transition area, with the transition area located between the coating area and the positive electrode tab. A positive electrode film is disposed on both sides of the coating area, and an insulating layer is disposed at both ends of the positive electrode film along the first direction. The insulating layer near the positive electrode tab along the first direction includes a first part and a second part. The first part is disposed on both sides of the coating area, and the second part is disposed on both sides of a portion of the positive electrode tab. The first part and the second part are connected. Along the first direction, the width D1 of the first part is 2 mm, and the average thickness D2 of the insulating layer is 30 μm.

[0293] Along the first direction, the dimension H of the first portion of the negative electrode film extending beyond the insulating layer is 1.5 mm.

[0294] With the battery cell at 0% SOC, the compaction density of the positive electrode film is 2.5 g / cm³. 3 The single-sided density of the positive electrode film is 0.38 g / 1540.25 mm.2 .

[0295] (3) Preparation of electrolyte

[0296] In an argon atmosphere glove box (H2O content <10ppm, O2 content <1ppm), the electrolyte salt lithium hexafluorophosphate LiPF6 and lithium difluorosulfonyl imide were dissolved in a mass ratio of 2:1 in a mixture of organic solvents dimethyl carbonate (DMC), ethyl acetate (EA), ethyl methyl carbonate (EMC), and ethylene carbonate (EC). Ethylene carbonate (VC) was then added and stirred until homogeneous.

[0297] 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%.

[0298] (4) Separating membrane

[0299] The separator includes a base film, which is a polyethylene (PE) film with a thickness of 7 μm.

[0300] (5) Preparation of battery cells

[0301] The positive electrode, separator, and negative electrode are stacked according to the stacking process, with the separator positioned between the positive and negative electrodes to isolate them. The electrode assembly is placed in an aluminum-plastic film, and electrolyte is injected. After vacuum sealing, settling, formation, and shaping, a single battery cell is obtained.

[0302] Example 2-3

[0303] The difference between Examples 2-3 and Example 1 is that the size H of the first part of the negative electrode film layer extending beyond the insulating layer along the first direction is different.

[0304] Examples 4-5

[0305] The difference between Examples 4-5 and Example 1 is that the width D1 of the first part of the insulating layer is different along the first direction.

[0306] Examples 6-7

[0307] The difference between Examples 6-7 and Example 1 is that the average thickness D2 of the insulating layer is different.

[0308] Examples 8-11

[0309] The difference between Examples 8-11 and Example 1 is that the ionic conductivity of the electrolyte is different.

[0310] In Example 8, based on the total mass of the electrolyte, the mass content of LiPF6 was 9.6%, the mass content of LIFSI was 4.8%, the mass content of dimethyl carbonate (DMC) was 8.6%, the mass content of ethyl methyl carbonate (EMC) was 41.1%, the mass content of ethylene carbonate (EC) was 32.5%, and the mass content of vinylene carbonate (VC) was 3.4%.

[0311] In Example 9, based on the total mass of the electrolyte, the mass content of LiPF6 was 9.6%, the mass content of LIFSI was 4.8%, the mass content of dimethyl carbonate (DMC) was 24.8%, the mass content of ethyl acetate was 16.3%, the mass content of ethyl methyl carbonate (EMC) was 24.8%, the mass content of ethylene carbonate (EC) was 16.3%, and the mass content of vinylene carbonate (VC) was 3.4%.

[0312] In Example 10, based on the total mass of the electrolyte, the mass content of LiPF6 was 9.6%, the mass content of LIFSI was 4.8%, the mass content of dimethyl carbonate (DMC) was 8.6%, the mass content of ethyl acetate was 41%, the mass content of ethyl methyl carbonate (EMC) was 4.4%, the mass content of ethylene carbonate (EC) was 28.2%, and the mass content of vinylene carbonate (VC) was 3.4%.

[0313] In Example 11, based on the total mass of the electrolyte, the mass content of LiPF6 was 9.6%, the mass content of LIFSI was 4.8%, the mass content of ethyl acetate was 75.4%, the mass content of ethylene carbonate EC was 6.8%, and the mass content of vinylene carbonate VC was 3.4%.

[0314] Comparative Example 1

[0315] The difference between Comparative Example 1 and Example 1 is that the connection between the first and second sides of the negative electrode sheet is not chamfered.

[0316] Comparative Example 2

[0317] 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 part of the insulating layer, and H is 0.

[0318] Comparative Example 3

[0319] The difference between Comparative Example 3 and Example 1 is 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%.

[0320] Comparative Example 4

[0321] The difference between Comparative Example 4 and Example 1 is 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%.

[0322] Table 1. Data from the Examples and Comparative Examples

[0323]

[0324] In Table 1, H is the dimension of the region along the first direction where the edge of the negative electrode film extends beyond the edge of the first portion near the edge of the positive electrode tab; D1 is the dimension of the first portion along the first direction; and D2 is the average thickness of the insulating layer.

[0325] Table 2 Data from some embodiments

[0326]

[0327] Table 3 Data from some embodiments

[0328]

[0329] In this embodiment, the cycle performance of a battery cell is reflected by the number of cycles in which the discharge capacity of the battery cell decays to 80% of the first discharge capacity. The more cycles, the better the cycle performance of the battery cell. The reliability of a battery cell is reflected by whether the battery cell leaks liquid. The leakage of a battery cell can be reflected by the thickness increase rate of the battery cell after heating at 60°C.

[0330] 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, and providing a chamfered structure at the connection between the first and second sides of the negative electrode sheet, and with the electrolyte having an ionic conductivity of 8.5 ms / cm to 20 ms / cm, the battery cell can achieve both good cycle performance and high reliability.

[0331] As shown in Examples 1-3, the size H of the region where the edge of the negative electrode film extends beyond the edge of the first part along the first direction is set to be 0.5 mm to 3 mm. This allows the battery cell to achieve good cycle performance, high energy density, and high reliability.

[0332] As shown in Embodiment 1 and Embodiments 4-5, the first part of the insulating layer is provided with a dimension D1 of 1mm to 3mm along the first direction, so that the battery cell can achieve good cycle performance, high energy density and high reliability.

[0333] As shown in Examples 1 and 6-7, by setting the thickness of the insulating layer to 10μm to 50μm, the battery cell can achieve good cycle performance, high energy density, and high reliability.

[0334] As shown in Examples 1 and 8-11, the ionic conductivity of the electrolyte is 8.5 ms / cm to 20 ms / cm, and the battery cell can achieve both good cycle performance and high reliability.

[0335] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

[0336] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0337] 1. Cyclic performance testing

[0338] At 45℃, the battery cell is charged at a constant current of 0.5C to 3.65V, then charged at a constant voltage to 0.05C, left to stand for 10 minutes, and then discharged at a constant current of 1C to 2.0V. This constitutes one charge-discharge cycle. The discharge capacity of the first cycle is recorded. After standing for 10 minutes, the above charge-discharge cycle is repeated until the discharge capacity of the battery cell decreases to 80% of the discharge capacity of the first cycle. The number of cycles is recorded.

[0339] 2. Leakage test

[0340] At 25°C, the thickness of the battery cell is measured as H0. The battery cell is placed on a metal plate at 60°C and heated. After 2 hours, the thickness of the battery cell is measured as H1. If the thickness increase rate (H1-H0) / H0 < 5%, leakage is considered.

[0341] 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.

[0342] 3. Energy density test

[0343] At 25℃, the battery cell is charged at a constant current of 0.33C to the cutoff voltage of 3.65V, then charged at a constant voltage to ≤0.05C, and then discharged at a constant current of 0.33C to the cutoff voltage of 2.0V. The discharge energy E0 and discharge capacity C0 are recorded. The cell dimensions (maximum outer contour length, width and thickness) are measured, and the cell volume V0 is calculated. The energy density of the battery cell is E0 / V0, in Wh / L.

[0344] 4. Self-discharge test

[0345] At 25±2℃, the battery cells were discharged to adjust to 30% SOC. After standing for 12 hours, the initial voltage V0 was recorded. At the same temperature, the cells were left to stand for another 48 hours, and the final voltage V1 was 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, a negative electrode, an electrolyte, and a packaging bag, wherein the positive electrode, the negative electrode, and the electrolyte are contained within the packaging bag; The positive electrode sheet includes a positive current collector, a positive electrode film layer, and an insulating layer. The positive current collector includes a positive electrode body portion and a positive electrode tab. The positive electrode tab protrudes from the positive electrode body portion along a first direction. The positive electrode body portion 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 disposed on at least one side surface of the coating area. The insulating layer includes a first portion, which is disposed on at least one side surface of the transition area. The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side surface of the negative current collector, wherein, along the first direction, the edge of the negative electrode film layer extends beyond the edge of the first portion near the positive electrode tab; wherein... The connection between the first and second sides of the negative electrode sheet is provided with a chamfer structure. The first side extends along the first direction, and the second side extends along the second direction. The first direction and the second direction are perpendicular to the thickness direction of the negative electrode sheet. The electrolyte has an ionic conductivity of 8.5 mS / cm to 20 mS / cm. The average thickness of the insulating layer is 10 μm to 50 μm. Along the first direction, the size of the chamfered structure is smaller than the size of the region where the edge of the negative electrode film extends beyond the first portion near the edge of the positive electrode tab.

2. The battery cell according to claim 1, characterized in that, The electrolyte has an ionic conductivity of 12 ms / cm to 16 ms / cm.

3. The battery cell according to claim 1, characterized in that, Along the first direction, the size of the first portion is 1 mm to 3 mm.

4. The battery cell according to claim 1, characterized in that, Along the first direction, the area of ​​the negative electrode film layer extending beyond the edge of the first portion near the edge of the positive electrode tab has a size of 0.5 mm to 3 mm.

5. The battery cell according to claim 1, characterized in that, The chamfered structure has a dimension of 0.5 mm to 1.5 mm along the first direction.

6. The battery cell according to claim 1, characterized in that, The dimension of the chamfered structure along the second direction is greater than the dimension of the chamfered structure along the first direction.

7. The battery cell according to claim 1, characterized in that, The chamfered structure has a dimension of 0.5 mm to 3 mm along the second direction.

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

9. The battery cell according to claim 8, characterized in that, The rounded corner structure is a concave structure.

10. The battery cell according to claim 1, characterized in that, 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 portion region of the positive electrode tab.

11. The battery cell according to claim 1, characterized in that, The negative electrode plate includes a negative electrode tab, and the negative electrode tab and the positive electrode tab are opposite each other along the first direction.

12. The battery cell according to claim 1, characterized in that, The battery cell includes an electrode assembly, which includes the positive electrode and the negative electrode. 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 electrode leads that pass between the two packaging films and are electrically connected to the electrode assembly.

13. The battery cell according to claim 12, characterized in that, 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, and the insulating protective layer is disposed on the surface of the metal layer away from the electrode assembly.

14. The battery cell according to claim 1, characterized in that, The electrolyte includes a solvent, which includes at least one of linear carbonates and linear carboxylic acid esters.

15. The battery cell according to claim 14, 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.

16. The battery cell according to claim 14, 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%.

17. 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 40% to 80%.

18. The battery cell according to claim 14, characterized in that, The solvent also includes cyclic carbonates.

19. 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 from 2.8 g / Ah to 3.5 g / Ah.

20. The battery cell according to claim 19, 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.

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

22. The battery cell according to claim 1, characterized in that, The compaction density of the positive electrode sheet is 2.3 g / cm³. 3 Up to 2.65 g / cm 3 .

23. The battery cell according to claim 22, characterized in that, The compaction density of the positive electrode sheet is 2.45 g / cm³. 3 Up to 2.6 g / cm 3 .

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

25. The battery cell according to claim 1, characterized in that, The compaction density of the negative electrode sheet is 1.3 g / cm³. 3 Up to 1.52 g / cm 3 .

26. The battery cell according to claim 25, characterized in that, The compaction density of the negative electrode sheet is 1.35 g / cm³. 3 Up to 1.5g / cm 3 .

27. The battery cell according to claim 1, characterized in that, The positive electrode film layer includes a positive electrode active material, which includes a lithium phosphate.

28. The battery cell according to claim 27, characterized in that, The average longest diameter of the primary particles containing lithium phosphate is between 300 nm and 800 nm.

29. The battery cell according to claim 28, 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.

30. The battery cell according to claim 29, characterized in that, The lithium-containing phosphate matrix includes lithium iron phosphate, which is doped with at least one of Al, V, and Ti.

31. The battery cell according to claim 30, characterized in that, Based on the total mass of the lithium 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.

32. 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, and at least a portion of the surface of the graphite has a coating layer, the coating layer including amorphous carbon.

33. The battery cell according to claim 32, characterized in that, The thickness of the coating layer is 100 nm to 500 nm.

34. The battery cell according to claim 32, characterized in that, The graphite comprises secondary particles.

35. The battery cell according to claim 32, characterized in that, The graphite has a graphitization degree of 90% to 94%.

36. The battery cell according to claim 32, characterized in that, The volume average particle size Dv50 of the graphite is 15 μm to 25 μm.

37. The battery cell according to claim 36, characterized in that, The volume average particle size Dv50 of the graphite is 16 μm to 20 μm.

38. The battery cell according to claim 1, characterized in that, The electrolyte includes additives, which include at least one of vinylene carbonate, fluoroethylene carbonate, and 1,3-propane sulpholactone.

39. The battery cell according to claim 38, characterized in that, Based on the total mass of the electrolyte, the mass content of the additive is less than or equal to 5%.

40. The battery cell according to claim 39, characterized in that, The additive has a mass content of 0.5% to 3% based on the total mass of the electrolyte.

41. A battery device, characterized in that, include: Multiple battery cells according to any one of claims 1-40.

42. The battery device according to claim 41, characterized in that, The battery device includes: Box; A plurality of battery cells are housed in the housing and 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. The first surfaces of the plurality of battery cells are arranged opposite to each other along the third direction. A thermal management component for regulating the temperature of a plurality of battery cells, the thermal management component being disposed opposite to the second surface of the plurality of battery cells along a fourth direction, the fourth direction being perpendicular to the third direction.

43. The battery device according to claim 42, characterized in that, The battery device also 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.

44. The battery device according to claim 43, characterized in that, The adhesive is directly attached to the packaging bag.

45. The battery device according to claim 43, characterized in that, The battery device further includes a housing containing at least one of the battery cells, and the adhesive is directly attached to the wall of the housing.

46. ​​An electrical appliance, characterized in that, include: A plurality of battery cells according to any one of claims 1-40, or a battery device according to any one of claims 41-45, wherein the battery cells or battery devices are used to store or provide electrical energy.

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