Battery cell, battery device, and electric device

Abstract

The embodiment of the application discloses a battery monomer, a battery device and a power utilization equipment. The battery monomer comprises a shell, the shell comprises a shell body, a positive electrode end cover assembly and a negative electrode end cover assembly; an electrode assembly, the electrode assembly comprises a positive electrode sheet and a negative electrode sheet arranged along the thickness direction of the battery monomer, and the electrode assembly is a laminated structure; the electrode assembly comprises a main body part and a tab part located at the end face of the main body part, the size of the main body part in the first direction is greater than 400 mm, the size of the main body part in the thickness direction of the battery monomer is less than 20 mm, the first direction is the extension direction of the longest side of the electrode assembly; the main body part comprises a first side face and a second side face, the first side face is the largest area face of the electrode assembly, and the area ratio of the first side face to the second side face is greater than 6; the single surface area density of the positive electrode film layer of the positive electrode sheet is greater than 375 mg / 1540.25 mm 2 The battery monomer provided by the application considers both high energy density and reliability.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit from PCT patent application No. PCT / CN2025 / 133519 entitled “Battery Cell, Battery Device and Electrical Equipment”, filed on November 7, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] 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

[0004] The new energy industry is attracting increasing attention. Within this industry, battery technology is a crucial factor in its development.

[0005] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, lifespan, capacity, fast charging performance, and reliability. Therefore, how to provide a battery cell that balances high energy density and high reliability is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell that combines high energy density and high reliability.

[0007] To achieve the above objectives, this application provides a battery cell, a battery device, and an electrical appliance.

[0008] In a first aspect, a battery cell is provided, comprising: a housing, the housing including a shell, a positive terminal cover assembly, and a negative terminal cover assembly, the positive terminal cover assembly and the negative terminal cover assembly being used to cover an opening of the shell; an electrode assembly, wherein an accommodating space is formed within the shell to accommodate the electrode assembly, the electrode assembly including a positive electrode sheet and a negative electrode sheet disposed along the thickness direction of the battery cell, the electrode assembly being a stacked structure; the electrode assembly including a main body portion and an electrode tab portion located on an end face of the main body portion, the main body portion having a dimension greater than 400 mm in a first direction, and a dimension less than 20 mm in the thickness direction of the battery cell, the first direction being the extension direction of the longest side of the electrode assembly; the main body portion including a first side surface and a second side surface extending along the first direction, the first side surface being the surface with the largest area of ​​the electrode assembly, the ratio of the area of ​​the first side surface to the area of ​​the second side surface being greater than 6; the positive electrode sheet including a positive current collector and a positive electrode film layer located on at least one side of the positive current collector, the single-sided areal density of the positive electrode film layer being greater than 375 mg / 1540.25 mm². 2 .

[0009] In this embodiment, the areal density of the positive electrode film layer on one side of the positive electrode sheet is set to be greater than 375 mg / 1540.25 mm. 2 This invention employs a thick coating method to improve the energy density of individual battery cells. Simultaneously, it utilizes a stacked electrode assembly, which typically lacks a winding structure and corners, thus improving space utilization and further enhancing the energy density of the battery cells. However, a thick coating on the positive electrode increases the impedance of the battery cell, leading to increased heat generation, accelerated aging, and an increased risk of thermal runaway. Therefore, the electrode assembly's main body is designed with a length greater than 400mm, a thickness less than 20mm, and a ratio of the area of ​​the large surface (first side) to the other sides greater than 6. This results in a larger large surface area and a thinner electrode assembly, facilitating heat dissipation in the thickly coated battery cells. This addresses the issues of accelerated aging or increased thermal runaway risk caused by high heat generation in thickly coated battery cells, improving their reliability. Therefore, the technical solution of this application can improve the reliability of battery cells while maintaining high energy density, providing a battery cell with excellent overall performance.

[0010] In one possible implementation, the main body has a dimension of 450mm to 650mm in the first direction.

[0011] In one possible implementation, the main body portion has a dimension of 13mm to 18mm in the thickness direction of the battery cell.

[0012] In one possible implementation, the ratio of the area of ​​the first side to the area of ​​the second side is 7 to 10. This further increases the surface area of ​​the electrode assembly, improving the heat dissipation performance of the high-energy-density battery cell.

[0013] In one possible implementation, the areal density of the positive electrode film is 380 mg / 1540.25 mm². 2 ~420mg / 1540.25mm 2 This will further help improve the energy density of individual battery cells.

[0014] In one possible implementation, the negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector, wherein the one-sided areal density of the negative electrode film layer is 165 mg / 1540.25 mm². 2 ~185mg / 1540.25mm 2 .

[0015] Setting the surface density of the negative electrode film within the above range is beneficial to improving the energy density of the battery cell.

[0016] In one possible implementation, the battery cell satisfies at least one of the following conditions: (1) the ratio of the thickness of the negative electrode film to the thickness of the negative electrode current collector is greater than 12; (2) the ratio of the thickness of the positive electrode film to the thickness of the positive electrode current collector is greater than 6.5.

[0017] In one possible implementation, the battery cell satisfies at least one of the following conditions: (1) the ratio of the thickness of the negative electrode film to the thickness of the negative electrode current collector is 13 to 18; (2) the ratio of the thickness of the positive electrode film to the thickness of the positive electrode current collector is 7 to 9.

[0018] Setting the ratio of the thickness of the positive electrode film / negative electrode film to the thickness of the positive electrode current collector / negative electrode current collector within the above range is beneficial to improving the energy density of the battery cell.

[0019] In one possible implementation, when the battery cell is at 0% SOC, the compaction density of the positive electrode sheet is 2.3 g / cm³. 3 ~2.65g / cm 3 .

[0020] In one possible implementation, when the battery cell is at 0% SOC, the compaction density of the positive electrode sheet is 2.45 g / cm³. 3 ~2.6g / cm 3 .

[0021] In one possible implementation, when the battery cell is at 0% SOC, the compaction density of the negative electrode sheet is 1.3 g / cm³. 3 ~1.52g / cm 3 .

[0022] In one possible implementation, when the battery cell is at 0% SOC, the compaction density of the negative electrode sheet is 1.3 g / cm³. 3 ~1.5g / cm 3 .

[0023] By keeping the compaction density of the positive and negative electrode sheets within the above range, both high energy density and fast charging performance of the battery cell can be achieved.

[0024] In one possible implementation, the battery cell satisfies at least one of the following conditions: (1) in the first direction, the ratio of the size of the positive electrode film to the size of the housing is 93.7% to 95.6%; (2) in the second direction, the ratio of the size of the positive electrode film to the size of the housing is 92.8% to 95%, and the second direction is perpendicular to the first direction and the thickness direction of the battery cell.

[0025] Setting the ratio of the positive electrode film layer to the casing in the length direction (first direction) and the ratio of the dimensions in the width direction (second direction) within the above range can improve the space utilization rate inside the casing, which is beneficial to improving the energy density of the battery cell.

[0026] In one possible implementation, the battery cell satisfies at least one of the following conditions: (1) the size of the positive electrode film layer in the first direction is 421.5 mm to 621.5 mm; (2) the size of the positive electrode film layer in the second direction is 83.5 mm to 123.5 mm, and the second direction is perpendicular to the first direction and the thickness direction of the battery cell.

[0027] Setting the dimensions of the positive electrode film in the length direction (first direction) within the above range is beneficial to improving the energy density of the battery cell; setting the dimensions of the positive electrode film in the width direction (second direction) within the above range is beneficial to the full wetting of the positive electrode sheet by the electrolyte, reducing internal resistance, accelerating the transport efficiency of lithium ions in the positive electrode material, thereby improving charge and discharge performance.

[0028] In one possible implementation, the battery cell satisfies at least one of the following conditions: (1) the ratio of the size of the main body portion in the first direction to the size of the main body portion in the second direction is greater than 3, and the second direction is perpendicular to the first direction and the thickness direction of the battery cell; (2) the size of the main body portion in the second direction is 90mm to 130mm.

[0029] Setting the dimensions of the main body in the width direction (second direction) within the aforementioned range, and limiting the ratio of the dimensions of the main body in the first direction to the dimensions in the second direction to be greater than 3, is beneficial for increasing the energy density of the battery cell, and also for ensuring sufficient wetting of the main body by the electrolyte, reducing internal resistance, and accelerating the transport efficiency of lithium ions in the electrode material, thereby improving charge and discharge performance.

[0030] In one possible implementation, the ratio of the size of the main body portion in the first direction to the size of the main body portion in the second direction is 4 to 6.

[0031] In one possible implementation, the electrode portion includes a positive electrode and a negative electrode, and the main body portion includes a first end face and a second end face disposed opposite to each other along the first direction. The positive electrode is located on the first end face side and is welded to the positive end cap assembly, and the negative electrode is located on the second end face side and is welded to the negative end cap assembly.

[0032] In this application, the tabs are respectively arranged on both sides along the extension direction (first direction) of the longest side of the electrode assembly. Therefore, the battery cell has a high space utilization rate and thus a high energy density.

[0033] In one possible implementation, an insulating support is provided between the first end face and the positive terminal cap assembly. The insulating support has a receiving cavity corresponding to the positive electrode tab, and the receiving cavity is configured to retract at least a portion of the positive electrode tab. This arrangement can reduce the risk of the positive electrode tab being inserted upside down into the positive electrode body, thereby improving the safety performance of high-energy-density battery cells.

[0034] In one possible implementation, the insulating support includes a first boss, a second boss, a first beam, and a second beam facing the electrode assembly; the first boss and the second boss are disposed on both sides of the insulating support in a second direction, and the first beam and the second beam are disposed on both sides of the insulating support along the thickness direction of the battery cell and connect the first boss and the second boss, wherein the second direction is perpendicular to the first direction and the thickness direction of the battery cell.

[0035] By providing a receiving cavity formed by a first boss, a second boss, a first beam, and a second beam on the side of the insulating support facing the electrode assembly, the receiving cavity is used to house the positive electrode tab, which helps to reduce the risk of the positive electrode tab being inserted backwards into the electrode assembly, thereby improving the safety performance of the battery cell.

[0036] In one possible implementation, in the first direction, the dimensions of the first boss and the second boss are larger than the dimensions of the first beam and the second beam.

[0037] By making the dimensions of the first protrusion and the second protrusion in the first direction larger than the dimensions of the first beam and the second beam in the first direction, it is beneficial to increase the space of the receiving cavity, thereby better accommodating the positive electrode tab.

[0038] In one possible implementation, the dimensions of the first boss and the second boss in the first direction are 4mm to 10mm.

[0039] In one possible implementation, the dimensions of the first beam and the second beam in the first direction are 3mm to 8mm.

[0040] By controlling the dimensions of the first protrusion, the second protrusion, the first beam, and the second beam in the first direction to be within the aforementioned range, both the energy density and safety performance of the battery cell can be taken into account.

[0041] In one possible implementation, the positive terminal cap assembly includes a positive terminal cap and at least two positive terminals disposed on the positive terminal cap.

[0042] The positive terminal has multiple positive terminals, which are welded to the positive electrode tab. This increases the flow area between the positive terminal and the positive electrode tab, thereby reducing the heat generated at the weld between the positive electrode tab and the positive terminal.

[0043] In one possible implementation, the positive terminal includes a first portion and a second portion connected together, the first portion being located on the side of the positive terminal cover facing the electrode assembly and welded to the positive terminal tab, the second portion being on the side opposite to the electrode assembly and protruding through the positive terminal cover, the projection of the first portion overlapping the projection of the second portion along the first direction; and / or, the positive terminal tab being welded to at least two of the first portions.

[0044] The positive terminal includes a first part welded to the positive electrode tab and a second part protruding towards and penetrating the positive terminal cover. The positive terminal cover assembly includes at least two first parts, with the positive electrode tab welded to each of the at least two first parts. This helps to mitigate the thermal expansion and stress generated by the positive terminal and reduces the possibility of cracking in the connection area between the positive electrode tab and the positive terminal, thereby ensuring the normal performance of the battery cell.

[0045] In one possible implementation, the first part and the second part are an integral structure.

[0046] By making the first and second parts of the positive terminal an integral structure, electron transport is more efficient, thereby reducing heat generation at the positive terminal of the battery cell during charging.

[0047] In one possible implementation, the positive terminal includes a first positive terminal and a second positive terminal, and the positive terminal cover assembly includes a first busbar component disposed on the side of the positive terminal cover opposite to the electrode assembly; the first busbar component includes a first through hole and a second through hole, a second portion of the first positive terminal passes through the first through hole along the first direction and is connected to the first busbar component, and a second portion of the second positive terminal passes through the second through hole along the first direction and is connected to the first busbar component.

[0048] The positive terminal cover assembly includes a first busbar component, with at least two positive terminals passing through through holes in the positive terminal cover and the first busbar component to connect to the first busbar component, thereby ensuring the normal function of the battery cell.

[0049] In one possible implementation, the size of the first portion in the first direction is 1mm to 1.5mm. The first portion is used for welding to the positive electrode tab, and setting the thickness of the first portion within the above range can ensure a firm connection between the positive electrode tab and the first portion.

[0050] In one possible implementation, the total cross-sectional area of ​​the first portion is 70 mm². 2 ~210mm 2 .

[0051] The first part is used for welding to the positive electrode tab. The total current-carrying cross-sectional area of ​​the first part is set within the above range. While ensuring a firm connection between the positive electrode tab and the first part, the first part also has a good current-carrying function.

[0052] In one possible implementation, the positive terminal cap assembly includes a first insulating member disposed between the insulating support and the positive terminal cap for insulating the electrode assembly and the positive terminal cap.

[0053] By setting a first insulating member between the positive terminal cover and the insulating support, the positive terminal and the cover surrounding the positive terminal can be insulated, reducing the risk of short circuit between the positive and negative terminals. Furthermore, the first insulating member occupies part of the space in the first direction, which can reduce the movement space of the electrode assembly in the first direction and reduce the risk of electrode damage caused by the electrode assembly hitting the positive terminal cover when the battery cell vibrates during use.

[0054] In one possible implementation, the first insulating member includes a first wall abutting against the positive terminal cap and a first recess facing the electrode assembly; the first wall has a first straight portion and a third through hole for the second portion to pass through, and the first recess is used to accommodate at least a portion of the first portion.

[0055] The above configuration can further save the internal space of the battery cell occupied by the first insulating component in the first direction, and further improve the energy density of the battery cell; and the first part is just accommodated in the first recess of the first insulating component, which can limit the positive terminal and reduce the positive terminal from swaying left and right and pulling the welding connection area with the positive electrode tab.

[0056] In one possible implementation, at least a portion of the first boss and / or the second boss abuts against the first insulating member.

[0057] By making the insulating support abut against the first insulating member, the internal space of the battery cell occupied by the first insulating member in the first direction can be further saved, which helps to improve the energy density of the battery cell; and the two can maintain the stability of the structure through direct contact.

[0058] In one possible implementation, the size of the first straight portion in the first direction is 1 mm to 3 mm. By limiting the size of the first straight portion in the first direction to the above range, it is beneficial to balance the safety performance and energy density of the battery cell.

[0059] In one possible implementation, the positive end cap includes a pressure relief mechanism; a fourth through hole corresponding to the pressure relief mechanism is provided on the first straight portion, and a fifth through hole corresponding to the fourth through hole is provided on the first protrusion.

[0060] By setting a pressure relief mechanism on the positive terminal cover, and correspondingly setting a fifth through hole and a fourth through hole, the gas can be discharged in time when a large amount of gas is generated inside the battery cell due to a fault, so as to ensure the safety performance of the battery cell.

[0061] In one possible implementation, the main body includes a positive electrode body portion, and the positive electrode tab extends from the positive electrode body portion along the first direction; in the second direction, the ratio of the size of the positive electrode tab to the size of the positive electrode body portion is greater than 50%.

[0062] In one possible implementation, in the second direction, the ratio of the size of the positive electrode tab to the size of the positive electrode body portion is 60% to 100%.

[0063] In the width direction (second direction) of the battery cell, by setting the size ratio of the positive electrode tab to the positive electrode body portion within the above range, it is possible to increase the current flow area at the positive electrode tab, reduce the impedance and heat generation at the positive electrode tab, and also take into account the energy density of the battery cell.

[0064] In one possible implementation, the first portion has a first surface close to the electrode assembly; in the first direction, the distance between the edge of the positive electrode film and the first surface is 7 mm to 10 mm.

[0065] By limiting the size of the positive electrode tab space within the above range, the risk of reverse insertion of the positive electrode tab can be reduced, while also taking into account the energy density of the battery cell.

[0066] In one possible implementation, the total area of ​​the first welding region formed by welding the positive electrode tab to the first portion is 130 mm². 2 ~200mm 2 .

[0067] By keeping the welding area between the positive electrode tab and the first part within the above range, normal current transmission can be guaranteed, while also taking into account the safety performance of the battery cell.

[0068] In one possible implementation, the positive electrode has a chamfered structure at the apex corner on the second end face side.

[0069] Compared to the negative electrode, the positive electrode is harder. Therefore, during the fabrication of stacked electrode assemblies, the sharp corners of the positive electrode are more likely to pierce the separator, leading to a short circuit between the positive and negative electrodes. Therefore, by adding a chamfered structure to the side of the positive electrode where the positive electrode tab is not located, the risk of the sharp corners piercing the separator due to the higher hardness of the positive electrode can be reduced, thus improving the safety performance of the individual battery cells.

[0070] In one possible implementation, the dimension of the chamfered structure on the extension line of the second direction is greater than the dimension on the extension line of the first direction.

[0071] The risk of the positive electrode sheet piercing the separator is greater in the second direction (width direction). Therefore, by making the dimension of the chamfered structure on the extension line of the second direction larger than the dimension on the extension line of the first direction (length direction), it is more beneficial to reduce the risk of the sharp corner of the positive electrode sheet piercing the separator, thereby improving the safety performance of the battery cell.

[0072] In one possible implementation, the chamfer structure has a size of 1mm to 2mm along the extension of the first direction; and a size of 1mm to 10mm along the extension of the second direction.

[0073] By controlling the size of the chamfered structure within the aforementioned range, it is beneficial to balance the energy density and safety performance of the battery cells.

[0074] In one possible implementation, the chamfered structure is a fan-shaped structure. The fan-shaped chamfered structure can minimize the risk of puncturing the isolation membrane.

[0075] In one possible implementation, the positive electrode includes a first transition region along the first direction, the first transition region being located at one end of the positive electrode film layer near the positive electrode tab and adjacent to the positive electrode film layer; the first transition region is provided with an insulating material.

[0076] By setting a first transition zone coated with insulating material on the side of the positive electrode sheet near the positive electrode tab, the risk of short circuit between the positive and negative electrodes caused by burrs piercing the separator during the cutting of the positive electrode tab can be reduced during the manufacturing process of the battery cell. This can further improve the safety performance of the battery cell.

[0077] In one possible implementation, the size of the first transition region in the first direction is 1.5 mm to 4 mm.

[0078] By controlling the size of the first transition region within the aforementioned range in the first direction, it is beneficial to balance the safety performance and energy density of the battery cell.

[0079] In one possible implementation, the positive electrode tab includes a second transition region along the first direction, the second transition region being located at one end of the positive electrode tab near the main body and adjacent to the first transition region; the second transition region is provided with an insulating material.

[0080] A second transition zone coated with insulating material is set at the root of the positive electrode tab, which helps to reduce the risk of burrs generated at the root of the tab during the cutting of the positive electrode tab piercing the separator and causing a short circuit between the positive and negative electrodes, thereby further improving the safety performance of the battery cell.

[0081] In one possible implementation, the size of the second transition region in the first direction is 4mm to 7mm.

[0082] By controlling the size of the second transition region within the aforementioned range in the first direction, it is beneficial to balance the safety performance and energy density of the battery cell.

[0083] In one possible implementation, in the first direction, the size ratio of the second transition region to the positive electrode tab is 1 / 6 to 1 / 3.

[0084] By maintaining the size ratio of the second transition region to the positive electrode tab within the above range, the safety performance of the battery cell can be improved, and the positive electrode tab can be guaranteed to have normal overcurrent capacity.

[0085] In one possible implementation, the negative end cap assembly includes a negative end cap and at least two negative terminals disposed on the negative end cap.

[0086] The negative terminal has at least two terminals, and the at least two negative terminals are welded to the negative electrode tab, which can increase the flow area between the negative terminal and the negative electrode tab, thereby reducing the heat generation at the weld between the negative terminal and the negative electrode tab.

[0087] In one possible implementation, the negative terminal includes a connected third portion and a fourth portion, the third portion being located on the side of the negative terminal cover facing the electrode assembly and welded to the negative electrode tab, the fourth portion being on the side opposite to the electrode assembly and protruding through the negative terminal cover, the projection of the third portion overlapping the projection of the fourth portion along the first direction; and / or, the negative electrode tab being welded to at least two of the third portions.

[0088] The negative terminal includes a third part welded to the negative electrode tab and a fourth part protruding towards and penetrating the negative terminal cover. The negative terminal cover assembly includes at least two third parts, with the negative electrode tab welded to each of the at least two third parts. This helps to mitigate thermal expansion and stress generated by the negative terminal cover and reduces the possibility of cracking in the connection area between the negative electrode tab and the negative terminal, thereby ensuring the normal performance of the battery cell.

[0089] In one possible implementation, the third and fourth parts are integrated into a single structure. This is more conducive to electron transport, thereby reducing heat generation at the negative terminal of the battery cell during charging.

[0090] In one possible implementation, the negative terminal includes a first negative terminal and a second negative terminal, and the negative terminal cover assembly includes a second busbar component disposed on the side of the negative terminal cover opposite to the electrode assembly; the second busbar component includes a sixth through hole and a seventh through hole, a fourth portion of the first negative terminal passes through the sixth through hole along the first direction and is connected to the second busbar component, and the fourth portion of the second negative terminal passes through the seventh through hole along the first direction and is connected to the second busbar component.

[0091] The negative terminal cover assembly includes a second busbar component, with at least two negative terminals passing through through holes in the negative terminal cover and the second busbar component to connect with the second busbar component, thereby ensuring the normal function of the battery cell.

[0092] In one possible implementation, the third portion has a size of 1.2 mm to 2.5 mm in the first direction.

[0093] The third part is used for welding to the negative electrode tab. Setting the thickness of the third part within the above range can make the negative electrode tab and the third part firmly connected.

[0094] In one possible implementation, the total cross-sectional area of ​​the third part is 70 mm². 2 ~210mm 2 .

[0095] The third part is used for welding to the negative electrode tab. The total current-carrying cross-sectional area of ​​the third part is set within the above range. This ensures a firm connection between the negative electrode tab and the third part, while also giving the third part a better current-carrying capacity.

[0096] In one possible implementation, the negative terminal cap assembly includes a second insulating member disposed between the electrode assembly and the negative terminal cap for insulating the electrode assembly and the negative terminal cap.

[0097] By setting a second insulating member between the negative terminal cover and the electrode assembly, the negative terminal and the cover surrounding the negative terminal can be insulated, reducing the risk of short circuit between the positive and negative terminals. Furthermore, the second insulating member occupies part of the space in the first direction, which can reduce the movement space of the electrode assembly in the first direction and reduce the risk of electrode damage caused by the electrode assembly hitting the negative terminal cover when the battery cell vibrates during use.

[0098] In one possible implementation, the second insulating member includes a second wall abutting against the negative terminal cap and a second recess facing the electrode assembly; the second wall has a second straight portion and an eighth through hole through which the fourth portion passes, and the second recess is used to accommodate at least a portion of the third portion and at least a portion of the negative electrode tab.

[0099] With the above configuration, the internal space of the battery cell occupied by the second insulating member in the first direction can be further saved, and the energy density of the battery cell can be further improved; and the third part is just accommodated in the second recess of the second insulating member and the negative electrode tab. The second recess can limit the negative terminal, reducing the negative terminal from swaying left and right and pulling the welding connection area with the negative electrode tab.

[0100] In one possible implementation, the side of the second insulating member closest to the electrode assembly abuts against at least a portion of the electrode assembly.

[0101] The negative electrode tab is housed in the second recess and connected to the third part of the negative terminal. By having the second insulating member partially abut against the electrode assembly, it is beneficial to further improve the energy density of the battery cell. Furthermore, the second insulating member is fixed inside the battery cell, and when at least part of the electrode assembly abuts against the second insulating member, the possibility of the electrode assembly shaking in the first direction can be reduced.

[0102] In one possible implementation, the size of the second straight portion in the first direction is 6mm to 9mm.

[0103] By limiting the size of the second straight portion in the first direction to the aforementioned range, it is beneficial to balance the safety performance and energy density of the battery cell.

[0104] In one possible implementation, the negative end cap further includes a liquid injection mechanism, and the second insulating member is provided with a ninth through hole, which corresponds to the liquid injection mechanism.

[0105] By providing a ninth through hole on the second insulating component that corresponds to the electrolyte injection mechanism, it can be ensured that the electrolyte is successfully injected into the battery cell.

[0106] In one possible implementation, the main body includes a negative electrode body portion, and the negative electrode tab extends from the negative electrode body portion along the first direction; in the second direction, the ratio of the size of the negative electrode tab to the size of the negative electrode body portion is greater than 50%.

[0107] In one possible implementation, in the second direction, the ratio of the size of the negative electrode tab to the size of the negative electrode body portion is 60% to 100%.

[0108] In the width direction (second direction) of the battery cell, the ratio of the size of the negative electrode tab to the size of the negative electrode body is set within the above range. This can increase the current flow area at the negative electrode tab, reduce the impedance and heat generation at the negative electrode tab, and also take into account the energy density of the battery cell.

[0109] In one possible implementation, the third portion has a second surface close to the electrode assembly; the negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector, wherein in the first direction, the dimension between the edge of the negative electrode film layer and the second surface is 7 mm to 10 mm.

[0110] By limiting the size of the negative electrode tab space within the above range, the negative electrode tab can be properly placed while also taking into account the energy density of the battery cell.

[0111] In one possible implementation, the total area of ​​the second welding region formed by welding the negative electrode tab to the third part is 130 mm². 2 ~200mm 2 .

[0112] By keeping the welding area between the negative electrode tab and the third part within the above range, normal current transmission can be guaranteed, while also taking into account the safety performance of the battery cell.

[0113] In one possible implementation, in the first direction, the edge of the negative electrode film extends beyond the edge of the positive electrode film; and in the second direction, the edge of the negative electrode film extends beyond the edge of the positive electrode film.

[0114] By making the edge of the negative electrode film extend beyond the edge of the positive electrode film in both the first and second directions, the formation of lithium dendrites can be reduced, which is beneficial to further improving the safety performance of the battery cell.

[0115] In one possible implementation, in the first direction, the distance by which the edge of the negative electrode film extends beyond the edge of the positive electrode film is OH1, and in the second direction, the distance by which the edge of the negative electrode film extends beyond the positive electrode film is OH2; OH1 is 3mm~8mm, and OH2 is 1mm~4mm.

[0116] By keeping OH1 and OH2 within the above range, the formation of lithium dendrites can be reduced, and the negative electrode film layer can be kept from being too long, thereby improving the energy density of the battery cell.

[0117] In one possible implementation, the projection of the first transition region overlaps the projection of the edge of the negative electrode film layer in the thickness direction of the battery cell.

[0118] In the thickness direction of the battery cell, by making the projection of the first transition region cover the projection of the edge of the negative electrode film layer, the risk of short circuit in the battery cell can be further reduced, thereby further improving the safety performance of the battery cell.

[0119] In one possible implementation, the positive electrode film layer includes a positive electrode active material, which includes lithium transition metal phosphate; the negative electrode film layer includes a negative electrode active material, which includes graphite.

[0120] In one possible implementation, the lithium transition metal phosphate includes at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

[0121] In one possible implementation, the volume average particle size Dv50 of the graphite is 8 μm to 13 μm.

[0122] By maintaining the volume average particle size Dv50 of the negative electrode active material at 8μm~13μm, both the fast charging performance and cycle performance of the battery cell can be balanced.

[0123] In one possible implementation, the negative electrode film layer includes a first film layer and a second film layer, with the first film layer located between the negative electrode current collector and the second film layer; the graphite in the first film layer includes artificial graphite or a mixture of artificial graphite and natural graphite, and the average particle size of the longest diameter of the graphite is 7μm to 18μm; the graphite in the second film layer includes artificial graphite or a mixture of artificial graphite and natural graphite, and the average particle size of the longest diameter of the graphite is 6μm to 10μm.

[0124] By configuring the negative electrode film into a double-layer structure, and using large-particle graphite in the first layer closest to the current collector, the high energy density of the battery cell can be guaranteed to a certain extent. Furthermore, using small-particle graphite in the second layer closest to the electrolyte improves its contact with the electrolyte, resulting in better wettability of the graphite by the electrolyte. The smaller particle size in the second layer also leads to larger porosity, which is beneficial for improving the fast-charging performance of the battery cell. In other words, the use of different particle sizes in the two layers of the negative electrode film can balance high energy density and fast-charging performance of the battery cell.

[0125] In one possible implementation, the battery cell satisfies at least one of the following conditions: (1) the average particle size of the graphite in the negative electrode film is 7 μm to 15 μm, and the graphite in the negative electrode film includes secondary particles; (2) the graphitization degree of the graphite in the negative electrode film is 90% to 94%.

[0126] Setting the overall graphite particle size of the negative electrode film within the above-mentioned range and limiting the degree of graphitization within the above-mentioned range is beneficial to improving the energy density of the battery cell.

[0127] In one possible implementation, a first functional layer is disposed between the negative electrode current collector and the negative electrode film layer, the first functional layer comprising an adhesive and a conductive agent; the thickness of the first functional layer is 0.2 μm to 3 μm; the adhesive comprises at least one of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan; the conductive agent comprises at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0128] By setting a first functional layer between the negative electrode current collector and the negative electrode film layer, the adhesion between the negative electrode film layer and the negative electrode current collector can be increased to prevent the negative electrode film layer from demolding, thereby improving the reliability of the battery cell. It can also improve the conductivity of the negative electrode sheet, reduce the heat generation of the negative electrode sheet and the heat generation of the battery cell, thereby meeting the fast charging performance of the battery cell.

[0129] In one possible implementation, when the battery cell is at 0% SOC, the porosity of the negative electrode is 25% to 40%. This can improve the kinetics of the negative electrode, thereby enhancing the fast-charging performance of the battery cell.

[0130] In one possible implementation, the battery cell further includes a separator, wherein the positive electrode, the separator, and the negative electrode are stacked in the thickness direction of the battery cell; the separator includes a base film and a second functional layer disposed on at least one side of the base film, the second functional layer including inorganic particles.

[0131] In one possible implementation, the inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide; and / or the average particle size of the inorganic particles is 5 nm to 100 nm.

[0132] By setting a second functional layer including inorganic particles on the base film of the separator, the heat resistance of the first functional layer can be improved, thereby enhancing the reliability of the battery cell. Furthermore, ensuring that the average particle size of the inorganic particles is within the aforementioned range is beneficial for improving the heat resistance and compressive modulus of the separator, which in turn further enhances the reliability of the battery cell.

[0133] In one possible implementation, the separator further includes a third functional layer located on the side of the second functional layer away from the base membrane, the third functional layer comprising a fluorinated adhesive.

[0134] By setting a third functional layer including a fluorinated binder, the connection between the separator and the electrode is improved, avoiding misalignment between the electrode and the separator due to the large surface area of ​​the electrode assembly. This prevents short circuits between the positive and negative electrodes and improves the reliability of the battery cell.

[0135] In one possible implementation, the thickness of the base film is less than 9 μm.

[0136] In one possible implementation, the thickness of the base film is 4 μm to 7 μm.

[0137] In one possible implementation, the thickness of the second functional layer is 0.5 μm to 1.5 μm.

[0138] In one possible implementation, the thickness of the third functional layer is 1 μm to 2.5 μm.

[0139] In one possible implementation, the thickness of the isolation membrane is 9 μm to 12 μm.

[0140] By ensuring that the thickness of each layer of the separator is within the aforementioned range, it is beneficial to improve the reliability of the battery cell while guaranteeing its energy density.

[0141] In one possible implementation, the thickness of the housing is less than 0.5 mm.

[0142] In one possible implementation, the thickness of the shell is 0.3 mm to 0.4 mm.

[0143] Setting the thickness of the casing within the aforementioned range can protect the electrode components without affecting the energy density of the individual battery cells due to excessive thickness.

[0144] In one possible implementation, the casing is made of a metallic material, including aluminum or steel. This provides the casing with good structural strength and a lighter weight, reducing the overall weight of the battery cell.

[0145] In one possible implementation, the housing includes a first sidewall and a second sidewall extending along the first direction, the first sidewall being the wall with the largest surface area of ​​the housing, and the housing including a weld located on the second sidewall and extending along the first direction.

[0146] The weld seam of the casing is located on the side wall with a smaller surface area. This means that when thermal runaway occurs in the battery cell, the high-temperature expansion force at the weld seam is smaller, and the overall stress on the casing of the battery cell is more uniform. The casing is less likely to crack at the weld seam, thus reducing the risk of thermal runaway spreading from the battery cell.

[0147] In one possible implementation, the battery cell further includes an electrolyte contained within the accommodating space, the electrolyte comprising an organic solvent, the organic solvent comprising dimethyl carbonate and a linear carboxylic acid ester; based on the total mass of the electrolyte, the sum of the mass contents of the dimethyl carbonate and the linear carboxylic acid ester is 10% to 60%.

[0148] In one possible implementation, the sum of the mass contents of the dimethyl carbonate and the linear carboxylic acid ester is 40% to 60% based on the total mass of the electrolyte.

[0149] In this embodiment, the electrode assembly has a large surface area, which is beneficial for heat dissipation of the battery cell. Based on this, a higher content of linear carboxylic acid ester solvent can be used in the electrolyte to improve the conductivity of the electrolyte, thereby improving the dynamic performance of the battery and the fast charging performance of the battery cell.

[0150] In one possible implementation, the linear carboxylic acid ester comprises the compound shown in formula (I).

[0151] Formula (I)

[0152] R1 and R2 each independently include alkyl or haloalkyl groups having 1 to 5 carbon atoms.

[0153] In one possible implementation, the linear carboxylic acid ester includes at least one of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

[0154] In one possible implementation, the electrolyte further includes a lithium salt, wherein the lithium salt has a mass content of 12% to 21% based on the total mass of the electrolyte.

[0155] Setting the mass content of lithium salt in the electrolyte within the above range is beneficial to further improve the fast charging performance of individual battery cells.

[0156] In one possible implementation, the lithium salt comprises lithium fluorosulfonylimide and lithium hexafluorophosphate; in the electrolyte, the mass ratio of the lithium hexafluorophosphate to the lithium fluorosulfonylimide is 0.8 to 3.5.

[0157] By combining lithium fluorosulfonylimide and lithium hexafluorophosphate, the conductivity of the electrolyte is improved while the generation of hydrofluoric acid is reduced, and the side reactions of the electrolyte are reduced, thus balancing the fast-charging performance and cycle life of the battery cells.

[0158] In one possible implementation, the lithium fluorinated sulfonamide includes at least one of lithium bisfluorosulfonamide and lithium bistrifluoromethanesulfonate imide.

[0159] Both of the above-mentioned lithium fluorosulfonylimide compounds can effectively improve the conductivity of the electrolyte, and have good thermal and electrochemical stability, which can reduce the occurrence of electrolyte side reactions.

[0160] In one possible implementation, the electrolyte further includes an additive, which includes at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate; the mass content of the additive is 0.1% to 5% based on the total mass of the electrolyte.

[0161] By setting the above additives within an appropriate range, the composition of the solid electrolyte interphase (SEI) film on the negative electrode side can be optimized, alleviating the volume expansion and interfacial side reactions of negative electrode active materials such as silicon-based materials, reducing high-temperature gas generation, and ensuring that the impedance of the SEI film is not too high and the internal resistance of the battery cell is relatively small, thus achieving a balance between improving the fast charging capability and reliability of the battery cell.

[0162] In one possible implementation, the conductivity of the electrolyte is 13 ms / cm to 20 ms / cm.

[0163] In one possible implementation, the conductivity of the electrolyte is 13 ms / cm to 17 ms / cm.

[0164] Setting the electrolyte conductivity within the aforementioned range helps to further improve the performance of individual battery cells.

[0165] In one possible implementation, the surface of the housing facing away from the electrode assembly has a first insulating film, the thickness of which is 0.05 mm to 0.2 mm; the material of the first insulating film includes at least one selected from polyethylene terephthalate, polypropylene, and polyimide. By providing an insulating film on the surface of the housing, the insulation and abrasion resistance of the housing can be improved.

[0166] In one possible implementation, the first insulating film has openings.

[0167] In one possible implementation, a second insulating film is provided between the main body and the housing, the second insulating film serving to insulate the main body from the housing; the second insulating film comprises at least one of polypropylene and polyethylene terephthalate. By covering the outer surface of the electrode assembly with an insulating film, the electrical connection between the housing and the electrode assembly can be isolated, reducing the short-circuit risk of the battery cell.

[0168] In one possible implementation, the battery cell further includes a side support plate disposed between the housing and the electrode assembly, the side support plate extending along the first direction and disposed opposite to the second side surface.

[0169] A side support plate is installed between the electrode assembly and the housing. This serves two purposes: firstly, it insulates the electrode assembly from the housing, and secondly, it improves the structural stability of the battery cell.

[0170] In one possible implementation, when the battery cell is charged at a 1 / 3C rate, the volumetric energy density of the battery cell is 440Wh / L to 460Wh / L.

[0171] In one possible implementation, when the battery cell is charged at a 1 / 3C rate, the mass energy density of the battery cell is 190Wh / kg to 200Wh / kg.

[0172] In a second aspect, a battery device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof.

[0173] Thirdly, an electrical device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof, or a battery device as described in the second aspect, wherein the battery cell or the battery device is used to store or provide electrical energy. Attached Figure Description

[0174] 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.

[0175] Figure 1 This is a schematic diagram of the structure of a battery cell according to one embodiment of this application;

[0176] Figure 2 This is a schematic diagram of the structure of a battery cell according to another embodiment of this application;

[0177] Figure 3 This is a schematic diagram of the structure of a portion of the electrode assembly according to one embodiment of this application;

[0178] Figure 4 This is a schematic diagram of the structure of the positive electrode sheet according to one embodiment of this application;

[0179] Figure 5 This is a schematic diagram of the structure of the negative electrode sheet according to one embodiment of this application;

[0180] Figure 6 This is a schematic diagram of the structure of an insulating support member according to one embodiment of this application;

[0181] Figure 7 This is a schematic diagram of the positive end cap assembly according to one embodiment of this application;

[0182] Figure 8 This is a schematic diagram of the positive end cap assembly according to another embodiment of this application;

[0183] Figure 9 This is an exploded view of the positive end cap assembly according to one embodiment of this application;

[0184] Figure 10 This is a schematic diagram of the structure of the first insulating member according to an embodiment of this application;

[0185] Figure 11 This is a cross-sectional view of a battery cell according to an embodiment of this application;

[0186] Figure 12 This is a schematic diagram of the structure of the positive electrode sheet according to another embodiment of this application;

[0187] Figure 13 This is a schematic diagram of the structure of a battery cell according to another embodiment of this application;

[0188] Figure 14 This is an exploded view of the negative end cap assembly according to one embodiment of this application;

[0189] Figure 15 This is a schematic diagram of the structure of the second insulating member according to an embodiment of this application;

[0190] Figure 16 This is a cross-sectional view of a battery cell according to another embodiment of this application;

[0191] Figure 17 This is a schematic diagram of the structure of the negative electrode sheet according to another embodiment of this application;

[0192] Figure 18 This is a schematic diagram of the structure of the negative electrode sheet in another embodiment of this application;

[0193] Figure 19 This is a schematic diagram of the negative electrode sheet according to another embodiment of this application;

[0194] Figure 20 This is a partial structural schematic diagram of a battery cell according to another embodiment of this application;

[0195] Figure 21 This is a schematic diagram of a battery device according to one embodiment of this application;

[0196] Figure 22 This is a schematic diagram of an electrical device according to one embodiment of this application.

[0197] The accompanying drawings are not drawn to scale.

[0198] Explanation of reference numerals in the attached figures:

[0199] Battery cell - 100, casing - 10, sealing ring - 110;

[0200] Housing-20, first sidewall 20a, second sidewall 20b, accommodating space-201, electrode assembly-21, main body-22, tab-23, first side surface 22a, second side surface 22b, positive electrode plate-210, positive electrode plate main body-211, positive electrode film-2111, first transition region-2112, positive current collector-2113, positive electrode tab-212, second transition region-2121, chamfered structure-213, negative electrode plate-220, negative electrode plate main body-221, negative electrode film-2211, first film-22111, second film-22112, negative current collector-2213, first functional layer-2214, negative electrode tab-222, separator-230;

[0201] Positive terminal cap assembly-30, positive terminal cap-310, pressure relief mechanism-311, positive terminal-320, first part-321, first surface-3211, second part-322, first positive terminal-323, second positive terminal-324, first busbar component-330, first through hole-331, second through hole-332, first insulating member-340, first wall-341, first straight part-3411, third through hole-3412, first recess-342, fourth through hole-343;

[0202] Negative end cap assembly-40, negative end cap-410, liquid injection mechanism-411, negative end-420, third part-421, second surface-4211, fourth part-422, first negative end-423, second negative end-424, second manifold component-430, sixth through hole-431, seventh through hole-432, second insulating member-440, second wall-441, second straight part-4411, eighth through hole-4412, second recess-442, ninth through hole-443;

[0203] Insulating support member-50, first boss-510, second boss-520, first beam-530, second beam-540, receiving cavity-550, fifth through hole-560, side support plate-51;

[0204] Battery unit-60, housing-61, first housing section 611, second housing section 612, vehicle-70, motor-80, controller-90;

[0205] First direction - X, second direction - Y, thickness direction of the battery cell - Z. Detailed Implementation

[0206] The following detailed description of embodiments of the battery cell, battery device, and electrical appliance of this application, with appropriate reference to the accompanying drawings, may omit unnecessary details. 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.

[0207] 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 also 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 "a~b" 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.

[0208] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicating orientation or positional relationships are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0209] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0210] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0211] 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.

[0212] To improve the energy density of individual battery cells, one feasible approach is to use electrode assemblies with a stacked structure. Stacked electrode assemblies can improve the space utilization within the battery cell's casing, thereby increasing the energy density. Another feasible approach is to use thick electrode coatings to improve energy density. However, thick electrode coatings increase the impedance of the battery cell, leading to increased heat generation, which accelerates battery aging and increases the risk of thermal runaway.

[0213] To address the aforementioned issues, this application improves the reliability of high-energy-density battery cells by modifying the electrode structure dimensions of the battery cell. Specifically:

[0214] The areal density of the positive electrode film layer on one side is greater than 375 mg / 1540.25 mm. 2 Furthermore, the electrode assembly has a stacked structure, thus the battery cell has a high energy density.

[0215] However, the impedance of a battery cell with a thickly coated electrode increases during charging and discharging, leading to increased heat generation in the battery cell, which accelerates battery aging and increases the risk of battery thermal runaway.

[0216] To improve the heat dissipation performance of individual battery cells, the length of the main body of the electrode assembly is set to be greater than 400mm, the thickness of the main body is set to be less than 20mm, and the ratio of the area of ​​the largest surface of the electrode assembly to the area of ​​its other sides is set to be greater than 6. This results in a larger surface area for the electrode assembly, increasing the heat dissipation area of ​​the individual battery cell, while the thinner electrode assembly facilitates heat dissipation in thickly coated battery cells. Through this structural dimension design, the heat dissipation capacity of the individual battery cells is improved.

[0217] The above comprehensive measures can improve the heat dissipation capability of thick-coated battery cells, and while increasing the energy density of battery cells, they also take into account the reliability of battery cells.

[0218] The embodiments of this application will be described next.

[0219] [Battery cell]

[0220] Firstly, a battery cell is provided. Figure 1 This is a schematic diagram of the structure of a battery cell according to one embodiment of this application. Figure 2 This is a schematic diagram of the structure of a battery cell according to another embodiment of this application. Figure 3 This is a structural diagram of a portion of the electrode assembly according to one embodiment of this application.

[0221] like Figure 1-3 As shown, the battery cell 100 includes a housing 10 and an electrode assembly 21.

[0222] The housing 10 includes a housing 20, a positive end cap assembly 30, and a negative end cap assembly 40, which are used to close the opening of the housing 20.

[0223] An accommodating space 201 is formed within the housing 20 to accommodate the electrode assembly 21. The electrode assembly 21 includes a positive electrode 210 and a negative electrode 220 disposed along the thickness direction Z of the battery cell. The electrode assembly 21 has a stacked structure.

[0224] The electrode assembly 21 includes a main body 22 and a tab 23 located on the end face of the main body 22. The main body 22 has a dimension greater than 400 mm in the first direction X and a dimension less than 20 mm in the thickness direction Z of the battery cell 100. The first direction X is the extension direction of the longest side of the electrode assembly 21 (i.e., the length direction of the electrode assembly 21). The main body 22 includes a first side 22a and a second side 22b extending along the first direction X. The first side 22a is the surface with the largest area of ​​the electrode assembly 21, and the ratio of the area of ​​the first side 22a to the area of ​​the second side 22b is greater than 6.

[0225] It should be understood that the second side 22b refers to any side of the electrode assembly 21 other than the side with the largest area, for example, when the shape of the battery cell 100 is square (e.g., Figure 1 As shown), the second side 22b can be two sides arranged opposite each other along the second direction Y, which is perpendicular to the first direction X and the thickness direction of the battery cell 100. For example, when the shape of the battery cell 100 is prism (e.g.... Figure 2 As shown), the second side 22b can be four sides that are adjacent to the two first sides 22a respectively.

[0226] The second direction Y is perpendicular to the first direction X and the thickness direction of the battery cell 100, that is, the second direction Y can be called the width direction X of the battery cell.

[0227] Figure 4 This is a schematic diagram of the structure of the positive electrode sheet according to one embodiment of this application.

[0228] like Figure 4As shown, the positive electrode 210 includes a positive current collector 2113 and a positive electrode film layer 2111 disposed on at least one side of the positive current collector 2113. The one-sided areal density of the positive electrode film layer 2111 is greater than 375 mg / 1540.25 mm². 2 .

[0229] The positive current collector 2113 has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer 2111 is disposed on either or both of the two opposite surfaces of the positive current collector 2113. As an example, Figure 4 The positive electrode film layer 2111 is disposed on both surfaces of the positive electrode current collector 2113.

[0230] In this application, the electrode assembly 21 has a stacked structure, which makes the interior of the casing 10 of the battery cell 100 have a high space utilization rate, and the positive electrode film layer 2111 of the positive electrode sheet 210 adopts a thick coating method. Through the above measures, the energy density of the battery cell 100 is improved.

[0231] However, thick coating of the electrode will increase the impedance of the battery cell 100 during the charging and discharging process, resulting in increased heat generation of the battery cell 100, which will accelerate battery aging and increase the risk of battery thermal runaway, affecting the reliability of the battery cell 100.

[0232] Therefore, this application also designs the structural dimensions of the electrode assembly 21. By controlling the length of the main body 22 of the electrode assembly 21 to be greater than 400 mm, the thickness of the main body 22 to be less than 20 mm, and setting the ratio of the area of ​​the largest surface of the electrode assembly 21 to the area of ​​other side surfaces to be greater than 6, the large surface area of ​​the electrode assembly 21 is made larger, thereby increasing the heat dissipation area of ​​the battery cell 100. The electrode assembly 21 is thinner, which is beneficial to the heat dissipation of the thick-coated battery cell 100. Through the above structural dimension design, the heat dissipation capacity of the battery cell 100 is improved.

[0233] The above comprehensive measures can improve the heat dissipation capability of the thick-coated battery cell 100, and improve the energy density of the battery cell 100 while taking into account the reliability of the battery cell 100.

[0234] For example, the dimensions of the main body 22 in the first direction X can be 410mm, 420mm, 430mm, 450mm, 470mm, 500mm, 550mm, 600mm, 630mm, 650mm, or a value within the range obtained by any combination of the above two values.

[0235] Optionally, the main body 22 has a dimension of 450mm to 650mm in the first direction X.

[0236] For example, the dimensions of the main body 22 in the thickness direction Z of the battery cell 100 can be 19mm, 18mm, 17mm, 16mm, 15mm, 14mm, 13mm, 12mm, or values ​​within the range obtained by any combination of the above two values.

[0237] Optionally, the main body 22 has a dimension of 13mm to 18mm in the thickness direction Z of the battery cell 100.

[0238] For example, the ratio of the area of ​​the first side 22a to the area of ​​the second side 22b can be 7, 8, 9, 10, 11, or a value within the range obtained by any combination of the above two values.

[0239] Optionally, the ratio of the area of ​​the first side 22a to the area of ​​the second side 22b is 7 to 10. This further increases the surface area of ​​the electrode assembly 21 and improves the heat dissipation performance of the high-energy-density battery cell 100.

[0240] For example, the areal density of the positive electrode film layer 2111 on one side can be 380 mg / 1540.25 mm. 2 390mg / 1540.25mm 2 400mg / 1540.25mm 2 405mg / 1540.25mm 2 410mg / 1540.25mm 2 415mg / 1540.25mm 2 420mg / 1540.25mm 2 430mg / 1540.25mm 2 , or its value is within the range obtained by combining any two of the above values.

[0241] Optionally, the areal density of the positive electrode film 2111 is 380 mg / 1540.25 mm². 2 ~420mg / 1540.25mm 2 This will further help improve the energy density of the battery cell.

[0242] In the embodiments of this application, the areal density of the positive electrode film can be detected using equipment and methods known in the art. For example, a single battery cell is discharged at a constant current of 0.05C to 2V to obtain a battery cell with 0% SOC; a positive electrode sheet of a certain area is taken, its area is measured, and the mass of the positive electrode film layer on the current collector after removing the positive electrode current collector is weighed. The areal density of the positive electrode sheet is calculated based on the area and mass. The negative electrode sheet is processed similarly, and will not be described in detail below.

[0243] In the embodiments of this application, unless otherwise specified, a battery cell in the 0% SOC state refers to a battery cell that is discharged at a constant current of 0.05C to 2V.

[0244] Figure 5 This is a schematic diagram of the negative electrode sheet according to one embodiment of this application.

[0245] like Figure 5 As shown, in some embodiments, the negative electrode 220 includes a negative electrode current collector 2213 and a negative electrode film layer 2211 disposed on at least one side of the negative electrode current collector 2213, wherein the one-sided areal density of the negative electrode film layer 2211 is 165 mg / 1540.25 mm². 2 ~185mg / 1540.25mm 2 .

[0246] The negative electrode current collector 2213 has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer 2211 is disposed on either or both of the two opposite surfaces of the negative electrode current collector 2213. As an example, Figure 5 The negative electrode film layer 2211 is disposed on both surfaces of the negative electrode current collector 2213.

[0247] For example, the areal density of the negative electrode film layer 2211 on one side can be 165 mg / 1540.25 mm. 2 170mg / 1540.25mm 2 172mg / 1540.25mm 2 178mg / 1540.25mm 2 180mg / 1540.25mm 2 183mg / 1540.25mm 2 185mg / 1540.25mm 2 , or its value is within the range obtained by combining any two of the above values.

[0248] Setting the surface density of the negative electrode film layer 2211 within the above range is beneficial to improving the energy density of the battery cell 100.

[0249] In some embodiments, the battery cell 100 satisfies at least one of the following conditions: (1) the ratio of the thickness of the negative electrode film 2211 to the thickness of the negative electrode current collector 2213 is greater than 12; (2) the ratio of the thickness of the positive electrode film 2111 to the thickness of the positive electrode current collector 2113 is greater than 6.5.

[0250] For example, the ratio of the thickness of the negative electrode film layer 2211 to the thickness of the negative electrode current collector 2213 can be 13, 14, 15, 16, 17, 18, or 19, or a value within the range obtained by any combination of the above two values. For example, the ratio of the thickness of the positive electrode film layer 2111 to the thickness of the positive electrode current collector 2113 can be 7, 7.5, 8, 8.5, 9, or 9.5, or a value within the range obtained by any combination of the above two values.

[0251] Optionally, the battery cell 100 satisfies at least one of the following conditions: (1) the ratio of the thickness of the negative electrode film 2211 to the thickness of the negative electrode current collector 2213 is 13 to 18; (2) the ratio of the thickness of the positive electrode film 2111 to the thickness of the positive electrode current collector 2113 is 7 to 9.

[0252] Setting the ratio of the thickness of the positive electrode film layer 2111 / negative electrode film layer 2211 to the thickness of the positive electrode current collector 2113 / negative electrode current collector 2213 within the above range is beneficial to improving the energy density of the battery cell 100.

[0253] In some embodiments, the battery cell 100 satisfies at least one of the following conditions: (1) in the first direction X, the ratio of the size of the positive electrode film layer 2111 to the size of the housing 20 is 93.7% to 95.6%; (2) in the second direction Y, the ratio of the size of the positive electrode film layer 2111 to the size of the housing 20 is 92.8% to 95%.

[0254] For example, in the first direction X, the ratio of the size of the positive electrode film layer 2111 to the size of the housing 20 can be 93.7%, 94%, 94.2%, 94.5%, 94.8%, 95%, 95.5%, 95.6%, or a value within the range obtained by any combination of the above two values.

[0255] For example, in the second direction Y, the ratio of the size of the positive electrode film layer 2111 to the size of the housing 20 can be 92.8%, 93%, 93.2%, 93.5%, 93.7%, 94%, 94.5%, 94.8%, 95%, or a value within the range obtained by any combination of the above two values.

[0256] By setting the dimensional ratio of the positive electrode film layer 2111 and the housing 20 in the length direction (first direction X) and the width direction (second direction Y) within the above range, the space utilization rate inside the housing 20 can be improved, which is beneficial to improving the energy density of the battery cell 100.

[0257] In some embodiments, the battery cell 100 satisfies at least one of the following conditions: (1) the size of the positive electrode film layer 2111 in the first direction X is 421.5 mm to 621.5 mm; (2) the size of the positive electrode film layer 2111 in the second direction Y is 83.5 mm to 123.5 mm.

[0258] For example, the dimensions of the positive electrode film layer 2111 in the first direction X can be 421.5mm, 430mm, 450mm, 480mm, 500mm, 550mm, 600mm, 610mm, 620mm, 621.5mm, or a value within the range obtained by any combination of the above two values.

[0259] For example, the dimensions of the positive electrode film layer 2111 in the second direction Y can be 83.5mm, 86mm, 88mm, 90mm, 100mm, 105mm, 110mm, 115mm, 120mm, 123.5mm, or values ​​within the range obtained by any combination of the above two values.

[0260] Setting the dimensions of the positive electrode film layer 2111 in the length direction (first direction X) within the above range is beneficial to improving the energy density of the battery cell 100; setting the dimensions of the positive electrode film layer 2111 in the width direction (second direction Y) within the above range is beneficial to the full wetting of the positive electrode sheet 210 by the electrolyte, reducing internal resistance, accelerating the transport efficiency of lithium ions in the positive electrode material, thereby improving charge and discharge performance.

[0261] In some embodiments, the battery cell 100 satisfies at least one of the following conditions: (1) the ratio of the size of the main body portion 22 in the first direction X to the size of the main body portion 22 in the second direction Y is greater than 3; (2) the size of the main body portion 22 in the second direction Y is 90mm to 130mm.

[0262] For example, the ratio of the size of the main body portion 22 in the first direction X to the size of the main body portion 22 in the second direction Y can be 4, 5, 6, 7, or a value within the range obtained by any combination of the above two values.

[0263] For example, the dimensions of the main body 22 in the second direction Y can be 90mm, 100mm, 110mm, 120mm, 130mm, or values ​​within the range obtained by any combination of the above two values.

[0264] Setting the dimensions of the main body 22 in the width direction (second direction Y) within the aforementioned range, and limiting the ratio of the dimensions of the main body 22 in the first direction X to the dimensions in the second direction Y to be greater than 3, is beneficial for increasing the energy density of the battery cell 100, and also for ensuring sufficient wetting of the main body 22 by the electrolyte, reducing internal resistance, accelerating the transport efficiency of lithium ions in the electrode material, thereby improving charge and discharge performance.

[0265] Optionally, the ratio of the dimension of the main body 22 in the first direction X to the dimension of the main body 22 in the second direction Y is 4 to 6.

[0266] In some embodiments, refer to Figure 1-2 The main body 22 includes a first end face and a second end face disposed opposite to each other along a first direction X. The positive electrode tab 212 is located on the first end face and is welded to the positive end cap assembly 30, and the negative electrode tab 222 is located on the second end face and is welded to the negative end cap assembly 40. An insulating support member 50 is disposed between the first end face and the positive end cap assembly 30. The insulating support member 50 is provided with a receiving cavity corresponding to the positive electrode tab 212, and the receiving cavity is configured to retract at least a portion of the positive electrode tab 212.

[0267] The main body 22 of the electrode assembly 21 has a first end face and a second end face facing each other in the first direction X. A positive electrode tab 212 is disposed on the first end face side, and a negative electrode tab 222 is disposed on the second end face side. That is, the positive electrode tab 212 and the negative electrode tab 222 are disposed on different sides of the electrode assembly 21. Specifically, the first direction X is parallel to the length direction of the electrode assembly 21. In other words, the first direction X is parallel to the length direction of the battery cell 100, meaning that the positive electrode tab 212 and the negative electrode tab 222 are disposed at opposite ends of the battery cell 100 in the length direction.

[0268] It should be noted that the first end face and the second end face here are used only to refer to the different end faces of the main body 22 of the electrode assembly 21.

[0269] The positive electrode tab 212 and the negative electrode tab 222 are the core conductive connectors between the internal active material of the battery cell 100 and the external circuit, equivalent to the current inlet and outlet of the battery cell 100. Specifically, the positive electrode tab 212 extends from the positive electrode plate 210 in the main body 22 and is welded to the positive end cap assembly 30, and the negative electrode tab 222 extends from the negative electrode plate 220 in the main body 22 and is welded to the negative end cap assembly 40. In the assembly process of the battery cell 100 of this application, the two ends of the outer casing 10 have openings. Since the negative electrode tab 222, which is made of copper foil, is relatively soft, the negative electrode tab 222 is first welded to the negative end cap assembly 40. Then, one side of the unwelded positive electrode tab 212 passes through the outer casing 10 and is led out from the other opening. Finally, the positive electrode tab 212 is welded to the positive end cap assembly 30. In this process, since the positive electrode tab 212 needs to be passed through and led out from the outer casing 10, the positive electrode tab 212 needs to have a relatively long length. Since the positive electrode tab 212 is made of aluminum foil, it is relatively hard. After the battery cell 100 is assembled, the positive electrode tab 212 is prone to being inserted backward into the electrode assembly 21, which can damage the electrode assembly 21 and affect the performance of the battery cell 100.

[0270] Therefore, this application provides an insulating support 50 between the first end face and the positive end cap assembly 30. The insulating support 50 has a receiving cavity at the position corresponding to the positive electrode tab 212. The receiving cavity can be used to gather at least a part of the positive electrode tab 212. In this way, the longer positive electrode tab 212 in the assembled battery cell 100 will not be inserted into the electrode assembly 21 due to improper placement, thereby improving the safety performance of the battery cell 100.

[0271] The receiving cavity is configured to enclose at least a portion of the positive electrode tab 212, that is, either a portion of the positive electrode tab 212 can be housed in the receiving cavity, or all of the positive electrode tab 212 can be housed in the receiving cavity.

[0272] Figure 6 This is a structural schematic diagram of an insulating support member according to one embodiment of this application. Figure 6 As shown, the insulating support member 50 includes a first boss 510, a second boss 520, a first beam 530, and a second beam 540 facing the electrode assembly 21; the first boss 510 and the second boss 520 are disposed on both sides of the insulating support member 50 along the second direction Y, and the first beam 530 and the second beam 540 are disposed on both sides of the insulating support member 50 along the thickness direction Z of the battery cell and connect the first boss 510 and the second boss 520.

[0273] The insulating support 50 has a side facing the electrode assembly 21 and a side facing away from the electrode assembly 21. In other words, the side facing the electrode assembly 21 is the side facing away from the positive terminal cover assembly 30, and the side facing away from the electrode assembly 21 is the side facing the positive terminal cover assembly 30. That is to say, both the first boss 510 and the second boss 520 are disposed facing away from the positive terminal cover assembly 30.

[0274] The second direction Y is perpendicular to the first direction X and the thickness direction Z of the battery cell; that is, the second direction Y can be called the width direction X of the battery cell.

[0275] The first boss 510 and the second boss 520 are disposed on both sides of the insulating support 50 in the second direction Y, and the first beam 530 and the second beam 540 are disposed on both sides of the insulating support 50 in the thickness direction Z of the battery cell and connect the first boss 510 and the second boss 520. That is, the first boss 510, the second boss 520, the first beam 530 and the second beam 540 enclose and form a receiving cavity 550 for accommodating the positive electrode tab 212.

[0276] In the above solution, by providing a receiving cavity 550 formed by the first boss 510, the second boss 520, the first beam 530 and the second beam 540 on the side of the insulating support 50 facing the electrode assembly 21, the receiving cavity 550 is used to receive the positive electrode tab 212, which helps to reduce the risk of the positive electrode tab 212 being inserted backward into the electrode assembly 21, thereby improving the safety performance of the battery cell 100.

[0277] In some embodiments, in the first direction X, the dimensions of the first boss 510 and the second boss 520 are larger than the dimensions of the first beam 530 and the second beam 540.

[0278] In some embodiments, the first boss 510 and the second boss 520 have the same dimensions in the first direction X, and the first beam 530 and the second beam 540 have the same dimensions.

[0279] The first boss 510 and the second boss 520 are located at both ends of the insulating support 50, and the first beam 530 and the second beam 540 are located on both sides of the insulating support 50. When the size of the first boss 510 and the second boss 520 is larger than the size of the first beam 530 and the second beam 540, the insulating support 50 has a high and low structure, which can increase the space of the receiving cavity 550 so as to better accommodate the positive electrode tab 212, and also achieve the weight reduction of the insulating support 50.

[0280] In the above scheme, by making the dimensions of the first protrusion 510 and the second protrusion 520 in the first direction X larger than the dimensions of the first beam 530 and the second beam 540 in the first direction X, it is beneficial to increase the space of the receiving cavity 550, thereby better accommodating the positive electrode tab 212.

[0281] In some embodiments, the dimensions of the first boss 510 and the second boss 520 in the first direction X are 4mm to 10mm.

[0282] In some embodiments, the dimensions of the first beam 530 and the second beam 540 in the first direction X are 3mm to 8mm.

[0283] If the height of the insulating support 50 is insufficient, the space of the cavity 550 that accommodates the positive electrode tab 212 will be insufficient. This will not only fail to reduce the probability of the positive electrode tab 212 being inserted into the electrode assembly 21 in reverse, but the electrode assembly 21 will also be prone to shaking along the first direction X, and may even pull the positive electrode tab 212 to further increase the risk of the positive electrode tab 212 being inserted in reverse. If the height of the insulating support 50 is too high, the insulating support 50 will occupy too much space in the first direction X, which is not conducive to the energy density of the battery cell 100.

[0284] In the above scheme, by controlling the dimensions of the first protrusion 510, the second protrusion 520, the first beam 530 and the second beam 540 in the first direction X within the above range, the safety performance and energy density of the battery cell 100 can be balanced.

[0285] Specifically, in the first direction X, the dimensions of the first boss 510 and the second boss 520 can be 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, or their values ​​can be within the range obtained by any combination of the above two values.

[0286] Specifically, in the first direction X, the dimensions of the first beam 530 and the second beam 540 can be 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, or values ​​within the range obtained by any combination of the above two values.

[0287] Figure 7 This is a schematic diagram of the positive end cap assembly according to one embodiment of this application. Figure 8 This is a schematic diagram of the positive end cap assembly according to another embodiment of this application. Figure 9 This is an exploded view of the positive end cap assembly according to one embodiment of this application.

[0288] like Figure 7-9 As shown, in some embodiments, the positive terminal cap assembly 30 includes a positive terminal cap 310 and at least two positive terminals 320 disposed on the positive terminal cap 310.

[0289] In the above scheme, there are multiple positive terminals 320. The multiple positive terminals 320 are welded to the positive electrode tab 212, which can increase the flow area between the positive terminal 320 and the positive electrode tab 212, thereby reducing the heat generation at the weld between the positive electrode tab 212 and the positive terminal 320.

[0290] like Figure 9 As shown, in some embodiments, the positive terminal 320 includes a first portion 321 and a second portion 322 connected together. The first portion 321 is located on the side of the positive terminal cover 310 facing the electrode assembly 21 and is welded to the positive electrode tab 212. The second portion 322 is on the side opposite to the electrode assembly 21 and protrudes through the positive terminal cover 310. Along a first direction X, the projection of the first portion 321 covers the projection of the second portion 322; and / or, the positive electrode tab 212 is welded to at least two of the first portions 321.

[0291] The first part 321 and the second part 322, which are in a connected state, constitute the positive terminal 320. The first part 321 is disposed facing the electrode assembly 21 and is used for welding to the positive electrode tab 212; the second part 322 is disposed facing the positive terminal cover 310 and passes through the positive terminal cover 310.

[0292] The positive terminal cap assembly 30 includes a plurality of positive terminals 320, that is, a plurality of first portions 321. The positive terminal tab 212 is welded to at least two of the first portions 321 respectively to achieve welding of the positive terminal tab 212 to the positive terminal 320. In other words, at least two positive terminals 320 can be separately configured.

[0293] When multiple positive terminals 320 are separately arranged, on the one hand, from an assembly perspective, the separate arrangement facilitates assembly and reduces the difficulty of manufacturing the battery cell 100; on the other hand, when the positive electrode tab 212 is welded to the first part 321, due to the characteristics of the metal material, the first part 321 will generate heat when current flows through it, and the first part 321 will expand and generate stress. The weld between the positive electrode tab 212 and the first part 321 cannot withstand this stress, which will lead to loosening or breakage between the positive electrode tab 212 and the first part 321. Therefore, when the positive electrode tab 212 is welded to the separate first part 321 separately, the thermal expansion and stress generated by each first part 321 can be alleviated, thereby reducing the possibility of cracking between the positive electrode tab 212 and the positive terminal 320.

[0294] In the above scheme, the positive terminal 320 includes a first portion 321 welded to the positive electrode tab 212 and a second portion 322 protruding towards and penetrating the positive terminal cover 310. The positive terminal cover assembly 30 includes at least two first portions 321, and the positive electrode tab 212 is welded to each of the at least two first portions 321. This helps to alleviate the thermal expansion and stress generated by the positive terminal 320 and reduces the possibility of cracking in the connection area between the positive electrode tab 212 and the positive terminal 320, thereby ensuring the normal performance of the battery cell 100.

[0295] In some embodiments, the first part 321 and the second part 322 are an integral structure.

[0296] In the above scheme, by making the first part 321 and the second part 322 of the positive terminal 320 into an integrated structure, it is more conducive to electron transmission, thereby reducing the heat generated at the positive terminal 320 of the battery cell 100 during charging.

[0297] like Figure 9 As shown, in some embodiments, the positive terminal 320 includes a first positive terminal 323 and a second positive terminal 324, and the positive terminal cover assembly 30 includes a first busbar component 330, which is disposed on the side of the positive terminal cover 310 away from the electrode assembly 21. The first busbar component 330 includes a first through hole 331 and a second through hole 332. The second part 322 of the first positive terminal 323 passes through the first through hole 331 along the first direction X and is connected to the first busbar component 330. The second part 322 of the second positive terminal 324 passes through the second through hole 332 and is connected to the first busbar component 330.

[0298] The first busbar component 330 is located on the side of the positive terminal cover 310 away from the electrode assembly 21. It can both fix and protect the positive terminal 320, and also provide a larger welding area for subsequent connection with other components.

[0299] The first busbar component 330 has a through hole through which the second portion 322 of the positive terminal 320 passes. Exemplarily, the first busbar component 330 is provided with a first through hole 331, and the positive terminal cap 310 is provided with a hole corresponding to the first through hole 331. The second portion 322 of the first positive terminal 323 passes through the hole on the positive terminal cap 310 and the first through hole 331 on the first busbar component 330, and remains connected to the first busbar component 330. The second positive terminal 324 is connected to the second through hole 332 of the first busbar component 330 in the same way, which will not be described in detail here.

[0300] Along the first direction X, the electrode assembly 21, the first part 321 of the positive terminal 320, the second part 322 of the positive terminal 320, the positive terminal cover 310 and the first busbar component 330 are arranged in sequence, wherein the second part 322 of the positive terminal 320 passes through the positive terminal cover 310 and the first busbar component 330.

[0301] In the above scheme, the positive terminal cover assembly 30 includes a first busbar component 330, and at least two positive terminals 320 pass through the positive terminal cover 310 and the through holes on the first busbar component 330 to connect with the first busbar component 330, thereby ensuring the normal function of the battery cell 100.

[0302] In some embodiments, the size of the first portion 321 in the first direction X is 1 mm to 1.5 mm.

[0303] In the above scheme, the first part 321 is used to weld with the positive electrode tab 212. By making the thickness of the first part 321 1mm~1.5mm, the positive electrode tab 212 can be firmly connected with the first part 321.

[0304] Specifically, in the first direction X, the size of the first part 321 can be 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, or a value within the range obtained by any combination of the above two values.

[0305] In some embodiments, the total cross-sectional area of ​​the first part 321 is 70 mm². 2 ~210mm 2 .

[0306] In the above scheme, the first part 321 is used for welding with the positive electrode tab 212, so that the total current-passing cross-sectional area of ​​the multiple first parts 321 is 70mm². 2 ~210mm 2 This allows the positive electrode tab 212 to be firmly connected to the first part 321, and also gives the first part 321 a better current-carrying capacity.

[0307] Specifically, the total cross-sectional area of ​​the first part 321 can be 70 mm². 2 90mm 2 110mm 2 130mm 2 150mm 2 160mm 2 180mm 2 190mm 2 200mm 2 210mm 2 , or its value is within the range obtained by combining any two of the above values.

[0308] It should be noted that the positive terminal cover assembly 30 includes multiple positive terminals 320, and each positive terminal 320 includes a first portion 321. Therefore, the total current-carrying cross-sectional area of ​​the first portion 321 here refers to the sum of the current-carrying cross-sectional areas of the multiple first portions 321, that is, the sum of the cross-sectional areas of the multiple first portions 321 perpendicular to the current direction.

[0309] Figure 10 This is a schematic diagram of the structure of the first insulating member according to an embodiment of this application.

[0310] Please combine Figure 6-10In some embodiments, the positive terminal cover assembly 30 includes a first insulating member 340; the first insulating member 340 is disposed between the insulating support member 50 and the positive terminal cover 310 for insulating the electrode assembly 21 and the positive terminal cover 310.

[0311] In the above solution, by setting a first insulating member 340 between the positive terminal cover 310 and the insulating support member 50, the positive terminal 320 and the cover surrounding the positive terminal 320 can be insulated, reducing the risk of short circuit between the positive and negative terminals; and the first insulating member 340 occupies part of the space in the first direction X, which can reduce the movement space of the electrode assembly 21 in the first direction X, and reduce the risk of electrode damage caused by the electrode assembly 21 hitting the positive terminal cover 310 when the battery cell 100 is vibrated during use.

[0312] In some embodiments, the first insulating member 340 includes a first wall 341 that abuts against the positive terminal cap 310 and a first recess 342 facing the electrode assembly; the first wall 341 is provided with a first straight portion 3411 and a third through hole 3412 through which the second portion 322 passes, and the first recess 342 is used to receive at least a portion of the first portion 321.

[0313] The first wall 341 is provided with a first straight part 3411 and a third through hole 3412. It can be understood that the first wall 341 is provided with the first straight part 3411 except for the third through hole 3412.

[0314] The first part 321 is used for welding to the positive electrode tab 212. The first part 321 is at least partially accommodated in the first recess 342. The second part 322, which is integral with the first part 321, passes through the third through hole 3412 on the first wall 341 to connect to the first busbar component 330.

[0315] In the above scheme, the above arrangement can further save the internal space of the battery cell 100 occupied by the first insulating member 340 in the first direction X, and further improve the energy density of the battery cell 100; and the first part 321 is just accommodated in the first recess 342 of the first insulating member 340. The first recess 342 can limit the positive terminal 320, reduce the left and right shaking of the positive terminal 320 and the pulling of the welding connection area with the positive electrode tab 212.

[0316] Figure 11 This is a cross-sectional view of a battery cell according to one embodiment of this application.

[0317] like Figure 11 As shown, in some embodiments, at least a portion of the first boss 510 and / or the second boss 520 abuts against the first insulating member 340.

[0318] It should be understood that "abutment" refers to two parts maintaining a relatively fixed position or stress state through direct contact. That is to say, after the battery cell 100 is assembled, the first insulating member 340 is in contact with the insulating support member 50 and maintains structural stability. More specifically, the first straight portion 3411 of the first insulating member 340 abuts against the first boss 510 and / or the second boss 520.

[0319] In the above scheme, by making the insulating support 50 abut against the first insulating member 340, the internal space of the battery cell 100 occupied by the first insulating member 340 in the first direction X can be further saved, which helps to improve the energy density of the battery cell 100; and the two can maintain the stability of the structure through direct contact.

[0320] In some embodiments, the size of the first straight portion 3411 in the first direction X is 1 mm to 3 mm.

[0321] It should be noted that, because the first recess 342 is a cavity structure, its dimensions in the first direction X cannot be accurately described. Therefore, the dimensions of the first straight portion 3411 in the first direction X can be understood as the dimensions of the first insulating member 340 in the first direction X.

[0322] If the height of the first insulating member 340 in the first direction X is insufficient, the insulation capacity will decrease. Once the material ages and fails, the risk of short circuit in the battery cell 100 will increase, which is detrimental to the safety performance of the battery cell 100. Furthermore, if the length occupied by the first insulating member 340 in the first direction X is too small, the space that the electrode assembly 21 can move in the first direction X will increase. The electrode assembly 21 will shake and pull the positive electrode tab 212, thereby increasing the risk of electrode damage, which is also detrimental to the safety performance of the battery cell 100. If the height of the first insulating member 340 in the first direction X is too high, it will occupy too much space inside the battery cell 100, which is detrimental to the energy density of the battery cell 100.

[0323] In the above solution, by limiting the size of the first straight portion 3411 in the first direction X within the above range, it is beneficial to balance the safety performance and energy density of the battery cell 100.

[0324] Specifically, in the first direction X, the dimensions of the first straight portion 3411 can be 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.1mm, 2.3mm, 2.5mm, 2.7mm, 3mm, or a value within the range obtained by any combination of the above two values.

[0325] Please continue to refer to Figure 9In some embodiments, the positive end cap 310 includes a pressure relief mechanism 311; a fourth through hole 343 corresponding to the pressure relief mechanism 311 is provided on the first straight portion 3411, and a fifth through hole 560 corresponding to the fourth through hole 343 is provided on the first boss 510.

[0326] When a fault occurs inside the battery cell 100, such as overcharging, short circuit, or thermal runaway, a large amount of gas is generated, causing the pressure to rise drastically. The internal pressure can be released through the pressure relief mechanism 311 to prevent the battery cell 100 from exploding or rupturing violently.

[0327] Therefore, when a pressure relief mechanism 311 is provided on the positive terminal cover 310, corresponding through holes need to be provided on the first insulating member 340 and the insulating support member 50 to ensure the normal function of the pressure relief mechanism 311. Specifically, when a fault occurs inside the battery cell, the gas can smoothly reach the pressure relief mechanism 311 through the fifth through hole 560 and the fourth through hole 343 in sequence.

[0328] This application does not limit the specific structure of the fifth through hole 560 and the fourth through hole 343. For example, they can be as follows: Figure 6 or Figure 9 As shown, multiple small holes respectively form the fifth through hole 560 and the fourth through hole 343, or they can be formed by a single large hole. In production, the configuration can be changed according to actual needs.

[0329] In the above scheme, by setting a pressure relief mechanism 311 on the positive terminal cover 310, and correspondingly setting a fifth through hole 560 and a fourth through hole 343, when a large amount of gas is generated inside the battery cell 100 due to a fault, the gas can be discharged in time to ensure the safety performance of the battery cell 100.

[0330] Figure 12 This is a schematic diagram of the structure of the positive electrode sheet according to one embodiment of this application. Figure 12 As shown, in some embodiments, the main body 22 includes a positive electrode body 211, and a positive electrode tab 212 extends from the positive electrode body 211 along a first direction X; in the second direction Y, the ratio of the size of the positive electrode tab 212 to the size of the positive electrode body 211 is greater than 50%.

[0331] The electrode assembly 21 includes a main body 22, a positive electrode tab 212, and a negative electrode tab 222. The main body 22 includes a positive electrode body 211 and a negative electrode body 222. That is, the positive electrode body 211 and the positive electrode tab 212 form the positive electrode 210, and the negative electrode body 211 and the negative electrode tab 222 form the negative electrode 220. Specifically, the positive electrode tab 212 extends from the positive electrode body 211, and the negative electrode tab 222 extends from the negative electrode body.

[0332] The second direction Y is the width direction of the battery cell 100. In the second direction Y, the ratio of the size of the positive electrode tab 212 to the size of the positive electrode body 211 is greater than 50%, that is, the width ratio of the positive electrode tab 212 to the width of the positive electrode body 211 is greater than 50%.

[0333] The wider the positive electrode tab 212, the better it is for overcurrent, heat conduction, reducing the temperature inside the battery cell 100 during charging and reducing the risk of electrolyte decomposition and gas generation. However, the wider the positive electrode tab 212, the larger the space it needs to occupy for the tab, which will affect the energy density of the battery cell 100.

[0334] In the above scheme, by making the size ratio of the positive electrode tab 212 to the positive electrode body 211 greater than 50% in the width direction Y of the battery cell, the current flow area at the positive electrode tab 212 can be increased, the impedance and heat generation at the positive electrode tab 212 can be reduced, and the energy density of the battery cell 100 can also be taken into account.

[0335] Specifically, in the second direction Y, the ratio of the size of the positive electrode tab 212 to the size of the positive electrode body 211 can be 50%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or a value within the range obtained by any combination of the above two values.

[0336] Optionally, in the second direction Y, the ratio of the size of the positive electrode tab 212 to the size of the positive electrode body 211 is 60% to 100%.

[0337] Figure 13 This is a schematic diagram of the structure of a battery cell according to another embodiment of this application.

[0338] like Figure 13 As shown, the battery cell 100 includes a plurality of positive electrode plates 210, and the positive electrode tab 212 formed by each positive electrode plate 210 is housed inside the battery cell 100. Therefore, the size of each positive electrode tab 212 inside the battery cell 100 is within the aforementioned range.

[0339] In some implementations, the size of the positive electrode tab can be detected by disassembling the battery cell at 0% SOC to obtain the positive electrode sheet. The positive electrode tab on the positive electrode sheet is divided into two parts: a first positive electrode tab not welded to the positive terminal and a second positive electrode tab welded to the positive terminal. The dimensions of the first and second positive electrode tabs are measured separately, and their sum is calculated as the size of the corresponding positive electrode tab. Additionally, if the first positive electrode tab is in a curled-up state, it needs to be unfolded before measuring the corresponding size.

[0340] It should be noted that, unless otherwise specified, the dimensions of the positive electrode tab mentioned in the embodiments of this application include the sum of the dimensions of the first positive electrode tab and the second positive electrode tab. The dimensions of the first positive electrode tab and the second positive electrode tab must be the absolute length dimensions obtained after being completely flattened. The same applies to the negative electrode tab described below.

[0341] Specifically, in the first direction X, the size of the positive electrode tab 212 can be 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, or 55mm, or a value within the range obtained by any combination of the above two values.

[0342] Please continue to refer to Figure 11 and Figure 12 In some embodiments, the first portion 321 has a first surface 3211 close to the electrode assembly 21; in the first direction X, the dimension between the edge of the positive electrode film layer 2111 and the first surface 3211 is 7 mm to 10 mm.

[0343] The first part 321 has a surface close to the electrode assembly 21 and a surface away from the electrode assembly 21. The surface of the first part 321 close to the electrode assembly 21 is connected to the positive electrode tab 212, that is, the first surface 3211 of the first part 321 is connected to the positive electrode tab 212.

[0344] The positive electrode tab 212 extends from the positive electrode body 211, is gathered in the insulating support 50, and then connects to the first surface 3211 of the first part 321. That is, the dimension between the edge of the positive electrode film layer 2111 and the first surface 3211 is the space for folding the positive electrode tab.

[0345] The larger the space of the positive electrode tab, the lower the risk of reverse insertion of the positive electrode tab 212, but the more space it occupies inside the battery cell 100, which is not conducive to the energy density of the battery cell.

[0346] In the above scheme, by limiting the size of the positive electrode tab space to 7mm~10mm, the risk of reverse insertion of the positive electrode tab 212 can be reduced, while also taking into account the energy density of the battery cell 100.

[0347] Specifically, in the first direction X, the dimension between the edge of the positive electrode film layer 2111 and the first surface 3211 can be 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, or a value within the range obtained by any combination of the above two values.

[0348] In some embodiments, the total area of ​​the first welding region formed by welding the positive electrode tab 212 to the first portion 321 is 130 mm². 2 ~200mm 2 .

[0349] The total area of ​​the first welding area can represent the current flow area between the positive electrode tab 212 and the positive terminal 320. If the total area of ​​the first welding area is too small, it is not conducive to reducing the electron transmission impedance and reducing the heat generated by the battery cell 100 during the charging process. However, if the total area of ​​the first welding area is too large, it may squeeze other structural components, causing safety hazards inside the battery cell 100.

[0350] In the above scheme, the welding area between the positive electrode tab 212 and the first part 321 is kept at 130 mm². 2 ~200mm 2 This ensures both normal current transmission and the safety performance of the individual battery cells.

[0351] It should be noted that the "total area" here refers to the sum of the welding areas of the positive electrode tab 212 and at least two first portions 321. The positive electrode cap assembly 30 includes at least two positive terminals 320, and the positive electrode tab 212 is welded to each of the at least two positive terminals 320 respectively. The sum of the welding areas formed after each welding should fall within the aforementioned range. Furthermore, the welding area of ​​the positive electrode tab 212 to each first portion 321 can be the same or different, and can be adjusted according to the manufacturing process.

[0352] Specifically, the total area of ​​the first welding region formed by welding the positive electrode tab 212 and the first part 321 can be 130 mm². 2 135mm 2 140mm 2 145mm 2 150mm 2 155mm 2 160mm 2 170mm 2 180mm 2 190mm 2 200mm 2 , or its value is within the range obtained by combining any two of the above values.

[0353] Please continue to refer to Figure 12 In some embodiments, the positive electrode body 211 has a chamfered structure 213 at the apex corner on the second end face side.

[0354] The electrode assembly 21 has a first end face and a second end face that are disposed opposite to each other in the first direction X. The first end face is provided with a positive electrode tab 212, and the second end face is provided with a negative electrode tab 222. That is, the positive electrode body 211 is provided with a chamfer structure 213 on the side where the positive electrode tab 212 is not provided, and the chamfer structure 213 is provided at the top corner of the end face.

[0355] The “beveled structure” 213 here refers to cutting off the top corner and processing the originally sharp top corner into a gentle slope or arc surface, which can eliminate potential safety hazards.

[0356] In the above scheme, the positive electrode 210 has a higher hardness than the negative electrode 220. Therefore, during the fabrication of the stacked electrode assembly 21, the sharp corners of the positive electrode 210 are more likely to pierce the separator 230, leading to a short circuit between the positive and negative electrodes. Therefore, by providing a chamfered structure 213 on the side of the positive electrode 210 where the positive electrode tab 212 is not provided, the risk of the sharp corners of the positive electrode 210 piercing the separator 230 due to its higher hardness can be reduced, which is beneficial to improving the safety performance of the battery cell 100.

[0357] In some embodiments, the chamfered structure 213 has a larger dimension on the extension of the second direction Y than on the extension of the first direction X.

[0358] like Figure 12 As shown, the chamfered structure 213 is actually the part that has been cut off. Therefore, this application uses the dimension on the extension line of the first direction X to represent the dimension of the cut-off chamfered structure 213 in the first direction X, and the same applies to the extension line of the second direction Y.

[0359] In the above scheme, the positive electrode 210 has a greater risk of piercing the separator 230 in the second direction Y (width direction). Therefore, by making the dimension of the chamfered structure 213 on the extension line of the second direction Y larger than its dimension on the extension line of the first direction X (length direction), it is more beneficial to reduce the risk of the sharp corner of the positive electrode 210 piercing the separator 230 and thus improve the safety performance of the battery cell 100.

[0360] In some embodiments, the chamfer structure 213 has a size of 1mm to 2mm along the extension of the first direction X; and a size of 1mm to 10mm along the extension of the second direction Y.

[0361] If the size of the chamfer structure 213 is too small, it will not be able to reduce the risk of puncturing the separator 230; if the size of the chamfer structure 213 is too large, it will affect the energy density of the battery cell 100.

[0362] In the above scheme, by controlling the size of the chamfered structure 213 within the above range, it is beneficial to balance the energy density and safety performance of the battery cell 100.

[0363] Specifically, on the extension line of the first direction X, the dimensions of the chamfer structure 213 can be 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.7mm, 1.8mm, or 2mm, or values ​​within the range obtained by any combination of the above two values; on the extension line of the second direction Y, the dimensions of the chamfer structure 213 can be 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm, or values ​​within the range obtained by any combination of the above two values.

[0364] Please continue to refer to Figure 12 In some embodiments, the chamfered structure 213 is a fan-shaped structure.

[0365] In the above scheme, the chamfered structure 213 with a fan shape can minimize the risk of puncturing the isolation membrane 230.

[0366] Please continue to refer to Figure 12 In some embodiments, the positive electrode body 211 further includes a first transition region 2112 along the first direction X. The first transition region 2112 is located at one end of the positive electrode film layer 2111 near the positive electrode tab 212 and is adjacent to the positive electrode film layer 2111. The first transition region 2112 is provided with an insulating material.

[0367] The positive electrode body 211 includes a positive electrode film layer 2111 for coating a positive electrode active material and a first transition region 2112 for providing an insulating material. In terms of position, it can be described that the positive electrode film layer 2111, the first transition region 2112 and the positive electrode tab 212 are arranged sequentially along the first direction X.

[0368] In the above scheme, by setting a first transition region 2112 coated with insulating material on the side of the positive electrode sheet 210 near the positive electrode tab 212, the risk of short circuit between the positive and negative electrodes caused by burrs piercing the separator 230 when cutting the positive electrode tab 212 can be reduced during the preparation of the battery cell 100, thereby further improving the safety performance of the battery cell 100.

[0369] Specifically, the insulating material may include at least one of alumina, boehmite, magnesium oxide, polyacrylate, and polyvinylidene fluoride. The binder may include at least one of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and vinylidene fluoride-chlorotrifluoroethylene copolymer.

[0370] In some embodiments, the size of the first transition region 2112 in the first direction X is 1.5 mm to 4 mm.

[0371] In the first direction X, if the size of the first transition region 2112 is too small, it cannot prevent the burrs generated during cutting from piercing the separator 230; if the size of the first transition region 2112 is too large, it will affect the energy density of the battery cell 100.

[0372] In the above scheme, by controlling the size of the first transition region 2112 to 1.5mm~4mm in the first direction X, it is beneficial to balance the safety performance and energy density of the battery cell 100.

[0373] Specifically, in the first direction X, the size of the first transition region 2112 can be 1.5mm, 1.8mm, 2mm, 2.5mm, 2.6mm, 3mm, 3.2mm, 3.5mm, 4mm, or a value within the range obtained by any combination of the above two values.

[0374] like Figure 12 As shown, in some embodiments, the positive electrode tab 212 further includes a second transition region 2121 along the first direction X. The second transition region 2121 is located at one end of the positive electrode tab 212 near the positive electrode body portion 211 and is adjacent to the first transition region 2112. The second transition region 2121 is provided with insulating material.

[0375] That is, along the first direction X, the positive electrode film layer 2111, the first transition region 2112, the second transition region 2121 and the positive electrode tab 212 without insulating material are arranged in sequence.

[0376] In the above scheme, a second transition region 2121 coated with insulating material is provided at the root of the positive electrode tab 212, which helps to reduce the risk of burrs generated at the root of the tab 212 during cutting of the positive electrode tab 212 piercing the separator 230 and causing a short circuit between the positive and negative electrodes, thereby further improving the safety performance of the battery cell 100.

[0377] In some embodiments, the size of the second transition region 2121 in the first direction X is 4mm to 7mm.

[0378] In the first direction X, if the size of the second transition region 2121 is too small, it cannot prevent the burrs generated during cutting from piercing the separator 230; if the size of the second transition region 2121 is too large, it will have a significant impact on the energy density of the battery cell 100.

[0379] In the above scheme, by controlling the size of the second transition region 2121 to 4mm~7mm in the first direction X, it is beneficial to balance the safety performance and energy density of the battery cell 100.

[0380] Specifically, in the first direction X, the size of the second transition region 2121 can be 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 6.8mm, 7mm, or a value within the range obtained by any combination of the above two values.

[0381] In some embodiments, in the first direction X, the size ratio of the second transition region 2121 to the positive electrode tab 212 is 1 / 6 to 1 / 3.

[0382] In the above scheme, by keeping the size ratio of the second transition region 2121 to the positive electrode tab 212 within the above range, the safety performance of the battery cell 100 can be improved, and the positive electrode tab 212 can be guaranteed to have normal overcurrent capacity.

[0383] Specifically, in the first direction X, the size ratio of the second transition region 2121 to the positive electrode tab 212 can be 1 / 6, 1 / 5, 2 / 9, 1 / 4, 1 / 3, or its value is within the range obtained by any combination of the above two values.

[0384] Figure 14 This is an exploded view of the negative end cap assembly according to one embodiment of this application. Figure 14 As shown, the negative terminal cover assembly 40 includes a negative terminal cover 410 and at least two negative terminals 420 disposed on the negative terminal cover 410.

[0385] In the above scheme, the negative terminal 420 has at least two, and multiple negative terminals 420 are welded to the negative electrode tab 222, which can increase the flow area between the negative terminal 420 and the negative electrode tab 222, thereby reducing the heat generation at the weld between the negative terminal 420 and the negative electrode tab 222.

[0386] In some embodiments, the negative terminal 420 includes a connected third portion 421 and a fourth portion 422, the third portion 421 being located on the side of the negative terminal cover 410 facing the electrode assembly 21 and welded to the negative electrode tab 222, the fourth portion 422 being on the side away from the electrode assembly 21 and protruding through the negative terminal cover 410, the projection of the third portion 421 covering the projection of the fourth portion 422 along a first direction X; and / or, the negative electrode tab 222 being welded to at least two of the third portions 421.

[0387] The third part 421 and the fourth part 422, in the connected state, constitute the negative terminal 420. The third part 421 is disposed facing the electrode assembly 21 and is used for welding to the negative electrode tab 222; the fourth part 422 is disposed facing the negative terminal cover 410 and passes through the negative terminal cover 410.

[0388] The negative terminal cap assembly 40 includes a plurality of negative terminals 420, that is, a plurality of third parts 421. The negative terminal tab 222 is welded to at least two of the third parts 421 respectively to achieve welding between the negative terminal tab 222 and the negative terminal 420. In other words, at least two negative terminals 420 can be separately configured.

[0389] When at least two negative terminals 420 are separately configured, on the one hand, from an assembly perspective, the separate configuration facilitates assembly and reduces the difficulty of manufacturing the battery cell 100; on the other hand, when the negative electrode tab 222 is welded to the third part 421, due to the characteristics of the metal material, the third part 421 will generate heat when current flows through it, and the third part 421 will expand and generate stress. The weld between the negative electrode tab 222 and the third part 421 cannot withstand this stress, which will lead to loosening or breakage between the negative electrode tab 222 and the third part 421. Therefore, when the negative electrode tab 222 is welded to the separate third part 421 separately, the thermal expansion and stress generated by the third part 421 can be alleviated, thereby reducing the possibility of cracking between the negative electrode tab 222 and the negative terminal 420.

[0390] In the above scheme, the negative terminal 420 includes a third part 421 welded to the negative electrode tab 222 and a fourth part 422 protruding towards and penetrating the negative terminal cover 410. The negative terminal cover assembly 40 includes at least two third parts 421, and the negative electrode tab 222 is welded to each of the at least two third parts 421. This helps to alleviate the thermal expansion and stress generated by the negative terminal cover 410 and reduces the possibility of cracking in the connection area between the negative electrode tab 222 and the negative terminal 420, thereby ensuring the normal performance of the battery cell 100.

[0391] In some embodiments, the third part 421 and the fourth part 422 are an integral structure.

[0392] In the above scheme, by making the third part 421 and the fourth part 422 of the negative terminal 420 into an integrated structure, it is more conducive to electron transmission, thereby reducing the heat generated at the negative terminal 420 of the battery cell 100 during charging.

[0393] In some embodiments, the negative terminal 420 includes a first negative terminal 423 and a second negative terminal 424, and the negative terminal cover assembly 40 includes a second busbar 430, which is disposed on the side of the negative terminal cover 410 away from the electrode assembly 21. The second busbar 430 includes a sixth through hole 431 and a seventh through hole 432. The fourth portion 422 of the first negative terminal 423 passes through the sixth through hole 431 along the first direction X and is connected to the second busbar 430. The fourth portion 422 of the second negative terminal 424 passes through the seventh through hole 432 and is connected to the second busbar 430.

[0394] The second busbar component 430 is located on the side of the negative terminal cover 410 away from the electrode assembly 21. It can both fix and protect the negative terminal 420, and also provide a larger welding area for subsequent connection with other components.

[0395] The second busbar component 430 has a through hole through which the fourth portion 422 of the negative terminal 420 passes. Exemplarily, the second busbar component 430 is provided with a sixth through hole 431, and the negative terminal cap 410 is provided with a hole corresponding to the sixth through hole 431. The fourth portion 422 of the first negative terminal 423 passes through the hole on the negative terminal cap 410 and the sixth through hole 431 on the second busbar component 430, and remains connected to the second busbar component 430. The connection method between the second negative terminal 424 and the seventh through hole 432 of the second busbar component 430 is the same, and will not be described in detail here.

[0396] Along the first direction X, the electrode assembly 21, the third part 421 of the negative terminal 420, the fourth part 422 of the negative terminal 420, the negative terminal cover 410, and the second busbar component 430 are arranged in sequence, wherein the fourth part 422 of the negative terminal 420 passes through the negative terminal cover 410 and the second busbar component 430.

[0397] In the above scheme, the negative terminal cover assembly 40 includes a second busbar component 430, and at least two negative terminals 420 pass through through holes on the negative terminal cover 410 and the second busbar component 430 to connect with the second busbar component 430, thereby ensuring the normal function of the battery cell 100.

[0398] In some embodiments, the third portion 421 has a size of 1.2 mm to 2.5 mm in the first direction X.

[0399] In the above scheme, the third part 421 is used to weld with the negative electrode tab 222. By making the thickness of the third part 421 1.2mm~2.5mm, the negative electrode tab 222 can be firmly connected to the third part 421.

[0400] Specifically, in the first direction X, the dimensions of the third part 421 can be 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, or values ​​within the range obtained by any combination of the above two values.

[0401] In some embodiments, the total cross-sectional area of ​​the third part 421 is 70 mm². 2 ~210mm 2 .

[0402] In the above scheme, the third part 421 is used for welding with the negative electrode tab 222, so that the total current-passing cross-sectional area of ​​the multiple third parts 421 is 70mm². 2 ~210mm 2 This allows the negative electrode tab 222 to be firmly connected to the third part 421, and also gives the third part 421 a better current-carrying function.

[0403] Specifically, the total cross-sectional area of ​​the third part 421 can be 70 mm². 2 90mm 2 110mm 2 130mm 2 150mm 2 160mm 2 180mm 2 190mm 2 200mm 2 210mm 2 , or its value is within the range obtained by combining any two of the above values.

[0404] It should be noted that the negative terminal cover assembly 40 includes multiple negative terminals 420, and each negative terminal 420 includes a third part 421. Therefore, the total current-carrying cross-sectional area of ​​the third part 421 here refers to the sum of the current-carrying cross-sectional areas of the multiple third parts 421, that is, the sum of the cross-sectional areas of the multiple third parts 421 perpendicular to the current direction.

[0405] Please continue to refer to Figure 1 In some embodiments, the negative terminal cap assembly 40 includes a second insulating member 440; the second insulating member 440 is disposed between the electrode assembly 21 and the negative terminal cap 410 for insulating the electrode assembly 21 and the negative terminal cap 410.

[0406] In the above solution, by providing a second insulating member 440 between the negative terminal cover 410 and the electrode assembly 21, the negative terminal 420 and the cover surrounding the negative terminal 420 can be insulated, reducing the risk of short circuit between the positive and negative terminals; and the second insulating member 440 occupies part of the space in the first direction X, which can reduce the movement space of the electrode assembly 21 in the first direction X, reducing the risk of electrode assembly 21 impacting the negative terminal cover 410 and causing electrode damage when the battery cell 100 vibrates during use.

[0407] Figure 15 This is a schematic diagram of the structure of the second insulating member according to an embodiment of this application.

[0408] Please combine Figure 14 and Figure 15In some embodiments, the second insulating member 440 includes a second wall 441 that abuts against the negative terminal cap 410 and a second recess 442 facing the electrode assembly; the second wall 441 is provided with a second straight portion 4411 and an eighth through hole 4412 through which the fourth portion 422 passes, and the second recess 442 is used to accommodate at least a portion of the third portion 421 and at least a portion of the negative electrode tab 222.

[0409] The second wall 441 is provided with a second straight section 4411 and an eighth through hole 4412. It can be understood that the second wall 441 is provided with the second straight section 4411 except for the eighth through hole 4412.

[0410] The third part 421 is used for welding to the negative electrode tab 222. The third part 421 is at least partially accommodated in the second recess 442. The fourth part 422, which is integral with the third part 421, passes through the eighth through hole 4412 on the second wall 441 to connect with the second busbar 430.

[0411] To meet the assembly requirements of the battery cell 100, the positive electrode tab 212 needs to be longer. Therefore, an insulating support 50 is provided between the electrode assembly 21 and the first insulating member 340 to hold the positive electrode tab 212 in place. However, the negative electrode tab 222 is shorter, so no additional support is needed on the negative side to accommodate it. The shorter negative electrode tab 222 can be housed in the second recess 442 of the second insulating member 440, which can further improve the energy density of the battery cell 100.

[0412] In the above scheme, the above settings can further save the internal space of the battery cell 100 occupied by the second insulating member 440 in the first direction X, and further improve the energy density of the battery cell 100; and the third part 421 is just accommodated in the second recess 442 of the second insulating member 440 and the negative electrode tab 222. The second recess 442 can limit the negative terminal 420, reducing the left and right shaking of the negative terminal 420 and the pulling of the welding connection area with the negative electrode tab 222.

[0413] Figure 16 This is a cross-sectional view of a battery cell according to another embodiment of this application. Figure 16 As shown, in some embodiments, the side of the second insulating member 440 near the electrode assembly 21 abuts against at least a portion of the electrode assembly 21.

[0414] The second insulating member 440 abuts against at least a portion of the electrode assembly 21 on the side near the electrode assembly 21. More specifically, the second straight portion 4411 abuts against at least a portion of the electrode assembly 21. The second straight portion 4411 has a side away from the electrode assembly 21 and a side near the electrode assembly 21. A negative terminal cap 410 is provided on the side away from the electrode assembly 21. When the second straight portion 4411 abuts against the electrode assembly 21, the structural components on the negative terminal side are arranged more compactly, without occupying too much space inside the battery cell 100, which is beneficial to improving the energy density of the battery cell 100.

[0415] In the above scheme, the negative electrode tab 222 is housed in the second recess 442 and connected to the third part 421 of the negative terminal 420. By having the second insulating member 440 partially abut against the electrode assembly 21, it is beneficial to further improve the energy density of the battery cell 100. Furthermore, the second insulating member 440 is fixed inside the battery cell 100. When at least part of the electrode assembly 21 abuts against the second insulating member 440, the possibility of the electrode assembly 21 swaying along the first direction X can be reduced.

[0416] In some embodiments, the second straight portion 4411 has a size of 6 mm to 9 mm in the first direction X.

[0417] It should be noted that, because the second recess 442 is a cavity structure, its dimensions in the first direction X cannot be accurately described. Therefore, the dimensions of the second straight portion 4411 in the first direction X can be understood as the dimensions of the second insulating member 440 excluding the second recess 442 in the first direction X.

[0418] If the height of the second insulating member 440 in the first direction X is insufficient, the insulation capacity will decrease. Once the material ages and fails, the risk of short circuit in the battery cell 100 will increase, which is detrimental to the safety performance of the battery cell 100. Furthermore, if the length occupied by the second insulating member 440 in the first direction X is too small, the space that the electrode assembly 21 can move in the first direction X will increase. The electrode assembly 21 will shake and pull the negative electrode tab 222, thereby increasing the risk of electrode damage, which is also detrimental to the safety performance of the battery cell 100. If the height of the second insulating member 440 in the first direction X is too high, it will occupy too much space inside the battery cell 100, which is detrimental to the energy density of the battery cell 100.

[0419] In the above solution, by limiting the size of the second straight portion 4411 in the first direction X within the above range, it is beneficial to balance the safety performance and energy density of the battery cell 100.

[0420] Specifically, in the first direction X, the dimensions of the second straight portion 4411 can be 6mm, 6.2mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 8.6mm, 9mm, or values ​​within the range obtained by any combination of the above two values.

[0421] Please continue to refer to Figure 14 and 15 ,like Figure 14 and 15 As shown, in some embodiments, the negative end cap 410 further includes a liquid injection mechanism 411, and a ninth through hole 443 is provided on the second insulating member 440, the ninth through hole 443 corresponding to the liquid injection mechanism 411.

[0422] A pressure relief mechanism 311 is provided on the positive electrode side, and a liquid injection mechanism 411 is provided on the negative electrode side. Since the electrolyte will corrode the pressure relief mechanism 311, the pressure relief mechanism 311 and the liquid injection mechanism 411 are provided separately, which can reduce the corrosion of the pressure relief mechanism 311 by the electrolyte.

[0423] In the above scheme, by providing a ninth through hole 443 on the second insulating member 440 corresponding to the liquid injection mechanism 411, it can be ensured that the electrolyte is successfully injected into the battery cell 100.

[0424] It should be noted here that, to enhance the tight connection between the electrode terminals and the lower plastic, a sealing ring can be provided on the second part of the electrode terminals. For example, Figure 9 and Figure 14 The sealing ring 110 shown.

[0425] Figure 17 This is a schematic diagram of the negative electrode sheet according to one embodiment of this application. Figure 17 As shown, in some embodiments, the main body 22 includes a negative electrode body 221, and a negative electrode tab 222 extends from the negative electrode body 221 along a first direction X; in the second direction Y, the ratio of the size of the negative electrode tab 222 to the size of the negative electrode body 221 is greater than 50%.

[0426] The electrode assembly 21 includes a main body 22, a positive electrode tab 212, and a negative electrode tab 222. The main body 22 includes a positive electrode body 211 and a negative electrode body 222. That is, the positive electrode body 211 and the positive electrode tab 212 form the positive electrode 210, and the negative electrode body 221 and the negative electrode tab 222 form the negative electrode 220. Specifically, the positive electrode tab 212 extends from the positive electrode body 211, and the negative electrode tab 222 extends from the negative electrode body 221.

[0427] The second direction Y is the width direction of the battery cell. In the second direction Y, the ratio of the size of the negative electrode tab 222 to the size of the negative electrode body 221 is greater than 50%, that is, the width ratio of the negative electrode tab 222 to the width of the negative electrode body 221 is greater than 50%.

[0428] The wider the negative electrode tab 222, the better it is for overcurrent, heat conduction, and reducing the temperature inside the battery cell 100 during charging and reducing the risk of electrolyte decomposition and gas generation. However, the wider the negative electrode tab 222, the larger the space it needs to occupy for the tab, which will affect the energy density of the battery cell 100.

[0429] In the above scheme, by making the ratio of the size of the negative electrode tab 222 to the size of the negative electrode body 221 greater than 50% in the width direction Y of the battery cell, the current flow area at the negative electrode tab 222 can be increased, the impedance and heat generation at the negative electrode tab 222 can be reduced, and the energy density of the battery cell 100 can also be taken into account.

[0430] Specifically, in the second direction Y, the ratio of the size of the negative electrode tab 222 to the size of the negative electrode body 221 can be 50%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, or a value within the range obtained by any combination of the above two values.

[0431] Optionally, in the second direction Y, the ratio of the size of the negative electrode tab 222 to the size of the negative electrode body 221 is 60% to 100%.

[0432] On the same positive side, the battery cell 100 also includes multiple negative electrode plates 220, and the negative electrode tab 222 formed by each negative electrode plate 220 is wound and stored inside the battery cell 100.

[0433] In some implementations, the size of the negative electrode tab can be detected by disassembling the battery cell at 0% SOC to obtain the negative electrode sheet. The negative electrode tab on the negative electrode sheet is divided into two parts: a first negative electrode tab not welded to the negative terminal and a second negative electrode tab welded to the negative terminal. The dimensions of the first and second negative electrode tabs are measured separately, and their sum is calculated as the size of the corresponding negative electrode tab. Additionally, if the first negative electrode tab is curled up, it needs to be unfolded before measuring the corresponding size.

[0434] It should be noted that, unless otherwise specified, the dimensions of the negative electrode tab mentioned in the embodiments of this application include the sum of the dimensions of the first negative electrode tab and the second negative electrode tab.

[0435] Please continue to refer to Figure 16 and17 .like Figure 16 and 17 As shown, in some embodiments, the third portion 421 has a second surface 4211 close to the electrode assembly 21; the negative electrode body portion 221 includes a negative electrode film layer 2211, which is used to coat a negative electrode active material; in the first direction X, the dimension between the edge of the negative electrode film layer 2211 and the second surface 4211 is 7 mm to 10 mm.

[0436] The third part 421 has a surface close to the electrode assembly 21 and a surface away from the electrode assembly 21. The surface of the third part 421 close to the electrode assembly 21 is connected to the negative electrode tab 222, that is, the second surface 4211 of the third part 421 is connected to the negative electrode tab 222.

[0437] The negative electrode tab 222 extends from the negative electrode body 221, is gathered in the second recess 442, and then connects to the second surface 4211 of the third part 421. That is, the dimension between the edge of the negative electrode film layer 2211 and the second surface 4211 is the space of the negative electrode tab.

[0438] In the above scheme, by limiting the size of the negative electrode tab space to 7mm~10mm, the negative electrode tab 222 can be properly placed, while also taking into account the energy density of the battery cell 100.

[0439] Specifically, in the first direction X, the dimension between the edge of the negative electrode film layer 2211 and the second surface 4211 can be 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, or a value within the range obtained by any combination of the above two values.

[0440] In some embodiments, the total area of ​​the second welding region formed by welding the negative electrode tab 222 and the third part 421 is 130 mm². 2 ~200mm 2 .

[0441] The total area of ​​the second welding area can represent the overcurrent area between the negative electrode tab 222 and the negative terminal 420. If the total area of ​​the first welding area is too small, it is not conducive to reducing the electron transmission impedance and reducing the heat generated by the battery cell 100 during the charging process. However, if the total area of ​​the second welding area is too large, it may squeeze other structural components, causing safety hazards inside the battery cell 100.

[0442] In the above scheme, the welding area between the negative electrode tab 222 and the third part 421 is kept at 130mm². 2 ~200mm 2 This ensures both normal current transmission and the safety performance of the individual battery cells.

[0443] It should be noted that the "total area" here refers to the sum of the welding areas of the negative electrode tab 222 and at least two third parts 421. The negative electrode cap assembly 40 includes multiple negative terminals 420. The negative electrode tab 222 is welded to multiple negative terminals 420, that is, the negative electrode tab 222 is welded to at least two third parts 421 respectively, and the sum of the welding areas formed after each welding is within the above-mentioned range. In addition, the welding area of ​​the negative electrode tab 222 and each third part 421 can be the same or different, which can be adjusted according to the production process.

[0444] Specifically, the total area of ​​the second welding region formed by welding the negative electrode tab 222 and the third part 421 can be 130 mm². 2 135mm 2 140mm 2 145mm 2 150mm 2 155mm 2 160mm 2 170mm 2 180mm 2 190mm 2 200mm 2 , or its value is within the range obtained by combining any two of the above values.

[0445] In some embodiments, the positive electrode active material in the positive electrode film 2111 includes lithium transition metal phosphate.

[0446] In some embodiments, the negative electrode active material in the negative electrode film layer 2211 includes graphite.

[0447] In the embodiments of this application, the specific materials in the positive and negative electrode films can be tested using equipment and methods known in the art. For example, the following testing method can be used: after disassembling the battery cell, scrape off the positive electrode film, add the scraped material to aqua regia, and digest it under mechanical stirring for 30 minutes; then add the digested solution to an ICAP7400 spectrometer to analyze the elemental composition. Alternatively, this application can also use JIS / K0131-1996 General Rules for X-ray Diffraction Analysis to perform X-ray powder diffraction testing and qualitative analysis on the specific materials in the positive and negative electrode films.

[0448] In some embodiments, the lithium transition metal phosphate includes at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

[0449] Please continue to refer to Figure 12 .like Figure 12As shown, in some embodiments, in the first direction X, the edge of the negative electrode film layer 2211 extends beyond the edge of the positive electrode film layer 2111; in the second direction Y, the edge of the negative electrode film layer 2211 extends beyond the edge of the positive electrode film layer 2111.

[0450] If the edge of the positive electrode film 2111 directly contacts the electrolyte, lithium ions may not be fully intercalated during charging, leading to the deposition of metallic lithium on the surface of the positive electrode film 2111, forming lithium dendrites. Lithium dendrites grow rapidly and may puncture the separator 230, causing a short circuit and affecting the safety performance of the battery cell 100. By extending the edge of the negative electrode film 2211 beyond the edge of the positive electrode film 2111, the edge of the positive electrode film 2111 can be prevented from directly contacting the electrolyte, reducing the risk of lithium dendrite formation.

[0451] The first direction X and the second direction Y are the length and width directions of the battery cell 100, respectively. In both the first direction X and the second direction Y, the negative electrode film layer 2211 extends beyond the positive electrode film layer 2111.

[0452] In the above scheme, by making the edge of the negative electrode film layer 2211 extend beyond the edge of the positive electrode film layer 2111 in both the first direction X and the second direction Y, the formation of lithium dendrites can be reduced, which is beneficial to further improving the safety performance of the battery cell.

[0453] In some embodiments, in the first direction X, the distance by which the edge of the negative electrode film layer 2211 extends beyond the edge of the positive electrode film layer 2111 is OH1, and in the second direction Y, the distance by which the edge of the negative electrode film layer 2211 extends beyond the edge of the positive electrode film layer 2111 is OH2, where OH1 is 3mm~8mm and OH2 is 1mm~4mm.

[0454] In some implementations, OH1 is greater than OH2.

[0455] In the above scheme, by making OH1 greater than OH2, the proportion of the positive electrode film layer 2111 and the negative electrode film layer 2211 in the casing 20 can be increased, thereby increasing the energy density of the battery cell 100.

[0456] In the above scheme, by keeping OH1 and OH2 within the above range, it is possible to reduce the formation of lithium dendrites and avoid the negative electrode film layer 2211 from being too long, thereby improving the energy density of the battery cell 100.

[0457] Specifically, OH1 can be 3mm, 3.1mm, 3.4mm, 3.5mm, 3.6mm, 4mm, 4.5mm, 5mm, 6mm, 7mm, 8mm, or a value within the range obtained by any combination of the above two values.

[0458] Specifically, OH2 can be 1mm, 1.6mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.6mm, 2.8mm, 3mm, 4mm, or its value can be within the range obtained by any combination of the above two values.

[0459] like Figure 12 As shown, in some embodiments, the projection of the first transition region 2112 in the thickness direction Z of the battery cell covers the projection of the edge of the negative electrode film layer 2211.

[0460] The positive electrode body 211 includes a positive electrode film layer 2111 coated with a positive electrode active material and a first transition region 2112 coated with an insulating material. The first transition region 2112 is disposed between the positive electrode film layer 2111 and the positive electrode tab 212. In the thickness direction Z of the battery cell, the projection of the first transition region 2112 covers the projection of the edge of the negative electrode film layer 2211, so the edge of the negative electrode film layer 2211 falls within the first transition region 2112.

[0461] During the charging process of the battery cell 100, if lithium ions are unevenly embedded on the surface of the negative electrode, lithium dendrites are likely to form at the edge of the negative electrode. The dendrites will gradually grow and may pierce the separator 230. If the edge of the negative electrode film layer 2211 falls into the first transition region 2112, which is an insulating material, even if the lithium dendrites pierce the separator 230, their growth direction will first contact the first transition region 2112, which is an insulating material, rather than the positive electrode active material. Therefore, the first transition region 2112 can not only physically prevent the dendrites from continuing to grow into the positive electrode 210, but also isolate the conductive contact between the dendrites and the positive electrode 210, thus preventing the dendrites from causing a short circuit in the battery cell 100.

[0462] In the above scheme, by making the projection of the first transition region 2112 cover the projection of the edge of the negative electrode film layer 2211 in the thickness direction Z of the battery cell, the risk of short circuit of the battery cell 100 can be further reduced, thereby further improving the safety performance of the battery cell 100.

[0463] In some embodiments, the volume average particle size Dv50 of graphite is 8 μm to 13 μm.

[0464] In this embodiment of the application, "volume average particle size" refers to the particle size corresponding to the cumulative particle size distribution percentage reaching 50% in the particle size distribution diagram of the sample. Its physical meaning is: particles with a diameter greater than this value account for 50% of the total number of particles in the sample, and particles with a diameter less than or equal to this value account for 50% of the total number of particles. Dv50, also known as median particle size, is commonly used to represent the average particle size of a sample.

[0465] When the Dv50 of graphite is small, it can meet the fast charging performance of the battery cell 100. However, if it is too small, the side reaction between graphite and electrolyte will increase, which will damage the SEI film and thus affect the cycle performance of the battery cell 100.

[0466] In the above scheme, by keeping the volume average particle size Dv50 of the negative electrode active material at 8μm~13μm, the fast charging performance and cycle performance of the battery cell 100 can be balanced.

[0467] Specifically, the volume average particle size Dv50 of the negative electrode active material can be 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, or 13μm, or a value within the range obtained by any combination of the above two values.

[0468] In the embodiments of this application, the volume average particle size of the negative electrode active material can be detected using equipment and methods known in the art. For example, a battery cell is discharged at a constant current of 0.05C to 2V to obtain a battery cell with 0% SOC. The negative electrode is then removed from the battery cell, and the film layer on the electrode is scraped off. The obtained film powder is mixed with water, stirred, filtered, and dried to obtain a negative electrode active material sample. According to the testing standard GB / T 19077-2016, the particle size is measured using a Mastersizer2000E laser particle size analyzer. The particle size at 50% of the volume distribution is calculated from smallest to largest on the volume particle size distribution curve; this is Dv50.

[0469] Figure 18 This is a schematic diagram of the negative electrode sheet according to another embodiment of this application. Figure 18 As shown, in some embodiments, the negative electrode film layer 2211 includes a first film layer 22111 and a second film layer 22112, with the first film layer 22111 located between the negative electrode current collector 2213 and the second film layer 22112; the graphite in the first film layer 22111 includes artificial graphite or a mixture of artificial graphite and natural graphite, and the average particle size of the longest diameter of the graphite is 7μm to 18μm; the graphite in the second film layer 22112 includes artificial graphite or a mixture of artificial graphite and natural graphite, and the average particle size of the longest diameter of the graphite is 6μm to 10μm.

[0470] In embodiments of this application, the longest diameter of the material may refer to the longest straight line that passes through the center point of the particle and extends to the outer periphery of the particle.

[0471] By configuring the negative electrode film layer 2211 into a double-layer structure, and using large-diameter graphite particles in the first film layer 22111 near the current collector, the high energy density of the battery cell 100 can be guaranteed to a certain extent. Furthermore, using small-diameter graphite particles in the second film layer 22112 near the electrolyte improves its contact with the electrolyte, resulting in better wettability of the graphite by the electrolyte. The small-diameter particles in the second film layer 22112 also result in larger porosity, which is beneficial for improving the fast-charging performance of the battery cell 100. In other words, the double-layer configuration of the negative electrode film layer 2211 with different particle sizes can balance the high energy density and fast-charging performance of the battery cell 100.

[0472] In the embodiments of this application, artificial graphite and natural graphite can be detected using equipment and methods known in the art. For example, they can be distinguished by SEM cross-sectional images taken by a scanning electron microscope (SEM). Natural graphite has gaps between its sheet-like structures in its SEM cross-sectional image, while artificial graphite is dense and has no obvious gaps in its SEM cross-sectional image. Alternatively, they can be distinguished by XRD patterns obtained by X-ray diffraction. Natural graphite has obvious 2H and 3R phases in its XRD pattern, while artificial graphite only has the 2H phase in its XRD pattern.

[0473] In embodiments of this application, the average particle size of the longest diameter of the material can be detected using equipment and methods known in the art. For example, it can be measured by taking 30 graphite-containing particles from a longitudinal section of the first or second film layer, measuring the longest diameter of each of the 30 particles, and then averaging the values ​​to obtain the average particle size of the longest diameter of the graphite in the first or second film layer.

[0474] Figure 19 This is a schematic diagram of the negative electrode sheet according to another embodiment of this application. Figure 19 As shown, in some embodiments, a first functional layer 2214 is disposed between the negative electrode current collector 2213 and the negative electrode film layer 2211. The first functional layer 2214 includes an adhesive and a conductive agent. The thickness of the first functional layer 2214 is 0.2 μm to 3 μm. The adhesive includes at least one of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan. The conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0475] When the battery cell 100 is a fast-charging battery system, the negative electrode 220 is more prone to expansion. Therefore, by providing a first functional layer 2214 between the negative electrode current collector 2213 and the negative electrode film layer 2211, the adhesion between the negative electrode film layer 2211 and the negative electrode current collector 2213 can be increased to prevent the negative electrode film layer 2211 from demolding; and, providing the first functional layer 2214 can improve the conductivity of the negative electrode 220, reduce the heat generation of the negative electrode 220 and the heat generation of the battery cell 100, so as to balance the fast-charging performance and reliability of the battery cell 100.

[0476] It should be noted that the 0.2μm~3μm range here refers to the thickness range of the first functional layer 2214 on one side. When the thickness of the first functional layer 2214 is within the above range, its space occupation is relatively small, which is beneficial to improving the space occupied by the negative electrode active material.

[0477] In the above scheme, by setting a first functional layer 2214 between the negative electrode current collector 2213 and the negative electrode film layer 2211, the bonding force between the negative electrode film layer 2211 and the negative electrode current collector 2213 can be increased to prevent the negative electrode film layer 2211 from demolding, thereby improving the reliability of the battery cell 100; at the same time, the conductivity of the negative electrode sheet 220 can be improved, the heat generation of the negative electrode sheet 220 and the heat generation of the battery cell 100 can be reduced, thereby meeting the fast charging performance of the battery cell 100.

[0478] Specifically, the thickness of the first functional layer 2214 can be 0.2μm, 0.5μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.6μm, 2μm, 2.3μm, 2.5μm, 2.7μm, 3μm, or a value within the range obtained by any combination of the above two values.

[0479] In the embodiments of this application, the thickness of the first functional layer 2214 has a meaning known in the art and can be detected using equipment and methods known in the art. For example, a tomographic scan of the negative electrode 220 can be performed to directly measure the thickness of the first functional layer 2214.

[0480] In some embodiments, the porosity of the negative electrode 220 corresponding to the battery cell 100 at 0% SOC is 25% to 40%.

[0481] The essence of fast charging is to allow a large number of lithium ions to be extracted from the positive electrode in a short period of time and quickly embedded into the negative electrode 220. The lithium ions migrate within the porosity through the electrolyte, and the porosity of the negative electrode 220 directly determines the amount of electrolyte filling and the migration path of lithium ions.

[0482] When the porosity is too low, there are few voids inside the negative electrode 220, and the electrolyte cannot be fully filled, resulting in a narrower and longer migration channel for lithium ions. At the same time, the electrolyte layer between the negative electrode active material particles becomes thinner, increasing the distance that lithium ions have to travel from the electrolyte to the surface of the negative electrode active material particles, and causing a sharp increase in transmission resistance. When the porosity is too high, the excessive porosity will reduce the density of the negative electrode 220, causing the electron conduction path in the negative electrode 220 to become longer, and reducing the electron transport efficiency.

[0483] In the above scheme, by controlling the porosity of the negative electrode 220 to 25%~40%, the dynamics of the negative electrode 220 can be improved, thereby improving the fast charging performance of the battery cell 100.

[0484] Specifically, the porosity of the negative electrode 220 can be 25%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, or a value within the range obtained by any combination of the above two values.

[0485] In the embodiments of this application, porosity refers to the ratio of the volume of pores to the apparent volume (or total volume) of the porous material. In the embodiments of this application, porosity can be detected using equipment and methods known in the art. For example, it can be tested using gas permeation, water repulsion, or gas adsorption methods.

[0486] In some embodiments, the graphite in the negative electrode film has an average particle size of 7 μm to 15 μm, and the graphite in the negative electrode film includes secondary particles.

[0487] Secondary particles refer to particle aggregates formed by the agglomeration of primary particles.

[0488] For example, the average particle size of the graphite in the negative electrode film can be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm, or a value within the range obtained by any combination of the above two values.

[0489] In some implementations, the graphitization degree of the graphite in the negative electrode film is 90% to 94%.

[0490] In some embodiments, when the battery cell 100 is at 0% SOC, the compaction density of the positive electrode 210 is 2.3 g / cm³. 3 ~2.65g / cm 3 .

[0491] In some embodiments, the compaction density of the negative electrode 220 is 1.3 g / cm³. 3 ~1.52g / cm 3 .

[0492] Compacted density refers to the mass of active material per unit volume after the electrode has been rolled, and its essence is the degree of compactness of the electrode. The higher the compacted density, the denser the electrode, and vice versa. In the embodiments of this application, unless otherwise specified, the compacted density of the positive electrode 210 and the negative electrode 220 refers to the compacted density at 3T.

[0493] For the negative electrode 220, if its compaction density is too high, the pores inside the electrode will be excessively squeezed and become smaller or even closed, resulting in a decrease in electrolyte wettability, lithium ions will lose the transport medium, and the ion transport resistance will increase; if its compaction density is too low, it will affect the energy density and the structural strength of the electrode.

[0494] For the positive electrode 210, if its compaction density is too high, it will affect the extraction of lithium ions from the positive electrode active material lattice and make it difficult for them to diffuse quickly into the electrolyte; if its compaction density is too low, it will also affect the energy density and electron conduction efficiency.

[0495] In the above scheme, by keeping the compaction density of the positive electrode 210 and the negative electrode 220 within the above range, the fast charging performance and energy density of the battery cell 100 can be balanced.

[0496] Specifically, when the cell is at 0% SOC, the compaction density of the positive electrode 210 can be 2.3 g / cm³. 3 2.35g / cm 3 2.4g / cm 3 2.45g / cm 3 2.5g / cm 3 2.55g / cm 3 2.6g / cm 3 2.65g / cm 3 , or its value is within the range obtained by combining any two of the above values.

[0497] Specifically, the compaction density of the negative electrode 220 can be 1.3 g / cm³. 3 1.32g / cm 3 1.35g / cm 3 1.38g / cm 3 1.4g / cm 3 1.44 g / cm 3 1.45g / cm 3 1.5g / cm 3 1.52 / cm 3 , or its value is within the range obtained by combining any two of the above values.

[0498] In the embodiments of this application, the compaction density of the negative electrode sheet can be detected using equipment and methods known in the art. For example, a battery cell under test at 0% SOC is disassembled to obtain the negative electrode sheet. Thirty unit areas are randomly selected from the negative electrode sheet under test. The mass m1 of the material (excluding the negative current collector) on each unit area of ​​the negative electrode sheet is weighed. The thickness H1 of the negative electrode sheet and the thickness H0 of the current collector are measured. The compaction density of each unit area of ​​the negative electrode sheet is calculated as m1 / (H1-H0). The compaction densities of the 30 unit areas of the negative electrode sheet are summed and then divided by 30 to obtain the compaction density of the negative electrode sheet under test. The measurement deviation of the compaction density is within ±0.05 g / cm³. 3 Within the range. The same applies to the positive electrode 210.

[0499] Optionally, when the cell is at 0% SOC, the compaction density of the positive electrode 210 is 2.45 g / cm³. 3 ~2.6g / cm 3 .

[0500] Optionally, when the cell is at 0% SOC, the compaction density of the negative electrode 220 is 1.3 g / cm³. 3 ~1.5g / cm 3 .

[0501] In some embodiments, such as Figure 3 As shown, the battery cell 100 also includes a separator 230.

[0502] In some embodiments, the positive electrode 210, the separator 230, and the negative electrode 220 are stacked in the thickness direction Z of the battery cell; the separator 230 includes a base film and a second functional layer disposed on at least one side of the base film, the second functional layer including inorganic particles.

[0503] In some embodiments, the inorganic particles include one or more of silicon oxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide; and / or the average particle size of the inorganic particles is 5 nm to 100 nm.

[0504] In the above scheme, by providing a second functional layer including inorganic particles on the base film of the separator 230, the heat resistance of the second functional layer can be improved, thereby enhancing the reliability of the battery cell 100. Furthermore, by ensuring that the average particle size of the inorganic particles is within the above range, it is beneficial to improve the heat resistance and compressive modulus of the separator 230, which is beneficial to further improving the reliability of the battery cell 100.

[0505] Specifically, the average particle size of the inorganic particles can be 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, or 100nm, or a value within the range obtained by any combination of the above two values.

[0506] In the embodiments of this application, the average particle size of inorganic particles has a meaning known in the art and can be detected using equipment and methods known in the art. For example, after obtaining the separator membrane and drying it as a sample, the separator membrane is cut with an ion beam cutter to form a cross-section. Subsequently, the particle size of inorganic particles in the separator membrane is measured using a scanning electron microscope. The particle size of multiple inorganic particles, such as 50, is measured, and their average value is calculated as the average particle size.

[0507] In some embodiments, the second functional layer may further include an adhesive, which includes one or more of fluorinated adhesives or polyacrylic adhesives. Specifically, the fluorinated adhesive includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and tetrafluoroethylene-hexafluoropropylene copolymer. The polyacrylic adhesive includes one or more of polyacrylic acid and fluorinated acrylate resins.

[0508] In some embodiments, the separator 230 further includes a third functional layer located on the side of the second functional layer away from the base membrane.

[0509] Specifically, the separator 230 includes a second functional layer and a third functional layer. The second functional layer is located on both sides of the base membrane, and the third functional layer is located on one side of the base membrane, specifically on the side of the second functional layer furthest from the base membrane. In this case, the third functional layer can be positioned close to the negative electrode 220.

[0510] In some embodiments, the fluorinated binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, a terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, and a terpolymer of tetrafluoroethylene-hexafluoropropylene.

[0511] In the above solution, by setting a third functional layer including a fluorinated binder, short circuits between the positive and negative electrodes can be prevented, thereby improving the reliability of the battery cell 100.

[0512] In some embodiments, the thickness of the base film is 5 μm to 9 μm.

[0513] In some implementations, the thickness of the second functional layer is 0.5 μm to 1.5 μm.

[0514] In some implementations, the thickness of the third functional layer is 1 μm to 2.5 μm.

[0515] In some embodiments, the thickness of the separator 230 is 9 μm to 12 μm.

[0516] In the above scheme, by keeping the thickness of each layer of the separator 230 within the above range, it is beneficial to improve the reliability of the battery cell 100.

[0517] Specifically, the thickness of the base film can be 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, or a value within the range obtained by any combination of the above two values.

[0518] Specifically, the thickness of the second functional layer can be 0.5μm, 0.6μm, 0.8μm, 1μm, 1.1μm, 1.2μm, 1.4μm, 1.5μm, or a value within the range obtained by any combination of the above two values.

[0519] Specifically, the thickness of the third functional layer can be 1μm, 1.2μm, 1.4μm, 1.5μm, 1.6μm, 1.8μm, 2μm, 2.1μm, 2.3μm, 2.5μm, or a value within the range obtained by any combination of the above two values.

[0520] In the embodiments of this application, the thickness of the membrane layer has a meaning known in the art. It can be detected using a meaning and equipment known in the art. For example, a newly prepared separator can be taken as a sample, or a battery cell that has been completely discharged (discharged to the discharge cutoff voltage so that the charge state of the battery cell is about 0% SOC) can be disassembled in reverse, the separator can be obtained from the battery cell, and the separator can be dried and used as a sample. The separator can be cut with an ion beam cutter to form a cross section. Subsequently, the thickness of the separator and its various layers can be measured using a scanning electron microscope.

[0521] In some embodiments, the thickness of the housing 20 is less than 0.5 mm.

[0522] For example, the thickness of the housing 20 can be 0.4 mm, 0.38 mm, 0.35 mm, 0.32 mm, 0.3 mm, 0.28 mm, or a value within the range obtained by any combination of the above two values.

[0523] Optionally, the thickness of the housing 20 is 0.3mm to 0.4mm.

[0524] Setting the thickness of the housing 20 within the aforementioned range can both protect the electrode assembly 21 and prevent the energy density of the battery cell 100 from being affected by excessive thickness.

[0525] In some embodiments, the casing 20 is made of a metallic material, including aluminum or steel. This provides the casing 20 with good structural strength and a lighter weight, reducing the overall weight of the battery cell 100.

[0526] In some implementations, refer to Figure 1-2 The housing 20 includes a first sidewall 20a and a second sidewall 20b extending in a first direction X. The first sidewall 20a is the wall with the largest surface area of ​​the housing 20. The housing 20 includes a weld (not shown in the figure), which is located on the second sidewall 20b and extends in the first direction X.

[0527] The weld of the casing 20 is located on the side wall with a small surface area. In this way, when thermal runaway occurs in the battery cell 100, the high-temperature expansion force at the weld is small, and the overall stress of the casing 20 of the battery cell 100 is more uniform. The casing 20 is less likely to crack at the weld, thus reducing the risk of thermal runaway propagation of the battery cell 100.

[0528] Figure 20 This is a partial structural diagram of a battery cell according to another embodiment of this application.

[0529] In some embodiments, refer to Figure 20 The battery cell 100 also includes a side support plate 51, which is disposed between the housing 20 and the electrode assembly 21. The side support plate 51 extends along the first direction X and is disposed opposite to the second side surface 22b.

[0530] A side support plate 51 is provided between the electrode assembly 21 and the housing 20. On the one hand, it serves to insulate the electrode assembly 21 and the housing 20, and on the other hand, it can improve the structural stability of the battery cell 100.

[0531] In some embodiments, when the battery cell is charged at a 1 / 3C rate, the volumetric energy density of the battery cell is 440Wh / L to 460Wh / L.

[0532] For example, the volumetric energy density of a single battery cell can be 440Wh / L, 445Wh / L, 450Wh / L, 455Wh / L, 457Wh / L, 460Wh / L, or a value within the range obtained by any combination of the above two values.

[0533] In some embodiments, when the battery cell is charged at a 1 / 3C rate, the gravimetric energy density of the battery cell is 190Wh / kg to 200Wh / kg.

[0534] For example, the mass energy density of a single battery cell can be 190Wh / kg, 192Wh / kg, 194Wh / kg, 195Wh / kg, 197Wh / kg, 200Wh / kg, or a value within the range obtained by any combination of the above two values.

[0535] In the embodiments of this application, the meaning of energy density is known in the art. It can be detected using known meanings and equipment in the art. For example, at room temperature (25℃±2℃), the battery is discharged to the lower limit voltage in the form of constant current discharge (1 / 3C rate), left to stand for 30 minutes, and then charged to the upper limit cutoff voltage in the form of constant current and constant voltage charging (constant current 1 / 3C, constant voltage charging to 1 / 20C), left to stand for 30 minutes, and the discharge energy E (in Wh) is recorded. This is repeated 3 times, and the average value of the 3 discharge energies E is recorded as E0. Dividing this value by the volume V of the battery cell, the volumetric energy density (in Wh / L) is E0 / V; or dividing this value by the mass m of the battery cell, the mass energy density (in Wh / kg) is E0 / m.

[0536] In some embodiments, the battery cell 100 further includes an electrolyte contained in a accommodating space 201. The electrolyte includes an organic solvent, including dimethyl carbonate and linear carboxylic acid esters. The total mass content of dimethyl carbonate and linear carboxylic acid esters is 10% to 60% based on the total mass of the electrolyte.

[0537] Linear carboxylic acid ester solvents have low viscosity and good flowability, resulting in low resistance to lithium ion migration and enabling high ionic conductivity for fast charging of the battery cell 100. Therefore, if the mass content of carboxylic acid ester solvents in the electrolyte is too low, a high ion migration rate cannot be achieved, which is detrimental to fast charging of the battery cell 100. However, if the mass content of carboxylic acid ester solvents is too high, interfacial side reactions may occur on the negative electrode side, increasing the risk of gas generation in the battery cell 100 at high temperatures, thus increasing the risk of battery cell 100 expansion and compromising its safety performance.

[0538] In this embodiment, the electrode assembly 21 has a large surface area, which is beneficial for heat dissipation of the battery cell 100. Based on this, a higher content of linear carboxylic acid ester solvent can be used in the electrolyte to improve the conductivity of the electrolyte, thereby improving the dynamic performance of the battery and the fast charging performance of the battery cell 100.

[0539] Specifically, based on the mass content of the electrolyte, the mass content of dimethyl carbonate and linear carboxylic acid ester can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or values ​​within the range obtained by any combination of the above two values.

[0540] In the embodiments of this application, the types and contents of inorganic components or lithium salts in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the inorganic components / electrolyte lithium salts in the electrolyte can be qualitatively or quantitatively analyzed by referring to standards JY / T 0575-2020 "General Rules for Ion Chromatography Analysis" and GB / T 6040-2019 "General Rules for Infrared Spectroscopy Analysis". In the embodiments of this application, freshly prepared electrolyte can be used as a sample, the free electrolyte of a fresh battery can be used as a sample, or a fully discharged battery cell (discharged to the discharge cutoff voltage so that the charge state of the battery cell is about 0% SOC) can be disassembled in reverse, and the free electrolyte obtained from the battery cell can be used as a sample for detection.

[0541] In the embodiments of this application, the types and contents of organic components in the electrolyte are known in the art and can be detected using equipment and methods known in the art. For example, the organic components of the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography using GB / T 9722-2023 "General Rules for Gas Chromatography of Chemical Reagents".

[0542] Optionally, based on the total mass of the electrolyte, the sum of the mass contents of dimethyl carbonate and linear carboxylic acid ester is 40% to 60%.

[0543] In some embodiments, the linear carboxylic acid ester comprises a compound represented by formula (I).

[0544] Formula (I)

[0545] R1 and R2 each independently include alkyl or haloalkyl groups having 1 to 5 carbon atoms.

[0546] In the above scheme, by making the linear carboxylic acid ester solvent meet the above chemical formula requirements, it is beneficial to the migration of lithium ions to improve the fast charging capability of the battery cell 100.

[0547] Optionally, R1 comprises an alkyl or haloalkyl group having 1 to 3 carbon atoms. More optionally, R1 comprises a hydrogen atom, an alkyl or haloalkyl group having 1 to 2 carbon atoms.

[0548] Optionally, R2 comprises an alkyl or haloalkyl group having 1 to 3 carbon atoms. More preferably, R2 comprises an alkyl or haloalkyl group having 1 to 2 carbon atoms.

[0549] In some embodiments, the halogenated alkyl group includes one or more of fluoroalkyl, chloroalkyl, bromoalkyl, and iodoalkyl groups; optionally, the halogenated alkyl group includes fluoroalkyl.

[0550] In some embodiments, the linear carboxylic acid ester includes at least one of methyl acetate, ethyl acetate, ethyl propionate, and methyl butyrate.

[0551] In some embodiments, the linear carboxylic acid ester includes at least one of methyl acetate and ethyl acetate.

[0552] In some embodiments, the electrolyte includes a lithium salt, and the lithium salt content is 12% to 21% based on the total mass of the electrolyte.

[0553] The lithium salt content in the electrolyte determines the concentration and migration ability of lithium ions. If the lithium salt content is too low, the concentration of free lithium ions in the electrolyte will be insufficient, and the lithium ion transport rate will not be able to match the high current demand during fast charging. This will lead to a lithium ion transport bottleneck, manifested as a rapid increase in voltage during charging, but the actual capacity cannot be charged, or lithium dendrites will precipitate on the negative electrode due to insufficient lithium ion supply. If the lithium salt content is too high, it will increase the viscosity of the electrolyte, which will reduce the migration rate of lithium ions.

[0554] In the above scheme, by making the mass content of lithium salt in the electrolyte 12%~21%, it is beneficial to further improve the fast charging performance of the battery cell 100.

[0555] Specifically, based on the total mass of the electrolyte, the mass content of lithium salt can be 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, or a value within the range obtained by any combination of the above two values.

[0556] In some embodiments, the lithium salt includes lithium fluorosulfonylimide and lithium hexafluorophosphate; in the electrolyte, the mass ratio of lithium hexafluorophosphate to lithium fluorosulfonylimide is 0.8 to 3.5.

[0557] Lithium hexafluorophosphate (LiPF6) has advantages such as good solubility, high ion conductivity, and high ion dissociation, but its poor thermal stability and tendency to hydrolyze into hydrogen fluoride lead to rapid capacity decay in batteries. Lithium fluorosulfonylimide (LiPF6) offers higher thermal stability, ion conductivity, lithium-ion transference number, and superior low-temperature performance, but it is more expensive. Therefore, adding both as lithium salts to the electrolyte can further improve the performance of individual battery cells.

[0558] By combining lithium fluorosulfonylimide and lithium hexafluorophosphate, the conductivity of the electrolyte is improved while the generation of hydrofluoric acid is reduced, and the side reactions of the electrolyte are reduced, thus balancing the fast charging performance and cycle life of the battery cell.

[0559] Specifically, the mass ratio of lithium hexafluorophosphate to lithium fluorosulfonyl imide can be 0.8, 1, 1.2, 1.5, 2, 2.5, 2.8, 3, 3.5, or a ratio within the range obtained by any combination of the above two ratios.

[0560] In some embodiments, lithium fluorosulfonylimide includes at least one of lithium bisfluorosulfonylimide and lithium bistrifluoromethanesulfonate imide.

[0561] Both of the above-mentioned lithium fluorosulfonylimide compounds can effectively improve the conductivity of the electrolyte, and have good thermal and electrochemical stability, which can reduce the occurrence of electrolyte side reactions.

[0562] In some embodiments, the electrolyte further includes additives, including at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate.

[0563] The mass content of the additive is 0.1% to 5% based on the total mass of the electrolyte.

[0564] The above-mentioned additives can participate in the formation of SEI film on the negative electrode side; however, if the mass content of the above-mentioned additives is too low, the effect of assisting film formation on the negative electrode side is poor, and it cannot play a good protective role for the negative electrode active material. This may still cause side reactions between the negative electrode active material and the carboxylic acid ester solvent, resulting in an increase in the internal pressure of the battery cell 100, which is not conducive to the reliability of the battery cell 100.

[0565] However, as the mass content of the above-mentioned additives increases, although they can form a dense solid electrolyte interface (SEI) film on the negative electrode side, effectively reducing the risk of side reactions between the negative electrode active material and the carboxylic acid ester solvent, the impedance of the SEI film formed is too high, increasing the internal resistance of the battery cell 100, which is not conducive to the fast charging of the battery cell 100.

[0566] In the above scheme, by keeping the mass content of the additive within the above range, it can optimize the composition of the solid electrolyte interphase (SEI) film on the negative electrode side, alleviate the volume expansion and interfacial side reactions of the negative electrode active material such as silicon-based material, reduce the amount of gas generated at high temperature, and ensure that the impedance of the SEI film is not too high and the internal resistance of the battery cell 100 is small, thus achieving a balance between improving the fast charging capability and reliability of the battery cell 100.

[0567] Specifically, based on the total mass of the electrolyte, the mass content of the additive can be 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.6%, 2%, 2.5%, 3%, 4%, 5%, or its value can be within the range obtained by any combination of the above two values.

[0568] Adding certain substances, such as additives, to the electrolyte can have a significant impact. Because these additives participate in the film formation on the surface of active materials, their content in the electrolyte of a single battery cell varies depending on the formation process, the battery's lifespan, and its storage condition. Therefore, the additive content in freshly prepared electrolyte may differ from that in electrolyte obtained from reverse-engineered batteries. However, those skilled in the art can determine the approximate range of the relevant substances' content in the fresh electrolyte based on the battery cell's performance characteristics (e.g., cycle count) and residual content. Similarly, those skilled in the art can determine the approximate range of the additive content in non-freshly prepared (i.e., reverse-engineered) electrolytes based on the additive content in freshly prepared electrolytes, considering the battery cell's performance requirements and storage environment.

[0569] Therefore, the additive content mentioned in the technical solution of this application can be the content of additives actively added to fresh electrolyte, or the content of residual additives detected by reverse detection based on the actual battery state.

[0570] For example, the mass content of additives in the electrolyte is 1% to 3%, which can be understood as the additive content of freshly prepared electrolyte. When the mass content of additives is within the above range, it can more effectively balance the reliability of battery cell 100 and fast charging performance.

[0571] For example, the mass content of the additive in the electrolyte is 0.05% to 2%, which can be understood as obtaining the content of unsaturated ester additives in the electrolyte of the battery cell 100 after formation. When the mass content of the unsaturated ester additives is within the above range, the reliability of the battery cell 100 and the fast charging performance can be more effectively balanced.

[0572] As the cycle and storage time of the battery cell 100 increases, the unsaturated ester additives are continuously consumed, and their mass content shows a downward trend. In some embodiments, the mass content of unsaturated ester additives changes at different life cycles of the battery cell 100 as follows:

[0573] In fresh electrolyte, if the mass content of the additive is 1%;

[0574] Within 3 months of storage in the lower compartment of the battery cell, the mass content of the additive is approximately 0.26%.

[0575] Within 3 to 6 months of storage in the lower compartment of the battery cell, the mass content of the additive is approximately 0.12%.

[0576] During the storage of individual battery cells in the lower compartment for 6 to 12 months, the mass content of the additive is approximately 0.05%.

[0577] In fresh electrolyte, if the mass content of the additive is 2%;

[0578] Within 3 months of storage in the lower compartment of the battery cell, the mass content of the additive is approximately 0.83%.

[0579] Within 3 to 6 months of storage in the lower compartment of the battery cell, the mass content of the additive is approximately 0.60%.

[0580] When battery cells are stored in the lower storage compartment for 6 to 12 months, the mass content of the additive is approximately 0.42%.

[0581] In fresh electrolyte, if the mass content of the additive is 3%;

[0582] Within 3 months of storage in the lower compartment of the battery cell, the mass content of the additive is approximately 1.56%.

[0583] Within 3 to 6 months of storage in the lower compartment of the battery cell, the mass content of the additive is approximately 1.28%.

[0584] When battery cells are stored in the lower storage compartment for 6 to 12 months, the mass content of the additive is approximately 1.03%.

[0585] In some embodiments, the conductivity of the electrolyte is 13 ms / cm to 20 ms / cm.

[0586] In the above scheme, by making the conductivity of the electrolyte 13ms / cm~20ms / cm, it helps to further improve the performance of the battery cell 100.

[0587] Specifically, the conductivity of the electrolyte can be 13ms / cm, 14ms / cm, 15ms / cm, 16ms / cm, 17ms / cm, 18ms / cm, 19ms / cm, 20ms / cm, or a value within the range obtained by any combination of the above two values.

[0588] Specifically, the conductivity of an electrolyte can be tested using the following methods: Equipment and methods known in the art can be employed. A commonly used standard solution is potassium chloride solution, whose conductivity has accurate known values ​​at different temperatures and concentrations. The electrolyte to be tested should be thoroughly stirred to ensure uniform composition and concentration. Record the measured conductivity value, measurement temperature, electrolyte composition and concentration, and other relevant information.

[0589] In some embodiments, the surface of the housing 10 facing away from the electrode assembly 21 has a first insulating film with a thickness of 0.05 mm to 0.2 mm; the material of the first insulating film includes at least one of polyethylene terephthalate, polypropylene, and polyimide.

[0590] In the above solution, by providing an insulating film on the surface of the housing 10, the insulation and wear resistance of the housing 10 can be improved.

[0591] Specifically, the thickness of the first insulating film can be 0.05mm, 0.08mm, 0.1mm, 0.12mm, 0.14mm, 0.15mm, 0.18mm, 2mm, 0.2mm, or a value within the range obtained by any combination of the above two values.

[0592] In some embodiments, the first insulating film has openings.

[0593] In some embodiments, a second insulating film is provided between the main body 22 and the housing 20, the second insulating film being used to insulate the main body 22 and the housing 20; the second insulating film includes at least one of polypropylene and polyethylene terephthalate.

[0594] In the above solution, by covering the outer surface of the electrode assembly 21 with an insulating film, the electrical connection between the housing 20 and the electrode assembly 21 can be isolated, thereby reducing the short-circuit risk of the battery cell 100.

[0595] [Positive electrode plate]

[0596] As described above, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0597] In some embodiments, the lithium phosphate content, based on the total mass of the positive electrode film, is 96.8% to 97.8%, for example 96.8%, 97%, 97.5%, 97.8%, or a value within the range obtained by any combination of the above two values.

[0598] In this application embodiment, the mass content of the positive electrode active material has a meaning known in the art and can be detected using equipment and methods known in the art. For example, after discharging the battery cell to 0% state of charge (SOC), the positive electrode sheet is disassembled (if it is a double-sided coated electrode sheet, the positive electrode active material layer on one side can be wiped off first), and the mass content of the positive electrode active material in the positive electrode active material layer is calculated according to the following steps:

[0599] Step 1: Weigh the container and filter membrane together to get the total weight m0;

[0600] Step 2: Mix n positive electrode sheets with a total mass of m2 in a container with 25% concentrated hydrochloric acid. The mass ratio of the positive electrode sheets to the concentrated hydrochloric acid is 1:8. Then, place the container on a heating plate and perform a single heating digestion at 180°C for 20 minutes to obtain a single digestion solution with a volume of approximately 2.5 mL. Filter the single digestion solution using a filter membrane under vacuum and rinse the filter residue with 200 mL of water to obtain the rinsed filter residue. Weigh the single positive electrode current collector with the positive active material layer removed as m1.

[0601] Step 3: Mix the filter residue after rinsing in Step 2 with 36% concentrated hydrochloric acid in a container. The mass ratio of filter residue to concentrated hydrochloric acid is 1:5. Then place the container on a heating plate and perform secondary heating and digestion at 230°C for 10 minutes to obtain a secondary digestion solution with a volume of about 5 mL.

[0602] Step 4: Filter the secondary digestion solution using the filter membrane from Step 2, and rinse the filter residue with 200 mL of water;

[0603] Step 5: Repeat steps 3 and 4 until the filtrate is a colorless and transparent solution, and obtain the product residue. Bake the product residue at 90°C for 10 hours, and then dry it in a desiccator for 1 hour.

[0604] Step Six: Weigh the container, product filter residue, and filter membrane to obtain the total weight m3. Based on the obtained m0, m1, m2, and m3, calculate the content Wt of the positive electrode active material in the positive electrode sheet according to the formula:

[0605] .

[0606] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0607] In some embodiments, the positive current collector can be a metal foil or a composite current collector. For example, aluminum foil can 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 can 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.).

[0608] In some embodiments, the thickness of the positive electrode current collector is 10 μm to 13 μm. For example, the thickness of the positive electrode current collector is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, or any combination of two of the above values. When the thickness of the positive electrode current collector is within the above range, the thickness of the positive electrode current collector is relatively thin, which is beneficial to increasing the space occupied by the positive electrode active material layer, thereby increasing the volumetric energy density of the battery cell.

[0609] In the embodiments of this application, the thickness of the positive current collector has a meaning known in the art and can be detected using equipment and methods known in the art, such as performing a tomographic scan on the positive electrode sheet to directly measure the thickness of the positive current collector.

[0610] In some embodiments, the positive electrode active material may further include positive electrode active materials known in the art for use in batteries. As an example, the positive electrode active material may include 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 LiNiO2). 1 / 3 Co 1 / 3Mn 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 0.15 Al 0.05 At least one of O2 and its modified compounds.

[0611] It should be understood that, for the aforementioned positive electrode active materials, lithium-ion secondary batteries experience Li intercalation / deintercalation and consumption during charging and discharging. Therefore, the molar content of Li in the positive electrode active material varies depending on the discharge state of the lithium-ion secondary battery. 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, in the examples of positive electrode active materials in this application, the molar content of O is only an ideal value. Lattice oxygen release causes changes in the molar content of O, and the actual molar content of O will fluctuate.

[0612] 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), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0613] In some embodiments, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may also include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, graphene, and carbon nanofibers.

[0614] In some embodiments, the positive electrode sheet can be prepared by forming a positive electrode slurry from the components described above. For example, the positive electrode active material, conductive agent, binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained.

[0615] [Negative electrode plate]

[0616] A negative electrode typically includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material.

[0617] In some embodiments, the mass content of the negative electrode active material in the negative electrode active material layer can be from 96.5% to 98.5%, for example 96.5%, 97%, 97.5%, 98%, 98.5%, or a value within the range obtained by any combination of the above two values.

[0618] When the mass content of the negative electrode active material in the negative electrode active material layer meets the above range, the capacity of the negative electrode active material layer can be increased, thereby improving the energy density of the battery cell.

[0619] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0620] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0621] In some embodiments, in addition to the negative electrode active materials mentioned in the foregoing embodiments, negative electrode active materials known in the art for use in batteries may also be used. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials 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.

[0622] In the embodiments of this application, the graphite particles can be prepared using methods known in the art. Taking artificial graphite as an example, the preparation method includes: providing artificial graphite and an organic carbon source, mixing the two, and then carbonizing them to form a negative electrode coating layer on at least a portion of the surface of the artificial graphite particles.

[0623] In some embodiments, the negative electrode film layer further includes a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0624] In some embodiments, the negative electrode film layer further includes 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.

[0625] In some embodiments, 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., N-methylpyrrolidone) to form a 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.

[0626] Electrolyte

[0627] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte includes electrolyte salts and solvents.

[0628] In one embodiment, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0629] In one embodiment, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0630] In one embodiment, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0631] [Isolation membrane]

[0632] This application does not impose any particular restrictions on the type of separator membrane. For example, any well-known porous separator membrane with good chemical and mechanical stability can be selected.

[0633] In some embodiments, the base film includes one or more of glass fiber, nonwoven fabric, and polyolefin. The base film can be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0634] In some embodiments, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0635] In some embodiments, the porosity of the separator is 20% to 70%, optionally 35% to 60%. Exemplarily, the porosity of the separator is 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any range of two of the above values.

[0636] In this embodiment, porosity refers to the percentage of the pore volume of the separator to the total volume of the separator. Porosity can be tested according to standard GB / T 36363-2018 Polyolefin separators for battery cells. It should be noted that the actual testing process may differ slightly from the standard due to differences in testing instruments, testing errors, and to minimize the impact on porosity testing, in order to obtain more accurate test values.

[0637] In some embodiments, the separator may include a coating. The coating includes heat-resistant particles. The heat-resistant particles may include at least one of inorganic particles and organic particles.

[0638] In some embodiments, inorganic particles may include one or more of the following: inorganic particles having a dielectric constant of 5 or greater, inorganic particles having ion conductivity but not storing ions, or inorganic particles capable of undergoing electrochemical reactions.

[0639] In some embodiments, inorganic particles having a dielectric constant of 5 or higher may include boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxides, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, aluminum hydroxide, barium oxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, calcium fluoride, barium fluoride, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hydropyrite, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb1-mLamZr1-nTinO3 (abbreviated as PLZT, 0 < m < 1, 0 < n < 1), Pb(Mg3Nb) 2 / 3 The inorganic particles can be selected from one or more of PbTiO3 (PMN-PT) and their respective modified inorganic particles. Optionally, the modification of each inorganic particle can be chemical modification and / or physical modification.

[0640] In some embodiments, inorganic particles that are ion-conductive but do not store ions may include Li3PO4, lithium titanium phosphate (Li3PO4), etc. x3 Ti y3 (PO4)3, Lithium aluminum titanium phosphate (Li) x4 Al y4 Ti z4 (PO4)3、(LiAlTiP) x5 O y5 Type glass, lithium lanthanum titanate (Li) x6 La y6 TiO3, lithium germanium thiophosphate Li x7 Ge y7 P z7 S e Lithium nitride (Li) x8 N y8SiS2 type glass Li x9 Si y9 S z9 and P2S5 type glass Li x10 P y10 S z10 One or more of the following are given: 0 < x3 < 2, 0 < y3 < 3, 0 < x4 < 2, 0 < y4 < 1, 0 < z4 < 3, 0 < x5 < 4, 0 < y5 < 13, 0 < x6 < 2, 0 < y6 < 3, 0 < x7 < 4, 0 < y7 < 1, 0 < z7 < 1, 0 < e < 5, 0 < x8 < 4, 0 < y8 < 2, 0 < x9 < 3, 0 < y9 < 2, 0 < z9 < 4, 0 < x10 < 3, 0 < y10 < 3, 0 < z10 < 7. This can improve the ion conductivity of the separator.

[0641] In some embodiments, the inorganic particles capable of undergoing electrochemical reactions may include one or more of lithium transition metal oxides, lithium transition metal phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium titanium compounds.

[0642] In some embodiments, the organic particles may include at least one of a thermoplastic resin polymer, a thermosetting resin polymer, or a crosslinked polymer.

[0643] In some embodiments, the thermoplastic resin polymer may include one or more of the following: polycarbonate organic particles, polymethyl methacrylate organic particles, polyoxymethylene organic particles, polyamide organic particles, styrene-acrylonitrile copolymer, polyphenylene sulfide organic particles, polyetheretherketone organic particles, polyimide organic particles, polysulfone organic particles, polyethersulfone organic particles, polyphenylene sulfone organic particles, polybenzimidazole organic particles, polyamide-imide organic particles, and polyethyleneimine organic particles.

[0644] In some embodiments, the thermosetting resin polymer may include one or more of the following: phenolic resin organic particles, polymer particles containing triazine ring structural units, epoxy resin organic particles, unsaturated polyester resin organic particles, urea-formaldehyde resin organic particles, and furan resin organic particles.

[0645] In some embodiments, the crosslinking polymer may include one or more of crosslinked styrene organic particles and silicon-containing organic crosslinked resin particles.

[0646] In some embodiments, the coating includes adhesive particles. The adhesive particles may include homopolymers or copolymers of acrylate monomer units, homopolymers or copolymers of acrylic monomer units, homopolymers or copolymers of styrene monomer units, polyurethane compounds, rubber compounds, homopolymers or copolymers of fluorinated alkenyl monomer units, homopolymers or copolymers of olefinic monomer units, homopolymers or copolymers of unsaturated nitrile monomer units, homopolymers or copolymers of epoxide monomer units, and one or more of the modified compounds of the above homopolymers or copolymers.

[0647] In some embodiments, the adhesive particles may include copolymers of acrylate monomer units and styrene monomer units, copolymers of acrylate monomer units and styrene monomer units, copolymers of acrylate monomer units, acrylate monomer units, and styrene monomer units, copolymers of styrene monomer units and unsaturated nitrile monomer units, copolymers of styrene monomer units, olefin monomer units, and unsaturated nitrile monomer units, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, copolymers of different fluorinated alkenyl monomer units, copolymers of fluorinated alkenyl monomer units and vinyl monomer units, copolymers of fluorinated alkenyl monomer units and acrylate monomer units, copolymers of fluorinated alkenyl monomer units and acrylate monomer units, and one or more of the modified compounds of the above homopolymers or copolymers.

[0648] In some embodiments, the adhesive particles may include one or more of the following: butyl acrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate copolymer, isooctyl methacrylate-styrene copolymer, methacrylate-methacrylate-styrene copolymer, methyl acrylate-isooctyl methacrylate-styrene copolymer, butyl acrylate-isooctyl methacrylate-styrene copolymer, butyl acrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate-styrene copolymer, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, methyl acrylate-styrene-acrylonitrile copolymer, isooctyl methacrylate-styrene-acrylonitrile copolymer, styrene-vinyl acetate copolymer, styrene-vinyl acetate-pyrrolidone copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, vinylidene fluoride-hexafluoropropylene-acrylate copolymer, and a modified compound of the above copolymers.

[0649] In some embodiments, the coating may further include a dispersant, such as one or more of alkylphenol polyoxyethylene ethers, polyacrylic acid dispersants, and cellulose dispersants, including but not limited to. For example, the dispersant may include one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0650] [Battery Device]

[0651] This application provides a battery device including the battery cells described in the above embodiments. The battery device can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed via a busbar.

[0652] In some embodiments, the battery device may be a battery pack, and the battery includes a housing and individual battery cells, with the individual battery cells or battery modules housed in the housing.

[0653] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0654] In some embodiments, the battery device may be located within an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0655] Figure 21 This is a schematic diagram of a battery device according to one embodiment of this application. For example, such as... Figure 21 As shown, the battery device 60 of this application embodiment may include a plurality of battery cells 100 to meet different power usage requirements. The shape of the battery cell 100 in this application embodiment can be set according to actual application. For example, the battery cell 100 can be cylindrical, or it can be cuboid or other shapes, and this application embodiment is not limited to this.

[0656] It should be understood that, such as Figure 21 As shown, the battery device 60 of this embodiment may further include a housing 61, which can be used to accommodate multiple battery cells 100. The housing 61 of this embodiment has a hollow interior, and the multiple battery cells 100 are accommodated within the housing 61. The housing 61 may include two parts, referred to herein as a first housing portion 611 and a second housing portion 612, which are fastened together. The shapes of the first housing portion 611 and the second housing portion 612 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 100 housed inside. At least one of the first housing portion 611 and the second housing portion 612 has an opening. For example, as... Figure 21As shown, the first housing portion 611 and the second housing portion 612 can both be hollow cuboids with one open side. The openings of the first housing portion 611 and the second housing portion 612 are opposite to each other, and the first housing portion 611 and the second housing portion 612 are interlocked to form a housing 61 with a closed cavity, which can accommodate multiple battery cells 100. The multiple battery cells 100 are connected in parallel, series, or mixed and placed inside the housing 61 formed by the interlocking of the first housing portion 611 and the second housing portion 612.

[0657] For example, unlike Figure 21 As shown, either the first housing portion 611 or the second housing portion 612 may have only one hollow cuboid with an opening, while the other is plate-shaped to cover the opening. Taking the second housing portion 612 as a hollow cuboid with one opening and the first housing portion 611 as a plate-shaped example, then the first housing portion 611 covers the opening of the second housing portion 612 to form a housing 61 with a closed chamber, which can be used to accommodate multiple battery cells 100.

[0658] [Electrical Equipment]

[0659] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells.

[0660] 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.

[0661] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0662] Figure 22 This is a schematic diagram of an electrical device according to one embodiment of this application. For example, such as... Figure 22The diagram shown is a structural schematic of a vehicle 70 according to one embodiment of this application. The vehicle 70 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. The vehicle 70 can have a motor 80, a controller 90, and a battery device 60 installed inside. The controller 90 controls the battery device 60 to supply power to the motor 80. For example, the battery device 60 can be installed at the bottom, front, or rear of the vehicle 70. The battery device 60 can be used to power the vehicle 70; for example, it can serve as the operating power source for the vehicle 70's electrical system, such as meeting the power requirements for starting, navigation, and operation. In another embodiment of this application, the battery device 60 can not only serve as the operating power source for the vehicle 70 but also as the driving power source, replacing or partially replacing gasoline or natural gas to provide driving power to the vehicle 70.

[0663] 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.

[0664] [Examples and Comparative Examples]

[0665] [Example 1]

[0666] 1. Preparation of positive electrode sheet

[0667] The positive electrode includes a positive current collector and a positive electrode film layer on the positive current collector. The positive electrode film layer is disposed on both sides of the positive current collector, and the positive current collector is a 13μm aluminum foil.

[0668] The positive electrode film consists of a film formed by uniformly coating a positive electrode slurry (using N-methylpyrrolidone, NMP) onto the surface of the positive electrode current collector, followed by drying and cold pressing. The positive electrode film comprises lithium iron phosphate as the positive electrode active material, polyvinylidene fluoride (PVDF) as the binder, and conductive carbon black as the conductive agent, in a mass ratio of 97:2:1. The areal density of the positive electrode film is 390 mg / 1540.25 mm². 2 .

[0669] 2. Preparation of negative electrode sheet

[0670] The negative electrode sheet includes a negative current collector and a negative electrode film layer on the negative current collector. The negative electrode film layer is disposed on both sides of the negative current collector, and the negative current collector is a copper foil with a thickness of 5μm.

[0671] The negative electrode film layer comprises a film formed by uniformly coating a negative electrode slurry (using deionized water as the solvent) onto the surface of the negative electrode current collector, followed by drying and cold pressing. The negative electrode film layer includes graphite (a negative electrode active material), CMC-Na (a thickener), SBR (a binder), and conductive carbon black (a conductive agent) in a mass ratio of 96.5:0.5:2:1. The single-sided areal density of the negative electrode film layer is 174 mg / 1540.25 mm². 2 .

[0672] 3. Separating membrane

[0673] The separator membrane includes a base membrane, a first coating, and a second coating. The base membrane consists of 7μm polyethylene (PE), and the separator membrane has a porosity of 45%.

[0674] The second coating is a film layer with a thickness of 1.5 μm formed by coating alumina particles and PVDF binder on both sides of the base film.

[0675] The first coating is a film formed by coating polyvinylidene fluoride onto the second coating, and the thickness of the first coating is 1.5 μm.

[0676] 4. Preparation of electrolyte

[0677] The electrolyte consists of organic solvents, lithium electrolyte salts, and additives.

[0678] The components of each organic solvent are mixed, and then an electrolyte lithium salt and additives are added to prepare an electrolyte.

[0679] The organic solvents include ethyl acetate (EA) at 57% by mass and ethylene carbonate (EC) at 25% by mass. The mass percentage of each component in the solvent is calculated based on the total mass of the electrolyte.

[0680] Based on the total mass of the electrolyte, the electrolyte also includes 0.03% by mass of tris(trimethylsilane) phosphate (TMSP), 2.9% by mass of vinylene carbonate (VC), 0.05% by mass of fluoroethylene carbonate (FEC), and 0.02% by mass of lithium difluorooxalate borate (LiDFOB).

[0681] The electrolyte lithium salt comprises 10% lithium hexafluorophosphate (LiPF6) and 5% lithium bisfluorosulfonylimide (LiFSI) by mass.

[0682] 5. Preparation of battery cells

[0683] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes, to obtain a stacked electrode assembly. The electrode assembly is placed in a housing, with the positive and negative terminals set on the housing. After baking, electrolyte is injected (multiple injections can be performed if necessary). After vacuum sealing, settling, formation, and shaping, a battery cell is obtained.

[0684] The compaction density of the positive electrode sheet of the battery cell is 2.5 g / cm³. 3 The compaction density of the negative electrode sheet is 1.47 g / cm³. 3 The conductivity of the electrolyte is 15.7 mS / cm.

[0685] The outer casing comprises a rectangular aluminum shell. The thickness of the large-face shell of the battery cell is 0.35 mm, and the thickness of the side shells of the battery cell is 0.35 mm. The thickness of the large-face shell refers to the thickness of the first wall of the casing, and the thickness of the side shells refers to the thickness of the second wall of the casing. The positive electrode tab is located on one side of the positive current collector along the length direction of the battery cell (the longer side of the positive current collector is parallel to the length direction of the battery cell), and the negative electrode tab is located on one side of the negative current collector along the length direction of the battery cell (the longer side of the negative current collector is parallel to the length direction of the battery cell). The main body of the electrode assembly has a length of 485.5 mm, a thickness of 13.8 mm, and a width of 115 mm; the area of ​​the first side surface of the main body is 558.3 ​​cm². 2 The area of ​​the second side of the main body is 67cm². 2 .

[0686] Example 2-3

[0687] Battery cells were prepared using a method similar to that of Example 1, except that the length of the main body of the electrode assembly was adjusted.

[0688] Comparative Example 1

[0689] Battery cells were prepared using a method similar to that of Example 1, except that the length of the main body of the electrode assembly was adjusted.

[0690] It should be noted that in Examples 2-3 and Comparative Example 1, the volume of the electrode assembly remains unchanged. Therefore, when adjusting the length of the main body of the electrode assembly, the width of the main body needs to be adjusted appropriately to keep the volume of the electrode assembly unchanged.

[0691] Examples 4-5

[0692] Battery cells were prepared using a method similar to that of Example 1, except that the thickness of the main body of the electrode assembly was adjusted.

[0693] Comparative Example 2

[0694] Battery cells were prepared using a method similar to that of Example 1, except that the thickness of the main body of the electrode assembly was adjusted.

[0695] It should be noted that in Examples 4-5 and Comparative Example 2, the volume of the electrode assembly remains unchanged. Therefore, when adjusting the thickness of the main body of the electrode assembly, it is necessary to adjust the width or length of the main body appropriately to keep the volume of the electrode assembly unchanged.

[0696] Examples 6-7

[0697] The battery cell was prepared using a method similar to that of Example 1. The difference from Example 1 is that the width and thickness of the main body were adjusted, thereby adjusting the ratio of the area of ​​the first side to the area of ​​the second side of the main body.

[0698] The product parameters and performance parameters of Examples 1-7 and Comparative Examples 1-2 are detailed in Table 1 below.

[0699] Table 1. Product parameters and performance parameters of Examples 1-7 and Comparative Examples 1-2

[0700]

[0701] In Table 1 above, the area ratio represents the ratio of the area of ​​the first side to the area of ​​the second side.

[0702] Combining the results of Examples 1-7 and Comparative Examples 1-2, it can be seen that when the single-sided areal density of the positive electrode sheet is set within the range of this application, i.e., when the positive electrode sheet is thickly coated, and when the length of the main body of the electrode assembly is greater than 400 mm, the thickness of the main body is less than 20 mm, and the area ratio of the large surface (first side) of the electrode assembly to other sides (second side) is greater than 6, the energy density of the battery cell can be increased while the aging rate of the battery cell is reduced, resulting in better high-temperature cycle performance and improved reliability of the thickly coated battery cell. In Comparative Example 1, although the areas of the first and second sides are relatively large (greater than 6), the length of the main body is only 200 mm, less than 400 mm. Because the length of the main body of the electrode assembly in Comparative Example 1 is small, unlike the long electrode assembly design of this application, the volume ratio of the active material inside the battery cell is reduced, resulting in a significant decrease in the energy density of the battery cell. In Comparative Example 2, although the length of the main body of the electrode assembly is greater than 400 mm, its thickness is greater than 20 mm, and the area of ​​the first side and the second side is only 3.3, which is less than 6. The large area occupies a smaller proportion than in Comparative Examples 1-7, which is not conducive to heat dissipation of the battery cell, accelerates the aging of the battery cell, and leads to a reduction in the high-temperature cycle life of the battery cell.

[0703] Examples 8-9

[0704] Battery cells were prepared using a method similar to that of Example 1, except that the surface density of the positive electrode film was adjusted.

[0705] Comparative Example 4

[0706] Battery cells were prepared using a method similar to that of Example 1, except that the surface density of the positive electrode film was adjusted.

[0707] The product parameters and performance parameters of Examples 8-9 and Comparative Example 4 are detailed in Table 2 below.

[0708] Table 2 Product parameters and performance parameters of Examples 8-9 and Comparative Example 4

[0709]

[0710] In Table 2 above, the area ratio represents the ratio of the area of ​​the first side to the area of ​​the second side.

[0711] Based on the results of Examples 8-9 and Comparative Example 4, it can be seen that increasing the areal density of one side of the positive electrode sheet can effectively improve the energy density of the battery cell, but it will reduce the high-temperature cycle performance of the battery cell. However, because the length of the electrode assembly body is greater than 400 mm, the thickness is less than 20 mm, and the area ratio of the first side surface to the second side surface is greater than 6, the battery cell has good heat dissipation performance, thus the battery cell still has good high-temperature cycle life. Therefore, the solution of this application can improve the energy density of the battery cell while taking into account the heat dissipation performance of the battery cell, and has good high-temperature cycle life.

[0712] 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.

[0713] 1. Testing the energy density of individual battery cells

[0714] At 25℃, the battery cell is charged at a constant current of 0.33C to the cutoff voltage of 3.8V, 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 volume V of the battery cell is length × thickness × width. The energy density of the battery cell is E0 / V, and the unit can be Wh / L.

[0715] 2. High-temperature cycle performance test of individual battery cells

[0716] At 45℃, the battery cell is charged at an equivalent 2.2C to 80% SOC, then charged at 0.33C (CC+CV) to 3.8V. The battery cell is then left to rest for 10 minutes, followed by discharge at 1C to 2.0V. The battery cell capacity at this point is recorded as C0. The above steps are repeated until the battery cell discharge capacity decays to 80% of the initial discharge capacity. The test is then stopped, and the number of cycles is recorded. Here, CC represents constant current charging, and CV represents constant voltage charging.

[0717] The capacity retention rate (%) of a battery after n cycles at 45℃ = (discharge capacity of the battery in the nth cycle / discharge capacity of the battery in the first cycle) × 100%.

[0718] 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.

Claims

1. A battery cell, characterized in that, include: The housing includes a shell, a positive terminal cap assembly, and a negative terminal cap assembly, the positive terminal cap assembly and the negative terminal cap assembly being used to close the opening of the shell; An electrode assembly is provided, wherein an accommodating space is formed within the housing to accommodate the electrode assembly, the electrode assembly comprising a positive electrode and a negative electrode disposed along the thickness direction of the battery cell, and the electrode assembly having a stacked structure; The electrode assembly includes a main body and a tab located on the end face of the main body. The main body has a dimension greater than 400 mm in a first direction and a dimension less than 20 mm in the thickness direction of the battery cell. The first direction is the extension direction of the longest side of the electrode assembly. The main body includes a first side and a second side extending along the first direction. The first side is the surface with the largest area of ​​the electrode assembly, and the ratio of the area of ​​the first side to the area of ​​the second side is greater than 6. The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector, wherein the single-sided areal density of the positive electrode film layer is greater than 375 mg / 1540.25 mm². 2 The ratio of the thickness of the positive electrode film to the thickness of the positive electrode current collector is greater than 6.

5. The battery cell also includes an electrolyte, which further includes a lithium salt. Based on the total mass of the electrolyte, the mass content of the lithium salt is 12% to 21%.

2. The battery cell according to claim 1, characterized in that, The main body has a dimension of 450mm to 650mm in the first direction.

3. The battery cell according to claim 1 or 2, characterized in that, The main body has a thickness of 13mm to 18mm in the thickness direction of the battery cell.

4. The battery cell according to claim 1, characterized in that, The ratio of the area of ​​the first side to the area of ​​the second side is 7 to 10.

5. The battery cell according to claim 1, characterized in that, The areal density of the positive electrode film is 380 mg / 1540.25 mm². 2 ~420mg / 1540.25mm 2 .

6. The battery cell according to claim 1, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector, wherein the single-sided areal density of the negative electrode film layer is 165 mg / 1540.25 mm². 2 ~185mg / 1540.25mm 2 .

7. The battery cell according to claim 6, characterized in that, The battery cell satisfies: The ratio of the thickness of the negative electrode film to the thickness of the negative electrode current collector is greater than 12.

8. The battery cell according to claim 6 or 7, characterized in that, The battery cell satisfies at least one of the following conditions: (1) The ratio of the thickness of the negative electrode film to the thickness of the negative electrode current collector is 13~18; (2) The ratio of the thickness of the positive electrode film to the thickness of the positive electrode current collector is 7 to 9.

9. The battery cell according to claim 1, characterized in that, When the battery cell has a state of 0% SOC, the compaction density of the positive electrode sheet is 2.3 g / cm³. 3 ~2.65g / cm 3 .

10. The battery cell according to claim 1, characterized in that, When the battery cell has a state of 0% SOC, the compaction density of the positive electrode sheet is 2.45 g / cm³. 3 ~2.6g / cm 3 .

11. The battery cell according to claim 1, characterized in that, When the battery cell has a state of 0% SOC, the compaction density of the negative electrode sheet is 1.3 g / cm³. 3 ~1.52g / cm 3 .

12. The battery cell according to claim 1, characterized in that, When the battery cell has a state of 0% SOC, the compaction density of the negative electrode sheet is 1.3 g / cm³. 3 ~1.5g / cm 3 .

13. The battery cell according to claim 1, characterized in that, The battery cell satisfies at least one of the following conditions: (1) In the first direction, the ratio of the size of the positive electrode film to the size of the housing is 93.7% to 95.6%; (2) In the second direction, the ratio of the size of the positive electrode film to the size of the housing is 92.8% to 95%, and the second direction is perpendicular to the first direction and the thickness direction of the battery cell.

14. The battery cell according to claim 1, characterized in that, The battery cell satisfies at least one of the following conditions: (1) The dimensions of the positive electrode film layer in the first direction are 421.5 mm to 621.5 mm; (2) The positive electrode film layer has a size of 83.5 mm to 123.5 mm in the second direction, which is perpendicular to the first direction and the thickness direction of the battery cell.

15. The battery cell according to claim 1, characterized in that, The battery cell satisfies at least one of the following conditions: (1) The ratio of the size of the main body in the first direction to the size of the main body in the second direction is greater than 3, and the second direction is perpendicular to the first direction and the thickness direction of the battery cell; (2) The main body has a size of 90mm to 130mm in the second direction.

16. The battery cell according to claim 15, characterized in that, The ratio of the dimension of the main body in the first direction to the dimension of the main body in the second direction is 4 to 6.

17. The battery cell according to claim 1, characterized in that, The electrode portion includes a positive electrode and a negative electrode, and the main body portion includes a first end face and a second end face disposed opposite to each other along the first direction. The positive electrode is located on the first end face side and is welded to the positive end cap assembly, and the negative electrode is located on the second end face side and is welded to the negative end cap assembly.

18. The battery cell according to claim 17, characterized in that, An insulating support is provided between the first end face and the positive end cap assembly. The insulating support is provided with a receiving cavity corresponding to the positive electrode tab. The receiving cavity is configured to gather at least a portion of the positive electrode tab.

19. The battery cell according to claim 18, characterized in that, The insulating support includes a first boss, a second boss, a first beam, and a second beam facing the electrode assembly; The first boss and the second boss are disposed on both sides of the insulating support in the second direction. The first beam and the second beam are disposed on both sides of the insulating support along the thickness direction of the battery cell and connect the first boss and the second boss. The second direction is perpendicular to the first direction and the thickness direction of the battery cell.

20. The battery cell according to claim 19, characterized in that, In the first direction, the dimensions of the first boss and the second boss are larger than the dimensions of the first beam and the second beam.

21. The battery cell according to claim 19 or 20, characterized in that, In the first direction, the dimensions of the first boss and the second boss are 4mm to 10mm.

22. The battery cell according to claim 19, characterized in that, In the first direction, the dimensions of the first beam and the second beam are 3mm to 8mm.

23. The battery cell according to claim 19, characterized in that, The positive terminal cap assembly includes a positive terminal cap and at least two positive terminals disposed on the positive terminal cap.

24. The battery cell according to claim 23, characterized in that, The positive terminal includes a first portion and a second portion connected together. The first portion is located on the side of the positive terminal cover facing the electrode assembly and is welded to the positive electrode tab. The second portion is on the side opposite to the electrode assembly and protrudes through the positive terminal cover. Along the first direction, the projection of the first portion overlaps the projection of the second portion; and / or, The positive electrode tab is welded to at least two of the first portions.

25. The battery cell according to claim 24, characterized in that, The first part and the second part are an integral structure.

26. The battery cell according to claim 24 or 25, characterized in that, The positive terminal includes a first positive terminal and a second positive terminal, and the positive terminal cover assembly includes a first busbar component, which is disposed on the side of the positive terminal cover opposite to the electrode assembly. The first busbar component includes a first through hole and a second through hole. A second portion of the first positive terminal passes through the first through hole along the first direction and is connected to the first busbar component. A second portion of the second positive terminal passes through the second through hole along the first direction and is connected to the first busbar component.

27. The battery cell according to claim 24, characterized in that, In the first direction, the size of the first portion is 1mm to 1.5mm.

28. The battery cell according to claim 24, characterized in that, The total cross-sectional area of ​​the first part is 70 mm². 2 ~210mm 2 .

29. The battery cell according to claim 24, characterized in that, The positive end cap assembly includes a first insulating member; The first insulating member is disposed between the insulating support and the positive terminal cover, and is used to insulate the electrode assembly and the positive terminal cover.

30. The battery cell according to claim 29, characterized in that, The first insulating member includes a first wall that abuts against the positive terminal cap and a first recess facing the electrode assembly; The first wall is provided with a first straight portion and a third through hole for the second portion to pass through, and the first recess is used to accommodate at least part of the first portion.

31. The battery cell according to claim 30, characterized in that, At least a portion of the first boss and / or the second boss abuts against the first insulating member.

32. The battery cell according to claim 30 or 31, characterized in that, In the first direction, the size of the first straight portion is 1mm to 3mm.

33. The battery cell according to claim 30, characterized in that, The positive end cap includes a pressure relief mechanism; The first straight portion is provided with a fourth through hole corresponding to the pressure relief mechanism, and the first protrusion is provided with a fifth through hole corresponding to the fourth through hole.

34. The battery cell according to claim 24, characterized in that, The main body includes a positive electrode plate main body, and the positive electrode tab extends from the positive electrode plate main body along the first direction; In the second direction, the ratio of the size of the positive electrode tab to the size of the positive electrode body is greater than 50%.

35. The battery cell according to claim 34, characterized in that, In the second direction, the ratio of the size of the positive electrode tab to the size of the positive electrode body is 60% to 100%.

36. The battery cell according to claim 34 or 35, characterized in that, The first portion has a first surface adjacent to the electrode assembly; In the first direction, the distance between the edge of the positive electrode film and the first surface is 7mm~10mm.

37. The battery cell according to claim 34, characterized in that, The total area of ​​the first welding region formed by welding the positive electrode tab to the first part is 130 mm. 2 ~200mm 2 .

38. The battery cell according to claim 34, characterized in that, The positive electrode sheet has a chamfered structure at the apex corner of the second end face.

39. The battery cell according to claim 38, characterized in that, The dimension of the chamfered structure on the extension line of the second direction is greater than the dimension on the extension line of the first direction.

40. The battery cell according to claim 39, characterized in that, Along the extension of the first direction, the size of the chamfer structure is 1mm to 2mm; Along the extension of the second direction, the chamfer structure has a size of 1mm to 10mm.

41. The battery cell according to any one of claims 38 to 40, characterized in that, The chamfered structure is a fan-shaped structure.

42. The battery cell according to claim 36, characterized in that, The positive electrode sheet includes a first transition region. Along the first direction, the first transition region is located at one end of the positive electrode film layer near the positive electrode tab and is adjacent to the positive electrode film layer. The first transition zone is provided with insulating material.

43. The battery cell according to claim 42, characterized in that, In the first direction, the size of the first transition region is 1.5mm to 4mm.

44. The battery cell according to claim 42 or 43, characterized in that, The positive electrode tab includes a second transition region. Along the first direction, the second transition region is located at one end of the positive electrode tab near the main body and is adjacent to the first transition region. The second transition zone is provided with insulating material.

45. The battery cell according to claim 44, characterized in that, In the first direction, the size of the second transition region is 4mm to 7mm.

46. ​​The battery cell according to claim 44, characterized in that, In the first direction, the size ratio of the second transition region to the positive electrode tab is 1 / 6 to 1 / 3.

47. The battery cell according to claim 17, characterized in that, The negative end cap assembly includes a negative end cap and at least two negative ends disposed on the negative end cap.

48. The battery cell according to claim 47, characterized in that, The negative terminal includes a connected third portion and a fourth portion. The third portion is located on the side of the negative terminal cover facing the electrode assembly and is welded to the negative electrode tab. The fourth portion is on the side opposite to the electrode assembly and protrudes through the negative terminal cover. Along the first direction, the projection of the third portion overlaps the projection of the fourth portion; and / or, The negative electrode tab is welded to at least two of the third parts.

49. The battery cell according to claim 48, characterized in that, The third part and the fourth part are an integral structure.

50. The battery cell according to claim 48 or 49, characterized in that, The negative terminal includes a first negative terminal and a second negative terminal, and the negative terminal cover assembly includes a second busbar component, which is disposed on the side of the negative terminal cover opposite to the electrode assembly. The second busbar component includes a sixth through hole and a seventh through hole. The fourth part of the first negative terminal passes through the sixth through hole along the first direction and is connected to the second busbar component. The fourth part of the second negative terminal passes through the seventh through hole along the first direction and is connected to the second busbar component.

51. The battery cell according to claim 48, characterized in that, In the first direction, the size of the third part is 1.2mm to 2.5mm.

52. The battery cell according to claim 48, characterized in that, The total cross-sectional area of ​​the third part is 70mm². 2 ~210mm 2 .

53. The battery cell according to claim 48, characterized in that, The negative end cap assembly includes a second insulating member; The second insulating member is disposed between the electrode assembly and the negative terminal cap to insulate the electrode assembly and the negative terminal cap.

54. The battery cell according to claim 53, characterized in that, The second insulating member includes a second wall that abuts against the negative terminal cap and a second recess facing the electrode assembly; The second wall is provided with a second straight portion and an eighth through hole through which the fourth portion passes, and the second recess is used to accommodate at least a portion of the third portion and at least a portion of the negative electrode tab.

55. The battery cell according to claim 54, characterized in that, The side of the second insulating member closest to the electrode assembly abuts against at least a portion of the electrode assembly.

56. The battery cell according to claim 54 or 55, characterized in that, In the first direction, the size of the second straight portion is 6mm to 9mm.

57. The battery cell according to claim 53, characterized in that, The negative end cap also includes a liquid injection mechanism, and the second insulating member is provided with a ninth through hole, which corresponds to the liquid injection mechanism.

58. The battery cell according to claim 53, characterized in that, The main body includes a negative electrode sheet main body, and the negative electrode tab extends from the negative electrode sheet main body along the first direction; In the second direction, the ratio of the size of the negative electrode tab to the size of the negative electrode body is greater than 50%; the second direction is perpendicular to the first direction and the thickness direction of the battery cell.

59. The battery cell according to claim 58, characterized in that, In the second direction, the ratio of the size of the negative electrode tab to the size of the negative electrode body is 60% to 100%.

60. The battery cell according to claim 58 or 59, characterized in that, The third portion has a second surface adjacent to the electrode assembly; The negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. In the first direction, the dimension between the edge of the negative electrode film layer and the second surface is 7mm to 10mm.

61. The battery cell according to claim 58, characterized in that, The total area of ​​the second welding region formed by welding the negative electrode tab to the third part is 130 mm. 2 ~200mm 2 .

62. The battery cell according to claim 60, characterized in that, In the first direction, the edge of the negative electrode film extends beyond the edge of the positive electrode film; In the second direction, the edge of the negative electrode film extends beyond the edge of the positive electrode film.

63. The battery cell according to claim 62, characterized in that, In the first direction, the distance by which the edge of the negative electrode film extends beyond the edge of the positive electrode film is OH1, and in the second direction, the distance by which the edge of the negative electrode film extends beyond the positive electrode film is OH2. The OH1 is 3mm~8mm, and the OH2 is 1mm~4mm.

64. The battery cell according to claim 42, characterized in that, In the thickness direction of the battery cell, the projection of the first transition region covers the projection of the edge of the negative electrode film layer.

65. The battery cell according to claim 1, characterized in that, The positive electrode film layer includes a positive electrode active material, which includes lithium transition metal phosphate; The negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes graphite.

66. The battery cell according to claim 65, characterized in that, The lithium transition metal phosphate includes at least one of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium nickel phosphate, and lithium cobalt phosphate.

67. The battery cell according to claim 65 or 66, characterized in that, The volume average particle size Dv50 of the graphite is 8μm~13μm.

68. The battery cell according to claim 65, characterized in that, The negative electrode film layer includes a first film layer and a second film layer, wherein the first film layer is located between the negative electrode current collector and the second film layer; The graphite in the first film layer includes artificial graphite or a mixture of artificial graphite and natural graphite, and the average particle size of the longest diameter of the graphite is 7μm~18μm; The graphite in the second film layer includes artificial graphite or a mixture of artificial graphite and natural graphite, and the average particle size of the longest diameter of the graphite is 6μm to 10μm.

69. The battery cell according to claim 68, characterized in that, The battery cell satisfies at least one of the following conditions: (1) The average particle size of the graphite in the negative electrode film is 7μm~15μm, and the graphite in the negative electrode film includes secondary particles; (2) The graphitization degree of the graphite in the negative electrode film is 90%~94%.

70. The battery cell according to claim 65, characterized in that, A first functional layer is disposed between the negative electrode current collector and the negative electrode film layer, the first functional layer comprising an adhesive and a conductive agent; The thickness of the first functional layer is 0.2 μm to 3 μm; The adhesive includes at least one of styrene-butadiene rubber, water-soluble unsaturated resin, water-based acrylic resin, polyvinyl alcohol, sodium alginate, and carboxymethyl chitosan. The conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

71. The battery cell according to claim 1, characterized in that, When the cell is at 0% SOC, the porosity of the negative electrode sheet is 25%~40%.

72. The battery cell according to claim 1, characterized in that, The battery cell also includes a separator, and the positive electrode, the separator, and the negative electrode are stacked in the thickness direction of the battery cell. The isolation membrane includes a base membrane and a second functional layer disposed on at least one side of the base membrane, the second functional layer including inorganic particles.

73. The battery cell according to claim 72, characterized in that, The inorganic particles include one or more of silicon dioxide, aluminum oxide, boehmite, barium sulfate, calcium oxide, titanium dioxide, zinc oxide, magnesium oxide, zirconium oxide, and tin oxide; and / or The average particle size of the inorganic particles is 5 nm to 100 nm.

74. The battery cell according to claim 72 or 73, characterized in that, The separator further includes a third functional layer located on the side of the second functional layer away from the base membrane, and the third functional layer includes a fluorinated adhesive.

75. The battery cell according to claim 72, characterized in that, The thickness of the base film is less than 9 μm.

76. The battery cell according to claim 75, characterized in that, The thickness of the base film is 4μm~7μm.

77. The battery cell according to claim 72, characterized in that, The thickness of the second functional layer is 0.5μm~1.5μm.

78. The battery cell according to claim 74, characterized in that, The thickness of the third functional layer is 1μm to 2.5μm.

79. The battery cell according to claim 72, characterized in that, The thickness of the isolation membrane is 9μm~12μm.

80. The battery cell according to claim 1, characterized in that, The thickness of the shell is less than 0.5 mm.

81. The battery cell according to claim 1, characterized in that, The thickness of the shell is 0.3mm to 0.4mm.

82. The battery cell according to claim 1, characterized in that, The shell is made of a metallic material, including aluminum or steel.

83. The battery cell according to claim 1, characterized in that, The housing includes a first sidewall and a second sidewall extending along the first direction, the first sidewall being the wall with the largest surface area of ​​the housing, and the housing including a weld located on the second sidewall and extending along the first direction.

84. The battery cell according to claim 1, characterized in that, The electrolyte is contained within the accommodating space, and the electrolyte includes an organic solvent, which includes dimethyl carbonate and linear carboxylic acid esters. Based on the total mass of the electrolyte, the sum of the mass contents of the dimethyl carbonate and the linear carboxylic acid ester is 10% to 60%.

85. The battery cell according to claim 84, characterized in that, Based on the total mass of the electrolyte, the sum of the mass contents of the dimethyl carbonate and the linear carboxylic acid ester is 40% to 60%.

86. The battery cell according to claim 84 or 85, characterized in that, The linear carboxylic acid esters include compounds represented by formula (I). Equation (I) R1 and R2 each independently include alkyl or haloalkyl groups having 1 to 5 carbon atoms.

87. The battery cell according to claim 86, characterized in that, The linear carboxylic acid ester includes at least one of ethyl acetate, methyl acetate, methyl propionate, propyl acetate, ethyl formate, and isopropyl formate.

88. The battery cell according to claim 1, characterized in that, The lithium salt includes lithium fluorosulfonylimide and lithium hexafluorophosphate; In the electrolyte, the mass ratio of lithium hexafluorophosphate to lithium fluorosulfonyl imide is 0.8 to 3.

5.

89. The battery cell according to claim 88, characterized in that, The fluorinated sulfonylimide lithium includes at least one of lithium bisfluorosulfonylimide and lithium bistrifluoromethanesulfonate imide.

90. The battery cell according to claim 1, characterized in that, The electrolyte also includes additives, which include at least one of vinylene carbonate, fluoroethylene carbonate, and vinyl sulfate. The additive has a mass content of 0.1% to 5% based on the total mass of the electrolyte.

91. The battery cell according to claim 1, characterized in that, The conductivity of the electrolyte is 13 ms / cm to 20 ms / cm.

92. The battery cell according to claim 1, characterized in that, The conductivity of the electrolyte is 13 ms / cm to 17 ms / cm.

93. The battery cell according to claim 1, characterized in that, The outer casing has a first insulating film on the side of its outer surface facing away from the electrode assembly, and the thickness of the first insulating film is 0.05mm to 0.2mm. The material of the first insulating film includes at least one of polyethylene terephthalate, polypropylene, and polyimide.

94. The battery cell according to claim 93, characterized in that, The first insulating film has openings.

95. The battery cell according to claim 1, characterized in that, A second insulating film is provided between the main body and the housing, the second insulating film being used to insulate the main body and the housing; The second insulating film includes at least one of polypropylene and polyethylene terephthalate.

96. The battery cell according to claim 1, characterized in that, The battery cell also includes a side support plate, which is disposed between the housing and the electrode assembly. The side support plate extends along the first direction and is disposed opposite to the second side.

97. The battery cell according to claim 1, characterized in that, When the battery cell is charged at a 1 / 3C rate, the volumetric energy density of the battery cell is 440Wh / L~460Wh / L.

98. The battery cell according to claim 1, characterized in that, When the battery cell is charged at a 1 / 3C rate, the mass energy density of the battery cell is 190Wh / kg to 200Wh / kg.

99. A battery device, characterized in that, include: Multiple battery cells according to any one of claims 1 to 98.

100. An electrical appliance, characterized in that, include: Multiple battery cells according to any one of claims 1 to 98, or battery devices according to claim 99, wherein the battery cells or battery devices are used to store or provide electrical energy.

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