Battery cell, battery device, and electric device

Abstract

The invention discloses a battery monomer, a battery device and a power utilization device. The battery monomer comprises an electrode assembly, the electrode assembly comprises a plurality of positive pole pieces and a plurality of negative pole pieces which are stacked in a third direction, and a positive pole lug located at a first side end in a second direction of the electrode assembly and a negative pole lug located at a second side end in the second direction of the electrode assembly; the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer positioned on at least one side of the negative electrode current collector, and the negative electrode film layer is thinned at least at one end adjacent to the negative electrode tab to form a negative electrode thinned part; the positive pole piece comprises a positive pole current collector and a positive pole film layer located on at least one side of the positive pole current collector, the positive pole film layer is at least thinned at one end adjacent to the negative pole lug so as to form a first positive pole thinned part, and the projection of the first positive pole thinned part and the projection of the negative pole thinned part in the third direction at least partially coincide. According to the technical scheme, the risk of lithium precipitation at the edge of the negative pole piece is reduced.

Description

[0001] This application claims the priority of PCT International Application PCT / CN2025 / 077649 titled "Battery Cell, Battery Device, and Electrical Device" filed on February 17, 2025, the entire content of which is incorporated herein by reference. Technical Field

[0002] This application relates to the technical field of batteries, and specifically relates to a battery cell, a battery device, and an electrical device. Background Art

[0003] In recent years, with the increasingly wide range of applications of batteries, batteries are widely used in energy storage power systems such as hydraulic, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0004] However, at present, there is a risk of lithium plating at the edges of the electrode sheets in the laminated structure battery, which limits the application of the battery. Summary of the Invention

[0005] This application is made in view of the above problems, and its purpose is to provide a battery cell, a battery device, and an electrical device, aiming to reduce the risk of lithium plating at the edges of the electrode sheets in the battery.

[0006] In a first aspect, this application provides a battery cell, the battery cell includes an electrode assembly, the electrode assembly includes a plurality of positive electrode sheets and a plurality of negative electrode sheets stacked in a third direction, and a positive electrode tab at the first side end and a negative electrode tab at the second side end in a second direction of the electrode assembly respectively; The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector. The negative electrode active material of the negative electrode film layer includes graphite. The negative electrode tab is electrically connected to the negative electrode current collector. The negative electrode film layer is thinned at least at one end adjacent to the negative electrode tab to form a negative electrode thinning portion; The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector; wherein, the positive electrode active material of the positive electrode film layer includes lithium-containing phosphate. The positive electrode tab is electrically connected to the positive electrode current collector. The positive electrode film layer is thinned at least at one end adjacent to the negative electrode tab to form a first positive electrode thinning portion, and at least a part of the projection of the first positive electrode thinning portion in the third direction coincides with the projection of the negative electrode thinning portion.

[0007] In the technical solution of this application, through the settings of the negative electrode thinning portion and the first positive electrode thinning portion, and through at least partial coincidence of the projection of the first positive electrode thinning portion in the third direction with the projection of the negative electrode thinning portion, it is beneficial to reduce the risk of lithium plating at the edges of the negative electrode sheet.

[0008] In any embodiment, in the direction away from the main body of the negative electrode film layer, the thickness of the negative electrode thinning portion is gradually decreased. Thereby, while reducing stress concentration, it is beneficial to reduce the edge buildup resulting in edge swelling.

[0009] In any embodiment, in the direction away from the main body of the positive electrode film layer, the thickness of the first positive electrode thinning portion is gradually decreased. Thereby, while reducing stress concentration, it is beneficial to reduce the edge buildup resulting in edge swelling.

[0010] In any embodiment, the minimum thickness of the first positive electrode thinning portion is less than the thickness of the main body of the positive electrode film layer, and the minimum thickness of the first positive electrode thinning portion is more than 85% of the thickness of the main body of the positive electrode film layer. Thereby, it is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab.

[0011] In any embodiment, the minimum thickness of the negative electrode thinning portion is less than the thickness of the main body of the negative electrode film layer, and the minimum thickness of the negative electrode thinning portion is more than 85% of the thickness of the main body of the negative electrode film layer. Thereby, it is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab.

[0012] In any embodiment, the size of the first positive electrode thinning portion in the second direction is 5 - 15 mm. Thereby, it is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab.

[0013] In any embodiment, the size of the negative electrode thinning portion in the second direction is 5 - 15 mm. Thereby, it is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab.

[0014] In any embodiment, one end of the positive electrode film layer adjacent to the positive electrode tab is thinned to form a second positive electrode thinning portion. Thereby, it is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab.

[0015] In any embodiment, in the direction away from the main body of the positive electrode film layer, the thickness of the second positive electrode thinning portion is gradually decreased. Thereby, while reducing stress concentration, it is beneficial to reduce the edge buildup resulting in edge swelling.

[0016] In any embodiment, the minimum thickness of the second positive electrode thinning portion is less than the thickness of the main body of the positive electrode film layer, and the minimum thickness of the second positive electrode thinning portion is more than 85% of the thickness of the main body of the positive electrode film layer. Thereby, it is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab.

[0017] In any embodiment, the size of the second positive electrode thinning portion in the second direction is 5 - 15 mm. Thereby, it is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab.

[0018] In any embodiment, the size of the battery cell in the first direction is 80 - 130 mm; the size of the battery cell in the second direction is 200 - 350 mm; the size of the battery cell in the third direction is 30 - 50 mm; the ratio of the size of the battery cell in the second direction to the size of the battery cell in the first direction is 1.5 - 4.4. Thus, it is beneficial to obtain a high energy density.

[0019] In any embodiment, the battery cell further includes a housing, a positive electrode connector, and a negative electrode connector. The housing includes a casing and a top cover covering one end port of the casing in the first direction. A positive electrode post and a negative electrode post are arranged on the top cover along the second direction, and the electrode assembly is arranged in the housing; The positive electrode connector includes a first main body portion and a first bent portion arranged at an angle. The first bent portion is provided with a first welding hole for the positive electrode post to pass through and be connected, and a first annular welding portion is formed between the first welding hole and the positive electrode post. The first main body portion is electrically connected to the positive electrode tab; the size of the first main body portion in the second direction is 1.5 - 3.0 mm, and the size of the first bent portion in the first direction is 1.5 - 3.0 mm; The negative electrode connector includes a second main body portion and a second bent portion arranged at an angle. The second bent portion is provided with a second welding hole for the negative electrode post to pass through and be connected, and a second annular welding portion is formed between the second welding hole and the negative electrode post; the second main body portion is electrically connected to the negative electrode tab; the size of the second main body portion in the second direction is 1.2 - 2.5 mm, and the size of the second bent portion in the first direction is 1.2 - 2.5 mm.

[0020] Thus, through the cooperation of the above sizes of the first main body portion and the first bent portion of the positive electrode connector, and the second main body portion and the second bent portion of the negative electrode connector, it is beneficial to improve the overcurrent capacity, thereby enhancing the reliability of stable passage of high current in a fast charging scenario.

[0021] In any embodiment, the sum of the size of the first main body portion in the first direction and the size of the first bent portion in the second direction is 50 mm - 90 mm. Thus, it is beneficial to optimize the electron transmission path, thereby reducing the internal resistance of the positive electrode connector.

[0022] In any embodiment, the sum of the size of the second main body portion in the first direction and the size of the second bent portion in the second direction is 50 mm - 90 mm. Thus, it is beneficial to optimize the electron transmission path, thereby reducing the internal resistance of the negative electrode connector.

[0023] In any embodiment, the size of the first main body portion in the first direction is 25% - 50% of the size of the battery cell in the first direction. Thus, it is beneficial to optimize the electron transmission path, thereby reducing the internal resistance of the positive electrode connector.

[0024] In any embodiment, the size of the second main body in the first direction is 25% to 50% of the size of the battery cell in the first direction. This is beneficial to optimize the electron transmission path, thereby reducing the internal resistance of the negative electrode connector.

[0025] In any embodiment, the size of the first main body in the third direction is smaller than the size of the battery cell in the third direction, and the absolute value of the difference between the size of the first main body in the third direction and the size of the battery cell in the third direction is 5 mm to 15 mm. This is conducive to effective contact between the positive electrode connector and the positive electrode tab.

[0026] In any embodiment, the size of the second main body in the third direction is smaller than the size of the battery cell in the third direction, and the absolute value of the difference between the size of the second main body in the third direction and the size of the battery cell in the third direction is 5 mm to 15 mm, thereby facilitating effective contact between the negative electrode connector and the positive electrode tab.

[0027] In any embodiment, at least one positive electrode tab is disposed on each positive electrode sheet, each positive electrode tab is disposed at a first side end of the positive electrode sheet in the second direction, and the size of the positive electrode tab in the first direction is 90% to 100% of the size of the positive electrode sheet in the first direction. This is conducive to increasing the contact area between the positive electrode tab and the positive electrode sheet, thereby reducing the resistance when current passes through.

[0028] In any embodiment, at least one negative electrode tab is disposed on each negative electrode plate, each negative electrode tab is disposed at the second side end of the negative electrode plate in the second direction, and the size of the negative electrode tab in the first direction is 90% to 100% of the size of the negative electrode plate in the first direction. This is conducive to increasing the contact area between the negative electrode tab and the positive electrode plate, thereby reducing the resistance when current passes through.

[0029] In any embodiment, the first bending portion includes a first welding section and a first connecting section, the first welding section is provided with a first welding hole, and the first connecting section connects the first welding section and the first main body; wherein the size of the first connecting section in the first direction is larger than the size of the first welding section in the first direction. The first welding section is relatively thin, which is conducive to improving the reliability of welding, and the first connecting section is relatively thick, which is conducive to ensuring the flow capacity.

[0030] In any embodiment, the size of the first connecting section in the first direction is 1.5-3.0 mm, which is beneficial to improve the reliability of stable passage of high current in fast charging scenarios.

[0031] In any embodiment, the size of the first welding section in the first direction is 1.0-2.5 mm, thereby facilitating both good welding stability and improved reliability of stable high current passage.

[0032] In any embodiment, on the side of the first bent portion facing away from the top cover, the first welding section is recessed relative to the first connecting section; the first welding section also includes an insulating sheet at least partially covering the surface of the first welding section, and the insulating sheet is arranged between the first welding section and the electrode assembly. The arrangement of the insulating sheet can prevent welding slag from falling into the gap between the electrode assemblies when welding the positive electrode column and the positive electrode connector.

[0033] In any embodiment, the second bent portion of the negative electrode connector includes a second welding section and a second connecting section, the second welding section is provided with a second welding hole, the second connecting section connects the second welding section and the second main body, wherein the size of the second connecting section in the first direction is greater than the size of the second welding section in the first direction. The second welding section is relatively thin, which is conducive to improving the reliability of welding, and the second connecting section is relatively thick, which is conducive to ensuring the flow capacity.

[0034] In any embodiment, the size of the second connecting section in the first direction is 1.2-2.5 mm, which is helpful to improve the reliability of stable passage of high current in fast charging scenarios.

[0035] In any embodiment, the size of the second welding section in the first direction is 1.0-2.0 mm, thereby facilitating both good welding stability and improved reliability of stable high current passage.

[0036] In any embodiment, on the side of the second bent portion facing away from the top cover, the second welding section is recessed relative to the second connecting section; the second welding section also includes an insulating sheet at least partially covering the surface of the second welding section, and the insulating sheet is arranged between the second welding section and the electrode assembly. The arrangement of the insulating sheet can prevent welding slag from falling into the gap between the electrode assemblies when the negative electrode column and the negative electrode connector are welded.

[0037] In any embodiment, the diameter of the positive electrode column is 9-22 mm, which is beneficial to improve the reliability of high current stable passage in fast charging scenarios.

[0038] In any embodiment, the diameter of the negative electrode column is 9-22 mm, which is beneficial to improve the reliability of high current stable passage in fast charging scenarios.

[0039] In any embodiment, the top cover includes a first edge and a second edge in the second direction, and the distance between the central axis of the positive electrode column and the first edge is 15-35 mm; the distance between the central axis of the negative electrode column and the second edge is 15-35 mm. The position setting of the positive electrode column and the negative electrode column is conducive to making the battery structure more reasonable and optimizing the electron transmission path.

[0040] In any embodiment, the positive electrode tab at least partially wraps the first main body portion. Thereby, it is beneficial to increase the contact area between the positive electrode tab and the positive electrode connector and reduce the internal resistance.

[0041] In any embodiment, the negative electrode tab at least partially wraps the second main body portion. Thereby, it is beneficial to increase the contact area between the negative electrode tab and the negative electrode connector and reduce the internal resistance.

[0042] In any embodiment, a heat insulation film layer is provided between the negative electrode tab and the negative electrode connector. Thereby, it is beneficial to isolate heat and improve the reliability of the battery.

[0043] In any embodiment, a heat insulation film layer is provided between the positive electrode tab and the positive electrode connector. Thereby, it is beneficial to isolate heat and improve the reliability of the battery.

[0044] In any embodiment, a heat insulation film layer is provided between the electrode assembly and the housing. Thereby, it is beneficial to isolate heat and improve the reliability of the battery.

[0045] In any embodiment, a heat insulation film layer is provided between the electrode assembly and the top cover. Thereby, it is beneficial to isolate heat and improve the reliability of the battery.

[0046] In any embodiment, the material of the heat insulation film layer includes at least one of polyimide and polyethylene terephthalate. The heat insulation film layer of the above materials is beneficial to isolate heat and improve the reliability of the battery.

[0047] In any embodiment, the thickness of the heat insulation film layer is 10 - 100 um. At this appropriate thickness, it is beneficial to reasonably utilize the battery space and is beneficial to isolate heat and improve the reliability of the battery.

[0048] In any embodiment, the size of the battery cell in the third direction is 30 - 50 mm. At this appropriate thickness, it is beneficial to reasonably utilize the battery space and exert the high energy density of the battery.

[0049] In any embodiment, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector. The negative electrode film layer includes a first film layer and a second film layer. The first film layer is provided on at least one surface of the negative electrode current collector, and the second film layer is provided on the surface of the first film layer facing away from the current collector; wherein, the first film layer contains a first negative electrode active material; the second film layer contains a second negative electrode active material; the average longest diameter of graphite in the second negative electrode active material is smaller than the average longest diameter of graphite in the first negative electrode active material.

[0050] Therefore, the average longest diameter of the graphite used in the second film layer is relatively smaller, and the ion transport distance of ions in the second film layer is relatively shorter, which is beneficial to further improving the fast charging performance of the battery cell. While the average longest diameter of the graphite used in the first film layer is relatively larger, and the tap density of the first film layer is relatively higher, which is beneficial to achieving good energy density.

[0051] In any implementation, the average longest diameter of the graphite in the first negative electrode active material is 7-18 μm. Therefore, it is beneficial to play the role of the relatively higher tap density of the first film layer.

[0052] In any implementation, the graphite in the first negative electrode active material includes at least one of artificial graphite and natural graphite.

[0053] In any implementation, the graphite in the first negative electrode active material includes graphite with a secondary particle morphology.

[0054] In any implementation, the volume distribution particle size Dv50 of the graphite in the first negative electrode active material is 7-15 μm.

[0055] In any implementation, the graphite in the first negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100-500 nm. The carbon coating layer is beneficial to improving the conductivity of the negative electrode active material.

[0056] In any implementation, the graphitization degree of the graphite in the first negative electrode active material is 90-94%.

[0057] In any implementation, the first negative electrode active material further includes a silicon material, and the mass ratio of silicon element in the silicon material in the first negative electrode active material is 0.5-10%. The addition of the silicon material is beneficial to further improving the energy density of the battery cell.

[0058] In any implementation, the average longest diameter of the graphite in the second negative electrode active material is 6-10 μm. Therefore, it is beneficial to play the role of the relatively shorter ion transport distance of ions in the second film layer.

[0059] In any implementation, the graphite in the second negative electrode active material includes at least one of artificial graphite and natural graphite.

[0060] In any implementation, the graphite in the second negative electrode active material includes graphite with a secondary particle morphology.

[0061] In any implementation, the volume distribution particle size Dv50 of the graphite in the second negative electrode active material is 7-15 μm.

[0062] In any embodiment, the graphite in the second negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100 to 500 nm. The carbon coating layer is beneficial to improving the conductivity of the negative electrode active material.

[0063] In any embodiment, the graphitization degree of the graphite in the second negative electrode active material is 90 to 94%.

[0064] In any embodiment, the second negative electrode active material further includes a silicon material, and the mass ratio of silicon element in the silicon material in the second negative electrode active material is 0.5 to 10%. The addition of the silicon material is beneficial to further improving the energy density of the battery cell. In any embodiment, the thickness of the first film layer is 30% to 70% of the total thickness of the negative electrode film layer. Thus, it is beneficial to play the role of the first film layer in taking into account the energy density of the battery cell.

[0065] In any embodiment, the thickness of the second film layer is 30% to 70% of the total thickness of the negative electrode film layer. Thus, it is beneficial to further improve the fast charging performance of the battery cell.

[0066] In any embodiment, under the condition that the state of charge SOC of the battery cell is 0%, the compaction density of the single-sided negative electrode film layer of the negative electrode plate is 1.3 to 1.52 g / cc. Thus, a suitable compaction density is beneficial to further adjusting the porosity of the negative electrode plate within a suitable range.

[0067] In any embodiment, the areal density of the single-sided negative electrode film layer of the negative electrode plate is 0.12 to 0.18 g / 1540.25 mm 2 . Thus, a suitable areal density is beneficial to further adjusting the porosity of the negative electrode plate within a suitable range.

[0068] In any embodiment, under the condition that the state of charge SOC of the battery cell is 0%, the compaction density of the single-sided positive electrode film layer of the positive electrode plate is 2.3 to 2.6 g / cc. Thus, a suitable compaction density is beneficial to further adjusting the porosity of the positive electrode plate within a suitable range.

[0069] In any embodiment, the areal density of the single-sided positive electrode film layer of the positive electrode plate is 0.25 to 0.33 g / 1540.25 mm 2 . Thus, a suitable areal density is beneficial to further adjusting the porosity of the positive electrode plate within a suitable range.

[0070] In any embodiment, the lithium-containing phosphate includes lithium iron phosphate, and the lithium iron phosphate includes metal elements, and the metal elements include at least one of aluminum, titanium, and vanadium. Adding the above metal elements to the lithium iron phosphate is beneficial to improving the compaction density of the positive electrode active material.

[0071] In any embodiment, the metal element includes aluminum, and the mass percentage of aluminum in the lithium-containing phosphate is 0.02% to 0.25%. Thus, it is beneficial to play the role of aluminum doping in improving the tap density of the cathode active material and further improving the cycle performance of the battery cell.

[0072] In any embodiment, the metal element includes titanium, and the mass percentage of the titanium in the lithium-containing phosphate is 0.15% to 0.35%. Thus, it is beneficial to play the role of titanium doping in improving the tap density of the cathode active material and further increasing the battery capacity.

[0073] In any embodiment, the metal element includes vanadium, and the mass percentage of the vanadium in the lithium-containing phosphate is 0.03% to 0.2%. Thus, it is beneficial to play the role of vanadium doping in improving the tap density of the cathode active material and further improving the charge and discharge performance of the battery cell.

[0074] In any embodiment, the lithium-containing phosphate includes lithium-containing phosphate with a primary particle morphology and lithium-containing phosphate with a secondary particle morphology. The mixed use of primary particles and secondary particles is beneficial to further adjust the tap density of the cathode active material.

[0075] In any embodiment, the average longest diameter of the lithium-containing phosphate with a primary particle morphology is 300 to 800 nm. Thus, it is beneficial to shorten the ion transport distance, thereby improving the fast charging performance.

[0076] In any embodiment, the average longest diameter of the lithium-containing phosphate with a secondary particle morphology is 8 μm to 15 μm. The secondary particles are usually composed of lithium-containing phosphate of primary particles with smaller particle sizes, which is beneficial to shorten the ion transport distance.

[0077] In any embodiment, the lithium-containing phosphate with a secondary particle morphology is spherical or quasi-spherical.

[0078] In any embodiment, the volume distribution particle size Dv50 of the lithium-containing phosphate is 5 to 15 μm.

[0079] In a second aspect, the present application provides a battery device, including the battery cell of the first aspect of the present application.

[0080] In a third aspect, the present application provides an electrical device, including the battery device of the second aspect of the present application. Description of the Drawings

[0081] Figure 1 It is a schematic structural diagram of a vehicle according to some embodiments of the present application; Figure 2 It is a schematic exploded view of a battery according to some embodiments of the present application; Figure 3Schematic structural diagram of a battery cell according to some embodiments of the present application; Figure 4 Cross-sectional schematic diagram of a positive electrode plate in a battery cell according to some embodiments of the present application; Figure 5 Cross-sectional schematic diagram of a negative electrode plate in a battery cell according to some embodiments of the present application; Figure 6 Exploded structural schematic diagram of a battery cell according to some embodiments of the present application; Figure 7 Front view of a positive electrode connector in a battery cell according to some embodiments of the present application; Figure 8 Front view of a negative electrode connector in a battery cell according to some embodiments of the present application; Figure 9 Top view of a positive electrode connector in a battery cell according to some embodiments of the present application; Figure 10 Top view of a negative electrode connector in a battery cell according to some embodiments of the present application; Figure 11 Front view of a positive electrode plate and a positive electrode tab in a battery cell according to some embodiments of the present application; Figure 12 Front view of a negative electrode plate and a negative electrode tab in a battery cell according to some embodiments of the present application; Figure 13 Front view of a top cover in a battery cell according to some embodiments of the present application.

[0082] Explanation of reference numerals: 1000, vehicle; 100, battery, 200, controller, 300, motor; 10, box body, 11, first part, 12, second part; 20, battery cell, 21, housing, 21a, shell, 21b, top cover, 21c, positive electrode post, 21d, negative electrode post, 22, electrode assembly, 22a, positive electrode plate, 22b, negative electrode plate, 22c, positive electrode tab, 22d, negative electrode tab, 23, positive electrode connector, 23a, first main body part, 23b, first bending part, 24, negative electrode connector, 24a, second main body part, 24b, second bending part, 25, insulating sheet; 22a1, positive electrode current collector, 22a2, positive electrode film layer, 22a3, first positive electrode thinning part, 22a4, second positive electrode thinning part, 22a5, main body of positive electrode film layer, 22b1, negative electrode current collector, 22b2, negative electrode film layer, 22b3, negative electrode thinning part, 22b4, main body of negative electrode film layer; 23b1, the first welding section, 23b2, the first connecting section, 23b3, the first welding hole, 24b1, the second welding section, 24b2, the second connecting section, 24b3, the second welding hole; H1, the dimension of the battery cell in the first direction, W1, the dimension of the battery cell in the second direction, T1, the dimension of the battery cell in the third direction; d1, the dimension of the first main body in the second direction, d2, the dimension of the first bending part in the first direction, d3, the dimension of the second main body in the second direction, d4, the dimension of the second bending part in the first direction, d5, the dimension of the first main body in the first direction, d6, the dimension of the first bending part in the second direction, d7, the dimension of the second main body in the first direction, d8, the dimension of the second bending part in the second direction, d9, the dimension of the first main body in the third direction, d10, the dimension of the second main body in the third direction, d11, the dimension of the positive electrode tab in the first direction, d12, the dimension of the negative electrode tab in the first direction, d13, the dimension of the first connecting section in the first direction, d14, the dimension of the first welding section in the first direction, d15, the dimension of the second connecting section in the first direction, d16, the dimension of the second welding section in the first direction, d17, the distance between the central axis of the positive electrode post and the first edge, d18, the distance between the central axis of the negative electrode post and the second edge; d20, the dimension of the first positive electrode thinning part in the second direction, d21, the dimension of the negative electrode thinning part in the second direction, d22, the dimension of the second positive electrode thinning part in the second direction. Detailed implementation mode

[0083] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically disclosed in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0084] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, 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, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0085] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0086] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0087] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0088] If there is no special instruction, the "including" and "comprising" mentioned in this application mean open-ended, and can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can only include or comprise the listed components.

[0089] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0090] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality of" means more than two, unless otherwise specifically defined.

[0091] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appearing at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0092] In the description of the embodiments of this application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0093] In the description of the embodiments of this application, the term "a plurality of" refers to more than two (including two). Similarly, "a plurality of groups" refers to more than two groups (including two groups), and "a plurality of pieces" refers to more than two pieces (including two pieces).

[0094] In the description of the embodiments of this application, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of this application and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of this application.

[0095] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "linkage", "fixation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0096] The battery cells disclosed in the embodiments of the present application can be used in electrical devices using batteries as power sources or various energy storage systems using batteries as energy storage elements. The electrical devices can be, but are not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, and the like. Among them, the electric toys can include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc., and the spacecraft can include airplanes, rockets, space shuttles, and spaceships, etc.

[0097] For the convenience of description in the following embodiments, a vehicle 1000, which is an electrical device in an embodiment of the present application, is taken as an example for illustration.

[0098] Please refer to Figure 1 , Figure 1 , which is a schematic structural diagram of the vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be disposed at the bottom, head, or tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000. For example, the battery 100 can be used as the operating power source of the vehicle 1000. The vehicle 1000 may further include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, for the working power requirements during the start, navigation, and driving of the vehicle 1000.

[0099] In some embodiments of the present application, the battery 100 can not only be used as the operating power source of the vehicle 1000, but also be used as the driving power source of the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0100] Please refer to Figure 2 , Figure 2An exploded view of the battery 100 provided by some embodiments of the present application. The battery 100 includes a box body 10 and battery cells 20, and the battery cells 20 are accommodated in the box body 10. Among them, the box body 10 is used to provide an accommodation space for the battery cells 20, and the box body 10 can adopt various structures. In some embodiments, the box body 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define an accommodation space for accommodating the battery cells 20. The second part 12 may be a hollow structure with one end open, and the first part 11 may be a plate-like structure. The first part 11 covers the open side of the second part 12 so that the first part 11 and the second part 12 jointly define an accommodation space; the first part 11 and the second part 12 may also both be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box body 10 formed by the first part 11 and the second part 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0101] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 can be connected in series, in parallel, or in a mixed connection. A mixed connection means that there are both series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed connection together, and then the whole formed by the multiple battery cells 20 is accommodated in the box body 10; of course, the battery 100 can also be that multiple battery cells 20 are first connected in series, in parallel, or in a mixed connection to form a battery module form, and then multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole and are accommodated in the box body 10. The battery 100 may further include other structures. For example, the battery 100 may further include a busbar component for realizing the electrical connection among the multiple battery cells 20.

[0102] Among them, each battery cell 20 can be a secondary battery or a primary battery. The battery cell 20 can be in the shape of a cylinder, a flat body, a cuboid, or other shapes, etc.

[0103] Some embodiments of the present application provide a battery cell 20. Refer to Figures 4 - 6 , the battery cell 20 includes an electrode assembly 22, the electrode assembly 22 includes a plurality of positive electrode plates 22a and a plurality of negative electrode plates 22b stacked in a third direction, and a positive electrode tab 22c located at the first side end and a negative electrode tab 22d located at the second side end in a second direction of the electrode assembly 22 respectively; The negative electrode plate 22b includes a negative electrode current collector 22b1 and a negative electrode film layer 22b2 located on at least one side of the negative electrode current collector 22b1. The negative electrode active material of the negative electrode film layer 22b2 includes graphite. The negative electrode tab 22d is electrically connected to the negative electrode current collector 22b1, and the negative electrode film layer 22b2 is thinned at least at one end adjacent to the negative electrode tab 22d to form a negative electrode thinning portion 22b3; The positive electrode plate 22a includes a positive electrode current collector 22a1 and a positive electrode film layer 22a2 located on at least one side of the positive electrode current collector 22a1; wherein, the positive electrode active material of the positive electrode film layer 22a2 includes a lithium-containing phosphate, the positive electrode tab 22c is electrically connected to the positive electrode current collector 22a1, and the positive electrode film layer 22a2 is thinned at least at one end adjacent to the negative electrode tab 22d to form a first positive electrode thinning portion 22a3, and the projection of the first positive electrode thinning portion 22a3 and the negative electrode thinning portion 22b3 in the third direction at least partially overlap.

[0104] Embodiments of the present application define three reference directions. As Figure 3 shown in the figure, the first direction in the figure is the height direction of the battery cell, the second direction is the width direction of the battery cell, and the third direction is the thickness direction of the battery cell.

[0105] In the embodiments of the present application, "being thinned" means a setting with a reduced thickness.

[0106] In the embodiments of the present application, refer to Figure 6 , at least one positive electrode tab 22c is provided on each positive electrode plate 22a, at least one negative electrode tab 22d is provided on each negative electrode plate 22b, and a plurality of positive electrode plates 22a and a plurality of negative electrode plates 22b are stacked so that each positive electrode tab 22c is located at the first side end of the electrode assembly 22 in the second direction, and each negative electrode tab 22d is located at the second side end of the electrode assembly 22 in the second direction, that is, the positive electrode tab 22c and the negative electrode tab 22d are respectively located at both side ends of the electrode assembly 22 in the second direction.

[0107] The electrode assembly 22 is a component in the battery cell where an electrochemical reaction occurs. The housing 21a may contain one or more electrode assemblies 22. The positive electrode tab 22c and the negative electrode tab 22d are respectively formed by the parts of the positive electrode plate 22a and the negative electrode plate 22b that do not have active substances. A separator is usually provided between the positive electrode plate 22a and the negative electrode plate 22b. During the charge and discharge process of the battery, the positive electrode active material and the negative electrode active material react with the electrolyte, and the positive electrode plate 22a is connected to the positive electrode terminal 21c through the positive electrode connection member 23, and the negative electrode plate 22b is connected to the negative electrode terminal 21d through the negative electrode connection member 24 to form a current loop.

[0108] In the technical solution of the present application, the positive electrode tab 22c and the negative electrode tab 22d are provided at both side ends of the electrode assembly 22 in the second direction, that is, the electrode tabs are led out from different sides, as Figure 6 . Refer to Figure 5 , through the setting of the negative electrode thinning portion 22b3, it is beneficial to reduce the risk of edge bulging and powder falling caused by the stacking of materials at the edge of the negative electrode film layer. However, in this case, the thickness of the positive electrode film layer opposite to the negative electrode thinning portion 22b3 is relatively thicker, and it is difficult for some lithium ions to be embedded in the graphite, increasing the risk of lithium deposition at the negative electrode thinning portion 22b3. Therefore, by usingFigure 4 A first positive electrode thinning portion 22a3 is provided at a position opposite to the negative electrode thinning portion 22b3. At this time, the projection of the first positive electrode thinning portion 22a3 and the negative electrode thinning portion 22b3 in the third direction at least partially overlap, which is beneficial to making the thickness of the negative electrode film layer near the negative electrode tab 22d match the thickness of the positive electrode film layer, thereby reducing the risk of lithium deposition at the edge of the negative electrode tab 22b.

[0109] In some embodiments, in the direction away from the main body 22b4 of the negative electrode film layer, the thickness of the negative electrode thinning portion 22b3 is gradually decreased. In the embodiments of the present application, the "direction away from the main body 22b4 of the negative electrode film layer" refers to the direction from the negative electrode current collector 22b1 to the negative electrode film layer. Thus, while reducing stress concentration, it is beneficial to reduce the edge swelling caused by edge stockpiling.

[0110] In some embodiments, in the direction away from the main body 22a5 of the positive electrode film layer, the thickness of the first positive electrode thinning portion 22a3 is gradually decreased. In the embodiments of the present application, the "direction away from the main body 22a5 of the positive electrode film layer" refers to the direction from the positive electrode current collector 22a1 to the positive electrode film layer. Thus, while reducing stress concentration, it is beneficial to reduce the edge swelling caused by edge stockpiling.

[0111] In some embodiments, the minimum thickness of the first positive electrode thinning portion 22a3 is less than the thickness of the main body 22a5 of the positive electrode film layer, and the minimum thickness of the first positive electrode thinning portion 22a3 is more than 85% of the thickness of the main body 22a5 of the positive electrode film layer. Thus, it is beneficial to further reduce the risk of lithium deposition at the edge of the negative electrode tab 22b. The minimum thickness of the first positive electrode thinning portion 22a3 can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or any numerical range composed of any two of the above values of the thickness of the main body 22a5 of the positive electrode film layer.

[0112] It should be noted that the positive electrode film layer can include one or more layers. When the positive electrode film layer is a multi-layer, the multi-layer positive electrode film layer can be regarded as a whole. The "thickness of the main body 22a5 of the positive electrode film layer" refers to the total thickness of the multi-layer positive electrode film layer's main body 22a5, and the "minimum thickness of the first positive electrode thinning portion 22a3" refers to the total thickness of the first positive electrode thinning portion 22a3 formed by the multi-layer positive electrode film layer.

[0113] In some embodiments, the minimum thickness of the negative electrode thinning portion 22b3 is less than the thickness of the main body 22b4 of the negative electrode film layer, and the minimum thickness of the negative electrode thinning portion 22b3 is more than 85% of the thickness of the main body 22b4 of the negative electrode film layer. Thus, it is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab 22b. The minimum thickness of the negative electrode thinning portion 22b3 can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% of the thickness of the main body 22b4 of the negative electrode film layer or any numerical interval composed of any two of the above numerical ranges.

[0114] It should be noted that the negative electrode film layer can include one or more layers. When the negative electrode film layer is multiple layers, the multiple negative electrode film layers can be regarded as a whole. The "thickness of the main body 22b4 of the negative electrode film layer" refers to the total thickness of the main body 22b4 of the multiple negative electrode film layers, and the "minimum thickness of the negative electrode thinning portion 22b3" refers to the total thickness of the negative electrode thinning portion 22b3 formed by the multiple negative electrode film layers.

[0115] In some embodiments, the dimension d20 of the first positive electrode thinning portion in the second direction is 5 - 15 mm. Thus, it is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab 22b. The dimension d20 of the first positive electrode thinning portion in the second direction can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm or any numerical interval composed of any two of the above numerical ranges.

[0116] In some embodiments, the dimension d21 of the negative electrode thinning portion in the second direction is 5 - 15 mm. Thus, it is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab 22b. The dimension d21 of the negative electrode thinning portion in the second direction can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm or any numerical interval composed of any two of the above numerical ranges.

[0117] In some embodiments, one end of the positive electrode film layer adjacent to the positive electrode tab 22c is thinned to form a second positive electrode thinning portion 22a4. It should be noted that here, a thinning portion may not be provided at the position on the negative electrode film layer that coincides with the projection of the second positive electrode thinning portion 22a4 in the third direction. The reason is that generally, when the thickness of the positive electrode film layer is relatively thicker, the situation of lithium plating on the negative electrode is more likely to occur. At this time, if a thinning portion is not provided on the negative electrode film layer opposite to the second positive electrode thinning portion 22a4, the negative electrode film layer in this part is relatively thicker. Thus, by providing the second positive electrode thinning portion 22a4, the positive electrode film layer in this area is made thinner relative to the negative electrode film layer it faces, which is beneficial to further reduce the risk of lithium plating at the edge of the negative electrode tab 22b.

[0118] In some embodiments, in the direction away from the main body 22a5 of the positive electrode film layer, the thickness of the second positive electrode thinning portion 22a4 is gradually decreased. Thereby, while reducing stress concentration, it is beneficial to reduce the edge swelling caused by edge stockpiling.

[0119] In some embodiments, the minimum thickness of the second positive electrode thinning portion 22a4 is less than the thickness of the main body 22a5 of the positive electrode film layer, and the minimum thickness of the second positive electrode thinning portion 22a4 is more than 85% of the thickness of the main body 22a5 of the positive electrode film layer. Thereby, it is beneficial to further reduce the risk of lithium deposition at the edge of the negative electrode tab 22b. The minimum thickness of the second positive electrode thinning portion 22a4 can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or any numerical interval composed of any two numerical ranges above of the thickness of the main body 22a5 of the positive electrode film layer.

[0120] In some embodiments, the dimension d22 of the second positive electrode thinning portion in the second direction is 5 - 15 mm. Thereby, it is beneficial to further reduce the risk of lithium deposition at the edge of the negative electrode tab 22b. The dimension d22 of the second positive electrode thinning portion in the second direction can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm or any numerical interval composed of any two numerical ranges above.

[0121] In some embodiments, referring to Figure 3 , the dimension H1 of the battery cell in the first direction is 80 - 130 mm; the dimension W1 of the battery cell in the second direction is 200 - 350 mm; the dimension T1 of the battery cell in the third direction is 30 - 50 mm; the ratio of the dimension of the battery cell in the second direction to the dimension of the battery cell in the first direction is 1.5 - 4.4. Thereby, it is beneficial to obtain a high energy density.

[0122] The dimension H1 (i.e., height) of the battery cell in the first direction can be 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, or a numerical interval composed of any two of the above numerical ranges. The dimension W1 (i.e., width) of the battery cell in the second direction can be 200 mm, 210 mm, 220 mm, 230 mm, 240 mm, 250 mm, 260 mm, 270 mm, 280 mm, 290 mm, 300 mm, 310 mm, 320 mm, 330 mm, 340 mm, 350 mm, or a numerical interval composed of any two of the above numerical ranges. The ratio of the dimension W1 of the battery cell in the second direction to the dimension H1 of the battery cell in the first direction can be 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, or a numerical interval composed of any two of the above numerical ranges. The dimension of the battery cell in the third direction can be 30 mm, 32 mm, 34 mm, 35 mm, 36 mm, 38 mm, 40 mm, 42 mm, 44 mm, 45 mm, 46 mm, 48 mm, 50 mm, or a numerical interval composed of any two of the above numerical ranges.

[0123] In some embodiments, referring to Figure 6 , the battery cell further includes a housing, a positive connection member, and a negative connection member. The housing includes a housing body and a top cover covering one end port of the housing body in the first direction. A positive electrode post and a negative electrode post are provided on the top cover along the second direction, and the electrode assembly is disposed in the housing; Referring to Figure 7 and Figure 9 , the positive connection member includes a first main body portion and a first bent portion disposed at an angle. The first bent portion is provided with a first welding hole for the positive electrode post to pass through and be connected, and a first annular welding portion is formed between the first welding hole and the positive electrode post. The first main body portion is electrically connected to the positive electrode tab; the dimension of the first main body portion in the second direction is 1.5 - 3.0 mm, and the dimension of the first bent portion in the first direction is 1.5 - 3.0 mm; The negative connection member includes a second main body portion and a second bent portion disposed at an angle. The second bent portion is provided with a second welding hole for the negative electrode post to pass through and be connected, and a second annular welding portion is formed between the second welding hole and the negative electrode post; the second main body portion is electrically connected to the negative electrode tab; the dimension of the second main body portion in the second direction is 1.2 - 2.5 mm, and the dimension of the second bent portion in the first direction is 1.2 - 2.5 mm.

[0124] In the embodiments of the present application, the dimension d1 of the first main body portion in the second direction can be understood as the thickness of the first main body portion 23a, and the dimension d2 of the first bending portion in the first direction can be understood as the thickness of the first bending portion 23b. It is positively correlated with the size of the overcurrent cross-section of the current.

[0125] In the embodiments of the present application, the first main body portion 23a and the first bending portion 23b "arranged at an angle" may refer to the angle formed to fit the edge shape of the electrode assembly 22. Similarly, the second main body portion 24a and the second bending portion 24b "arranged at an angle" may refer to the angle formed to fit the edge shape of the electrode assembly 22. This angle can be an acute angle, a right angle, or an obtuse angle.

[0126] In the embodiments of the present application, the dimension d2 of the first bending portion in the first direction refers to the maximum dimension of the first bending portion in the first direction, and the dimension d4 of the second bending portion in the first direction refers to the maximum dimension of the second bending portion in the first direction.

[0127] Exemplarily, the first annular welding portion formed between the first welding hole 23b3 and the positive electrode column 21c, and the second annular welding portion formed between the second welding hole 24b3 and the negative electrode column 21d can be formed by butt welding.

[0128] The dimension d1 (i.e., the thickness) of the first main body portion in the second direction can be 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm or a numerical interval composed of any two numerical ranges above. The dimension d2 (i.e., the thickness) of the first bending portion in the first direction can be 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm or a numerical interval composed of any two numerical ranges above.

[0129] The dimension d3 (i.e., the thickness) of the second main body portion in the second direction can be 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, or a numerical range formed by any two of the above values. The dimension d4 (i.e., the thickness) of the second bending portion in the first direction can be 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, or a numerical range formed by any two of the above values.

[0130] In the embodiment of the present application, the shape of the top cover 21b can be adapted to the shape of the housing 21a to cooperate with the housing 21a. Optionally, the top cover 21b can be made of a material with a certain hardness and strength (such as aluminum alloy). In this way, the top cover 21b is not easily deformed when being squeezed or collided, enabling the battery cell 20 to have higher structural strength. The positive electrode post and the negative electrode post are respectively electrically connected to the electrode assembly 22 through the positive electrode connector 23 and the negative electrode connector 24 for outputting or inputting the electrical energy of the battery cell 20. In some embodiments, a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold can also be provided on the top cover 21b. The housing 21a is a component for cooperating with the top cover 21b to form the internal environment of the battery cell 20, and the formed internal environment can be used to accommodate the electrode assembly 22, the electrolyte, and other components.

[0131] It can be understood that in the embodiment of the present application, the size of the electrode assembly 22 is close to the size of the battery cell 20, and there is a gap between the electrode assembly 22 and the inner wall of the battery cell 20, and this gap only needs to satisfy that the electrode assembly 22 can be put into and taken out along the inner wall of the battery cell 20.

[0132] Thus, through the cooperation of the above dimensions of the first main body portion of the positive electrode connector, the first bending portion, the second main body portion of the negative electrode connector, and the second bending portion, it is beneficial to improve the overcurrent capacity, thereby enhancing the reliability of high-current stable passing in the fast charging scenario.

[0133] In some embodiments, refer to Figure 7, the sum of the dimension d5 of the first main body portion in the first direction and the dimension d6 of the first bent portion in the second direction is 50 mm to 90 mm. The sum of the dimension d5 of the first main body portion in the first direction and the dimension d6 of the first bent portion in the second direction can be 50 mm, 51 mm, 52 mm, 53 mm, 54 mm, 55 mm, 56 mm, 57 mm, 58 mm, 59 mm, 60 mm, 61 mm, 62 mm, 63 mm, 64 mm, 65 mm, 66 mm, 67 mm, 68 mm, 69 mm, 70 mm, 71 mm, 72 mm, 73 mm, 74 mm, 75 mm, 76 mm, 77 mm, 78 mm, 79 mm, 80 mm, 81 mm, 82 mm, 83 mm, 84 mm, 85 mm, 86 mm, 87 mm, 88 mm, 89 mm, 90 mm or a numerical interval composed of any two numerical ranges above. Thus, it is beneficial to optimize the electron transmission path, thereby reducing the internal resistance of the positive electrode connector 23.

[0134] In some embodiments, referring to Figure 8 , the sum of the dimension d7 of the second main body portion in the first direction and the dimension d8 of the second bent portion in the second direction is 50 mm to 90 mm. The sum of the dimension d7 of the second main body portion in the first direction and the dimension d8 of the second bent portion in the second direction can be 50 mm, 51 mm, 52 mm, 53 mm, 54 mm, 55 mm, 56 mm, 57 mm, 58 mm, 59 mm, 60 mm, 61 mm, 62 mm, 63 mm, 64 mm, 65 mm, 66 mm, 67 mm, 68 mm, 69 mm, 70 mm, 71 mm, 72 mm, 73 mm, 74 mm, 75 mm, 76 mm, 77 mm, 78 mm, 79 mm, 80 mm, 81 mm, 82 mm, 83 mm, 84 mm, 85 mm, 86 mm, 87 mm, 88 mm, 89 mm, 90 mm or a numerical interval composed of any two numerical ranges above. Thus, it is beneficial to optimize the electron transmission path, thereby reducing the internal resistance of the negative electrode connector 24.

[0135] In some embodiments, the dimension d5 of the first main body portion in the first direction is 25% to 50% of the dimension H1 of the battery cell in the first direction. Thus, it is beneficial to optimize the electron transmission path, thereby reducing the internal resistance of the positive electrode connector 23. The dimension d5 of the first main body portion in the first direction can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% of the dimension of the electrode assembly 22 in the first direction or a numerical interval composed of any two numerical ranges above.

[0136] In some embodiments, the dimension d7 of the second main body portion in the first direction is 25% to 50% of the dimension H1 of the battery cell in the first direction. Thus, it is beneficial to optimize the electron transmission path, thereby reducing the internal resistance of the negative electrode connecting member 24. The dimension d7 of the second main body portion in the first direction can be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% of the dimension H1 of the battery cell in the first direction, or a numerical range composed of any two of the above values.

[0137] In some embodiments, referring to Figure 9 , the dimension d9 of the first main body portion in the third direction is less than the dimension T1 of the battery cell in the third direction, and the absolute value of the difference between the dimension d9 of the first main body portion in the third direction and the dimension T1 of the battery cell in the third direction is 5 mm to 15 mm. As an example, in the embodiments of the present application, the dimension d9 of the first main body portion in the third direction is the same as the dimension of the first bent portion in the third direction. Thus, it is beneficial to the effective contact between the positive electrode connecting member 23 and the positive electrode tab. The absolute value of the above difference can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, or a numerical range composed of any two of the above values.

[0138] In some embodiments, referring to Figure 10 , the dimension d10 of the second main body portion in the third direction is less than the dimension T1 of the battery cell in the third direction, and the absolute value of the difference between the dimension d10 of the second main body portion in the third direction and the dimension T1 of the battery cell in the third direction is 5 mm to 15 mm. As an example, in the embodiments of the present application, the dimension d9 of the first main body portion in the third direction is the same as the dimension of the first bent portion in the third direction. Thus, it is beneficial to the effective contact between the negative electrode connecting member 24 and the positive electrode tab. The absolute value of the above difference can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, or a numerical range composed of any two of the above values.

[0139] In some embodiments, referring to Figure 11, at least one positive electrode tab 22c is provided on each positive electrode plate 22a, and each positive electrode tab 22c is provided at the first side end of the positive electrode plate 22a in the second direction. The size d11 of the positive electrode tab in the first direction is 90% - 100% of the size of the positive electrode plate 22a in the first direction. Thus, it is beneficial to increase the contact area between the positive electrode tab and the positive electrode plate 22a, thereby reducing the resistance when current passes through. The size d11 of the positive electrode tab in the first direction can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100% of the size of the positive electrode plate 22a in the first direction, or a numerical interval composed of any two of the above numerical ranges.

[0140] In an embodiment of the present application, as an example, the shape of the positive electrode tab 22c can be square. At this time, the size d11 of the positive electrode tab in the first direction is the same. It can be understood that the shape of the positive electrode tab 22c can also be other existing feasible shapes, such as trapezoidal or other irregular shapes. At this time, the above-mentioned size d11 of the positive electrode tab in the first direction can refer to the size at the connection between the positive electrode plate 22a and the positive electrode tab 22c.

[0141] In some embodiments, referring to Figure 12 , at least one negative electrode tab 22d is provided on each negative electrode plate 22b, and each negative electrode tab 22d is provided at the second side end of the negative electrode plate 22b in the second direction. The size d12 of the negative electrode tab in the first direction is 90% - 100% of the size of the negative electrode plate 22b in the first direction. Thus, it is beneficial to increase the contact area between the negative electrode tab 22d and the positive electrode plate 22a, thereby reducing the resistance when current passes through. The size d12 of the negative electrode tab in the first direction can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100% of the size of the negative electrode plate 22b in the first direction, or a numerical interval composed of any two of the above numerical ranges.

[0142] In an embodiment of the present application, as an example, the shape of the negative electrode tab 22d can be square. At this time, the size d12 of the negative electrode tab in the first direction is the same. It can be understood that the shape of the negative electrode tab 22d can also be other existing feasible shapes, such as trapezoidal or other irregular shapes. At this time, the above-mentioned size d12 of the negative electrode tab in the first direction can refer to the size at the connection between the negative electrode plate 22b and the negative electrode tab 22d.

[0143] In some embodiments, continue to refer to Figure 7, the first bending portion 23b includes a first welding section 23b1 and a first connecting section 23b2. A first welding hole 23b3 is provided on the first welding section 23b1. The first connecting section 23b2 connects the first welding section 23b1 and the first main body portion 23a. Among them, the dimension d13 of the first connecting section in the first direction is greater than the dimension d14 of the first welding section in the first direction. The first bending portion is in a stepped shape. The first welding section 23b1 is relatively thin, which is beneficial to improving the welding reliability. The first connecting section 23b2 is relatively thick, which is beneficial to ensuring the current-carrying capacity.

[0144] In some embodiments, the dimension d13 of the first connecting section in the first direction is 1.5 - 3.0 mm. Thus, it is beneficial to improve the reliability of stable high-current passing in the fast charging scenario. The dimension d15 of the second connecting section in the first direction can be 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm or any numerical interval composed of any two of the above numerical ranges.

[0145] In some embodiments, the dimension d14 of the first welding section in the first direction is 1.0 - 2.5 mm. Thus, it is beneficial to balance the stability of good welding while improving the reliability of stable high-current passing. The dimension d14 of the first welding section in the first direction can be 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm or any numerical interval composed of any two of the above numerical ranges.

[0146] In some embodiments, referring to Figure 6 and Figure 7 , on the side of the first bending portion 23b facing away from the top cover 21b, the first welding section 23b1 is recessed relative to the first connecting section 23b2; the first welding section 23b1 further includes an insulating sheet 25 at least partially covering the surface of the first welding section 23b1, and the insulating sheet 25 is disposed between the first welding section 23b1 and the electrode assembly 22. It can be understood that the above-mentioned recessed part is disposed on the side facing away from the top cover 21b, which can enable the insulating sheet 25 to be disposed between the first welding section 23b1 and the electrode assembly 22. The setting of the insulating sheet 25 can prevent welding slag from falling into the gap between the electrode assemblies 22 when welding the positive electrode post 21c and the positive electrode connecting member 23.

[0147] In some embodiments, referring to Figure 8, the second bent portion 24b of the negative electrode connecting member 24 includes a second welding section 24b1 and a second connecting section 24b2. A second welding hole 24b3 is provided on the second welding section 24b1. The second connecting section 24b2 connects the second welding section 24b1 and the second main body portion 24a. Among them, the dimension d15 of the second connecting section in the first direction is greater than the dimension d16 of the second welding section in the first direction. The second bent portion is in a stepped shape. The second welding section 24b1 is relatively thin, which is beneficial to improving the welding reliability. The second connecting section 24b2 is relatively thick, which is beneficial to ensuring the current-carrying capacity.

[0148] In some embodiments, the dimension d15 of the second connecting section in the first direction is 1.2 - 2.5 mm. Thus, it is beneficial to improve the reliability of stable high-current passing in the fast charging scenario. The dimension d15 of the second connecting section in the first direction can be 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm or any numerical interval composed of any two of the above numerical ranges.

[0149] In some embodiments, the dimension d16 of the second welding section in the first direction is 1.0 - 2.0 mm. Thus, it is beneficial to improve the reliability of stable high-current passing while taking into account the good welding stability. The dimension d16 of the second welding section in the first direction can be 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm or any numerical interval composed of any two of the above numerical ranges.

[0150] In some embodiments, referring to Figure 6 and Figure 8 , on the side of the second bent portion facing away from the top cover 21b, the second welding section 24b1 is recessed relative to the second connecting section 24b2; the second welding section 24b1 further includes an insulating sheet 25 at least partially covering the surface of the second welding section 24b1. The insulating sheet 25 is disposed between the second welding section 24b1 and the electrode assembly 22. It can be understood that the above-mentioned recessed part is disposed on the side facing away from the top cover 21b, which can make the insulating sheet 25 be disposed between the second welding section 24b1 and the electrode assembly 22. The setting of the insulating sheet 25 can prevent welding slag from falling into the gap between the negative electrode posts 21d and the negative electrode connecting member 24 when welding the negative electrode post 21d and the negative electrode connecting member 24.

[0151] In some embodiments, the diameter of the positive electrode post 21c is 9 to 22 mm. Thus, it is beneficial to improve the reliability of stable passage of high current in a fast charging scenario. The diameter of the positive electrode post 21c can be 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, or a numerical range composed of any two of the above numerical values.

[0152] In some embodiments, the diameter of the negative electrode post 21d is 9 to 22 mm. Thus, it is beneficial to improve the reliability of stable passage of high current in a fast charging scenario. The diameter of the negative electrode post 21d can be 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, or a numerical range composed of any two of the above numerical values.

[0153] In some embodiments, referring to Figure 13 , the top cover 21b includes a first edge and a second edge in the second direction. The distance d17 between the central axis of the positive electrode post and the first edge is 15 - 35 mm; the distance d18 between the central axis of the negative electrode post and the second edge is 15 - 35 mm. The position settings of the positive electrode post 21c and the negative electrode post 21d are beneficial to make the battery structure more reasonable and optimize the electron transmission path. The distance d17 between the central axis of the positive electrode post and the first edge can be 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, or a numerical range composed of any two of the above numerical values. The distance d18 between the central axis of the negative electrode post and the second edge can be 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, or a numerical range composed of any two of the above numerical values.

[0154] In some embodiments, the positive electrode tab 22c at least partially wraps the first main body portion. Due to the presence of multiple layers of positive electrode tabs, the positive electrode tab 22c can be bent and partially or entirely wrapped around the first main body portion 23a. Thus, it is beneficial to increase the contact area between the positive electrode tab 22c and the positive electrode connecting member 23 and reduce the internal resistance. In some embodiments, the negative electrode tab 22d at least partially wraps the second main body portion. Similarly, due to the presence of multiple layers of negative electrode tabs 22d, the negative electrode tab 22d can be bent and partially or entirely wrapped around the second main body portion 24a. Thus, it is beneficial to increase the contact area between the negative electrode tab 22d and the negative electrode connecting member 24 and reduce the internal resistance.

[0155] In some embodiments, a heat insulation film layer is provided between the negative electrode tab 22d and the negative electrode connecting member 24. Thus, it is beneficial to isolate heat and improve the reliability of the battery.

[0156] In some embodiments, a heat insulation film layer is provided between the positive electrode tab 22c and the positive electrode connecting member 23. Thus, it is beneficial to isolate heat and improve the reliability of the battery.

[0157] In some embodiments, a heat insulation film layer is provided between the electrode assembly 22 and the housing 21a. Thus, it is beneficial to isolate heat and improve the reliability of the battery.

[0158] In some embodiments, a heat insulation film layer is provided between the electrode assembly 22 and the top cover 21b. Thus, it is beneficial to isolate heat and improve the reliability of the battery.

[0159] In some embodiments, the material of the heat insulation film layer includes at least one of polyimide and polyethylene terephthalate. The heat insulation film layer of the above materials is beneficial to isolate heat and improve the reliability of the battery.

[0160] In some embodiments, the thickness of the heat insulation film layer is 10 - 100 um. At this appropriate thickness, it is beneficial to reasonably utilize the battery space and is beneficial to isolate heat and improve the reliability of the battery. The thickness of the heat insulation film layer can be 10um, 20um, 30um, 40um, 50um, 60um, 70um, 80um, 90um, 100um or any numerical interval composed of any two of the above numerical ranges.

[0161] In some embodiments, the size T1 of the battery cell in the third direction is 30 - 50 mm. At this appropriate thickness, it is beneficial to reasonably utilize the battery space and exert the high energy density of the battery. The size T1 of the battery cell in the third direction can be 30mm, 32mm, 34mm, 35mm, 36mm, 38mm, 40mm, 42mm, 44mm, 45mm, 46mm, 48mm, 50mm or any numerical interval composed of any two of the above numerical ranges.

[0162] In some embodiments, the negative electrode tab 22b 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 first film layer and a second film layer. The first film layer is disposed on at least one surface of the negative current collector, and the second film layer is disposed on the surface of the first film layer facing away from the current collector. Wherein, the first film layer contains a first negative electrode active material; the second film layer contains a second negative electrode active material; the average longest diameter of graphite in the second negative electrode active material is smaller than the average longest diameter of graphite in the first negative electrode active material.

[0163] As used herein, the "average longest diameter" means that the electrode tab is ion-polished and cut along the thickness direction of the electrode tab to expose the cross-section of the film layer. The cross-section of the film layer can be tested by scanning electron microscopy (SEM). At a magnification of 1000 times in the SEM scenario, more than 50 particles are randomly selected, and the length of the longest straight line passing through the center point of the particle and extending to the outer periphery of the particle is measured for each single particle. Then, the average value of the longest straight line lengths of these particles is taken.

[0164] Thus, the average longest diameter of graphite used in the second film layer is relatively smaller, and the ion transport distance in the second film layer is relatively shorter, which is beneficial to further improving the fast charging performance of the battery cell. While the average longest diameter of graphite used in the first film layer is relatively larger, and the compaction density of the first film layer is relatively higher, which is beneficial to taking into account good energy density.

[0165] In some embodiments, the average longest diameter of graphite in the first negative electrode active material is 7 to 18 μm. Thus, it is beneficial to play the role of the relatively higher compaction density of the first film layer. The average longest diameter of graphite in the first negative electrode active material can be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or any numerical range composed of any two of the above values.

[0166] In some embodiments, the graphite in the first negative electrode active material includes at least one of artificial graphite and natural graphite.

[0167] In some embodiments, the graphite in the first negative electrode active material includes graphite with a secondary particle morphology.

[0168] In this application, the particles with a primary particle morphology refer to primary particles. A primary particle is the smallest unit of a particle within a certain observation range. There may be various forms of defects inside a primary particle, but no smaller particles can be defined within a primary particle. Primary particles may aggregate under physical forces such as van der Waals forces, but this aggregation can be easily depolymerized under external forces such as ultrasonic waves, stirring, and rolling, so that the main morphological form of the active material in the film layer remains primary particles.

[0169] In this application, the particles with a secondary particle morphology refer to secondary particles. Secondary particles are formed by the aggregation of primary particles and are not easily dispersed under external forces such as ultrasonic waves. However, after cutting the cross-section of the secondary particles, it can be seen that the secondary particles are formed by the aggregation of numerous primary particles.

[0170] In some embodiments, the volume distribution particle size Dv50 of the first negative electrode active material is 7 - 15 μm. The volume distribution particle size Dv50 of the first negative electrode active material can be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or any numerical range composed of any two of the above values.

[0171] In this application, the volume distribution particle size Dv50 of a material represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and it can be measured by known instruments and methods in the art. For example, it can be conveniently measured with a laser particle size analyzer by referring to GB / T19077 - 2016 Laser Diffraction Method for Particle Size Distribution. The test instrument can be the Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited, UK.

[0172] In some embodiments, the graphite in the first negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100 - 500 nm. The carbon coating layer is beneficial to improving the conductivity of graphite. The thickness of the carbon coating layer can be 100 nm, 150 nm, 200 nm, 350 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm or any numerical range composed of any two of the above values.

[0173] The thickness of the coating layer can be characterized by transmission electron microscopy (TEM) testing. Observe the negative electrode active material through transmission electron microscopy. According to the difference in lattice fringes, the coating layer coated on the surface of the negative electrode active material can be clearly observed. Randomly select 5 positions in the coating layer for testing, and calculate the average value as the average thickness of the coating layer.

[0174] In some embodiments, the graphitization degree of graphite in the first negative electrode active material is 90-94%. A high graphitization degree of the material indicates a small interlayer spacing of graphite, less lattice rotation, less disordered stacking of the layers, more ordered arrangement, a high specific capacity of the material, and is conducive to obtaining a battery cell with a high energy density. The graphitization degree of graphite in the first negative electrode active material can be 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94% or any numerical range composed of any two of the above values.

[0175] In this article, the term "graphitization degree" macroscopically characterizes what proportion of the material reaches a complete graphite crystal structure; microscopically, it refers to the degree to which carbon structures in different transitional states approach an ideal graphite crystal.

[0176] In this application, the graphitization degree of graphite can be tested using instruments and methods known in the art. For example, it can be tested using an X-ray diffractometer (such as Bruker D8 Discover). The test can refer to JISK 0131-1996 and JB / T4220-2011 to obtain the average interlayer spacing d002 of the C(002) crystal plane in the crystal structure of the material, and then the graphitization degree can be calculated according to the formula g=(0.344 - d002) / (0.344 - 0.3354)×100%. In the above formula, d002 is the average interlayer spacing of the C(002) crystal plane in the crystal structure of the material expressed in nanometers (nm).

[0177] In some embodiments, the first negative electrode active material further includes a silicon material, and the mass ratio of silicon element in the silicon material in the first negative electrode active material is 0.5-10%. The addition of the silicon material is conducive to further improving the energy density of the battery cell. The mass ratio of silicon element in the silicon material in the first negative electrode active material can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or any numerical range composed of any two of the above values.

[0178] In this application, the content of silicon element can be tested using instruments and methods known in the art. For example, the negative electrode active material can be placed in an appropriate digestion solvent, concentrated nitric acid solvent, and digested using the flat digestion method. Finally, it is dissolved and extracted with hydrochloric acid, and then the resulting solution is fixed to an appropriate volume and quantitatively tested using an inductively coupled plasma optical emission spectrometer ICP-OES.

[0179] In some embodiments, the average longest diameter particle size of graphite in the second negative electrode active material is 6 to 10 μm. Thus, it is beneficial to exert the effect that the ion transport distance in the second film layer is relatively shorter. The average longest diameter particle size of graphite in the second negative electrode active material can be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any numerical range composed of any two of the above values.

[0180] In some embodiments, the graphite in the second negative electrode active material includes at least one of artificial graphite and natural graphite.

[0181] In some embodiments, the graphite in the second negative electrode active material includes a negative electrode active material with a secondary particle morphology.

[0182] In some embodiments, the volume distribution particle size Dv50 of graphite in the second negative electrode active material is 7 to 15 μm. The volume distribution particle size Dv50 of graphite in the second negative electrode active material can be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or any numerical range composed of any two of the above values.

[0183] In some embodiments, the graphite in the second negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100 to 500 nm. The carbon coating layer is beneficial to improving the conductivity of the negative electrode active material. The thickness of the carbon coating layer can be 100 nm, 150 nm, 200 nm, 350 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm or any numerical range composed of any two of the above values.

[0184] In some embodiments, the graphitization degree of graphite in the second negative electrode active material is 90 to 94%. A high graphitization degree of the material indicates a small graphite layer spacing, less lattice rotation, less disordered stacking of the layers, orderly arrangement, a high specific capacity of the material, and is beneficial to obtaining a battery cell with a high energy density. The graphitization degree of graphite in the second negative electrode active material can be 90%, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94% or any numerical range composed of any two of the above values.

[0185] In some embodiments, the second negative electrode active material further includes a silicon material, and the mass percentage of silicon element in the silicon material in the second negative electrode active material is 0.5% to 10%. The addition of the silicon material is beneficial to further improving the energy density of the battery cell. The mass percentage of silicon element in the silicon material in the second negative electrode active material can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or any numerical range composed of any two of the above values.

[0186] In some embodiments, the thickness of the first film layer is 30% to 70% of the total thickness of the negative electrode film layer. Thus, it is beneficial to play the role of the first film layer in taking into account the energy density of the battery cell. The thickness of the first film layer can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% of the total thickness of the negative electrode film layer or any numerical range composed of any two of the above values.

[0187] In some embodiments, the thickness of the second film layer is 30% to 70% of the total thickness of the negative electrode film layer. Thus, it is beneficial to further improve the fast charging performance of the battery cell. The thickness of the second film layer can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% of the total thickness of the negative electrode film layer or any numerical range composed of any two of the above values.

[0188] The thicknesses of the first film layer and the second film layer can be characterized by transmission electron microscopy (TEM) testing. Observe the cross-section of the negative electrode sheet through transmission electron microscopy, and observe the thicknesses of the first film layer and the second film layer according to the difference in the average longest diameter particle size of the active materials in the first film layer and the second film layer. Take the average value after observing, for example, 5 times.

[0189] In some embodiments, under the condition that the state of charge (SOC) of the battery cell is 0%, the tap density of the single-sided negative electrode film layer of the negative electrode tab is 1.3 to 1.52 g / cc. Thus, a suitable tap density is beneficial to further adjust the porosity of the negative electrode tab within a suitable range. Under the condition that the state of charge (SOC) of the battery cell is 0%, the tap density of the single-sided negative electrode film layer of the negative electrode tab can be 1.3 g / cc, 1.31 g / cc, 1.32 g / cc, 1.33 g / cc, 1.34 g / cc, 1.35 g / cc, 1.36 g / cc, 1.37 g / cc, 1.38 g / cc, 1.39 g / cc, 1.4 g / cc, 1.41 g / cc, 1.42 g / cc, 1.43 g / cc, 1.44 g / cc, 1.45 g / cc, 1.46 g / cc, 1.47 g / cc, 1.48 g / cc, 1.49 g / cc, 1.5 g / cc, 1.51 g / cc, 1.52 g / cc or any numerical range composed of any two of the above values.

[0190] In the present application, the tap density of the electrode tab has the meaning well-known in the art and can be measured by methods known in the art. Under the condition that the state of charge (SOC) of the battery cell is 0%, the electrode tab is removed from the lithium-ion battery, and a certain area of the electrode tab is taken. The mass and thickness of the electrode tab and the current collector after removing the film layer are measured respectively. According to the following formula, the tap density of the electrode tab is calculated. Tap density of the electrode tab = (mass of the electrode tab - mass of the current collector) / [(thickness of the electrode tab - thickness of the current collector) × area of the electrode tab].

[0191] In some embodiments, the areal density of the single-sided negative electrode film layer of the negative electrode tab is 0.12 to 0.18 g / 1540.25 mm 2 . Thus, a suitable areal density is beneficial to further adjust the porosity of the negative electrode tab within a suitable range. The areal density of the single-sided negative electrode film layer of the negative electrode tab can be 0.12 g / 1540.25 mm 2 , 0.13 g / 1540.25 mm 2 , 0.14 g / 1540.25 mm 2 , 0.15 g / 1540.25 mm 2 , 0.16 g / 1540.25 mm 2 , 0.17 g / 1540.25 mm 2 , 0.18 g / 1540.25 mm 2 or any numerical range composed of any two of the above values.

[0192] In this application, the areal density of the film layer has the meaning well-known in the art and can be measured by methods known in the art. For example, take a single-sided coated and cold-pressed electrode sheet (if it is a double-sided coated electrode sheet, the film layer on one side can be wiped off), punch it into small round pieces with an area of S1, weigh it, and record it as M1. Then wipe off the film layer of the above-mentioned weighed electrode sheet and weigh the weight of the current collector, and record it as M0. The areal density of the single-sided film layer = (M1 - M0) / S1. To ensure the accuracy of the test results, multiple groups (for example, 10 groups) of samples to be tested can be tested, and the average value can be calculated as the test result.

[0193] In some embodiments, under the condition that the state of charge (SOC) of the battery cell is 0%, the tap density of the single-sided positive electrode film layer of the positive electrode sheet is 2.3 to 2.6 g / cc. Thus, a suitable tap density is beneficial to further adjust the porosity of the positive electrode sheet within a suitable range. Under the condition that the state of charge (SOC) of the battery cell is 0%, the tap density of the single-sided positive electrode film layer of the positive electrode sheet can be 2.3 g / cc, 2.31 g / cc, 2.32 g / cc, 2.33 g / cc, 2.34 g / cc, 2.35 g / cc, 2.36 g / cc, 2.37 g / cc, 2.38 g / cc, 2.39 g / cc, 2.4 g / cc, 2.41 g / cc, 2.42 g / cc, 2.43 g / cc, 2.44 g / cc, 2.45 g / cc, 2.46 g / cc, 2.47 g / cc, 2.48 g / cc, 2.49 g / cc, 2.5 g / cc, 2.51 g / cc, 2.52 g / cc, 2.53 g / cc, 2.54 g / cc, 2.55 g / cc, 2.56 g / cc, 2.57 g / cc, 2.58 g / cc, 2.59 g / cc, 2.6 g / cc or any numerical range composed of any two of the above values.

[0194] In some embodiments, the areal density of the single-sided positive electrode film layer of the positive electrode sheet is 0.25 to 0.33 g / 1540.25 mm 2 . Thus, a suitable areal density is beneficial to further adjust the porosity of the positive electrode sheet within a suitable range. The areal density of the single-sided positive electrode film layer of the positive electrode sheet can be 0.25 g / 1540.25 mm 2 , 0.26 g / 1540.25 mm 2 , 0.27 g / 1540.25 mm 2 , 0.28 g / 1540.25 mm 2 , 0.29 g / 1540.25 mm 2 , 0.3 g / 1540.25 mm 2 , 0.31 g / 1540.25 mm 2, 0.32 g / 1540.25 mm 2 , 0.33 g / 1540.25 mm 2 Or a numerical range composed of any two of the above values.

[0195] In some embodiments, the lithium-containing phosphate includes lithium iron phosphate, and the lithium iron phosphate includes metal elements, and the metal elements include at least one of aluminum, titanium, and vanadium. Adding the above metal elements to lithium iron phosphate is beneficial to improving the tap density of the cathode active material.

[0196] In the present application, the contents of aluminum, titanium, and vanadium in the lithium-containing phosphate can be tested by instruments and methods known in the art. For example, the lithium-containing phosphate can be placed in an appropriate digestion solvent, concentrated nitric acid solvent, and digested by the plate digestion method. Finally, it is dissolved with hydrochloric acid to extract the solvent, and then the obtained solution is fixed to an appropriate volume and quantitatively tested using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0197] In some embodiments, the metal element includes aluminum, and the mass ratio of aluminum in the lithium-containing phosphate is 0.02% - 0.25%. Thus, it is beneficial to play the role of aluminum doping in improving the tap density of the cathode active material and further improving the cycling performance of the battery monomer. The mass ratio of aluminum in the lithium-containing phosphate can be 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25% or a numerical range composed of any two of the above values.

[0198] In some embodiments, the metal element includes titanium, and the mass ratio of the titanium in the lithium-containing phosphate is 0.15% - 0.35%. Thus, it is beneficial to play the role of titanium doping in improving the tap density of the cathode active material and further increasing the battery capacity. The mass ratio of the titanium in the lithium-containing phosphate can be 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35% or a numerical range composed of any two of the above values.

[0199] In some embodiments, the metal element includes vanadium, and the mass ratio of vanadium in the lithium-containing phosphate is 0.03% to 0.2%. Thus, it is beneficial to play the role of vanadium doping in improving the tap density of the cathode active material and further improving the charge and discharge performance of the battery cell. The mass ratio of vanadium in the lithium-containing phosphate can be 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2% or a numerical range composed of any two of the above values.

[0200] In some embodiments, the lithium-containing phosphate includes lithium-containing phosphate with a primary particle morphology and lithium-containing phosphate with a secondary particle morphology. The mixed use of primary particles and secondary particles is beneficial to further adjust the tap density of the cathode active material.

[0201] In some embodiments, the average longest diameter of the lithium-containing phosphate with a primary particle morphology is 300 to 800 nm. Thus, it is beneficial to shorten the ion transport distance, thereby improving the fast charging performance. The average longest diameter of the lithium-containing phosphate with a primary particle morphology can be 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm or a numerical range composed of any two of the above values.

[0202] In some embodiments, the average longest diameter of the lithium-containing phosphate with a secondary particle morphology is 8 μm to 15 μm. The secondary particles are usually composed of lithium-containing phosphates of primary particles with smaller particle sizes, which is beneficial to shorten the ion transport distance. The average longest diameter of the lithium-containing phosphate with a secondary particle morphology can be 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm or a numerical range composed of any two of the above values.

[0203] In some embodiments, the lithium-containing phosphate with a secondary particle morphology is spherical or quasi-spherical. Spherical refers to a material with a sphericity of 1, and quasi-spherical refers to a material with a sphericity close to 1 but not 1.

[0204] In some embodiments, the volume - based particle size distribution Dv50 of the lithium - containing phosphate is 5 - 15 μm. The volume - based particle size distribution Dv50 of the lithium - containing phosphate can be 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm or any numerical range composed of any two of the above values.

[0205] The embodiment of the present application also provides a battery device, including the battery cell provided by the present application.

[0206] As the electrical device, the battery cell, battery module or battery pack can be selected according to its usage requirements.

[0207] The electrical device can be a pure - electric vehicle, a hybrid - electric vehicle, or a plug - in hybrid - electric vehicle, etc. In order to meet the high - power and high - energy - density requirements of the electrical device for the battery cell, a battery pack or a battery module can be used.

[0208] As another example of the device, it can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a battery cell can be used as the power source.

[0209] The embodiment of the present application also provides an electrical device, including the battery device provided by the present application.

[0210] Embodiment Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those embodiments where specific technologies or conditions are not indicated, the technologies or conditions described in the literature in the art or according to the product specifications are followed. For the reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0211] Embodiment 1 1. Preparation of the positive electrode plate The positive electrode plate includes a positive current collector and a positive electrode film layer. The positive electrode film layer is disposed on both sides of the positive current collector, and the positive current collector is aluminum foil.

[0212] The positive electrode film layer is formed by uniformly coating a positive electrode slurry (the solvent is N - methyl - 2 - pyrrolidone NMP) on the surface of the positive current collector, followed by drying and cold pressing. The positive electrode film layer includes a positive electrode active material, a binder polyvinylidene fluoride (PVDF), and a conductive agent acetylene black with a weight ratio of 90:5:5.

[0213] The positive electrode film layer is thinned at one end adjacent to the negative electrode tab to form a first positive electrode thinning portion. In the direction away from the main body of the positive electrode film layer, the thickness of the first positive electrode thinning portion gradually decreases. The minimum thickness of the first positive electrode thinning portion of the positive electrode film layer is 85% of the thickness of the main body of the positive electrode film layer. The size of the first positive electrode thinning portion in the second direction is 10 mm.

[0214] One end of the positive electrode film layer adjacent to the positive electrode tab is thinned to form a second positive electrode thinning portion. In the direction away from the main body of the positive electrode film layer, the thickness of the second positive electrode thinning portion gradually decreases. The minimum thickness of the second positive electrode thinning portion is 85% of the thickness of the main body of the positive electrode film layer. The size of the second positive electrode thinning portion in the second direction is 10 mm.

[0215] The positive electrode active material includes lithium iron phosphate particles and metal elements located in the lithium iron phosphate particles. The metal elements include Al, V, and Ti. Among them, the mass ratios of Al, V, and Ti in the lithium iron phosphate particles are all 0.15%.

[0216] The lithium iron phosphate particles include primary particles and secondary particles formed by the aggregation of primary particles. The secondary particles are spherical and quasi-spherical. The average longest diameter of the primary particles is 600 nm, and the average longest diameter of the secondary particles is 10 μm. The volume distribution particle size Dv50 of the lithium iron phosphate particles is 7 μm.

[0217] The areal density of the single-sided positive electrode film layer is 0.28 g / 1540.25 mm 2 。

[0218] Under the condition that the state of charge SOC of the battery cell is 0%, the compaction density of the single-sided positive electrode film layer of the positive electrode plate is 2.4 g / cc.

[0219] 2. Preparation of the negative electrode plate The negative electrode plate includes a negative electrode current collector and a negative electrode film layer. The negative electrode film layer is disposed on both sides of the negative electrode current collector, and the negative electrode current collector is a copper foil.

[0220] The negative electrode film layer includes a first film layer and a second film layer formed by uniformly coating a negative electrode slurry (the solvent is deionized water) on the surface of the negative electrode current collector and then drying and cold pressing.

[0221] The first film layer is disposed on the surface of the negative electrode current collector, and it includes a first negative electrode active material, acetylene black as a conductive agent, styrene-butadiene rubber as a negative electrode binder, and sodium carboxymethyl cellulose as a thickening agent with a mass ratio of 96.5:0.5:2:1. The negative electrode active material includes graphite and silicon oxide, and the mass percentage of silicon element in the first negative electrode active material is 5%. The graphite includes artificial graphite and a carbon coating layer, the carbon coating layer covers the surface of the artificial graphite, the thickness of the carbon coating layer is 200 nm, the graphitization degree of the graphite is 92%. The average longest diameter of the graphite is 12 μm.

[0222] The second film layer is disposed on the surface of the negative electrode current collector, and it includes a negative electrode active material, acetylene black as a conductive agent, styrene-butadiene rubber as a negative electrode binder, and sodium carboxymethyl cellulose as a thickening agent with a mass ratio of 96.5:0.5:2:1. The negative electrode active material includes graphite and silicon oxide, and the mass percentage of silicon element in the first negative electrode active material is 5%. The graphite includes artificial graphite and a carbon coating layer, the carbon coating layer covers the surface of the artificial graphite, the thickness of the carbon coating layer is 200 nm, the graphitization degree of the graphite is 92%. The average longest diameter of the graphite is 9 μm.

[0223] The thickness of the first film layer is 50% of the total thickness of the negative electrode film layer, and the thickness of the second film layer is 50% of the total thickness of the negative electrode film layer.

[0224] The negative electrode film layer is thinned at one end adjacent to the negative electrode tab to form a negative electrode thinning portion. In the direction away from the main body of the negative electrode film layer, the thickness of the negative electrode thinning portion gradually decreases. The projection of the first positive electrode thinning portion and the negative electrode thinning portion in the third direction at least partially overlap.

[0225] The minimum thickness of the negative electrode thinning portion in the negative electrode film layer is 85% of the thickness of the main body of the negative electrode film layer. The size of the negative electrode thinning portion in the second direction is 10 mm.

[0226] The areal density of the single-sided negative electrode film layer is 0.13 g / 1540.25 mm 2 。

[0227] Under the condition that the state of charge SOC of the battery cell is 0%, the tap density of the single-sided negative electrode film layer of the negative electrode plate is 1.4 g / cc.

[0228] 3. Separator The separator is a 7-μm polyethylene film layer.

[0229] 4. Preparation of electrolyte The electrolyte includes an organic solvent, a lithium salt, and an additive. After mixing the components of each organic solvent, the lithium salt and the additive are added to prepare the electrolyte. The organic solvent includes ethyl acrylate, dimethyl carbonate, and propylene carbonate. Based on the total mass of the electrolyte, the mass ratio of ethyl acrylate is 20%, the mass ratio of dimethyl carbonate is 20%, and the mass ratio of propylene carbonate is 40%. The lithium salt is lithium hexafluorophosphate. Based on the total mass of the electrolyte, the mass ratio of lithium hexafluorophosphate is 15%. The additive includes lithium difluorophosphate and vinylene carbonate. Based on the total mass of the electrolyte, the mass ratio of lithium difluorophosphate is 1%, and the mass ratio of vinylene carbonate is 4%.

[0230] 5. Preparation of Battery Cell Stack the above-mentioned positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, obtaining a stacked electrode assembly. Among them, multiple positive electrode sheets and multiple negative electrode sheets are stacked in the third direction, and the positive electrode tab and the negative electrode tab are respectively located at both ends in the second direction of the electrode assembly.

[0231] Place the electrode assembly in a housing. The housing includes a shell and a top cover covering one end port of the shell in the first direction. Positive and negative electrode posts are arranged on the top cover along the second direction. After baking, the electrolyte is injected, and through processes such as vacuum packaging, standing, forming, and shaping, a battery cell is obtained.

[0232] In this embodiment, the size H1 of the battery cell in the first direction is 100 mm; the size W1 of the battery cell in the second direction is 300 mm; the size T1 of the battery cell in the third direction is 50 mm.

[0233] The positive electrode connector includes a first main body portion and a first bending portion arranged at an angle. The first bending portion is provided with a first welding hole for the positive electrode post to pass through and connect, and a first annular welding portion is formed between the first welding hole and the positive electrode post. The first main body portion is electrically connected to the positive electrode tab; the size d1 of the first main body portion in the second direction is 2.5 mm, and the size d2 of the first bending portion in the first direction is 2.5 mm; Among them, the size of the first main body portion in the first direction is 25 mm, and the sum of the size of the first main body portion in the first direction and the size of the first bending portion in the second direction is 60 mm. The first bending portion includes a first welding section and a first connecting section. The first welding hole is arranged on the first welding section, and the size of the first connecting section in the first direction is 2.5 mm; the size of the first welding section in the first direction is 1.5 mm.

[0234] The negative electrode connecting member includes a second main body portion and a second bending portion arranged at an angle. The second bending portion is provided with a second welding hole for the negative electrode post to pass through and be connected, and a second annular welding portion is formed between the second welding hole and the negative electrode post; the second main body portion is electrically connected to the negative electrode tab; the dimension d3 of the second main body portion in the second direction is 2 mm, and the dimension d4 of the second bending portion in the first direction is 2 mm.

[0235] Wherein, the dimension of the second main body portion in the first direction is 25 mm, and the sum of the dimension of the second main body portion in the first direction and the dimension of the second bending portion in the second direction is 60 mm. The second bending portion includes a second welding section and a second connecting section. The second welding hole is provided on the second welding section, and the dimension of the second connecting section in the first direction is 2 mm; the dimension of the second welding section in the first direction is 1.0 mm.

[0236] The diameter of the positive electrode post is 15 mm, and the diameter of the negative electrode post is 15 mm.

[0237] In Example 2 and Comparative Example 1, the battery was prepared in a similar manner to Example 1. For the differences, please refer to Table 1.

[0238] Performance test: (1) Cycle performance test: At 25 °C, the battery cell was charged at a constant current of 1C to the charging cut-off voltage of 3.65V, and then charged at a constant current of 0.05C to the charging cut-off voltage of 3.65V, and left standing for 30 min; discharged at a constant current of 1C to 2.5V, and left standing for 30 min. This is one charge-discharge cycle. Repeat the above charge-discharge cycle steps until the cycle capacity retention rate (i.e., Cn / C0×100%) is 80%, and record the number of cycle turns.

[0239] Table 1

[0240] As can be seen from Examples 1-2 and Comparative Example 1, in Comparative Example 1, the minimum thickness of the first positive electrode thinning portion is 100% of the thickness of the positive electrode film layer, and there is a problem of lithium deposition, resulting in poor cycle performance. In Examples 1-2, the first positive electrode thinning portion is provided, and in the direction away from the main body of the positive electrode film layer, the thickness of the first positive electrode thinning portion is gradually decreased. The projection of the first positive electrode thinning portion and the negative electrode thinning portion in the third direction at least partially overlap, which is beneficial to improving the cycle performance of the battery. And as the proportion of the minimum thickness of the first positive electrode thinning portion decreases, the number of battery cycle turns increases.

[0241] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are only examples, and embodiments having the same composition and the same effect as the technical idea within the scope of the technical solution of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some of the constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A battery cell, characterized in that: The battery cell includes an electrode assembly, wherein the electrode assembly includes a plurality of positive electrode sheets and a plurality of negative electrode sheets stacked in a third direction, and a positive electrode tab and a negative electrode tab respectively located at a first side end and a second side end of the electrode assembly in a second direction; The negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector, the negative electrode active material of the negative electrode film layer comprises graphite, the negative electrode tab is electrically connected to the negative electrode current collector, and the negative electrode film layer is thinned at least at one end adjacent to the negative electrode tab to form a negative electrode thinning portion; The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector; wherein the positive electrode active material of the positive electrode film layer includes a lithium-containing phosphate, the positive electrode tab is electrically connected to the positive electrode current collector, and the positive electrode film layer is thinned at least at one end adjacent to the negative electrode tab to form a first positive electrode thinning portion, and the projections of the first positive electrode thinning portion and the negative electrode thinning portion in a third direction at least partially overlap.

2. The battery cell according to claim 1, characterized in that: In a direction away from the main body of the negative electrode film layer, the thickness of the negative electrode thinning portion is gradually reduced.

3. The battery cell according to claim 1 or 2, characterized in that: In a direction away from the main body of the positive electrode film layer, the thickness of the first positive electrode thinning portion is gradually reduced.

4. The battery cell according to claim 1, characterized in that: The minimum thickness of the first positive electrode thinned portion is less than the thickness of the main body of the positive electrode film layer, and the minimum thickness of the first positive electrode thinned portion is more than 85% of the thickness of the main body of the positive electrode film layer.

5. The battery cell according to claim 1, characterized in that: The minimum thickness of the negative electrode thinned portion is less than the thickness of the main body of the negative electrode film layer, and the minimum thickness of the negative electrode thinned portion is more than 85% of the thickness of the main body of the negative electrode film layer.

6. The battery cell according to claim 1, characterized in that: The size of the first positive electrode thinned portion in the second direction is 5-15 mm.

7. The battery cell according to claim 1, characterized in that: The size of the negative electrode thinned portion in the second direction is 5-15 mm.

8. The battery cell according to claim 1, characterized in that: The positive electrode film layer is thinned at one end adjacent to the positive electrode tab to form a second positive electrode thinning portion.

9. The battery cell according to claim 8, characterized in that: In a direction away from the main body of the positive electrode film layer, the thickness of the second positive electrode thinning portion is gradually reduced.

10. The battery cell according to claim 8 or 9, characterized in that: The minimum thickness of the second positive electrode thinned portion is less than the thickness of the main body of the positive electrode film layer, and the minimum thickness of the second positive electrode thinned portion is more than 85% of the thickness of the main body of the positive electrode film layer.

11. The battery cell according to claim 8, characterized in that: The size of the second positive electrode thinned portion in the second direction is 5-15 mm.

12. The battery cell according to claim 1, characterized in that: The size of the battery cell in the first direction is 80~130mm; the size of the battery cell in the second direction is 200~350mm; the size of the battery cell in the third direction is 30~50mm; the ratio of the size of the battery cell in the second direction to the size of the battery cell in the first direction is 1.5~4.

4.

13. The battery cell according to claim 1, characterized in that: The battery cell also includes a housing, a positive electrode connector and a negative electrode connector. The housing comprises a shell and a top cover covering a port of the shell in a first direction, a positive electrode column and a negative electrode column are arranged on the top cover along a second direction, and the electrode assembly is arranged in the shell; The positive electrode connector includes a first main body and a first bent portion arranged at an angle, the first bent portion is provided with a first welding hole for the positive electrode column to pass through and connect, and a first annular welding portion is formed between the first welding hole and the positive electrode column, and the first main body is electrically connected to the positive electrode tab; the size of the first main body in the second direction is 1.5-3.0 mm, and the size of the first bent portion in the first direction is 1.5-3.0 mm; The negative electrode connector includes a second main body and a second bent portion arranged at an angle, the second bent portion is provided with a second welding hole for the negative electrode column to pass through and connect, and a second annular welding portion is formed between the second welding hole and the negative electrode column; the second main body is electrically connected to the negative electrode tab; the size of the second main body in the second direction is 1.2~2.5mm, and the size of the second bent portion in the first direction is 1.2~2.5mm.

14. The battery cell according to claim 13, characterized in that: The sum of the size of the first main body in the first direction and the size of the first bending portion in the second direction is 50 mm to 90 mm.

15. The battery cell according to claim 13 or 14, characterized in that: The sum of the size of the second main body in the first direction and the size of the second bending portion in the second direction is 50 mm to 90 mm.

16. The battery cell according to claim 13, characterized in that: The size of the first main body in the first direction is 25% to 50% of the size of the battery cell in the first direction.

17. The battery cell according to claim 13, characterized in that: The size of the second main body in the first direction is 25% to 50% of the size of the battery cell in the first direction.

18. The battery cell according to claim 13, characterized in that: The size of the first main body in the third direction is smaller than the size of the battery cell in the third direction, and the absolute value of the difference between the size of the first main body in the third direction and the size of the battery cell in the third direction is 5 mm to 15 mm.

19. The battery cell according to claim 13, characterized in that: The size of the second main body in the third direction is smaller than the size of the battery cell in the third direction, and the absolute value of the difference between the size of the second main body in the third direction and the size of the battery cell in the third direction is 5 mm to 15 mm.

20. The battery cell according to claim 13, characterized in that: At least one positive electrode tab is disposed on each of the positive electrode plates, and each of the positive electrode tabs is disposed at a first side end of the positive electrode plate in the second direction, and a size of the positive electrode tab in the first direction is 90% to 100% of a size of the positive electrode plate in the first direction.

21. The battery cell according to claim 13, characterized in that: At least one negative electrode tab is disposed on each of the negative electrode plates, and each of the negative electrode tabs is disposed at a second side end of the negative electrode plate in the second direction, and a size of the negative electrode tab in the first direction is 90% to 100% of a size of the negative electrode plate in the first direction.

22. The battery cell according to claim 13, characterized in that: The first bending portion comprises: a first welding section, wherein a first welding hole is provided on the first welding section; and A first connecting section connects the first welding section and the first main body; wherein a size of the first connecting section in the first direction is larger than a size of the first welding section in the first direction.

23. The battery cell according to claim 22, characterized in that: The size of the first connecting section in the first direction is 1.5-3.0 mm.

24. The battery cell according to claim 22 or 23, characterized in that: The dimension of the first welding section in the first direction is 1.0-2.5 mm.

25. The battery cell according to claim 22, characterized in that: On the side of the first bending portion facing away from the top cover, the first welding section is recessed relative to the first connecting section; the first welding section also includes an insulating sheet that at least partially covers the surface of the first welding section, and the insulating sheet is arranged between the first welding section and the electrode assembly.

26. The battery cell according to claim 13, characterized in that: The second bent portion of the negative electrode connector comprises: A second welding section, wherein a second welding hole is provided on the second welding section; and A second connecting segment connects the second welding segment and the second main body; wherein a size of the second connecting segment in the first direction is larger than a size of the second welding segment in the first direction.

27. The battery cell according to claim 26, characterized in that: The size of the second connecting segment in the first direction is 1.2-2.5 mm.

28. The battery cell according to claim 26 or 27, characterized in that: The size of the second welding section in the first direction is 1.0-2.0 mm.

29. The battery cell according to claim 26, characterized in that: On the side of the second bending portion facing away from the top cover, the second welding section is recessed relative to the second connecting section; the second welding section also includes an insulating sheet that at least partially covers the surface of the second welding section, and the insulating sheet is arranged between the second welding section and the electrode assembly.

30. The battery cell according to claim 13, characterized in that The diameter of the positive electrode column is 9-22 mm.

31. The battery cell according to claim 13, characterized in that: The diameter of the negative electrode column is 9-22 mm.

32. The battery cell according to claim 13, characterized in that: The top cover includes a first edge and a second edge in a second direction, and the distance between the central axis of the positive electrode column and the first edge is 15-35 mm; the distance between the central axis of the negative electrode column and the second edge is 15-35 mm.

33. The battery cell according to claim 13, characterized in that: The positive electrode tab at least partially covers the first main body.

34. The battery cell according to claim 13, characterized in that: The negative electrode tab at least partially covers the second main body.

35. The battery cell according to claim 13, characterized in that A heat insulation film layer is arranged between the negative electrode tab and the negative electrode connector.

36. The battery cell according to claim 13, characterized in that: A heat insulation film layer is arranged between the positive electrode tab and the positive electrode connector.

37. The battery cell according to claim 13, characterized in that: A heat insulation film layer is arranged between the electrode assembly and the shell.

38. The battery cell according to claim 13, characterized in that: A heat insulation film layer is arranged between the electrode assembly and the top cover.

39. The battery cell according to claim 35, characterized in that The material of the thermal insulation film layer includes at least one of polyimide and polyethylene terephthalate.

40. The battery cell according to claim 35, characterized in that The thickness of the thermal insulation film layer is 10-100 um.

41. The battery cell according to claim 1, characterized in that The negative electrode film layer comprises a first film layer and a second film layer, wherein the first film layer is arranged on at least one surface of the negative electrode current collector, and the second film layer is arranged on a surface of the first film layer that is opposite to the current collector; The first film layer contains a first negative electrode active material; the second film layer contains a second negative electrode active material; the longest average particle size of graphite in the second negative electrode active material is smaller than the longest average particle size of graphite in the first negative electrode active material.

42. The battery cell according to claim 41, characterized in that The longest average particle size of graphite in the first negative electrode active material is 7-18 μm.

43. The battery cell according to claim 41 or 42, characterized in that: The graphite in the first negative electrode active material includes at least one of artificial graphite and natural graphite.

44. The battery cell according to claim 41, characterized in that The graphite in the first negative electrode active material includes graphite in a secondary particle morphology.

45. The battery cell according to claim 41, characterized in that The volume distribution particle size Dv50 of graphite in the first negative electrode active material is 7-15 μm.

46. ​​The battery cell according to claim 41, characterized in that The graphite in the first negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100-500 nm.

47. The battery cell according to claim 41, characterized in that The graphitization degree of the graphite in the first negative electrode active material is 90-94%.

48. The battery cell according to claim 41, characterized in that The first negative electrode active material further includes a silicon material, and the mass proportion of silicon element in the silicon material in the first negative electrode active material is 0.5-10%.

49. The battery cell according to claim 41, characterized in that The longest average particle size of graphite in the second negative electrode active material is 6-10 μm.

50. The battery cell according to claim 41, characterized in that The graphite in the second negative electrode active material includes at least one of artificial graphite and natural graphite.

51. The battery cell according to claim 41, characterized in that The graphite in the second negative electrode active material includes graphite in a secondary particle morphology.

52. The battery cell according to claim 41, characterized in that The volume distribution particle size Dv50 of graphite in the second negative electrode active material is 7-15 μm.

53. The battery cell according to claim 41, characterized in that The graphite in the second negative electrode active material includes a carbon coating layer, and the thickness of the carbon coating layer is 100-500 nm.

54. The battery cell according to claim 41, characterized in that The graphitization degree of the graphite in the second negative electrode active material is 90-94%.

55. The battery cell according to claim 41, characterized in that The second negative electrode active material further includes a silicon material, and the mass proportion of silicon element in the silicon material in the second negative electrode active material is 0.5-10%.

56. The battery cell according to claim 41, characterized in that The thickness of the first film layer is 30% to 70% of the total thickness of the negative electrode film layer.

57. The battery cell according to claim 41, characterized in that The thickness of the second film layer is 30% to 70% of the total thickness of the negative electrode film layer.

58. The battery cell according to claim 1, characterized in that When the state of charge (SOC) of the battery cell is 0%, the compaction density of the negative electrode film layer on a single side of the negative electrode plate is 1.3-1.52 g / cc.

59. The battery cell according to claim 1, characterized in that The surface density of the negative electrode film layer on a single side of the negative electrode plate is 0.12-0.18 g / 1540.25 mm 2 .

60. The battery cell according to claim 1, characterized in that When the state of charge (SOC) of the battery cell is 0%, the compaction density of the single-sided positive electrode film layer of the positive electrode sheet is 2.3-2.6 g / cc.

61. The battery cell according to claim 1, characterized in that The surface density of the single-sided positive electrode film layer of the positive electrode plate is 0.25-0.33 g / 1540.25 mm 2 .

62. The battery cell according to claim 1, characterized in that The lithium-containing phosphate includes lithium iron phosphate, the lithium iron phosphate includes a metal element, and the metal element includes at least one of aluminum, titanium, and vanadium.

63. The battery cell according to claim 62, characterized in that: The metal element includes aluminum, and the mass proportion of the aluminum in the lithium-containing phosphate is 0.02% to 0.25%.

64. The battery cell according to claim 62 or 63, characterized in that: The metal element includes titanium, and the mass proportion of the titanium in the lithium-containing phosphate is 0.15% to 0.35%.

65. The battery cell according to claim 62, characterized in that The metal element includes vanadium, and the mass proportion of the vanadium in the lithium-containing phosphate is 0.03% to 0.2%.

66. The battery cell according to claim 1, characterized in that The lithium-containing phosphate includes lithium-containing phosphate in the form of primary particles and lithium-containing phosphate in the form of secondary particles.

67. The battery cell according to claim 66, characterized in that The longest average particle size of the lithium-containing phosphate in the primary particle morphology is 300-800 nm.

68. The battery cell according to claim 66 or 67, characterized in that: The longest average particle size of the lithium-containing phosphate in the secondary particle morphology is 8 μm to 15 μm.

69. The battery cell according to claim 66, characterized in that The lithium-containing phosphate in the secondary particle morphology is spherical or quasi-spherical.

70. The battery cell according to claim 1, characterized in that The volume distribution particle size Dv50 of the lithium-containing phosphate is 5-15 μm.

71. A battery device, characterized in that: Comprising a battery cell as claimed in any one of claims 1 to 70.

72. An electrical device, characterized in that: Comprising a battery device as described in claim 71.

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