Electrode assemblies, battery cells, batteries and electrical equipment

Abstract

The present application provides an electrode assembly, a battery cell, a battery, an electrical device, and a manufacturing method and equipment for an electrode assembly, and relates to the field of battery technology. The electrode assembly includes a positive electrode sheet and a negative electrode sheet, and the electrode assembly includes a resting area and a non-resting area located on both sides of the center plane of its thickness; the negative electrode sheet includes a plurality of first negative electrode active material layers located in the resting area and a plurality of second negative electrode active material layers located in the non-resting area; the positive electrode sheet includes a plurality of first positive electrode active material layers located in the resting area and a plurality of second positive electrode active material layers located in the non-resting area; the active material capacity per unit area of ​​the first negative electrode active material layer is greater than the active material capacity per unit area of ​​the second negative electrode active material layer; and / or the active material capacity per unit area of ​​the first positive electrode active material layer is less than the active material capacity per unit area of ​​the second positive electrode active material layer, thereby effectively reducing the risk of lithium plating caused by the electrolyte being squeezed out when the resting area abuts against the shell.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an electrode assembly, a battery cell, a battery, an electrical device, and a method and equipment for manufacturing an electrode assembly. Background Art

[0002] With the rapid development of smartphones, tablets, and electric vehicles, lithium-ion batteries are increasingly being used, placing higher demands on them. While people prioritize battery safety, they also demand superior electrical performance. Lithium plating is one of the primary factors affecting both battery performance and safety. Once lithium plating occurs in a battery cell, it not only degrades its electrical performance but, as the amount of plating accumulates, it can easily form dendrites. These dendrites can potentially pierce the separator, causing a short circuit within the battery and posing a safety hazard.

[0003] Therefore, how to effectively avoid or reduce the risk of battery lithium plating has become a technical problem that needs to be solved urgently. Summary of the Invention

[0004] The embodiments of the present application provide an electrode assembly, a battery cell, a battery, an electrical device, and a method and equipment for manufacturing an electrode assembly to effectively reduce the risk of lithium plating in the battery.

[0005] In a first aspect, an embodiment of the present application provides an electrode assembly for being accommodated in a shell, wherein the electrode assembly includes a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet and the negative electrode sheet are stacked and wound around a winding axis; the electrode assembly includes abutment areas for abutting against the shell and a non-abutment area not abutting against the shell located on both sides of its thickness center plane, wherein the thickness center plane is perpendicular to the thickness direction of the electrode assembly and passes through the winding axis; the negative electrode sheet includes a plurality of first negative electrode active material layers located in the abutment areas and stacked along the thickness direction and a plurality of first negative electrode active material layers located in the non-abutment areas and A plurality of second negative electrode active material layers are stacked along the thickness direction; the positive electrode sheet includes a plurality of first positive electrode active material layers located in the abutment area and stacked along the thickness direction, and a plurality of second positive electrode active material layers located in the non-abutment area and stacked along the thickness direction; the active material capacity per unit area of ​​the first negative electrode active material layer is greater than the active material capacity per unit area of ​​the second negative electrode active material layer; and / or the active material capacity per unit area of ​​the first positive electrode active material layer is less than the active material capacity per unit area of ​​the second positive electrode active material layer.

[0006] In the above technical solution, if the lithium ions deintercalated from the positive electrode cannot enter the negative electrode, the lithium ions can only be deposited on the surface of the negative electrode, thereby forming a gray substance, i.e., lithium plating. When the active material capacity per unit area of ​​the second negative electrode active material layer in the non-abutting area that does not abut against the shell meets the design requirements, that is, the active material capacity per unit area of ​​the second negative electrode active material layer in the non-abutting area reaches the first preset value, so that the second negative electrode active material layer in the non-abutting area is not prone to lithium plating. When the active material capacity per unit area of ​​the first negative electrode active material layer located in the abutting area is greater than the active material capacity per unit area of ​​the second negative electrode active material layer located in the non-abutting area, that is, the active material capacity per unit area of ​​the first negative electrode active material layer is greater than the first preset value, it is equivalent to increasing the active material capacity per unit area of ​​the first negative electrode active material layer, then the first negative electrode active material layer can accept the lithium ions deintercalated from the first positive electrode active material layer, and the possibility of lithium plating in the first negative electrode active material layer in the abutting area is small, thereby effectively reducing the risk of lithium plating caused by the electrolyte being squeezed out when the abutting area abuts against the shell.

[0007] When the active material capacity per unit area of ​​the second positive electrode active material layer in the non-abutting area that does not abut against the shell meets the design requirements, that is, the active material capacity per unit area of ​​the second positive electrode active material layer in the non-abutting area reaches the second preset value, so that the second negative electrode active material layer in the non-abutting area is not prone to lithium plating. When the active material capacity per unit area of ​​the first positive electrode active material layer located in the abutting area is less than the active material capacity per unit area of ​​the second positive electrode active material layer located in the non-abutting area, that is, the active material capacity per unit area of ​​the first positive electrode active material layer is less than the second preset value, which is equivalent to reducing the active material capacity per unit area of ​​the first positive electrode active material layer, the first negative electrode active material layer can accept the lithium ions released from the first positive electrode active material layer, and the possibility of lithium plating in the first negative electrode in the abutting area is small, thereby effectively reducing the risk of lithium plating caused by the electrolyte being squeezed out when the abutting area abuts against the shell.

[0008] In some embodiments of the first aspect, the gram capacity of the active material of the first negative electrode active material layer is greater than the gram capacity of the active material of the second negative electrode active material layer; and / or, the gram capacity of the active material of the first positive electrode active material layer is less than the gram capacity of the active material of the second positive electrode active material layer.

[0009] In the above technical solution, by increasing the gram capacity of the active material of the first negative electrode active material layer in the abutment area, the active material capacity per unit area of ​​the first negative electrode active material layer in the abutment area can be increased, so that the capacity per unit area of ​​the first negative electrode active material layer in the abutment area is greater than the capacity per unit area of ​​the second negative electrode active material in the non-abutment area; and / or, by reducing the gram capacity of the active material of the first positive electrode active material layer in the abutment area, the active material capacity per unit area of ​​the first positive electrode active material layer in the abutment area can be reduced, so that the capacity per unit area of ​​the first positive electrode active material layer in the abutment area is less than the capacity per unit area of ​​the second positive electrode active material in the non-abutment area, which can effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out when the abutment area abuts against the shell.

[0010] In some embodiments of the first aspect, the ratio of the weight of the active material of the first negative electrode active material layer to the weight of the first negative electrode active material layer is greater than the ratio of the weight of the active material of the second negative electrode active material layer to the weight of the second negative electrode active material layer; and / or, the ratio of the weight of the active material of the first positive electrode active material layer to the weight of the first positive electrode active material layer is less than the ratio of the weight of the active material of the second positive electrode active material layer to the weight of the second positive electrode active material layer.

[0011] In the above technical solution, by increasing the active material in the first negative electrode active material layer in the abutment area, the weight ratio of the active material in the first negative electrode active material layer in the abutment area is increased, thereby increasing the active material capacity per unit area of ​​the first negative electrode active material layer in the abutment area; and / or by reducing the active material in the first positive electrode active material layer in the abutment area, the weight ratio of the active material in the first positive electrode active material layer in the abutment area is reduced, thereby reducing the active material capacity per unit area of ​​the first positive active material layer in the abutment area, which can effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out when the abutment area abuts against the shell.

[0012] In some embodiments of the first aspect, the active material capacity per unit area of ​​one of the two adjacent first negative electrode active material layers is greater than the active material capacity per unit area of ​​the other first negative electrode active material layer, and the other first negative electrode active material layer is closer to the thickness center plane than the one first negative electrode active material layer; and / or, the active material capacity per unit area of ​​one of the two adjacent first positive electrode active material layers is less than the active material capacity per unit area of ​​the other first positive electrode active material layer, and the other first positive electrode active material layer is closer to the thickness center plane than the one first positive electrode active material layer.

[0013] In the above technical solution, in the abutment area, the closer the first negative electrode active material layer or the first positive electrode active material layer is to the shell, the more severely it is squeezed, and the active material capacity per unit area of ​​the one of the two adjacent first negative electrode active material layers that is closer to the shell and farther away from the center plane of the thickness is greater than the active material capacity per unit area of ​​the other; and / or the active material capacity per unit area of ​​the one of the two adjacent first positive electrode active material layers that is closer to the shell and farther away from the center plane of the thickness is smaller than the active material capacity per unit area of ​​the other, which can further effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out when the abutment area abuts against the shell.

[0014] In some embodiments of the first aspect, the gram capacity of the active material of one of the two adjacent first negative electrode active material layers is greater than the gram capacity of the active material of the other first negative electrode active material layer, and the other first negative electrode active material layer is closer to the thickness center plane than the one first negative electrode active material layer; and / or, the gram capacity of the active material of the first positive electrode active material layer of one of the two adjacent first positive electrode active material layers is less than the gram capacity of the active material of the other first positive electrode active material layer, and the other first positive electrode active material layer is closer to the thickness center plane than the one first positive electrode active material layer.

[0015] In the above technical solution, by increasing the gram capacity of the active material of one of the two adjacent first negative electrode active material layers that is closer to the shell, the active material capacity per unit area of ​​the first negative electrode active material layer can be increased, so that the active material capacity per unit area of ​​the one of the two adjacent first negative electrode active material layers that is closer to the shell is greater than the active material capacity per unit area of ​​the other first negative electrode active material layer; and / or, by reducing the gram capacity of the active material of one of the two adjacent first positive electrode active material layers that is closer to the shell, the active material capacity per unit area of ​​the first positive electrode active material layer can be reduced, so that the active material capacity per unit area of ​​the one of the two adjacent first positive electrode active material layers that is closer to the shell is less than the active material capacity per unit area of ​​the other first positive electrode active material layer, which can further effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out when the abutment area abuts against the shell.

[0016] In some embodiments of the first aspect, the ratio of the weight of the active material of one of the two adjacent first negative electrode active material layers to the weight of the one first negative electrode active material layer is greater than the ratio of the weight of the active material of the other first negative electrode active material layer to the weight of the other first negative electrode active material layer, and the other first negative electrode active material layer is closer to the thickness center plane than the one first negative electrode active material layer; and / or, the ratio of the weight of the active material of one of the two adjacent first positive electrode active material layers to the weight of the one first positive electrode active material layer is less than the ratio of the weight of the active material of the other first positive electrode active material layer to the weight of the other first positive electrode active material layer, and the other first positive electrode active material layer is closer to the thickness center plane than the one first positive electrode active material layer.

[0017] In the above technical solution, by increasing the active material in one of the two adjacent first negative electrode active material layers that is closer to the shell, the weight ratio of the active material in the first negative electrode active material layer can be increased, thereby increasing the active material capacity per unit area of ​​the first negative electrode active material layer that is closer to the shell among the two adjacent first negative electrode active material layers; and / or by reducing the active material in one of the two adjacent first positive electrode active material layers that is closer to the shell, the weight ratio of the active material in the first positive electrode active material layer can be reduced, thereby reducing the active material capacity per unit area of ​​the first positive electrode active material layer that is closer to the shell among the two adjacent first negative electrode active material layers, which can effectively reduce the risk of lithium precipitation caused by the electrolyte being squeezed out at the position where the squeezing in the abutment area is more severe.

[0018] In some embodiments of the first aspect, the first negative electrode active material layer includes multiple negative electrode active segments, and the first positive electrode active material layer includes multiple positive electrode active segments; the active material capacity per unit area of ​​one negative electrode active segment of two adjacent negative electrode active segments is greater than the active material capacity per unit area of ​​the other negative electrode active segment, and the one negative electrode active segment is closer to the center of the first negative electrode active material layer than the other negative electrode active segment; and / or the active material capacity per unit area of ​​one segment of two adjacent positive electrode active segments is smaller than the active material capacity per unit area of ​​the other positive electrode active segment, and the one positive electrode active segment is closer to the center of the first positive electrode active material layer than the other positive electrode active segment.

[0019] In the above technical solution, the closer the first negative electrode active material layer and the first positive electrode active material layer are to their respective centers, the more severe the squeezing is. Therefore, the active material capacity per unit area of ​​one of the two adjacent negative electrode active sections that is closer to the center of the first negative electrode active material layer is greater than the active material capacity per unit area of ​​the other negative electrode active section, and / or the active material capacity per unit area of ​​one of the two adjacent positive electrode active sections that is closer to the center of the first positive electrode active material layer is smaller than the active material capacity per unit area of ​​the other positive electrode active section, which can further effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out when the abutting area abuts against the shell.

[0020] In some embodiments of the first aspect, the gram capacity of the active material in one of two adjacent negative electrode active segments is greater than the gram capacity of the active material in the other negative electrode active segment, and the one negative electrode active segment is closer to the center of the first negative electrode active material layer than the other negative electrode active segment; and / or, the gram capacity of the active material in one of two adjacent positive electrode active segments is less than the gram capacity of the active material in the other positive electrode active segment, and the one positive electrode active segment is closer to the center of the first positive electrode active material layer than the other positive electrode active segment.

[0021] In the above technical solution, by increasing the gram capacity of the active material of one of the two adjacent negative electrode active sections which is closer to the center of the first negative electrode active material layer, the active material capacity per unit area of ​​the negative electrode active section can be increased, so that the active material capacity per unit area of ​​one of the two adjacent negative electrode active sections which is closer to the center of the first negative electrode active material layer is greater than the active material capacity per unit area of ​​the other negative electrode active section; and / or, by reducing the gram capacity of the active material of one of the two adjacent positive electrode active sections which is closer to the center of the first positive electrode active material layer, the active material capacity per unit area of ​​the positive electrode active section can be reduced, so that the active material capacity per unit area of ​​one of the two adjacent positive electrode active sections which is closer to the center of the first positive electrode active material layer is greater than the active material capacity per unit area of ​​the other positive electrode active section, which can effectively reduce the risk of lithium precipitation caused by the electrolyte being squeezed out when the abutment area abuts against the shell.

[0022] In some embodiments of the first aspect, the ratio of the weight of the active material of one negative electrode active segment of two adjacent negative electrode active segments to the weight of the one negative electrode active segment is greater than the ratio of the weight of the active material of the other negative electrode active segment to the weight of the other negative electrode active segment, and the one negative electrode active segment is closer to the center of the first negative electrode active material layer than the other negative electrode active segment; and / or, the ratio of the weight of the active material of one positive electrode active segment of two adjacent positive electrode active segments to the weight of the one positive electrode active segment is less than the ratio of the weight of the active material of the other positive electrode active segment to the weight of the other positive electrode active segment, and the one positive electrode active segment is closer to the center of the first positive electrode active material layer than the other positive electrode active segment.

[0023] In the above technical solution, by increasing the active material in a negative electrode active section that is closer to the center of the first negative electrode active material layer among the two adjacent negative electrode active sections, the weight ratio of the active material in the negative electrode active section can be increased, thereby increasing the active material capacity per unit area of ​​the negative electrode active section; and / or by reducing the active material in a positive electrode active section that is closer to the center of the first positive electrode active material layer among the two adjacent positive electrode active sections, the weight ratio of the active material in the positive electrode active section can be reduced, thereby reducing the active material capacity per unit area of ​​the positive electrode active section, which can effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out when the abutment area abuts against the shell.

[0024] In some embodiments of the first aspect, each negative electrode active segment is strip-shaped, and the multiple negative electrode active segments are arranged along the direction of the winding axis; and / or each positive electrode active segment is strip-shaped, and the multiple positive electrode active segments are arranged along the direction of the winding axis.

[0025] In the above technical solution, the negative electrode active section and / or the positive electrode active section are in a strip shape, which facilitates coating of the negative electrode active material layer.

[0026] In some embodiments of the first aspect, the multiple negative electrode active segments include a central negative electrode active segment and at least one peripheral negative electrode active segment, each peripheral negative electrode active segment is annular and surrounds the central negative electrode active segment, and the central negative electrode active segment and the at least one peripheral negative electrode active segment are radially distributed from the center of the first negative electrode active material layer; and / or, the multiple positive electrode active segments include a central positive electrode active segment and at least one peripheral positive electrode active segment, each peripheral positive electrode active segment is annular and surrounds the central positive electrode active segment, and the central positive electrode active segment and the at least one peripheral positive electrode active segment are radially distributed from the center of the first positive electrode active material layer.

[0027] In the above technical solution, each negative electrode active segment is arranged in the center of the first negative electrode active material layer. Then, along any direction, the active material capacity per unit area of ​​the negative electrode active segment closer to the center of the two adjacent negative electrode active segments is greater than the active material capacity per unit area of ​​the other negative electrode active segment; and / or each positive electrode active segment is arranged in the center of the first positive electrode active material layer. Then, along any direction, the active material capacity per unit area of ​​the positive electrode active segment closer to the center of the two adjacent positive electrode active segments is less than the active material capacity per unit area of ​​the other positive electrode active segment, which can further reduce the risk of lithium deposition caused by the electrolyte being squeezed out at the position where the squeezing in the abutment area is more severe.

[0028] In some embodiments of the first aspect, the central negative electrode active section and / or the central positive electrode active section are elliptical.

[0029] In the above technical solution, the central negative electrode active section and / or the central positive electrode active section are elliptical, which can be closer to the expansion deformation state of the first negative electrode active material layer and the first positive electrode active material layer when the abutment area abuts against the shell, which is beneficial to reducing the risk of lithium plating caused by the electrolyte being squeezed out when the abutment area abuts against the shell.

[0030] In a second aspect, an embodiment of the present application provides a battery cell, comprising: a shell and an electrode assembly provided according to an embodiment of the first aspect, wherein the electrode assembly is accommodated in the shell, the abutting area is used to abut against the shell, and the non-abutting area is used not to abut against the shell.

[0031] In the above technical solution, the active material capacity per unit area of ​​the first negative electrode active material layer in the abutment area of ​​the electrode assembly is greater than the active material capacity per unit area of ​​the second negative electrode active material layer in the non-abutment area; and / or the active material capacity per unit area of ​​the first positive electrode active material layer in the abutment area of ​​the electrode assembly is less than the active material capacity per unit area of ​​the second positive electrode active material layer in the non-abutment area, which can effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out due to the abutment between the abutment area and the shell when the battery cell is working.

[0032] In some embodiments of the second aspect, the battery cell includes two electrode assemblies, the two electrode assemblies are arranged side by side along the thickness direction, and the abutting areas of the two electrode assemblies are arranged to face each other.

[0033] In the above technical solution, when the two electrode assemblies are arranged side by side in the thickness direction, there will inevitably be two areas that may abut against the inside of the shell. The abutting areas of the two electrode assemblies are set apart from each other, while the non-abutting areas of the two electrode assemblies are set close to each other. In this way, the abutting areas of the two electrode assemblies can abut against the shell, which can effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out due to the abutment of the abutting areas at both ends of the arrangement direction of the electrode assemblies against the shell when the battery cell is working.

[0034] In a third aspect, an embodiment of the present application provides a battery, comprising the battery cell provided by any embodiment of the second aspect.

[0035] In the above technical solution, the active material capacity per unit area of ​​the first negative electrode active material layer in the abutment area of ​​the electrode assembly is greater than the active material capacity per unit area of ​​the second negative electrode active material layer in the non-abutment area; and / or the active material capacity per unit area of ​​the first positive electrode active material layer in the abutment area of ​​the electrode assembly is less than the active material capacity per unit area of ​​the second positive electrode active material layer in the non-abutment area, which can effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out due to the abutment between the abutment area of ​​the electrode assembly and the shell when the battery is working.

[0036] In a fourth aspect, an embodiment of the present application provides an electrical device, comprising a battery cell provided by any embodiment of the second aspect.

[0037] In a fifth aspect, an embodiment of the present application provides a method for manufacturing an electrode assembly, comprising: providing a positive electrode sheet and a negative electrode sheet; stacking the negative electrode sheet and the positive electrode sheet and winding them around a winding axis to form a winding structure, so that the electrode assembly includes abutment areas for abutting against the shell and a non-abutment area that does not abut against the shell located on both sides of its thickness center plane, and the thickness center plane is perpendicular to the thickness direction of the electrode assembly and passes through the winding axis; wherein the negative electrode sheet includes a plurality of first negative electrode active material layers located in the abutment area and stacked along the thickness direction and a plurality of first negative electrode active material layers located in the non-abutment area. The positive electrode sheet includes a plurality of first positive electrode active material layers located in the abutting area and stacked along the thickness direction, and a plurality of second positive electrode active material layers located in the non-abutting area and stacked along the thickness direction; the active material capacity per unit area of ​​the first negative electrode active material layer is greater than the active material capacity per unit area of ​​the second negative electrode active material layer; and / or the active material capacity per unit area of ​​the first positive electrode active material layer is less than the active material capacity per unit area of ​​the second positive electrode active material layer.

[0038] In a sixth aspect, an embodiment of the present application provides an electrode assembly manufacturing device, comprising: a providing device for providing a positive electrode sheet and a negative electrode sheet; an assembling device for stacking the positive electrode sheet and the negative electrode sheet and winding them around a winding axis to form a winding structure, so that the electrode assembly includes abutment areas for abutting against the shell and non-abutment areas that do not abut against the shell located on both sides of its thickness center plane, and the thickness center plane is perpendicular to the thickness direction of the electrode assembly and passes through the winding axis; wherein the negative electrode sheet includes a plurality of first negative electrode active material layers and A plurality of second negative electrode active material layers are located in the non-abutment area and stacked along the thickness direction; the positive electrode sheet includes a plurality of first positive electrode active material layers located in the abutment area and stacked along the thickness direction and a plurality of second positive electrode active material layers located in the non-abutment area and stacked along the thickness direction; the active material capacity per unit area of ​​the first negative electrode active material layer is greater than the active material capacity per unit area of ​​the second negative electrode active material layer; and / or the active material capacity per unit area of ​​the first positive electrode active material layer is less than the active material capacity per unit area of ​​the second positive electrode active material layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 A schematic structural diagram of a vehicle provided in some embodiments of the present application;

[0041] Figure 2 A schematic diagram of the structure of a battery provided in some embodiments of the present application;

[0042] Figure 3 An exploded view of a battery cell provided in some embodiments of the present application;

[0043] Figure 4 A schematic structural diagram of an assembled battery cell provided in some embodiments of the present application;

[0044] Figure 5 for Figure 4 Middle P0-P0 sectional view;

[0045] Figure 6 A schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application;

[0046] Figure 7 for Figure 6P1-P1 sectional view;

[0047] Figure 8 Schematic diagram of the structure of electrode assemblies provided in other embodiments of the present application;

[0048] Figure 9 Schematic diagram of the structure of the electrode assembly provided in some other embodiments of the present application (the first negative electrode active material layer includes multiple negative electrode active segments);

[0049] Figure 10 A schematic structural diagram of the first negative electrode active material layer provided in some embodiments of the present application;

[0050] Figure 11 Schematic diagram of the structure of the first negative electrode active material layer provided in some other embodiments of the present application;

[0051] Figure 12 Schematic diagram of the structure of the first negative electrode active material layer provided in other embodiments of the present application;

[0052] Figure 13 A schematic structural diagram of a first negative electrode active material layer provided in some further embodiments of the present application;

[0053] Figure 14 Schematic diagram of the structure of the first negative electrode active material layer provided in some further embodiments of the present application (the central negative electrode active section is elliptical);

[0054] Figure 15 A schematic structural diagram of an electrode assembly provided in some further embodiments of the present application;

[0055] Figure 16 A schematic structural diagram of an electrode assembly provided in some other embodiments of the present application;

[0056] Figure 17 Schematic diagram of the structure of electrode assemblies provided in other embodiments of the present application;

[0057] Figure 18 A schematic structural diagram of an electrode assembly provided in some further embodiments of the present application (the first positive electrode active material layer includes a plurality of positive electrode active segments);

[0058] Figure 19 A schematic structural diagram of a first positive electrode active material layer provided in some embodiments of the present application;

[0059] Figure 20 Schematic diagram of the structure of the first positive electrode active material layer provided in some other embodiments of the present application;

[0060] Figure 21 Schematic diagram of the structure of the first positive electrode active material layer provided in some other embodiments of the present application;

[0061] Figure 22 A schematic structural diagram of a first positive electrode active material layer provided in some further embodiments of the present application;

[0062] Figure 23 Schematic diagram of the structure of the first positive electrode active material layer provided in some further embodiments of the present application (the central positive electrode active section is elliptical);

[0063] Figure 24 Schematic diagram of the structure of the electrode assembly provided in some other embodiments of the present application (the active material capacity per unit area of ​​the first positive electrode active material layer on both surfaces of the positive electrode current collector is different);

[0064] Figure 25 Schematic diagram of the structure of electrode assemblies provided in other embodiments of the present application (both the first negative electrode active material layer and the first positive electrode active material layer are improved);

[0065] Figure 26 A flow chart of a method for manufacturing an electrode assembly according to some embodiments of the present application;

[0066] Figure 27 A structural block diagram of the manufacturing equipment of the electrode assembly provided in some embodiments of the present application.

[0067] Marking instructions: 1000-vehicle; 100-battery; 10-housing; 11-first housing portion; 12-second housing portion; 20-battery cell; 21-housing; 211-side wall; 22-end cap assembly; 23-electrode assembly; 231-negative electrode sheet; 2311-negative electrode current collector; 2312-first negative electrode active material layer; 2312a-first negative electrode active section; 2312b-second negative electrode active section; 2312c-third negative electrode active section; 2312d-fourth negative electrode active section; 2312e-fifth negative electrode active section; 2 312f - sixth negative electrode active segment; 2312g - seventh negative electrode active segment; 2312h - central negative electrode active segment; 2312i - first peripheral negative electrode active segment; 2312j - second peripheral negative electrode active segment; 2312k - third peripheral negative electrode active segment; 2312m - inner negative electrode active material layer; 2312n - outer negative electrode active material layer; 2313 - second negative electrode active material layer; 232 - positive electrode sheet; 2321 - positive electrode current collector; 2322 - first positive electrode active material layer; 2322a - first positive electrode active segment; 2322b-second positive electrode active segment; 2322c-third positive electrode active segment; 2322d-fourth positive electrode active segment; 2322e-fifth positive electrode active segment; 2322f-sixth positive electrode active segment; 2322g-seventh positive electrode active segment; 2322h-central positive electrode active segment; 2322i-first peripheral positive electrode active segment; 2322j-second peripheral positive electrode active segment; 2322k-third peripheral positive electrode active segment; 2322m-inner positive electrode active material layer; 2322n-outer positive electrode active material layer; 232 3-second positive electrode active material layer; 233-diaphragm; X-thickness direction; Y-winding direction; Z-winding axis direction; A0-straight area; A1-bending area; B-thickness center plane; B1-rest area; B2-non-rest area; O1-center of the first negative electrode active material layer; O2-center plane of the first negative electrode active material layer; O3-center of the first positive electrode active material layer; O4-center plane of the first positive electrode active material layer; 200-controller; 300-motor; 400-electrode assembly manufacturing equipment; 410-providing device; 420-assembling device. DETAILED DESCRIPTION

[0068] The following detailed description of the embodiments of the present application is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present application, but are not intended to limit the scope of the present application, i.e., the present application is not limited to the described embodiments.

[0069] In the description of this application, it should be noted that, unless otherwise specified, "multiple" means more than two; the terms "upper", "lower", "left", "right", "inside", "outside", etc., indicating directions or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly perpendicular, but is within the allowable error range. "Parallel" is not strictly parallel, but is within the allowable error range.

[0070] The directional words appearing in the following description are all directions shown in the figures, and do not limit the specific structure of this application. In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0071] The term "plurality" used in this application refers to two or more (including two).

[0072] In this application, battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., and the embodiments of this application do not limit this. Battery cells may be cylindrical, flat, rectangular, or other shapes, etc., and the embodiments of this application do not limit this. Battery cells are generally divided into three types based on the packaging method: cylindrical battery cells, prismatic battery cells, and soft-pack battery cells, and the embodiments of this application do not limit this.

[0073] The battery referred to in the embodiments of this application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the battery referred to in this application may include a battery module or a battery pack. A battery generally includes a casing that encloses one or more battery cells. The casing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0074] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode sheet, a negative electrode sheet, and a separator. A battery cell primarily operates by the movement of metal ions between the positive and negative electrode sheets. The positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive electrode collector. The uncoated positive electrode collector protrudes from the coated positive electrode collector, and the uncoated positive electrode collector serves as the positive electrode tab. For lithium-ion batteries, for example, the positive electrode current collector can be made of aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The negative electrode sheet includes a negative current collector and a negative active material layer. The negative active material layer is coated on the surface of the negative electrode collector. The uncoated negative electrode collector protrudes from the coated negative electrode collector, and the uncoated negative electrode collector serves as the negative electrode tab. The negative electrode current collector can be made of copper, and the negative electrode active material can be carbon or silicon, among others. To ensure that high currents can pass without fusing, multiple positive electrode tabs are stacked together, and multiple negative electrode tabs are stacked together. The separator can be made of materials such as PP (polypropylene) or PE (polyethylene). Furthermore, the electrode assembly can be a wound or laminated structure, but the embodiments of the present application are not limited thereto.

[0075] The development of battery technology requires simultaneous consideration of multiple design factors, including performance parameters such as energy density, cycle life, discharge capacity, and charge / discharge rate. Furthermore, battery safety must be considered. Lithium plating is one of the primary factors affecting a battery's electrical and safety performance. Once it occurs, lithium plating not only degrades battery performance but also, as the amount of plating accumulates, dendrites form. These dendrites can potentially pierce the separator, causing a short circuit within the battery and posing a safety hazard. There are many reasons for lithium plating.

[0076] The inventors discovered that for a battery cell comprising multiple electrode assemblies arranged side by side along the thickness direction, one side of the two electrode assemblies located at both ends in the thickness direction will abut against the inner wall of the battery cell shell during thermal expansion. Under the constraint of the inner wall of the shell, the stress on the side where the electrode assembly abuts against the shell cannot be released, resulting in the electrolyte being squeezed out to a greater extent than the side where the electrode assembly does not abut against the shell. The side with a greater degree of electrolyte squeezing will have insufficient electrolyte infiltration, resulting in smaller gaps in the negative electrode sheet and increased diffusion resistance of lithium ions inside the negative electrode sheet, which in turn leads to lithium plating.

[0077] In view of this, an embodiment of the present application provides a technical solution, which effectively reduces the risk of lithium plating caused by the electrolyte being squeezed out when the abutting area abuts the shell by making the active material capacity per unit area of ​​the first negative electrode active material layer of the electrode assembly used to abut against the shell greater than the active material capacity per unit area of ​​the second negative electrode active material layer of the non-abutting area that does not abut against the shell, and / or making the active material capacity per unit area of ​​the first positive electrode active material layer of the abutting area smaller than the active material capacity per unit area of ​​the second positive electrode active material layer of the non-abutting area.

[0078] The technical solutions described in the embodiments of the present application are applicable to batteries and electrical devices using batteries.

[0079] Electrical equipment can be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and electric tools, etc. Vehicles can be fuel vehicles, gas vehicles, or new energy vehicles. New energy vehicles can be pure electric vehicles, hybrid vehicles, or extended-range vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical equipment.

[0080] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle 1000 as an example.

[0081] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of the present application. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head, or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 can also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, to meet the power requirements of the vehicle 1000 during startup, navigation, and driving.

[0082] In some embodiments of the present application, the battery 100 can not only serve as the operating power source of the vehicle 1000, but also serve 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.

[0083] like Figure 2As shown, battery 100 includes a housing 10 and battery cells 20. The battery cells 20 are housed within the housing 10, which provides a space for the battery cells 20. The housing 10 includes a first housing portion 11 and a second housing portion 12, which together define a space for accommodating the battery cells 20. In battery 100, there can be one or more battery cells 20. If there are multiple battery cells 20, the multiple battery cells 20 can be connected in series, in parallel, or in a hybrid configuration. A hybrid configuration refers to a combination of series and parallel connections within the multiple battery cells 20. Multiple battery cells 20 can be directly connected in series, in parallel, or in a hybrid configuration, and then the entire battery cell 20 is housed within the housing 10. Alternatively, multiple battery cells 20 can be first connected in series, in parallel, or in a hybrid configuration to form a battery module, which is then connected in series, in parallel, or in a hybrid configuration to form a single unit housed within the housing 10. The battery cells 20 can be cylindrical, flat, or have other shapes.

[0084] In some embodiments, the battery 100 may further include a busbar component (not shown in the figure), and the multiple battery cells 20 may be electrically connected via the busbar component to achieve series connection, parallel connection, or mixed connection of the multiple battery cells 20 .

[0085] Please refer to Figure 3 、 Figure 4 , Figure 3 FIG. 2 shows an exploded view of a battery cell 20 provided in some embodiments of the present application. Figure 4 The figure shows a schematic diagram of the structure of the battery cell 20 after assembly. The battery cell 20 includes a shell 21, an end cover assembly 22 and an electrode assembly 23. The shell 21 has an opening, the electrode assembly 23 is accommodated in the shell, and the end cover assembly 22 is used to seal the opening. The shell 21 can be in various shapes, such as cylindrical, flat, etc. The shape of the shell can be determined according to the specific shape of the electrode assembly 23. For example, if the electrode assembly 23 is a flat structure, the shell can be a rectangular parallelepiped structure. The material of the shell can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of the present application do not impose any special restrictions on this.

[0086] The battery cell 20 includes a plurality of electrode assemblies 23 . Figure 3 and Figure 4 The battery cell 20 is shown as an example, wherein the outer shell is a rectangular parallelepiped and the two electrode assemblies 23 are flat. Figure 3 In the embodiment, there are two electrode assemblies 23 , and along the thickness direction X of the electrode assemblies 23 , the two electrode assemblies 23 are arranged side by side.

[0087] like Figure 5As shown, the shell 21 has two side walls 211 arranged opposite to each other along the thickness direction X of the electrode assembly 23 . One of the two electrode assemblies 23 is arranged close to one side wall 211 , and the other electrode assembly 23 is arranged close to the other side wall 211 .

[0088] In some embodiments, the battery cell 20 further includes at least one battery cell, which is located between the two electrode assemblies 23 along the thickness direction X. The structure of the battery cell can be the same as that of the electrode assembly 23 provided in the embodiment of the present application, or can refer to existing battery cell designs, which will not be described in detail here.

[0089] In some embodiments, as Figure 6 、 Figure 7 As shown, the electrode assembly 23 includes a negative electrode sheet 231, a positive electrode sheet 232, and a separator 233. The positive electrode sheet 232, the negative electrode sheet 231, and the separator 233 are stacked and wound around a winding axis to form a wound electrode assembly 23.

[0090] The negative electrode sheet 231 includes a negative electrode current collector 2311, a first negative electrode active material layer 2312 coated on both surfaces of the negative electrode current collector 2311, and a second negative electrode active material layer 2313 coated on both surfaces of the negative electrode current collector 2311. There are multiple first negative electrode active material layers 2312 and multiple second negative electrode active material layers 2313. The first negative electrode active material layers 2312 and the second negative electrode active material layers 2313 are alternately arranged along the winding direction Y of the electrode assembly 23.

[0091] The positive electrode sheet 232 includes a positive electrode current collector 2321, a first positive electrode active material layer 2322 coated on both surfaces of the positive electrode current collector 2321, and a second positive electrode active material layer 2323 coated on both surfaces of the positive electrode current collector 2321. There are multiple first positive electrode active material layers 2322 and multiple second positive electrode active material layers 2323. The first positive electrode active material layers 2322 and the second positive electrode active material layers 2323 are alternately arranged along the winding direction Y of the electrode assembly 23.

[0092] Separator 233 is used to separate negative electrode 231 from positive electrode 232 to prevent short circuits. Separator 233 has numerous micropores that allow for the free passage of electrolyte ions and is highly permeable to lithium ions. Separator 233 can be made of materials such as polypropylene (PP) or polyethylene (PE).

[0093] The electrode assembly 23 has a straight region A0 and two curved regions A1, each connected to the ends of the straight region A0. The first negative electrode active material layer 2312, the first positive electrode active material layer 2322, the second negative electrode active material layer 2313, and the second positive electrode active material layer 2323 are all located in the straight region A0 and are stacked along the thickness direction X within the straight region A0.

[0094] The electrode assembly 23 includes two sides of the thickness center plane B for contacting with the shell 21 ( Figure 5 ) and the abutment area B1 that abuts against the housing 21 ( Figure 5 The electrode assembly 23 is located in the non-abutting region B2 (shown in FIG), where the thickness center plane B is perpendicular to the thickness direction X of the electrode assembly 23 and passes through the winding axis. All of the first negative electrode active material layers 2312 and all of the first positive electrode active material layers 2322 are located in the abutting region B1 and are stacked along the thickness direction X. All of the second negative electrode active material layers 2313 and all of the second positive electrode active material layers 2323 are located in the non-abutting region B2 and are stacked along the thickness direction X.

[0095] It can be understood that the two parts of the straight area A0 located on both sides of the thickness center plane B of the electrode assembly 23 are located in the abutment area B1 and the non-abutment area B2 respectively.

[0096] In some embodiments, if the active material capacities per unit area of ​​the first negative active material layer 2312 on both surfaces of any negative electrode current collector 2311 along the thickness direction X are the same, the active material capacities per unit area of ​​the first negative active material layer 2312 can represent the active material capacities per unit area of ​​the first negative active material layer 2312 on both surfaces of the negative electrode current collector 2311 of the corresponding layer. If the active material capacities per unit area of ​​the second negative active material layer 2313 on both surfaces of the negative electrode current collector 2311 of any layer are the same, the active material capacities per unit area of ​​the second negative active material layer 2313 can represent the active material capacities per unit area of ​​the second negative active material layer 2313 on both surfaces of the negative electrode current collector 2311 of the corresponding layer.

[0097] In some embodiments, see Figure 7 The active material capacity per unit area of ​​the first negative electrode active material layer 2312 is greater than the active material capacity per unit area of ​​the second negative electrode active material layer 2313 .

[0098] When the active material capacity per unit area of ​​the second negative electrode active material layer 2313 in the non-abutting area B2 that does not abut against the shell 21 meets the design requirements, that is, the active material capacity per unit area of ​​the second negative electrode active material layer 2313 in the non-abutting area B2 reaches the first preset value, the second negative electrode active material layer 2313 in the non-abutting area B2 is not prone to lithium deposition. When the active material capacity per unit area of ​​the first negative electrode active material layer 2312 located in the abutment area B1 is greater than the active material capacity per unit area of ​​the second negative electrode active material layer 2313 located in the non-abutment area B2, that is, the active material capacity per unit area of ​​the first negative electrode active material layer 2312 is greater than the first preset value, it is equivalent to increasing the active material capacity per unit area of ​​the first negative electrode active material layer 2312, then the first negative electrode active material layer 2312 can accept the lithium ions released from the first positive electrode active material layer 2322, and the possibility of lithium deposition in the first negative electrode active material layer 2312 in the abutment area B1 is small, thereby effectively reducing the risk of lithium deposition caused by the electrolyte being squeezed out when the abutment area B1 abuts against the shell 21.

[0099] It should be noted that the active material capacity per unit area of ​​the first negative electrode active material layer 2312 refers to the ratio of the active material capacity of the first negative electrode active material layer 2312 to the total area of ​​the first negative electrode active material layer 2312, and the active material capacity per unit area of ​​the second negative electrode active material layer 2313 refers to the ratio of the active material capacity of the second negative electrode active material layer 2313 to the total area of ​​the second negative electrode active material layer 2313. To further explain, if the active material capacity of the first negative electrode active material layer 2312 is Q1 and the area of ​​the first negative electrode active material layer 2312 is S1, then the capacity per unit area of ​​the first negative electrode active material layer 2312 is QS1 = Q1 / S1. If the active material capacity of the second negative electrode active material layer 2313 is Q2 and the area of ​​the second negative electrode active material layer 2313 is S2, then the capacity per unit area of ​​the second negative electrode active material layer 2313 is QS2 = Q2 / S2.

[0100] There are many factors that affect the active material capacity per unit area of ​​the first negative electrode active material layer 2312 and the active material capacity per unit area of ​​the second negative electrode active material layer 2313. Therefore, there are many ways to achieve that the active material capacity per unit area of ​​the first negative electrode active material layer 2312 is greater than the active material capacity per unit area of ​​the second negative electrode active material layer 2313.

[0101] In some embodiments, the gram capacity of the active material of the first negative electrode active material layer 2312 is greater than the gram capacity of the active material of the second negative electrode active material layer 2313 .

[0102] By increasing the gram capacity of the active material of the first negative electrode active material layer 2312 in the abutment area B1, the active material capacity per unit area of ​​the first negative electrode active material layer 2312 in the abutment area B1 can be increased, so that the capacity per unit area of ​​the first negative electrode active material layer 2312 in the abutment area B1 is greater than the capacity per unit area of ​​the second negative electrode active material layer 2313 in the non-abutment area B2, which can effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out when the abutment area B1 abuts against the shell 21.

[0103] Gram capacity refers to the ratio of the capacitance released by the active material within the battery 100 to the mass of the active material. Gram capacity is related to the active material in the first negative electrode active material layer 2312 and the active material in the second negative electrode active material layer 2313. For example, the active material in the first negative electrode active material layer 2312 is a silicon compound, while the active material in the second negative electrode active material layer 2313 is graphite. The silicon compound has a greater material activity than graphite, resulting in a greater lithium insertion capacity for the first negative electrode active material layer 2312 than for the second negative electrode active material layer 2313. This reduces the impact of electrolyte extrusion on the abutment area B1.

[0104] In other embodiments, the ratio of the weight of the active material of the first negative electrode active material layer 2312 to the weight of the first negative electrode active material layer 2312 is greater than the ratio of the weight of the active material of the second negative electrode active material layer 2313 to the weight of the second negative electrode active material layer 2313, so that the active material capacity per unit area of ​​the first negative electrode active material layer 2312 is greater than the active material capacity per unit area of ​​the second negative electrode active material layer 2313.

[0105] The first negative electrode active material layer 2312 and the second negative electrode active material layer 2313 both include active materials, binders and conductive agents. By increasing the active materials in the first negative electrode active material layer 2312 and increasing the proportion of active materials in the first negative electrode active material layer 2312, the active material capacity per unit area of ​​the first negative electrode active material layer 2312 is increased, so that the active material capacity per unit area of ​​the first negative electrode active material layer 2312 is greater than the active material capacity per unit area of ​​the second negative electrode active material layer 2313.

[0106] In some embodiments, the weight of the binder and the conductive agent in the first negative electrode active material layer 2312 can also be reduced to reduce the weight of the first negative electrode active material layer 2312, thereby increasing the proportion of active material in the first negative electrode active material layer 2312, which is equivalent to reducing the coating weight of the first negative electrode active material layer 2312. Not only can the ratio of the weight of the active material in the first negative electrode active material layer 2312 to the weight of the first negative electrode active material layer 2312 be greater than the ratio of the weight of the active material in the second negative electrode active material layer 2313 to the weight of the second negative electrode active material layer 2313, but the demand of the first negative electrode active material layer 2312 for electrolyte can also be reduced. The first negative electrode active material layer 2312 can be infiltrated with a smaller amount of electrolyte, which can reduce the influence of the first negative electrode active material layer 2312 being squeezed out by the electrolyte.

[0107] In the abutting area B1, along the thickness direction X, the closer to the shell 21 ( Figure 5 The more severe the degree of compression between the position (shown in FIG) and the shell 21 is.

[0108] Based on this, Figure 8 As shown, in some embodiments, along the thickness direction X, the active material capacity per unit area of ​​one of the two adjacent first negative electrode active material layers 2312 is greater than the active material capacity per unit area of ​​the other first negative electrode active material layer 2312, and the other first negative electrode active material layer 2312 is closer to the thickness center plane B than the one first negative electrode active material layer 2312. It can be understood that in the abutment area B1, along the thickness direction X, the farther the first negative electrode active material layer 2312 is from the thickness center plane B (the closer it is to the sidewall 211 of the housing 21), the greater the active material capacity per unit area, which can further effectively reduce the risk of lithium deposition caused by the electrolyte being squeezed out when the abutment area B1 abuts the housing 21.

[0109] Similarly, many methods can be used to ensure that the capacity per unit area of ​​the first negative electrode active material layer 2312 closer to the side wall 211 of the shell 21 is greater than the active material capacity per unit area of ​​the other second negative electrode active material layer 2313 .

[0110] In some embodiments, the gram capacity of the active material of one of two adjacent first negative electrode active material layers 2312 is greater than the gram capacity of the active material of the other first negative electrode active material layer 2312, and the other first negative electrode active material layer 2312 is closer to the thickness center plane B than the one first negative electrode active material layer 2312. It can be understood that in the abutting area B1, in the thickness direction X, the farther away from the thickness center plane B (the closer to the side wall 211 of the casing 21), the greater the gram capacity of the first negative electrode active material layer 2312.

[0111] The gram capacity is related to the active material in the first negative electrode active material layer 2312. For example, the active material of the first negative electrode active material layer 2312 that is closer to the side wall 211 of the shell 21 of the two adjacent first negative electrode active material layers 2312 is a silicon compound, and the active material of the other first negative electrode active material is graphite. The material activity of the silicon compound is greater than the material activity of the graphite, so that the lithium insertion ability of the first negative electrode active material layer 2312 that is closer to the side wall 211 of the shell 21 of the two adjacent first negative electrode active material layers 2312 is greater than the lithium insertion ability of the other first negative electrode active material layer 2312, which can further reduce the influence of the electrolyte extrusion on the abutment area B1.

[0112] In some embodiments, the ratio of the weight of the active material of one of the two adjacent first negative electrode active material layers 2312 to the weight of the first negative electrode active material layer 2312 is greater than the ratio of the weight of the active material of the other first negative electrode active material layer 2312 to the weight of the other first negative electrode active material layer 2312, and the other first negative electrode active material layer 2312 is closer to the thickness center plane B than the one first negative electrode active material layer 2312. It can be understood that, in the abutting area B1, in the thickness direction X, the farther from the thickness center plane B (the closer to the sidewall 211 of the casing 21), the greater the ratio of the weight of the active material of the first negative electrode active material layer 2312 to the weight of the first negative electrode active material layer 2312.

[0113] In some embodiments, by increasing the active material in one of the two adjacent first negative electrode active material layers 2312 that is closer to the side wall 211 of the shell 21, the proportion of active material in the first negative electrode active material layer 2312 is increased, thereby increasing the active material capacity per unit area of ​​the first negative electrode active material layer 2312, so that the active material capacity per unit area of ​​the first negative electrode active material layer 2312 close to the shell 21 is greater than the active material capacity per unit area of ​​the other first negative electrode active material layer 2312.

[0114] In some embodiments, the weight of the binder and the conductive agent in the first negative electrode active material layer 2312 closer to the shell 21 can also be reduced to reduce the weight of the first negative electrode active material layer 2312 closer to the shell 21, thereby increasing the proportion of active material in the first negative electrode active material layer 2312, which is equivalent to reducing the coating weight of the first negative electrode active material layer 2312 closer to the shell 21 among the two adjacent first negative electrode active material layers 2312. This not only makes the ratio of the weight of the active material in the first negative electrode active material layer 2312 to the weight of the first negative electrode active material layer 2312 greater than the ratio of the weight of the active material in the other second negative electrode active material layer 2313 to the weight of the other second negative electrode active material layer 2313, but also reduces the demand for electrolyte by the first negative electrode active material layer 2312 closer to the shell 21. The first negative electrode active material layer 2312 can be infiltrated with a smaller amount of electrolyte, which can reduce the impact of electrolyte extrusion on the first negative electrode active material layer 2312.

[0115] For each first negative electrode active material layer 2312 , when the electrode assembly 23 expands, the closer to the center O1 of the first negative electrode active material layer, the greater the squeezing force, and the greater the degree to which the electrolyte is squeezed out.

[0116] Based on this, in some embodiments, such as Figure 9 As shown, the first negative electrode active material layer 2312 includes multiple negative electrode active segments. The active material capacity per unit area of ​​one of two adjacent negative electrode active segments is greater than the active material capacity per unit area of ​​the other negative electrode active segment, and the one negative electrode active segment is closer to the center O1 of the first negative electrode active material layer than the other negative electrode active segment. It can be understood that, in the abutment area B1, the closer the negative electrode active segment is to the center O1 of the first negative electrode active material layer, the greater the active material capacity per unit area. By dividing the first negative electrode active material layer 2312 into multiple negative electrode active segments, and by increasing the active material capacity per unit area of ​​the negative electrode active segment closer to the center O1 of the first negative electrode active material layer, the area near the center O1 of the first negative electrode active material layer is less affected by electrolyte extrusion, further effectively reducing the risk of lithium deposition caused by electrolyte extrusion when the abutment area B1 abuts the housing 21.

[0117] In some embodiments, the gram capacity of the active material in one of two adjacent negative electrode active segments is greater than the gram capacity of the active material in the other negative electrode active segment, and the one negative electrode active segment is closer to the center O1 of the first negative electrode active material layer than the other negative electrode active segment, so that the active material capacity per unit area closer to the first negative electrode active material layer 2312 is greater than the active material capacity per unit area of ​​the other first negative electrode active material layer 2312.

[0118] In some embodiments, the ratio of the weight of the active material of one negative electrode active segment of two adjacent negative electrode active segments to the weight of the one negative electrode active segment is greater than the ratio of the weight of the active material of the other negative electrode active segment to the weight of the other negative electrode active segment, and the one negative electrode active segment is closer to the center O1 of the first negative electrode active material layer than the other negative electrode active segment.

[0119] In some embodiments, by increasing the active material in one of the two adjacent negative electrode active sections close to the shell 21, the proportion of active material in the negative electrode active section is increased, thereby increasing the active material capacity per unit area of ​​the negative electrode active section, so that the active material capacity per unit area of ​​the negative electrode active section closer to the center O1 of the first negative electrode active material layer among the two adjacent negative electrode active sections is greater than the active material capacity per unit area of ​​the other negative electrode active section.

[0120] In some embodiments, the weight of the adhesive and the conductive agent of the negative electrode active segment near the center of the first negative electrode active material layer 2312 can also be reduced to reduce the weight of the negative electrode active segment, thereby increasing the proportion of active material in the first negative electrode active material layer 2312, which is equivalent to reducing the coating weight of a negative electrode active segment near the center of the two adjacent negative electrode active segments. Not only can the ratio of the weight of the active material in the negative electrode active segment to the weight of the negative electrode active segment be greater than the ratio of the weight of the active material in the other negative electrode active segment to the weight of the other negative electrode active segment, but the demand for electrolyte in the negative electrode active segment near the center O1 of the first negative electrode active material layer can also be reduced. The negative electrode active segment can be infiltrated with a smaller amount of electrolyte, which can reduce the influence of the electrolyte extrusion on the first negative electrode active material layer 2312.

[0121] The negative electrode active section may have various shapes, and the shapes of the negative electrode active sections may be the same or different.

[0122] In some embodiments, as Figure 10 、 Figure 11 As shown, each negative electrode active segment is strip-shaped and arranged along the winding axis. The number of negative electrode active segments is an odd number.

[0123] like Figure 10As shown, there are seven negative electrode active segments, which are arranged along the winding axis Z in order: a first negative electrode active segment 2312a, a second negative electrode active segment 2312b, a third negative electrode active segment 2312c, a fourth negative electrode active segment 2312d, a fifth negative electrode active segment 2312e, a sixth negative electrode active segment 2312f, and a seventh negative electrode active segment 2312g. In the winding axis direction Z, the center plane of the fourth negative electrode active segment 2312d coincides with the center plane O2 of the first negative electrode active material layer and passes through the center O1 of the first negative electrode active material layer, the first negative electrode active segment 2312a and the seventh negative electrode active segment 2312g are symmetrical about the center plane O2 of the first negative electrode active material layer, the second negative electrode active segment 2312b and the sixth negative electrode active segment 2312f are symmetrical about the center plane O2 of the first negative electrode active material layer, and the third negative electrode active segment 2312c and the fifth negative electrode active segment 2312e are symmetrical about the center plane O2 of the first negative electrode active material layer.

[0124] Among them, the active material capacity per unit area of ​​the fourth negative electrode active segment 2312d is greater than the active material capacity per unit area of ​​the third negative electrode active segment 2312c, the active material capacity per unit area of ​​the third negative electrode active segment 2312c is greater than the active material capacity per unit area of ​​the second negative electrode active segment 2312b, and the active material capacity per unit area of ​​the second negative electrode active segment 2312b is greater than the active material capacity per unit area of ​​the first negative electrode active segment 2312a; the active material capacity per unit area of ​​the fourth negative electrode active segment 2312d is greater than the active material capacity per unit area of ​​the fifth negative electrode active segment 2312e, the active material capacity per unit area of ​​the fifth negative electrode active segment 2312e is greater than the active material capacity per unit area of ​​the sixth negative electrode active segment 2312f, and the active material capacity per unit area of ​​the sixth negative electrode active segment 2312f is greater than the active material capacity per unit area of ​​the seventh negative electrode active segment 2312g.

[0125] In some embodiments, as Figure 11 As shown, there are three negative electrode active segments, which are, in order along the winding axis direction Z, a first negative electrode active segment 2312a, a second negative electrode active segment 2312b, and a third negative electrode active segment 2312c. Along the winding axis direction Z, the center plane of the second negative electrode active segment 2312b coincides with the center plane O2 of the first negative electrode active material layer and passes through the center O1 of the first negative electrode active material layer. The first negative electrode active segment 2312a and the third negative electrode active segment 2312c are symmetrical about the center plane O2 of the first negative electrode active material layer.

[0126] The active material capacity per unit area of ​​the second negative active section 2312b is greater than that of the first negative active section 2312a. The active material capacity per unit area of ​​the second negative active section 2312b is greater than that of the third negative active section 2312c. The active material capacity per unit area of ​​the first negative active section 2312a is the same as that of the third negative active section 2312c.

[0127] Symmetrical means that the areas and active material capacities per unit area of ​​the two negative electrode active sections that are symmetrical about the central plane O2 of the first negative electrode active material layer are the same.

[0128] When the negative electrode active segments are strip-shaped and arranged along the winding axis direction Z, the distance between each negative electrode active segment and the center O1 of the first negative electrode active material layer can be understood as the distance between each negative electrode active segment and the center plane O2 of the first negative electrode active material layer.

[0129] In some embodiments, as Figure 12-14 As shown, the multiple negative electrode active segments include a central negative electrode active segment 2312h and at least one peripheral negative electrode active segment. Each peripheral negative electrode active segment is annular and surrounds the central negative electrode active segment 2312h. The central negative electrode active segment 2312h and the at least one peripheral negative electrode active segment are radially distributed from the center O1 of the first negative electrode active material layer. Each negative electrode active segment is distributed around the center O1 of the first negative electrode active material layer. In any direction, the active material capacity per unit area of ​​the negative electrode active segment closer to the center of the two adjacent negative electrode active segments is greater than the active material capacity per unit area of ​​the other negative electrode active segment.

[0130] The active material capacity per unit area of ​​the central negative electrode active section 2312h is greater than the active material capacity per unit area of ​​the peripheral negative electrode active sections.

[0131] In some embodiments, as Figure 12 As shown, the central negative active segment 2312h is rectangular, and there is one peripheral negative active segment, defined as the first peripheral negative active segment 2312i. The inner contour of the peripheral negative active segment is rectangular and coincides with the outer contour of the central negative active segment 2312h. The outer contour of the peripheral negative active segment is also rectangular. The center of the central negative active segment 2312h is the center O1 of the first negative active material layer.

[0132] In some embodiments, as Figure 13As shown, there are three peripheral negative electrode active segments, namely a first peripheral negative electrode active segment 2312i, a second peripheral negative electrode active segment 2312j and a third peripheral negative electrode active segment 2312k. A first peripheral negative electrode active segment 2312i is arranged around the central negative electrode active segment 2312h, with its inner contour coinciding with the outer contour of the central negative electrode active segment 2312h. A second peripheral negative electrode active segment 2312j is arranged around the first peripheral negative electrode active segment 2312i, with its inner contour coinciding with the outer contour of the first peripheral negative electrode active segment 2312i. A third peripheral negative electrode active segment 2312k is arranged around the second peripheral negative electrode active segment 2312j, with its inner contour coinciding with the outer contour of the second peripheral negative electrode active segment 2312j. The outer contour of the third peripheral negative electrode active segment 2312k is rectangular. The center of the central negative electrode active segment 2312h is the center O1 of the first negative electrode active material layer. The outer contour of the central negative active segment 2312h is a rectangle, the inner and outer contours of the first peripheral negative active segment 2312i are both rectangles, the inner and outer contours of the second peripheral negative active segment 2312j are both rectangles, and the inner and outer contours of the third peripheral negative active segment 2312k are both rectangles.

[0133] In some embodiments, as Figure 14 As shown, the outer contour of the central negative electrode active section 2312h is elliptical. The inner and outer contours of the first peripheral negative electrode active section 2312i are both elliptical; the inner and outer contours of the second peripheral negative electrode active section 2312j are both elliptical; the inner contour of the third peripheral negative electrode active section 2312k is elliptical, and the outer contour of the third peripheral negative electrode active material layer is rectangular. The elliptical shape of the central negative electrode active section 2312h better aligns with the expansion and deformation state of the first negative electrode active material layer 2312 when the abutment area B1 abuts the housing 21, thereby reducing the risk of lithium deposition caused by electrolyte extrusion when the abutment area B1 abuts the housing 21.

[0134] In some embodiments, the particle size of the active material in the first negative electrode active material layer 2312 is smaller than the particle size of the active material in the second negative electrode active material layer 2313. During the charge and discharge process, lithium ions diffuse more easily in the first negative electrode active material layer 2312, are more evenly distributed in the first negative electrode active material layer 2312, and are less likely to aggregate in the first negative electrode active material layer 2312, thereby reducing the risk of lithium plating and improving the fast charging performance of the first negative electrode active material layer 2312.

[0135] In some embodiments, in each first negative active material layer 2312 , the particle size of the active material in the negative active section closer to the center O1 of the first negative active material layer is smaller.

[0136] In some embodiments, for example, see Figure 14 The third peripheral negative electrode active zone 2312k is the region with the largest active material particle size in the first negative electrode active material layer 2312. If the particle size of the active material in the third peripheral negative electrode active zone 2312k is D, then the particle sizes of the active material in the second peripheral negative electrode active zone 2312j, the first peripheral negative electrode active zone 2312i, and the central negative electrode active zone 2312h are 0.8D, 0.6D, and 0.4D, respectively. When the electrode assembly 23 expands, the central negative electrode active zone 2312h expands the most. The active material in the central negative electrode active zone 2312h has the smallest particle size, which effectively improves the diffusion of lithium ions in the central negative electrode active zone 2312h and prevents aggregation in the central negative electrode active zone 2312h, thereby reducing the risk of lithium plating.

[0137] In some embodiments, as Figure 15 As shown, along the thickness direction X of the electrode assembly 23, the active material capacity per unit area of ​​the first negative electrode active material layer 2312 on the two surfaces of the negative electrode current collector 2311 is different. The active material capacity per unit area of ​​the first negative electrode active material layer 2312 on the surface of the negative electrode current collector 2311 closer to the thickness center plane B is smaller than the active material capacity per unit area of ​​the first negative electrode active material layer 2312 on the surface of the negative electrode current collector 2311 farther from the thickness center plane B. Figure 15 In the abutment area B1, the active material capacity per unit area of ​​the inner negative electrode active material layer 2312m inside the negative electrode current collector 2311 is smaller than the active material capacity per unit area of ​​the outer negative electrode active material layer 2312n. The inner and outer sides of the negative electrode current collector 2311 are defined relative to the thickness center plane B: the side closer to the thickness center plane B is the inner side, and the side farther from the thickness center plane B is the outer side.

[0138] In some embodiments, the positive electrode sheet 232 may be improved to reduce the risk of lithium deposition caused by the electrolyte being squeezed out when the abutting area B1 abuts against the shell 21 .

[0139] In some embodiments, as Figure 16 As shown, the active material capacity per unit area of ​​the first positive electrode active material layer 2322 is smaller than the active material capacity per unit area of ​​the second positive electrode active material layer 2323 .

[0140] In some embodiments, along the thickness direction X, the active material capacity per unit area of ​​the second positive electrode active material layer 2323 on the two surfaces of any layer of the positive electrode current collector 2321 is the same, then the active material capacity per unit area of ​​the second positive electrode active material layer 2323 can represent the active material capacity per unit area of ​​the second positive electrode active material layer 2323 on the two surfaces of the negative electrode current collector 2311 of the corresponding layer.

[0141] When the active material capacity per unit area of ​​the second positive electrode active material layer 2323 in the non-abutting area B2 that does not abut the housing 21 meets the design requirements, that is, the active material capacity per unit area of ​​the second positive electrode active material layer 2323 in the non-abutting area B2 reaches the second preset value, the second negative electrode active material layer 2313 in the non-abutting area B2 is less likely to undergo lithium deposition. When the active material capacity per unit area of ​​the first positive electrode active material layer 2322 in the abutting area B1 is less than the active material capacity per unit area of ​​the second positive electrode active material layer 2323 in the non-abutting area B2, that is, the active material capacity per unit area of ​​the first positive electrode active material layer 2322 is less than the second preset value, which is equivalent to reducing the active material capacity per unit area of ​​the first positive electrode active material layer 2322, the first negative electrode active material layer 2312 is able to accept lithium ions released from the first positive electrode active material layer 2322, and the possibility of lithium deposition in the first negative electrode in the abutting area B1 is low, thereby effectively reducing the risk of lithium deposition caused by the electrolyte being squeezed out when the abutting area B1 abuts the housing 21.

[0142] It should be noted that the active material capacity per unit area of ​​the first positive electrode active material layer 2322 refers to the ratio of the active material capacity of the first positive electrode active material layer 2322 to the total area of ​​the first positive electrode active material layer 2322, and the active material capacity per unit area of ​​the second positive electrode active material layer 2323 refers to the ratio of the active material capacity of the second positive electrode active material layer 2323 to the total area of ​​the second positive electrode active material layer 2323. To further explain, if the active material capacity of the first positive electrode active material layer 2322 is E1 and the area of ​​the first positive electrode active material layer 2322 is G1, then the capacity per unit area of ​​the first positive electrode active material layer 2322 EG1 = E1 / G1. If the active material capacity of the second positive electrode active material layer 2323 is E2 and the area of ​​the second positive electrode active material layer 2323 is G2, then the capacity per unit area of ​​the second positive electrode active material layer 2323 EG2 = E2 / G2.

[0143] There are many factors that affect the active material capacity per unit area of ​​the first positive electrode active material layer 2322 and the active material capacity per unit area of ​​the second positive electrode active material layer 2323. Therefore, there are many ways to achieve that the active material capacity per unit area of ​​the first positive electrode active material layer 2322 is smaller than the active material capacity per unit area of ​​the second positive electrode active material layer 2323.

[0144] In some embodiments, the gram capacity of the active material of the first positive electrode active material layer 2322 is smaller than the gram capacity of the active material of the second positive electrode active material layer 2323 .

[0145] By reducing the gram capacity of the active material of the first positive electrode active material layer 2322 in the abutment area B1, the active material capacity per unit area of ​​the first positive electrode active material layer 2322 in the abutment area B1 can be reduced, so that the capacity per unit area of ​​the first positive electrode active material layer 2322 in the abutment area B1 is smaller than the capacity per unit area of ​​the second positive electrode active material in the non-abutment area B2, which can effectively reduce the risk of lithium plating caused by the electrolyte being squeezed out when the abutment area B1 abuts against the shell 21.

[0146] The gram capacity is related to the active material in the first positive electrode active material layer 2322 and the active material in the second positive electrode active material layer 2323. For example, the active material in the first positive electrode active material layer 2322 is different from the active material in the second positive electrode active material layer 2323: lithium iron phosphate, while the active material in the second positive electrode active material layer 2323 is ternary lithium. The material activity of lithium iron phosphate is lower than that of ternary lithium, resulting in a lower lithium delithiation capacity of the first positive electrode active material layer 2322 than that of the second positive electrode active material layer 2323. This can further reduce the impact of electrolyte extrusion on the abutment area B1.

[0147] In some embodiments, the ratio of the weight of the active material in the first positive electrode active material layer 2322 to the weight of the first positive electrode active material layer 2322 is less than the ratio of the weight of the active material in the second positive electrode active material layer 2323 to the weight of the second positive electrode active material layer 2323. Both the first positive electrode active material layer 2322 and the second positive electrode active material layer 2323 include active material, a binder, and a conductive agent. By reducing the active material content in the first positive electrode active material layer 2322 and thereby reducing the proportion of active material in the first positive electrode active material layer 2322, the active material capacity per unit area of ​​the first positive electrode active material layer 2322 is reduced, so that the active material capacity per unit area of ​​the first positive electrode active material layer 2322 is less than the active material capacity per unit area of ​​the second positive electrode active material layer 2323.

[0148] In the abutting area B1 , along the thickness direction X, the closer the position is to the shell 21 , the more severe the degree of compression with the shell 21 .

[0149] Based on this, Figure 17As shown, in some embodiments, along the thickness direction X, the active material capacity per unit area of ​​one of the two adjacent first positive electrode active material layers 2322 is smaller than the active material capacity per unit area of ​​the other first positive electrode active material layer 2322, and the other first positive electrode active material layer 2322 is closer to the thickness center plane B than the one first positive electrode active material layer 2322. It can be understood that in the abutment area B1, along the thickness direction X, the farther the first positive electrode active material layer 2322 is from the thickness center plane B (the closer it is to the side wall 211 of the housing 21), the smaller the active material capacity per unit area, which can further effectively reduce the risk of lithium deposition caused by the electrolyte being squeezed out when the abutment area B1 abuts the housing 21.

[0150] There are many ways to ensure that the capacity per unit area of ​​the first positive electrode active material layer 2322 closer to the shell 21 of the two adjacent first positive electrode active material layers 2322 is smaller than the active material capacity per unit area of ​​the other second positive electrode active material layer 2323 .

[0151] In some embodiments, the gram capacity of the active material of one of the two adjacent first positive electrode active material layers 2322 is smaller than the gram capacity of the active material of the other first positive electrode active material layer 2322, and the other first positive electrode active material layer 2322 is closer to the thickness center plane B than the first first positive electrode active material layer 2322. It can be understood that in the abutment area B1, in the thickness direction X, the farther the first positive electrode active material layer 2322 is from the thickness center plane B (the closer it is to the sidewall 211 of the housing 21), the smaller the gram capacity of the first positive electrode active material layer 2322.

[0152] The gram capacity is related to the active material in the first positive electrode active material layer 2322. For example, the active materials of the two adjacent first positive electrode active material layers 2322 are different. The active material of the first positive electrode active material layer 2322 close to the shell 21 is lithium iron phosphate, and the active material of the other first positive electrode active material is ternary lithium, so that the delithiation ability of the first positive electrode active material layer 2322 close to the shell 21 of the two adjacent first positive electrode active material layers 2322 is smaller than the delithiation ability of the other first positive electrode active material layer 2322, which can further reduce the influence of the electrolyte extrusion on the abutment area B1.

[0153] In some embodiments, the ratio of the weight of the active material of one of the two adjacent first positive electrode active material layers 2322 to the weight of the first positive electrode active material layer 2322 is smaller than the ratio of the weight of the active material of the other first positive electrode active material layer 2322 to the weight of the other first positive electrode active material layer 2322, and the other first positive electrode active material layer 2322 is closer to the thickness center plane B than the one first positive electrode active material layer 2322. It can be understood that, in the abutting area B1, in the thickness direction X, the farther from the thickness center plane B (the closer to the sidewall 211 of the housing 21), the smaller the ratio of the weight of the active material of the first positive electrode active material layer 2322 to the weight of the first positive electrode active material layer 2322.

[0154] By reducing the active material in one of the two adjacent first positive electrode active material layers 2322 that is close to the shell 21, the proportion of active material in the first positive electrode active material layer 2322 is reduced, thereby reducing the active material capacity per unit area of ​​the first positive electrode active material layer 2322, so that the active material capacity per unit area of ​​the first positive electrode active material layer 2322 close to the shell 21 is smaller than the active material capacity per unit area of ​​the other first positive electrode active material layer 2322.

[0155] For each first positive electrode active material layer 2322 , when the electrode assembly 23 expands, the closer to the center O3 of the first positive electrode active material layer, the greater the squeezing force, and the greater the degree to which the electrolyte is squeezed out.

[0156] Based on this, in some embodiments, such as Figure 18 As shown, the first positive electrode active material layer 2322 includes multiple positive electrode active segments. The active material capacity per unit area of ​​one of two adjacent positive electrode active segments is smaller than the active material capacity per unit area of ​​the other positive electrode active segment. The one positive electrode active segment is closer to the center O3 of the first positive electrode active material layer than the other positive electrode active segment. It can be understood that in the abutment area B1, the closer the positive electrode active segment is to the center O3 of the first positive electrode active material layer, the smaller the active material capacity per unit area. By dividing the first positive electrode active material layer 2322 into multiple negative electrode active segments, and the closer to the center O3 of the first positive electrode active material layer, the smaller the active material capacity per unit area of ​​the negative electrode active segment, thereby reducing the lithium delithiation ability of the positive electrode active segment near the center of the first positive electrode active material layer 2322, so that the position near the center of the first negative electrode active material layer 2312 is less affected by the squeezing out of the electrolyte, which can further effectively reduce the risk of lithium precipitation caused by the squeezing out of the electrolyte when the abutment area B1 abuts against the shell 21.

[0157] In some embodiments, the gram capacity of the active material of one of two adjacent positive electrode active segments is smaller than the gram capacity of the active material of the other positive electrode active segment, and the one positive electrode active segment is closer to the center O3 of the first positive electrode active material layer than the other positive electrode active segment, so that the active material capacity per unit area of ​​the positive electrode active segment closer to the center O3 of the first positive electrode active material layer is smaller.

[0158] In some embodiments, the ratio of the weight of the active material of one of two adjacent positive electrode active segments to the weight of the one positive electrode active segment is less than the ratio of the weight of the active material of the other positive electrode active segment to the weight of the other positive electrode active segment, and the one positive electrode active segment is closer to the center O3 of the first positive electrode active material layer than the other positive electrode active segment, so that the active material capacity per unit area of ​​the positive electrode active segment closer to the center O3 of the first positive electrode active material layer is smaller. By reducing the active material in the one of the two adjacent positive electrode active segments closer to the center O3 of the first positive electrode active material layer, the proportion of active material in the positive electrode active segment is reduced, thereby reducing the active material capacity per unit area of ​​the positive electrode active segment, so that the active material capacity per unit area of ​​the positive electrode active segment closer to the center O3 of the first positive electrode active material layer is smaller than the active material capacity per unit area of ​​the other positive electrode active segment.

[0159] The positive electrode active section can have various shapes, and the shapes of the negative electrode active sections can be the same or different.

[0160] In some embodiments, as Figure 19 、 Figure 20 As shown, each positive electrode active segment is strip-shaped, and each positive electrode active segment is arranged along the winding axis. The strip-shaped positive electrode active segment facilitates the coating of the negative electrode active material layer. The number of negative electrode active segments is an odd number.

[0161] like Figure 19As shown, there are seven positive electrode active segments, which are arranged along the winding axis Z in order: a first positive electrode active segment 2322a, a second positive electrode active segment 2322b, a third positive electrode active segment 2322c, a fourth positive electrode active segment 2322d, a fifth positive electrode active segment 2322e, a sixth positive electrode active segment 2322f, and a seventh positive electrode active segment 2322g. In the winding axis direction Z, the center plane of the fourth positive electrode active segment 2322d coincides with the center plane O4 of the first positive electrode active material layer and passes through the center O3 of the first positive electrode active material layer, the first positive electrode active segment 2322a and the seventh positive electrode active segment 2322g are symmetrical about the center plane O4 of the first positive electrode active material layer, the second positive electrode active segment 2322b and the sixth positive electrode active segment 2322f are symmetrical about the center plane O4 of the first positive electrode active material layer, and the third positive electrode active segment 2322c and the fifth positive electrode active segment 2322e are symmetrical about the center plane O4 of the first positive electrode active material layer.

[0162] The active material capacity per unit area of ​​the fourth positive electrode active segment 2322d is smaller than the active material capacity per unit area of ​​the third positive electrode active segment 2322c, the active material capacity per unit area of ​​the third positive electrode active segment 2322c is smaller than the active material capacity per unit area of ​​the second negative electrode active segment 2312b, the active material capacity per unit area of ​​the second positive electrode active segment 2322b is smaller than the active material capacity per unit area of ​​the first positive electrode active segment 2322a; the active material capacity per unit area of ​​the fourth positive electrode active segment 2322d is smaller than the active material capacity per unit area of ​​the fifth positive electrode active segment 2322e, the active material capacity per unit area of ​​the fifth positive electrode active segment 2322e is smaller than the active material capacity per unit area of ​​the sixth positive electrode active segment 2322f, and the active material capacity per unit area of ​​the sixth positive electrode active segment 2322f is smaller than the active material capacity per unit area of ​​the seventh positive electrode active segment 2322g.

[0163] In some embodiments, as Figure 20 As shown, there are three positive electrode active segments, which are, in order along the winding axis direction Z, the first positive electrode active segment 2322a, the second positive electrode active segment 2322b, and the third positive electrode active segment 2322c. In the winding axis direction Z, the center plane of the second positive electrode active segment 2322b coincides with the center plane O4 of the first positive electrode active material layer and passes through the center O3 of the first positive electrode active material layer. The first positive electrode active segment 2322a and the third positive electrode active segment 2322c are symmetrical about the center plane O4 of the first positive electrode active material layer.

[0164] The active material capacity per unit area of ​​the second positive active segment 2322b is smaller than that of the first positive active segment 2322a, and the active material capacity per unit area of ​​the second positive active segment 2322b is smaller than that of the third positive active segment 2322c. The active material capacity per unit area of ​​the first positive active segment 2322a is the same as that of the third positive active segment 2322c.

[0165] When the positive electrode active segments are strip-shaped and arranged along the winding axis direction Z, the distance between each positive electrode active segment and the center O3 of the first positive electrode active material layer can be understood as the distance between each positive electrode active segment and the center plane O4 of the first positive electrode active material layer.

[0166] In some embodiments, as Figure 21-23 As shown, the multiple positive electrode active segments include a central positive electrode active segment 2322h and at least one peripheral positive electrode active segment, each peripheral positive electrode active segment is annular and surrounds the central positive electrode active segment 2322h, and the central positive electrode active segment 2322h and the at least one peripheral positive electrode active segment are radially distributed from the center O3 of the first positive electrode active material layer.

[0167] The active material capacity per unit area of ​​the central positive electrode active section 2322h is smaller than the active material capacity per unit area of ​​the peripheral positive electrode active sections.

[0168] In some embodiments, as Figure 21 As shown, the central positive active segment 2322h is rectangular, and there is one peripheral positive active segment, defined as the first peripheral positive active segment 2322i. The inner contour of the peripheral positive active segment is rectangular and coincides with the outer contour of the central positive active segment 2322h. The outer contour of the peripheral positive active segment is also rectangular. The center of the central positive active segment 2322h is the center O3 of the first positive active material layer.

[0169] In some embodiments, as Figure 22As shown, there are three peripheral negative electrode active segments, namely a first peripheral positive electrode active segment 2322i, a second peripheral positive electrode active segment 2322j and a third peripheral positive electrode active segment 2322k. The first peripheral positive electrode active segment 2322i is arranged around the central positive electrode active segment 2322h, and its inner contour coincides with the outer contour of the central positive electrode active segment 2322h. The second peripheral positive electrode active segment 2322j is arranged around the first peripheral positive electrode active segment 2322i, and its inner contour coincides with the outer contour of the first peripheral positive electrode active segment 2322i. The third peripheral positive electrode active segment 2322k is arranged around the second peripheral positive electrode active segment 2322j, and its inner contour coincides with the outer contour of the second peripheral positive electrode active segment 2322j. The outer contour of the third peripheral positive electrode active segment 2322k is rectangular. The center of the central positive electrode active segment 2322h is the center O3 of the first positive electrode active material layer. The outer contour of the central positive active segment 2322h is a rectangle, the inner and outer contours of the first peripheral positive active segment 2322i are both rectangles, the inner and outer contours of the second peripheral positive active segment 2322j are both rectangles, and the inner and outer contours of the third peripheral positive active segment 2322k are both rectangles.

[0170] In some embodiments, as Figure 23 As shown, the outer contour of the central positive electrode active segment 2322h is elliptical, which can be closer to the expansion deformation state of the first positive electrode active material layer 2322 when the abutment area B1 abuts against the shell 21, which is beneficial to reducing the risk of lithium plating caused by the electrolyte being squeezed out when the abutment area B1 abuts against the shell 21.

[0171] In some embodiments, the particle size of the active material in the first positive electrode active material layer 2322 is larger than the particle size of the active material in the second positive electrode active material layer 2323. During the charge and discharge process, the diffusion rate of lithium ions in the first positive electrode active material layer is low, and the rate at which lithium ions are released from the first positive electrode active material layer is also slowed. This can reduce the risk of lithium ions released from the first positive electrode active material layer gathering in the first negative electrode active material layer, making it less likely for lithium to be deposited in the first negative electrode active material layer.

[0172] In some embodiments, in each first positive active material layer 2322 , the particle size of the active material in the positive active section closer to the center O3 of the first positive active material layer is larger.

[0173] For example, please see Figure 23The central positive electrode active segment 2322h is the segment with the largest particle size of the active material in the first positive electrode active material layer 2322. The particle size of the active material in the central positive electrode active segment 2322h is K, then the particle size of the active material in the first peripheral positive electrode active segment 2322i, the particle size of the active material in the second peripheral positive electrode active segment 2322j and the particle size of the active material in the third peripheral positive electrode active segment 2322k are 0.8K, 0.6K and 0.4K respectively.

[0174] In some embodiments, as Figure 24 As shown, along the thickness direction X of the electrode assembly 23, the active material capacity per unit area of ​​the first positive active material layer 2322 on both surfaces of the positive electrode current collector 2321 is different. The active material capacity per unit area of ​​the first positive active material layer 2322 on the surface of the positive electrode current collector 2321 closer to the thickness center plane B is smaller than the active material capacity per unit area of ​​the first positive active material layer 2322 on the surface of the positive electrode current collector 2321 farther from the thickness center plane B. That is, in FIG24 , in the abutment area B1, the active material capacity per unit area of ​​the inner positive active material layer 2322m of the positive electrode current collector 2321 is greater than the active material capacity per unit area of ​​the outer positive active material layer 2322n of the positive electrode current collector 2321. The inner and outer sides of the positive electrode current collector 2321 are relative to the thickness center plane B: the side closer to the thickness center plane B is the inner side, and the side farther from the thickness center plane B is the outer side.

[0175] In some embodiments, as Figure 25 As shown, both the negative electrode sheet 231 and the positive electrode sheet 232 can be improved so that the active material capacity per unit area of ​​the first negative electrode active material layer 2312 is greater than the active material capacity per unit area of ​​the second negative electrode active material layer 2313; and the active material capacity per unit area of ​​the first positive electrode active material layer 2322 is less than the active material capacity per unit area of ​​the second positive electrode active material layer 2323.

[0176] like Figure 26 As shown, the embodiment of the present application further provides a method for manufacturing an electrode assembly 23, comprising:

[0177] S100: Providing a positive electrode sheet 232 and a negative electrode sheet 231;

[0178] S200: The negative electrode sheet 231 and the positive electrode sheet 232 are stacked and wound around a winding axis to form a winding structure, so that the electrode assembly 23 includes abutment areas B1 for abutting against the shell 21 and non-abutment areas B2 that do not abut against the shell 21 located on both sides of its thickness center plane B, and the thickness center plane B is perpendicular to the thickness direction X of the electrode assembly 23 and passes through the winding axis.

[0179] Among them, the negative electrode sheet 231 includes a plurality of first negative electrode active material layers 2312 located in the abutment area B1 and stacked along the thickness direction X, and a plurality of second negative electrode active material layers 2313 located in the non-abutment area B2 and stacked along the thickness direction X; the positive electrode sheet 232 includes a plurality of first positive electrode active material layers 2322 located in the abutment area B1 and stacked along the thickness direction X, and a plurality of second positive electrode active material layers 2323 located in the non-abutment area B2 and stacked along the thickness direction X; the active material capacity per unit area of ​​the first negative electrode active material layer 2312 is greater than the active material capacity per unit area of ​​the second negative electrode active material layer 2313; and / or, the active material capacity per unit area of ​​the first positive electrode active material layer 2322 is less than the active material capacity per unit area of ​​the second positive electrode active material layer 2323.

[0180] It should be noted that the relevant structure of the electrode assembly 23 manufactured by the above-mentioned manufacturing method of the electrode assembly 23 can refer to the electrode assembly 23 provided in the above-mentioned embodiments.

[0181] like Figure 27 As shown, the embodiment of the present application also provides an electrode assembly manufacturing device 400, including: a providing device 410 for providing a positive electrode sheet 232 and a negative electrode sheet 231; an assembling device 420 for stacking the positive electrode sheet 232 and the negative electrode sheet 231 and winding them to form a winding structure, so that the electrode assembly 23 includes abutting areas B1 located on both sides of its thickness center plane B for abutting against the shell 21 and a non-abutting area B2 that does not abut against the shell 21, and the thickness center plane B is perpendicular to the thickness direction X of the electrode assembly 23 and passes through the winding axis; wherein the negative electrode sheet 231 includes a plurality of first negative electrode active material layers 2312 and a plurality of first negative electrode active material layers 2313 located in the abutting area B1 and stacked along the thickness direction X. A plurality of second negative electrode active material layers 2313 are stacked in the non-abutment area B2 and along the thickness direction X; the positive electrode sheet 232 includes a plurality of first positive electrode active material layers 2322 located in the abutment area B1 and arranged in a stacked manner along the thickness direction X, and a plurality of second positive electrode active material layers 2323 located in the non-abutment area B2 and arranged in a stacked manner along the thickness direction X; the active material capacity per unit area of ​​the first negative electrode active material layer 2312 is greater than the active material capacity per unit area of ​​the second negative electrode active material layer 2313; and / or, the active material capacity per unit area of ​​the first positive electrode active material layer 2322 is less than the active material capacity per unit area of ​​the second positive electrode active material layer 2323.

[0182] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A battery cell, characterized in that: The invention comprises a housing and two electrode assemblies, wherein the two electrode assemblies are accommodated in the housing, the electrode assemblies comprising a positive electrode sheet and a negative electrode sheet, the positive electrode sheet and the negative electrode sheet are stacked and wound around a winding axis; The electrode assembly includes an abutting area for abutting against the shell and a non-abutting area not abutting against the shell, located on both sides of a thickness center plane thereof, wherein the thickness center plane is perpendicular to the thickness direction of the electrode assembly and passes through the winding axis; The two electrode assemblies are arranged side by side along the thickness direction, and the abutting areas of the two electrode assemblies are arranged away from each other; The negative electrode sheet includes a plurality of first negative electrode active material layers located in the abutting area and stacked along the thickness direction, and a plurality of second negative electrode active material layers located in the non-abutting area and stacked along the thickness direction; the positive electrode sheet includes a plurality of first positive electrode active material layers located in the abutting area and stacked along the thickness direction, and a plurality of second positive electrode active material layers located in the non-abutting area and stacked along the thickness direction; The active material capacity per unit area of ​​the first negative electrode active material layer is greater than the active material capacity per unit area of ​​the second negative electrode active material layer; And / or, the active material capacity per unit area of ​​the first positive electrode active material layer is smaller than the active material capacity per unit area of ​​the second positive electrode active material layer.

2. The battery cell according to claim 1, wherein: The gram capacity of the active material of the first negative electrode active material layer is greater than the gram capacity of the active material of the second negative electrode active material layer; and / or the gram capacity of the active material of the first positive electrode active material layer is less than the gram capacity of the active material of the second positive electrode active material layer.

3. The battery cell according to claim 1, wherein: The ratio of the weight of the active material of the first negative electrode active material layer to the weight of the first negative electrode active material layer is greater than the ratio of the weight of the active material of the second negative electrode active material layer to the weight of the second negative electrode active material layer; and / or, the ratio of the weight of the active material of the first positive electrode active material layer to the weight of the first positive electrode active material layer is less than the ratio of the weight of the active material of the second positive electrode active material layer to the weight of the second positive electrode active material layer.

4. The battery cell according to claim 1, wherein: The active material capacity per unit area of ​​one of the two adjacent first negative electrode active material layers is greater than the active material capacity per unit area of ​​the other first negative electrode active material layer, and the other first negative electrode active material layer is closer to the thickness center plane than the one first negative electrode active material layer; and / or, the active material capacity per unit area of ​​one of the two adjacent first positive electrode active material layers is less than the active material capacity per unit area of ​​the other first positive electrode active material layer, and the other first positive electrode active material layer is closer to the thickness center plane than the one first positive electrode active material layer.

5. The battery cell according to claim 4, characterized in that The gram capacity of the active material of one of the two adjacent first negative electrode active material layers is greater than the gram capacity of the active material of the other first negative electrode active material layer, and the other first negative electrode active material layer is closer to the thickness center plane than the one first negative electrode active material layer; and / or, the gram capacity of the active material of the first positive electrode active material layer of one of the two adjacent first positive electrode active material layers is less than the gram capacity of the active material of the other first positive electrode active material layer, and the other first positive electrode active material layer is closer to the thickness center plane than the one first positive electrode active material layer.

6. The battery cell according to claim 4, characterized in that The ratio of the weight of the active material of one of the two adjacent first negative electrode active material layers to the weight of the one first negative electrode active material layer is greater than the ratio of the weight of the active material of the other first negative electrode active material layer to the weight of the other first negative electrode active material layer, and the other first negative electrode active material layer is closer to the thickness center plane than the one first negative electrode active material layer; and / or, the ratio of the weight of the active material of one of the two adjacent first positive electrode active material layers to the weight of the one first positive electrode active material layer is less than the ratio of the weight of the active material of the other first positive electrode active material layer to the weight of the other first positive electrode active material layer, and the other first positive electrode active material layer is closer to the thickness center plane than the one first positive electrode active material layer.

7. The battery cell according to any one of claims 1 to 6, characterized in that: The first negative electrode active material layer includes a plurality of negative electrode active segments, and the first positive electrode active material layer includes a plurality of positive electrode active segments; The active material capacity per unit area of ​​one of the two adjacent negative electrode active segments is greater than the active material capacity per unit area of ​​the other negative electrode active segment, and the one negative electrode active segment is closer to the center of the first negative electrode active material layer than the other negative electrode active segment; and / or, the active material capacity per unit area of ​​one of the two adjacent positive electrode active segments is less than the active material capacity per unit area of ​​the other positive electrode active segment, and the one positive electrode active segment is closer to the center of the first positive electrode active material layer than the other positive electrode active segment.

8. The battery cell according to claim 7, characterized in that The gram capacity of the active material in one of the two adjacent negative electrode active segments is greater than the gram capacity of the active material in the other negative electrode active segment, and the one negative electrode active segment is closer to the center of the first negative electrode active material layer than the other negative electrode active segment; and / or the gram capacity of the active material in one of the two adjacent positive electrode active segments is less than the gram capacity of the active material in the other positive electrode active segment, and the one positive electrode active segment is closer to the center of the first positive electrode active material layer than the other positive electrode active segment.

9. The battery cell according to claim 7, characterized in that: The ratio of the weight of the active material of one negative electrode active segment of two adjacent negative electrode active segments to the weight of the one negative electrode active segment is greater than the ratio of the weight of the active material of the other negative electrode active segment to the weight of the other negative electrode active segment, and the one negative electrode active segment is closer to the center of the first negative electrode active material layer than the other negative electrode active segment; and / or, the ratio of the weight of the active material of one positive electrode active segment of two adjacent positive electrode active segments to the weight of the one positive electrode active segment is less than the ratio of the weight of the active material of the other positive electrode active segment to the weight of the other positive electrode active segment, and the one positive electrode active segment is closer to the center of the first positive electrode active material layer than the other positive electrode active segment.

10. The battery cell according to claim 7, characterized in that Each negative electrode active segment is strip-shaped, and the multiple negative electrode active segments are arranged along the direction of the winding axis; and / or each positive electrode active segment is strip-shaped, and the multiple positive electrode active segments are arranged along the direction of the winding axis.

11. The battery cell according to claim 7, characterized in that The multiple negative electrode active segments include a central negative electrode active segment and at least one peripheral negative electrode active segment, each peripheral negative electrode active segment is annular and surrounds the central negative electrode active segment, and the central negative electrode active segment and the at least one peripheral negative electrode active segment are radially distributed from the center of the first negative electrode active material layer; and / or, the multiple positive electrode active segments include a central positive electrode active segment and at least one peripheral positive electrode active segment, each peripheral positive electrode active segment is annular and surrounds the central positive electrode active segment, and the central positive electrode active segment and the at least one peripheral positive electrode active segment are radially distributed from the center of the first positive electrode active material layer.

12. The battery cell according to claim 11, characterized in that The central negative electrode active section and / or the central positive electrode active section are elliptical.

13. A battery, wherein: The invention comprises the battery cell according to any one of claims 1 to 12.

14. An electrical device, wherein: The invention comprises the battery cell according to any one of claims 1 to 12.

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