Battery cell, secondary battery, and electronic device

Abstract

An electrode group, a secondary battery, and an electronic device are provided. The electrode group includes a first electrode sheet, a separator, and a second electrode sheet that are stacked and wound. The electrode group includes a first flat section, a first bent section, a second flat section, and a second bent section that are sequentially connected. The first flat section and the second flat section are arranged opposite each other in a first direction. The first bent section and the second bent section are arranged opposite each other in a second direction. The first electrode sheet includes a first current collector, a first active material layer, and a first solid electrolyte layer. The first active material layer is arranged on at least one side surface of the first current collector in a thickness direction of the first current collector. In at least a portion of the first electrode sheet in the first bent section and / or the second bent section, the first active material layer is provided with the first solid electrolyte layer in at least a portion of an area in which the first active material layer is away from the surface of the first current collector.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a battery cell, a secondary battery, and an electronic device. Background Technology

[0002] In existing wound battery cells, the high tension at the corners results in small spacing between the corner electrodes. During cell cycling, the corners are prone to interface problems such as lithium plating or electrolyte wetting bridging due to insufficient electrolyte, leading to reduced cell cycle performance. Summary of the Invention

[0003] In view of the above situation, this application provides a battery cell that is beneficial to improving the cycle performance of the battery cell.

[0004] Embodiments of this application provide a battery cell, which includes an electrode assembly with its thickness direction in a first direction. The electrode assembly includes a first electrode, a separator, and a second electrode stacked and wound together. The electrode assembly includes a first straight section, a first bent section, a second straight section, and a second bent section connected in sequence. Viewed along a third direction, the first straight section and the second straight section are arranged opposite each other along the first direction, and the first bent section and the second bent section are arranged opposite each other along a second direction. The first direction, the second direction, and the third direction are perpendicular to each other. The first electrode includes a first current collector, a first active material layer, and a first solid electrolyte layer. Along the thickness direction of the first current collector, the first active material layer is disposed on at least one side surface of the first current collector. In at least a portion of the first electrode located in the first bent section and / or the second bent section, at least a portion of the surface of the first active material layer away from the first current collector is provided with the first solid electrolyte layer.

[0005] In the aforementioned battery cell, the first solid electrolyte layer provides physical support for the first and / or second bending sections, improving the structural stability at the cell's corners. The first solid electrolyte layer also promotes lithium-ion desolvation through dielectricization, thereby providing ion channels at the cell corners and reducing the risk of interface problems such as lithium plating or electrolyte wetting bridging due to insufficient electrolyte at the corners, thus improving the cell's cycle performance. Simultaneously, by solving the lithium plating problem at the corners, the cell's expansion rate is reduced.

[0006] In some embodiments of this application, along a third direction, the ratio of the length of the first solid electrolyte layer to the length of the first active material layer in which the first solid electrolyte layer is located is A1, 60%≤A1≤100%, in order to reduce the risk of interface problems such as lithium plating or electrolyte wetting breakage at the corners of the battery cell due to insufficient electrolyte, improve the cycle performance of the battery cell, and help reduce the space waste caused by the first solid electrolyte layer protruding from the first active material layer, thereby increasing the energy density of the battery cell.

[0007] In some embodiments of this application, in at least a portion of the first electrode located in the first bending section or the second bending section, along the winding direction of the first electrode, the ratio of the width of the first solid electrolyte layer to the width of the first active material layer containing the first solid electrolyte layer is B1, 50%≤B1≤100%, in order to reduce the risk of interface problems such as lithium plating or electrolyte wetting breakage at the corners of the battery cell due to insufficient electrolyte, improve the cycle performance of the battery cell, and help reduce the space waste caused by the first solid electrolyte layer protruding from the first active material layer, thereby increasing the energy density of the battery cell.

[0008] In some embodiments of this application, the coating weight per unit area of ​​the first solid electrolyte layer is W1, where 0.5 mg / cm² ≤ W1 ≤ 5 mg / cm². If W1 is too small, it reduces lithium-ion transport efficiency; if W1 is too large, it results in an excessively thick solid electrolyte layer, affecting the volumetric energy density of the battery cell and increasing the lithium-ion transport path, as well as production and material costs. Therefore, setting W1 to 0.5 mg / cm² ≤ W1 ≤ 5 mg / cm² improves lithium-ion transport efficiency and the energy density of the battery cell, and also helps to shorten the lithium-ion transport path, reducing material and production costs.

[0009] In some embodiments of this application, 1 mg / cm² ≤ W1 ≤ 3 mg / cm², in order to further improve the lithium-ion transport efficiency and the energy density of the battery cell, and further facilitate the shortening of the lithium-ion transport path, thereby reducing material costs and production costs.

[0010] In some embodiments of this application, the first solid electrolyte layer includes a first solid electrolyte, the material of which includes at least one of organic solid electrolyte and inorganic solid electrolyte; wherein, the organic solid electrolyte includes a block copolymer, the block copolymer includes a conductive polymer and a lithium-conducting polymer, the conductive polymer includes at least one of pyrrole, aniline, thiophene, polyacetylene, p-phenylenediamine terephthalamide or 3,4-ethylenedioxythiophene, and the lithium-conducting polymer includes at least one of polyethylene oxide, polyethylene glycol, polyethylene oxide, poly(ethylene glycol) acrylate or poly(ethylene glycol) methacrylate; the inorganic solid electrolyte includes at least one of oxide solid electrolyte and sulfide solid electrolyte, the oxide solid electrolyte includes at least one of lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide or lithium lanthanum titanate, and the sulfide solid electrolyte includes at least one of lithium sulfur silver germanium or lithium sulfur phosphorus.

[0011] In some embodiments of this application, the first solid electrolyte layer further includes a first binder and a first conductive agent. The material of the first binder includes at least one of polyvinylidene fluoride, polyacrylic acid, and carboxymethyl cellulose, and the material of the first conductive agent includes at least one of carbon nanotubes, carbon black, conductive graphite, and graphene.

[0012] In some embodiments of this application, the mass ratio of the first adhesive to the mass of the first solid electrolyte layer is W2, where 1% ≤ W2 ≤ 10%, to improve the peel strength between the first solid electrolyte layer and the first active material layer and to improve the cycle performance of the battery cell. If W1 is too small, the solid electrolyte layer is prone to powder shedding and falling off, affecting the stability and lifespan of the battery cell; if W1 is too large, it may lead to an increase in mechanical stress between the solid electrolyte layer and the active material layer, causing the battery cell to be prone to deformation.

[0013] In some embodiments of this application, the first electrode includes a second solid electrolyte layer and a third solid electrolyte layer. In the first electrode located in the first straight section, a second solid electrolyte layer is disposed in a portion of the surface of the first active material layer away from the first current collector. In the first electrode located in the second straight section, a third solid electrolyte layer is disposed in a portion of the surface of the first active material layer away from the first current collector. The second and third solid electrolyte layers can promote lithium-ion desolvation through dielectricization, thereby expanding the range of ion channels in conjunction with the first solid electrolyte layer. This further reduces the risk of interface problems such as lithium plating or electrolyte wetting bridging at the corners of the battery cell due to insufficient electrolyte, thereby improving the cycle performance of the battery cell.

[0014] In some embodiments of this application, the first bending section includes an N1 layer first electrode. In the first electrode of the 1 / 3 N1 layer located inside the first bending section, the two ends of the first solid electrolyte layer are respectively connected to the second solid electrolyte layer and the third solid electrolyte layer along the winding direction of the first electrode. This is to specifically expand the range of ion channels inside the first bending section, reduce the risk of interface problems such as lithium plating or electrolyte wetting bridging caused by insufficient electrolyte inside the first bending section, and thus improve the cycle performance of the battery cell.

[0015] In some embodiments of this application, the second bending section includes an N2 layer first electrode. In the first electrode of the 1 / 3 N2 layer located inside the second bending section, the two ends of the first solid electrolyte layer are respectively connected to the second solid electrolyte layer and the third solid electrolyte layer along the winding direction of the first electrode. This is to specifically expand the range of ion channels inside the second bending section, reduce the risk of interface problems such as lithium plating or electrolyte wetting bridging caused by insufficient electrolyte in the first electrode inside the second bending section, and thus improve the cycle performance of the battery cell.

[0016] In some embodiments of this application, the length of the second solid electrolyte layer along the second direction is L1, 0.5mm≤L1≤2mm, which is beneficial to improving the cycle performance and energy density of the battery cell. And / or the length of the third solid electrolyte layer along the second direction is L2, 0.5mm≤L2≤2mm, which is beneficial to improving the cycle performance and energy density of the battery cell.

[0017] In some embodiments of this application, 1mm≤L1≤1.5mm; and / or, 1mm≤L2≤1.5mm.

[0018] In some embodiments of this application, the first electrode is a negative electrode and the second electrode is a positive electrode.

[0019] In some embodiments of this application, the second electrode includes a second current collector, a second active material layer, and a fourth solid electrolyte layer. Along the thickness direction of the second current collector, the second active material layer is disposed on at least one side surface of the second current collector. In at least a portion of the second electrode located in the first bending section and / or the second bending section, at least a portion of the surface of the second active material layer away from the second current collector is provided with the fourth solid electrolyte layer.

[0020] In some embodiments of this application, in the second electrode sheet of the same layer located in the first bending section, on the side facing the winding center of the electrode assembly, the ratio of the area of ​​the fourth solid electrolyte layer to the area of ​​the second active material layer in which the fourth solid electrolyte layer is located is C1; on the side away from the winding center of the electrode assembly, the ratio of the area of ​​the fourth solid electrolyte layer to the area of ​​the second active material layer in which the fourth solid electrolyte layer is located is C2; C1 > C2, so that the first solid electrolyte layer provides sufficient ion channels for the first electrode sheet to receive lithium ions on the side facing the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0021] In some embodiments of this application, in the same layer of the second electrode located in the second bend section, on the side facing the winding center of the electrode assembly, the ratio of the area of ​​the fourth solid electrolyte layer to the area of ​​the second active material layer containing the fourth solid electrolyte layer is C1′; on the side away from the winding center of the electrode assembly, the ratio of the area of ​​the fourth solid electrolyte layer to the area of ​​the second active material layer containing the fourth solid electrolyte layer is C2′; C1′>C2′, so that the fourth solid electrolyte layer provides sufficient ion channels for the first electrode to receive lithium ions on the side facing the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0022] In some embodiments of this application, in the second electrode sheet of the same layer located in the first bending section, the coating weight per unit area of ​​the fourth solid electrolyte layer is W3 on the side facing the winding center of the electrode assembly; and the coating weight per unit area of ​​the fourth solid electrolyte layer is W4 on the side away from the winding center of the electrode assembly; W3 > W4, so that the fourth solid electrolyte layer provides sufficient ion channels for the first electrode sheet to receive lithium ions on the side facing the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0023] In some embodiments of this application, in the second electrode sheet of the same layer located in the second bending section, the coating weight per unit area of ​​the fourth solid electrolyte layer is W3′ on the side facing the winding center of the electrode assembly; and the coating weight per unit area of ​​the fourth solid electrolyte layer is W4′ on the side away from the winding center of the electrode assembly; W3′ > W4′, so that the first solid electrolyte layer provides sufficient ion channels for the first electrode sheet to receive lithium ions on the side facing the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0024] In some embodiments of this application, in the same layer of the first electrode sheet located in the first bending section, on the side facing the winding center of the electrode assembly, the ratio of the area of ​​the first solid electrolyte layer to the area of ​​the first active material layer in which the first solid electrolyte layer is located is C3; on the side away from the winding center of the electrode assembly, the ratio of the area of ​​the first solid electrolyte layer to the area of ​​the first active material layer in which the first solid electrolyte layer is located is C4; C4 > C3, so that the first solid electrolyte layer provides sufficient ion channels for the first electrode sheet to receive lithium ions on the side away from the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0025] In some embodiments of this application, in the same layer of the first electrode sheet located in the second bending section, on the side facing the winding center of the electrode assembly, the ratio of the area of ​​the first solid electrolyte layer to the area of ​​the first active material layer in which the first solid electrolyte layer is located is C3′; on the side away from the winding center of the electrode assembly, the ratio of the area of ​​the first solid electrolyte layer to the area of ​​the first active material layer in which the fourth solid electrolyte layer is located is C4′; C4′>C3′, so that the first solid electrolyte layer provides sufficient ion channels for the first electrode sheet to receive lithium ions on the side away from the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0026] In some embodiments of this application, in the same layer of the first electrode sheet located in the first bending section, the coating weight per unit area of ​​the first solid electrolyte layer is W5 on the side facing the winding center of the electrode assembly; and the coating weight per unit area of ​​the first solid electrolyte layer is W6 on the side away from the winding center of the electrode assembly; W6 > W5, so that the first solid electrolyte layer provides sufficient ion channels for the first electrode sheet to receive lithium ions on the side away from the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0027] In some embodiments of this application, in the same layer of the first electrode sheet located in the second bending section, the coating weight per unit area of ​​the first solid electrolyte layer is W5′ on the side facing the winding center of the electrode assembly; and the coating weight per unit area of ​​the first solid electrolyte layer is W6′ on the side away from the winding center of the electrode assembly; W6′ > W5′, so that the first solid electrolyte layer provides sufficient ion channels for the first electrode sheet to receive lithium ions on the side away from the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0028] The embodiments of this application also provide a secondary battery, which includes any of the cells described in the above embodiments.

[0029] Embodiments of this application also provide an electronic device, which includes the secondary battery described in the above embodiments.

[0030] In the aforementioned battery cells, secondary batteries, and electronic devices, the first solid electrolyte layer provides physical support for the first and / or second bending sections, improving the structural stability at the corners of the battery cell. The first solid electrolyte layer also promotes lithium-ion desolvation through dielectricization, thereby providing ion channels at the corners of the battery cell. This reduces the risk of interface problems such as lithium plating or electrolyte wetting bridging at the corners due to insufficient electrolyte, thus improving the cycle performance of the battery cell. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the battery cell viewed along a third direction in one embodiment of this application.

[0032] Figure 2 This is a schematic diagram of the structure of the first electrode plate of the battery cell having a first solid electrolyte layer in one embodiment of this application.

[0033] Figure 3 This is a schematic diagram of the structure of the second and third solid electrolyte layers of the battery cell in one embodiment of this application.

[0034] Figure 4 This is a schematic diagram of the structure of the fourth solid electrolyte layer of the battery cell in one embodiment of this application.

[0035] Figure 5 This is a schematic diagram of a secondary battery assembled into an electronic device in one embodiment of this application.

[0036] Explanation of main component symbols

[0037] 100 cells

[0038] Secondary battery 200

[0039] Electronic device 300

[0040] Electrode assembly 10

[0041] First straight section 10A

[0042] First bend section 10B

[0043] Second straight section 10C

[0044] Second bend segment 10D

[0045] First Polar Film 11

[0046] First current collector 111

[0047] First active material layer 112

[0048] First area 1121

[0049] Second area 1122

[0050] Third area 1123

[0051] First solid electrolyte layer 113

[0052] Second solid electrolyte layer 114

[0053] Third solid electrolyte layer 115

[0054] Diaphragm 12

[0055] Second pole piece 13

[0056] Second current collector 131

[0057] Second active material layer 132

[0058] Fourth solid electrolyte layer 133

[0059] First Pole Ear 20

[0060] Second pole ear 30

[0061] First direction X

[0062] Second direction Y

[0063] Third direction Z

[0064] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0065] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0066] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.

[0067] When a value is considered "equal" to another value, it means that the two values ​​are equal within a set deviation range, which is within 5%. In other words, if at least one of the two values ​​fluctuates within the set deviation range, they are considered approximately equal even if their values ​​are not equal. Similarly, when a value is considered to have a "1:1" ratio with another value, it means that the two values ​​are equal within a set deviation range, which is within 5%. Again, if at least one of the two values ​​fluctuates within the set deviation range, they are considered equal in ratio even if their values ​​are not equal.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. The term "overlap" as used herein refers to the overlapping of the projected portions of two components or the coincidence of the projected portions of two components.

[0069] Embodiments of this application provide a battery cell, which includes an electrode assembly with its thickness direction in a first direction. The electrode assembly includes a first electrode, a separator, and a second electrode stacked and wound together. The electrode assembly includes a first straight section, a first bent section, a second straight section, and a second bent section connected in sequence. Viewed along a third direction, the first straight section and the second straight section are arranged opposite each other along the first direction, and the first bent section and the second bent section are arranged opposite each other along a second direction. The first direction, the second direction, and the third direction are perpendicular to each other. The first electrode includes a first current collector, a first active material layer, and a first solid electrolyte layer. Along the thickness direction of the first current collector, the first active material layer is disposed on at least one side surface of the first current collector. In at least a portion of the first electrode located in the first bent section and / or the second bent section, at least a portion of the surface of the first active material layer away from the first current collector is provided with the first solid electrolyte layer.

[0070] In the aforementioned battery cell, the first solid electrolyte layer provides physical support for the first and / or second bending sections, improving the structural stability at the cell's corners. The first solid electrolyte layer also promotes lithium-ion desolvation through dielectricization, thereby providing ion channels at the cell's corners. This reduces the risk of interface problems such as lithium plating or electrolyte wetting bridging due to insufficient electrolyte at the cell's corners, thus improving the cell's cycle performance.

[0071] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0072] Please see Figure 1 One embodiment of this application provides a battery cell 100. The battery cell 100 includes an electrode assembly 10, a first tab 20, and a second tab 30. The electrode assembly 10 is used to convert chemical energy into electrical energy. The first tab 20 has opposite polarities to the second tab 30. One end of the first tab 20 is connected to the electrode assembly 10, and the other end of the first tab 20 is configured to be electrically connected to an external circuit. One end of the second tab 30 is connected to the electrode assembly 10, and the other end of the second tab 30 is configured to be electrically connected to an external circuit.

[0073] The thickness direction of the electrode assembly 10 is the first direction X, the width direction of the electrode assembly 10 is the second direction Y, and the length direction of the electrode assembly 10 is the third direction Z. The first direction X, the second direction Y, and the third direction Z are perpendicular to each other.

[0074] Electrode assembly 10 includes a first electrode 11, a diaphragm 12, and a second electrode 13 stacked and wound together. A first tab 20 is connected to the first electrode 11, and a second tab 30 is connected to the second electrode 13.

[0075] The electrode assembly 10 includes a first straight section 10A, a first bent section 10B, a second straight section 10C, and a second bent section 10D connected in sequence. Viewed along a third direction Z, the first straight section 10A and the second straight section 10C are positioned opposite each other along a first direction X. The first bent section 10B and the second bent section 10D are positioned opposite each other along a second direction Y. The first bent section 10B and the second bent section 10D are located at the corners of the cell 100.

[0076] It should be noted that the specific location of the boundary between the straight and bent sections is determined using the testing reference standard: ISO 15708:2002 "Non-destructive testing - Radiation methods - Computed tomography". The specific testing method is as follows: After discharging the battery cell, place it on the X-ray computed tomography (CT) scanner stage. Near the boundary between the straight and bent sections, measure the angle of the outer contour of the electrode assembly every 1 mm along the direction from the straight section to the bent section. When the angular deviation between the angle of the outer contour of the electrode assembly and the width direction of the electrode assembly is equal to 1°, this is defined as the boundary point between the straight and bent sections. The extension line passing through the boundary point between the straight and bent sections and extending along the length direction of the electrode assembly is defined as the boundary line between the straight and bent sections.

[0077] Please continue reading. Figure 1 The first electrode 11 includes a first current collector 111, a first active material layer 112, and a first solid electrolyte layer 113. Along the thickness direction of the first current collector 111, the first active material layer 112 is disposed on at least one side surface of the first current collector 111. In at least a portion of the first electrode 11 located in the first bending section 10B and / or the second bending section 10D, at least a portion of the surface of the first active material layer 112 away from the surface of the first current collector 111 is provided with the first solid electrolyte layer 113.

[0078] The first solid electrolyte layer 113 provides physical support for the first bending segment 10B and / or the second bending segment 10D, improving the structural stability at the corner of the cell 100. The first solid electrolyte layer 113 also promotes lithium-ion desolvation through dielectricization, thereby providing ion channels at the corner of the cell 100. This reduces the risk of interface problems such as lithium plating or electrolyte wetting bridging at the corner of the cell 100 due to insufficient electrolyte, thus improving the cycle performance of the cell 100.

[0079] Please refer to the following: Figure 1 and Figure 2In some embodiments, along the third direction Z, the ratio of the length of the first solid electrolyte layer 113 to the length of the first active material layer 112 containing the first solid electrolyte layer 113 is A1, where 60% ≤ A1 ≤ 100%. When A1 is too small (less than 60%), other areas of the first active material layer 112 are prone to interface problems such as lithium plating or electrolyte wetting bridging due to insufficient electrolyte, resulting in reduced cycle performance of the cell 100. When A1 is too large (less than 100%), the first solid electrolyte layer 113 is prone to protruding beyond the first active material layer 112, resulting in wasted space and reduced energy density of the cell 100. By limiting A1 to 60% ≤ A1 ≤ 100%, the risk of interface problems such as lithium plating or electrolyte wetting bridging at the corners of the cell 100 due to insufficient electrolyte is reduced, improving the cycle performance of the cell 100 and reducing the wasted space caused by the first solid electrolyte layer 113 protruding beyond the first active material layer 112, thereby increasing the energy density of the cell 100.

[0080] Optionally, A1 can be any value within the range of 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, and 60%≤A1≤100%.

[0081] The lengths of the first solid electrolyte layer 113 and the first active material layer 112 are obtained by disassembling the electrode assembly 10, removing the first electrode 11, flattening the first electrode 11, and then measuring it with a ruler.

[0082] Please continue reading. Figure 2 In some embodiments, when 60% ≤ A1 < 100%, the first active material layer 112 includes a first region 1121, a second region 1122, and a third region 1123 sequentially disposed along the third direction Z. The first solid electrolyte layer 113 covers the second region 1122, while the first region 1121 and the third region 1123 are not provided with the first solid electrolyte layer 113. Along the third direction Z, the length of the first region 1121 is D1, and the length of the third region 1123 is D2. D1 and D2 are adjusted according to the diffusion difficulty of the electrolyte.

[0083] Specifically, along the third direction Z, when the difficulty of electrolyte wetting at the top of the corner of cell 100 is higher than that at the bottom of the corner (e.g., when the top of cell 100 is facing upwards and the bottom is facing downwards), by setting D1 < D2, the risk of interface problems such as lithium plating or electrolyte wetting breakage at the top of the corner of cell 100 due to insufficient electrolyte is reduced, thereby improving the cycle performance of cell 100. Similarly, along the third direction Z, when the difficulty of electrolyte wetting at the bottom of the corner of cell 100 is higher than that at the top of the corner (e.g., when the bottom of cell 100 is facing upwards and the top is facing downwards), by setting D1 > D2, the risk of interface problems such as lithium plating or electrolyte wetting breakage at the bottom of the corner of cell 100 due to insufficient electrolyte is reduced, thereby improving the cycle performance of cell 100. Along the third direction Z, when there is no significant difference between the difficulty of wetting the electrolyte at the top of the corner of the cell 100 and the difficulty of wetting the electrolyte at the bottom of the corner of the cell 100, D1 = D2.

[0084] Please continue reading. Figure 1 and Figure 2 In some embodiments, in at least a portion of the first electrode 11 located in the first bending segment 10B or the second bending segment 10D, along the winding direction of the first electrode 11, the ratio of the width of the first solid electrolyte layer 113 to the width of the first active material layer 112 containing the first solid electrolyte layer 113 is B1, where 50% ≤ B1 ≤ 100%. When B1 is too small (less than 60%), other areas of the first active material layer 112 are prone to interface problems such as lithium plating or electrolyte wetting bridging due to insufficient electrolyte, resulting in a decrease in the cycle performance of the cell 100. When B1 is too large (greater than 100%), the first solid electrolyte layer 113 is prone to protrude beyond the first active material layer 112, resulting in wasted space and a decrease in the energy density of the cell 100. By limiting B1 to 100% to 50%, the risk of interface problems such as lithium plating or electrolyte wetting breakage at the corners of the cell 100 due to insufficient electrolyte is reduced, thereby improving the cycle performance of the cell 100. It also helps to reduce the space waste caused by the first solid electrolyte layer 113 protruding from the first active material layer 112 and improve the energy density of the cell 100.

[0085] Optionally, B1 can be any value within the range of 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, and any other value within the range of 50%≤B1≤100%.

[0086] The width of the first solid electrolyte layer 113 is obtained by disassembling the electrode assembly 10, removing the first electrode 11, flattening the first electrode 11, and then measuring it with a ruler. The width of the first active material layer 112 is the width of the first electrode 11 located in the first bending section 10B or the second bending section 10D. After defining the range of the first bending section 10B and the second bending section 10D using the method mentioned above, the electrode assembly 10 is disassembled, the first electrode 11 is removed and flattened, and the width of each layer of the first electrode 11 located in the first bending section 10B or the second bending section 10D is measured with a ruler to obtain the width of each layer of the first active material layer 112 located in the first bending section 10B or the second bending section 10D.

[0087] Please continue reading. Figure 1 In some embodiments, the first solid electrolyte layer 113 is coated onto the surface of the first active material layer 112 by extrusion spraying. The coating weight per unit area of ​​the first solid electrolyte layer 113 is W1, where 0.5 mg / cm² ≤ W1 ≤ 5 mg / cm². When W1 is too small (less than 0.5 mg / cm²), the first solid electrolyte layer 113 is easily made too thin, reducing lithium-ion transport efficiency. When W1 is too large (greater than 5 mg / cm²), the first solid electrolyte layer 113 is easily made too thick, leading to a decrease in energy density and also lengthening the lithium-ion transport path, increasing material and production costs. By limiting W1 to 0.5 mg / cm² ≤ W1 ≤ 5 mg / cm², the lithium-ion transport efficiency and the energy density of the cell 100 are improved, and the lithium-ion transport path is shortened, reducing material and production costs.

[0088] Optionally, W1 can be any value within the range of 0.5 mg / cm², 1 mg / cm², 1.5 mg / cm², 2 mg / cm², 2.5 mg / cm², 3 mg / cm², 3.5 mg / cm², 4 mg / cm², 4.5 mg / cm², 5 mg / cm², and any other value within the range of 0.5 mg / cm² ≤ W1 ≤ 5 mg / cm².

[0089] The coating weight W1 per unit area of ​​the first solid electrolyte layer 113 can be measured in the following ways: 1) Discharge the secondary battery 200 to 0 SOC% at a test temperature of 25°C, disassemble it to obtain the first electrode 11, clean it with dimethyl carbonate (DMC) and then dry it; 2) Cut a first electrode 11 with an area of ​​S2 from the first electrode 11 of the first bent section 10B as a sample of the first bent section 10B, wherein the area of ​​the first current collector 111, the area of ​​the first active material layer 112 and the area of ​​the first solid electrolyte layer 113 in this sample are all S2, weigh it using a balance, and record the weight as W. 总Observing the cross-section of the first bent segment 10B sample under a scanning electron microscope, a clear boundary line between the first active material layer 112 and the first solid electrolyte layer 113 can be observed. The thickness d1 of the first active material layer 112 is obtained by measuring the cross-section of the sample using a scanning electron microscope; 3) Use a scraper to scrape off the first solid electrolyte layer 113 and part of the first active material layer 112 located on the surface of the first active material layer 112. The scraping area needs to exceed the boundary between the first active material layer 112 and the first solid electrolyte layer 113. The boundary is defined to ensure that the first solid electrolyte layer 113 is completely scraped off. The remaining first active material layer 112 and the first current collector 111 are weighed and recorded as W′. The remaining thickness d2 of the first active material layer 112 is observed and measured under a scanning electron microscope. The remaining first active material layer 112 is then washed away with the solvent N-methylpyrrolidone (NMP), dried, and the weight of the first current collector 111 is recorded as W0. The compaction density ρ of the first active material layer 112 at the first bend 10B is calculated. 1= (W′-W0) / (d2×S2); 4) Calculate the coating weight per unit area of ​​the first solid electrolyte layer 113 using the following formula: W=[(W 总 -W0)-ρ1×S2×d1] / S2.

[0090] Furthermore, 1 mg / cm² ≤ W1 ≤ 3 mg / cm², in order to further improve the lithium-ion transport efficiency and the energy density of cell 100, and further facilitate the shortening of the lithium-ion transport path, thereby reducing material costs and production costs.

[0091] In some embodiments, the first solid electrolyte layer 113 includes a first adhesive, the mass ratio of the first adhesive to the mass of the first solid electrolyte layer 113 being W2, where 1% ≤ W2 ≤ 10%. When W2 is too small (less than 1%), the peel strength between the first solid electrolyte layer 113 and the first active material layer 112 is weak. When W2 is too large (greater than 10%), excessive adhesive can clog the pores on the surface of the first active material layer 112, causing lithium plating and reducing the cycle performance of the cell 100. By limiting W2 to 1% ≤ W2 ≤ 10%, the peel strength between the first solid electrolyte layer 113 and the first active material layer 112 is improved, and the cycle performance of the cell 100 is also improved.

[0092] Optionally, W2 can be any value within the range of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, and any other value within the range of 1%≤W2≤10%.

[0093] In some embodiments, the material of the first adhesive includes at least one of PVDF (polyvinylidene fluoride), PAA (polyacrylic acid), and CMC (carboxymethyl cellulose).

[0094] In some embodiments, the first solid electrolyte layer 113 includes a first conductive agent, the material of which includes at least one of carbon nanotubes, carbon black, conductive graphite, and graphene.

[0095] In some embodiments, the mass ratio of the first conductive agent to the mass of the first solid electrolyte layer 113 is 0.1% to 3%.

[0096] It should be noted that in the preparation process of the battery cell 100, a slurry for the first solid electrolyte layer 113 is first prepared, and then the slurry for the first solid electrolyte layer 113 is coated onto the surface of the first active material layer 112 by extrusion spraying. The slurry for the first solid electrolyte layer 113 includes a first solid electrolyte, a solvent, a first binder, and a first conductive agent. The material of the first solid electrolyte includes at least one of organic solid electrolyte and inorganic solid electrolyte; wherein, the organic solid electrolyte includes block copolymers, the block copolymers include conductive polymers and lithium-conducting polymers, the conductive polymers include at least one of pyrrole, aniline, thiophene, polyacetylene, p-phenylenediamine terephthalamide, or 3,4-ethylenedioxythiophene, and the lithium-conducting polymers include at least one of polyethylene oxide, polyethylene glycol, polypropylene oxide, poly(ethylene glycol) acrylate, or poly(ethylene glycol) methacrylate; the inorganic solid electrolyte includes at least one of oxide solid electrolyte and sulfide solid electrolyte, the oxide solid electrolyte including lithium aluminum titanium phosphate (LATP[Li 1.4 Al 0.4 Ti 1.6 (PO4)3]), lithium aluminum germanium phosphate (LAGP[Li 1.5 Al 0.5 Ge 1.5 (PO4)3]), Lithium lanthanum zirconium oxide (Li7La3Zr2O) 12 ), lithium lanthanum zirconium tantalum oxide, lithium zinc germanium oxide (LZGO[Li 14 At least one of ZnGeO4] or lithium lanthanum titanate, the sulfide solid electrolyte includes lithium silver sulfide germanium (LGPS, Li 10 GeP2S 12The solvent includes at least one of lithium sulfide phosphorus (LPS, Li2S-P2S5). The solvent includes N-methylpyrrolidone. The first solid electrolyte layer 113 is formed after the slurry of the first solid electrolyte layer 113 is cured. Wherein, W2 is the ratio of the mass of the first binder in the cured first solid electrolyte layer 113 to the mass of the first solid electrolyte layer 113. The method for measuring W2 is as follows: a portion of the first solid electrolyte layer 113 is scraped off using a scraper on the first electrode 11 and the scraped-off first solid electrolyte layer 113 is collected. The mass m1 of the scraped-off first solid electrolyte layer 113 is weighed using an electronic balance; then, the scraped-off first solid electrolyte layer 113 is dissolved using N-methylpyrrolidone to prepare a solid electrolyte solution with a mass concentration of 0.5%. The absorbance of the solid electrolyte solution is measured using an infrared spectrometer and compared with the absorbance of a standard solution to calculate the mass m2 of the first binder in the solution; the mass percentage of the first binder in the first solid electrolyte layer 113, W2 = m2 / m1 × 100%.

[0097] Please continue reading. Figure 1 and Figure 2 In some embodiments, the peel strength between the first solid electrolyte layer 113 and the first active material layer 112 is S1, where 0.2 N / m ≤ S1 ≤ 5 N / m. When S1 is too small (less than 0.2 N / m), the first solid electrolyte layer 113 is prone to powder shedding and detachment, leading to a decrease in the cycle performance of the cell 100. When S1 is too large (greater than 5 N / m), the mechanical stress between the first solid electrolyte layer 113 and the first active material layer 112 is prone to increase, leading to deformation of the electrode assembly 10. By limiting S1 to 5 N / m (0.2 N / m ≤ S1 ≤ 5 N / m), the cycle performance of the cell 100 is improved, and the structural stability of the electrode assembly 10 is also improved.

[0098] Optionally, S1 can be any value within the range of 0.2 N / m, 0.5 N / m, 1 N / m, 1.5 N / m, 2 N / m, 2.5 N / m, 3 N / m, 3.5 N / m, 4 N / m, 4.5 N / m, 5 N / m, and any other value within the range of 0.2 N / m ≤ S1 ≤ 5 N / m.

[0099] Furthermore, 1N / m≤S1≤3N / m is used to further improve the cycle performance of the cell 100 and further improve the structural stability of the electrode assembly 10.

[0100] Please see Figure 3In some embodiments, the first electrode 11 includes a second solid electrolyte layer 114 and a third solid electrolyte layer 115. In the first electrode 11 located in the first straight section 10A, the second solid electrolyte layer 114 is provided in a portion of the surface of the first active material layer 112 away from the surface of the first current collector 111. In the first electrode 11 located in the second straight section 10C, the third solid electrolyte layer 115 is provided in a portion of the surface of the first active material layer 112 away from the surface of the first current collector 111. The second solid electrolyte layer 114 and the third solid electrolyte layer 115 can promote the desolvation of lithium ions through dielectricization, thereby expanding the range of ion channels in conjunction with the first solid electrolyte layer 113, further reducing the risk of interface problems such as lithium plating or electrolyte wetting bridging at the corners of the cell 100 due to insufficient electrolyte, and thus improving the cycle performance of the cell 100.

[0101] In some embodiments, the first bending section 10B includes an N1 layer first electrode 11. In the first electrode 11 of the 1 / 3 N1 layer located inside the first bending section 10B, the two ends of the first solid electrolyte layer 113 are respectively connected to the second solid electrolyte layer 114 and the third solid electrolyte layer 115 along the winding direction of the first electrode 11. Specifically, during the cycling process of the cell 100, the electrolyte wetting effect of the inner electrode of the cell 100 is worse than that of the outer electrode. That is, the first electrode 11 located inside the first bending section 10B is more prone to electrolyte deficiency than the first electrode 11 located outside the first bending section 10B. By connecting the two ends of the first solid electrolyte layer 113 in the first electrode 11 of the 1 / 3N1 layer located inside the first bending section 10B to the second solid electrolyte layer 114 and the third solid electrolyte layer 115 respectively, the range of ion channels inside the first bending section 10B is expanded in a targeted manner, reducing the risk of interface problems such as lithium plating or electrolyte wetting bridging caused by insufficient electrolyte inside the first bending section 10B, thereby improving the cycle performance of the cell 100.

[0102] Optionally, N1 = 3, 6, 9, 12, 15, etc. It should be noted that when 1 / 3N1 is not an integer, the integer less than and closest to 1 / 3N1 is used as a reference. For example, if N1 = 4, then the two ends of the first solid electrolyte layer 113 are connected to the second solid electrolyte layer 114 and the third solid electrolyte layer 115 respectively in the first electrode 11 located inside the first bending section 10B.

[0103] Please continue reading. Figure 3In some embodiments, the second bending segment 10D includes an N2 layer first electrode 11. In the first electrode 11 of the 1 / 3 N2 layer located inside the second bending segment 10D, the two ends of the first solid electrolyte layer 113 are respectively connected to the second solid electrolyte layer 114 and the third solid electrolyte layer 115 along the winding direction of the first electrode 11. Specifically, during the cycling process of the cell 100, the electrolyte wetting effect of the inner electrode of the cell 100 is worse than that of the outer electrode. That is, the first electrode 11 located inside the second bending segment 10D is more prone to electrolyte deficiency than the first electrode 11 located outside the second bending segment 10D. By connecting the two ends of the first solid electrolyte layer 113 in the first electrode 11 of the 1 / 3 N2 layer located inside the second bending section 10D to the second solid electrolyte layer 114 and the third solid electrolyte layer 115 respectively, the range of ion channels inside the second bending section 10D is expanded in a targeted manner. This reduces the risk of interface problems such as lithium plating or electrolyte wetting bridging caused by insufficient electrolyte in the first electrode 11 inside the second bending section 10D, thereby improving the cycle performance of the cell 100.

[0104] Optionally, N2 = 3, 6, 9, 12, 15, etc. It should be noted that when 1 / 3N2 is not an integer, the integer less than and closest to 1 / 3N2 is used as a reference. For example, if N2 = 7, then in the two layers of first electrode 11 located inside the second bending segment 10D, the two ends of the first solid electrolyte layer 113 are respectively connected to the second solid electrolyte layer 114 and the third solid electrolyte layer 115.

[0105] Please continue reading. Figure 3 In some embodiments, the length of the second solid electrolyte layer 114 along the second direction Y is L1, where 0.5mm ≤ L1 ≤ 2mm. When L1 is too small (less than 0.5mm), the range of ion channels provided by the second solid electrolyte layer 114 is too narrow, resulting in reduced cycle performance of the cell 100. Furthermore, due to the relatively small winding radius of the inner ring, the first solid electrolyte layer 113 located in the first bending segment 10B or the second bending segment 10D of the 1 / 3N1 layer or 1 / 3N2 layer of the inner ring is prone to detachment. The provision of the second solid electrolyte layer 114 helps to increase the overlapping area between the solid electrolyte layer and the active material layer, reducing the risk of solid electrolyte layer detachment. When the length L1 of the second solid electrolyte layer 114 is too small (less than 0.5mm), the risk of solid electrolyte layer detachment increases, and the detachment of the solid electrolyte layer may cause the falling particles to puncture the diaphragm, leading to a short circuit. When L1 is too large (greater than 2 mm), the second solid electrolyte layer 114 occupies a large space in the first direction X, resulting in wasted space and a decrease in the energy density of the cell 100. By limiting L1 to 0.5 mm ≤ L1 ≤ 2 mm, it is beneficial to improve the cycle performance and energy density of the cell 100.

[0106] Optionally, L1 can be any value within the range of 0.5mm, 1mm, 1.5mm, 2mm, and 0.5mm≤L1≤2mm.

[0107] Furthermore, 1mm≤L1≤1.5mm is beneficial for further improving the cycle performance and energy density of cell 100.

[0108] Please continue reading. Figure 3 In some embodiments, the length of the third solid electrolyte layer 115 along the second direction Y is L2, where 0.5mm ≤ L2 ≤ 2mm. When L2 is too small (less than 0.5mm), the range of ion channels provided by the third solid electrolyte layer 115 is too narrow, resulting in reduced cycle performance of the cell 100. Furthermore, due to the relatively small winding radius of the inner ring, the first solid electrolyte layer 113 located in the first bending segment 10B or the second bending segment 10D of the 1 / 3N1 layer or 1 / 3N2 layer of the inner ring is prone to detachment. The provision of the third solid electrolyte layer 115 helps to increase the overlapping area between the solid electrolyte layer and the active material layer, reducing the risk of solid electrolyte layer detachment. When the length L1 of the third solid electrolyte layer 115 is too small (less than 0.5mm), the risk of solid electrolyte layer detachment increases, and the detachment of the solid electrolyte layer may cause the falling particles to puncture the diaphragm, leading to a short circuit. When L2 is too large (greater than 2 mm), the third solid electrolyte layer 115 tends to occupy a large space in the first direction X, resulting in wasted space and a decrease in the energy density of the cell 100. By limiting L2 to 0.5 mm ≤ L2 ≤ 2 mm, it is beneficial to improve the cycle performance and energy density of the cell 100.

[0109] Optionally, L2 can be any value within the range of 0.5mm, 1mm, 1.5mm, 2mm, and 0.5mm≤L2≤2mm.

[0110] Furthermore, 1mm≤L2≤1.5mm is beneficial for further improving the cycle performance and energy density of cell 100.

[0111] The test methods for L1 and L2 are as follows: disassemble the electrode assembly 10, remove the first electrode 11, flatten the electrode, and use a ruler to measure the length of the second solid electrolyte layer 114 located on the first straight section 10A to obtain L1, and use a ruler to measure the length of the third solid electrolyte layer 115 located on the second straight section 10C to obtain L2.

[0112] Please continue reading. Figure 1In some embodiments, the first electrode 11 is a negative electrode and the second electrode 13 is a positive electrode. The first solid electrolyte layer 113 disposed on the first electrode 11 can better improve the corner interface, thereby achieving better improvement in corner expansion and increasing the cycle life of the battery cell.

[0113] In some embodiments, the second electrode 13 includes a second current collector 131, a second active material layer 132, and a fourth solid electrolyte layer 133. Along the thickness direction of the second current collector 131, the second active material layer 132 is disposed on at least one side surface of the second current collector 131. In at least a portion of the second electrode 13 located in the first bend segment 10B and / or the second bend segment 10D, at least a portion of the surface of the second active material layer 132 away from the second current collector 131 is provided with the fourth solid electrolyte layer 133. The fourth solid electrolyte layer 133 can provide physical support for the first bend segment 10B and / or the second bend segment 10D, improving the structural stability at the corner of the cell 100. The fourth solid electrolyte layer 133 can also promote lithium-ion desolvation through dielectricization, thereby providing ion channels at the corner of the cell 100, reducing the risk of interface problems such as lithium plating or electrolyte wetting bridging at the corner of the cell 100 due to insufficient electrolyte, and thus improving the cycle performance of the cell 100.

[0114] In some embodiments, in the same layer of the second electrode 13 located in the first bending section 10B, on the side facing the winding center of the electrode assembly 10, the ratio of the area of ​​the fourth solid electrolyte layer 133 to the area of ​​the second active material layer 132 containing the fourth solid electrolyte layer 133 is C1; on the side away from the winding center of the electrode assembly 10, the ratio of the area of ​​the fourth solid electrolyte layer 133 to the area of ​​the second active material layer 132 containing the fourth solid electrolyte layer 133 is C2; C1 > C2. Specifically, at the corner of the cell 100, the second electrode 13 covers the first electrode 11. On the side of the second electrode 13 facing the winding center, the winding radius of the second electrode 13 is larger than that of the first electrode 11. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the first electrode 11 and the second electrode 13 is insufficient, which increases the risk of interface problems such as lithium plating. By limiting C1 to C2, the fourth solid electrolyte layer 133 provides sufficient ion channels for the first electrode 11 to receive lithium ions on the side facing the winding center of the electrode assembly 10, thereby reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell 100.

[0115] In some embodiments, in the same layer of the second electrode 13 located in the second bending section 10D, on the side facing the winding center of the electrode assembly 10, the ratio of the area of ​​the fourth solid electrolyte layer 133 to the area of ​​the second active material layer 132 containing the fourth solid electrolyte layer 133 is C1′; on the side away from the winding center of the electrode assembly 10, the ratio of the area of ​​the fourth solid electrolyte layer 133 to the area of ​​the second active material layer 132 containing the fourth solid electrolyte layer 133 is C2′; C1′>C2′. Specifically, at the corner of the cell 100, the second electrode 13 covers the first electrode 11. On the side of the second electrode 13 facing the winding center, the winding radius of the second electrode 13 is larger than that of the first electrode 11. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the first electrode 11 and the second electrode 13 is insufficient, which increases the risk of interface problems such as lithium plating. By limiting C1′ to C2′, the first solid electrolyte layer 113 provides sufficient ion channels for the second electrode 13 to receive lithium ions on the side facing the winding center of the electrode assembly 10, thereby reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell 100.

[0116] In the above embodiments, the measurement methods for C1, C2, C1′, and C2′ are as follows: The electrode assembly 10 is disassembled, the second electrode 13 is removed and flattened, and the length and width of the fourth solid electrolyte layer 133 facing the winding center are measured using a ruler. Their product is then calculated to obtain the area of ​​the fourth solid electrolyte layer 133. Similarly, the length and width of the corresponding second electrode 13 in the first bending segment 10B or the second bending segment 10D are measured using a ruler, and their product is calculated to obtain the area of ​​the corresponding second electrode 13 in the first bending segment 10B or the second bending segment 10D. Since there is no area in the second electrode 13 in the first bending segment 10B and the second bending segment 10D where the second active material layer 13 is not coated, the area of ​​the corresponding second electrode 13 in the first bending segment 10B or the second bending segment 10D is equivalent to the area of ​​the second active material layer 132 in the first bending segment 10B or the second bending segment 10D. The area of ​​the fourth solid electrolyte layer 133 is divided by the area of ​​the second active material layer 132 to obtain C1 or C1′. The measurement and calculation methods for C2 or C2′ are similar to those for C1 or C1′.

[0117] In some embodiments, in the same layer of the second electrode 13 located in the first bending section 10B, the coating weight per unit area of ​​the fourth solid electrolyte layer 133 is W3 on the side facing the winding center of the electrode assembly 10; and W4 on the side away from the winding center of the electrode assembly 10; W3 > W4. Specifically, at the corner of the cell 100, the second electrode 13 covers the first electrode 11. On the side of the second electrode 13 facing the winding center, the winding radius of the second electrode 13 is larger than that of the first electrode 11. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the first electrode 11 and the second electrode 13 is insufficient, which increases the risk of interface problems such as lithium plating. By limiting W3 to W4, the fourth solid electrolyte layer 133 provides sufficient ion channels for the first electrode 11 to receive lithium ions on the side facing the winding center of the electrode assembly 10, thereby reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell 100.

[0118] In some embodiments, in the same layer of the second electrode 13 located in the second bending section 10D, the coating weight per unit area of ​​the fourth solid electrolyte layer 133 is W3′ on the side facing the winding center of the electrode assembly 10; and W4′ on the side away from the winding center of the electrode assembly 10; W3′>W4′. Specifically, at the corner of the cell 100, the second electrode 13 covers the first electrode 11. On the side of the second electrode 13 facing the winding center, the winding radius of the second electrode 13 is larger than that of the first electrode 11. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the first electrode 11 and the second electrode 13 is insufficient, which increases the risk of interface problems such as lithium plating. By limiting W3′ to W4′, the fourth solid electrolyte layer 133 provides sufficient ion channels for the first electrode 11 to receive lithium ions on the side facing the winding center of the electrode assembly 10, thereby reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell 100.

[0119] The measurement methods for W3, W4, W3′, and W4′ mentioned above are the same as the measurement method for W1 mentioned earlier.

[0120] Please continue reading. Figure 4In some embodiments, in the same layer of the first electrode 11 located in the first bending section 10B, on the side facing the winding center of the electrode assembly 10, the ratio of the area of ​​the first solid electrolyte layer 113 to the area of ​​the first active material layer 112 containing the first solid electrolyte layer 113 is C3; on the side away from the winding center of the electrode assembly 10, the ratio of the area of ​​the first solid electrolyte layer 113 to the area of ​​the first active material layer 112 containing the first solid electrolyte layer 113 is C4; C4 > C3. Specifically, at the corner of the cell 100, the first electrode 11 covers the second electrode 13. On the side of the first electrode 11 facing the winding center, the winding radius of the first electrode 11 is larger than that of the second electrode 13. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the first electrode 11 and the second electrode 13 is larger, reducing the risk of interface problems such as lithium plating. By limiting C4 to C3, the first solid electrolyte layer 113 provides sufficient ion channels for the first electrode 11 to receive lithium ions on the side away from the winding center of the electrode assembly 10, thereby reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell 100.

[0121] In some embodiments, in the same layer of the first electrode 11 located in the second bending segment 10D, on the side facing the winding center of the electrode assembly 10, the ratio of the area of ​​the first solid electrolyte layer 113 to the area of ​​the first active material layer 112 containing the first solid electrolyte layer 113 is C3′; on the side away from the winding center of the electrode assembly 10, the ratio of the area of ​​the first solid electrolyte layer 113 to the area of ​​the first active material layer 112 containing the first solid electrolyte layer 113 is C4′; C4′>C3′. Specifically, at the corner of the cell 100, the first electrode 11 covers the second electrode 13. On the side of the first electrode 11 facing the winding center, the winding radius of the first electrode 11 is larger than that of the second electrode 13. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the first electrode 11 and the second electrode 13 is larger, and the risk of interface problems such as lithium plating is lower. By limiting C4′ to C3′, the first solid electrolyte layer 113 provides sufficient ion channels for the first electrode 11 to receive lithium ions on the side away from the winding center of the electrode assembly 10, thereby reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell 100.

[0122] The measurement and calculation methods for C3, C4, C3′ and C4′ mentioned above are the same as those for C1, C2, C1′ and C2′.

[0123] In some embodiments, in the same layer of the first electrode 11 located in the first bending section 10B, the coating weight per unit area of ​​the first solid electrolyte layer 113 is W5 on the side facing the winding center of the electrode assembly 10; and W6 on the side away from the winding center of the electrode assembly 10; W6 > W5. Specifically, at the corner of the cell 100, the first electrode 11 covers the second electrode 13. On the side of the first electrode 11 facing the winding center, the winding radius of the first electrode 11 is larger than that of the second electrode 13. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the first electrode 11 and the second electrode 13 is larger, and the risk of interface problems such as lithium plating is lower. By limiting W6 to W5, the first solid electrolyte layer 113 provides sufficient ion channels for the first electrode 11 to receive lithium ions on the side away from the winding center of the electrode assembly 10, thereby reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell 100.

[0124] In some embodiments, in the same layer of the first electrode 11 located in the second bending section 10D, the coating weight per unit area of ​​the first solid electrolyte layer 113 is W5′ on the side facing the winding center of the electrode assembly 10; and W6′ on the side away from the winding center of the electrode assembly 10; W6′ > W5′. Specifically, at the corner of the cell 100, the first electrode 11 covers the second electrode 13. On the side of the first electrode 11 facing the winding center, the winding radius of the first electrode 11 is larger than that of the second electrode 13. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the first electrode 11 and the second electrode 13 is larger, and the risk of interface problems such as lithium plating is lower. By limiting W6′ to W5′, the first solid electrolyte layer 113 provides sufficient ion channels for the first electrode 11 to receive lithium ions on the side away from the winding center of the electrode assembly 10, thereby reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell 100.

[0125] The measurement methods for W5, W6, W5′, and W6′ are the same as those for W1 mentioned earlier.

[0126] Please see Figure 5 An embodiment of this application also provides a secondary battery 200, which includes the cell 100 in any of the above embodiments. After the secondary battery 200 is discharged, the active material can be activated by charging so that it can continue to be used.

[0127] Please continue reading. Figure 5An embodiment of this application also provides an electronic device 300, which includes the secondary battery 200 in any of the above embodiments. Optionally, the electronic device 300 may be a vehicle, mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, or power tool, etc.

[0128] The following describes the specific implementation of the battery cell 100 in the embodiments and comparative examples.

[0129] Cell cycle testing:

[0130] At a test temperature of 25°C, the secondary battery 200 was left to stand for 30 minutes and then subjected to stepped charging according to the following steps: (a) 2.0C constant current charging to 4.23V, constant voltage charging to 1.8C; (b) 1.8C constant current charging to 4.3V, constant voltage charging to 1.4C; (c) 1.4C constant current charging to 4.4V, constant voltage charging to 1.0C; (d) 1.0C constant current charging to 4.5V, constant voltage charging to 0.05C. After standing for 10 minutes, the battery was discharged according to the following steps: 1C DC discharge to 3V. The above charge-discharge process constitutes one cycle, which was repeated 1000 times. 20 cells were tested in each comparative and example group.

[0131] (1) The initial cell thickness and the cell thickness after 1000 cycles were measured by a PPG thickness tester, and the thickness expansion rate was calculated.

[0132] The thickness expansion rate of each cell = [(cell thickness after 1000 cycles - initial cell thickness) / initial cell thickness] × 100%;

[0133] The thickness expansion rate in each comparative example or embodiment is the average thickness expansion rate of the 20 cells in each group.

[0134] (2) Calculate the capacity retention rate of the battery cell;

[0135] Capacity retention rate of each cell = Discharge capacity after 1000 cycles / Initial discharge capacity × 100%.

[0136] The capacity retention rate in each comparative example or embodiment is the average of the capacity retention rates of the 20 cells in each group.

[0137] (3) Disassemble the battery cell and observe whether grayish-white lithium plating appears at the corner of the battery cell. Record the number of lithium platings at the corner of the negative electrode in each of the 20 battery cells in the comparative example or embodiment as X1. Then the lithium plating rate at the corner of the negative electrode in each comparative example or embodiment is X1 / 20.

[0138] (4) Calculate the volumetric energy density of the cell = plateau voltage × first discharge capacity / (initial cell length × initial cell width × initial cell thickness).

[0139] (5) Perform high-voltage insulation testing (Hipot test) on the battery cells and calculate the pass rate. Hipot test is an insulation resistance test. The test method is to detect the leakage current generated by the electrode assembly 10 under the test voltage output by the high voltage generator, and then calculate the resistance value = test voltage / leakage current. The calculated resistance value is compared with the set judgment resistor. If the detected resistance value is greater than or equal to the preset value, the product under test is judged to pass the test (OK); if the detected resistance value is less than the preset value, the test voltage is cut off instantly and the product under test is judged to fail the test (NG). The preset value of the judgment resistor in this test is 5mΩ. When the resistance value is less than 5mΩ, it means that it can conduct but the resistance value is too small, there is a short circuit point, and it is judged to be NG; when the resistance value is greater than or equal to 5mΩ, it is judged to be OK. 20 battery cells are tested in each set of embodiments. The number of battery cells that pass the test is X2, and the pass rate is X2 / 100.

[0140] Example 1:

[0141] A type of battery cell 100, with an initial thickness of 1.4mm at 50% SOC, a length of 110mm, and a width of 50mm, is assembled as follows:

[0142] (1) Preparation of negative electrode sheet (corresponding to the first electrode sheet): A copper foil with a thickness of 6 μm is provided as the negative electrode current collector; artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) are mixed in a weight ratio of 96:1.5:2.5, deionized water is added as a solvent, and a slurry with a weight percentage of 50 wt% is prepared and stirred evenly; solid electrolyte material lithium aluminum titanium phosphate, first binder polyvinylidene fluoride, and first conductive agent carbon nanotube are dissolved in solvent N-methylpyrrolidone in a weight percentage ratio of 94%:5%:1% to prepare a solid electrolyte slurry and stirred evenly; the two slurries are simultaneously coated on one surface of the copper foil by extrusion spraying using two nozzles, and then dried at 110°C to obtain a negative electrode sheet with a single-sided coating of negative electrode active material layer. When preparing a double-sided coated negative electrode sheet, the above steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided coating of negative electrode active material layer. Then, the coated electrode sheet is subjected to a cold pressing process. The thickness of the single-sided negative electrode active material layer of the flat section after cold pressing is 105 μm. A portion of the negative electrode active material layer is etched away using a laser to expose the negative electrode current collector below the negative electrode active material layer. Negative electrode tabs are welded onto the exposed negative electrode current collector. The material of the negative electrode tabs is copper. (2) Preparation of positive electrode sheet (corresponding to the second electrode sheet): Provide an aluminum foil with a thickness of 8 μm as the positive electrode current collector; attach foam adhesive to the position where the positive electrode tab needs to be welded on the positive electrode current collector; mix the positive electrode active material lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) in a weight ratio of 97.5:1.0:1.5, add N-methylpyrrolidone (NMP) as a solvent, and prepare a slurry with a solid content of 75 wt%, and stir evenly. Coat the slurry evenly on one surface of the aluminum foil, and then dry it at 90°C to obtain a positive electrode sheet with a single-sided coating of positive electrode active material. When preparing a double-sided coated positive electrode sheet, the above coating steps are repeated on the other surface of the aluminum foil. The coated electrode sheet is then subjected to a cold pressing process, and the thickness of the single-sided positive active material layer after cold pressing is 95μm. Heating is then used to remove the foam to expose the positive current collector covered by the foam. Positive electrode tabs are then welded onto the exposed positive current collector. The positive electrode tabs are made of aluminum.

[0143] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC=30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0144] (4) Preparation of the isolation membrane: A 7-micron thick porous polyethylene polymer film was used as the isolation membrane.

[0145] (5) Electrode assembly fabrication: The positive electrode sheet, the separator, and the negative electrode sheet are wound together. After winding, the electrode assembly has 24 layers of positive and negative electrode sheets, of which 12 layers of positive and negative electrode sheets are located in the first bending section and the second bending section. The first solid electrolyte layer is disposed on the surface of the negative electrode active material layer located in the first bending section away from the negative electrode current collector, and the number of negative electrode sheets covered by the first solid electrolyte layer is 1.

[0146] (6) Electrode assembly assembly: Place the punched aluminum-plastic film in the assembly fixture with the punched surface facing up, place the electrode assembly in the punch, and apply external force to press it. Then cover the electrode assembly with another punched aluminum-plastic film with the punched surface facing down, and heat seal the two aluminum-plastic films around their perimeter by hot pressing to obtain the assembled electrode assembly.

[0147] (7) Electrolyte injection and encapsulation: Electrolyte is injected into the assembled electrode assembly, and the battery cell is obtained through vacuum encapsulation, standing, hot pressing, shaping and other processes.

[0148] Comparative Example 1: The electrode at the corner of the battery cell does not have a solid electrolyte layer. It should be noted that, except for the absence of a solid electrolyte layer, all other parameters of Comparative Example 1 are the same as those of Example 1.

[0149] Examples 2 to 20: Except for the parameters mentioned in Table 1, all other parameters are the same as in Example 1, wherein the coating method of the fourth solid electrolyte layer in the second electrode is similar to the coating method of the first solid electrolyte layer in the first electrode.

[0150] Examples 21 to 32: Except for the parameters mentioned in Table 2, all other parameters are the same as in Example 20.

[0151] Examples 33 to 50: Except for the parameters mentioned in Table 3, all other parameters are the same as in Example 20.

[0152] Examples 51 to 70: Except for the parameters mentioned in Table 4, all other parameters are the same as in Example 20.

[0153]

[0154] As can be seen from Comparative Example 1 and Examples 1 to 10, in at least a portion of the first electrode located in the first bending section and / or the second bending section, a first solid electrolyte layer is provided in at least a portion of the surface of the first active material layer away from the first current collector, which can improve the cycle performance of the battery cell, and the improvement effect is better as the number of layers of the first solid electrolyte layer increases.

[0155] As can be seen from Comparative Example 1 and Examples 11-15, in at least a portion of the second electrode located in the first bending section and / or the second bending section, a fourth solid electrolyte layer is provided in at least a portion of the surface of the second active material layer away from the second current collector, which can further improve the cycle performance of the cell, and the improvement effect is better as the number of fourth solid electrolyte layers increases. As can be seen from Examples 1-5 and Examples 11-15, the improvement effect of directly placing the first solid electrolyte layer on the negative electrode is better than the improvement effect of placing the first solid electrolyte layer on the positive electrode.

[0156] As can be seen from Examples 16 to 20, the improvement effect of simultaneously setting a solid electrolyte layer on both the positive and negative electrode plates is better, and the improvement effect is better as the number of solid electrolyte layers increases.

[0157]

[0158] As can be seen from Examples 20 to 23, limiting the cell's cycle performance to 60% ≤ A1 ≤ 100% can improve the cell's cycle performance. It should be noted that when A1 > 100%, the first solid electrolyte layer is prone to protruding beyond the first active material layer, resulting in wasted space and a decrease in the cell's energy density. Therefore, no examples with A1 > 100% were provided.

[0159] As can be seen from Examples 20 and 24-26, limiting B1 to 100% can improve the cycle performance of the battery cell. It should be noted that when B1 > 100%, the first solid electrolyte layer is prone to protruding beyond the first active material layer, resulting in wasted space and a decrease in the energy density of the battery cell. Therefore, no examples with B1 > 100% were provided.

[0160] As shown in Examples 20 and 27-32, limiting the cell's cycle performance to 0.5 mg / cm² ≤ W1 ≤ 5 mg / cm² can improve the cell's cycle performance. When W1 is less than 0.5 mg / cm², the improvement in cycle performance and expansion rate of the cell by setting the first solid electrolyte layer is not significant. When W1 is greater than 5 mg / cm², the larger coating weight and thickness of the first solid electrolyte layer lead to a greater loss in the cell's volumetric energy density. Simultaneously, the increased thickness of the first solid electrolyte layer increases the lithium-ion transport distance, resulting in a higher lithium plating rate at the corner of the negative electrode. Therefore, to balance improving the cell's cycle performance, reducing the loss in volumetric energy density, and lowering the lithium plating rate at the corner of the negative electrode, W1 is set to 0.5 mg / cm² ≤ W1 ≤ 5 mg / cm². Further preferred values ​​are 1 mg / cm² ≤ W1 ≤ 3 mg / cm².

[0161]

[0162] As can be seen from Examples 20 and 33-38, when L1 is less than 0.5 mm, the impact on cycle capacity retention is small, and due to the small winding radius of the inner winding, the first solid electrolyte layer located on the inner winding is more prone to detachment. When L1 is too small, the probability of internal short circuit in the electrode assembly increases due to the shedding of powder from the first solid electrolyte layer, resulting in a lower pass rate for the high-voltage insulation test. When L1 is greater than 2 mm, the cycle capacity retention and high-voltage insulation test pass rate are higher; however, the thickness of the overlapping area between the second solid electrolyte layer and the first active material layer increases, and when L1 is large, the volumetric energy density of the cell decreases. Therefore, to balance high cycle capacity retention, high-voltage insulation test pass rate, and high volumetric energy density, 0.5 mm ≤ L1 ≤ 2 mm is limited, and more preferably 1 mm ≤ L1 ≤ 1.5 mm. As shown in Examples 20 and 39-44, when L2 is less than 0.5 mm, the impact on cycle capacity retention is small, and due to the small winding radius of the inner winding, the first solid electrolyte layer located on the inner winding is more prone to detachment. When L2 is too small, the probability of internal short circuit in the electrode assembly increases due to the shedding of powder from the first solid electrolyte layer, resulting in a lower pass rate for the high-voltage insulation test. When L2 is greater than 2 mm, the cycle capacity retention and high-voltage insulation test pass rate are higher; however, the thickness of the overlapping area between the third solid electrolyte layer and the first active material layer increases, and when L2 is large, the volumetric energy density of the cell decreases. Therefore, to balance high cycle capacity retention, high-voltage insulation test pass rate, and high volumetric energy density, 0.5 mm ≤ L2 ≤ 2 mm is specified, and more preferably 1 mm ≤ L2 ≤ 1.5 mm. As can be seen from Examples 45 to 50, when L1 and L2 are both in the range of 0.5mm to 2mm, a higher cycle capacity retention rate, a higher high voltage insulation test pass rate, and a higher volumetric energy density can be obtained. Furthermore, it is preferable that L1 and L2 are in the range of 1mm to 1.5mm.

[0163]

[0164]

[0165] As shown in Examples 20 and 51-55, in the same layer of positive electrode sheet located in the first bending section, when C1 > C2, the improvement in cycle capacity retention is more significant compared to the cases of C1 = C2 and C1 < C2. In the same layer of positive electrode sheet located in the second bending section, when C1′ > C2′, the improvement in cycle capacity retention is more significant compared to the cases of C1′ = C2′ and C1′ < C2′. This is because at the corner of the cell, the positive electrode sheet covers the negative electrode sheet. On the side of the positive electrode sheet facing the winding center, the winding radius of the positive electrode sheet is larger than that of the negative electrode sheet. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the negative electrode sheet and the positive electrode sheet is insufficient, resulting in a higher risk of interface problems such as lithium plating. By limiting C1 > C2 and / or C1′ > C2′, the fourth solid electrolyte layer provides sufficient ion channels for the negative electrode to receive lithium ions on the side facing the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0166] As shown in Examples 20 and 56-60, in the same layer of positive electrode sheet located in the first bending section, when W3 > W4, the improvement in cycle capacity retention is more significant compared to the cases where W3 = W4 and W3 < W4; in the same layer of positive electrode sheet located in the second bending section, when W3′ > W4′, the improvement in cycle capacity retention is more significant compared to the cases where W3′ = W4′ and W3′ < W4′. This is because at the corner of the cell, the positive electrode sheet covers the negative electrode sheet. On the side of the positive electrode sheet facing the winding center, the winding radius of the positive electrode sheet is larger than that of the negative electrode sheet. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the negative electrode sheet and the positive electrode sheet is insufficient, resulting in a higher risk of interface problems such as lithium plating. By defining W3 > W4 and / or W3′ > W4′, the fourth solid electrolyte layer provides sufficient ion channels for the negative electrode to receive lithium ions on the side facing the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0167] As shown in Examples 20 and 61-65, in the same layer of negative electrode sheet located in the first bending section, when C4 > C3, the improvement in cycle capacity retention is more significant compared to the cases where C3 = C4 and C4 < C3; in the same layer of negative electrode sheet located in the second bending section, when C4′ > C3′, the improvement in cycle capacity retention is more significant compared to the cases where C3′ = C4′ and C4′ < C3′. This is because at the corner of the cell, the negative electrode sheet covers the positive electrode sheet. On the side of the negative electrode sheet facing the winding center, the winding radius of the positive electrode sheet is larger than that of the negative electrode sheet. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the negative electrode sheet and the positive electrode sheet is insufficient, resulting in a higher risk of interface problems such as lithium plating. By limiting C4 > C3 and / or C4′ > C3′, the fourth solid electrolyte layer provides sufficient ion channels for the negative electrode to receive lithium ions on the side facing the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0168] As shown in Examples 20 and 66-70, in the same layer of negative electrode sheet located in the first bending section, when W6 > W5, the improvement in cycle capacity retention is more significant compared to the cases where W5 = W6 and W6 < W5. In the same layer of negative electrode sheet located in the second bending section, when W6′ > W5′, the improvement in cycle capacity retention is more significant compared to the cases where W5′ = W6′ and W6′ < W5′. This is because at the corner of the cell, the negative electrode sheet covers the positive electrode sheet. On the side of the positive electrode sheet facing the winding center, the winding radius of the positive electrode sheet is larger than that of the negative electrode sheet. Consequently, the CB value (the ratio of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode) of the negative electrode sheet and the positive electrode sheet is insufficient, resulting in a higher risk of interface problems such as lithium plating. By limiting W6 > W5 and / or W6′ > W5′, the fourth solid electrolyte layer provides sufficient ion channels for the negative electrode to receive lithium ions on the side facing the winding center of the electrode assembly, reducing the risk of interface problems such as lithium plating and improving the cycle performance of the cell.

[0169] In addition, those skilled in the art may make other changes within the spirit of this application. Of course, all such changes made in accordance with the spirit of this application should be included within the scope disclosed in this application.

Claims

1. A battery cell, characterized in that, The battery cell includes an electrode assembly, the thickness direction of which is a first direction. The electrode assembly includes a first electrode, a separator, and a second electrode that are stacked and wound together. The electrode assembly includes a first straight section, a first bent section, a second straight section, and a second bent section connected in sequence. When viewed along a third direction, the first straight section and the second straight section are arranged opposite each other along the first direction, and the first bent section and the second bent section are arranged opposite each other along a second direction. The first direction, the second direction, and the third direction are perpendicular to each other. The first electrode includes a first current collector, a first active material layer, and a first solid electrolyte layer. Along the thickness direction of the first current collector, the first active material layer is disposed on at least one side surface of the first current collector. In at least a portion of the first electrode located in the first bend and / or the second bend, the first solid electrolyte layer is disposed in at least a portion of the surface of the first active material layer away from the first current collector. The first electrode includes a second solid electrolyte layer and a third solid electrolyte layer. In the first electrode located in the first straight section, the second solid electrolyte layer is provided in a portion of the surface of the first active material layer away from the first current collector. In the first electrode located in the second straight section, the third solid electrolyte layer is provided in a portion of the surface of the first active material layer away from the first current collector. The first bending section includes an N1 layer of the first electrode sheet. The first electrode sheet located on the inner side of the first bending section is provided with a first solid electrolyte layer in 1 / 3 of the N1 layer. Along the winding direction of the first electrode sheet, the two ends of the first solid electrolyte layer are respectively connected to the second solid electrolyte layer and the third solid electrolyte layer. The second bending section includes the first electrode sheet with an N2 layer. The first electrode sheet with an N2 layer located on the inner side of the second bending section is provided with the first solid electrolyte layer. Along the winding direction of the first electrode sheet, the two ends of the first solid electrolyte layer are respectively connected to the second solid electrolyte layer and the third solid electrolyte layer. When 1 / 3N1 is not an integer, the integer less than and closest to 1 / 3N1 is used as the reference; when 1 / 3N2 is not an integer, the integer less than and closest to 1 / 3N2 is used as the reference.

2. The battery cell as described in claim 1, characterized in that, Along the third direction, the ratio of the length of the first solid electrolyte layer to the length of the first active material layer containing the first solid electrolyte layer is A1, where 60% ≤ A1 ≤ 100%; and / or, In at least a portion of the first electrode located in the first bend or the second bend, along the winding direction of the first electrode, the ratio of the width of the first solid electrolyte layer to the width of the first active material layer in which the first solid electrolyte layer is located is B1, 50%≤B1≤100%.

3. The battery cell as described in claim 1, characterized in that, The coating weight per unit area of ​​the first solid electrolyte layer is W1, where 0.5 mg / cm² ≤ W1 ≤ 5 mg / cm².

4. The battery cell as described in claim 3, characterized in that, 1 mg / cm² ≤ W1 ≤ 3 mg / cm².

5. The battery cell as described in claim 1, characterized in that, The first solid electrolyte layer includes a first solid electrolyte, the material of which includes at least one of organic solid electrolyte and inorganic solid electrolyte; wherein, the organic solid electrolyte includes a block copolymer, the block copolymer includes a conductive polymer and a lithium-conducting polymer, the conductive polymer includes at least one of pyrrole, aniline, thiophene, polyacetylene, p-phenylenediamine terephthalamide or 3,4-ethylenedioxythiophene, and the lithium-conducting polymer includes at least one of polyethylene oxide, polyethylene glycol, polypropylene oxide, poly(ethylene glycol) acrylate or poly(ethylene glycol) methacrylate; the inorganic solid electrolyte includes at least one of oxide solid electrolyte and sulfide solid electrolyte, the oxide solid electrolyte includes at least one of lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide or lithium lanthanum titanate, and the sulfide solid electrolyte includes at least one of lithium sulfur silver germanium or lithium sulfur phosphorus.

6. The battery cell as described in claim 5, characterized in that, The first solid electrolyte layer further includes a first binder and a first conductive agent. The material of the first binder includes at least one of polyvinylidene fluoride, polyacrylic acid, and carboxymethyl cellulose. The material of the first conductive agent includes at least one of carbon nanotubes, carbon black, conductive graphite, and graphene.

7. The battery cell as described in claim 6, characterized in that, The mass ratio of the first adhesive to the mass of the first solid electrolyte layer is W2, where 1% ≤ W2 ≤ 10%.

8. The battery cell as described in claim 1, characterized in that, Along the second direction, the length of the second solid electrolyte layer is L1, 0.5mm ≤ L1 ≤ 2mm; and / or, Along the second direction, the length of the third solid electrolyte layer is L2, 0.5mm≤L2≤2mm.

9. The battery cell as described in claim 8, characterized in that, 1mm≤L1≤1.5mm; and / or, 1mm≤L2≤1.5mm.

10. The battery cell according to any one of claims 1 to 9, characterized in that, The first electrode is the negative electrode, and the second electrode is the positive electrode.

11. The battery cell as described in claim 10, characterized in that, The second electrode includes a second current collector, a second active material layer, and a fourth solid electrolyte layer. Along the thickness direction of the second current collector, the second active material layer is disposed on at least one side surface of the second current collector. In at least a portion of the second electrode located in the first bending section and / or the second bending section, the fourth solid electrolyte layer is disposed in at least a portion of the surface of the second active material layer away from the second current collector.

12. The battery cell as described in claim 11, characterized in that, In the same layer of the second electrode located in the first bending section, on the side facing the winding center of the electrode assembly, the ratio of the area of ​​the fourth solid electrolyte layer to the area of ​​the second active material layer containing the fourth solid electrolyte layer is C1; on the side away from the winding center of the electrode assembly, the ratio of the area of ​​the fourth solid electrolyte layer to the area of ​​the second active material layer containing the fourth solid electrolyte layer is C2; C1 > C2; and / or, In the second electrode sheet of the same layer located in the second bending section, on the side facing the winding center of the electrode assembly, the ratio of the area of ​​the fourth solid electrolyte layer to the area of ​​the second active material layer in which the fourth solid electrolyte layer is located is C1′; on the side away from the winding center of the electrode assembly, the ratio of the area of ​​the fourth solid electrolyte layer to the area of ​​the second active material layer in which the fourth solid electrolyte layer is located is C2′; C1′>C2′.

13. The battery cell as described in claim 11, characterized in that, In the second electrode sheet within the same layer located in the first bending section, on the side facing the winding center of the electrode assembly, the coating weight per unit area of ​​the fourth solid electrolyte layer is W3; on the side away from the winding center of the electrode assembly, the coating weight per unit area of ​​the fourth solid electrolyte layer is W4; W3 > W4; and / or, In the second electrode sheet of the same layer located in the second bending section, the coating weight per unit area of ​​the fourth solid electrolyte layer is W3′ on the side facing the winding center of the electrode assembly; and W4′ on the side away from the winding center of the electrode assembly; W3′>W4′.

14. The battery cell as described in claim 10, characterized in that, In the same layer of the first electrode sheet located in the first bend section, on the side facing the winding center of the electrode assembly, the ratio of the area of ​​the first solid electrolyte layer to the area of ​​the first active material layer containing the first solid electrolyte layer is C3; on the side away from the winding center of the electrode assembly, the ratio of the area of ​​the first solid electrolyte layer to the area of ​​the first active material layer containing the first solid electrolyte layer is C4; C4 > C3; and / or, In the first electrode sheet of the same layer located in the second bending section, on the side facing the winding center of the electrode assembly, the ratio of the area of ​​the first solid electrolyte layer to the area of ​​the first active material layer in which the first solid electrolyte layer is located is C3′; on the side away from the winding center of the electrode assembly, the ratio of the area of ​​the first solid electrolyte layer to the area of ​​the first active material layer in which the first solid electrolyte layer is located is C4′; C4′>C3′.

15. The battery cell as described in claim 10, characterized in that, In the first electrode sheet within the same layer located in the first bend section, on the side facing the winding center of the electrode assembly, the coating weight per unit area of ​​the first solid electrolyte layer is W5; on the side away from the winding center of the electrode assembly, the coating weight per unit area of ​​the first solid electrolyte layer is W6; W6 > W5; and / or, In the first electrode sheet of the same layer located in the second bending section, on the side facing the winding center of the electrode assembly, the coating weight per unit area of ​​the first solid electrolyte layer is W5′; on the side away from the winding center of the electrode assembly, the coating weight per unit area of ​​the first solid electrolyte layer is W6′; W6′>W5′.

16. A secondary battery, characterized in that, The secondary battery includes the cell as described in any one of claims 1 to 15.

17. An electronic device, characterized in that, The electronic device includes the secondary battery as described in claim 16.

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