Battery cell

Abstract

The invention discloses a battery cell. The battery cell comprises an anode plate, a cathode plate and a diaphragm. The anode strip comprises a plurality of first straight sections and a plurality of anode corner sections which are sequentially connected along the winding direction of the battery cell, the anode strip comprises a first current collector and a first active substance layer, the first active substance layer comprises a long film surface and a short film surface, and the long film surface and the short film surface are respectively arranged on two sides of the current collector; the surface density of the long film surface at the anode corner section is a first surface density, the surface density of the long film surface at the first straight section is a second surface density, and the first surface density is greater than the second surface density. The active material layer on the long film surface of the anode plate is non-uniformly coated, so that the first surface density of the active material layer at the corner of the anode plate is increased and is greater than the second surface density at the straight position, the total amount of the active material in the corner area is increased, and the lithium intercalation capability of the anode plate at the corner is improved; the lithium precipitation phenomenon in the corner area of the battery cell is improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a battery cell. Background Technology

[0002] In the field of lithium batteries, lithium plating in battery cells has become a key issue restricting battery life and safety. Due to structural characteristics, the corner areas of battery cells have insufficient space for lithium intercalation on the anode plates, making them more prone to lithium plating. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a battery cell that can effectively improve the lithium plating phenomenon at the corners of the battery cell.

[0004] A battery cell according to an embodiment of the present invention includes an anode sheet, a cathode sheet, and a separator. The anode sheet includes a plurality of first straight sections and a plurality of anode corner sections sequentially connected along the winding direction of the battery cell. The anode sheet includes a first current collector and a first active material layer. The first active material layer includes a long film surface and a short film surface, which are respectively disposed on both sides of the current collector along its thickness direction. The areal density of the long film surface located in the anode corner section is a first areal density, and the areal density of the long film surface located in the first straight section is a second areal density, wherein the first areal density is greater than the second areal density. The cathode sheet includes a plurality of second straight sections and a plurality of cathode corner sections sequentially connected along the winding direction of the battery cell. The cathode sheet includes a second current collector and a second active material layer. The anode sheet and the cathode sheet are stacked and wound together. The separator is disposed between the anode sheet and the cathode sheet.

[0005] The battery cell according to embodiments of the present invention has at least the following beneficial effects: Research has shown that lithium plating mainly occurs on the long film surface of the active material layer at the corner of the anode sheet because the cathode sheet arc length is relatively long at this location, resulting in insufficient lithium intercalation capability of the anode sheet. Therefore, by unevenly coating the active material layer on the long film surface of the anode sheet, the first areal density of the active material layer at the corner of the anode sheet is increased, making it greater than the second areal density in the straight section, thereby increasing the total amount of active material in the corner region and improving the lithium intercalation capability of the anode sheet at the corner, thus mitigating the lithium plating phenomenon in the corner region of the battery cell.

[0006] According to some embodiments of the present invention, the anode corner segment includes a first corner segment and a plurality of second corner segments, the first corner segment being the innermost anode corner segment of the cell; the cathode corner segment includes a third corner segment and a plurality of fourth corner segments, the third corner segment being the innermost cathode corner segment of the cell; the radius of the first corner segment is D0; the radius of the third corner segment is D1; ​​the distance between two adjacent anode corner segments is R0; the distance between two adjacent cathode corner segments is R1; and the second active... The specific capacity of the material layer is a, the areal density of the second active material layer is b, the proportion of the second active material layer is c, the specific capacity of the first active material layer is d, the proportion of the first active material layer is e, the ratio of the anode capacity to the cathode capacity at the anode corner segment and the cathode corner segment is CB, from the inside to the outside, n: the nth anode corner segment of the anode sheet, the first areal density = ((D1 + R1 × (n - 1)) / (D0 + R0 × (n - 1))) × (CB × b × a × c / (e × d)).

[0007] According to some embodiments of the present invention, the thickness of the diaphragm is L1, the thickness of the first current collector is L2, and D0 = 3 × L1 + L2.

[0008] According to some embodiments of the present invention, the thickness of the first active material layer located at the anode corner segment is L3, and D1 = D0 + 0.5L3 + L1 + R1.

[0009] According to some embodiments of the present invention, 2μm≤L1≤20μm, and / or, 2μm≤L2≤15μm.

[0010] According to some embodiments of the present invention, the thickness of the anode sheet having a double layer of the first active material is L4, the thickness of the cathode sheet having a double layer of the second active material is L5, R0 = L5 + 2 × L1, and R1 = L4 + 2 × L1.

[0011] According to some embodiments of the present invention, 8μm≤L4≤500μm, 8μm≤L5≤500μm.

[0012] According to some embodiments of the present invention, 130mAh / g ≤ a ≤ 274mAh / g, and / or, 10mg / 1540.25mm 2 ≤b≤500mg / 1540.25mm 2 .

[0013] According to some embodiments of the present invention, 1.0 ≤ CB ≤ 2.0, and / or, 50% ≤ c ≤ 100%.

[0014] According to some embodiments of the present invention, 50mAh / g≤d≤3860mAh / g, and / or, 50%≤e≤100%.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the battery cell structure in one embodiment of the present invention; Figure 2 This is a top view of the anode sheet in one embodiment of the present invention; Figure 3 This is a side view of the anode sheet in one embodiment of the present invention; Figure 4 This is a schematic diagram of the first part of the experimental data in several embodiments of the present invention; Figure 5 This is a schematic diagram of the second part of the experimental data in several embodiments of the present invention; Figure 6 This is a schematic diagram of the second part of the experimental data in several embodiments of the present invention.

[0017] Reference numerals: Cell 100, Anode plate 101, First straight section 102, Anode corner section 103, First current collector 104, First active material layer 105, Cathode plate 106, Second straight section 107, Cathode corner section 108, Second current collector 109, Second active material layer 110, Separator 111, First corner section 112, Second corner section 113, Third corner section 114, Fourth corner section 115, Long film surface 301, Short film surface 302. Detailed Implementation

[0018] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0019] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0020] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0021] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0022] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0023] In the existing technology, the long and short film surfaces of the cathode and anode are uniformly coated, which results in insufficient lithium intercalation capability of the anode sheet of the wound cell due to structural problems, thus causing the corner lithium plating phenomenon.

[0024] This invention proposes a battery cell that can improve the lithium plating phenomenon at corners.

[0025] refer to Figures 1 to 3According to an embodiment of the present invention, the battery cell 100 includes an anode sheet 101, a cathode sheet 106, and a separator 111. The anode sheet 101 includes a plurality of first straight sections 102 and a plurality of anode corner sections 103 connected sequentially along the winding direction of the battery cell 100. The anode sheet 101 includes a first current collector 104 and a first active material layer 105. The first active material layer 105 includes a long film surface 301 and a short film surface 302. The long film surface 301 and the short film surface 302 are respectively disposed on both sides of the current collector along its thickness direction. The areal density of the long film surface 301 located in the anode corner section 103 is a first areal density, and the areal density of the long film surface 301 located in the first straight section 102 is a second areal density. The first areal density is greater than the second areal density. The cathode plate 106 includes multiple second straight sections 107 and multiple cathode corner sections 108 connected sequentially along the winding direction of the cell 100. The cathode plate 106 includes a second current collector 109 and a second active material layer 110. The anode plate 101 and the cathode plate 106 are stacked and wound together. A separator 111 is disposed between the anode plate 101 and the cathode plate 106. Studies have shown that lithium plating mainly occurs on the long film surface 301 of the active material layer at the corner of the anode plate 101 because the arc length of the cathode plate 106 is relatively long at this location, resulting in insufficient lithium intercalation capacity of the anode plate 101. Therefore, by unevenly coating the active material layer on the long film surface 301 of the anode plate 101, the first areal density of the active material layer at the corner of the anode plate 101 is increased, making it greater than the second areal density at the straight sections. This increases the total amount of active material in the corner region and enhances the lithium intercalation capacity of the anode plate 101 at the corner, thereby improving the lithium plating phenomenon in the corner region of the cell 100.

[0026] refer to Figures 1 to 3In some embodiments of the present invention, the anode corner segment 103 includes a first corner segment 112 and a plurality of second corner segments 113, the first corner segment 112 being the innermost anode corner segment 103 of the cell 100; the cathode corner segment 108 includes a third corner segment 114 and a plurality of fourth corner segments 115, the third corner segment 114 being the innermost cathode corner segment 108 of the cell 100; the radius of the first corner segment 112 is D0; the radius of the third corner segment 114 is D1; ​​the distance between two adjacent anode corner segments 103 is R0; and the distance between two adjacent cathode corner segments 108 is... R1, the specific capacity of the second active material layer 110 is a, the areal density of the second active material layer 110 is b, the proportion of the second active material layer 110 is c, the specific capacity of the first active material layer 105 is d, the proportion of the first active material layer 105 is e, the ratio of the anode capacity to the cathode capacity at the anode corner segment 103 and the cathode corner segment 108 is CB, from the inside to the outside, n: the nth anode corner segment 103 of the anode plate 101, the first areal density = ((D1 + R1 × (n - 1)) / (D0 + R0 × (n - 1))) × (CB × b × a × c / (e × d)). Since the increase in the first areal density, i.e. the areal density of the active material layer at the corner of the anode plate 101, can improve the lithium plating phenomenon, by setting a target CB value (Cell Balance, i.e. the capacity balance value of cell 100), and then adjusting the various parameters of the second active material layer 110 and the specific capacity of the first active material layer 105, the optimal first areal density can be calculated by the above formula, thereby achieving the best effect of improving the corner lithium plating.

[0027] refer to Figures 4 to 6 This application demonstrates, through setting up eight comparative examples and embodiments, that by unevenly coating the active material layer on the long film surface 301 of the anode sheet 101, the first surface density of the active material layer at the corner of the anode sheet 101 is increased. Specifically, the number of cycles of lithium deposition obtained after the same set of experimental data shows that the number of cycles of lithium deposition in the embodiments increases, thus the corner lithium deposition phenomenon is effectively improved.

[0028] It should be noted that the innermost anode corner segment 103 of cell 100 refers to... Figure 1 The corner segment shown has at least one side coated with the first active material layer 105. In some cell 100 structures, the anode sheet 101 has a pre-folded section with empty foil, that is, only the pre-folded section of the first current collector 104. In this case, the section is not regarded as the innermost anode corner segment 103, but its thickness is included in the radius D0 of the first corner segment 112. The third corner segment 114 of the cathode sheet 106 is judged in the same way as the first corner segment 112. If an empty foil pre-folded section appears, it is not regarded as the innermost cathode corner segment 108, but its thickness is included in the radius D1 of the third corner segment 114.

[0029] It should be noted that the reference Figure 1 The radii of D0 and D1 are essentially the sum of the thicknesses of the components at the corner. The calculation logic for the first surface density is (cathode radius / anode radius) × (CB × cathode surface density × cathode active material ratio × cathode specific capacity / (anode active material ratio × anode specific capacity)). The above formula is obtained by simplifying similar terms.

[0030] refer to Figures 1 to 3 In some embodiments of the present invention, the thickness of the diaphragm 111 is L1, the thickness of the first current collector 104 is L2, and D0 = 3 × L1 + L2. Figure 1 The battery cell 100 structure has partially pre-wound the separator 111. The innermost first corner segment 112 is the first current collector 104 with a first active material layer 105 coated on one side. Therefore, D0 is the thickness of the first current collector 104 itself, plus the thickness of the single-layer separator 111 included on its right side and the thickness of the two pre-wound separators 111, that is, the thickness of the three separators 111 in total. Similarly, the radius of the first corner segment 112 on the right side of the battery cell 100 needs to be calculated, and the thickness of the two pre-wound separators 111 inside also needs to be included. So it is also the thickness of the first current collector 104 plus the thickness of the three separators 111, that is, 3×L1+L2. In some embodiments, the different innermost structures of the cell 100 will also affect the calculation of the parameters of D0. Specifically, it can be calculated based on the sum of the thicknesses of all components that the cell 100 passes through from the first corner segment 112 to the center of the cell 100. If there is a pre-folding of the empty foil of the cathode sheet 106, the thickness of the second current collector 109 of the cathode sheet 106 also needs to be added. In addition, the calculation of D0 also needs to include the thickness of the first current collector 104 itself.

[0031] refer to Figure 1 In some embodiments of the present invention, the thickness of the first active material layer 105 located at the anode corner segment 103 is L3, and D1 = D0 + 0.5L3 + L1 + R1. Since the first corner segment 112 is to the right of the third corner segment 114, the thickness of the third corner segment 114 includes the thickness of the first corner segment 112. Furthermore, since the first active material layer 105 is coated on the left side of the first corner segment 112, the thickness of the third corner segment 114 also includes the coating thickness on one side, i.e., 0.5L3. Figure 1 It is known that it also includes the diaphragm 111 and a thickness of R1, therefore in Figure 1In the structure of the cell 100 shown, D1 = D0 + 0.5L3 + L1 + R1. In some embodiments, the different innermost structures of the cell 100 will also affect the calculation of the parameter D1. Specifically, it can be calculated based on the thickness of D0 in the structure of the cell 100 and the sum of the distances between the third corner segment 114 and the first corner segment 112. If other components appear between the third corner segment 114 and the first corner segment 112, their thicknesses also need to be added accordingly. In addition, the calculation of D1 does not need to include the thickness of the cathode sheet 106 itself.

[0032] refer to Figure 3 In some embodiments of the present invention, the thickness of L3 is the total thickness L4 of the corner section anode plate 101 minus the thickness L2 of the first current collector 104.

[0033] In some embodiments of the present invention, 2μm ≤ L1 ≤ 20μm, and / or, 2μm ≤ L2 ≤ 15μm. Specifically, L1 can be a thickness of 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, or any value from 2μm to 20μm, while L2 can be a thickness of 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or any value from 2μm to 15μm, depending on the appropriate thickness. The thickness of the separator 111 can balance mechanical strength and electrolyte wetting ability. When L1 is less than 2μm, the thickness of the separator 111 is too small, resulting in insufficient mechanical strength. It is easily punctured by electrode burrs, which can lead to accidents such as short circuits. Furthermore, the electrolyte storage capacity is reduced, exacerbating lithium plating. When L1 is greater than 20μm, the thickness of the separator 111 is too thick. On the one hand, it will reduce the energy density of the cell 100, and on the other hand, it will reduce the porosity, affecting the performance of the cell 100. A separator 111 with a large thickness also has problems such as high manufacturing difficulty and poor thickness uniformity. Choosing an appropriate thickness for the first current collector 104 can alleviate stress deformation at the corner of the cell 100 and balance the dual requirements of energy density and mechanical strength. When L2 is less than 2μm, the thickness of the first current collector 104 is too small, which will also lead to insufficient mechanical strength and make it easy for lithium plating to puncture, thus causing a safety accident. When L2 is greater than 15μm, the thickness of the first current collector 104 is too large, which will reduce the energy density of the cell 100 and increase internal resistance and heat loss.

[0034] refer to Figure 1 and Figure 3In some embodiments of the present invention, the thickness of the anode plate 101 having a double first active material layer 105 is L4, and the thickness of the cathode plate 106 having a double second active material layer 110 is L5, R0 = L5 + 2 × L1, R1 = L4 + 2 × L1. The distance between two adjacent anode corner segments 103 is R0, that is, R0 is equal to the total thickness of the cathode plate 106 at the corner plus the thickness of the separators 111 on both sides. The distance between two adjacent cathode corner segments 108 is R1, that is, R1 is equal to the total thickness of the anode plate 101 at the corner plus the thickness of the separators 111 on both sides. If there are other components such as adhesive tape in some cell 100 structures, the thickness of the adhesive tape or other components is added.

[0035] In some embodiments of the present invention, 8μm≤L4≤500μm and 8μm≤L5≤500μm. Specifically, L4 can be 8μm, 10μm, 15μm, 30μm, 35μm, 55μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 420μm, 430μm, 440μm, 450μm, 460μm, 470μm, 480μm, 490μm, 500μm, or any value from 8μm to 500μm. Choosing an appropriate thickness for the anode sheet 101 can alleviate stress concentration and improve lithium plating. When L4 is greater than 500μm, the thickness of the anode sheet 101 is too large, which will aggravate extrusion, increase the risk of lithium plating, and affect the overall energy density. When L4 is less than 8μm, the thickness of the anode sheet 101 is too small. Being too thin also has the disadvantages of poor mechanical strength and being easily punctured. L5 can be 8μm, 10μm, 15μm, 30μm, 35μm, 55μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 420μm, 430μm, 440μm, 450μm, 460μm, 470μm, 480μm, 490μm, 500μm, or any value from 8μm to 500μm. Choosing a suitable cathode sheet 106 is also to improve stress concentration and lithium plating. Too thick or too thin will affect the overall energy density and mechanical strength.

[0036] In some embodiments of the present invention, 130mAh / g ≤ a ≤ 274mAh / g, and / or, 10mg / 1540.25mm 2 ≤b≤500mg / 1540.25mm 2The specific capacity of the second active material layer 110, i.e., the specific capacity of the cathode active material layer, represents the amount of electricity that can theoretically be released per gram of cathode active material. For example, when a = 130 mAh / g, it means that each gram of cathode active material can theoretically release 130 milliamperes of electricity. Specifically, a can be 130 mAh / g, 140 mAh / g, 160 mAh / g, 180 mAh / g, 190 mAh / g, 200 mAh / g, 210 mAh / g, 215 mAh / g, 220 mAh / g, 225 mAh / g, 230 mAh / g, 235 mAh / g, 240 mAh / g, 245 mAh / g, 250 mAh / g, 255 mAh / g, 260 mAh / g, 265 mAh / g, 270 mAh / g, 271 mAh / g, etc. Choosing the appropriate specific capacity of the second active material layer 110—whether it's mAh / g, 272mAh / g, 273mAh / g, 274mAh / g, or any value between 130mAh / g and 274mAh / g—can effectively improve the battery's energy density and optimize its cycle life. When 'a' is less than 130mAh / g, the specific capacity of the second active material layer 110 is too low, resulting in poor lithium-ion storage capacity. This necessitates increasing the amount of the second active material layer 110, leading to a larger overall volume and weight of the cell 100. Conversely, when 'a' is greater than 274mAh / g, the specific capacity of the second active material layer 110 is too high, resulting in poor material stability, more vigorous reactions during charging and discharging, potentially causing safety issues and exacerbating side reactions between the cathode and electrolyte, thus affecting the stability of the cell 100. The areal density 'b' of the second active material layer 110 represents the mass of the second active material within a certain area. For example, when b = 10mg / 1540.25mm²... 2 At that time, it represented 1540.25mm. 2 Under the given area, the mass of the second active substance is 10 mg. Specifically, b can be 10 mg / 1540.25 mm². 2 20mg / 1540.25mm 2 30mg / 1540.25mm 2 40mg / 1540.25mm 2 50mg / 1540.25mm 2 60mg / 1540.25mm 2 70mg / 1540.25mm 2 80mg / 1540.25mm 2 90mg / 1540.25mm 2 100mg / 1540.25mm 2 200mg / 1540.25mm 2300mg / 1540.25mm 2 350mg / 1540.25mm 2 400mg / 1540.25mm 2 410mg / 1540.25mm 2 420mg / 1540.25mm 2 430mg / 1540.25mm 2 450mg / 1540.25mm 2 470mg / 1540.25mm 2 480mg / 1540.25mm 2 490mg / 1540.25mm 2 500mg / 1540.25mm 2 It could also be 10mg / 1540.25mm. 2 Up to 500mg / 1540.25mm 2 Any value in the range. When b is less than 10mg / 1540.25mm 2 When the areal density of the second active material layer 110 is too low, it will lead to insufficient overall capacity and poor performance of the cell 100. This is especially true when b > 500 mg / 1540.25 mm². 2 If the surface density of the second active material layer 110 is too high, it will easily lead to excessive thickness, affecting electrolyte wetting, and also cause the surface density of the first active material layer 105 to increase accordingly, making the overall size of the battery cell 100 too large. In addition, excessive surface density can also easily lead to internal stress concentration, which will reduce the toughness of the coating or cause it to break.

[0037] In some embodiments of the present invention, 1.0 ≤ CB ≤ 2.0, and / or 50% ≤ c ≤ 100%. The CB value is Cell Balance, i.e., the capacity balance value of cell 100, or the ratio of anode capacity to cathode capacity. Setting a suitable CB value can effectively improve lithium plating and enhance the cycle life of cell 100. Specifically, the CB value can be 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or any value between 1.0 and 2.0. When CB is less than 1.0, the CB value is too small, and the amount of lithium ions released from the positive electrode exceeds the amount that can be inserted into the negative electrode, thus triggering lithium plating. When CB is greater than 2.0, the CB value is too large, leading to an imbalance in the positive and negative electrode ratio, low utilization, and reduced energy density. In the embodiments of the present invention, the most suitable first areal density value is obtained by setting a CB value and then adjusting various values. c represents the proportion of the second active material layer 110, referring to the content of the second active material layer 110 on the coating of the cathode plate 106. Because in some cells 100, the cathode plate 106 is also coated with materials such as adhesives and conductive agents, c can be a proportion of 50%, 60%, 70%, 80%, 90%, 100%, or any proportion between 50% and 100%. Choosing a suitable proportion of the second active material layer 110 can balance electrochemical performance and overall structural stability. When c is less than 50%, it means that the content of conductive agents, adhesives, etc. is too high, which will increase the overall weight without improving the performance of the cell 100 and will also reduce the energy density of the cell 100. In some parts, the proportion of the second active material layer 110 can reach 100%, that is, there are no conductive agents, adhesives, or other substances in that area.

[0038] In some embodiments of the present invention, 50mAh / g ≤ d ≤ 3860mAh / g, and / or, 50% ≤ e ≤ 100%. d is the gram capacity of the first active material, representing the theoretical energy storage capacity of the first active material layer 105 per unit weight. For example, when d is 50mAh / g, it means that one gram of the first active material can theoretically store 50mAh of energy. Specifically, d can be 50mAh / g, 100mAh / g, 200mAh / g, 300mAh / g, 400mAh / g, 500mAh / g, 600mAh / g, 700mAh / g, 800mAh / g, 900mAh / g, 1000mAh / g, 1100mAh / g, 1200mAh / g, 1300mAh / g, 1500mAh / g, 1700mAh / g, 2000mAh / g, 2100mAh / g, 2200mAh / g, 230mAh / g, etc. Values ​​such as 0mAh / g, 2700mAh / g, 3000mAh / g, 3500mAh / g, 3800mAh / g, 3820mAh / g, 3840mAh / g, and 3860mAh / g, or any value between 50mAh / g and 3860mAh / g, are similar to the specific capacity of the second active material layer 110. When d is less than 50mAh / g or greater than 3860mAh / g, problems such as poor lithium-ion storage capacity, poor material stability, violent reaction process, and impact on safety performance may occur. The value of e represents the proportion of the first active material layer 105, which refers to the content of the first active material layer 105 on the coating of the anode plate 101. This is because in some cells 100, the anode plate 101 is also coated with materials such as adhesives and conductive agents. Specifically, e can be a proportion of 50%, 60%, 70%, 80%, 90%, 100%, or any proportion between 50% and 100%. Choosing an appropriate proportion of the first active material layer 105 can balance electrochemical performance and overall structural stability. When e is less than 50%, it indicates that the content of conductive agents, adhesives, etc. is too high. This will increase the overall weight without improving the performance of the cell 100 and will also reduce the energy density of the cell 100. In some parts, the proportion of the first active material layer 105 can reach 100%, that is, there are no conductive agents, adhesives, or other substances in that area.

[0039] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An electric cell, characterized by, Comprise: an anode sheet comprising a plurality of first flat sections and a plurality of anode corner sections connected in sequence along a winding direction of the battery cell, the anode sheet comprising a first current collector and a first active material layer, the first active material layer comprising a long film surface and a short film surface, the long film surface and the short film surface being respectively arranged on both sides of the current collector along its thickness direction, a surface density of the long film surface located at the anode corner section being a first surface density, a surface density of the long film surface located at the first flat section being a second surface density, the first surface density being greater than the second surface density; a cathode sheet comprising a plurality of second flat sections and a plurality of cathode corner sections connected in sequence along the winding direction of the battery cell, the cathode sheet comprising a second current collector and a second active material layer, the anode sheet and the cathode sheet being stacked with each other and wound; a separator arranged between the anode sheet and the cathode sheet.

2. The electric cell of claim 1, wherein, The anode corner section comprises one first corner section and a plurality of second corner sections, the first corner section being the innermost anode corner section of the battery cell, the cathode corner section comprises one third corner section and a plurality of fourth corner sections, the third corner section being the innermost cathode corner section of the battery cell, a radius of the first corner section being D0, a radius of the third corner section being D1, a distance between two adjacent anode corner sections being R0, a distance between two adjacent cathode corner sections being R1, a gram capacity of the second active material layer being a, a surface density of the second active material layer being b, a proportion of the second active material layer being c, a gram capacity of the first active material layer being d, a proportion of the first active material layer being e, a ratio of anode capacity to cathode capacity at the anode corner section and the cathode corner section being CB, from inside to outside, n: the nth anode corner section of the anode sheet, the first surface density = ((D1+R1×(n-1)) / (D0+R0×(n-1)))×(CB×b×a×c / (e×d)).

3. The electric cell of claim 2, wherein, A thickness of the separator being L1, a thickness of the first current collector being L2, D0=3×L1+L2.

4. The electric cell of claim 3, wherein, A thickness of the first active material layer located at the anode corner section being L3, D1=D0+0.5L3+L1+R1.

5. The electric cell of claim 4, wherein, 2μm≤L1≤20μm, and / or, 2μm≤L2≤15μm.

6. The electric cell of claim 4, wherein, A thickness of the anode sheet with double-layer first active material layer being L4, a thickness of the cathode sheet with double-layer second active material layer being L5, R0=L5+2×L1, R1=L4+2×L1.

7. The electric cell of claim 6, wherein, 8μm≤L4≤500μm, 8μm≤L5≤500μm.

8. The electric cell of claim 2, wherein, 130 mAh / g < a < 274 mAh / g, and / or, 10 mg / 15 40.25 mm 2 ≤ b ≤ 500 mg / 15 40.25 mm 2 .

9. The electric cell of claim 2, wherein, 1.0≤CB≤2.0, and / or, 50%≤c≤100%.

10. The electric cell of claim 2, wherein, 50mAh / g≤d≤3860mAh / g, and / or, 50%≤e≤100%.

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