Battery

Abstract

The utility model provides a battery, relates to the technical field of batteries, and is used for solving the technical problem of low energy density of the battery. The battery comprises a positive plate, a diaphragm and a negative plate which are stacked in sequence; the first end of the positive plate is provided with a first concave area and a positive lug; the first end of the negative plate is provided with a second concave area and a negative lug, a part of the structure of the positive lug is bent and arranged in the second concave area, and a part of the structure of the negative lug is bent and arranged in the first concave area; the size of the first concave area in the first direction is larger than that of the second concave area in the first direction; the size of the first recessed area in the second direction is larger than the size of the second recessed area in the second direction. The energy density of the battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery. Background Art

[0002] The battery is a rechargeable battery that uses lithium ion intercalation compounds as the positive electrode material. It has the advantages of high energy density, fast charging, long cycle life, good safety performance and less impact on the environment.

[0003] In the related art, the battery includes a positive electrode sheet, a separator and a negative electrode sheet stacked in sequence. The first end of the positive electrode sheet has a positive electrode ear, and the first end of the negative electrode sheet has a negative electrode ear. Some idle space is reserved at the first end of the battery to bend the positive electrode ear and the negative electrode ear to form a folded electrode ear.

[0004] However, the related art has a technical problem of low energy density. Utility Model Content

[0005] In view of the above problems, an embodiment of the present application provides a battery for solving the problem of low energy density of the battery.

[0006] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0007] An embodiment of the present application provides a battery, comprising: a positive electrode sheet, a separator, and a negative electrode sheet stacked in sequence; the first end of the positive electrode sheet has a first recessed area and a positive electrode ear; the first end of the negative electrode sheet has a second recessed area and a negative electrode ear, part of the structure of the positive electrode ear is bent and arranged in the second recessed area, and part of the structure of the negative electrode ear is bent and arranged in the first recessed area; the size of the first recessed area in the first direction is larger than the size of the second recessed area in the first direction; the size of the first recessed area in the second direction is larger than the size of the second recessed area in the second direction.

[0008] In some embodiments, along the second direction, one end of the positive electrode tab close to the positive electrode sheet has a first covering layer.

[0009] In some embodiments, the positive electrode sheet includes a first current collector and a first active material layer disposed on the first current collector;

[0010] There is a gap between the first covering layer and the first active material layer; or there is an overlapping area between the first covering layer and the first active material layer.

[0011] In some embodiments, the structure of the first covering layer in the first direction includes a first thinned portion, a flat portion, and a second thinned portion connected in sequence;

[0012] The first cover layer further includes at least one of a first protrusion and a second protrusion;

[0013] When the first covering layer includes the first protrusion and the second protrusion, the first protrusion is provided at an end of the first thinned portion away from the flat portion; and the second protrusion is provided at an end of the second thinned portion away from the flat portion.

[0014] In some embodiments, the first thinned portion has a first protrusion at one end away from the flat portion; and the second thinned portion has a second protrusion at one end away from the flat portion;

[0015] The length of the flat portion is greater than the lengths of the first protruding portion, the first thinned portion, the second thinned portion, and the second protruding portion.

[0016] In some embodiments, the ratio of the sum of the lengths of the first protrusion and the second protrusion to the length of the first covering layer is between 0.15 and 0.2; and / or

[0017] The ratio of the sum of the lengths of the first thinned portion and the second thinned portion to the length of the first covering layer is between 0.16 and 0.33.

[0018] In some embodiments, at least one of the following is included:

[0019] The maximum dimension of the first protrusion in the third direction is greater than the maximum dimension of the first thinned portion in the third direction;

[0020] The maximum dimension of the second protrusion in the third direction is greater than the maximum dimension of the second thinned portion in the third direction;

[0021] The maximum dimension of the flat portion in the third direction is larger than the maximum dimensions of the first and second thinned portions in the third direction.

[0022] In some embodiments, the size of the first protrusion in the first direction is 0 to 2 mm;

[0023] The size of the first thinned portion in the first direction is 0.5 to 1 mm;

[0024] The size of the flat portion in the first direction is 1 to 10 mm;

[0025] The size of the second thinned portion in the first direction is 0.5 to 1 mm;

[0026] A dimension of the second protrusion in the first direction is 0 to 2 mm.

[0027] In some embodiments, the angle between the first protruding portion and the first thinned portion is 45° to 150°; the angle between the first thinned portion and the flat portion is 10° to 30°.

[0028] In some embodiments, the width of the first covering layer in the first direction is less than or equal to the widths of the first recessed area and the second recessed area in the first direction.

[0029] In some embodiments, a ratio of a width of the first covering layer in the first direction to a width of the first recessed area and a width of the second recessed area in the first direction is 0.6-1.

[0030] In some embodiments, a second covering layer is provided on the negative electrode tab at a connection position with the negative electrode sheet.

[0031] In some embodiments, the negative electrode sheet includes a second current collector and a second active material layer disposed on the second current collector, the second current collector includes a second covering area and a second non-covering area, the second covering area is configured to cover the second active material layer, the negative electrode tab is connected to the second non-covering area of ​​the second current collector, and the second covering layer covers the connection position between the negative electrode tab and the second current collector.

[0032] In some embodiments, the first end of the diaphragm has a first set of slits and a second set of slits;

[0033] The first slit group includes two first slits, the two first slits are spaced apart along a first direction, and the projection of the positive electrode tab on the separator is located between the two first slits;

[0034] The second slit group includes two second slits, the two second slits are spaced apart along the first direction, and the projection of the negative electrode tab on the separator is located between the two second slits.

[0035] In the battery provided in the embodiment of the present application, a first recessed area and a positive electrode ear are provided at the first end of the positive electrode sheet, and a second recessed area and a negative electrode ear are provided at the first end of the negative electrode sheet, and the size of the first recessed area in the first direction is larger than the size of the second recessed area in the first direction; the size of the first recessed area in the second direction is larger than the size of the second recessed area in the second direction; part of the structure of the positive electrode ear is bent and provided in the second recess, and part of the structure of the negative electrode ear is bent and provided in the first recess. In this way, the space occupied by the positive electrode ear and the negative electrode ear at the first end of the battery after being bent can be reduced, and the area of ​​the positive electrode ear and the negative electrode ear can be increased, thereby improving the energy density of the lithium battery; in addition, the coverage of the negative electrode sheet on the positive electrode sheet can be ensured, thereby avoiding the risk of lithium plating during circulation.

[0036] In addition to the technical problems solved by the embodiments of the present application, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions described above, other technical problems that can be solved by the battery provided by the embodiments of the present application, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0038] Figure 1 A schematic diagram of the structure of a pole piece in a battery provided in an embodiment of the present application;

[0039] Figure 2 A schematic cross-sectional perspective view of a structure of a battery provided in an embodiment of the present application;

[0040] Figure 3 A partial schematic diagram of another cross-sectional perspective structure of a battery provided in an embodiment of the present application;

[0041] Figure 4 A schematic diagram of a partial structure of a structure of a pole piece and a pole tab in a battery provided in an embodiment of the present application;

[0042] Figure 5 for Figure 4 Schematic diagram from another perspective;

[0043] Figure 6 A partial structural diagram of another structure of a pole piece and a pole tab in a battery provided in an embodiment of the present application;

[0044] Figure 7 for Figure 6 Schematic diagram from another perspective;

[0045] Figure 8 A partial structural diagram of yet another structure of a pole piece and a pole tab in a battery provided in an embodiment of the present application;

[0046] Figure 9 for Figure 5 、 Figure 7 and Figure 8 Schematic diagram of the cross section at AA in the middle;

[0047] Figure 10 for Figure 5 、 Figure 7 and Figure 8 Schematic diagram of the cross section at the middle BB;

[0048] Figure 11 for Figure 5 、 Figure 7 and Figure 8 Schematic diagram of the cross section at CC;

[0049] Figure 12 for Figure 10 A partial enlarged schematic diagram.

[0050] Reference numerals:

[0051] 100-battery;

[0052] 110 - positive electrode sheet; 111 - first recessed area; 112 - positive electrode tab;

[0053] 113 - first current collector; 114 - first active material layer;

[0054] 120-diaphragm;

[0055] 130 - negative electrode sheet; 131 - second recessed area; 132 - negative electrode ear;

[0056] 140-first covering layer;

[0057] 141-first protruding portion; 142-first thinned portion; 143-flat portion;

[0058] 144 - second thinned portion; 145 - second protruding portion;

[0059] 150 - second covering layer;

[0060] 160-first gap group; 161-first gap;

[0061] 170-second gap group; 171-second gap. DETAILED DESCRIPTION

[0062] In the prior art, during battery manufacturing, the presence of the tabs at the battery head exacerbates thermal shrinkage of the separator. This can lead to the separator being insufficient to separate the positive and negative electrodes, potentially causing safety issues such as internal short circuits. To address this issue, the separator width near the first end of the battery is typically increased to address the severe thermal shrinkage. However, increasing the separator width near the first end of the battery in the prior art reduces the battery's energy density.

[0063] In order to solve the above problems, the present application provides a battery, by setting a first recessed area and a positive electrode ear at the first end of the positive electrode sheet, and setting a second recessed area and a negative electrode ear at the first end of the negative electrode sheet, and the size of the first recessed area in the first direction is larger than the size of the second recessed area in the first direction; the size of the first recessed area in the second direction is larger than the size of the second recessed area in the second direction; part of the structure of the positive electrode ear is bent and set in the second recess, and part of the structure of the negative electrode ear is bent and set in the first recess. In this way, the space occupied by the positive electrode ear and the negative electrode ear at the first end of the battery after being bent can be reduced, and the area of ​​the positive electrode ear and the negative electrode ear can be increased, thereby improving the energy density of the lithium battery; in addition, the coverage of the negative electrode sheet on the positive electrode sheet can be ensured, avoiding the risk of lithium plating during circulation.

[0064] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0065] Please refer to Figures 1 to 3 As shown, an embodiment of the present application provides a battery 100, which includes a stacked core, which includes at least two electrode sheets and a diaphragm 120, and a diaphragm 120 is provided between two adjacent electrode sheets, wherein a positive electrode sheet 110 is provided on one side of the diaphragm 120, and a negative electrode sheet 130 is provided on the other side of the diaphragm 120, so as to isolate the positive electrode sheet 110 and the negative electrode sheet 130 through the diaphragm 120 to avoid direct contact between the positive electrode sheet 110 and the negative electrode sheet 130 and thus avoid a short circuit.

[0066] In addition, a positive electrode tab 112 is provided on the positive electrode sheet 110, and a negative electrode tab 132 is provided on the negative electrode sheet 130. The negative electrode tab 132 and the positive electrode tab 112 are located at the same end of the stacked core. For example, the negative electrode tab 132 and the positive electrode tab 112 are both located at the first end of the battery 100 (for example, which can be called the head of the battery 100). In this way, the positive electrode sheet 110 and the negative electrode sheet 130 are electrically connected to the external structure through the positive electrode tab 112 and the negative electrode tab 132, respectively.

[0067] In some embodiments, the first end of the positive electrode sheet 110 has a first recessed area 111; the first end of the negative electrode sheet 130 has a second recessed area 131, that is, the first recessed area 111 and the second recessed area 131 are located at the same end of the stacked core, and part of the structure of the positive electrode tab 112 is bent and disposed in the second recessed area 131, and part of the structure of the negative electrode tab 132 is bent and disposed in the first recessed area 111; wherein the negative electrode tab 132 extends through a first recessed area 111 on the positive electrode sheet 110 to be electrically connected to an external structure, and the positive electrode tab 112 extends through the negative electrode tab 111 to be electrically connected to an external structure. A second recessed area 131 on 32 extends out to be electrically connected to an external structure, wherein the size of the first recessed area 111 in the first direction is larger than the size of the second recessed area 131 in the first direction; the size of the first recessed area 111 in the second direction is larger than the size of the second recessed area 131 in the second direction. In this way, the space occupied by the positive and negative ears at the first end of the battery after being bent can be reduced, and the area of ​​the positive and negative ears can be increased, thereby improving the energy density of the lithium battery; in addition, the coverage of the negative electrode sheet on the positive electrode sheet can be ensured to avoid the risk of lithium plating during circulation.

[0068] In addition, the widths of the edges around the diaphragm 120 and the corresponding edges of the negative electrode sheet 130 are equal. For example, the outlines of the diaphragm 120 and the negative electrode sheet 130 are both rectangular. In this way, the distances between the edges of the diaphragm 120 and the corresponding edges of the negative electrode sheet 130 are equal. For example, Figure 2 In the figure, a first distance L1 is provided between the edges of the diaphragm 120 and the edges corresponding to the negative electrode sheet 130 , and the distances between the edges of the diaphragm 120 and the edges corresponding to the negative electrode sheet are all L1 .

[0069] For example, the outline shapes of the separator 120 and the negative electrode sheet 130 are both rectangular, wherein the separator 120 has a first edge, a second edge, a third edge and a fourth edge connected in sequence, and correspondingly, the negative electrode sheet 130 has a first edge, a second edge, a third edge and a fourth edge connected in sequence, so that the first edge of the separator 120 corresponds to the first edge of the negative electrode sheet 130, and the width between the first edge of the separator 120 and the first edge of the negative electrode sheet 130 is L1, the second edge of the separator 120 corresponds to the second edge of the negative electrode sheet 130, and the width between the second edge of the separator 120 and the second edge of the negative electrode sheet 130 is L1; the third edge of the separator 120 corresponds to the third edge of the negative electrode sheet 130, and the width between the third edge of the separator 120 and the third edge of the negative electrode sheet 130 is L1; the fourth edge of the separator 120 corresponds to the fourth edge of the negative electrode sheet 130, and the width between the fourth edge of the separator 120 and the fourth edge of the negative electrode sheet 130 is L1.

[0070] In some embodiments, as Figure 2 and Figure 3As shown, the width of the diaphragm 120 covering the negative electrode sheet 130 at all four sides of the stacked core is equal, and the width extending from the edge of the negative electrode sheet 130 is the first spacing L1, where the value of L1 is, for example, 0.5mm to 3mm. Compared with the conventional stacked core, the width of the first end of the diaphragm 120 is reduced. Taking a stacked core of 65mm (length) * 86mm (width) as an example, combined with the special-shaped electrode provided in the embodiment of the present application, the energy density can be increased by 1.6%.

[0071] In some embodiments, the electrode includes a current collector and an active material layer coated on the current collector, wherein the current collector refers to a structure or part that collects current. Exemplarily, the current collector includes metal foil, for example, the current collector includes copper foil, aluminum foil, etc.; the active material layer is mainly used to generate current, and the current collector is used to collect the current generated by the active material layer to form a larger current and output it to the outside.

[0072] Illustratively, the positive electrode sheet 110 includes a first current collector 113 and a first active material layer 114 , where the first current collector 113 is, for example, aluminum foil; the negative electrode sheet 130 includes a second current collector and a second active material layer, where the second current collector is, for example, copper foil.

[0073] During the manufacturing process of the battery 100, it is necessary to clean the active material layer on the positive electrode ear 112 and the negative electrode ear 132. In this way, when the external structures of the positive electrode ear 112 and the negative electrode ear 132 are welded, the active material layer can be prevented from affecting the welding effect. Among them, after cleaning the second active material layer on the negative electrode ear 132, the distance between the remaining second active material layer and the diaphragm 120 can be represented by L2.

[0074] The ratio of L2 to L1 can range from 1.2 to 1.7. Once the value of L1 is determined, the range of L2 values ​​can be determined based on this ratio. The second active material layer on the negative tab 132 can then be cleaned based on the size of L2. Maintaining the ratio of L2 to L1 within the range of 1.2 to 1.7 allows sufficient shrinkage margin for the separator 120 covering the tab, preventing short circuits caused by insufficient coverage of the separator 120. Above this range, significant loss of positive and negative active material occurs at the base of the tab, reducing the battery's energy density. Below this range, there is a safety risk of contraction of the separator 120 at this location, leading to contact and short circuits between the positive and negative electrode sheets 130.

[0075] Thus, it can be seen that in the embodiment of the present application, by providing the first recessed area 111 at the first end of the positive electrode sheet 110 and providing the second recessed area 131 at the first end of the negative electrode sheet 130, it is possible to make a portion of the structure of the positive electrode ear 112 bend in the first recessed area 111 and the second recessed area 131 and extend through one of the second recessed areas 131, while a portion of the structure of the negative electrode ear 132 bend in the second recessed area 131 and the first recessed area 111 and extend through one of the first recessed areas 111, so that the first end of the positive electrode sheet 110 has the first recessed area 111, and the first end of the negative electrode sheet 130 has the second recessed area 131, so that the portions of the structure of the positive electrode ear 112 and the negative electrode ear 132 are separated. The diaphragm 120 is bent and embedded in the second recessed area 131 and the first recessed area 111. In this way, there is no need to increase the width of the diaphragm 120 at the first end due to the presence of a tab at the first end of the battery 100, so that the width of the diaphragm 120 extending around the stacked core is equal, and the first distance between the edge of the diaphragm 120 and the edge of the negative electrode sheet 130 is smaller than the second distance between the edge of the first end of the positive electrode sheet 110 and the corresponding edge of the diaphragm 120. Therefore, while satisfying the thermal shrinkage of the diaphragm 120 without affecting the separation of the positive electrode sheet 110 and the negative electrode sheet 130 by the diaphragm 120, the area of ​​the positive electrode sheet 110 and the negative electrode sheet 130 can be increased, reducing the waste of space at the first end of the battery 100, thereby increasing the energy density of the lithium battery.

[0076] During the manufacturing process of the battery 100, part of the active material layer on the tab needs to be cleaned. Thus, the interface between the cleaned active material layer and the current collector is easily damaged and burrs are generated, thereby affecting the strength of the interface between the cleaned active material layer and the current collector. The generated burrs are easy to pierce the diaphragm 120, causing a short circuit between the positive electrode sheet 110 and the negative electrode sheet 130.

[0077] For example, when aluminum foil is used for the positive electrode sheet 110, the first active material layer 114 on the tab needs to be cleaned. After cleaning the first active material layer 114, there is a risk of burrs on the positive tab 112 from which the first active material layer 114 has been cleaned, close to the first current collector 113 from which the first active material layer 114 has not been cleaned. The burrs generated can easily pierce the diaphragm 120, causing a short circuit between the positive electrode sheet 110 and the negative electrode sheet 130.

[0078] For the above technical issues, please refer to Figure 2 and Figure 3As shown, along the second direction, the end of the positive electrode tab 112 near the positive electrode sheet 110 is covered with a first covering layer 140. The first covering layer 140 increases the thickness and strength of the connection area of ​​the positive electrode tab 112 near the positive electrode sheet 110 to prevent the connection area from breaking due to insufficient strength, which would affect the safety and reliability of the battery 100. In addition, the first covering layer 140 covers burrs on the positive electrode tab 112 at the connection area with the positive electrode sheet 110 to prevent the burrs from piercing the separator 120. The second direction is perpendicular to the first direction.

[0079] In some embodiments, please refer to Figure 4 and Figure 5 As shown, there is a gap between the first covering layer 140 and the first active material layer 114, and the gap is greater than or equal to 0 and less than or equal to the first preset width W1. It can be understood that, under ideal conditions, the gap between the first covering layer 140 and the first active material layer 114 is 0, that is, the first covering layer 140 and the first active material layer 114 are in direct contact and do not cover each other, so that the first covering layer 140 covers the first current collector 113 that contacts the positive electrode active material layer at the head of the stacked core, so that the first covering layer 140 can cover the burrs at the root of the positive electrode tab 112, so as to reduce the internal short circuit problem caused by the burrs piercing the diaphragm 120, and improve the strength of the root of the positive electrode tab 112, thereby improving the safety and reliability of the battery 100.

[0080] Since the gap between the first covering layer 140 and the first active material layer 114 is 0, the manufacturing process is difficult. Therefore, in some embodiments, such as Figure 6 and Figure 7 As shown, the gap between the first covering layer 140 and the first active material layer 114 is greater than 0 and less than the first preset width W1, that is, a portion of the first current collector 113 is exposed between the first covering layer 140 and the first active material layer 114. By controlling the size of the first preset width W1, the strength of the root of the positive electrode tab 112 is ensured, and the burrs do not pierce the diaphragm 120, and the problem of low energy density can be prevented from being covered by the first covering layer 140.

[0081] Exemplarily, the value of the first preset width W1 may be between 0 and 0.5 mm.

[0082] In other embodiments, Figure 8As shown, the first covering layer 140 is in direct contact with the first active material layer 114, and the first covering layer 140 covers a portion of the first active material layer 114, that is, there is an overlapping area between the first covering layer 140 and the first active material layer 114, and the width of the overlapping area is greater than or equal to 0 and less than or equal to the second preset width W2. In this way, the difficulty of the preparation process can be reduced, and the coverage of crack damage, burrs and other structures at the root of the positive electrode ear 112 can be ensured, thereby avoiding safety hazards caused by internal short circuits in the battery.

[0083] By controlling the size of the second preset width W2, the energy density of the battery can be maintained while ensuring the safety and reliability of the battery. For example, the value of the second preset width W2 can be between 0 and 0.5 mm.

[0084] In some embodiments, please refer back to Figure 2 and Figure 3 As shown, the width of the first covering layer 140 in the first direction is less than or equal to the width of the first recessed area 111 and the second recessed area 131 in the first direction, respectively. Exemplarily, the width of the first covering layer 140 in the first direction is less than the width of the first recessed area 111 in the first direction, and also less than the width of the second recessed area 131 in the first direction, to ensure that the first covering layer 140 can cover the burrs at the base of the positive electrode tab 112 while reducing the area covered by the first covering layer 140 on the first active material layer 114, thereby improving the safety and reliability of the battery 100 while increasing the battery's energy density.

[0085] Exemplarily, the ratio of the width of the first covering layer 140 in the first direction to the width of the first recessed area 111 and the second recessed area 131 in the first direction is 0.6 to 1; for example, the width of the first covering layer 140 in the first direction is 3 to 12 mm, therefore, the width of the first recessed area 111 and the second recessed area 131 in the first direction are both 5 to 24 mm.

[0086] like Figure 3 In the embodiment, when the corner between the bottom wall and the side wall of the first recessed area 111 is rounded, the radius of the rounded corner is represented by R, for example, and the width of the straight area of ​​the bottom wall of the first recessed area 111 in the first direction is represented by I, for example, and the size of the first covering layer 140 in the first direction is represented by L3, for example, then: L3≤2R+I.

[0087] In the embodiment of the present application, by controlling the ratio of the width of the first covering layer 140 in the first direction to the width of the first recessed area 111 and the second recessed area 131 in the first direction in the range of 0.6 to 1, it is possible to ensure that the burr area at the root of the positive electrode ear 112 is covered while improving the energy density; if the width L3 of the first covering layer 140 is greater than this range, the first covering layer 140 will cover part of the first active material layer 114, resulting in low energy density; and if the width L3 of the first covering layer 140 is less than this range, the coverage area of ​​the burr at the root of the positive electrode ear 112 is insufficient, and there is a risk of battery short circuit.

[0088] In some embodiments, as Figure 9 As shown, the structure of the first covering layer 140 in the first direction includes a first thinning portion 142, a flat portion 143 and a second thinning portion 144 connected in sequence; the first covering layer 140 also includes at least one of a first protrusion 141 and a second protrusion 145; that is, the first protrusion 141 and the second protrusion 145 may all exist, or only one of them may exist.

[0089] Exemplarily, when the first covering layer 140 includes a first protrusion 141 and a second protrusion 145, the first protrusion 141 is arranged at the end of the first thinning portion 142 away from the flat portion 143; the second protrusion 145 is arranged at the end of the second thinning portion 144 away from the flat portion 143; wherein, the first thinning portion 142 and the first protrusion 141 can be continuous or discontinuous; the second thinning portion 144 and the second protrusion 145 can be continuous or discontinuous; the arrangement of the first thinning portion 142 and the first protrusion 141, as well as the arrangement of the second thinning portion 144 and the second protrusion 145, can better cover the first active material layer 114 (i.e., the positive electrode active material layer) at the root of the positive electrode ear 112, to prevent the active material at the root of the ear from being subjected to force and falling off during the production process, resulting in loss of capacity.

[0090] In some embodiments, the first thinning portion 142 has a first protrusion 141 at one end away from the flat portion 143; and the second thinning portion 144 has a second protrusion 145 at one end away from the flat portion 143; the length of the flat portion 143 is greater than the length of the first protrusion 141, the first thinning portion 142, the second thinning portion 144 and the second protrusion 145 respectively.

[0091] For example, Figure 9 As shown in the figure, along the first direction, the size of the first protrusion 141 is represented by L4, the first thinned portion 142 is represented by L5, the flat portion 143 is represented by L6, the second thinned portion 144 is represented by L7, and the second protrusion 145 is represented by L8, so L3=L4+L5+L6+L7+L8; L6>L4, L5, L7, L8.

[0092] In some embodiments, the ratio of the sum of the lengths of the first protrusion 141 and the second protrusion 145 to the length of the first covering layer 140 is between 0.15 and 0.2; and / or the ratio of the sum of the lengths of the first thinned portion 142 and the second thinned portion 144 to the length of the first covering layer 140 is between 0.16 and 0.33. In this way, the first protrusion 141 and the second protrusion 145 can respectively increase the strength of the root of the electrode tab, and can better cover the first active material layer 114 (i.e., the positive electrode active material layer) at the root of the positive electrode tab 112, thereby preventing the active material at the root of the electrode tab from being forced to fall off during the production process, resulting in loss of capacity.

[0093] Illustratively, along the first direction, the size L4 of the first protrusion 141 ranges from 0 to 2 mm; the size L5 of the first thinned portion 142 ranges from 0.5 to 1 mm; the size L6 of the flat portion 143 ranges from 1 to 10 mm; the size L7 of the second thinned portion 144 ranges from 0.5 to 1 mm; and the size L8 of the second protrusion 145 ranges from 0 to 2 mm.

[0094] by Figure 5 、 Figure 7 and Figure 8 Take the section cut along AA as an example, please continue to refer to Figure 9 As shown, the maximum dimension of the first protrusion 141 in the third direction is greater than the maximum dimension of the first thinned portion 142 in the third direction. The third direction is perpendicular to the first direction and the second direction.

[0095] Please continue to refer to Figure 9 As shown, the maximum dimension of the second protrusion 145 in the third direction is greater than the maximum dimension of the second thinned portion 144 in the third direction.

[0096] Please continue to refer to Figure 9 As shown, the maximum dimension of the flat portion 143 in the third direction is larger than the maximum dimensions of the first thinned portion 142 and the second thinned portion 144 in the third direction.

[0097] In the above embodiment, by controlling the maximum sizes of the first protrusion 141 , the first thinned portion 142 , the flat portion 143 , the second thinned portion 144 and the second protrusion 145 , the size of the battery head can be prevented from increasing, thereby improving the energy density of the battery.

[0098] The following will be Figure 5 、 Figure 7 and Figure 8 Taking the corresponding embodiment as an example, the structural dimensions of the cross sections of the first cover layer 140 cut along AA, BB and CC are introduced.

[0099] Example 1: There is an exposed first current collector 113 between the first covering layer 140 and the first active material layer 114, such as Figure 5 As shown, the first covering layer 140 is cut along the first position (AA), the second position (BB) and the third position (CC), respectively, wherein the cross sections after cutting along the first position and the third position both include the first covering layer 140 and the first current collector 113, and the thickness of the first covering layer 140 at the first position is generally higher than the thickness of the first covering layer 140 at the third position.

[0100] For example, in the cross section of the first covering layer 140 cut along the first position (AA), please combine Figure 9 As shown, the thickness of the first protrusion 141 is represented by H1, and the range of H1 is 30 to 150 μm; the thickness of the first thinned portion 142 is represented by H2, and the range of H2 is 5 to 80 μm; the thickness of the flat portion 143 is represented by H3, and the range of H3 is 10 to 100 μm; the thickness of the second thinned portion 144 is represented by H4, and the range of H4 is 5 to 80 μm; the thickness of the second protrusion 145 is represented by H5, and the range of H5 is 30 to 150 μm.

[0101] In the cross section of the first covering layer 140 cut along the third position (CC), please combine Figure 11 As shown, the thickness H1 of the first protrusion 141 ranges from 5 to 50 μm; the thickness H2 of the first thinned portion 142 ranges from 0 to 25 μm; the thickness H3 of the flat portion 143 ranges from 2 to 30 μm; the thickness H4 of the second thinned portion 144 ranges from 0 to 25 μm; and the thickness H5 of the second protrusion 145 ranges from 5 to 50 μm.

[0102] Example 2: The first covering layer 140 is continuous with and does not cover the first active material layer 114. Figure 7 As shown, the first covering layer 140 is cut along the first position (AA), the second position (BB) and the third position (CC), respectively, wherein the cross sections after cutting along the first position (AA) and the third position (CC) both include the first covering layer 140 and the first current collector 113, and the thickness of the first covering layer 140 at the first position is generally higher than the thickness of the first covering layer 140 at the third position.

[0103] For example, in the cross section of the first covering layer 140 cut along the first position (AA), please combine Figure 9As shown, the thickness of the first protrusion 141 is represented by H1, and the range of H1 is 30 to 150 μm; the thickness of the first thinned portion 142 is represented by H2, and the range of H2 is 5 to 80 μm; the thickness of the flat portion 143 is represented by H3, and the range of H3 is 10 to 100 μm; the thickness of the second thinned portion 144 is represented by H4, and the range of H4 is 5 to 80 μm; the thickness of the second protrusion 145 is represented by H5, and the range of H5 is 30 to 150 μm.

[0104] In the cross section of the first covering layer 140 cut along the third position (CC), please combine Figure 11 As shown, the thickness H1 of the first protrusion 141 ranges from 5 to 50 μm; the thickness H2 of the first thinned portion 142 ranges from 0 to 25 μm; the thickness H3 of the flat portion 143 ranges from 2 to 30 μm; the thickness H4 of the second thinned portion 144 ranges from 0 to 25 μm; and the thickness H5 of the second protrusion 145 ranges from 5 to 50 μm.

[0105] Example 3: The first covering layer 140 is continuous with the first active material layer 114, and the first covering layer 140 covers a portion of the first active material layer 114. Figure 8 As shown, the first covering layer 140 is cut along the first position (AA), the second position (BB) and the third position (CC), respectively, wherein the cross sections after cutting along the first position and the third position both include the first covering layer 140 and the first current collector 113, and the thickness of the first covering layer 140 at the first position is generally higher than the thickness of the first covering layer 140 at the third position, and the cross section at the second position includes the first covering layer 140, the first active layer and the first current collector 113.

[0106] For example, in the cross section of the first covering layer 140 cut along the second position (BB), please combine Figure 10 As shown, the thickness of the first protrusion 141 is represented by H1, and the range of H1 is 5-50μm; the thickness of the first thinned portion 142 is represented by H2, and the range of H2 is 0-25μm; the thickness of the flat portion 143 is represented by H3, and the range of H3 is 2-30μm; the thickness of the second thinned portion 144 is represented by H4, and the range of H4 is 0-25μm; the thickness of the second protrusion 145 is represented by H5, and the range of H5 is 5-50μm. The ratio of the thickness of the first active layer at the second position (BB) to the thickness of the first active layer at other cross-section positions is 0.15-0.8. This ensures that the thickness at the second position (BB) after being covered by the first covering layer 140 is not excessive, thereby ensuring the energy density of the battery.

[0107] For example, in the cross section of the first covering layer 140 cut along the first position (AA), please combine Figure 9As shown, the thickness of the first protrusion 141 is represented by H1, and the range of H1 is 30 to 150 μm; the thickness of the first thinned portion 142 is represented by H2, and the range of H2 is 5 to 80 μm; the thickness of the flat portion 143 is represented by H3, and the range of H3 is 10 to 100 μm; the thickness of the second thinned portion 144 is represented by H4, and the range of H4 is 5 to 80 μm; the thickness of the second protrusion 145 is represented by H5, and the range of H5 is 30 to 150 μm.

[0108] In the cross section of the first covering layer 140 cut along the third position (CC), please combine Figure 11 As shown, the thickness H1 of the first protrusion 141 ranges from 5 to 50 μm; the thickness H2 of the first thinned portion 142 ranges from 0 to 25 μm; the thickness H3 of the flat portion 143 ranges from 2 to 30 μm; the thickness H4 of the second thinned portion 144 ranges from 0 to 25 μm; and the thickness H5 of the second protrusion 145 ranges from 5 to 50 μm.

[0109] In some embodiments, please refer to Figure 12 As shown, the angle θ1 between the first protrusion 141 and the first thinned portion 142 is 45° to 150°; the angle θ2 between the first thinned portion 142 and the flat portion 143 is 10° to 30°, so as to control the size of the angle between the first protrusion 141 and the first thinned portion 142, and the size of the angle between the first thinned portion 142 and the flat portion 143, thereby controlling the length dimension of the first protrusion 141, the first thinned portion 142 and the flat portion 143 in the first direction and the thickness dimension in the third direction respectively.

[0110] In some embodiments, as Figure 1 As shown in the figure, a second covering layer 150 is provided at the connection position between the negative electrode ear 132 and the negative electrode sheet 130. The second covering layer 150 is used to cover the burrs at the root of the negative electrode ear 132 and improve the strength of the root of the negative electrode ear 132. The structure and working principle of the second covering layer 150 can refer to the first covering layer 140 and will not be repeated here.

[0111] In some embodiments, the second current collector includes a second covering area and a second non-covering area, the second covering area is configured to cover the second active material layer, the negative electrode ear 132 is connected to the second non-covering area of ​​the second current collector, and the second covering layer 150 covers the connection position between the negative electrode ear 132 and the second current collector, so as to cover the burrs at the junction of the negative electrode ear 132 and the second active material layer through the second covering layer 150 and improve the strength of the junction.

[0112] In some embodiments, the first covering layer 140 includes one or more of a filler, an adhesive, and an additive. The filler may be a ceramic material such as alumina, boehmite, silica, CeO2, MgAl2O4, ZrO, TiO2, or a polymer material such as BOPP, PET, PI, etc. The adhesive is mainly used to provide adhesion between the components of the first covering layer 140 and between the first covering layer 140. The adhesive may be polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide (PI), perfluorosulfonic acid ionomer (Nafion), polyacrylic acid (PAA), polypropylene oxide, polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), polyvinyl butyral (PVB), polyacrylonitrile, polyvinyl chloride, polyvinylidene fluoride-co-hexafluoropropylene, polyethylene imine, polymethyl methacrylate, polybutyl acrylate, polyvinyl pyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate (EVA), polyarylate, polyphenylene terephthalate (PEP), polyvinyl chloride (PVDF), polyvinyl chloride-co-hexafluoropropylene (PVDF), polyvinyl chloride-co-hexafluoropropylene (PVB), polyvinyl chloride-co-hexafluoropropylene (PVDF), polyvinyl chloride-co-hexafluoropropylene (PVDF), polyvinyl chloride-co-hexafluoropropylene (PVA ...DF), polyvinyl chloride-co-hexafluoropropylene (PVA), polyvinyl chloride The invention also includes a group consisting of acryloyl-p-phenylenediamine polyethylene oxide, polyoxymethylene, SD-3, polyvinyl chloride, polyethylene, polypropylene, epoxy resin or nylon, methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC) and methyl cellulose (CMC), hydroxypropyl cellulose, diacetyl cellulose, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyacrylates (LA series), polyacrylic acid (PAA), sodium alginate (ALG), chitosan (CTS), carboxymethyl chitosan (C-CTS), water-based acrylic resin and mixtures thereof; the additive may be one or more of a thickener, a colorant, etc.: methyl cellulose (CMC), iron oxide, titanium, cobalt, molybdenum, chromium, nickel, bismuth vanadate and various composite inorganic pigments.

[0113] Also, please refer back to Figure 3 As shown, the first end of the diaphragm 120 has a first slit group 160 and a second slit group 170; the first slit group 160 includes two first slits 161, and the two first slits 161 are spaced apart along the first direction, and the projection of the positive electrode ear 112 on the diaphragm 120 is located between the two first slits 161; the second slit group 170 includes two second slits 171, and the two second slits 171 are spaced apart along the first direction, and the projection of the negative electrode ear 132 on the diaphragm 120 is located between the two second slits 171. In this way, the first slit 161 and the second slit 171 can provide a certain bending and deformation space for the bending of the diaphragm 120.

[0114] In the battery provided in the embodiment of the present application, a first recessed area and a positive electrode ear are provided at the first end of the positive electrode sheet, and a second recessed area and a negative electrode ear are provided at the first end of the negative electrode sheet, and the size of the first recessed area in the first direction is larger than the size of the second recessed area in the first direction; the size of the first recessed area in the second direction is larger than the size of the second recessed area in the second direction; part of the structure of the positive electrode ear is bent and provided in the second recess, and part of the structure of the negative electrode ear is bent and provided in the first recess. In this way, the space occupied by the positive electrode ear and the negative electrode ear at the first end of the battery after being bent can be reduced, and the area of ​​the positive electrode ear and the negative electrode ear can be increased, thereby improving the energy density of the lithium battery; in addition, the coverage of the negative electrode sheet on the positive electrode sheet can be ensured, thereby avoiding the risk of lithium plating during circulation.

[0115] The various embodiments or implementation methods in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referenced to each other.

[0116] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations 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 any one or more embodiments or examples.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery, characterized in that: include: A positive electrode sheet (110), a separator (120), and a negative electrode sheet (130) are stacked in sequence; The first end of the positive electrode sheet (110) has a first recessed area (111) and a positive electrode tab (112); the first end of the negative electrode sheet (130) has a second recessed area (131) and a negative electrode tab (132); a portion of the structure of the positive electrode tab (112) is bent and arranged in the second recessed area (131), and a portion of the structure of the negative electrode tab (132) is bent and arranged in the first recessed area (111); The size of the first recessed area (111) in the first direction is greater than the size of the second recessed area (131) in the first direction; the size of the first recessed area (111) in the second direction is greater than the size of the second recessed area (131) in the second direction.

2. The battery according to claim 1, characterized in that Along the second direction, one end of the positive electrode tab (112) close to the positive electrode sheet (110) has a first covering layer (140).

3. The battery according to claim 2, characterized in that The positive electrode sheet (110) includes a first current collector (113) and a first active material layer (114) disposed on the first current collector (113); There is a gap between the first covering layer (140) and the first active material layer (114); or there is an overlapping area between the first covering layer (140) and the first active material layer (114).

4. The battery according to claim 2 or 3, characterized in that The structure of the first covering layer (140) in the first direction comprises a first thinned portion (142), a flat portion (143) and a second thinned portion (144) connected in sequence; The first covering layer (140) further includes at least one of a first protrusion (141) and a second protrusion (145); The first protrusion (141) is arranged at one end of the first thinned portion (142) away from the flat portion (143); and the second protrusion (145) is arranged at one end of the second thinned portion (144) away from the flat portion (143).

5. The battery according to claim 4, characterized in that The first thinned portion (142) has a first protrusion (141) at one end away from the flat portion (143); and the second thinned portion (144) has a second protrusion (145) at one end away from the flat portion (143); The length of the flat portion (143) is respectively greater than the lengths of the first protruding portion (141), the first thinned portion (142), the second thinned portion (144), and the second protruding portion (145).

6. The battery according to claim 5, characterized in that The ratio of the sum of the lengths of the first protrusion (141) and the second protrusion (145) to the length of the first covering layer (140) is 0.15 to 0.2; and / or The ratio of the sum of the lengths of the first thinned portion (142) and the second thinned portion (144) to the length of the first covering layer (140) is 0.16 to 0.

33.

7. The battery according to claim 5, characterized in that Include at least one of the following: The maximum dimension of the first protruding portion (141) in the third direction is greater than the maximum dimension of the first thinned portion (142) in the third direction; The maximum dimension of the second protrusion (145) in the third direction is greater than the maximum dimension of the second thinned portion (144) in the third direction; The maximum dimension of the flat portion (143) in the third direction is larger than the maximum dimensions of the first thinned portion (142) and the second thinned portion (144) in the third direction.

8. The battery according to claim 5, characterized in that The size of the first protrusion (141) in the first direction is 0 to 2 mm; The size of the first thinned portion (142) in the first direction is 0.5 to 1 mm; The size of the flat portion (143) in the first direction is 1 to 10 mm; The size of the second thinned portion (144) in the first direction is 0.5 to 1 mm; The size of the second protrusion (145) in the first direction is 0-2 mm.

9. The battery according to claim 6, characterized in that The included angle between the first protruding portion (141) and the first thinned portion (142) is 45° to 150°; and the included angle between the first thinned portion (142) and the flat portion (143) is 10° to 30°.

10. The battery according to claim 2 or 3, characterized in that The width of the first covering layer (140) in the first direction is less than or equal to the width of the first recessed area (111) and the second recessed area (131) in the first direction respectively.

11. The battery according to claim 10, characterized in that The ratio of the width of the first covering layer (140) in the first direction to the width of the first recessed area (111) and the second recessed area (131) in the first direction is 0.6 to 1.

12. The battery according to any one of claims 1 to 3, characterized in that The first end of the diaphragm (120) has a first slit group (160) and a second slit group (170); The first slit group (160) includes two first slits (161), the two first slits (161) are spaced apart along a first direction, and the projection of the positive electrode tab (112) on the diaphragm (120) is located between the two first slits (161); The second slit group (170) includes two second slits (171), the two second slits (171) are spaced apart along the first direction, and the projection of the negative electrode tab (132) on the separator (120) is located between the two second slits (171).

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