Sheet structures, pole pieces, wound cells and batteries

Abstract

The utility model discloses a sheet structure, a pole piece, a wound cell and a battery, wherein the sheet structure comprises a current collector and a conductive coating disposed on both sides of the current collector, the sheet structure is divided into a winding straight section and a winding curved section alternately distributed along its length direction, and the conductive coating on at least one side of at least one winding curved section is provided with a first pit area, and the first pit area is located on the side of the conductive coating facing away from the current collector. The technical solution of the utility model improves the purple spot lithium precipitation situation in the corner area of ​​the wound cell and improves the cycle performance of the wound cell.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a sheet structure, a pole piece, a winding type battery core and a battery. Background Art

[0002] Nowadays, all countries are vigorously developing green and efficient secondary batteries. As a new type of secondary battery, lithium-ion battery has the advantages of high energy density and power density, high working voltage, light weight, small size, long cycle life, good safety, and green environmental protection. It has broad application prospects in portable appliances, power tools, large energy storage, electric transportation power supply, etc.

[0003] At present, lithium-ion batteries for consumer electronic products basically use wound cells, the middle area of ​​the wound cell is a flat area, and the two sides are corner areas (i.e., arc-shaped bending areas). As people's requirements for the charging rate of lithium-ion batteries become higher and higher, the requirements for the structural performance of lithium-ion batteries are also getting higher and higher. When existing lithium-ion batteries are charged at a high rate, the corner area of ​​the wound cell is under high pressure, which can easily squeeze the electrolyte between the positive and negative electrodes out of the corner area, resulting in insufficient electrolyte between the positive and negative electrodes in the corner area, which in turn causes the electrode in the corner area to be unable to embed lithium, forming purple spots, and eventually developing into lithium precipitation, affecting the cycle performance of the wound cell. Utility Model Content

[0004] The utility model provides a sheet structure, a pole piece, a wound battery cell and a battery, aiming to improve the purple spot lithium precipitation in the corner area of ​​the wound battery cell and enhance the cycle performance of the wound battery cell.

[0005] To achieve the above-mentioned purpose, the utility model proposes a sheet structure, including a current collector and a conductive coating arranged on both sides of the current collector, the sheet structure is divided into a winding straight section and a winding curved section alternately distributed along its length direction, and the conductive coating on at least one side of at least one of the winding curved sections is provided with a first pit area, and the first pit area is located on the side of the conductive coating facing away from the current collector.

[0006] In some embodiments, along the length direction of the sheet-like structure, the length of the winding curved section gradually increases or decreases;

[0007] and / or, the area of ​​the first pit region is consistent with the area of ​​the winding curved section where the first pit region is located;

[0008] and / or, the first pit area includes a plurality of strip-shaped grooves evenly spaced apart;

[0009] and or, the first pit region comprises a plurality of concentric annular grooves evenly spaced apart;

[0010] And / or, the first recessed area includes a plurality of liquid storage holes distributed in an array;

[0011] And / or, the first recessed area comprises one or more grooves.

[0012] In some embodiments, the conductive coating on at least one side of each of the winding curved segments is provided with the first concave region;

[0013] And / or, a blank section not coated with the conductive coating is provided on one side of the current collector, and the blank section is located at one end of the current collector;

[0014] And / or, the depth of the pit in the first pit area is greater than or equal to two-fifths of the thickness of the conductive coating and less than or equal to half of the thickness of the conductive coating.

[0015] The utility model also proposes a pole piece, comprising the above-mentioned sheet structure and an active material layer, wherein the active material layer is coated on the conductive coating, and the active material layer on at least one side of the winding curved section is provided with a second pit area, and the second pit area is arranged on the side of the active material layer facing away from the conductive coating, and the second pit area corresponds to the first pit area in position and has the same shape.

[0016] In some embodiments, at least one side of each of the winding curved segments is provided with the third concave pit area;

[0017] And / or, the electrode sheet is a negative electrode sheet or a positive electrode sheet.

[0018] The utility model also provides a pole piece, comprising winding straight sections and winding curved sections alternately distributed along the length direction thereof, and at least one side of at least one of the winding curved sections is provided with a third pit area.

[0019] In some embodiments, along the length direction of the pole piece, the length of the winding curved section gradually increases or decreases;

[0020] and / or, the area of ​​the third pit region is consistent with the area of ​​the winding curved section where the third pit region is located;

[0021] And / or, the third pit area includes a plurality of strip-shaped grooves evenly spaced apart;

[0022] and or, the third pit region comprises a plurality of concentric annular grooves evenly spaced apart;

[0023] And / or, the third recessed area includes a plurality of liquid storage holes distributed in an array;

[0024] And / or, the third recessed area comprises one or more grooves.

[0025] In some embodiments, at least one side of each of the winding curved segments is provided with the first concave pit area;

[0026] And / or, the electrode sheet is a negative electrode sheet or a positive electrode sheet.

[0027] The utility model also proposes a wound battery cell, comprising an electrode assembly formed by winding a negative electrode sheet, a separator and a positive electrode sheet together, wherein the electrode assembly comprises a plane area and corner areas located on both sides of the plane area, the negative electrode sheet and / or the positive electrode sheet is the above-mentioned electrode sheet, and the winding bending section is located in the corner area.

[0028] The utility model also provides a battery, comprising a shell and the above-mentioned wound battery core, wherein the wound battery core is installed in the shell.

[0029] The technical solution of the sheet structure of the utility model is to provide a first concave area on the conductive coating on at least one side of at least one winding bending section, so that a second concave area corresponding to the position and having the same shape as the first concave area is obtained on the active material layer of the pole piece made by the sheet structure. Therefore, when the pole piece made by the sheet structure of this embodiment is applied to a wound battery cell, the second concave area on the active material layer is located in the corner area of ​​the wound battery cell, and the electrolyte can be accommodated in the second concave area; during the charge and discharge cycle of the wound battery cell, when the pole piece expands and squeezes in the corner area, the electrolyte in the second concave area will not be squeezed away, which can improve the electrolyte shortage in the corner area caused by expansion and squeezing, thereby achieving the effect of improving the purple spot lithium precipitation in the corner area of ​​the wound battery cell and improving the cycle performance of the wound battery cell. Moreover, when the sheet structure of the utility model has more winding bending sections in the first pit area, the electrode piece made of the sheet structure has more prominent effect in improving the purple spot lithium precipitation in the corner area of ​​the wound battery cell, and the cycle performance of the wound battery cell is improved more. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic cross-sectional structure diagram of a sheet structure in one embodiment of the utility model;

[0031] Figure 2 It is a top view of a part of the sheet structure in the first embodiment of the utility model;

[0032] Figure 3 It is a top view of a part of the sheet structure in the first embodiment of the utility model;

[0033] Figure 4 A top view of a portion of the sheet structure in the third embodiment of the present invention;

[0034] Figure 5 It is a schematic cross-sectional structure diagram of a pole piece in one embodiment of the utility model;

[0035] Figure 6 is a schematic cross-sectional structure diagram of a pole piece in another embodiment of the utility model;

[0036] Figure 7 It is a schematic structural diagram of a wound battery cell in one embodiment of the utility model.

[0037] Explanation of the accompanying drawings: 10 - current collector, 20 - conductive coating, 30 - active material layer, 21 - first pit area, 211 - strip groove, 212 - annular groove, 213 - liquid storage hole, 31 - second pit area, 32 - third pit area, D1 - winding straight section, D2 - winding curved section, Q1 - plane area, Q2 - corner area. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0039] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0040] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0041] In addition, the descriptions of "first", "second", etc. in the present utility model are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0042] The utility model provides a sheet structure, which is mainly used for manufacturing pole pieces of a wound-type battery core.

[0043] See also Figure 1 In this embodiment, the sheet structure includes a current collector 10 and a conductive coating 20 disposed on both sides of the current collector 10. The sheet structure is divided into a winding straight section D1 and a winding curved section D2 that are alternately distributed along its length direction, wherein the winding curved section D2 is a portion of the sheet structure corresponding to the corner area Q2 of the wound battery cell, that is, the pole piece made of the sheet structure of this embodiment is applied to the wound battery cell (reference Figure 7 , when the wound battery cell includes a plane area Q1 and corner areas Q2 located on both sides of the plane area Q1), the winding bending section D2 of the sheet structure corresponds to the corner area Q2 of the wound battery cell. When the sheet structure of this embodiment is used to make a pole piece, it is only necessary to coat the corresponding active material layer 30 on the conductive coating 20 of the sheet structure through a coating device, and then perform subsequent treatments such as rolling. The sheet structure of this embodiment can be used to make negative electrode sheets, and can also be used to make positive electrode sheets; when used to make negative electrode sheets, the negative electrode active material is coated on the conductive coating 20, and when used to make positive electrode sheets, the positive electrode active material is coated on the conductive coating 20.

[0044] In the sheet structure of the present embodiment, the conductive coating 20 on at least one side of at least one winding curved section D2 is provided with a first concave region 21, and the first concave region 21 is located on the side of the conductive coating 20 facing away from the current collector 10. The first concave region 21 may be a region where a concave structure of any shape (such as a strip groove, an annular groove, a hole, etc.) is provided. In some embodiments, the sheet structure may be provided with a first concave region 21 on the conductive coating 20 on one or both sides of all the winding curved sections D2, or may be provided with a first concave region 21 on the conductive coating 20 on one or both sides of some of the winding curved sections D2. Figure 1 and 5 Since the conductive coating 20 is provided with a first concave area 21, when the active material layer 30 is coated on the sheet structure, when it is coated on the sheet structure having the first concave area 21, the active material layer 30 will form a concave structure corresponding in shape and size to the concave structure in the first concave area 21, so that a second concave area 31 corresponding in position and consistent in shape to the first concave area 21 is obtained on the active material layer 30.

[0045] When the pole piece made of the sheet structure of this embodiment is applied to a wound battery cell, the second pit area 31 on the active material layer 30 is located in the corner area Q2 of the wound battery cell, and the second pit area 31 can accommodate electrolyte; during the charge and discharge cycle of the wound battery cell, when the pole piece expands and squeezes in the corner area Q2, the electrolyte in the second pit area 31 will not be squeezed away, which can improve the electrolyte shortage in the corner area Q2 due to expansion and squeezing, thereby achieving the effect of improving the purple spot lithium precipitation in the corner area Q2 of the wound battery cell and improving the cycle performance of the wound battery cell. The more winding bending sections D2 of the first pit area 21 of the sheet structure of this embodiment are set, the more prominent the improvement effect of the pole piece made of the sheet structure on the purple spot lithium precipitation in the corner area Q2 of the wound battery cell is, and the greater the improvement of the cycle performance of the wound battery cell is.

[0046] In some embodiments, along the length direction of the sheet structure, the length of each winding curved section D2 gradually increases or decreases; because the length of the arc located in the corner area Q2 of the wound battery cell gradually increases from the inside to the outside of the electrode sheet in the wound battery cell, therefore, the scheme of this embodiment designs the length of each winding curved section D2 to gradually change along the length direction of the sheet structure, so that the length of each winding curved section D2 of the sheet structure of this embodiment can be consistent with the arc length of each layer of electrode sheet in the corner area Q2 of the wound battery cell. In some embodiments, the length of each winding curved section D2 of the sheet structure can be matched one by one with the arc length of each layer of curved part of a certain electrode sheet (negative electrode sheet or positive electrode sheet) in the wound battery cell located in the corner area Q2, and the winding straight section D1 of the sheet structure is consistent with the length of the plane area Q1 of the wound battery cell.

[0047] In some embodiments, a blank section (not shown in the figure) not coated with the conductive coating 20 is provided on one side of the current collector 10, and the blank section is located at one end of the current collector 10. Since the winding start section of the negative electrode sheet only needs to be provided with the negative electrode active material on one side, and the winding end section of the positive electrode sheet only needs to be provided with the positive electrode active material on one side, the sheet structure of this embodiment leaves a blank section not coated with the conductive coating 20 on one side of the current collector 10, and when the sheet structure is used to make the negative electrode sheet, the blank section is used as the winding start section of the negative electrode sheet, and when the sheet structure is used to make the negative electrode sheet, the blank section is used as the winding end section of the positive electrode sheet; in this way, the use amount of the conductive coating 20 can be saved, and the raw material cost can be saved.

[0048] When the sheet structure is used to make a negative electrode sheet, the conductive coating 20 may be made of conductive graphite with a large particle size and a small specific surface area. For example, the conductive graphite has the following characteristics: a particle size of 2-6 μm, a specific surface area of ​​10-20 m 2 / g, compacted density is 0.5-1.2mg / cm 3, using the above-mentioned conductive graphite with large particle size and small surface area, in the rolling process of making the electrode sheet with a sheet structure, the volume change of the conductive coating 20 after rolling is small, and the pits in the first pit area 21 are not easy to be flattened. When the sheet structure is used to make the positive electrode sheet, the conductive coating 20 can be made of a suitable material so that the volume change of the conductive coating 20 is small when rolling.

[0049] In some embodiments, the pit depth in the first pit region 21 may be greater than or equal to two-fifths of the thickness of the conductive coating 20, and less than or equal to half of the thickness of the conductive coating 20. In this way, the conductive performance of the conductive coating 20 provided with the first pit region 21 is ensured, and the pits of the second pit region 31 formed on the active material layer 30 due to the first pit region 21 can be sufficient to accommodate the electrolyte. Of course, in other embodiments, the pit depth in the first pit region 21 can also be other sizes that are smaller than the thickness of the conductive coating 20.

[0050] In some embodiments, the area of ​​the first pit region 21 is consistent with the area of ​​the winding bend section D2 where it is located, that is, the first pit region 21 covers the winding bend section D2 where it is located. In this way, the area of ​​the first pit region 21 is maximized. When making the electrode, the area of ​​the corresponding second pit region 31 formed on the active material layer 30 is also maximized, so that the corner area Q2 of the wound battery cell has a greater ability to retain electrolyte, better improves the purple spot lithium precipitation situation in the corner area Q2 of the wound battery cell, and greatly improves the cycle performance of the wound battery cell.

[0051] See also Figure 2 In some embodiments, the first pit area 21 may include a plurality of strip grooves 211 evenly spaced. In this embodiment, the recessed structure in the first pit area 21 uses a plurality of strip grooves 211, and each strip groove 211 is evenly spaced, so that the recessed structure in the first pit area 21 is evenly distributed, so that when the sheet structure is made into a pole sheet, the ability of the second pit area 31 of the active material layer 30 to store electrolyte is evenly distributed, wherein the spacing between the strip grooves 211 can be designed according to demand. In this embodiment, the strip grooves 211 may be straight, or the strip grooves 211 may be curved (such as arc, wavy line, sawtooth, etc.); each strip groove 211 may be extended along the width direction of the winding curved section D2, or may be extended along the length direction of the winding curved section D2, or may be extended along other directions.

[0052] See also Figure 3In some embodiments, the first concave pit area 21 may include a plurality of concentric annular grooves 212 evenly spaced. In this embodiment, the concave structure in the first concave pit area 21 uses a plurality of annular grooves 212, and the annular grooves 212 may be circular annular grooves, square annular grooves, etc. The annular grooves 212 are concentric and evenly spaced, so that the concave area in the first concave pit area 21 is evenly distributed, so that when the sheet structure is made into a pole sheet, the capacity of the second concave pit area 31 of the active material layer 30 to store electrolyte is evenly distributed, wherein the spacing between the annular grooves 212 can be designed according to requirements.

[0053] See also Figure 4 In some embodiments, the first concave region 21 includes a plurality of liquid storage holes 213 distributed in an array, such as each liquid storage hole 213 is arranged in a dot matrix distribution. In this embodiment, the concave structure in the first concave region 21 adopts a plurality of liquid storage holes 213, and the plurality of liquid storage holes 213 are distributed in an array, so that the concave structure in the first concave region 21 is evenly distributed, so that when the sheet structure is made into a pole sheet, the ability of the second concave region 31 of the active material layer 30 to store electrolyte is evenly distributed, wherein the distribution spacing between the liquid storage holes 213 can be designed according to demand, and the size of the liquid storage holes 213 can also be adjusted according to demand, and the liquid storage holes 213 can be circular holes, square holes, or holes of other shapes.

[0054] In some embodiments, the first pit area 21 includes one or more grooves, that is, the concave structure of the first pit area 21 adopts one or more grooves. When it is a groove, the area of ​​the groove can be designed to be consistent with the area of ​​the winding bending section D2 where it is located, so that the pole piece made of the sheet structure, the second pit area 31 on the active material layer 30 can accommodate a larger amount of electrolyte, better improve the purple spot lithium precipitation situation in the corner area Q2 of the wound battery cell, and further improve the cycle performance of the wound battery cell. When the concave structure is a plurality of grooves, each groove can be a groove structure of various shapes.

[0055] It should be noted that the above-mentioned various embodiments of the sheet structure of the utility model can be arbitrarily combined or combined to form a new embodiment when there is no contradiction or conflict between them.

[0056] Two methods of providing the first recessed area 21 on the conductive coating 20 of the wound curved section D2 of the sheet-like structure are described below.

[0057] Method 1: On the primer gravure roller, according to the required size, pit distribution density and pit size (including depth or length and other dimensions) of each first pit area 21, the corresponding protrusion distribution position, as well as the distribution density and size of each protrusion are engraved in advance. When applying the conductive coating 20, the protrusion will squeeze out part of the slurry. After coating, pits will be left at the corresponding position (i.e., the first pit area 21). For example, using the above-mentioned special primer gravure roller, a conductive coating 20 (such as conductive graphite) of a certain thickness (such as 1 to 15 μm) is coated on the winding bend D2 of the current collector 10 (such as copper foil).

[0058] Method 2: The conductive coating 20 is normally coated on the current collector 10 in an existing manner, and then before the conductive coating 20 is dried, a workpiece or casting with a small protrusion is used to press the winding curved section D2 to form a first pit area 21 on the conductive coating 20 of the winding curved section D2. The material of the workpiece or casting can be metal, ceramic or organic polymer.

[0059] The method of making the pole piece with the above-mentioned sheet structure is: use an extrusion coater to coat the active material layer 30 on the surface of the above-mentioned sheet structure. Because the slurry extrusion amount of the extrusion coater is fixed, due to the existence of the first pit area 21, pits will appear on the active material layer 30 to form a second pit area 31 in the winding bending section D2. After the pole piece made as above is made into a wound battery cell, the second pit area 31 on the active material layer 30 allows more electrolyte to be accommodated between the pole pieces, and when it is expanded and squeezed, the electrolyte contained in the pit of the second pit area 31 will not be squeezed out, ensuring that the electrolyte in the corner area Q2 of the wound battery cell will not dry up, improving the purple spot lithium precipitation of the pole piece in the corner area Q2, and improving the cycle performance of the wound battery cell.

[0060] See also Figure 5 The utility model also proposes a pole piece, comprising the above-mentioned sheet structure and an active material layer 30, the active material layer 30 is coated on the conductive coating 20, and the active material layer 30 on at least one side of the winding bending section D2 is provided with a second pit area 31, the second pit area 31 is arranged on the side of the active material layer 30 facing away from the conductive coating 20, and the second pit area 31 corresponds to the first pit area 21 in position and has the same shape.

[0061] When the pole piece of the present embodiment is applied to a wound battery cell, the second concave area 31 on the active material layer 30 is located in the corner area Q2 of the wound battery cell, and the second concave area 31 can accommodate electrolyte; during the charge and discharge cycle of the wound battery cell, when the pole piece expands and squeezes in the corner area Q2, the electrolyte in the second concave area 31 will not be squeezed away, which can improve the electrolyte shortage in the corner area Q2 due to expansion and squeezing, thereby achieving the effect of improving the purple spot lithium precipitation in the corner area Q2 of the wound battery cell and improving the cycle performance of the wound battery cell. The more winding bending sections D2 of the first concave area 21 are set on the sheet structure of the pole piece of the present embodiment, the more corresponding second concave areas 31 on the pole piece, the more prominent the improvement effect of the pole piece on the purple spot lithium precipitation in the corner area Q2 of the wound battery cell, and the greater the improvement of the cycle performance of the wound battery cell.

[0062] In addition, since the pole piece of this embodiment adopts all the technical solutions of all the embodiments of the sheet structure, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0063] The electrode sheet of this embodiment can be a negative electrode sheet or a positive electrode sheet.

[0064] See also Figure 6 The utility model further proposes a pole piece, comprising winding straight sections D1 and winding curved sections D2 alternately distributed along its length direction, and at least one side of at least one winding curved section D2 is provided with a third pit area 32.

[0065] The third concave region 32 may be a region where a concave structure of any shape (such as a strip groove, an annular groove, a hole, etc.) is provided. In some embodiments, the pole piece may be provided with the third concave region 32 on one or both sides of all the winding curved sections D2, or may be provided with the third concave region 32 on one or both sides of part of the winding curved sections D2.

[0066] When the pole piece of this embodiment is applied to a wound battery cell, each winding bend section D2 is located in the corner area Q2 of the wound battery cell, and the third pit area 32 set on the surface of the winding bend section D2 can accommodate electrolyte; during the charge and discharge cycle of the wound battery cell, when the pole piece expands and squeezes in the corner area Q2, the electrolyte in the third pit area 32 will not be squeezed away, which can improve the electrolyte shortage in the corner area Q2 caused by expansion and squeezing, thereby achieving the effect of improving the purple spot lithium precipitation in the corner area Q2 of the wound battery cell and improving the cycle performance of the wound battery cell. The more winding bend sections D2 of the pole piece of this embodiment are set in the third pit area 32, the more prominent the improvement effect of the pole piece on the purple spot lithium precipitation in the corner area Q2 of the wound battery cell is, and the greater the improvement of the cycle performance of the wound battery cell is.

[0067] The electrode sheet of this embodiment can be a negative electrode sheet or a positive electrode sheet.

[0068] In some embodiments, the length of the winding curved section D2 gradually increases or decreases along the length direction of the pole piece; since the arc length of the corner area Q2 of the wound battery cell gradually increases from the inside to the outside, the scheme of this embodiment designs the length of each winding curved section D2 to gradually change along the length direction of the pole piece, so that the length of each winding curved section D2 of the pole piece of this embodiment can match the gradually increasing arc length of the corner area Q2 of the wound battery cell. In some embodiments, the length of each winding curved section D2 of the pole piece can be matched with the arc length of each layer of the curved portion of the corner area Q2 of the wound battery cell, and the winding straight section D1 of the sheet structure is consistent with the length of the plane area Q1 of the wound battery cell.

[0069] In some embodiments, the area of ​​the third pit area 32 is consistent with the area of ​​the winding bend section D2 where it is located, that is, the third pit area 32 covers the winding bend section D2 where it is located. In this way, the area of ​​the third pit area 32 is maximized, so that the corner area Q2 of the wound battery cell has a greater ability to retain electrolyte, better improves the purple spot lithium precipitation situation in the corner area Q2 of the wound battery cell, and greatly improves the cycle performance of the wound battery cell.

[0070] In some embodiments, the third pit area 32 may include a plurality of strip grooves evenly spaced apart (the specific structure of which can be referred to in Figure 2 ). In this embodiment, the recessed structure in the third recessed area 32 adopts a plurality of strip grooves, and each strip groove is distributed at equal intervals, so that the recessed structure in the third recessed area 32 is evenly distributed, thereby ensuring that the liquid storage distribution at each position of the corner area Q2 of the wound battery cell is more even, wherein the spacing between the strip grooves can be designed according to demand. In this embodiment, the strip grooves can be straight, or the strip grooves can be curved (such as arc, wavy line, sawtooth, etc.); each strip groove can be extended along the width direction of the winding curved section D2, or can be extended along the length direction of the winding curved section D2, or can be extended along other directions.

[0071] In some embodiments, the third recessed area 32 may include a plurality of concentric annular grooves evenly spaced apart (the specific structure of which may be referred to in Figure 3 ). In this embodiment, the concave structure in the third concave pit area 32 adopts a plurality of annular grooves, which may be circular annular grooves, square annular grooves, etc. The annular grooves are concentric and evenly spaced, so that the concave areas in the third concave pit area 32 are evenly distributed, thereby ensuring that the liquid storage distribution at each position of the corner area Q2 of the wound battery cell is more even, wherein the spacing between the annular grooves can be designed according to requirements.

[0072] In some embodiments, the third recessed area 32 includes a plurality of liquid storage holes distributed in an array (the specific structure of which can be referred to in Figure 4 ), such as each liquid storage hole is arranged in a dot matrix distribution. In this embodiment, the concave structure in the third concave pit area 32 adopts a plurality of liquid storage holes, and the plurality of liquid storage holes are distributed in an array, so that the concave structure in the third concave pit area 32 is evenly distributed, thereby ensuring that the liquid storage distribution at each position of the corner area Q2 of the wound battery cell is more even, wherein the distribution spacing between the liquid storage holes can be designed according to demand, and the size of the liquid storage holes can also be adjusted according to demand, and the liquid storage holes can be circular holes, square holes, or holes of other shapes.

[0073] In some embodiments, the third pit area 32 includes one or more grooves, that is, the concave structure of the third pit area 32 adopts one or more grooves. When there is one groove, the area of ​​the groove can be designed to be consistent with the area of ​​the winding bending section D2 where it is located, so that the third pit area 32 can accommodate a larger amount of electrolyte, better improve the purple spot lithium precipitation situation in the corner area Q2 of the wound battery cell, and further improve the cycle performance of the wound battery cell. When the concave structure is a plurality of grooves, each groove can be a groove structure of various shapes.

[0074] The third recessed area 32 of the pole piece of the present embodiment can be formed by the same process as that of the first recessed area of ​​the sheet structure, which will not be described in detail here.

[0075] It should be noted that the above-mentioned various embodiments of the pole piece of the utility model can be arbitrarily combined or combined to form a new embodiment when there is no contradiction or conflict between them.

[0076] The utility model also proposes a wound battery cell, including an electrode assembly formed by winding a negative electrode sheet, a separator and a positive electrode sheet together, the electrode assembly includes a plane area Q1 and a corner area Q2 located on both sides of the plane area Q1, the negative electrode sheet and / or the positive electrode sheet is the above-mentioned electrode sheet, and the winding bending section D2 is located in the corner area Q2. The specific structure of the electrode sheet refers to the above-mentioned embodiment. Since the wound battery cell adopts all the technical solutions of all the above-mentioned electrode sheet embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here. The wound battery cell of the utility model can be used to make batteries for various electronic products, such as mobile phone batteries, tablet batteries, etc.

[0077] In some embodiments, the winding curved sections D2 of the pole piece are all located in the corner area Q2 of the wound battery cell, and the winding straight sections D1 of the pole piece are all located in the plane area Q1 of the wound battery cell.

[0078] In some embodiments, the wound battery cell can be a structure in which only the negative electrode sheet is the electrode sheet of the above embodiment, the wound battery cell can be a structure in which only the positive electrode sheet is the electrode sheet of the above embodiment, or the wound battery cell can be a structure in which the negative electrode sheet is the electrode sheet of the above embodiment and the positive electrode sheet is also the electrode sheet structure of the above embodiment.

[0079] The utility model also proposes a battery, including a shell and the above-mentioned wound battery cell, the wound battery cell is installed in the shell, and the specific structure of the wound battery cell refers to the above-mentioned embodiment. Since the battery adopts all the technical solutions of all the embodiments of the above-mentioned wound battery cell, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0080] The above description is only a partial or preferred embodiment of the present invention. Neither the text nor the drawings can limit the scope of protection of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the overall concept of the present invention, or direct / indirect application in other related technical fields are included in the scope of protection of the present invention.

Claims

1. A sheet structure, characterized in that: It includes a current collector and a conductive coating arranged on both sides of the current collector, the sheet structure is divided into a winding straight section and a winding curved section alternately distributed along its length direction, and the conductive coating on at least one side of at least one of the winding curved sections is provided with a first pit area, and the first pit area is located on the side of the conductive coating facing away from the current collector.

2. The sheet structure according to claim 1, characterized in that Along the length direction of the sheet structure, the length of the winding curved section gradually increases or decreases; and / or, the area of ​​the first pit region is consistent with the area of ​​the winding curved section where the first pit region is located; and / or, the first pit area includes a plurality of strip-shaped grooves evenly spaced apart; and or, the first pit region comprises a plurality of concentric annular grooves evenly spaced apart; And / or, the first recessed area includes a plurality of liquid storage holes distributed in an array; And / or, the first recessed area comprises one or more grooves.

3. The sheet structure according to claim 1, characterized in that The conductive coating on at least one side of each of the winding curved sections is provided with the first concave pit area; And / or, a blank section not coated with the conductive coating is provided on one side of the current collector, and the blank section is located at one end of the current collector; And / or, the depth of the pit in the first pit area is greater than or equal to two-fifths of the thickness of the conductive coating and less than or equal to half of the thickness of the conductive coating.

4. A pole piece, characterized in that: It comprises the sheet structure and active material layer as described in any one of claims 1 to 3, wherein the active material layer is coated on the conductive coating, and the active material layer on at least one side of the winding bending section is provided with a second pit area, and the second pit area is arranged on the side of the active material layer facing away from the conductive coating, and the second pit area corresponds to the first pit area in position and has the same shape.

5. The pole piece according to claim 4, characterized in that: The electrode sheet is a negative electrode sheet or a positive electrode sheet.

6. A pole piece, characterized in that: The invention comprises winding straight sections and winding curved sections which are alternately distributed along the length direction thereof, and at least one side of at least one winding curved section is provided with a third pit area.

7. The pole piece according to claim 6, characterized in that: Along the length direction of the pole piece, the length of the winding curved section gradually increases or decreases; and / or, the area of ​​the third pit region is consistent with the area of ​​the winding curved section where the third pit region is located; And / or, the third pit area includes a plurality of strip-shaped grooves evenly spaced apart; and or, the third pit region comprises a plurality of concentric annular grooves evenly spaced apart; And / or, the third recessed area includes a plurality of liquid storage holes distributed in an array; And / or, the third recessed area comprises one or more grooves.

8. The pole piece according to claim 6, characterized in that: At least one side of each of the winding curved sections is provided with the third pit area; And / or, the electrode sheet is a negative electrode sheet or a positive electrode sheet.

9. A wound battery cell, comprising an electrode assembly formed by winding a negative electrode sheet, a separator and a positive electrode sheet together, wherein the electrode assembly comprises a plane area and corner areas located on both sides of the plane area, characterized in that: The negative electrode sheet and / or the positive electrode sheet is the electrode sheet according to any one of claims 4 to 8, and the winding bend section is located in the corner area.

10. A battery, characterized in that: The invention comprises a shell and the wound battery core according to claim 9, wherein the wound battery core is installed in the shell.

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