Battery cell and battery

Abstract

The utility model discloses an electric core and a battery, which are applied to the technical field of batteries, a positive plate comprises a positive current collector and a positive active layer, a negative plate comprises a negative current collector and a negative active layer, the positive active layer is positioned on the surface of one side of the positive current collector facing the negative plate, and the negative active layer is positioned on the surface of one side of the negative current collector facing the positive plate; the surface of one side, facing the negative plate, of the winding tail part of the positive plate is provided with an empty foil area which is not coated with an active material, the termination gummed paper is provided with a first part and a second part along the winding direction, at least part of the first part covers the tail end of the positive active layer, at least part of the empty foil area is covered by the second part, and the thickness of the first part is smaller than that of the second part. The termination gummed paper is used, the first part with the thin thickness is used for covering the positive electrode active layer located on the upper layer of the first step structure, the second part with the thick thickness is attached to the empty foil area located on the lower layer of the first step structure, and the thickness influence caused by the gummed paper can be reduced by reducing the thickness of the gummed paper covering the positive electrode active layer.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a battery core and a battery. Background Art

[0002] As the best commercial energy storage solution today, the volumetric energy density, cycle life, charge and discharge rate performance and safety performance of rechargeable batteries have always been the main focus of rechargeable battery research.

[0003] In rechargeable batteries, adhesive tape is often applied to the end of the positive electrode to prevent burrs from piercing the diaphragm and causing a short circuit, thereby improving safety performance. However, the adhesive tape has a certain thickness, which will affect the energy density of the battery; the adhesive layer of the adhesive tape and the electrolyte are both organic substances. Under conditions of high temperature and high voltage, the adhesive layer of the adhesive tape is prone to interact with the electrolyte, causing problems such as pore blockage in the diaphragm at the edge of the adhesive tape and powder loss at the positive electrode at the edge of the adhesive tape. At present, in order to further improve the energy density of rechargeable batteries, the negative electrode sheet is made thicker and thicker, but this leads to the problem of difficulty in infiltration of the electrolyte, resulting in poor battery charge and discharge performance.

[0004] Therefore, how to solve the problem of reduced energy density caused by the finishing tape of thick electrode batteries and the adverse effects of the adhesive layer on active materials is an urgent problem that technicians in this field need to solve. Utility Model Content

[0005] The utility model aims to provide a battery core, which can reduce the thickness influence caused by adhesive tape; the utility model also provides a battery, which can reduce the thickness influence caused by adhesive tape.

[0006] In order to solve the above technical problems, the utility model provides a battery core, including a termination tape, and a positive electrode sheet, a separator and a negative electrode sheet stacked and wound;

[0007] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer, and the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer, wherein the positive electrode active layer is located on the surface of the positive electrode current collector facing the negative electrode sheet, and the negative electrode active layer is located on the surface of the negative electrode current collector facing the positive electrode sheet;

[0008] The winding tail of the positive electrode sheet has an empty foil area on the surface of one side facing the negative electrode sheet without being coated with active material. Along the winding direction, the termination tape has a first part and a second part, at least part of the first part covers the tail end of the positive electrode active layer, and the second part covers at least part of the empty foil area, wherein the thickness of the first part is less than the thickness of the second part.

[0009] Optionally, the first part includes a first substrate layer, and the second part includes a second substrate layer and an adhesive layer which are stacked, and the adhesive layer is located on a side of the second substrate layer away from the negative electrode sheet.

[0010] Optionally, the first substrate layer and the second substrate layer are integrated.

[0011] Optionally, the area of ​​the first part is S1, the area of ​​the second part is S2, and S1 and S2 satisfy: 0.3≤S1 / (S1+S2)≤0.95.

[0012] Optionally, along the thickness direction of the battery cell, the thickness of the second portion of the termination tape is not greater than the thickness of the positive electrode active layer; and / or along the width direction of the positive electrode sheet, the width of the termination tape is greater than the width of the positive electrode sheet.

[0013] Optionally, along the winding direction, a first groove is provided on the surface of the tail of the negative electrode active layer facing the positive electrode sheet;

[0014] Along the thickness direction of the battery core, a projection of a head portion of the first portion away from the second portion is located within a projection of the first groove.

[0015] Optionally, a second step structure is formed on a side of the first groove facing the head of the negative electrode sheet, and a side wall of the second step structure is arranged along an edge of a side of the first portion away from the second portion.

[0016] Optionally, along the thickness direction of the battery core, the depth of the first groove is not less than the thickness of the first portion.

[0017] Optionally, a plurality of first recesses are provided on the surface of the negative electrode active layer, the first recesses extend along the width direction of the negative electrode sheet, and the plurality of first recesses are arranged at intervals along the length direction of the negative electrode sheet.

[0018] Optionally, a plurality of second recesses are provided on the tail end surface of the positive electrode active layer;

[0019] Along the thickness direction of the battery core, projections of the plurality of second recesses are all located within the projection of the first portion.

[0020] Optionally, the second recessed portion is a groove, and a plurality of the grooves are distributed in an array on the surface of the positive electrode active layer.

[0021] The present application also provides a battery, comprising a shell and a battery cell as described in any one of the above items, wherein the battery cell is installed in the shell.

[0022] The utility model provides a battery cell, comprising a termination tape, and a positive electrode sheet, a separator and a negative electrode sheet that are stacked and wound; the positive electrode sheet comprises a positive electrode collector and a positive electrode active layer, the negative electrode sheet comprises a negative electrode collector and a negative electrode active layer, the positive electrode active layer is located on the surface of the positive electrode collector on the side facing the negative electrode sheet, and the negative electrode active layer is located on the surface of the negative electrode collector on the side facing the positive electrode sheet; the winding tail of the positive electrode sheet has an empty foil area that is not coated with active material on the surface facing the negative electrode sheet, and along the winding direction, the termination tape has a first part and a second part, at least part of the first part covers the tail end of the positive electrode active layer, and the second part covers at least part of the empty foil area, wherein the thickness of the first part is less than the thickness of the second part.

[0023] By using termination tape, and using a thinner first part to cover the positive electrode active layer located on the upper layer of the first step structure, and using a thicker second part to adhere to the empty foil area on the lower layer of the first step structure, the thickness influence of the tape can be reduced by reducing the thickness of the tape covering the positive electrode active layer.

[0024] The utility model also provides a battery, which also has the above-mentioned beneficial effects, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the utility model or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a schematic diagram of the structure of the pressure-sensitive adhesive paper used in the prior art;

[0027] Figure 2 A schematic diagram of the structure of a battery cell provided in this embodiment;

[0028] Figure 3 for Figure 2 A schematic diagram of the side view of the structure of the tail of the middle pole piece;

[0029] Figure 4 for Figure 3 Schematic diagram of the top view of the positive electrode sheet;

[0030] Figure 5 for Figure 3 Schematic diagram of the structure of the middle negative electrode plate viewed from above;

[0031] Figure 6 for Figure 2 The schematic diagram of the structure of the stopper tape;

[0032] Figure 7A schematic diagram of a top view of a specific positive electrode sheet provided in this embodiment;

[0033] Figure 8 A schematic diagram of the structure of a specific battery cell provided in this embodiment;

[0034] Fig. 9 An enlarged view of the tail of a pole piece in a battery cell provided in this embodiment;

[0035] Fig.10 A schematic diagram of a specific negative electrode sheet structure from a bottom view provided in this embodiment;

[0036] Fig.11 A schematic diagram of a specific side view structure of a battery cell provided in this embodiment;

[0037] Fig.12 This is another specific schematic diagram of the top view structure of the positive electrode sheet provided in this embodiment.

[0038] In the figure: 11. positive electrode current collector, 12. positive electrode active layer, 13. positive electrode ear, 14. second recess, 21. negative electrode current collector, 22. negative electrode active layer, 23. negative electrode ear, 24. first groove, 25. first recess, 3. termination tape, 31. substrate, 32. bonding layer, 4. side wall. DETAILED DESCRIPTION

[0039] The core of the utility model is to provide a battery cell; wherein the battery cell and battery provided by the present application are preferably lithium-ion batteries; of course, they can also be sodium-ion batteries, potassium-ion batteries, semi-solid batteries, or solid-state batteries, etc.; in addition, the battery cell and battery provided by the present application are preferably wound cores, and of course, they can also be stacked cores, etc., without too much limitation here. The following embodiments are described with lithium-ion wound battery cells as preferred embodiments.

[0040] In the prior art, rechargeable batteries often use adhesive tape to stick at the end of the positive electrode of the battery cell to prevent burrs from piercing the diaphragm and causing a short circuit, thereby improving safety performance; at the same time, the negative electrode is ensured to exceed the positive electrode to prevent lithium deposition. Figure 1 , Figure 1 Schematic diagram of the structure of pressure-sensitive adhesive tape used in the prior art. Figure 1 It can be seen that the surface of one side of the substrate 31 of the pressure-sensitive adhesive tape is completely coated with the adhesive layer 32. However, the adhesive tape has a certain thickness, which will affect the energy density of the battery; the adhesive layer 32 of the adhesive tape and the electrolyte are both organic substances. Under conditions of high temperature and high voltage, the adhesive layer 32 of the adhesive tape is easy to interact with the electrolyte, resulting in pore blockage of the diaphragm at the edge of the adhesive tape, powder loss at the positive electrode at the edge of the adhesive tape, and lithium deposition at the negative electrode corresponding to the edge of the adhesive tape.

[0041] The utility model provides a battery cell comprising a termination tape, and a stacked and wound positive electrode sheet, a separator and a negative electrode sheet; the positive electrode sheet comprises a positive electrode collector and a positive electrode active layer, the negative electrode sheet comprises a negative electrode collector and a negative electrode active layer, the positive electrode active layer is located on the surface of the positive electrode collector facing the negative electrode sheet, and the negative electrode active layer is located on the surface of the negative electrode collector facing the positive electrode sheet; the winding tail of the positive electrode sheet has an empty foil area without active material coating on the surface facing the negative electrode sheet, and along the winding direction, the termination tape has a first part and a second part, at least part of the first part covers the tail end of the positive electrode active layer, and the second part covers at least part of the empty foil area, wherein the thickness of the first part is less than the thickness of the second part.

[0042] By using termination tape, and using a thinner first part to cover the positive electrode active layer located on the upper layer of the first step structure, and using a thicker second part to adhere to the empty foil area on the lower layer of the first step structure, the thickness of the tape covering the positive electrode active layer can be reduced, thereby reducing the thickness impact of the tape.

[0043] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0044] Embodiment 1

[0045] Please refer to Figures 2 to 11 , Figure 2 A schematic diagram of the structure of a battery cell provided in this embodiment; Figure 3 for Figure 2 A schematic diagram of the side view of the structure of the tail of the middle pole piece; Figure 4 for Figure 3 Schematic diagram of the top view of the positive electrode sheet; Figure 5 for Figure 3 Schematic diagram of the structure of the middle negative electrode plate viewed from above; Figure 6 for Figure 2 The schematic diagram of the structure of the stopper tape; Figure 7 A schematic diagram of a top view of a specific positive electrode sheet provided in this embodiment; Figure 8 A schematic diagram of the structure of a specific battery cell provided in this embodiment; Fig. 9 A schematic diagram of a specific negative electrode sheet structure from a bottom view provided in this embodiment; Fig.10 A schematic diagram of a specific side view structure of a battery cell provided in this embodiment; Fig.11 This is another specific schematic diagram of the top view structure of the positive electrode sheet provided in this embodiment.

[0046] See also Figures 2 to 3 In an embodiment of the utility model, the battery cell includes a termination tape 3, and a positive electrode sheet, a separator and a negative electrode sheet that are stacked and wound; the positive electrode sheet includes a positive electrode collector 11 and a positive electrode active layer 12, and the negative electrode sheet includes a negative electrode collector 21 and a negative electrode active layer 22, the positive electrode active layer 12 is located on the surface of the positive electrode collector 11 facing the negative electrode sheet, and the negative electrode active layer 22 is located on the surface of the negative electrode collector 21 facing the positive electrode sheet; the winding tail of the positive electrode sheet has an empty foil area that is not coated with active material on the surface of the negative electrode sheet facing the negative electrode sheet, and along the winding direction, the termination tape 3 has a first part and a second part, at least part of the first part covers the tail end of the positive electrode active layer 12, and the second part covers at least part of the empty foil area, wherein the thickness of the first part is less than the thickness of the second part.

[0047] The above-mentioned positive electrode sheet and negative electrode sheet arranged opposite to each other constitute the main structure of the battery cell. Usually, the above-mentioned positive electrode sheet and the negative electrode sheet are arranged in a wound manner, and a separator is arranged between the positive electrode sheet and the negative electrode sheet to form a wound battery cell. Usually, the positive electrode sheet and the negative electrode sheet are generally strip-shaped, so the positive electrode sheet and the negative electrode sheet both have a head and a tail, wherein the head of the positive electrode sheet is arranged opposite to the head of the negative electrode sheet, and the tail of the positive electrode sheet is arranged opposite to the tail of the negative electrode sheet.

[0048] See also Figure 4 as well as Figure 5 , the positive electrode sheet includes a positive electrode collector 11 and a positive electrode active layer 12 disposed on the surface of the positive electrode collector 11, and the corresponding negative electrode sheet includes a negative electrode collector 21 and a negative electrode active layer 22 disposed on the surface of the negative electrode collector 21. In this embodiment, the positive electrode active layer 12 is located on the surface of the positive electrode collector 11 facing the negative electrode sheet, and the negative electrode active layer 22 is located on the surface of the negative electrode collector 21 facing the positive electrode sheet, that is, the positive electrode active layer 12 and the negative electrode active layer 22 are disposed oppositely. For a wound cell, since both sides of the positive electrode collector 11 in the middle part have the negative electrode collector 21 disposed oppositely, and conversely, both sides of the negative electrode collector 21 have the positive electrode collector 11 disposed oppositely, the positive electrode active layer 12 is usually disposed on both sides of the positive electrode collector 11 in the middle part, and the negative electrode active layer 22 is usually disposed on both sides of the negative electrode collector 21 in the middle part. Of course, since the tail of the positive electrode sheet is usually no longer located in the middle of the battery cell, the positive electrode active layer 12 is usually only provided on one side.

[0049] The specific materials of the positive electrode current collector 11 , the positive electrode active layer 12 , the negative electrode current collector 21 , and the negative electrode active layer 22 can be set according to actual conditions and are not specifically limited here.

[0050] In this embodiment, the positive electrode current collector 11 at the tail of the positive electrode sheet will exceed the coverage of the positive electrode active layer 12, so that the surface of the winding tail of the positive electrode sheet facing the negative electrode sheet has an empty foil area without active material coating, and the empty foil area is formed on the surface of the positive electrode current collector 11 facing the negative electrode sheet, thereby forming a first step structure at the tail of the positive electrode sheet. The upper material of the first step structure is the positive electrode active layer 12, and the lower material is the positive electrode current collector 11, thereby forming a first step structure that exposes the lower positive electrode current collector 11. In this embodiment, the termination tape 3 is specifically attached to the first step structure to prevent burrs from piercing the diaphragm and causing a short circuit, thereby improving safety performance.

[0051] In this embodiment, the termination tape 3 has a first portion and a second portion arranged along the winding direction, and the thickness of the first portion is less than the thickness of the second portion. In this embodiment, at least part of the first portion covers the tail end of the positive electrode active layer 12, and the second portion covers at least part of the empty foil area, that is, at least part of the first portion with a relatively thin thickness will cover the upper surface of the first step structure, and the thicker area will cover at least part of the lower surface of the first step structure. By reducing the thickness of the tape covering the positive electrode active layer 12, the thickness effect caused by the tape can be reduced. Usually, only the first portion will cover the tail end of the positive electrode active layer 12.

[0052] In this embodiment, the first part includes a first substrate layer, and the second part includes a second substrate layer and an adhesive layer 32 which are stacked, and the adhesive layer 32 is located on the side of the second substrate layer away from the negative electrode sheet. The above-mentioned first part needs to include at least one substrate layer, namely the first substrate layer. The first part may also include an adhesive layer 32, and the adhesive layer is specifically located on the side of the first substrate layer facing the positive electrode sheet; the second part needs to include at least a second substrate layer and an adhesive layer 32. In order to achieve that the thickness of the first part is less than the thickness of the second part, three structures are specifically provided in this embodiment. In the first one, the first substrate layer and the second substrate layer are formed of the same material, but the thickness of the first substrate layer is less than the thickness of the second substrate layer, so that the thickness of the first part of the termination tape is less than the thickness of the second part.

[0053] Second, an adhesive layer 32 is also provided on the surface of the first substrate layer, and the thickness of the adhesive layer 32 located on the surface of the first substrate layer is less than the thickness of the adhesive layer 32 located on the surface of the second substrate layer, so that the thickness of the first part of the termination tape 3 is less than the thickness of the second part.

[0054] The third type is that the surface of the first substrate layer is not provided with the adhesive layer 32, that is, the first part only includes the first substrate layer, and the second part includes the second substrate layer and the adhesive layer 32, and the thickness of the first part is ensured to be less than that of the second part by reducing the adhesive layer in the first part. The termination tape 3 of this structure is usually also called zebra tape.

[0055] In this embodiment, in order to allow the stopper tape 3 to more comprehensively cover the winding tail of the positive electrode sheet, the first substrate layer and the second substrate layer are usually integrated to ensure the overall integrity of the stopper tape 3 .

[0056] Preferably, in this embodiment, the zebra tape of the third structure is selected as the termination tape 3, because it can not only realize that the thickness of the first part is less than the thickness of the second part, but also reduce the contact between the adhesive layer 32 and the positive electrode active layer 12, and reduce the adhesive layer 32 from interacting with the electrolyte, resulting in the problem of pore blockage of the tape edge diaphragm, powder falling off the positive electrode edge, and lithium deposition on the negative electrode. Figure 6 The stop tape 3 used in this embodiment is specifically composed of a substrate 31 and an adhesive layer 32 disposed on one side of the substrate 31. The surface of the side of the substrate 31 where the adhesive layer 32 is disposed is not entirely covered by the adhesive layer 32, but only covers a portion of the area. The area where the adhesive layer 32 is disposed is called the adhesive area in this embodiment, which is the second part mentioned above; and the area where the adhesive layer 32 is not disposed is the non-adhesive area, which is the first part mentioned above. Obviously, the thickness of the adhesive area is greater than the thickness of the non-adhesive area. When the thickness of the substrate 31 in the first part is equal to that of the second part, the difference between the thicknesses is equal to the thickness of the adhesive layer 32.

[0057] In this embodiment, assuming that the area of ​​the first portion is S1 and the area of ​​the second portion is S2, then S1 and S2 generally satisfy: 0.3≤S1 / (S1+S2)≤0.95.

[0058] In this way, the first portion having a certain width can be effectively covered with the active material while ensuring that the stop tape 3 can be firmly adhered to the empty foil area.

[0059] Preferably, S1 / (S1+S2)=0.5. That is, the widths of the first portion and the second portion are consistent, which can balance the thickness gradient change of the positive electrode active layer and the empty foil area, thereby reducing the breakage phenomenon at the tail of the positive electrode sheet.

[0060] Alternatively, the value of S1 / (S1+S2) may be any value such as 0.4, 0.6, 0.7, 0.8, or 0.9.

[0061] In this embodiment, the termination tape 3 of this structure is attached to the first step structure at the tail of the positive electrode sheet, wherein the non-glue area covers the positive electrode active layer 12, and the glue area covers the positive electrode current collector 11, that is, the thinner area of ​​the termination tape 3 will cover the upper surface of the first step structure, and the thicker area will cover the lower surface of the first step structure. The first step structure is used to accommodate the bonding layer 32, reducing the effect of the termination tape 3 on the thickness of the battery cell. Only the above-mentioned non-glue area corresponds to the positive electrode active layer 12, which can reduce the thickness effect of the tape, and at the same time reduce the adhesive layer 32 from interacting with the electrolyte, resulting in the problem of pore blocking of the tape edge diaphragm, powder falling off the positive electrode edge, and lithium precipitation of the negative electrode.

[0062] In this embodiment, along the thickness direction of the battery cell, the thickness of the second part of the termination tape 3 is usually not greater than the thickness of the positive electrode active layer 12; and / or along the width direction of the positive electrode sheet, the width of the termination tape 3 is usually greater than the width of the positive electrode sheet. When the thickness of the second part of the termination tape 3 is not greater than the thickness of the positive electrode active layer 12, the height difference of the first step structure formed at the tail of the positive electrode sheet can accommodate the second part of the termination tape 3, thereby reducing the impact of the termination tape 3 on the thickness of the battery cell. The width of the termination tape 3 is greater than the width of the positive electrode sheet, which can ensure that the termination tape 3 completely covers the tail of the positive electrode sheet to avoid exposing the positive electrode active layer 12.

[0063] Taking zebra tape as the termination tape 3 as an example, the thickness of the substrate 31 in the termination tape 3 is usually 4μm~50μm, and the thickness of the adhesive layer 32 is usually 2μm~40μm. Usually, the thickness of the adhesive layer 32 of the termination tape 3 is not greater than the thickness of the positive electrode active layer 12, so as to reduce the influence of the termination tape 3 on the battery structure. Assuming that the area of ​​the glue area is S1 and the area of ​​the surface of one side of the entire substrate 31 is S, then S1 / S=30%~95%, that is, the area of ​​the glue area accounts for 30%~95% of the area of ​​the entire termination tape 3. The substrate 31 of the termination tape 3 can specifically include one or more of polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polyimide (PI); the adhesive layer 32 includes one or more of natural rubber, synthetic rubber, polyacrylate, polypropylene, polyisobutylene, and styrene-isoprene copolymer. Of course, the specific materials of the substrate 31 and the adhesive layer 32 are not specifically limited in this embodiment and depend on the specific situation.

[0064] See also Figures 7 to 9In this embodiment, the glue-containing area of ​​the termination tape 3 is attached to the positive current collector 11 along the outer side of the edge of the positive active layer 12, that is, the adhesive layer 32 in the termination tape 3 will be arranged along the side wall 4 of the first step structure. Under normal circumstances, the length direction of the termination tape 3 will be arranged along the width direction of the positive electrode sheet, so as to be attached to the surface of the first step structure. In this embodiment, the overall width of the termination tape 3 is usually 5mm~50mm. Assuming that the width of the positive electrode sheet is L1 and the length of the termination tape 3 is L2, then L1≤L2≤L1+8mm, that is, the length of the above-mentioned termination tape 3 is usually not less than the width of the positive electrode substrate, and does not exceed the width of the positive electrode sheet 8mm. The width of the above-mentioned non-glue area is usually 2mm~8mm, that is, the width of the termination tape 3 covering the positive active layer 12 is usually 2mm~8mm, so that the surface capacity loss is caused by the termination tape 3 covering too much positive active layer 12.

[0065] When the positive electrode sheet and the negative electrode sheet are wound to form a wound battery cell, assuming that the distance between the zebra sticker and the arc edge of the wound battery cell is L3, then L3≤arc width R+10 mm. The purpose of this structure is to limit the position of the zebra sticker to the arc end of the wound battery cell to reduce the impact of the zebra sticker on the thickness of the wound battery cell, and at the same time to increase the distance between the zebra sticker and the pole ear in the battery cell. In this embodiment, the positive electrode sheet is provided with a positive pole ear 13, the negative electrode sheet is provided with a negative pole ear 23, and the above-mentioned termination tape 3 is staggered with the pole ears of the battery cell, that is, the above-mentioned termination tape 3, the positive pole ear 13 and the negative pole ear 23 need to be staggered to avoid the termination tape 3 affecting the pole ears.

[0066] In this embodiment, in order to avoid burrs and ensure that the area of ​​the positive active layer 12 is smaller than that of the negative active layer 22, it is necessary to affix the above-mentioned termination tape 3 to the junction between the positive active layer 12 and the positive current collector 11, that is, the above-mentioned first step structure, wherein the portion in contact with the positive active layer 12 corresponds to the glue-free area of ​​the termination tape 3.

[0067] Preferably, the adhesive area of ​​the termination tape 3 is attached to the positive current collector 11 along the outer side of the edge of the positive active layer 12. However, in actual situations, although only the adhesive-free area covers the positive active layer 12 and the adhesive area covers the positive current collector 11, due to assembly accuracy issues, there may be a gap between the positive active layer 12 and the adhesive layer 32, or the adhesive layer 32 may be attached to the surface of the positive active layer 12. On this basis, in this embodiment, the width of the adhesive-free area in the zebra sticker is set as w1, and the width of the positive active layer 12 covered by the adhesive-free area is set as w2. Generally, this embodiment needs to ensure that w2-3mm≤w1≤w2+3mm, that is, the difference between the width of the positive active layer 12 covered by the adhesive-free area and the width of the adhesive-free area in the zebra sticker is within ±3mm.

[0068] See also Fig. 9 , further, in this embodiment, along the winding direction, the tail of the negative electrode active layer 22 is provided with a first groove 24 on the surface of one side facing the positive electrode sheet; along the thickness direction of the battery cell, the projection of the head of the first part away from the second part is located within the projection of the first groove 24. The first groove 24 is used to accommodate the termination tape 3, which is usually used to accommodate the glue-free area of ​​the termination tape 3. Specifically, in this embodiment, the first groove 24 can be formed with a second step structure on the side facing the head of the negative electrode sheet. From the figure, the second step structure is an inverted step structure. The side wall 4 of the second step structure is preferably arranged along the edge of the first part away from the second part, so that the upper layer of the second step structure, that is, the bottom of the first groove 24, will correspond to the glue-free area, that is, the area covered by the positive electrode active layer 12, to accommodate the termination tape 3. Combined with the above-mentioned first step structure, the termination tape 3 can be accommodated in the groove at the tail of the battery cell. When the side wall 4 of the second step structure is arranged along the edge of the first part away from the second part, more negative electrode active layers 22 can be retained as much as possible to increase the capacity of the battery cell.

[0069] In this embodiment, along the thickness direction of the battery cell, the depth of the first groove 24 is usually not less than the thickness of the first portion. Taking zebra tape as the termination tape 3 as an example, the depth of the first groove 24 is usually not less than the thickness of the substrate 31 to avoid the effect of the tape setting on the thickness of the battery cell tail. At the same time, the depth of the first groove 24 is usually less than the thickness of the negative electrode material, that is, the negative electrode current collector 21 will not be exposed at the first groove 24. In this embodiment, the first groove 24 usually penetrates the negative electrode active layer 22 along the width direction of the negative electrode sheet to form a strip-shaped groove.

[0070] Specifically, in this embodiment, a plurality of first recesses 25 are provided on the surface of the negative electrode active layer 22, and the first recesses 25 extend along the width direction of the negative electrode sheet, and the plurality of first recesses 25 are arranged at intervals along the length direction of the negative electrode sheet. A first recess 25 may be provided on the surface of the negative electrode sheet facing the positive electrode sheet, and the first recess 25 usually penetrates the negative electrode active layer 22 along the width direction of the negative electrode sheet. The function of the first recess 25 is to improve the wettability of the electrolyte to the negative electrode active material. The first recess 25 is specifically provided along the width direction of the negative electrode sheet, and specifically penetrates the negative electrode active layer 22 along the width direction of the negative electrode sheet to form a strip-shaped groove. In this embodiment, the negative electrode sheet is usually provided with a plurality of the first recesses 25, and the first recesses 25 are evenly distributed on the surface of the negative electrode active layer 22, that is, the first recesses 25 can be distributed periodically and equidistantly.

[0071] See also Fig.10 as well as Fig.11In this embodiment, the negative electrode active layer 22 has an area that is not in contact with the termination tape 3 and an area that is in contact with the termination tape 3. The above-mentioned first recess 25 is arranged in the area that is not in contact with the termination tape 3. The first recess 25 is usually distributed periodically. The spacing size of the first recess 25 is a1, the width of the first recess 25 is b1, and the depth of the first recess 25 is c1, wherein usually 0<a1≤5mm; 0<b1≤500μm; 0<c1≤50μm. The above-mentioned first groove 24 is provided in the contact area with the termination tape 3. Assuming that the width of the first groove 24 is b2, and the depth of the first groove 24 is c2, then in the present embodiment, the width of the positive electrode active layer 12 covered by the non-glue area is w2≤b2≤w2+5mm, the thickness of the tape substrate 31 is ≤c2≤the thickness of the tape substrate 31+50μm, and usually b1<b2, that is, the width of the above-mentioned first groove 24 will specifically correspond to the width of the positive electrode active layer 12 covered by the non-glue area, and it will usually not be less than the width of the positive electrode active layer 12 covered by the non-glue area, and it will at most exceed the above-mentioned width by 5mm, and the width of the first groove 24 will usually be greater than the width of the first recess 25.

[0072] In this embodiment, a narrower first recess 25 is provided in the negative electrode active layer 22 to improve the wettability of the electrolyte, and a wider first groove 24 is provided in the area in contact with the adhesive tape, and the adhesive tape is buried in the groove, so that the energy density of the battery can be improved.

[0073] See also Fig.12 , further, in this embodiment, the tail end surface of the positive electrode active layer 12 is provided with a plurality of second recesses 14; along the thickness direction of the battery cell, the projections of the plurality of second recesses 14 are all located within the projection of the first part. That is, the area of ​​the positive electrode active layer 12 covered by the termination tape 3 can be provided with a second recess 14. The purpose of setting the second recess 14 is to reduce the lithium ion escape from the covered area of ​​the positive electrode active layer 12, thereby further improving the lithium precipitation at the edge of the tape. The second recess 14 can be one or more of a circle, an ellipse, a square, a rectangle, a triangle, and a diamond, and the groove area of ​​the second recess 14 is located below the positive electrode material covered by the termination tape 3. The second recess 14 is generally a groove, and the plurality of grooves are distributed in an array on the surface of the positive electrode active layer 12. The groove as the second recess 14 can be a through hole, a blind hole or a countersunk hole. The specific structure of the second recess 14 can be set according to the actual situation, and is not specifically limited here.

[0074] In this embodiment, the positive electrode active layer 12 is usually provided with a plurality of the second recesses 14 , which are distributed in an array. The depth of the second recesses 14 is usually smaller than the thickness of the positive electrode active layer 12 .

[0075] Assuming the width of the positive electrode sheet is L1, the width of the groove area is W1, and the length of the groove area is M1, then L1-5mm≤M1≤L1, that is, the difference between the length of the groove area where the second recess 14 is set and the width of the positive electrode sheet is usually not greater than 5mm; W1=0mm~8mm, that is, the width of the groove area is 0mm~8mm. Assuming the spacing size of the second recess 14 is a3, the width of the second recess 14 is b3, and the depth of the second recess 14 is c3, wherein 0<a3≤5mm; 0<b3≤500μm; 0<c3≤50μm.

[0076] The first groove 24 , the first recessed portion 25 and the second recessed portion 14 can be manufactured by laser pore forming process or other manufacturing process, which is not specifically limited here.

[0077] A battery cell provided in this embodiment uses a termination tape 3, and only uses a thin non-adhesive area to cover the positive electrode active layer 12 located on the upper layer of the first step structure, and uses a thicker adhesive area to adhere to the positive electrode collector 11 on the lower layer of the first step structure. Based on the step structure to accommodate the adhesive layer 32 of the sticker, the thickness effect of the tape can be reduced; at the same time, by reducing the contact between the adhesive layer 32 and the positive electrode active layer 12, the adhesive layer 32 is less likely to interact with the electrolyte, resulting in problems such as pore blockage of the tape edge diaphragm, powder shedding at the positive electrode edge, and lithium deposition at the negative electrode.

[0078] Embodiment 2

[0079] According to the structure disclosed in the above embodiment, a comparison group and an experimental group are provided in this embodiment, wherein the comparison group is provided with a conventional pressure-sensitive adhesive tape, and one side surface of the substrate 31 of the pressure-sensitive adhesive tape is completely coated with an adhesive layer 32, while the experimental group is specifically provided with a termination adhesive tape 3 of the above structure.

[0080] In this embodiment, a unified battery cell is used, and the experimental model of the battery cell is 3862A0, which has a central ear structure, a pole piece width L=94mm, a positive electrode active layer 12 is a ternary material, and a negative electrode active layer 22 is graphite; the manufacturing process of the battery cell is: ingredient preparation, coating, rolling, slitting, film making, winding, packaging, liquid injection, formation, secondary sealing, sorting, OCV (Open circuit voltage, open circuit voltage test); in the film making process, the pole piece is pasted with adhesive tape, the orthodox width of the adhesive tape is 20mm, the length is 96mm, the adhesive tape substrate 31 is PET, the thickness of the substrate 31 is 6μm, the adhesive layer 32 is rubber, the thickness of the adhesive layer 32 is 6μm, and the winding core is covered with 5mm of paste.

[0081] Comparative group: using conventional pressure-sensitive adhesive tape, the adhesive area is S1, the substrate 31 area is S, S1 / S=100%. Neither the positive electrode sheet nor the negative electrode sheet has a groove.

[0082] Experimental group 1: using stop tape 3, the adhesive area is S1, the substrate 31 is S, S1 / S=75%.

[0083] Experimental group 2: using the termination tape 3, with the adhesive area S1 and the substrate 31 area S, S1 / S=75%, the negative electrode sheet was laser-punched between the slitting and film-making processes to set the first groove 24 and the first recess 25, the two grooves passed through the top and bottom of the electrode sheet, and there was no contact area with the termination tape 3, the first recess 25 was periodically distributed, the spacing size of the first recess 25 was 1mm, the width of the first recess 25 was 90μm, the depth of the first recess 25 was 15μm, and in the contact area with the termination tape 3, the first groove 24 was 6mm wide and 10μm deep.

[0084] Experimental group 3: using stopper tape 3, the area of ​​the adhesive area is S1, the area of ​​the substrate 31 is S, S1 / S=75%, the positive electrode sheet is laser-formed between the slitting and sheeting processes to set the second recess 14, the second recess 14 is elliptical, and its recess area is located below the positive electrode active layer 12 covered by the stopper tape 3. The width of the recess area is 5 mm, the length is 94 mm, the spacing size of the second recess 14 is 0.5 mm, the width of the second recess 14 is 60 μm, and the depth of the second recess 14 is 10 μm.

[0085] Experimental group 4: using the termination tape 3, with the adhesive area area S1 and the substrate 31 area S, S1 / S=75%, the negative electrode sheet is laser-punched between the slitting and film-making processes to set the first groove 24 and the first recess 25, the two grooves run through the top and bottom of the electrode sheet, and there is no contact area with the termination tape 3, the first recess 25 is periodically distributed, the first recess 25 spacing size is 1mm, the first recess 25 width is 90μm, the first recess 25 depth is 15μm, in the contact area with the termination tape 3, the first groove 24 is 6mm wide, and the first groove 24 is 10μm deep; at the same time, the positive electrode sheet is laser-punched between the slitting and film-making processes to set the second recess 14, the second recess 14 is elliptical, and its groove area is located below the positive electrode active layer 12 covered by the termination tape 3. The groove area has a width of 5 mm and a length of 94 mm. The spacing dimension of the second recesses 14 is 0.5 mm. The width of the second recesses 14 is 60 μm, and the depth of the second recesses 14 is 10 μm.

[0086] Test method: Charge at 1.1C to 4.1V, then switch to 0.5C to fully charge (cut off at 0.05C), let stand for 24 hours, then discharge at 0.5C, cycle 50T, and disassemble. In the table below, energy density = battery capacity × platform voltage / thickness / width / height.

[0087] Table 1 Experimental results

[0088] plan Adhesive tape Lithium deposition at the edge of the adhesive tape Average energy density / Wh / L Comparison group Conventional pressure-sensitive adhesive tape serious 632 Experimental Group 1 Termination tape No lithium precipitate 634 Experimental Group 2 Termination tape No lithium precipitate 641 Experimental Group 3 Termination tape No lithium precipitate 633 Experimental Group 4 Termination tape No lithium precipitate 638

[0089] It can be seen from the above results that lithium deposition is serious at the edge of the adhesive tape in the control group, while lithium deposition does not occur at the edge of the adhesive tape in experimental groups 1, 2, 3, and 4 corresponding to the structures provided in the above embodiments, and the energy density is higher than that of the control group.

[0090] Embodiment 3

[0091] A battery provided in an embodiment of the utility model is introduced below. The battery described below and the battery cell described above can be referred to each other.

[0092] In this embodiment, the battery includes a housing and a battery cell as described in any of the above embodiments, and the battery cell is installed in the housing. The specific structure of the battery cell has been described in detail in the above utility model embodiments, and will not be repeated here. The specific structure of the housing can refer to the prior art, and will not be repeated here.

[0093] Since the battery provided in this embodiment specifically uses the battery cells provided in the above embodiments, the battery has higher energy density and higher reliability.

[0094] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0095] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0096] The above is a detailed introduction to a battery cell and a battery provided by the utility model. This article uses specific examples to illustrate the principle and implementation method of the utility model. The description of the above embodiments is only used to help understand the method and core idea of ​​the utility model. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the utility model, the utility model can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the utility model.

Claims

1. A battery cell, characterized in that: Including termination tape, and stacked and wound positive electrode sheets, separators and negative electrode sheets; The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer, and the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer, wherein the positive electrode active layer is located on the surface of the positive electrode current collector facing the negative electrode sheet, and the negative electrode active layer is located on the surface of the negative electrode current collector facing the positive electrode sheet; The winding tail of the positive electrode sheet has an empty foil area on the surface of one side facing the negative electrode sheet without being coated with active material. Along the winding direction, the termination tape has a first part and a second part, at least part of the first part covers the tail end of the positive electrode active layer, and the second part covers at least part of the empty foil area, wherein the thickness of the first part is less than the thickness of the second part.

2. The battery cell according to claim 1, characterized in that: The first part includes a first substrate layer, and the second part includes a second substrate layer and an adhesive layer which are stacked together. The adhesive layer is located on a side of the second substrate layer away from the negative electrode sheet.

3. The battery cell according to claim 2, characterized in that: The first substrate layer and the second substrate layer are integrally provided.

4. The battery cell according to claim 1, characterized in that: The area of ​​the first part is S1, the area of ​​the second part is S2, and S1 and S2 satisfy: 0.3≤S1 / (S1+S2)≤0.

95.

5. The battery cell according to claim 1, characterized in that: Along the thickness direction of the battery cell, the thickness of the second portion of the termination tape is not greater than the thickness of the positive electrode active layer; and / or along the width direction of the positive electrode sheet, the width of the termination tape is greater than the width of the positive electrode sheet.

6. The battery cell according to claim 1, characterized in that: Along the winding direction, a first groove is provided on the surface of the tail of the negative electrode active layer facing the positive electrode sheet; Along the thickness direction of the battery core, a projection of a head portion of the first portion away from the second portion is located within a projection of the first groove.

7. The battery cell according to claim 6, characterized in that: A second step structure is formed on a side of the first groove facing the head of the negative electrode sheet, and a side wall of the second step structure is arranged along an edge of a side of the first portion away from the second portion.

8. The battery cell according to claim 6, characterized in that: Along the thickness direction of the battery core, the depth of the first groove is not less than the thickness of the first portion.

9. The battery cell according to claim 1, characterized in that: A plurality of first recesses are arranged on the surface of the negative electrode active layer. The first recesses extend along the width direction of the negative electrode sheet, and the plurality of first recesses are arranged at intervals along the length direction of the negative electrode sheet.

10. The battery cell according to claim 1, characterized in that: The tail end surface of the positive electrode active layer is provided with a plurality of second recesses; Along the thickness direction of the battery core, projections of the plurality of second recesses are all located within the projection of the first portion.

11. The battery cell according to claim 10, characterized in that: The second recessed portion is a groove, and a plurality of the grooves are distributed in an array on the surface of the positive electrode active layer.

12. A battery, characterized in that: The invention comprises a housing and a battery cell according to any one of claims 1 to 11, wherein the battery cell is installed in the housing.

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