Roll core and battery

Abstract

The utility model provides a roll core and a battery. The roll core comprises a positive plate, a negative plate and a diaphragm, and the positive plate and the negative plate are wound along the winding direction across the diaphragm. The positive plate comprises a current collector, an active material layer and an adhesive tape, at least one surface of the current collector is provided with a layout area and an empty foil area which are arranged along the length direction of the positive plate, and the empty foil area is closer to the ending end of the positive plate than the layout area. The active material layer is arranged in the laying area and is provided with an ending edge. The ending edge of the active material layer defines a boundary between the routing region and the empty foil region. The tape covers the ending edge, includes a base layer and an adhesive layer, and has a head end and a tail end extending in the winding direction. And the ending end of the negative plate exceeds the head end of the adhesive tape along the winding direction. The surface, facing the current collector, of the base layer is provided with a glue area and a non-glue area, and the glue layer is arranged in the glue area. The adhesive layer at least partially covers the empty foil area, and a small part of the non-adhesive area covers the active material layer. This construction contributes to the reduction of security risks.

Description

Technical Field

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

[0002] The battery generally includes a winding core, which includes a positive electrode sheet and a negative electrode sheet separated by a separator. The positive electrode sheet generally includes a current collector and an active material layer. The active material layer can be provided on one or both surfaces of the current collector.

[0003] The tail edge of the active material layer needs to be taped, for example, to prevent the burrs on the tail edge from piercing the diaphragm, or to ensure that the tail edge of the negative active material layer exceeds the tail edge of the positive active material layer to avoid lithium plating at the negative electrode.

[0004] However, under high temperature and high voltage conditions, the adhesive layer of the tape will interact with the electrolyte, causing the diaphragm pores at the edge of the tape to be blocked, resulting in lithium deposition at the negative electrode, thereby increasing the safety risk of the battery. Utility Model Content

[0005] In view of this, an embodiment of the utility model provides a positive winding core and a battery to reduce safety risks.

[0006] On the one hand, an embodiment of the utility model provides a winding core. The winding core includes a positive electrode sheet, a negative electrode sheet and a separator, and the positive electrode sheet and the negative electrode sheet are wound along the winding direction with the separator between them. The positive electrode sheet includes a current collector, an active material layer and an adhesive tape. At least one surface of the current collector has a layout area and an empty foil area arranged along the length direction of the positive electrode sheet, and the empty foil area is closer to the tail end of the positive electrode sheet than the layout area. The active material layer is arranged in the layout area and has a tail edge. The tail edge of the active material layer defines the boundary between the layout area and the empty foil area. The adhesive tape covers the tail edge, includes a base layer and an adhesive layer, and has a head end and a tail end extending along the winding direction. The tail end of the negative electrode sheet exceeds the head end of the adhesive tape along the winding direction. The surface of the base layer facing the current collector has an adhesive area and a non-adhesive area, and the adhesive layer is arranged in the adhesive area. The adhesive layer at least partially covers the empty foil area, and the non-adhesive area at least partially covers the active material layer.

[0007] In an optional implementation, the glue-free area and the glue-containing area are arranged along the length direction of the positive electrode sheet, and the glue-containing area is closer to the end of the positive electrode sheet than the glue-free area.

[0008] In an optional implementation, the glue layer has a glue layer edge defining a boundary between a glue area and a glue-free area, and the glue layer edge is connected to the tail edge of the active material layer.

[0009] In an optional implementation, the glue layer has a glue layer edge defining a boundary between a glue area and a glue-free area, and the glue layer edge is spaced apart from a trailing edge of the active material layer in the length direction of the positive electrode sheet.

[0010] In an optional implementation, the glue layer has a glue layer edge defining a boundary between a glue area and a glue-free area. The tail edge of the active material layer is closer to the tail end of the positive electrode sheet than the glue layer edge, so that a portion of the glue layer covers the active material layer.

[0011] In an optional implementation, the positive electrode sheet satisfies: S3 / S2=0.2-1; and S4 / S1=0.5-1. Here, S1 is the area of ​​the glue layer, S2 is the area of ​​the glue-free area, S3 is the area of ​​the part of the glue-free area covering the active material layer, and S4 is the area of ​​the part of the glue layer covering the empty foil area.

[0012] In an optional implementation, the positive electrode sheet satisfies: L1 = 5-50 mm; L2 = 2-8 mm; and L2 < L1. Here, L1 is the size of the tape in the length direction of the positive electrode sheet, and L2 is the size of the portion of the tape covering the active material layer in the length direction of the positive electrode sheet.

[0013] In an optional implementation, the positive electrode sheet satisfies: W1≤W2≤W1+8mm. Here, W1 is the size of the current collector in the width direction of the positive electrode sheet, and W2 is the size of the tape in the width direction of the positive electrode sheet.

[0014] In an optional implementation, the active material layer has a first section and a second section arranged along the length direction, the second section is closer to the end of the positive electrode sheet and thinner than the first section, and the tape covers at least part of the second section and does not cover the first section.

[0015] In an optional implementation, the empty foil area is a first empty foil area, and the tape is a first tape. At least one surface of the current collector also has a second empty foil area, and the second empty foil area is closer to the starting end of the positive electrode sheet than the layout area. The active material layer also has a starting edge, and the starting edge of the active material layer defines the boundary between the layout area and the second empty foil area. The positive electrode sheet also includes a pole ear and a second tape, and the pole ear is arranged in the second empty foil area. The second tape covers the starting edge of the active material layer and covers a part of the pole ear. The second tape includes a base layer and a glue layer. The surface of the base layer of the second tape facing the current collector has a glue area and a glue-free area. The glue layer of the second tape is arranged in the glue area of ​​the second tape. Here, at least part of the glue layer of the second tape covers the second empty foil area, and at least part of the glue-free area of ​​the second tape covers the active material layer.

[0016] In an optional implementation, a distance D1 between the tail end of the negative electrode sheet and the head end of the tape satisfies 2 mm ≤ D1 ≤ 6 mm.

[0017] In an optional implementation, the winding core has a pair of curved portions and a flat portion extending between the pair of curved portions. The tail end of the positive electrode sheet exceeds the tail end of the negative electrode sheet and the tail end of the separator along the winding direction. The winding core also includes a fixing tape, which is attached to the tail end of the positive electrode sheet. Along the width direction of the winding core, the distance D2 between the tape and the fixing tape is ≥4 mm.

[0018] In an optional implementation, the core includes a pair of curved portions and a flat portion extending between the pair of curved portions. The pair of curved portions includes a first curved portion and a second curved portion. The first curved portion has a first outer end, and the first outer end is located on a side of the first curved portion that is away from the flat portion in the width direction of the core. The first curved portion is closer to the head end of the tape than the second curved portion in the width direction of the core. The core satisfies: D3≤W3+20mm. Here, D3 is the distance between the head end of the tape and the first outer end in the width direction of the core, and W3 is the size of the first curved portion in the width direction of the core.

[0019] In an optional implementation, the core includes a pair of curved portions and a flat portion extending between the pair of curved portions. The pair of curved portions includes a first curved portion and a second curved portion. The first curved portion has a first outer end, and the first outer end is located on a side of the first curved portion that is away from the flat portion in the width direction of the core. The second curved portion has a second outer end, and the second outer end is located on a side of the second curved portion that is away from the flat portion in the width direction of the core. The first curved portion is closer to the leading end of the first tape than the second curved portion in the width direction of the core. The second tape has a leading end and a trailing end arranged in sequence along the winding direction, and the second curved portion is closer to the trailing end of the second tape than the first curved portion in the width direction of the core. The core satisfies: D3≤W3+20mm; and, D4≤W4+20mm. Here, D3 is the distance between the leading end and the first outer end of the first tape in the width direction of the core, D4 ​​is the distance between the trailing end and the second outer end of the second tape in the width direction of the core, W3 is the size of the first bend in the width direction of the core, and W4 is the size of the second bend in the width direction of the core.

[0020] On the other hand, an embodiment of the present invention provides a battery, which includes the winding core of the above aspect.

[0021] At the trailing edge of the active material layer, the active material layer is at least partially covered by the adhesive-free area of ​​the tape, which helps to avoid or reduce the interaction between the adhesive layer and the electrolyte, and reduces the risk of clogging of the diaphragm at the edge of the tape, thereby reducing the risk of lithium plating at the negative electrode, and further reducing safety risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of a positive electrode sheet according to an embodiment of the utility model.

[0023] Figure 2 For along Figure 1 A schematic cross-sectional view taken along the AA plane in FIG.

[0024] Figure 3 for Figure 1 Schematic diagram of the structure of the tape.

[0025] Figure 4 It is a cross-sectional schematic diagram of a positive electrode sheet according to another embodiment of the utility model.

[0026] Figure 5 It is a cross-sectional schematic diagram of a positive electrode sheet according to another embodiment of the utility model.

[0027] Figure 6 It is a structural schematic diagram of a part of a positive electrode sheet according to another embodiment of the utility model.

[0028] Figure 7 It is a structural schematic diagram of a part of a positive electrode sheet according to another embodiment of the utility model.

[0029] Figure 8 It is a structural schematic diagram of a part of a positive electrode sheet according to another embodiment of the utility model.

[0030] Fig. 9 It is a schematic structural diagram of a positive electrode sheet according to another embodiment of the utility model.

[0031] Fig.10 It is a schematic structural diagram of a positive electrode sheet according to another embodiment of the utility model.

[0032] Fig.11 For along Fig.10 A schematic cross-sectional view taken along the BB plane in FIG.

[0033] Fig.12 Schematic diagram of the structure of a winding core according to an embodiment of the utility model.

[0034] Fig.13 For along Fig.12 Schematic cross-sectional view taken along the CC plane.

[0035] Fig.14 It is a schematic cross-sectional view of a winding core according to another embodiment of the utility model.

[0036] Fig.15 It is a schematic cross-sectional view of a winding core according to another embodiment of the utility model.

[0037] Fig.16 FIG. 1 is a schematic structural diagram of a battery according to an embodiment of the utility model.

[0038] Fig.17FIG. 4 is a schematic structural diagram of a battery according to another embodiment of the utility model. DETAILED DESCRIPTION

[0039] The following is a description of the embodiments of the present invention in conjunction with the accompanying drawings. It should be understood that the present invention can be implemented in a variety of ways and should not be construed as being limited to the embodiments described here. The embodiments described here are only for a more thorough and clear understanding of the present invention.

[0040] <Exemplary positive electrode sheet>

[0041] refer to Figure 1 The present utility model embodiment provides a positive electrode sheet 10. Figures 12 to 15 As shown, the positive electrode sheet 10 and the negative electrode sheet 20 can be wound into a winding core 100 along a winding direction with the separator 30 interposed therebetween. Fig.16 and 17 As shown, the winding core 100 may be packaged into a packaging body 300 to form a battery 200. The winding core 100 and the battery 200 will be described below and will not be described in detail here.

[0042] The following may involve the length direction, thickness direction and width direction of the positive electrode sheet. In the accompanying drawings, the length direction of the positive electrode sheet is indicated by arrow X, the thickness direction is indicated by arrow Z, and the width direction is indicated by arrow Y. It can be understood that the positive electrode sheet has a relative starting end and a tail end in its length direction. In the winding process, the positive electrode sheet is wound from the starting end to the tail end.

[0043] refer to Figure 1 and Figure 2 , the positive electrode sheet 10 may include a current collector 11 and an active material layer 12. The surface 111 of the current collector 11 has a layout area 112 and an empty foil area 113 (i.e., a first empty foil area). The layout area 112 and the empty foil area 113 are arranged along the length direction of the positive electrode sheet 10, and the empty foil area 113 is closer to the end 101 of the positive electrode sheet 10 than the layout area 112. The active material layer 12 is arranged in the layout area 112, while the empty foil area 113 is not provided with an active material layer 12.

[0044] By way of example only, the current collector 11 may be a strip of metal foil, and the active material layer 12 may include a positive electrode active material that can reversibly absorb and release charge carriers. In addition, the active material layer 12 may further include a conductive material, a binder, and various additives.

[0045] By way of example only, the metal foil mentioned here may be aluminum foil, the positive electrode active material mentioned may be lithium transition metal composite oxides such as lithium nickel cobalt manganese composite oxide, the conductive material mentioned may be carbon materials such as acetylene black, and the adhesive mentioned may be polyvinylidene fluoride, etc.

[0046] It is understood that, in this article, the empty foil area refers to the portion on the surface of the current collector where no active material layer is provided. It should be particularly noted that, although the empty foil area is not provided with an active material layer, it does not mean that the metal foil of the current collector is directly exposed in the empty foil area. For example, in some examples, the empty foil area may be at least partially provided with a safety layer. For example, the safety layer may be made of an insulating material.

[0047] Continue to refer Figure 1 and Figure 2 , the active material layer 12 may have a tail edge 121. The tail edge 121 may define a boundary B1 between the layout area 112 and the empty foil area 113. The positive electrode sheet 10 may further include an adhesive tape 13 (first adhesive tape), which may cover the tail edge 121 to prevent the burrs of the tail edge 121 from piercing the separator and lithium plating in the negative electrode.

[0048] refer to Figures 1 to 3 The adhesive tape 13 may include a base layer 131 and an adhesive layer 132. Figures 13 to 15 As shown, the tape 13 has a head end 13a and a tail end 13b extending along the winding direction, and the tail end 201 of the negative electrode sheet 20 exceeds the head end 13a of the tape 13 along the winding direction. The surface 1311 of the base layer 131 facing the current collector 11 may have a glue area 1312 and a glue-free area 1313. The glue layer 132 may be provided in the glue area 1312, while the glue-free area 1313 is not provided with the glue layer 132. Figure 2 , at least part of the adhesive layer 132 covers the empty foil area 113 , and at least part of the adhesive-free area 1313 of the adhesive tape 13 covers the active material layer 12 .

[0049] According to the positive electrode sheet 10 provided in the embodiment of the utility model, at the trailing edge 121 of the active material layer 12, the active material layer 12 is at least partially covered by the glue-free area 1313 of the tape 13, which helps to avoid or reduce the interaction between the glue layer 132 and the electrolyte, and reduces the risk of clogging of the diaphragm at the edge of the tape, thereby reducing the risk of lithium plating at the negative electrode, and further reducing the safety risk.

[0050] It is understood that the positive electrode sheet 10 may further include another active material layer and another tape, the active material layer may be disposed on another surface of the current collector 11 opposite to the surface 111, and the tape may cover the tail edge of the active material layer. The synergistic relationship between the active material layer, the tape and the surface mentioned here may be substantially the same as the synergistic relationship between the active material layer 12, the tape 13 and the surface 111. For the purpose of brevity, this article will not repeat it.

[0051] It can also be understood that, in order to make the drawing clear, Figure 2Only the active material layer 12 disposed on the surface 111 and the adhesive tape 13 matched therewith are shown, and another active material layer disposed on another surface of the current collector 11 and the adhesive tape matched therewith are not shown. Figure 4 , Figure 5 and Fig.11 .

[0052] By way of example only, the material of the base layer 131 may be, but is not limited to, one or more selected from polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) and polyimide (PI).

[0053] By way of example only, the material of the adhesive layer 132 may be, but is not limited to, one or more selected from natural rubber, synthetic rubber, polyacrylate, polypropylene (PP), polyisobutylene (PIB) and styrene-isoprene copolymer.

[0054] Continue to refer Figure 2 and Figure 3 , the glue-free area 1313 and the glue-containing area 1312 can be arranged along the length direction of the positive electrode sheet 10, and the glue-containing area 1312 can be closer to the tail end 101 of the positive electrode sheet 10 than the glue-free area 1313. On the one hand, the tape 13 with such a structure is less difficult to manufacture. On the other hand, according to such a structure of the tape 13, the glue layer 132 can be entirely or mostly attached to the empty foil area 113 of the current collector 11, and the glue-free area 1313 of the base layer 131 can entirely or mostly cover the active material layer 12, which helps to avoid or reduce the contact between the glue layer 132 and the electrolyte on the basis of ensuring relatively firm attachment.

[0055] Continue to refer Figure 2 and Figure 3 The glue layer 132 may have a glue layer edge 1321, and the glue layer edge 1321 defines a boundary B2 between the glue area 1312 and the glue-free area 1313. In one example, Figure 2 As shown, the edge 1321 of the glue layer may be connected to the end edge 131 of the active material layer 12 , that is, the boundary B1 and the boundary B2 may overlap.

[0056] In this way, the glue layer 132 will not cover the active material layer 12. On the one hand, this structure helps to avoid or reduce the impact of the glue layer 132 on the active material layer 12 in the electrolyte environment. On the other hand, according to this structure, the height of the step structure at the edge 130 of the tape 13 is the thickness of the base layer 131, rather than the thickness of both the base layer 131 and the glue layer 132, which helps to reduce the height of the step structure, thereby reducing the risk of negative electrode lithium plating. If the glue layer 132 covers the active material layer 12, the step structure at the edge 130 will have a greater height, which will cause the negative electrode sheet and the positive electrode sheet 10 to form a gap at the step structure, which will in turn cause lithium ion transmission to be blocked and negative electrode lithium plating to occur.

[0057] refer to Figure 4 As an alternative implementation, the glue layer edge 1321 of the glue layer 132 can be spaced from the tail edge 121 of the active material layer 12. That is, in the length direction of the positive electrode sheet 13, the boundary B1 and the boundary B2 can be spaced. According to this structure, the glue layer 132 will not contact the active material layer 12, thereby more effectively avoiding or reducing the impact of the glue layer 132 on the active material layer 12 in the electrolyte environment. In addition, this structure also helps to reduce the height of the step structure at the edge 130, thereby reducing the risk of lithium plating at the negative electrode.

[0058] refer to Figure 5 As another alternative implementation, the tail edge 121 of the active material layer 12 is closer to the tail end 101 of the positive electrode sheet 10 than the glue layer edge 1321 of the glue layer 132, so that the glue layer 132 partially covers the active material layer 12. Since a part of the glue layer 132 is attached to the active material layer 12, the adhesive tape 13 will be more firmly attached. At the same time, since another part of the glue layer 13 is not attached to the active material layer 12, this part of the glue layer will not or less affect the active material layer 12 in the electrolyte environment. Therefore, this implementation can take into account both high adhesion firmness and low safety risks.

[0059] Re-reference Figure 3 The base layer 131 has a thickness T1, and the adhesive layer 132 has a thickness T2. By way of example only, the thickness T1 may range from 4 μm to 50 μm, and the thickness T2 may range from 2 μm to 40 μm.

[0060] Continue to refer Figure 3 , the surface 1311 of the base layer 131 facing the current collector 11 has an area S, and the glue layer 132 (or the glue area 1312) has an area S1. Here, the area S is the sum of the areas of the glue area 1312 and the non-glue area 1313. By way of example only, the ratio S1 / S of the area S1 to the area S can range from 30% to 95%.

[0061] refer to Figure 2 and Figure 3 , the non-glue area 1313 has an area S2, the part of the non-glue area 1313 covering the active material layer 12 has an area S3, and the part of the glue layer 132 covering the empty foil area 113 has an area S4. The ratio S3 / S2 of the area S3 to the area S2 can be in the range of 0.2 to 1 to reduce the influence of the glue layer 132 on the active material layer 121 under the electrolyte environment. The ratio S4 / S1 of the area S4 to the area S1 can be in the range of 0.5 to 1 to ensure that the tape 13 is firmly attached.

[0062] refer to Figure 2 In the length direction of the positive electrode sheet 10, the tape 13 has a size L1, and the portion of the tape 13 covering the active material layer 12 has a size L2. The size L1 may range from 5 mm to 50 mm, and the size L2 may range from 2 mm to 8 mm. In this way, the portion of the active material layer 12 covered by the tape 13 is small, and the capacity loss is small.

[0063] Re-reference Figure 1 In the width direction of the positive electrode sheet 10, the current collector 11 has a size W1, and the tape 13 has a size W2. The size W1 and the size W2 can satisfy W1≤W2≤W1+8mm. In this way, in the width direction of the positive electrode sheet 10, the tape 13 will not be shorter than the current collector 11, nor will it be too long than the current collector 11, so that the tape 13 can completely cover the end edge 121 of the active material layer 12, and there will be no waste of material due to the excessive length of the tape 13.

[0064] It can be understood that the above description of the structure of the adhesive tape 13 is exemplary, and the adhesive tape 13 according to the embodiment of the utility model is not limited to the above structure. Figures 6 to 8 , other possible structures of the adhesive tape 13 are illustrated.

[0065] As a possible implementation, refer to Figure 6 In the length direction of the positive electrode sheet 10 , the two non-glue areas 1313 may be located at opposite sides of the glue area 1312 . Further, the glue area 1312 may extend in a wave shape along the width direction of the positive electrode sheet 10 .

[0066] As another possible implementation, refer to Figure 7 The base layer 131 may have a plurality of adhesive regions 1312 and a plurality of adhesive-free regions 1313. Each adhesive region 1312 is in the shape of a strip extending along the width direction of the positive electrode sheet 10, and each adhesive-free region 1313 is also in the shape of a strip extending along the width direction of the positive electrode sheet 10. The plurality of adhesive regions 1312 and the plurality of adhesive-free regions 1313 may be alternately arranged along the length direction of the positive electrode sheet 10.

[0067] As another possible implementation, refer to Figure 8 , the adhesive area 1312 may be located in the middle of the base layer 131, and the adhesive-free area 1313 may surround the adhesive area 1312. Further, the adhesive area 1312 may be rectangular. Further, the size of the adhesive area 1312 in the width direction of the positive electrode sheet 10 may be greater than its size in the length direction of the positive electrode sheet 10.

[0068] Re-reference Figure 1 and Figure 2 In some embodiments of the present invention, the active material layer 12 may have a first section 122 and a second section 123. The first section 122 and the second section 123 may be arranged along the length direction of the positive electrode sheet 10, and the second section 123 may extend from the first section 122 to the tail edge 121. That is, along the length direction of the positive electrode sheet 10, the second section 123 may be closer to the tail end 101 of the positive electrode sheet 10 than the first section 122. Moreover, the second section 123 may be thinner than the first section 122. The tape 13 may cover at least part of the second section 123 and not cover the first section 122. Since the second section 122 covered by the tape 13 is thinner than the first section 122, the increase in thickness of the positive electrode sheet 10 caused by the tape 13 will be suppressed, which makes the thickness distribution of the positive electrode sheet 10 more uniform, which helps to improve the energy density and reduce the risk of lithium plating at the negative electrode.

[0069] By way of example only, the first segment 122 has a thickness T3, the second segment 123 has a thickness T4, and the difference between the thickness T3 and the thickness T4 may satisfy T3-T4≥4 μm.

[0070] By way of example only, along the length direction of the positive electrode sheet 10, the active material layer 12 has a length L3, the first section 122 has a length L4, and the second section 123 has a length L5, and their relationship can satisfy: L4 / L3=2 / 4, L5 / L3=1 / 4.

[0071] Continue to refer Figure 1 , the positive electrode sheet 10 may further include a tab 14. In the current example, along the length direction of the positive electrode sheet 10, the tab 14 may be located approximately in the middle of the positive electrode sheet 10. That is, in the current example, the positive electrode sheet 10 may have a tab-centered structure. Further, by way of example only, the tab 14 may be an independent component, which may be fixed to the current collector 11 by welding.

[0072] Of course, the positive electrode sheet 10 provided in the embodiment of the utility model is not limited to the structure with the tab placed in the middle.

[0073] refer to Fig. 9In an alternative example, the positive electrode sheet 10 may include a plurality of tabs 14, and the plurality of tabs 14 may be arranged spaced apart from each other along the length direction of the positive electrode sheet 10. In other words, in this example, the positive electrode sheet 10 may have a multi-tab structure. Further, by way of example only, the plurality of tabs 14 may constitute a part of the current collector 11 and may be formed by die cutting.

[0074] refer to Fig.10 In another alternative example, the surface of the current collector 11 may further include an empty foil area 114 (i.e., a second empty foil area), and the empty foil area 114 may be closer to the starting end 102 of the positive electrode sheet 10 than the active material layer 112. The positive electrode sheet 10 may include a tab 14, which may be disposed in the empty foil area 114. That is, in this example, the positive electrode sheet 10 may have a conventional structure in terms of the arrangement of the tab 14. Exemplarily, the tab 14 may be an independent component, which may be fixed to the current collector 11 by welding.

[0075] Further, refer to Fig.10 and Fig.11 , the positive electrode sheet 10 may further include a tape 15 (i.e., a second tape), which may cover the starting edge 124 of the active material layer 12 and a portion of the tab 14. The tape 15 may include a base layer 151 and a glue layer 152. The surface of the base layer 151 facing the current collector 11 may include a glue area 1512 and a glue-free area 1513. The glue layer 152 may be provided in the glue area 1512, while the glue-free area 1513 is not provided with the glue layer 152. At least a portion of the glue layer 152 may cover the empty foil area 114, and at least a portion of the glue-free area 1513 may cover the active material layer 12.

[0076] According to this construction, at the starting edge 124 of the active material layer 12, the active material layer 12 is at least partially covered by the glue-free area 1513 of the base layer 151, which helps to avoid or reduce the interaction between the glue layer 152 and the electrolyte, and reduce the risk of clogging of the diaphragm at the edge of the tape, thereby reducing the risk of lithium plating at the negative electrode, and further reducing safety risks.

[0077] <Exemplary Core>

[0078] The present utility model embodiment also provides a winding core 100, which may include the positive electrode sheet 10 mentioned above. Figures 12 to 16 , the core 100 is illustrated as an example.

[0079] First, refer to Fig.12 and Fig.13In addition to the positive electrode sheet 10, the winding core 100 may also include a negative electrode sheet 20 and a separator 30. The positive electrode sheet 10 and the negative electrode sheet 20 may be wound around the winding center SS and along the winding direction with the separator 30 interposed therebetween to form the winding core 100. Here, with respect to the positive electrode sheet 10, the winding direction may refer to the direction from its starting end 101 to its ending end 102. For ease of understanding, the winding direction is indicated by an arrow Wi in the accompanying drawings.

[0080] By way of example only, the current collector of the negative electrode sheet 20 may be a strip of metal foil, and the active material layer of the negative electrode sheet 20 may include a negative electrode active material capable of reversibly absorbing and releasing charge carriers, a binder, a dispersant, and various additives.

[0081] By way of example only, the metal foil mentioned here may be copper foil, the negative electrode active material mentioned may be carbon materials such as graphite, the binder mentioned may be rubbers such as styrene-butadiene rubber, and the dispersant mentioned may be celluloses such as carboxymethyl cellulose.

[0082] The separator 30 is a member that insulates the positive electrode sheet 10 and the negative electrode sheet 20. By way of example only, the separator 30 may be a porous belt made of a polyolefin resin such as polyethylene or polypropylene. Of course, it is also possible to foresee that the separator 25 may be made of other materials.

[0083] Continue to refer Fig.12 and Fig.13 , the tape 13 has a head end 13a and a tail end 13b. The head end 13a and the tail end 13b of the tape 13 are arranged in sequence along the winding direction. That is to say, the tail end 13b of the tape 13 is closer to the tail end 101 of the positive electrode sheet 10 than its head end 13a. Along the winding direction, the tail end 201 of the negative electrode sheet 20 exceeds the head end 13a of the tape 13, and the two have a spacing D1. The spacing D1 can satisfy 2mm≤D1≤6mm. If D1 is too small, it is difficult to ensure that the tail end 201 of the negative electrode sheet 20 exceeds the tail edge 121 of the active material layer 12 of the positive electrode sheet 10, which will increase the risk of negative electrode lithium plating. If D1 is too large, the energy density will be reduced too much. According to the above-mentioned value range of the spacing D1, the risk of negative electrode lithium plating will be small and the energy density will not be significantly reduced.

[0084] Continue to refer Fig.12 and Fig.13 , the winding core 100 may have a flat structure. Specifically, the winding core 100 may include a first curved portion 110a, a second curved portion 110b, and a flat portion 120. The flat portion 120 may extend between the first curved portion 21a and the second curved portion 110b. When any one of the first curved portion 21a and the second curved portion 110b is referred to indiscriminately, it is referred to as the curved portion 110.

[0085] For the convenience of explanation, the width direction, thickness direction and length direction of the core will be mentioned below. The width direction of the core refers to the direction from one curved part to another curved part, indicated by arrow U; the thickness direction of the core refers to the direction perpendicular to the width direction, indicated by arrow V; the length direction of the core refers to the direction parallel to the winding axis SS, perpendicular to its width direction and thickness direction, indicated by arrow R.

[0086] Still refer to Fig.13 , the core 100 may have a positive electrode tailing structure. That is, along the winding direction, the tail end 101 of the positive electrode sheet 10 exceeds the tail end 201 of the negative electrode sheet 20, and also exceeds the tail end 301 of the diaphragm 30. The core 100 may also include a fixing tape 40, which is attached to the tail end 101 of the positive electrode sheet 10. The spacing D2 between the tape 13 and the fixing tape 40 may satisfy D2 ≥ 4 mm. In this way, in the width direction of the core 100, the tape 13 and the fixing tape 40 will not overlap, which helps to reduce the thickness of the core 100, thereby improving the energy density.

[0087] Continue to refer Fig.13 , the curved portion 110a has an outer end 111a (i.e., a first outer end). The outer end 111a is located on the side of the curved portion 110a away from the flat portion 120 in the width direction. In the width direction of the core 100, the curved portion 110a is closer to the head end 13a of the adhesive tape 13 than the curved portion 110b. In the width direction of the core 100, the outer end 111a of the curved portion 110a and the head end 13a of the adhesive tape 13 have a spacing D3, and the curved portion 110a has a size W3. The spacing D3 may satisfy D3≤W3+20mm.

[0088] If the gap between the distance D3 and the dimension W3 is too large, the tail edge 121 of the active material layer 12 and the tail end 201 of the negative electrode sheet 20 will be away from the curved portion 110a, which will reduce the space utilization of the core 100 in the thickness direction, thereby reducing the energy density. According to the embodiment of the utility model, since the dimension D3 satisfies D3≤W3+20mm, the space of the core 100 in the thickness direction is fully utilized, so the energy density is high.

[0089] Continue to refer Fig.13 In the current example, the winding core 100 may have a structure in which the tabs are placed in the middle. Specifically, the tabs 14 (i.e., the positive tabs) may be located in the middle of the positive electrode sheet 10 in the winding direction. That is, in the current example, the positive electrode sheet 10 may be Figure 1 The positive electrode sheet 10 shown. Correspondingly, the tab 24 (ie, the negative electrode tab) may be located in the middle of the negative electrode sheet 20 in the winding direction.

[0090] It can be understood that the winding core 100 provided in the embodiment of the utility model is not limited to the structure with the tab placed in the middle.

[0091] refer to Fig.14 In an alternative example, the winding core 100 may also have a multi-electrode structure. Specifically, along the winding direction, the positive electrode sheet 10 may have a plurality of spaced-apart pole ears 14. That is, in this example, the positive electrode sheet 10 may be Fig. 9 The positive electrode sheet 10 is shown. Correspondingly, the negative electrode sheet 20 may also have a plurality of tabs 24 arranged at intervals.

[0092] refer to Fig.15 In another alternative example, the winding core 100 may also have a conventional structure. That is, in this example, the positive electrode sheet 10 may be Fig.10 The positive electrode sheet 10 shown in FIG. Fig. 9 As shown, the electrode tab 14 can be disposed in the empty foil area 114. Correspondingly, the negative electrode tab 24 can also be disposed in the empty foil area near the starting end of the negative electrode current collector.

[0093] Furthermore, combined with Fig. 9 and Fig.15 , the curved portion 110b may have an outer end 111b (i.e., a second outer end), and the outer end 111b is located on the side of the curved portion 110b away from the flat portion 120 in the width direction of the core 100. The tape 15 has a leading end 15a and a trailing end 15b arranged in sequence along the winding direction. In the width direction of the core 100, the curved portion 110b is closer to the trailing end 15b of the tape 15 than the curved portion 110a. In the width direction of the core 100, the outer end 111b of the curved portion 110b and the trailing end 15b of the tape 15 have a spacing D4, and the curved portion 110b has a size W4. The spacing D4 may satisfy D4≤W4+20mm.

[0094] If the difference between the spacing D4 and the dimension W4 is too large, the starting edge 124 of the active material layer 12 will be away from the curved portion 110b, which will reduce the space utilization of the core 100 in the thickness direction, thereby reducing the energy density. According to the embodiment of the utility model, since the dimension D4 satisfies D3≤W4+20mm, the space of the core 100 in the thickness direction is fully utilized, so the energy density is high.

[0095] <Exemplary Battery>

[0096] It should be noted that, in this article, "battery" refers to a storage device that can be repeatedly charged and discharged, which can be interpreted as the concept of "secondary battery". In the present utility model, the concept of "secondary battery" can include, but is not limited to, lithium-ion secondary batteries, sodium-ion secondary batteries, and nickel-hydrogen batteries.

[0097] According to an embodiment of the present invention, a battery 200 is Fig.16 Reference Fig.16 The battery 200 may include a winding core 100 and a packaging body 300. The packaging body 300 may be provided with a cavity, and one or more winding cores 100 may be accommodated in the cavity.

[0098] like Fig.16 As shown, the package 300 may be square. That is, the battery 200 may be a square battery. The material of the package 300 may be the same as that used in the past, and there is no particular limitation. For example, the package 300 may be made of metal, in particular, may be made of aluminum (alloy) or iron (alloy).

[0099] According to another embodiment of the present invention, a battery 200 is Fig.17 As shown in Fig.17 As shown, in this embodiment, the packaging body 300 is flat and made of a relatively soft material, such as an aluminum-plastic film. That is, in this embodiment, the battery 200 can be a soft-pack battery.

[0100] It is foreseeable that in other examples of the present invention, the battery 200 may also be implemented as other types besides a square battery and a soft-pack battery.

[0101] It should be noted that other aspects of the structure of the battery 200 may be the same as the conventional battery structure, and for the purpose of brevity, the present invention will not elaborate on this.

[0102] It should be understood that the term "including" and its variations used in the present invention are open inclusions, i.e., "including but not limited to". The term "according to" means "at least in part according to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least another embodiment".

[0103] It should be understood that although the terms "first" or "second" etc. may be used in the present invention to describe various elements, for example, the first tape and the second tape, these elements are not defined by these terms, and these terms are only used to distinguish one element from another.

[0104] The protection scope of the present invention is not limited to the above embodiments. Any changes or substitutions that can be thought of by any person skilled in the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A winding core, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the positive electrode sheet and the negative electrode sheet are wound along a winding direction with the separator interposed therebetween, and the positive electrode sheet comprises: A current collector, wherein at least one surface of the current collector has a layout area and an empty foil area arranged along the length direction of the positive electrode sheet, and the empty foil area is closer to the end of the positive electrode sheet than the layout area; an active material layer, disposed in the layout area and having a tail edge, wherein the tail edge of the active material layer defines a boundary between the layout area and the empty foil area; and The adhesive tape covers the tail edge, comprises a base layer and an adhesive layer, and has a head end and a tail end extending along the winding direction, the tail end of the negative electrode sheet exceeds the head end of the adhesive tape along the winding direction, the surface of the base layer facing the current collector has an adhesive area and an adhesive-free area, the adhesive layer is arranged in the adhesive area, the adhesive layer at least partially covers the empty foil area, and the adhesive-free area at least partially covers the active material layer.

2. The winding core according to claim 1, characterized in that: The non-glue area and the glue area are arranged along the length direction of the positive electrode sheet, and the glue area is closer to the tail end of the positive electrode sheet than the non-glue area.

3. The winding core according to claim 2, characterized in that: The adhesive layer has an adhesive layer edge defining a boundary between the adhesive area and the adhesive-free area, and the adhesive layer edge is connected to a tail edge of the active material layer.

4. The winding core according to claim 2, characterized in that: The glue layer has a glue layer edge defining a boundary between the glue-containing area and the glue-free area, and the glue layer edge is spaced apart from a tail edge of the active material layer in a length direction of the positive electrode sheet.

5. The winding core according to claim 2, characterized in that: The glue layer has a glue layer edge defining a boundary between the glue area and the glue-free area, and the tail edge of the active material layer is closer to the tail end of the positive electrode sheet than the glue layer edge, so that a portion of the glue layer covers the active material layer.

6. The winding core according to claim 1, characterized in that: The positive electrode sheet satisfies: S3 / S2 = 0.2 to 1; and S4 / S1=0.5~1, Among them, S1 is the area of ​​the glue layer, S2 is the area of ​​the glue-free area, S3 is the area of ​​the part of the glue-free area covering the active material layer, and S4 is the area of ​​the part of the glue layer covering the empty foil area.

7. The winding core according to claim 1, characterized in that: The positive electrode sheet satisfies: L1 = 5-50 mm; L2 = 2 to 8 mm; and L2<L1, Wherein, L1 is the dimension of the adhesive tape in the length direction of the positive electrode sheet, and L2 is the dimension of the portion of the adhesive tape covering the active material layer in the length direction of the positive electrode sheet.

8. The winding core according to claim 1, characterized in that: The positive electrode sheet satisfies: W1≤W2≤W1+8mm, Wherein, W1 is the dimension of the current collector in the width direction of the positive electrode sheet, and W2 is the dimension of the tape in the width direction of the positive electrode sheet.

9. The winding core according to claim 1, characterized in that: The active material layer has a first section and a second section arranged along the length direction, the second section is closer to the tail end of the positive electrode sheet than the first section and is thinner than the first section, and the tape covers at least part of the second section and does not cover the first section.

10. The winding core according to claim 1, characterized in that: The empty foil area is a first empty foil area, the adhesive tape is a first adhesive tape, the at least one surface of the current collector further has a second empty foil area, and the second empty foil area is closer to the starting end of the positive electrode sheet than the layout area; The active material layer also has a starting edge, and the starting edge of the active material layer defines the boundary between the layout area and the second empty foil area. The positive electrode sheet also includes a pole ear and a second tape, and the pole ear is arranged in the second empty foil area, and the second tape covers the starting edge of the active material layer and a part of the pole ear. The second tape includes a base layer and an adhesive layer, wherein the surface of the base layer of the second tape facing the current collector has an adhesive area and an adhesive-free area, and the adhesive layer of the second tape is arranged in the adhesive area of ​​the second tape, wherein at least part of the adhesive layer of the second tape covers the second empty foil area, and at least part of the adhesive-free area of ​​the second tape covers the active material layer.

11. The winding core according to any one of claims 1 to 10, characterized in that The distance D1 between the tail end of the negative electrode sheet and the head end of the tape satisfies 2mm≤D1≤6mm.

12. The winding core according to any one of claims 1 to 10, characterized in that The winding core has a pair of curved portions and a flat portion extending between the pair of curved portions, the tail end of the positive electrode sheet exceeds the tail end of the negative electrode sheet and the tail end of the separator along the winding direction, and the winding core also includes a fixing tape, which is adhered to the tail end of the positive electrode sheet, wherein, along the width direction of the winding core, the distance D2 between the tape and the fixing tape is ≥4mm.

13. The winding core according to any one of claims 1 to 10, characterized in that The winding core includes a pair of curved portions and a flat portion extending between the pair of curved portions, the pair of curved portions includes a first curved portion and a second curved portion, the first curved portion has a first outer end, the first outer end is located at a side of the first curved portion away from the flat portion in the width direction of the winding core, and the first curved portion is closer to the head end of the adhesive tape than the second curved portion in the width direction of the winding core; The core meets the following requirements: D3≤W3+20mm, Wherein, D3 is the distance between the head end of the tape and the first outer end in the width direction of the winding core, and W3 is the size of the first curved portion in the width direction of the winding core.

14. The winding core according to claim 10, characterized in that: The invention comprises a pair of curved portions and a flat portion extending between the pair of curved portions, wherein the pair of curved portions comprises a first curved portion and a second curved portion; The first curved portion has a first outer end, the first outer end is located at a side of the first curved portion away from the flat portion in the width direction of the winding core, and the second curved portion has a second outer end, the second outer end is located at a side of the second curved portion away from the flat portion in the width direction of the winding core; The first adhesive tape has a leading end and a trailing end sequentially arranged along a winding direction, and the first curved portion is closer to the leading end of the first adhesive tape than the second curved portion in a width direction of the winding core; The second adhesive tape has a leading end and a trailing end arranged in sequence along the winding direction, and the second curved portion is closer to the trailing end of the second adhesive tape than the first curved portion in the width direction of the winding core; The core meets the following requirements: D3≤W3+20mm; as well as D4≤W4+20mm, Among them, D3 is the distance between the leading end and the first outer end of the first tape in the width direction of the core, D4 ​​is the distance between the trailing end and the second outer end of the second tape in the width direction of the core, W3 is the size of the first curved portion in the width direction of the core, and W4 is the size of the second curved portion in the width direction of the core.

15. A battery, characterized in that: The battery comprises the jellyroll according to any one of claims 1 to 14.

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