Cell and secondary battery

Abstract

The present application relates to the technical field of energy storage, and in particular to a cell and a secondary battery. The cell comprises a first electrode sheet, a second electrode sheet, a separator, and a first insulating member; the polarity of the second electrode sheet is opposite to that of the first electrode sheet; the separator is arranged between the first electrode sheet and the second electrode sheet; and the first electrode sheet, the separator and the second electrode sheet are wound in a winding direction to form an electrode assembly. In the winding direction, the first electrode sheet comprises a first winding start section located on a first layer of the innermost circle of the electrode assembly; and the first winding start section has a first winding start end. The first insulating member is arranged on two surfaces of a part of the first winding start section and extends beyond the first winding start end in a first direction; the portion extending beyond the first winding start end is a first part of the first insulating member; and the first direction is the length direction of the first electrode sheet. The first part can shield burrs of the first electrode sheet at the first winding start end, so as to protect the separator between the first electrode sheet and the second electrode sheet, thereby improving the safety of the cell.

Description

Battery cells and secondary batteries Technical Field

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

[0002] Secondary batteries include a cell and an electrolyte. The cell consists of a second electrode, a first electrode, and a separator. Secondary batteries primarily rely on the movement of metal ions between the second and first electrodes to function. Winding is a key process in the battery manufacturing process because it has a strong integration function, allowing the battery's appearance to take shape. Therefore, the winding process plays a pivotal role in the battery manufacturing process. During the winding process, the electrode is generally cut off with a cutter, and the burrs generated in this process are large, which can easily cause the electrode to pierce the separator at the starting end, causing a short circuit. Summary of the Invention

[0003] In view of this, the present application provides a battery cell and a secondary battery, which can improve the problem of the electrode puncturing the diaphragm at the starting end.

[0004] In a first aspect, an embodiment of the present application provides a battery cell comprising a first pole piece, a second pole piece, a diaphragm, and a first insulating member, wherein the polarity of the second pole piece is opposite to that of the first pole piece, and the diaphragm is disposed between the first pole piece and the second pole piece, and the first pole piece, the diaphragm, and the second pole piece are wound along a winding direction to form an electrode assembly. Along the winding direction, the first pole piece includes a first winding start section located at the first layer of the innermost circle of the electrode assembly, and the first winding start section has a first winding start end. The first insulating member is disposed on both sides of a portion of the first winding start section and extends beyond the first winding start end along the first direction. The portion extending beyond the first winding start end is the first portion of the first insulating member, and the first direction is the length direction of the first pole piece.

[0005] In the above-mentioned battery cell, the first electrode sheet, the second electrode sheet and the diaphragm are wound along the winding direction to form an electrode assembly, wherein the first layer of the first electrode sheet at the innermost circle of the electrode assembly is the first winding starting section. Before the winding process, the first electrode sheet is usually cut off by a cutter. During this process, burrs are easily generated at the end of the first electrode sheet. Such burrs can easily cause the first electrode sheet to pierce the diaphragm at the first winding starting end, causing a short circuit in the battery cell. By arranging a first insulating member on both sides of a portion of the first winding starting section, and along the length direction of the first electrode sheet, the first winding starting section has a first winding starting end, the first insulating member extends beyond the first winding starting end, and the extending portion is the first portion of the first insulating member. The first portion can block the burrs of the first electrode sheet at the first winding starting end to protect the diaphragm between the first electrode sheet and the second electrode sheet, thereby improving the problem of the electrode sheet piercing the diaphragm at the starting end and improving the safety of the battery cell.

[0006] In one or more of the above embodiments, the first winding starting section is provided with a cutout, and the first insulating members at least partially cover the cutout and are bonded to each other at the cutout.

[0007] In the aforementioned battery cell, the cutout provided at the first winding start section helps to mark the first winding start section of the first electrode piece during the winding process, facilitating attachment of the first insulating member to the first winding start section and facilitating winding from the first winding start section provided with the cutout. Furthermore, the first insulating members provided on both sides of the first winding start section, after covering the cutout, can adhere to each other at the cutout, thereby improving the bonding strength between the two first insulating members.

[0008] In one or more of the above embodiments, the length of the first portion is C mm, 30≥C≥1.5.

[0009] In the aforementioned battery cell, the length of the first portion is greater than or equal to 1.5 mm, thereby improving the bonding strength between the first insulating member and the first electrode piece and enhancing bonding firmness. Furthermore, the length of the first portion is less than or equal to 30 mm, thereby reducing the length of the first insulating member while maintaining sufficient bonding strength, thereby reducing the risk of bending of the first portion and improving the safety of the battery cell without compromising the energy density of the battery cell.

[0010] In one or more of the above embodiments, along the winding direction, the second pole piece includes a second winding starting segment located in the first layer of the innermost circle of the electrode assembly, the length of the second winding starting segment is B mm, the length of the first winding starting segment is A mm, the length of the first part is C mm, and 5≥BA≥C.

[0011] In the above-mentioned battery cell, along the winding direction, the length of the second winding starting section is greater than the length of the first winding starting section, and the length of the second winding starting section exceeding the first winding starting section is greater than or equal to the length of the first part of the first insulating member and does not exceed 5 mm, so that after the first pole piece, the diaphragm and the second pole piece are wound along the winding direction to form an electrode assembly, the hollow area of ​​the second pole piece in the thickness direction of the battery cell is reduced, thereby reducing the lithium plating problem at the starting end of the second pole piece.

[0012] In one or more of the above embodiments, along the winding direction, the length of the first winding starting section is A mm, the length of the first portion is C mm, the width of the electrode assembly is W mm, and C+A≤W.

[0013] In the above-mentioned battery cell, along the winding direction, the sum of the length of the first winding starting section and the length of the first part is less than or equal to the width of the electrode assembly, so as to improve the situation where the first insulating part is folded due to excessive length in the innermost layer of the electrode assembly. The first insulating part remains in a single-layer structure, thereby reducing the impact of the first insulating part on the overall thickness of the electrode assembly.

[0014] In one or more of the above embodiments, the first insulating member further includes a second portion, which is the portion of the first insulating member bonded to the first winding starting section. The length of the second portion is D mm, the length of the first portion is C mm, and 10C≥D≥3C.

[0015] In the above-mentioned battery cell, the length of the portion of the first insulating member bonded to the first winding starting section is greater than or equal to 3 times the length of the portion of the first insulating member extending out of the first winding starting section along the winding direction, and less than or equal to 10 times the length of the portion of the first insulating member extending out of the first winding starting section along the winding direction, so as to improve the bonding stability between the first insulating member and the first winding starting section.

[0016] In one or more of the above embodiments, the first pole piece includes a first current collector and an active material layer arranged on both sides of the first current collector. Along the thickness direction of the first winding starting section, the thickness of the first insulating member is Eμm, the thickness of the first current collector is Fμm, and the thickness of the diaphragm is Gμm, and E+G≥3F.

[0017] Before winding the above-mentioned battery cell, the first electrode sheet usually needs to be pre-cut with a cutter. During the cutting process, burrs will be generated on the cut edge of the first current collector. The size of this burr is usually 2 to 3 times the thickness of the first current collector. By setting the sum of the thickness of the first insulating member and the diaphragm to 3 times the thickness of the first current collector, the burrs on the edge of the first current collector can be effectively blocked by the first insulating member and the diaphragm, thereby improving the problem of positive and negative electrode contact short circuit caused by the burrs on the edge of the first current collector piercing the diaphragm, thereby improving the safety of the battery cell.

[0018] In one or more of the above embodiments, 20≤E≤60.

[0019] In the above-mentioned battery cell, the thickness of the first insulating member is set to be greater than 20μm and less than 60μm, so that when the first insulating member is attached to the first winding starting section, the influence of the thickness of the first insulating member on the thickness of the innermost layer of the electrode assembly winding is reduced.

[0020] In one or more of the above embodiments, the first insulating member further includes a third portion, which is the portion of the first insulating member extending beyond the first winding starting end along the third direction, the third direction being the width direction of the first pole piece, and the length of the third portion along the third direction is K mm, K≤2.

[0021] In the above-mentioned battery cell, the length of the portion of the first insulating member that exceeds the starting end of the first winding along the width direction of the first pole piece is less than or equal to 3 mm, so that along the width direction of the first pole piece, the first insulating member can block the end of the first pole piece in the width direction to protect the diaphragm between the first pole piece and the second pole piece, thereby improving the problem of the pole piece puncturing the diaphragm at the starting end and improving the safety of the battery cell.

[0022] In one or more of the above embodiments, the first insulating member includes a first adhesive layer and an isolation layer. The first adhesive layer is arranged on a side of the isolation layer close to the first winding starting section, and the first insulating member is bonded and fixed to the first winding starting section through the first adhesive layer.

[0023] In the above-mentioned battery cell, the first insulating member is bonded and fixed to the first winding starting section through the first adhesive layer. The first adhesive layer plays a connecting role, while the isolation layer plays a protective role. The isolation layer is used to contact the burrs on the cut edge of the first current collector to isolate the first pole piece and the diaphragm. The first adhesive layer fixes the isolation layer through adhesive force.

[0024] In one or more of the above embodiments, the first insulating member includes a first adhesive layer, an isolation layer and a second adhesive layer, the second adhesive layer is arranged on the side of the isolation layer away from the first winding starting section, and the first insulating member is bonded and fixed to the diaphragm through the second adhesive layer.

[0025] In the above-mentioned battery cell, the second adhesive layer is arranged on the side of the isolation layer away from the first winding starting section, so that both sides of the first insulating member are sticky, and the first insulating member is bonded and fixed to the diaphragm through the second adhesive layer, so that the position of the first insulating member is fixed.

[0026] In one or more of the above embodiments, the first insulating member is hot melt adhesive.

[0027] In the above-mentioned battery cell, the hot melt adhesive is a plastic adhesive whose physical state changes with temperature within a certain temperature range, while its chemical properties remain unchanged, and the fixing relationship between the first insulating member and the first pole piece will be more firmly secured.

[0028] In one or more of the above embodiments, the first winding start section has no empty foil area.

[0029] In the above-mentioned battery cell, there is no empty foil area in the starting section of the first winding, so that in the innermost layer of the electrode assembly, the starting section of the first winding has sufficient reaction area. At the same time, the absence of the empty foil area in the starting section of the first winding can make the first insulating member have a flat adhesive surface, thereby improving the adhesive stability of the first insulating member.

[0030] In one or more of the above embodiments, the battery cell also includes a second insulating member. Along the winding direction, the first pole piece also includes a first winding tail section located at the end of the outermost circle of the electrode assembly. The second insulating member is pasted on both sides of the first winding tail section. The first winding tail section has a first winding tail end, and the second insulating member extends beyond the first winding tail end along the first direction.

[0031] In the above-mentioned battery cell, the first pole piece, the second pole piece and the diaphragm are wound along the winding direction to form an electrode assembly, wherein the first pole piece at the outermost end of the electrode assembly is the first winding tail section. Before the winding process, the first pole piece is usually cut off by a cutter. During this process, burrs are easily generated at the end of the first pole piece. Such burrs can easily cause the first pole piece to pierce the diaphragm at the first winding tail end, causing a short circuit in the battery cell. By arranging a second insulating member on both sides of the first winding tail section, and along the length direction of the first pole piece, the first winding tail section has a first winding tail end, and the second insulating member exceeds the first winding tail end, the second insulating member can block the burrs of the first pole piece at the first winding tail end to protect the diaphragm between the first pole piece and the second pole piece, thereby improving the problem of the pole piece piercing the diaphragm at the tail end and improving the safety of the battery cell.

[0032] In one or more of the above embodiments, the second insulating member includes a tail portion, which is a portion of the second insulating member that extends beyond the first winding tail end along the first direction, and the length of the tail portion along the first direction is P mm; along the winding direction, the second pole piece includes a second winding tail segment, the length of the second winding tail segment is N mm, the length of the first winding tail segment is M mm, and NM≥P.

[0033] In the above-mentioned battery cell, along the winding direction, the length of the second winding tail section is greater than the length of the first winding tail section, and the length of the second winding tail section exceeding the first winding tail section is greater than or equal to the length of the tail portion of the second insulating member, so that after the first electrode, the diaphragm and the second electrode are wound along the winding direction to form an electrode assembly, the ion embedding space of the second electrode is increased, the lithium plating problem of the second electrode is improved, and the capacity and charge and discharge performance of the battery cell are improved.

[0034] In one or more of the above embodiments, the isolation layer includes a layer formed by at least one of the following:

[0035] Polyolefins, polyolefin nitriles, polyol esters, polyamides, polyurethanes, polyethylene terephthalate, and composites containing at least one of polyolefins, polyolefin nitriles, polyol esters, polyamides, polyurethanes, and polyethylene terephthalate;

[0036] The first adhesive layer and / or the second adhesive layer includes a layer formed of at least one of the following:

[0037] Polyolefins, polyurethanes, polyacrylates, silicones, rubbers, and composites containing at least one of polyolefins, polyurethanes, polyacrylates, silicones, and rubbers.

[0038] In the above-mentioned battery cell, the isolation layer includes a layer formed by at least one of the following: polyolefin, polyolefin nitrile, polyol ester, polyamide, polyurethane, polyethylene terephthalate, and a composite containing at least one of polyolefin, polyolefin nitrile, polyol ester, polyamide, polyurethane, and polyethylene terephthalate. These materials are polymer materials with good mechanical properties and electrical insulation properties, and high chemical stability. The first adhesive layer and / or the second adhesive layer include a layer formed by at least one of the following: polyolefin, polyurethane, polyacrylate, silicone, rubber, and a composite containing at least one of polyolefin, polyurethane, polyacrylate, silicone, and rubber. These substances used as the materials of the first adhesive layer and / or the second adhesive layer have good permeability and high bonding strength after polymerization.

[0039] In a second aspect, an embodiment of the present application provides a secondary battery, comprising the battery cell in any of the above embodiments.

[0040] By adopting the above-mentioned battery cell, the above-mentioned secondary battery can improve the problem of the electrode of the battery cell puncturing the diaphragm at the starting end, thereby improving the safety of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG1 is a schematic diagram of the overall structure of a secondary battery in an embodiment of the present application.

[0042] FIG2 is a schematic diagram of the disassembled structure of a secondary battery in an embodiment of the present application.

[0043] FIG3 is a schematic diagram of a wound cross-sectional structure of a battery cell in an embodiment of the present application, which shows a schematic diagram of the structure cut along “III-III” in FIG2 .

[0044] FIG4 is a schematic diagram of the fixing relationship between the first winding starting section and the first insulating member in an embodiment of the present application.

[0045] FIG5 is a schematic top view of the fixed relationship between the first winding starting section and the first insulating member in an embodiment of the present application.

[0046] FIG6 is a schematic diagram of the layer structure of the first insulating member in an embodiment of the present application.

[0047] FIG7 is a schematic diagram of the fixed relationship between the first winding tail section and the second insulating member in an embodiment of the present application.

[0048] Description of Main Component Symbols 100 Secondary battery 200 Battery cell 210 First pole piece 211 First winding starting section 2111 First winding starting end 2112 Notch 212 First current collector 213 Active material layer 214 First winding ending section 2141 First winding ending end 220 Second pole piece 221 Second winding starting section 230 Separator 240 First insulating member 241 First portion 242 Second portion 243 Third portion 244 First adhesive layer 245 Isolation layer 246 Second adhesive layer 250Second insulating member 251 Tail portion R Winding direction X First direction Y Second direction Z Third direction 300 Tab 400 Housing

[0049] The following specific implementation methods will further illustrate this application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0051] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a centrally located element at the same time. When an element is considered to be "disposed on" another element, it can be directly disposed on the other element or there may be a centrally located element at the same time. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances. The term "and / or" as used herein includes any and all combinations of one or more related listed items.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "include" and "include" and any variations thereof in the specification and claims of this application and the accompanying drawings are intended to cover non-exclusive inclusions.

[0053] In the description of the embodiments of this application, the technical terms "first," "second," etc. are used only to distinguish different objects and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise specifically defined.

[0054] The term "perpendicular" is used to describe an ideal position between two components. In actual production or use, two components may be approximately perpendicular to each other. For example, in numerical terms, perpendicularity can refer to the angle between two lines being within 90°±10°, the dihedral angle between two planes being within 90°±10°, or the angle between a line and a plane being within 90°±10°.

[0055] It should be noted that when a parameter is greater than, equal to, or less than a certain endpoint value, it should be understood that the endpoint value is allowed to have a tolerance of ±10%. For example, if the ratio of A to B is greater than 10, it should be understood to include the case where the ratio of A to B is greater than 9, and also include the case where the ratio of A to B is greater than 11.

[0056] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The appearance of such phrases in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. The various embodiments of the present application may be combined with each other unless there is a conflict.

[0057] It should be noted that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary and should not constitute any limitation to the present application.

[0058] An embodiment of the present application provides a battery cell comprising a first pole piece, a second pole piece, a diaphragm, and a first insulating member. The polarity of the second pole piece is opposite to that of the first pole piece. The diaphragm is disposed between the first pole piece and the second pole piece. The first pole piece, the diaphragm, and the second pole piece are wound along a winding direction to form an electrode assembly. Along the winding direction, the first pole piece includes a first winding start section located in the first layer of the innermost circle of the electrode assembly. The first winding start section has a first winding start end. The first insulating member is disposed on both sides of a portion of the first winding start section and extends beyond the first winding start end along a first direction. The portion extending beyond the first winding start end is the first portion of the first insulating member. The first direction is the length direction of the first pole piece.

[0059] In the above-mentioned battery cell, the first electrode sheet, the second electrode sheet and the diaphragm are wound along the winding direction to form an electrode assembly, wherein the first layer of the first electrode sheet at the innermost circle of the electrode assembly is the first winding starting section. Before the winding process, the first electrode sheet is usually cut off by a cutter. During this process, burrs are easily generated at the end of the first electrode sheet. Such burrs can easily cause the first electrode sheet to pierce the diaphragm at the first winding starting end, causing a short circuit in the battery cell. By arranging a first insulating member on both sides of a portion of the first winding starting section, and along the length direction of the first electrode sheet, the first winding starting section has a first winding starting end, the first insulating member extends beyond the first winding starting end, and the extending portion is the first portion of the first insulating member. The first portion can block the burrs of the first electrode sheet at the first winding starting end to protect the diaphragm between the first electrode sheet and the second electrode sheet, thereby improving the problem of the electrode sheet piercing the diaphragm at the starting end and improving the safety of the battery cell.

[0060] Some implementation methods of the present application are described in detail below with reference to the accompanying drawings.

[0061] Referring to Figures 1 and 2 , one embodiment of the present application provides a secondary battery 100 comprising a battery cell 200, a tab 300, and a housing 400. The battery cell 200 is a wound structure, with the battery cell 200 and tab 300 housed in the housing 400. The tab 300 is electrically connected to the battery cell 200 and partially extends out of the housing 400. A first direction X is defined as the width of the secondary battery 100 and the battery cell 200; a second direction Y is defined as the thickness of the secondary battery 100 and the battery cell 200; and a third direction Z is defined as the length of the secondary battery 100 and the battery cell 200. The first direction X, the second direction Y, and the third direction Z are perpendicular to each other.

[0062] In some embodiments, the housing 400 may be an aluminum-plastic film.

[0063] In some embodiments, an electrolyte is injected into the housing 400. The electrolyte comprises a solvent, a lithium salt, and additives. The solvent may be a cyclic carbonate (PC, EC), a chain carbonate (DEC, DMC, EMC), a carboxylate (MF, MA, EA, MP), other organic solvents, or a combination thereof. The lithium salt may be LiPF6, LiBF4, LiClO4, LiB(C6H), LiCH3SO3, LiCF3SO3LiN(SO2CF3)2, LiC(SO2CF3)3, LiBOB, etc.

[0064] It should be noted that after winding, the battery cell 200 is typically subjected to a heat pressing process to tighten the wound structure and form it into a compact shape. The battery cell 200 is then placed into the housing 400 and filled with electrolyte. The electrolyte is omitted in Figure 2 for clarity.

[0065] In related technical means, before the winding process, the first pole piece 210 is usually cut off by a cutter. During this process, burrs are easily generated at the end of the first pole piece 210. These burrs can easily cause the first pole piece 210 to pierce the diaphragm 230 at the first winding starting end 2111, causing the battery cell 200 to short-circuit.

[0066] Please refer to Figure 3. An embodiment of the present application provides a battery cell 200, including a first electrode piece 210, a second electrode piece 220, a diaphragm 230 and a first insulating member 240. The polarity of the second electrode piece 220 is opposite to that of the first electrode piece 210. The diaphragm 230 is arranged between the first electrode piece 210 and the second electrode piece 220. The first electrode piece 210, the diaphragm 230 and the second electrode piece 220 are wound along a winding direction R to form an electrode assembly.

[0067] In some embodiments, the first electrode 210 is a positive electrode, and the second electrode 220 is a negative electrode.

[0068] In some embodiments, along the winding direction R, the first electrode sheet 210 includes a first winding start segment 211 located at the first layer of the innermost circle of the electrode assembly, and the first winding start segment 211 has a first winding start end 2111 .

[0069] It is worth noting that the first pole piece 210 has straight sections and curved sections during the winding process. The straight sections extend in a direction substantially parallel to the first direction X. Multiple straight sections are stacked along the second direction Y, while the curved sections connect the two preceding and succeeding straight sections along the winding direction R. The first winding starting section 211 is the portion of the first pole piece 210 in the first layer of the innermost circle of the electrode assembly, i.e., the portion of the innermost straight section. The innermost circle of the first pole piece 210 in the electrode assembly refers to the circle of the first pole piece 210 closest to the central axis of the winding of the electrode assembly.

[0070] Referring to Figures 3 and 4 , in some embodiments, the first electrode sheet 210 includes a first current collector 212 and active material layers 213 disposed on both sides of the first current collector 212. Along the thickness direction of the first winding starting section 211, the thickness of the first insulating member 240 is E μm, the thickness of the first current collector 212 is F μm, and the thickness of the separator 230 is G μm, where E + G ≥ 3 F. During the cutting process, burrs are generated on the cut edges of the first current collector 212. These burrs are typically 2 to 3 times the thickness of the first current collector 212. By setting the combined thickness of the first insulating member 240 and the separator 230 to 3 times the thickness of the first current collector 212, the burrs on the edges of the first current collector 212 are effectively blocked by the first insulating member 240 and the separator 230. This mitigates the problem of positive-negative electrode short circuits caused by burrs piercing the separator 230, thereby improving the safety of the battery cell 200.

[0071] In some embodiments, 20 ≤ E ≤ 60. By setting the thickness of the first insulating member 240 to be greater than 20 μm and less than 60 μm, when the first insulating member 240 is attached to the first winding start section 211, the effect of the thickness of the first insulating member 240 on the thickness of the innermost layer of the electrode assembly winding is reduced, wherein the thickness of the innermost layer of the electrode assembly winding refers to the total thickness of the first electrode sheet 210 and the first insulating member 240.

[0072] The first insulating member 240 is disposed on both sides of a portion of the first winding starting section 211 and extends beyond the first winding starting end 2111 along the first direction X. The portion extending beyond the first winding starting end 2111 is the first portion 241 of the first insulating member 240. The first direction X represents the length of the first electrode piece 210 and also the width of the battery cell 200. By disposing the first insulating member 240 on both sides of the first winding starting section 211, with the first portion 241 extending beyond the first winding starting end 2111 along the first direction X, burrs on the first electrode piece 210 at the first winding starting end 2111 are shielded, thereby protecting the diaphragm 230 between the first electrode piece 210 and the second electrode piece 220. This mitigates the risk of the electrode piece puncturing the diaphragm 230 at the starting end and improves the safety of the battery cell 200.

[0073] In some embodiments, along the winding direction R, the length of the first winding starting section 211 is A mm, the width of the electrode assembly is W mm, C+A≤W, and the sum of the length of the first winding starting section 211 and the length of the first part 241 is less than or equal to the width of the electrode assembly, so as to improve the situation where the first insulating member 240 is folded due to excessive length in the innermost layer of the electrode assembly, and the first insulating member 240 remains in a single-layer structure, thereby reducing the influence of the first insulating member 240 on the overall thickness of the electrode assembly.

[0074] In some embodiments, the length of the first portion 241 is C mm, where 30 ≥ C ≥ 1.5. The length of the first portion 241 is greater than or equal to 1.5 mm, thereby improving the bonding strength and adhesiveness between the first insulating member 240 and the first pole piece 210. Furthermore, the length of the first portion 241 is less than or equal to 30 mm. This reduces the length of the first insulating member 240 while maintaining sufficient bonding strength, alleviates the problem of bending of the first portion 241, and improves the safety of the battery cell 200 without affecting the energy density of the battery cell 200.

[0075] Referring to Figures 4 and 5 , in some embodiments, the first insulating member 240 further includes a second portion 242 bonded to the first winding start section 211. Specifically, the second portion 242 is the portion of the first insulating member 240 bonded to the first winding start section 211. The length of the second portion 242 is D mm, with 10C ≥ D ≥ 3C. The length of the second portion 242 is greater than or equal to three times the length of the portion of the first insulating member 240 extending from the first winding start section 211 along the winding direction R, and less than or equal to ten times the length of the portion of the first insulating member 240 extending from the first winding start section 211 along the winding direction R, thereby improving the bonding stability between the first insulating member 240 and the first winding start section 211.

[0076] Please refer to Figure 5. In some embodiments, the first insulating member 240 also includes a third portion 243 that extends beyond the first winding starting end 2111 along the third direction Z, that is, the third portion 243 is the portion of the first insulating member 240 that extends beyond the first winding starting end 2111 along the third direction Z. The third direction Z is the width direction of the first pole piece 210 and also the length direction of the battery cell 200. The length of the third portion 243 along the third direction Z is Kmm, K≤2, so that the first insulating member 240 can block the end of the first pole piece 210 in the width direction along the width direction of the first pole piece 210 to protect the diaphragm 230 between the first pole piece 210 and the second pole piece 220, thereby improving the problem of the pole piece puncturing the diaphragm 230 at the starting end and improving the safety of the battery cell 200.

[0077] It is worth noting that the length of the above-mentioned third part 243 along the third direction Z refers to the length of the first insulating part 240 along the third direction Z that exceeds the single side of the first winding starting end 2111, that is, the first insulating part 240 may include two third parts 243, each first part 241 exceeds one side of the first winding starting end 2111 along the third direction Z, and the length of the third part 243 on each side is less than or equal to 2 mm; the first insulating part 240 may also include a third part 243, and a third part 243 exceeds either side of the first winding starting end 2111 along the third direction Z.

[0078] Please refer to Figures 3, 4 and 6. In some embodiments, the first insulating member 240 includes a first adhesive layer 244 and an isolation layer 245. The first adhesive layer 244 is arranged on the side of the isolation layer 245 close to the first winding starting section 211. The first insulating member 240 is bonded and fixed to the first winding starting section 211 through the first adhesive layer 244. The first adhesive layer 244 plays a connecting role, while the isolation layer 245 plays a protective role. The isolation layer 245 is used to contact the burrs on the cut edge of the first current collector 212 to isolate the first pole piece 210 and the diaphragm 230. The first adhesive layer 244 fixes the isolation layer 245 through adhesion.

[0079] In some embodiments, the first insulating member 240 further includes a second adhesive layer 246. The second adhesive layer 246 is disposed on a side of the isolation layer 245 away from the first winding starting section 211. The first insulating member 240 is bonded and fixed to the diaphragm 230 via the second adhesive layer 246. Both surfaces of the first insulating member 240 are adhesive to enhance the positional stability of the first insulating member 240.

[0080] In some embodiments, the first insulating member 240 is hot melt adhesive. Hot melt adhesive is a plastic adhesive whose physical state changes with temperature within a certain temperature range, while its chemical properties remain unchanged. This provides a more secure connection between the first insulating member 240 and the first electrode 210, thereby alleviating the problem of the first insulating member 240 shifting within the battery cell 200. Because hot melt adhesive is a solid, it facilitates packaging, transportation, and storage. Hot melt adhesive is solid at room temperature, but when heated and melted to a certain temperature, it becomes a fluid, viscous liquid with a high adhesive strength, thus facilitating attachment of the first insulating adhesive to the first winding start section 211.

[0081] In some embodiments, the first winding starting section 211 is provided with a notch 2112. The notch 2112 can help mark the first winding starting section 211 of the first pole piece 210 during the winding process, so as to facilitate the attachment of the first insulating member 240 at the first winding starting section and facilitate the start of winding from the first winding starting section 211 provided with the notch 2112. The notch 2112 is located on the first winding starting end 2111 arranged along the first direction X. The first insulating member 240 at least partially covers the notch 2112 and is bonded to each other at the notch 2112. That is, in the first insulating member 240 attached to both sides of the first winding starting section 211, the two first portions 241 are bonded to each other, the two third portions 243 are bonded to each other, and the two second portions 242 are bonded to each other through the notch 2112, thereby improving the bonding strength between the two first insulating members 240.

[0082] In some embodiments, the first winding starting section 211 has no empty foil area, so that in the innermost layer of the electrode assembly, the first winding starting section 211 has a sufficient reaction area. At the same time, the first winding starting section 211 has no empty foil area, which can enable the first insulating member 240 to have a flat adhesive surface, thereby improving the adhesive stability of the first insulating member 240.

[0083] Referring to Figures 3 and 7 , in some embodiments, the battery cell 200 further includes a second insulating member 250. The first electrode sheet 210 further includes a first winding end segment 214 located at the outermost end of the electrode assembly along the winding direction R. The outermost end of the first electrode sheet 210 in the electrode assembly refers to the first electrode sheet 210 that is farthest from the central axis of the winding of the electrode assembly.

[0084] The second insulating member 250 is adhered to both sides of the first winding end section 214. The first winding end section 214 has a first winding end end 2141. The second insulating member 250 extends beyond the first winding end end 2141 along the first direction X. Since the first winding end end 2141 will leave burrs after being cut by a cutter, the burrs can easily cause the first electrode piece 210 to pierce the diaphragm 230 at the first winding end end 2141, thereby causing electrical conduction between the first electrode piece 210 and the second electrode piece 220, resulting in a short circuit in the battery cell 200. By arranging the second insulating member 250 on both sides of the first winding tail section 214, and along the length direction of the first pole piece 210, the first winding tail section 214 has a first winding tail end 2141, and the second insulating member 250 exceeds the first winding tail end 2141. The second insulating member 250 can block the burrs of the first pole piece 210 at the first winding tail end 2141 to protect the diaphragm 230 between the first pole piece 210 and the second pole piece 220, thereby improving the problem of the pole piece puncturing the diaphragm 230 at the tail end and improving the safety of the battery cell 200.

[0085] In some embodiments, the second insulating member 250 includes a tail portion 251, which is a portion of the second insulating member 250 that extends beyond the first winding tail end 2141 along the first direction X. The tail portion 251 has a length of P mm along the first direction X. Along the winding direction R, the second electrode piece 220 includes a second winding tail segment, the length of the second winding tail segment is N mm, the length of the first winding tail segment 214 is M mm, NM ≥ P, the length of the second winding tail segment is greater than the length of the first winding tail segment 214, and the length of the second winding tail segment that extends beyond the first winding tail segment 214 is greater than or equal to the length of the tail portion 251 of the second insulating member 250. This allows the first electrode piece 210, the separator 230, and the second electrode piece 220 to be wound along the winding direction R to form an electrode assembly, thereby increasing the ion embedding space in the second electrode piece 220, improving the lithium plating problem in the second electrode piece 220, and improving the capacity and charge-discharge performance of the battery cell 200. It can be understood that the ion intercalation space is an intercalation space for lithium ions.

[0086] Referring to FIG. 3 , in some embodiments, along the winding direction R, the second electrode sheet 220 includes a second winding start segment 221 located in the first innermost layer of the electrode assembly. The length of the second winding start segment 221 is B, the length of the first winding start segment 211 is A mm, and the length of the first portion 241 is C mm, where 5 mm ≥ B ≥ C. The length of the second winding start segment 221 is greater than the length of the first winding start segment 211. The length of the second winding start segment 221 beyond the first winding start segment 211 is greater than or equal to the length of the first portion 241 of the first insulating member 240 and does not exceed 5 mm. This allows, after the first electrode sheet 210, separator 230, and second electrode sheet 220 are wound along the winding direction R to form the electrode assembly, to reduce the hollow area of ​​the second electrode sheet 220 in the thickness direction of the battery cell 200, thereby alleviating lithium deposition issues in the second electrode sheet 220.

[0087] In some embodiments, isolation layer 245 includes a layer formed from at least one of the following: polyolefin, polyolefin nitrile, polyol ester, polyamide, polyurethane, polyethylene terephthalate, or a composite containing at least one of polyolefin, polyolefin nitrile, polyol ester, polyamide, polyurethane, and polyethylene terephthalate. These materials are polymers that have excellent mechanical and electrical insulation properties and are highly chemically stable.

[0088] The first adhesive layer 244 and / or the second adhesive layer 246 may be formed from at least one of the following: polyolefin, polyurethane, polyacrylate, silicone, rubber, or a composite containing at least one of polyolefin, polyurethane, polyacrylate, silicone, and rubber. These materials, used as the material for the first adhesive layer 244 and / or the second adhesive layer 246, have good permeability and high adhesive strength after polymerization.

[0089] In addition, those skilled in the art may also make other changes within the technical concept of the present application. Of course, these changes made based on the technical concept of the present application should be included in the scope disclosed in the present application.

Claims

1. A battery cell, comprising: A first electrode tab; A second electrode tab, the polarity of the second electrode tab being opposite to that of the first electrode tab; A separator disposed between the first electrode tab and the second electrode tab, and the first electrode tab, the separator, and the second electrode tab are wound along a winding direction to form an electrode assembly; Characterized in that, along the winding direction, the first electrode tab includes a first winding starting segment located at the innermost layer and the first layer of the electrode assembly, the first winding starting segment has a first winding starting end, and the battery cell further includes: A first insulating member disposed on both sides of a part of the first winding starting segment and extending beyond the first winding starting end along a first direction, and the extended part is the first part of the first insulating member, and the first direction is the length direction of the first electrode tab.

2. The battery cell according to claim 1, characterized in that, The first winding starting segment is provided with a notch, and the first insulating member at least partially covers the notch and is adhesively bonded to each other at the notch.

3. The battery cell according to claim 1, characterized in that, The length of the first part is C mm, 30≥C≥1.

5.

4. The battery cell according to any one of claims 1-3, characterized in that, Along the winding direction, the second electrode tab includes a second winding starting segment located at the innermost layer and the first layer of the electrode assembly, the length of the second winding starting segment is B mm, the length of the first winding starting segment is A mm, the length of the first part is C mm, 5≥B - A≥C.

5. The battery cell according to any one of claims 1-3, characterized in that, Along the winding direction, the length of the first winding starting segment is A mm, the length of the first part is C mm, and the width of the electrode assembly is W mm, C + A≤W.

6. The battery cell according to any one of claims 1-3, characterized in that, The first insulating member further includes a second part, the second part is the part of the first insulating member adhesively bonded to the first winding starting segment, the length of the second part is D mm, the length of the first part is C mm, 10C≥D≥3C.

7. The battery cell according to any one of claims 1-3, characterized in that, The first electrode tab includes a first current collector and active material layers disposed on both sides of the first current collector. Along the thickness direction of the first winding starting segment, the thickness of the first insulating member is Eμm, the thickness of the first current collector is Fμm, and the thickness of the separator is Gμm, E + G≥3F.

8. The battery cell according to claim 7, wherein, 20≤E≤60。 9. The battery cell according to any one of claims 1-3, characterized in that The first insulating member further includes a third part, the third part is the part of the first insulating member extending beyond the first winding starting end along a third direction, the third direction is the width direction of the first electrode tab, and the length of the third part along the third direction is K mm, K≤2.

10. The battery cell according to claim 1, characterized in that, The first insulating member includes a first adhesive layer and an isolation layer, the first adhesive layer is disposed on the side of the isolation layer close to the first winding starting segment, and the first insulating member is adhesively fixed to the first winding starting segment through the first adhesive layer.

11. The battery cell according to any one of claims 1 to 3, characterized in that The first insulating member includes a first adhesive layer, an isolation layer, and a second adhesive layer, the second adhesive layer is disposed on the side of the isolation layer away from the first winding starting segment, and the first insulating member is adhesively fixed to the separator through the second adhesive layer.

12. The battery cell according to claim 10, characterized in that, The first insulating member is a hot melt adhesive.

13. The battery cell according to any one of claims 1 to 3, characterized in that, There is no empty foil area in the first winding starting segment.

14. The battery cell according to any one of claims 1-3, characterized in that, The battery cell further includes a second insulating member. Along the winding direction, the first pole piece further includes a first winding ending section located at the end of the outermost circle of the electrode assembly. Both sides of the first winding ending section are pasted with the second insulating member. The first winding ending section has a first winding ending end, and the second insulating member extends beyond the first winding ending end along a first direction.

15. The battery cell according to claim 14, wherein, The second insulating member includes a tail section, and the tail section is the part where the second insulating member extends beyond the first winding ending end along the first direction. The length of the tail section along the first direction is P mm. Along the winding direction, the second pole piece includes a second winding ending section, the length of the second winding ending section is N mm, the length of the first winding ending section is M mm, and N - M ≥ P.

16. The battery cell according to claim 11, wherein The separator layer includes a layer formed by at least one of the following: Polyolefin, polyacrylonitrile, polyol ester, polyamide, polyurethane, polyethylene terephthalate, and a composite containing at least one of polyolefin, polyacrylonitrile, polyol ester, polyamide, polyurethane, and polyethylene terephthalate; The first adhesive layer and / or the second adhesive layer includes a layer formed by at least one of the following: Polyolefin, polyurethane, polyacrylate, silicone, rubber, and a composite containing at least one of polyolefin, polyurethane, polyacrylate, silicone, and rubber.

17. A secondary battery, characterized in that, A battery cell including the battery cell according to any one of claims 1-16.

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