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] This application relates to the field of energy storage technology, and in particular to a battery cell and a secondary battery. Background Technology

[0002] A secondary battery consists of a cell and an electrolyte. The cell comprises a second electrode, a first electrode, and a separator. Secondary batteries primarily function by the movement of metal ions between the second and first electrodes. Among these processes, winding is crucial in battery manufacturing because it provides strong integration, giving the battery its initial shape. Therefore, the winding process acts as a pivotal link in the battery manufacturing process. During electrode winding, the electrodes are typically cut with a cutter, generating relatively large burrs that can easily puncture the separator at the starting end, causing a short circuit. Summary of the Invention

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

[0004] In a first aspect, embodiments of this application provide a battery cell including a first electrode, a second electrode, a separator, and a first insulating member. The polarity of the second electrode is opposite to that of the first electrode. The separator is disposed between the first and second electrodes. The first electrode, the separator, and the second electrode are wound along a winding direction to form an electrode assembly. Along the winding direction, the first electrode includes a first winding start segment located in the innermost first layer of the electrode assembly, and the first winding start segment has a first winding start end. The first insulating member is disposed on both sides of a portion of the first winding start segment and extends beyond the first winding start end along a first direction. The extended portion is the first part of the first insulating member, and the first direction is the length direction of the first electrode.

[0005] In the aforementioned battery cell, a first electrode, a second electrode, and a separator are wound along a winding direction to form an electrode assembly. The first electrode, located in the innermost layer of the electrode assembly, forms the first winding start section. Before the winding process, the first electrode is typically cut with a cutter. During this process, burrs are easily generated at the end of the first electrode. These burrs can easily cause the first electrode to puncture the separator at the first winding start end, resulting in a short circuit in the battery cell. By providing a first insulating member on both sides of a portion of the first winding start section, and along the length of the first electrode, the first winding start section has a first winding start end. The first insulating member extends beyond the first winding start end, and the extended portion is the first part of the first insulating member. This first part can shield the burrs on the first electrode at the first winding start end, protecting the separator between the first and second electrodes. This improves the problem of the electrode puncturing the separator at the start end and enhances the safety of the battery cell.

[0006] In one or more of the above embodiments, the first winding starting segment is provided with a slit, and the first insulating member at least partially covers the slit and is bonded to each other at the slit.

[0007] In the aforementioned battery cell, by providing a slit in the first winding start section, on the one hand, the slit helps to mark the first winding start section of the first electrode during the winding process, facilitating the adhesion of the first insulating element to the first winding start section and making it easier to start winding from the first winding start section with the slit. On the other hand, after the first insulating elements provided on both sides of the first winding start section cover the slit, they can adhere to each other at the slit, improving the adhesion strength between the two first insulating elements.

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

[0009] In the aforementioned battery cell, the length of the first part is greater than or equal to 1.5 mm, thereby increasing the bonding strength between the first insulating component and the first electrode, and improving the bonding firmness. Simultaneously, the length of the first part is less than or equal to 30 mm, so as to reduce the length of the first insulating component while meeting the bonding strength requirements, thus mitigating the problem of bending in the first part and improving the battery cell's safety without affecting its energy density.

[0010] In one or more of the above embodiments, along the winding direction, the second electrode includes a second winding starting segment located in the innermost 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, and 5≥BA≥C.

[0011] In the aforementioned battery cell, along the winding direction, the length of the second winding starting segment is greater than the length of the first winding starting segment, and the length of the second winding starting segment exceeding the length of the first winding starting segment is greater than or equal to the length of the first part of the first insulating member and does not exceed 5mm. This is to reduce the hollow area of ​​the second electrode in the thickness direction of the battery cell after the first electrode, the separator, and the second electrode are wound along the winding direction to form an electrode assembly, thereby reducing the lithium plating problem at the starting end of the second electrode.

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

[0013] In the aforementioned battery cell, along the winding direction, the sum of the length of the first winding starting segment and the length of the first part is less than or equal to the width of the electrode assembly. This is to improve the situation where the first insulating member folds due to its excessive length in the innermost layer of the electrode assembly winding. The first insulating member remains a single-layer structure, thereby reducing the impact of the first insulating member 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 part, which is the portion of the first insulating member adhered to the first winding starting section. The length of the second part is D mm, the length of the first part is C mm, and 10C≥D≥3C.

[0015] In the aforementioned battery cell, the length of the portion of the first insulating member bonded to the first winding start section is greater than or equal to three times the length of the portion of the first insulating member extending out of the first winding start section along the winding direction, and less than or equal to ten times the length of the portion of the first insulating member extending out of the first winding start section along the winding direction, in order to improve the bonding stability between the first insulating member and the first winding start section.

[0016] In one or more of the above embodiments, the first electrode 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 start section, the thickness of the first insulating member is E μm, the thickness of the first current collector is F μm, the thickness of the separator is G μm, and E+G≥3F.

[0017] Before the aforementioned battery cell is wound, 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 these burrs is usually 2 to 3 times the thickness of the first current collector. By setting the sum of the thickness of the first insulating component and the separator 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 component and the separator, thereby improving the problem of short circuit between the positive and negative electrodes caused by the burrs on the edge of the first current collector piercing the separator and enhancing the safety of the battery cell.

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

[0019] In the aforementioned battery cell, the thickness of the first insulating component is set to be greater than 20μm and less than 60μm, so that when the first insulating component is attached to the first winding start section, the thickness of the first insulating component reduces the influence of the thickness of the first insulating component on the thickness of the innermost layer of the electrode assembly winding.

[0020] In one or more of the above embodiments, the first insulating member further includes a third part, which is the portion of the first insulating member that extends beyond the first winding start end along a third direction, where the third direction is the width direction of the first electrode sheet, and the length of the third part along the third direction is K mm, where K≤2.

[0021] In the aforementioned battery cell, the length of the portion of the first insulating member extending beyond the first winding start end along the width direction of the first electrode is less than or equal to 3 mm. This allows the first insulating member to shield the end of the first electrode along its width direction, thereby protecting the separator between the first and second electrodes. This improves the problem of the electrode puncturing the separator at the start end and enhances 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 insulating layer. The first adhesive layer is disposed on the side of the insulating layer near the first winding start section. The first insulating member is bonded and fixed to the first winding start section through the first adhesive layer.

[0023] In the aforementioned battery cell, the first insulating component is bonded and fixed to the first winding starting section through the first adhesive layer. The first adhesive layer serves as a connection, while the insulating layer serves as a protection. The insulating layer is used to contact the burrs on the cutting edge of the first current collector to isolate the first electrode and the diaphragm. The first adhesive layer fixes the insulating 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 disposed on the side of the isolation layer away from the first winding start section. The first insulating member is bonded and fixed to the diaphragm through the second adhesive layer.

[0025] In the aforementioned battery cell, the second adhesive layer is disposed on the side of the insulating layer away from the first winding start section, so that both sides of the first insulating member are adhesive. 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 element is hot melt adhesive.

[0027] In the aforementioned battery cell, hot melt adhesive is a plastic adhesive whose physical state changes with temperature within a certain temperature range, while its chemical properties remain unchanged, thus making the fixing relationship between the first insulating component and the first electrode plate more secure.

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

[0029] In the aforementioned battery cell, the first winding starting section has no empty foil area, so that the first winding starting section has sufficient reaction area in the innermost layer of the electrode assembly winding. At the same time, the absence of empty foil area in the first winding starting section enables the first insulating component to have a flat bonding surface, improving the bonding stability of the first insulating component.

[0030] In one or more of the above embodiments, the battery cell further includes a second insulating member. Along the winding direction, the first electrode also includes a first winding termination section located at the outermost end of the electrode assembly. The second insulating member is attached to both sides of the first winding termination section. The first winding termination section has a first winding termination end. The second insulating member extends beyond the first winding termination end along a first direction.

[0031] In the aforementioned battery cell, a first electrode, a second electrode, and a separator are wound along a winding direction to form an electrode assembly. The outermost end of the first electrode at the electrode assembly is the first winding termination section. Before the winding process, the first electrode is typically cut with a cutter. During this process, burrs are easily generated at the end of the first electrode. These burrs can easily cause the first electrode to puncture the separator at the first winding termination section, resulting in a short circuit in the battery cell. By providing second insulating members on both sides of the first winding termination section, and along the length direction of the first electrode, the first winding termination section has a first winding termination end, and the second insulating members extend beyond the first winding termination end, the second insulating members can shield the burrs on the first electrode at the first winding termination end, thus protecting the separator between the first and second electrodes. This improves the problem of the electrode puncturing the separator at the termination end and enhances 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 the 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 electrode includes a second winding tail section, the length of the second winding tail section is N mm, the length of the first winding tail section is M mm, and NM≥P.

[0033] In the aforementioned 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 length of the first winding tail section is greater than or equal to the length of the tail section of the second insulating component. This is to improve the ion insertion space of the second electrode after the first electrode, the separator, and the second electrode are wound along the winding direction to form an electrode assembly, thereby improving the lithium plating problem of the second electrode and increasing the capacity and charge / discharge performance of the battery cell.

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

[0035] Polyolefins, polyacrylonitrile, polyol esters, polyamides, polyurethanes, polyethylene terephthalate, and complexes containing at least one of polyolefins, polyacrylonitrile, polyol esters, polyamides, polyurethanes, and polyethylene terephthalate;

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

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

[0038] In the aforementioned battery cell, the insulating layer comprises a layer formed of 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. These materials are polymeric materials with good mechanical and electrical insulation properties and high chemical stability. The first adhesive layer and / or the second adhesive layer comprises a layer formed of 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, as materials for the first adhesive layer and / or the second adhesive layer, have good permeability and high adhesive strength after polymerization.

[0039] Secondly, embodiments of this application provide a secondary battery, including the battery cell in any of the above embodiments.

[0040] The aforementioned secondary battery, by employing the aforementioned battery cell, can improve the problem of the electrode plates puncturing the separator at the starting end, thereby enhancing the safety of the secondary battery. Attached Figure Description

[0041] Figure 1 is a schematic diagram of the overall structure of the secondary battery in one embodiment of this application.

[0042] Figure 2 is a schematic diagram of the disassembled structure of a secondary battery in one embodiment of this application.

[0043] Figure 3 is a schematic diagram of the winding cross-sectional structure of the battery cell in one embodiment of this application, which shows the structural schematic diagram cut along “Ⅲ-Ⅲ” in Figure 2.

[0044] Figure 4 is a schematic diagram of the fixing relationship between the first winding starting segment and the first insulating member in one embodiment of this application.

[0045] Figure 5 is a top view schematic diagram of the fixing relationship between the first winding starting segment and the first insulating member in one embodiment of this application.

[0046] Figure 6 is a schematic diagram of the layer structure of the first insulating element in one embodiment of this application.

[0047] Figure 7 is a schematic diagram of the fixing relationship between the first winding end section and the second insulating member in one embodiment of this application.

[0048] Key Component Symbols: 100 Secondary Battery; 200 Cell; 210 First Electrode; 211 First Winding Start Section; 2111 First Winding Start End; 2112 Cut; 212 First Current Collector; 213 Active Material Layer; 214 First Winding End Section; 2141 First Winding End End; 220 Second Electrode; 221 Second Winding Start Section; 230 Separator; 240 First Insulator; 241 First Part; 242 Second Part; 243 Third Part; 244 First Adhesive Layer; 245 Separator Layer; 246 Second Adhesive Layer; 250Second insulating component 251, tail section R, winding direction X, first direction Y, second direction Z, third direction 300, electrode tab 400, housing.

[0049] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all 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 an element that is interposed in between. When an element is considered to be "set" on another element, it can be directly set on the other element or there may be an element that is interposed in between. Those skilled in the art will understand the specific meaning of the above terms in this application according to the specific circumstances. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "comprising" and any variations thereof in the specification, claims, and foregoing description of the drawings are intended to cover a non-exclusive inclusion.

[0053] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0054] The term "perpendicular" is used to describe an ideal state between two components. In actual production or use, two components can exist in a state that is approximately perpendicular. For example, in numerical terms, perpendicularity can refer to the angle between two straight lines within the range of 90° ± 10°, the dihedral angle between two planes within the range of 90° ± 10°, or the angle between a straight line and a plane within the range of 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 A is greater than B by 10, it should be understood that it includes the case where A is greater than B by 9, as well as the case where A is greater than B by 11.

[0056] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. Where there is no conflict, the various embodiments in this application can be combined with each other.

[0057] It should be noted that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative examples and should not constitute any limitation on this application.

[0058] Embodiments of this application provide a battery cell including a first electrode, a second electrode, a separator, and a first insulating member. The polarity of the second electrode is opposite to that of the first electrode. The separator is disposed between the first and second electrodes. The first electrode, separator, and second electrode are wound along a winding direction to form an electrode assembly. Along the winding direction, the first electrode includes a first winding start segment located in the innermost first layer of the electrode assembly, and the first winding start segment has a first winding start end. The first insulating member is disposed on both sides of a portion of the first winding start segment and extends beyond the first winding start end along a first direction. The extended portion is the first part of the first insulating member, and the first direction is the length direction of the first electrode.

[0059] In the aforementioned battery cell, a first electrode, a second electrode, and a separator are wound along a winding direction to form an electrode assembly. The first electrode, located in the innermost layer of the electrode assembly, forms the first winding start section. Before the winding process, the first electrode is typically cut with a cutter. During this process, burrs are easily generated at the end of the first electrode. These burrs can easily cause the first electrode to puncture the separator at the first winding start end, resulting in a short circuit in the battery cell. By providing a first insulating member on both sides of a portion of the first winding start section, and along the length of the first electrode, the first winding start section has a first winding start end. The first insulating member extends beyond the first winding start end, and the extended portion is the first part of the first insulating member. This first part can shield the burrs on the first electrode at the first winding start end, protecting the separator between the first and second electrodes. This improves the problem of the electrode puncturing the separator at the start end and enhances the safety of the battery cell.

[0060] The following describes some embodiments of this application in detail with reference to the accompanying drawings.

[0061] Please refer to Figures 1 and 2. One embodiment of this application provides a secondary battery 100, including a cell 200, tabs 300, and a casing 400. The cell 200 has a wound structure, and the cell 200 and the tabs 300 are housed in the casing 400. The tabs 300 are electrically connected to the cell 200 and partially extend out of the casing 400. A first direction X is defined as the width direction of the secondary battery 100 and the cell 200, a second direction Y is defined as the thickness direction of the secondary battery 100 and the cell 200, and a third direction Z is defined as the length direction of the secondary battery 100 and the cell 200. The first direction X, the second direction Y, and the third direction Z are all 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 casing 400. The electrolyte composition includes a solvent, a lithium salt, and additives. The solvent may be a cyclic carbonate (PC, EC), a chain carbonate (DEC, DMC, EMC), a carboxylic acid ester (MF, MA, EA, MP), other organic solvents, or combinations thereof. The lithium salt may be LiPF6, LiBF4, LiClO4, LiB(C6H), LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiBOB, etc.

[0064] It should be noted that after the battery cell 200 is wound, it usually needs to undergo a hot-pressing process to make the winding structure more compact and formed. Then, the battery cell 200 is installed into the housing 400 and electrolyte is injected. Understandably, for clarity, the electrolyte is omitted in Figure 2.

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

[0066] Please refer to Figure 3. An embodiment of this application provides a battery cell 200, including a first electrode 210, a second electrode 220, a separator 230, and a first insulating member 240. The polarity of the second electrode 220 is opposite to that of the first electrode 210. The separator 230 is disposed between the first electrode 210 and the second electrode 220. The first electrode 210, the separator 230, and the second electrode 220 are wound along the 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 210 includes a first winding start segment 211 located in the innermost first layer of the electrode assembly, the first winding start segment 211 having a first winding start end 2111.

[0069] It is worth noting that the first electrode 210 has straight sections and curved sections during the winding process. The length of the straight sections extends substantially parallel to the first direction X, and multiple straight sections are stacked along the second direction Y. The curved sections connect the two straight sections along the winding direction R. The first winding starting section 211 is the part of the first electrode 210 in the innermost layer of the electrode assembly, that is, the part of the innermost straight section. The innermost layer of the first electrode 210 in the electrode assembly refers to the ring of the first electrode 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 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 start 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≥3F. Since burrs are generated at the cut edge of the first current collector 212 during the cutting process, and the size of these burrs is typically 2 to 3 times the thickness of the first current collector 212, by setting the sum of the thicknesses of the first insulating member 240 and the separator 230 to 3 times the thickness of the first current collector 212, the burrs at the edge of the first current collector 212 can be effectively blocked by the first insulating member 240 and the separator 230. This improves the problem of short circuits caused by burrs at the edge of the first current collector 212 piercing the separator 230, thereby enhancing 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, the influence of the thickness of the first insulating member 240 on the thickness of the innermost layer of the electrode assembly winding is reduced when the first insulating member 240 is attached to the first winding start segment 211. The thickness of the innermost layer of the electrode assembly winding refers to the total thickness of the first electrode 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 start section 211 and extends beyond the first winding start end 2111 along the first direction X. The portion extending beyond the first winding start end 2111 is the first part 241 of the first insulating member 240. The first direction X is the length direction of the first electrode 210 and also the width direction of the aforementioned battery cell 200. By providing the first insulating member 240 on both sides of the first winding start section 211, and with the first part 241 extending beyond the first winding start end 2111 along the first direction X, the burrs on the first electrode 210 at the first winding start end 2111 are blocked, thereby protecting the separator 230 between the first electrode 210 and the second electrode 220, improving the problem of the electrode piercing the separator 230 at the start end, and enhancing the safety of the battery cell 200.

[0073] In some embodiments, along the winding direction R, the length of the first winding starting segment 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 segment 211 and the length of the first part 241 is less than or equal to the width of the electrode assembly. This is to improve the situation where the first insulating member 240 folds due to its excessive length in the innermost layer of the electrode assembly winding. The first insulating member 240 remains a single-layer structure, thereby reducing the impact of the first insulating member 240 on the overall thickness of the electrode assembly.

[0074] In some embodiments, the length of the first part 241 is C mm, where 30 ≥ C ≥ 1.5. The length of the first part 241 is greater than or equal to 1.5 mm, thereby increasing the bonding strength between the first insulating member 240 and the first electrode 210, and improving the bonding firmness. Simultaneously, the length of the first part 241 is less than or equal to 30 mm, reducing the length of the first insulating member 240 while still meeting the bonding strength requirements, thus mitigating the problem of bending of the first part 241 and improving the safety of the battery cell 200 without affecting its energy density.

[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 segment 211, that is, the second portion 242 is the part of the first insulating member 240 bonded to the first winding start segment 211. The length of the second portion 242 is D mm, where 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 out of the first winding start segment 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 out of the first winding start segment 211 along the winding direction R, in order to improve the bonding stability between the first insulating member 240 and the first winding start segment 211.

[0076] Referring to Figure 5, in some embodiments, the first insulating member 240 further includes a third portion 243 extending beyond the first winding start end 2111 along a third direction Z. That is, the third portion 243 is the part of the first insulating member 240 extending beyond the first winding start end 2111 along a third direction Z. The third direction Z is the width direction of the first electrode 210 and also the length direction of the cell 200. The length of the third portion 243 along the third direction Z is K mm, K≤2, so that the first insulating member 240 can block the end of the first electrode 210 in the width direction along the width direction of the first electrode 210 to protect the diaphragm 230 between the first electrode 210 and the second electrode 220, thereby improving the problem of the electrode piercing the diaphragm 230 at the start end and improving the safety of the cell 200.

[0077] It is worth noting that the length of the third part 243 along the third direction Z mentioned above refers to the length of the first insulating member 240 extending beyond one side of the first winding start end 2111 along the third direction Z. That is, the first insulating member 240 may include two third parts 243, each of which extends beyond one side of the first winding start end 2111 along the third direction Z, and the length of the third part 243 on each side is less than or equal to 2mm; the first insulating member 240 may also include one third part 243, which extends beyond either side of the first winding start 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 insulating layer 245. The first adhesive layer 244 is disposed on the side of the insulating layer 245 near the first winding start section 211. The first insulating member 240 is bonded and fixed to the first winding start section 211 by the first adhesive layer 244. The first adhesive layer 244 serves as a connector, while the insulating layer 245 serves as a protector. The insulating layer 245 is used to contact the burrs on the cut edge of the first current collector 212 to isolate the first electrode 210 and the diaphragm 230. The first adhesive layer 244 fixes the insulating layer 245 by adhesive force.

[0079] In some embodiments, the first insulating member 240 further includes a second adhesive layer 246, which is disposed on the side of the insulating layer 245 away from the first winding start section 211. The first insulating member 240 is bonded and fixed to the diaphragm 230 through the second adhesive layer 246. Both sides 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 element 240 is a 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 makes the fixing relationship between the first insulating element 240 and the first electrode 210 more secure, thereby improving the problem of the position of the first insulating element 240 changing within the battery cell 200. Because hot melt adhesive is a solid, it is easy to package, transport, and store. Hot melt adhesive is solid at room temperature, but when heated to a certain temperature, it becomes a flowable liquid with a certain viscosity, resulting in high adhesive strength. This facilitates the adhesion of the first insulating adhesive to the first winding starting segment 211.

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

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

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

[0084] The first winding termination section 214 has a second insulating element 250 attached to both sides. The first winding termination section 214 has a first winding termination end 2141, and the second insulating element 250 extends beyond the first winding termination end 2141 along the first direction X. Since the first winding termination end 2141 will also leave burrs after being cut by the cutter, these burrs can easily cause the first electrode 210 to puncture the diaphragm 230 at the first winding termination end 2141, so that the first electrode 210 and the second electrode 220 are connected, causing a short circuit in the cell 200. By providing second insulating members 250 on both sides of the first winding end section 214, and along the length direction of the first electrode 210, the first winding end section 214 has a first winding end 2141, and the second insulating member 250 extends beyond the first winding end 2141. The second insulating member 250 can block the burrs of the first electrode 210 at the first winding end 2141 to protect the diaphragm 230 between the first electrode 210 and the second electrode 220, thereby improving the problem of the electrode puncturing the diaphragm 230 at the end and improving the safety of the cell 200.

[0085] In some embodiments, the second insulating member 250 includes a tail portion 251, which is the portion of the second insulating member 250 extending beyond the first winding tail end 2141 along the first direction X. The length of the tail portion 251 along the first direction X is P mm. Along the winding direction R, the second electrode 220 includes a second winding tail section, the length of which is N mm. The length of the first winding tail section 214 is M mm, where NM≥P. The length of the second winding tail section is greater than the length of the first winding tail section 214, and the length of the second winding tail section extending beyond the first winding tail section 214 is greater than or equal to the length of the tail portion 251 of the second insulating member 250. This improves the ion insertion space of the second electrode 220 after the first electrode 210, the separator 230, and the second electrode 220 are wound along the winding direction R to form an electrode assembly, thereby improving the lithium plating problem of the second electrode 220 and increasing the capacity and charge / discharge performance of the cell 200. Understandably, the ion intercalation space is the intercalation space of lithium ions.

[0086] Referring to Figure 3, in some embodiments, along the winding direction R, the second electrode 220 includes a second winding start segment 221 located in the innermost first 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 part 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, and the length of the second winding start segment 221 extending beyond the first winding start segment 211 is greater than or equal to the length of the first part 241 of the first insulating member 240 and does not exceed 5 mm. This is to reduce the hollow area of ​​the second electrode 220 in the thickness direction of the cell 200 after the first electrode 210, the separator 230, and the second electrode 220 are wound along the winding direction R to form the electrode assembly, thereby reducing the lithium plating problem of the second electrode 220.

[0087] In some embodiments, the insulating layer 245 comprises a layer formed of 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. These materials are polymeric materials with good mechanical and electrical insulation properties and high chemical stability.

[0088] The first adhesive layer 244 and / or the second adhesive layer 246 comprise layers formed of at least one of the following: polyolefin, polyurethane, polyacrylate, silicone, rubber, and composites containing at least one of polyolefin, polyurethane, polyacrylate, silicone, and rubber. These substances, as materials for the first adhesive layer 244 and / or the second adhesive layer 246, exhibit good permeability and high adhesive strength after polymerization.

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

Claims

1. A battery cell, comprising: First electrode plate; The second electrode has a polarity opposite to that of the first electrode. A diaphragm is disposed between the first electrode and the second electrode, and the first electrode, the diaphragm, and the second electrode are wound together along a winding direction to form an electrode assembly; The feature is that, along the winding direction, the first electrode includes a first winding starting segment located in the innermost first layer of the electrode assembly, the first winding starting segment having a first winding starting end, and the battery cell further includes: A 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 extended portion is the first part of the first insulating member, and the first direction is the length direction of the first electrode sheet.

2. The battery cell as described in claim 1, characterized in that, The first winding starting section is provided with a slit, and the first insulating member at least partially covers the slit and is bonded to each other at the slit.

3. The battery cell as described in claim 1, characterized in that, The length of the first part is C mm, and 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 includes a second winding starting segment located in the innermost 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, and the length of the first part is C mm, where 5 ≥ BA ≥ 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, where 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, which is the portion of the first insulating member adhered to the first winding starting section. The length of the second part is D mm, and the length of the first part is C mm, where 10C≥D≥3C.

7. The battery cell according to any one of claims 1-3, characterized in that, The first electrode 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 start section, the thickness of the first insulating element is E μm, the thickness of the first current collector is F μm, and the thickness of the separator is G μm, where E+G≥3F.

8. The battery cell as described in claim 7, characterized in that, 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, which is the portion of the first insulating member that extends beyond the first winding start end along a third direction, where the third direction is the width direction of the first electrode sheet, and the length of the third part along the third direction is K mm, where K≤2.

10. The battery cell as described in claim 1, characterized in that, The first insulating member includes a first adhesive layer and an insulating layer. The first adhesive layer is disposed on the side of the insulating layer near the first winding start section. The first insulating member is bonded and fixed to the first winding start section through the first adhesive layer.

11. The battery cell according to any one of claims 1-3, characterized in that, The first insulating member includes a first adhesive layer, an insulating layer, and a second adhesive layer. The second adhesive layer is disposed on the side of the insulating layer away from the first winding start section. The first insulating member is bonded and fixed to the diaphragm through the second adhesive layer.

12. The battery cell as described in claim 10, characterized in that, The first insulating component is hot melt adhesive.

13. The battery cell according to any one of claims 1-3, characterized in that, The first winding starting section has no empty foil area.

14. The battery cell according to any one of claims 1-3, characterized in that, The battery cell also includes a second insulating member. Along the winding direction, the first electrode also includes a first winding termination section located at the outermost end of the electrode assembly. The second insulating member is attached to both sides of the first winding termination section. The first winding termination section has a first winding termination end. The second insulating member extends beyond the first winding termination end along a first direction.

15. The battery cell as described in claim 14, characterized in that, The second insulating member includes a tail portion, which is the portion of the second insulating member that extends beyond the first winding tail end along a first direction, and the length of the tail portion along the first direction is P mm; Along the winding direction, the second electrode includes a second winding termination section, the length of which is N mm, and the length of which is M mm, where NM ≥ P.

16. The battery cell as described in claim 11, characterized in that, The isolation layer comprises a layer formed by at least one of the following: Polyolefins, polyacrylonitrile, polyol esters, polyamides, polyurethanes, polyethylene terephthalate, and complexes containing at least one of polyolefins, polyacrylonitrile, polyol esters, polyamides, polyurethanes, and polyethylene terephthalate; The first adhesive layer and / or the second adhesive layer comprise layers formed of at least one of the following: Polyolefins, polyurethanes, polyacrylates, silicones, rubber, and compounds containing at least one of polyolefins, polyurethanes, polyacrylates, silicones, and rubber.

17. A secondary battery, characterized in that, Includes the battery cell as described in any one of claims 1-16.

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