Roll core structure, secondary battery and electric equipment
By adding grooves and protrusions at the corner arc sections of the core structure, the stress mismatch problem at the corners of the wound lithium-ion battery is solved, achieving uniform distribution of electronic capacity and improving the battery's cycle performance and safety.
Patent Information
- Application Number
- CN202423278595.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2026-01-13
- Estimated Expiration
- 2034-12-30
AI Technical Summary
Existing wound lithium-ion batteries suffer from excessive stress at the corners, leading to a mismatch between the positive electrode and the negative electrode, which easily causes lithium deposition, increases cell thickness, and poses a safety risk of internal short circuits, thus reducing safety and stability in use.
Grooves and protrusions are added at the corner arc sections of the core structure. The first electrode is thinned by setting grooves and the second electrode is thickened by setting protrusions, so as to achieve a uniform distribution of electron capacity and avoid lithium plating.
This achieves longer cycle life, structural stability, and safety of the battery, avoids lithium plating at corners, and improves the overall safety and stability of the battery.
Smart Images
Figure CN223797375U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of battery technology, and in particular relates to a core structure, a secondary battery, and an electrical device. Background Technology
[0002] With the advent of the electronic age, portable power banks have been applied to all aspects of life. Currently, lithium-ion batteries, while meeting energy density requirements, are increasingly demanded products with more and more efficient charging capabilities. Wound lithium-ion batteries, characterized by combining the positive and negative electrodes through winding, offer advantages such as high production efficiency and low cost, and have become one of the commonly used battery types.
[0003] However, most existing wound batteries suffer from excessive stress at the corners and mismatch in CB (Cell Balance, electrode capacity) caused by the positive electrode covering the negative electrode. This can easily lead to lithium deposition at the corners. The resulting lithium dendrites not only increase the cell thickness but also pose a safety risk of internal short circuit due to puncturing the separator, thus reducing the safety and stability of use. Utility Model Content
[0004] The purpose of this invention is to provide a core structure that addresses the shortcomings of existing technologies and solves the technical problems of low safety and stability in the use of existing technologies.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A wound core structure includes a first electrode, a second electrode, and a separator disposed between the first electrode and the second electrode; the first electrode, the separator, and the second electrode are sequentially wound to form a wound body; the wound body has at least one corner arc segment; the first electrode has at least one groove; the second electrode has at least one protrusion; and both the groove and the protrusion are disposed on the corner arc segment.
[0007] Preferably, the first electrode includes a first current collector and a first active material layer disposed on at least one surface of the first current collector; the groove is disposed on the first active material layer; and the groove is recessed from the first active material layer toward the first current collector;
[0008] The second electrode includes a second current collector and a second active material layer disposed on at least one surface of the second current collector; the protrusion is disposed on the second active material layer and extends from the second current collector toward the second active material layer;
[0009] Furthermore, the projection of the groove toward the isolation membrane and the projection of the protrusion toward the isolation membrane are at least partially overlapped.
[0010] Preferably, the first electrode is a positive electrode; the second electrode is a negative electrode.
[0011] Preferably, the relationship between the thickness H2 of the groove and the thickness T4 of the first active material layer satisfies: H2 = (1 / 5 ~ 1 / 4) * T4.
[0012] Preferably, the relationship between the thickness H1 of the protrusion and the thickness T3 of the second active material layer satisfies: H1 = (1 / 4 ~ 1 / 3) * T3.
[0013] Preferably, in the wound body, the number of layers n and the length K of the recess 101 in the nth layer are specified. n The relationship between the thickness T4 of the first active material layer, the thickness T5 of the first current collector, the thickness T1 of the separator, the thickness T3 of the second active material layer, and the thickness T2 of the second current collector satisfies: K n =π*[2*(n+1)T1+nT2+(2n-1)T3+n*T4+(2n-1.5)*T5].
[0014] Preferably, in the wound body, the number of layers n and the length M of the protrusion in the nth layer are... n The relationship between the thickness T4 of the first active material layer, the thickness T5 of the first current collector, the thickness T1 of the separator, the thickness T3 of the second active material layer, and the thickness T2 of the second current collector satisfies: M n =π*[(2n+1)*T1+n*T2+(n-1)*T4+2*(n-1)T5+(2n-1.5)*T3].
[0015] Preferably, in the wound body, the number of layers n and the length K of the recess in the nth layer are... n The length M of the protrusion n The ratio is K n / M n The relationship between the thickness T4 of the first active material layer, the thickness T5 of the first current collector, the thickness T1 of the separator, the thickness T3 of the second active material layer, and the thickness T2 of the second current collector satisfies: K n / M n ≥[2(n+1)*T1+nT2+(2n-1)*T3+nT4+(2n-1.5)*T5] / [(2n+1)*T1+nT2+(n-1)*T4+2(n-1)*T5+(2n-1.5)*T3].
[0016] This utility model also discloses a secondary battery, including the aforementioned core structure.
[0017] This utility model also discloses an electrical device, including the aforementioned secondary battery.
[0018] The beneficial effects of this utility model are as follows: by adding at least one groove at the corner arc section of the first electrode, the surface capacity at that location is reduced, thereby achieving a more uniform overall electron capacity. Furthermore, by adding at least one protrusion at the corner arc section of the second electrode, the surface capacity at that location is increased, thereby achieving a more uniform overall electron capacity. This avoids problems such as lithium plating in the corner arc section of the core structure, achieving longer cycle performance and improved stability and safety in structural use. Attached Figure Description
[0019] The following will refer to the appendix. Figures 1-4 This section describes the features, advantages, and technical effects of exemplary embodiments of the present invention.
[0020] Figure 1 This is a schematic diagram of the exploded state of the core structure according to an embodiment of the present invention;
[0021] Figure 2 This is a partial structural schematic diagram of the core structure in the winding state according to an embodiment of the present invention;
[0022] Figure 3 This is a schematic diagram of the structure of the first electrode sheet of a core structure according to an embodiment of the present invention;
[0023] Figure 4 This is a schematic diagram of the structure of the second pole piece of the core structure according to an embodiment of the present invention.
[0024] In the figure: 100-first electrode; 101-groove; 110-first active material layer; 120-first current collector; 200-second electrode; 201-protrusion; 210-second active material layer; 220-second current collector; 300-separation membrane; 41-straight section; 42-corner arc section. Detailed Implementation
[0025] 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 pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.
[0026] 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.
[0027] 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 separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0028] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or multiple situations existing alone. In addition, the character " / " in this document generally indicates that the related objects before and after are in an "or" relationship.
[0029] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.
[0030] The following is in conjunction with the appendix Figures 1-4 The present invention will be described in further detail, but this is not intended to limit the scope of the present invention.
[0031] like Figure 1 and 2 As shown, in one embodiment of this utility model, the core structure includes a first electrode 100, a second electrode 200, and a separator 300 disposed between the first electrode 100 and the second electrode 200; the first electrode 100, the separator 300, and the second electrode 200 are sequentially wound to form a wound body; the wound body has at least one straight section and at least one corner arc section 42 that are interleaved; the first electrode 100 is provided with at least one groove 101; the second electrode 200 is provided with at least one protrusion 201; and both the groove 101 and the protrusion 201 are disposed on the corner arc section 42.
[0032] The technical solution of this utility model adds at least one groove at the corner arc section of the first electrode to achieve thinning treatment at that position, thereby reducing the areal capacity at that position and achieving overall electron capacity uniformity as much as possible; and adds at least one protrusion at the corner arc section of the second electrode to achieve thickening treatment at that position, thereby increasing the areal capacity at that position and achieving overall electron capacity uniformity as much as possible; thus avoiding problems such as lithium plating in the corner arc section of the core structure, achieving longer cycle performance and stability and safety of structural use.
[0033] Specifically, in some implementations, such as Figure 1 As shown, the first electrode 100 includes a first current collector 120 and a first active material layer 110 disposed on at least one surface of the first current collector 120; a groove 101 is disposed on the first active material layer 110; and the groove 101 is recessed from the first active material layer 110 toward the first current collector 120; the second electrode 200 includes a second current collector 220 and a second active material layer 210 disposed on at least one surface of the second current collector 220; a protrusion 201 is disposed on the second active material layer 210, and the protrusion 201 extends from the second current collector 220 toward the second active material layer 210; and the projection of the groove 101 toward the separator 300 and the projection of the protrusion 201 toward the separator 300 at least partially overlap. The groove 101 can be disposed on either the first active material layer 110 above or below the first current collector 120; or the groove 101 can be disposed on both the first active material layers 110 above and below the first current collector 120. The protrusion 201 can be disposed above or below any one of the second active material layers 210 of the second current collector 220; or the protrusion 201 can be disposed above and below the second active material layers 210 of the second current collector 220 respectively. In addition, the positions of the protrusion 201 and the positions of the groove 101 can be arbitrarily combined with each other.
[0034] Specifically, in some embodiments, the first electrode 100 is the positive electrode, and the second electrode 200 is the negative electrode. Since the positive and negative electrodes at various positions on the wound core correspond one-to-one, but the situation varies at the corner arc positions, one surface (long film surface) of the positive electrode wraps around one surface (long film surface) of the negative electrode; the other surface (short film surface) of the positive electrode is wrapped around the other surface (short film surface) of the negative electrode. That is, at the actual corner arc positions, the CB value at one surface position is smaller than the CB value at the planar position; the CB value at the other surface position is larger than the CB value at the planar position. Therefore, it is necessary to thin the positive electrode and thicken the negative electrode to avoid lithium plating and other problems in the corner arc section of the wound core structure, thereby achieving longer cycle performance and structural stability and safety.
[0035] The positive electrode current collector can be made of aluminum, and the positive electrode active material layer includes a positive electrode active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode current collector can be made of copper, and the negative electrode active material layer includes a negative electrode active material, which can be carbon or silicon, etc. The separator 300 can be made of PP (polypropylene) or PE (polyethylene), etc.
[0036] Specifically, in some implementations, such as Figure 1 and 3 As shown, the relationship between the thickness H2 of the groove 101 and the thickness T4 of its first active material layer 110 satisfies: H2 = (1 / 5 to 1 / 4) * T4. Preferably, H2 = 1 / 5 * T4. That is, by using a groove 101 of appropriate thickness, the areal capacity reduction at the corner arc segment can be effectively controlled to achieve the most uniform overall electron capacity; thereby avoiding problems such as lithium plating in the corner arc segment of the core structure, achieving longer cycle performance and stability and safety of the structure.
[0037] Specifically, in some implementations, such as Figure 1 and 4 As shown, the relationship between the thickness H1 of the protrusion 201 and the thickness T3 of its second active material layer 210 satisfies: H1 = (1 / 4 ~ 1 / 3) * T3. Preferably, H1 = 1 / 3 * T3. That is, by using a protrusion 201 of appropriate thickness, the areal capacity at the corner arc segment can be effectively controlled to achieve the most uniform overall electron capacity; thereby avoiding problems such as lithium plating in the corner arc segment of the core structure, achieving longer cycle performance and stability and safety of the structure.
[0038] Specifically, in some implementations, such as Figure 1 , 3 As shown in Figure 4, in the winding body, the number of layers n and the length K of the recess 101 in the nth layer are... n The relationship between the thickness T4 of the first active material layer 110, the thickness T5 of the first current collector 120, the thickness T1 of the separator 300, the thickness T3 of the second active material layer 210, and the thickness T2 of the second current collector 220 satisfies: K n=π*[2*(n+1)T1+nT2+(2n-1)T3+n*T4+(2n-1.5)*T5]. That is, in the first layer of the winding body, K1 = π*(4*T1+T2+T3+T5 / 2). In the second layer of the winding body, K2 = π*(6T1+2T2+3T3+T4+2.5T5). By using grooves 101 of appropriate thickness, the areal capacity reduction at the corner arc section can be effectively controlled to achieve the most uniform overall electron capacity; thus avoiding problems such as lithium plating in the corner arc section of the core structure, achieving longer cycle performance and stability and safety of the structure.
[0039] Specifically, in some implementations, such as Figure 1 , 3 As shown in Figure 4, in the winding body, the number of layers n and the length M of the protrusion 201 of the nth layer are... n The relationship between the thickness T4 of the first active material layer 110, the thickness T5 of the first current collector 120, the thickness T1 of the separator 300, the thickness T3 of the second active material layer 210, and the thickness T2 of the second current collector 220 satisfies: M n =π*[(2n+1)*T1+n*T2+(n-1)*T4+2*(n-1)T5+(2n-1.5)*T3]. That is, in the first layer of the winding body, M1 = π*(3T1+T2+T3 / 2). In the second layer of the winding body, M2 = π*(5T1+2T2+T4+2T5+2.5T3). By using protrusions 201 of appropriate thickness, the areal capacity increase at the corner arc segment can be effectively controlled to achieve the most uniform overall electron capacity; thus avoiding problems such as lithium plating in the corner arc segment of the core structure, achieving longer cycle performance and ensuring the stability and safety of the structure.
[0040] Specifically, in some implementations, such as Figure 1 , 3 As shown in Figure 4, in the winding body, the number of layers n and the length K of the recess 101 in the nth layer are... n The length M of protrusion 201 n The ratio is K n / M n The relationship between the thickness T4 of the first active material layer 110, the thickness T5 of the first current collector 120, the thickness T1 of the separator 300, the thickness T3 of the second active material layer 210, and the thickness T2 of the second current collector 220 satisfies: K n / M n ≥[2(n+1)
[0041] *T1+nT2+(2n-1)*T3+nT4+(2n-1.5)*T5] / [(2n+1)*T1+nT2+(n-1)*T4+2(n-1)*T5+(2n-1.5)*T3]. That is, in the first layer of the winding body, K... n / M n ≥(4T1+T2+T3+T5 / 2) / (3T1+T2+T3 / 2). In the second layer of the winding body, K... n / M n ≥(6T1+2T2+3T3+T4+2.5T5) /
[0042] (5T1+2T2+T4+2T5+2.5T3).
[0043] This utility model also proposes a secondary battery, which includes a core structure. The specific structure of the core structure is as described in the above embodiments. Since this secondary battery adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.
[0044] A rechargeable battery, also known as a secondary battery or accumulator battery, is a battery that can be recharged after discharge to reactivate its active materials and continue to be used. Utilizing the reversibility of chemical reactions, a new battery can be constructed; that is, after a chemical reaction converts into electrical energy, the electrical energy can be used to repair the chemical system, and then the chemical reaction can be converted back into electrical energy. Therefore, it is called a secondary battery (rechargeable battery). The main types of rechargeable batteries on the market include nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid (or lead-acid) batteries, lithium-ion batteries, and polymer lithium-ion batteries.
[0045] Example 1
[0046] (1) Preparation of positive electrode
[0047] The positive electrode material lithium cobalt oxide, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 98:1.2:0.8. The mixture is then coated onto an Al foil, dried, rolled, and slit to obtain a positive electrode sheet. Recesses 101 are provided on both sides of the positive electrode sheet (the long film A side and the short film B side).
[0048] (2) Preparation of negative electrode
[0049] The negative electrode material, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in a deionized water solvent system at a mass ratio of 98.1:0.5:0.7:0.7. The mixture is then coated onto a Cu foil, dried, rolled, and slit to obtain the negative electrode sheet. Both sides of the negative electrode sheet (the long film A side and the short film B side) are provided with protrusions 201.
[0050] (3) Preparation of the separating membrane
[0051] Polyethylene (PE) porous polymer film is used as the separator.
[0052] (4) Preparation of electrolyte
[0053] A solution prepared by mixing lithium salt LiPF6 with a non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): ethylene carbonate (VC)) at a mass ratio of 25:25:15:31:4, with a mass ratio of 8:92) is used as the electrolyte for lithium batteries.
[0054] (5) Preparation of lithium-ion secondary batteries
[0055] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for safety isolation. The electrode assembly is then wound up to form the electrode assembly. The electrode assembly is placed in a packaging shell, electrolyte is injected, and the package is sealed to obtain a lithium battery.
[0056] (6) Test
[0057] The lithium plating window of the six groups of cells was tested at room temperature.
[0058] Example 2
[0059] The difference between Example 2 and Example 1 is that only the long film A surface on the positive electrode is provided with a recess 101.
[0060] Example 3
[0061] The difference between Example 3 and Example 1 is that only the short film B side on the positive electrode sheet has a recess 101.
[0062] Example 4
[0063] The difference between Example 4 and Example 1 is that only the long film A surface on the negative electrode sheet has a protrusion 201.
[0064] Example 5
[0065] The difference between Example 5 and Example 1 is that only the short film B side on the negative electrode sheet has a protrusion 201.
[0066] Comparative Example 1
[0067] The difference between Comparative Example 1 and Example 1 is that the negative electrode does not have a protrusion 201; the positive electrode does not have a depression 101.
[0068] Comparative Example 2
[0069] The difference between Comparative Example 2 and Example 1 is that: no protrusion 201 is provided on the negative electrode sheet; and recesses 101 are provided on both sides of the positive electrode sheet (long film A side and short film B side).
[0070] Comparative Example 3
[0071] The difference between Comparative Example 3 and Example 1 is that: the positive electrode does not have a recess 101; both sides of the negative electrode (the long film A side and the short film B side) are provided with protrusions 201.
[0072] Table 1 Performance parameters for all embodiments and comparative examples
[0073]
[0074] Therefore, as shown in the table above, adding at least one groove at the corner arc section of the first electrode sheet can achieve thinning treatment at that position; at the same time, adding at least one protrusion at the corner arc section of the second electrode sheet can achieve thickening treatment at that position, which can ensure the uniformity of the overall electronic capacity of the cell; thereby avoiding problems such as lithium plating in the corner arc section of the core structure, and achieving longer cycle performance as well as the stability and safety of the structure.
[0075] The present invention also proposes an electrical device, which includes a secondary battery. The specific structure of the secondary battery is as described in the above embodiments. Since the present electrical device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.
[0076] The electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose special limitations on the above-mentioned electrical equipment.
[0077] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
[0078] Based on the disclosure and teachings of the above specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, this utility model is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on this utility model are within the protection scope of this utility model. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on this utility model.
Claims
1. A core structure, characterized in that: It includes a first electrode, a second electrode, and a separator disposed between the first electrode and the second electrode; and the first electrode, the separator, and the second electrode are sequentially wound to form a wound body; the wound body has at least one corner arc segment; The first electrode has at least one groove; the second electrode has at least one protrusion; and both the groove and the protrusion are located at the corner arc segment.
2. The core structure according to claim 1, characterized in that: The first electrode includes a first current collector and a first active material layer disposed on at least one surface of the first current collector; the groove is disposed on the first active material layer; and the groove is recessed from the first active material layer toward the first current collector; The second electrode includes a second current collector and a second active material layer disposed on at least one surface of the second current collector; The protrusion is disposed on the second active material layer, and the protrusion extends from the second current collector toward the second active material layer; Furthermore, the projection of the groove toward the isolation membrane and the projection of the protrusion toward the isolation membrane are at least partially overlapped.
3. The core structure according to claim 1 or 2, characterized in that: The first electrode is the positive electrode; the second electrode is the negative electrode.
4. The core structure according to claim 2, characterized in that: The relationship between the thickness H2 of the groove and the thickness T4 of the first active material layer satisfies: H2 = (1 / 5 ~ 1 / 4) * T4.
5. The core structure according to claim 2, characterized in that: The relationship between the thickness H1 of the protrusion and the thickness T3 of the second active material layer satisfies: H1 = (1 / 4 ~ 1 / 3) * T3.
6. The core structure according to claim 2, characterized in that: In the wound body, the number of layers n and the length K of the recess 101 in the nth layer are... n The relationship between the thickness T4 of the first active material layer, the thickness T5 of the first current collector, the thickness T1 of the separator, the thickness T3 of the second active material layer, and the thickness T2 of the second current collector satisfies: K n =π*[2*(n+1)T1+nT2+(2n-1)T3+n*T4+(2n-1.5)*T5].
7. The core structure according to claim 2, characterized in that: In the wound body, the number of layers n and the length M of the protrusion in the nth layer are... n The relationship between the thickness T4 of the first active material layer, the thickness T5 of the first current collector, the thickness T1 of the separator, the thickness T3 of the second active material layer, and the thickness T2 of the second current collector satisfies: M n =π*[(2n+1)*T1+n*T2+(n-1)*T4+2*(n-1)T5+(2n-1.5)*T3].
8. The core structure according to claim 2, 6, or 7, characterized in that: In the wound body, the number of layers n and the length K of the recess in the nth layer are... n The length M of the protrusion n The ratio is K n / M n The relationship between the thickness T4 of the first active material layer, the thickness T5 of the first current collector, the thickness T1 of the separator, the thickness T3 of the second active material layer, and the thickness T2 of the second current collector satisfies: K n / M n ≥[2(n+1)*T1+nT2+(2n-1)*T3+nT4+(2n-1.5)*T5] / [(2n+1)*T1+nT2+(n-1)*T4+2(n-1)*T5+(2n-1.5)*T3].
9. A secondary battery, characterized in that: Includes the core structure as described in any one of claims 1 to 8.
10. An electrical appliance, characterized in that: Includes the secondary battery as described in claim 9.