Lithium ion battery and assembly method thereof

Abstract

The present invention relates to the technical field of new energy vehicles and lithium-ion batteries, and discloses a lithium-ion battery and an assembly method thereof. The lithium-ion battery of the present invention comprises a housing, a winding core, a positive electrode cover plate, and a negative electrode cover plate. A fixing plate is provided at one end of the housing, and a through-hole is provided at the center of the fixing plate. The positive electrode cover plate is arranged at an opening at one end of the housing where the fixing plate is provided. The winding core is arranged within the housing, and a center hole is provided on the winding core. The positive electrode current collector of the winding core is welded to a side of the fixing plate away from the positive electrode cover plate. The negative electrode cover plate is arranged at an opening at one end of the housing away from the fixing plate. A negative electrode post is provided at the center of the negative electrode cover plate. A guide plate is provided on one end of the negative electrode post disposed within the housing. One side of the guide plate is welded to the negative electrode post, and the other side of the guide plate is welded to the negative electrode current collector of the winding core. The battery does not require foldable conductive connectors, thereby reducing the difficulty of battery assembly and the risk of short circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles and lithium-ion batteries, and in particular to a lithium-ion battery and an assembling method thereof. Background Art

[0002] Lithium-ion batteries are secondary batteries (rechargeable batteries) that rely primarily on the movement of lithium ions between positive and negative electrodes to function and are widely used in various workplaces. Cylindrical lithium-ion batteries, due to their structural advantages such as ease of manufacture, have become a popular power source for plug-in hybrid and pure electric new energy vehicles. Cylindrical lithium-ion batteries are also a common battery structure in the energy storage market, such as for home energy storage, RV energy storage, and large-scale industrial energy storage.

[0003] Traditional lithium-ion batteries, such as the 18650 and 21700 sizes, often use a single tab to connect the core and battery electrodes. Because tabs are typically thin, elongated conductors, they are a major negative factor affecting battery internal resistance and heat generation. With increasing energy density and output power requirements for new energy vehicles, large cylindrical lithium-ion batteries are becoming the trend. This also means the tabs must withstand higher currents and release more heat, becoming a key factor affecting battery safety. Additionally, lithium-ion battery cores with "tab-less" or "full-tab" structures have emerged, often with covers (or "collector plates") at each end. Because some battery cell casings are cylindrical with open ends, with positive and negative covers at each end, the corresponding electrodes need to be connected to the collector plates at each end of the core via conductive connectors. To accommodate the distance tolerance between the collector plates and the electrodes, the conductive connectors are typically folded, occupying a significant amount of space within the cell casing, limiting the core volume and battery energy density. The installation of the positive and negative electrode covers requires folding the conductive connector, which is a cumbersome operation. Furthermore, the folding and assembly of the conductive connector connecting the negative electrode can easily touch the shell wall and the battery cell, causing a short circuit and affecting battery safety. Therefore, it is necessary to improve the structure of cylindrical lithium-ion batteries. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a lithium-ion battery that does not require foldable conductive connectors, thereby reducing the difficulty of battery assembly and the risk of short circuit.

[0005] To achieve the above objectives, the lithium-ion battery of the present invention includes a housing, a winding core, a positive electrode cover plate, and a negative electrode cover plate. The housing is a cylindrical tube with openings at both ends. A fixing plate is provided at one end of the housing. The fixing plate is disposed within the housing near the corresponding end opening. The periphery of the fixing plate is conductively and fixedly connected to the inner wall of the cylindrical tube. A through hole is provided at the center of the fixing plate.

[0006] The positive electrode cover plate is arranged at the opening of the housing where one end of the fixing plate is provided, and the positive electrode cover plate is welded to the periphery of the corresponding opening of the housing;

[0007] The winding core is arranged in the shell, and a central hole is provided on the winding core. The central hole passes through the current collecting disks of the two poles of the winding core, and the current collecting disk of the positive electrode of the winding core is welded to a side of the fixing plate away from the positive electrode cover plate;

[0008] The negative electrode cover is arranged at the opening of the shell away from one end of the fixed plate, and the negative electrode cover is welded to the periphery of the corresponding opening of the shell. A negative electrode post is provided at the center of the negative electrode cover, and the negative electrode post is insulated from the negative electrode cover. One end of the negative electrode post is arranged in the shell, and the other end of the negative electrode post passes through the negative electrode cover and is arranged outside the shell. A guide plate is provided on the end of the negative electrode post arranged in the shell, one side of the guide plate is welded to the negative electrode post, and the other side of the guide plate is welded to the current collecting disk of the negative electrode of the winding core.

[0009] In one embodiment, the guide plate is made of elastic metal conductive material.

[0010] In one embodiment, a mounting hole is provided at the center of the negative electrode cover plate, and the mounting hole passes through the negative electrode cover plate; the negative electrode column includes a negative electrode pressure plate and a conductive rivet, the negative electrode pressure plate is arranged on the outside of the negative electrode cover plate, an insulating member is provided between the negative electrode pressure plate and the negative electrode cover plate, an insulating seal is provided on the inner side of the negative electrode cover plate, and the insulating seal passes through the mounting hole and is connected to the insulating member; the conductive rivet passes through the insulating seal, the mounting hole and the insulating member in sequence and is riveted to the negative electrode pressure plate, one side of the guide plate is welded to the conductive rivet, and the other side of the guide plate is welded to the current collecting disk of the negative electrode of the winding core.

[0011] In one embodiment, a boss is provided on one side of the insulating seal close to the negative electrode cover plate, the boss passes through the mounting hole and is inserted into the insulating member, the conductive rivet passes through the side of the insulating seal away from the negative electrode cover plate, and the end face of one end of the boss inserted into the insulating member is connected to the negative electrode pressure plate.

[0012] In one embodiment, the end of the boss inserted into the insulating member is interference fit with the insulating member and the mounting hole, and the conductive rivet is interference fit with the insulating seal.

[0013] In one embodiment, a first protrusion is provided on a side of the guide plate close to the conductive rivet, and the first protrusion is welded to the conductive rivet. A second protrusion is provided on a side of the guide plate away from the conductive rivet, and the second protrusion is welded to the current collecting disk of the negative electrode of the core.

[0014] In one embodiment, a side of the fixing plate facing away from the positive electrode cover plate is provided with an annular groove and a plurality of recessed portions. The annular groove is concentrically arranged with the fixing plate and is arranged at the connection between the fixing plate and the shell. The recessed portions are arranged in the area enclosed by the annular groove and are spaced around the center of the fixing plate.

[0015] In one embodiment, a gap is provided between two adjacent surfaces of the positive electrode cover plate and the fixed plate, the positive electrode cover plate is provided with an injection hole and a sealing cover capable of closing the injection hole, and the recessed portion is provided through the fixed plate.

[0016] The lithium-ion battery in the above embodiment has at least the following advantages:

[0017] (1) The positive electrode cover is connected to the positive electrode collector of the core through the shell and the fixed plate, and the negative electrode column is connected to the negative electrode collector of the core through the guide plate. The entire structure avoids the use of folding conductive connectors, reducing the difficulty of battery assembly and the risk of short circuit. Through the through hole at the center of the fixed plate and the center hole on the core, the guide plate can be welded to the negative electrode collector first and then to the negative electrode column; at the same time, the fixed plate and the guide plate are directly welded to the collector of the core, which can better fix the position of the core in the shell. At the same time, it can also simplify its assembly process, reduce the space occupied by the throttling structure in the battery shell, and improve the energy density of the battery.

[0018] (2) The guide plate is made of elastic metal conductive material to facilitate the connection between the guide plate and the core negative electrode collector plate, the negative electrode column and the conductive rivet. The guide plate can produce a certain deformation to adapt to the distance error between the conductive rivet and the core negative electrode collector plate. The conductive rivet and the insulating seal, and the boss of the insulating seal and the mounting hole are simultaneously interference fit. After the conductive rivet is installed, the interference fit between the insulating seal and the mounting hole is increased, which can reduce the difficulty of installing the insulating seal while ensuring the interference fit.

[0019] (3) The first protrusion, the second protrusion, the annular groove, and the recessed portion create a gap between the winding core and the guide plate and the fixed plate, which facilitates welding and the flow of electrolyte after injection. A gap is provided between the positive electrode cover plate and the fixed plate to facilitate electrolyte injection.

[0020] With respect to the lithium-ion battery in the above embodiment, the present invention further provides a method for assembling a lithium-ion battery. The method for assembling a lithium-ion battery of the present invention comprises the following steps:

[0021] S1: Fix the fixing plate to one end of the shell by welding or integral molding, then insert the winding core from the other end of the shell, and connect the fixing plate and the current collector of the core positive electrode by laser spot welding;

[0022] S2: Install the guide plate into the shell and fix the guide plate to the negative electrode collector plate of the winding core by laser spot welding;

[0023] S3: Install the negative electrode post on the negative electrode cover, install the negative electrode cover on the end of the shell away from the fixed plate, and use resistance welding to connect the guide plate and the negative electrode post through the center hole on the winding core;

[0024] S4: Install the positive electrode cover and inject the electrolyte, and connect the positive electrode cover to the shell by welding.

[0025] Furthermore, step S3 also includes the following steps: firstly welding the negative electrode cover plate to the shell, and then using the upper and lower electrodes of a resistance welding machine to clamp the guide plate and the negative electrode column for welding.

[0026] The lithium-ion battery assembly method in the above embodiment has at least the following advantages:

[0027] (1) The positive and negative electrode covers do not need to be welded separately. The fixed plate and the current collector of the positive electrode of the core are welded first, and then the guide plate and the negative electrode current collector of the core are welded. This makes it easier to control the tight contact between the fixed plate and the guide plate and the corresponding current collector, ensuring the welding quality. The guide plate and the negative electrode column are welded by resistance welding, so that the guide plate and the negative electrode column are tightly contacted during the welding process, avoiding empty welds. The battery assembly process is simplified, which is conducive to improving production efficiency.

[0028] (2) First weld the negative electrode cover to the shell, and then weld the guide plate and the negative electrode column to facilitate the welding of the negative electrode cover and reduce the impact of the negative electrode cover on the welding of the guide plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly introduces the drawings required for use in the specific embodiments. In all the drawings, each element or part is not necessarily drawn according to the actual scale.

[0030] Figure 1 A front cross-sectional view of a lithium-ion battery provided in one embodiment of the present invention;

[0031] Figure 2 for Figure 1 A magnified view of the lithium-ion battery shown;

[0032] Figure 3 for Figure 1 B is an enlarged view of the lithium-ion battery shown;

[0033] Figure 4 for Figure 1 A schematic diagram of the three-dimensional structure of the shell shown;

[0034] Figure 5 for Figure 1 A schematic diagram of the three-dimensional structure of the guide plate shown;

[0035] Reference numerals:

[0036] 1-shell, 11-fixing plate, 111-through hole, 112-annular groove, 113-recessed portion, 2-positive electrode cover, 21-liquid injection hole, 22-sealing cover, 3-negative electrode cover, 31-mounting hole, 32-negative electrode column, 321-negative electrode pressure plate, 322-conductive rivet, 33-insulating member, 34-insulating sealing member, 341-boss, 4-winding core, 41-center hole, 5-guide plate, 51-first protrusion, 52-second protrusion, 53-liquid hole. DETAILED DESCRIPTION

[0037] The following embodiments of the technical solution of the present invention are described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only examples and are not intended to limit the scope of protection of the present invention. It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0038] In the description of this application, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In the description of the present invention, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined. Unless otherwise clearly stipulated and defined, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0039] See also Figures 1 to 5 In one embodiment, a lithium-ion battery includes a shell 1, a positive electrode cover plate 2, a negative electrode cover plate 3 and a winding core 4, which does not require folded conductive connectors, reducing the difficulty of battery assembly and the risk of short circuit.

[0040] For details, please refer to Figures 1 to 3 , the shell 1 is a cylindrical tube with openings at both ends. A fixing plate 11 is provided at one end of the shell 1, and the fixing plate 11 is arranged in the shell 1 near the corresponding end opening. The periphery of the fixing plate 11 is conductively fixedly connected to the inner wall of the cylindrical tube. A through hole 111 is provided at the center of the fixing plate 11. The positive electrode cover plate 2 is arranged at the opening of the end of the shell 1 where the fixing plate 11 is provided. The positive electrode cover plate 2 is welded to the periphery of the corresponding opening of the shell 1. The positive electrode cover plate 2 and the shell 1 constitute the positive terminal structure of the battery. The fixing plate 11 can be integrally formed with the shell 1 or be arranged in the shell 1 by welding or other means.

[0041] The core 4 is arranged in the shell 1. A center hole 41 is provided on the core 4, and the center hole 41 passes through the current collecting disks of the two poles of the core 4. The current collecting disk of the positive pole of the core 4 is welded to the side of the fixed plate 11 away from the positive cover plate 2. The core 4 is the battery core, which is formed by curling the positive electrode sheet, the negative electrode sheet and the diaphragm. Current collecting disks corresponding to the positive and negative poles are provided at both ends of the core 4. The so-called current collecting disk is a current collector structure of a battery core structure such as a pole-free ear or a pole-weighted ear, and reference can be made to the prior art. The center hole 41 is formed by curling or by setting a center tube in the center of the core 4. The center hole 41 is coaxially arranged with the through hole 111. Please refer to Figure 4 Specifically, an annular groove 112 and a plurality of recessed portions 113 are provided on the side of the fixed plate 11 facing away from the positive electrode cover plate 2. The annular groove 112 is concentrically arranged with the fixed plate 11 and is arranged at the connection between the fixed plate 11 and the shell 1. The recessed portions 113 are arranged in the area enclosed by the annular groove 112 and are spaced around the center of the fixed plate 11. The current collecting disk of the positive electrode of the winding core 4 is welded to the spaced area between the annular groove 112 and the recessed portions 113. It has a simple structure and a large conductive area and can withstand a large current. A gap is formed between the recessed portion 113 and the annular groove 112 and the positive electrode current collecting disk of the winding core 4 to facilitate the flow of electrolyte. In one embodiment, a gap is provided between the two adjacent surfaces of the positive electrode cover plate 2 and the fixed plate 11. The positive electrode cover plate 2 is provided with an injection hole 21 and a sealing cover 22 that can close the injection hole 21. The recessed portion 113 is provided through the fixed plate 11. The injection hole 21 is used to inject battery electrolyte, and the recessed portion 113 passes through the fixing plate 11 to facilitate the electrolyte to flow into the winding core 4. Specifically, the recessed portions 113 are evenly spaced around the through hole 111. In one embodiment, the recessed portions 113 are fan-shaped or fan-shaped.

[0042] The negative electrode cover plate 3 is arranged at the opening of the shell 1 away from the fixed plate 11. The negative electrode cover plate 3 is welded to the periphery of the corresponding opening of the shell 1. A negative electrode post 32 is provided at the center of the negative electrode cover plate 3, and the negative electrode post 32 is insulated from the negative electrode cover plate 3. One end of the negative electrode post 32 is provided in the shell 1, and the other end of the negative electrode post 32 passes through the negative electrode cover plate 3 and is provided outside the shell 1. A guide plate 5 is provided on the end of the negative electrode post 32 provided in the shell 1. One side of the guide plate 5 is welded to the negative electrode post 32, and the other side of the guide plate 5 is welded to the negative electrode collector disk of the winding core 4. The positive electrode cover plate 2 is connected to the positive electrode collector disk of the winding core 4 through the shell 1 and the fixed plate 11, and the negative electrode post 32 is connected to the negative electrode collector disk of the winding core 4 through the guide plate 5. The use of folded conductive connectors is avoided in the entire structure, reducing the difficulty of battery assembly and the risk of short circuit. Through the through hole 111 at the center of the fixing plate 11 and the center hole 41 on the winding core 4, the guide plate 5 can be first welded to the negative electrode current collecting disk and then welded to the negative electrode pole 32; at the same time, the fixing plate 11 and the guide plate 5 are directly welded to the current collecting disk of the winding core 4, and the position fixing effect of the winding core 4 in the shell 1 is better; at the same time, it can also simplify its assembly process, reduce the space occupied by the current collecting structure in the battery cell shell 1, and improve the battery energy density.

[0043] In one embodiment, a mounting hole 31 is provided at the center of the negative electrode cover plate 3. The mounting hole 31 passes through the negative electrode cover plate 3. The negative electrode post 32 includes a negative electrode pressure plate 321 and a conductive rivet 322. The negative electrode pressure plate 321 is arranged on the outside of the negative electrode cover plate 3, and an insulating member 33 is provided between the negative electrode pressure plate 321 and the negative electrode cover plate 3. An insulating seal 34 is provided on the inside of the negative electrode cover plate 3, and the insulating seal 34 passes through the mounting hole 31 and is connected to the insulating member 33. The conductive rivet 322 passes through the insulating seal 34, the mounting hole 31, and the insulating member 33 in sequence and is riveted to the negative electrode pressure plate 321. One side of the guide plate 5 is welded to the conductive rivet 322, and the other side of the guide plate 5 is welded to the current collecting disk of the negative electrode of the winding core 4. Specifically, a boss 341 is provided on the side of the insulating seal 34 close to the negative electrode cover plate 3. The boss 341 passes through the mounting hole 31 and is inserted into the insulating member 33. The conductive rivet 322 extends through the side of the insulating seal 34 facing away from the negative electrode cover 3 and connects to the negative electrode pressure plate 321 along with the end of the boss 341 inserted into the insulating member 33. In one embodiment, the end of the boss 341 inserted into the insulating member 33 forms an interference fit with the insulating member 33 and the mounting hole 31, and the conductive rivet 322 also forms an interference fit with the insulating seal 34. After installation, the conductive rivet 322 increases the interference fit between the insulating seal 34 and the mounting hole 31, and also between the insulating seal 34 and the insulating member 33, thereby reducing the difficulty of installing the insulating seal 34 while ensuring the required interference fit.

[0044] Please also refer to Figure 5In one embodiment, a first protrusion 51 is provided on one side of the guide plate 5 close to the conductive rivet 322, and the first protrusion 51 is welded to the conductive rivet 322. A second protrusion 52 is provided on the side of the guide plate 5 away from the conductive rivet 322, and the second protrusion 52 is welded to the current collecting plate of the negative pole of the winding core 4. The first protrusion 51, the second protrusion 52, the annular groove 112 and the recessed portion 113 form a gap between the winding core 4 and the local area of the guide plate 5 and the fixed plate 11, which is convenient for welding and the flow of electrolyte after injection. Furthermore, the guide plate 5 is also provided with a liquid hole 53, which is arranged at intervals corresponding to each second protrusion 52 and passes through the guide plate 5. The liquid hole 53 facilitates the flow of electrolyte at the negative end of the winding core and the discharge of air, thereby facilitating the injection of electrolyte.

[0045] In one embodiment, the guide plate 5 is made of an elastic conductive metal material. Specifically, the elastic conductive metal material is a copper sheet, a nickel sheet, or a copper-nickel-plated sheet. The guide plate 5 can deform to accommodate the distance error between the negative electrode post 32 and the negative current collector of the winding core 4, thereby facilitating connection between the guide plate 5, the negative electrode post 32, and the negative current collector of the winding core.

[0046] With respect to the lithium-ion battery in the above embodiment, the present invention further provides a method for assembling a lithium-ion battery. In one embodiment, the method for assembling a lithium-ion battery includes the following steps:

[0047] S1: Secure the fixing plate 11 to one end of the housing 1 by welding or integral molding. Then, insert the winding core 4 from the other end of the housing 1 and connect the fixing plate 11 to the positive electrode current collector of the winding core 4 using laser spot welding. Specifically, multiple welding points are performed between the positive electrode current collector of the winding core 4 and the fixing plate 11 to ensure a stable connection between the corresponding current collectors and the fixing plate 11, increase the contact and conduction area, and reduce the internal resistance of the battery.

[0048] S2: Install the guide plate 5 into the housing 1 and secure it to the negative electrode current collector disc of the winding core 4 using laser spot welding. Specifically, the guide plate 5 and the negative electrode current collector disc of the winding core 4 are welded at multiple points. The spot welds are located around the center hole 41. This increases the contact and conduction area between the guide plate 5 and the negative electrode current collector disc of the winding core 4, thereby reducing the internal resistance of the battery.

[0049] S3: Install the negative electrode post 32 onto the negative electrode cover 3. Install the negative electrode cover 3 onto the end of the housing 1 away from the fixing plate 11. Connect the guide plate 5 and the negative electrode post 32 using resistance welding through the center hole 41 on the winding core 4. Specifically, first weld the negative electrode cover 3 to the housing 1. Then, use the upper and lower electrodes of the resistance welding machine to clamp the guide plate 5 and the negative electrode post 32 for welding. During the welding process, due to the use of resistance welding, the resistance welding machine can clamp the guide plate 5 and the negative electrode post 32 during welding, ensuring a firm weld and stable conduction.

[0050] S4, installing the positive electrode cover plate 2 and injecting the electrolyte, and connecting the positive electrode cover plate 2 to the housing 1 by welding.

[0051] According to the lithium-ion battery assembly method described in the above embodiment, the positive and negative electrode cover plates 2 and 3 do not need to be welded separately. The fixing plate 11 and the positive electrode current collector of the winding core 4 are welded first, followed by the guide plate 5 and the negative electrode current collector of the winding core 4. This facilitates the close contact between the fixing plate 11 and the guide plate 5 and the corresponding current collector, ensuring weld quality. The guide plate 5 and the negative electrode post 32 are then welded using resistance welding, ensuring a close contact during the welding process and preventing weld holes. This simplifies the battery assembly process and improves production efficiency.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A lithium-ion battery comprising a housing, a winding core, a positive electrode cover plate, and a negative electrode cover plate, characterized in that: The housing is a cylindrical tube with openings at both ends. A fixing plate is provided at one end of the housing. The fixing plate is disposed within the housing near the corresponding opening. The periphery of the fixing plate is electrically and fixedly connected to the inner wall of the cylindrical tube. A through hole is provided at the center of the fixing plate. The positive electrode cover plate is arranged at the opening of the housing where one end of the fixing plate is provided, and the positive electrode cover plate is welded to the periphery of the corresponding opening of the housing; The winding core is arranged in the shell, and a central hole is provided on the winding core. The central hole passes through the current collecting disks of the two poles of the winding core, and the current collecting disk of the positive electrode of the winding core is welded to a side of the fixing plate away from the positive electrode cover plate; The negative electrode cover is arranged at an opening of the housing away from one end of the fixing plate, the negative electrode cover is welded to the periphery of the corresponding opening of the housing, a negative electrode post is provided at the center of the negative electrode cover, the negative electrode post is insulated from the negative electrode cover, one end of the negative electrode post is provided inside the housing, the other end of the negative electrode post passes through the negative electrode cover and is provided outside the housing, and a guide plate is provided on the end of the negative electrode post provided inside the housing; The guide plate is made of elastic metal conductive material; The negative electrode column includes a negative electrode pressure plate and a conductive rivet, one side of the guide plate is welded to the conductive rivet, and the other side of the guide plate is welded to the current collecting plate of the negative electrode of the winding core; A first protrusion is provided on a side of the guide plate close to the conductive rivet, and the first protrusion is welded to the conductive rivet. A second protrusion is provided on a side of the guide plate away from the conductive rivet, and the second protrusion is welded to the current collecting plate of the negative electrode of the winding core. An annular groove and a plurality of recessed portions are provided on one side of the fixing plate facing away from the positive electrode cover plate. The annular groove is concentrically arranged with the fixing plate and is provided at the connection between the fixing plate and the shell. The recessed portions are provided in the area enclosed by the annular groove and are spaced around the center of the fixing plate.

2. The lithium-ion battery according to claim 1, wherein A mounting hole is provided at the center of the negative electrode cover plate, and the mounting hole passes through the negative electrode cover plate; the negative electrode pressure plate is arranged on the outside of the negative electrode cover plate, and an insulating member is provided between the negative electrode pressure plate and the negative electrode cover plate, and an insulating seal is provided on the inner side of the negative electrode cover plate, and the insulating seal passes through the mounting hole and is connected to the insulating member; the conductive rivet passes through the insulating seal, the mounting hole and the insulating member in sequence and is riveted to the negative electrode pressure plate.

3. The lithium-ion battery according to claim 2, wherein The insulating seal is provided with a boss on one side close to the negative electrode cover plate, and the boss passes through the mounting hole and is inserted into the insulating member. The conductive rivet passes through the side of the insulating seal away from the negative electrode cover plate, and the end face of one end of the boss inserted into the insulating member is connected to the negative electrode pressure plate.

4. The lithium-ion battery according to claim 3, characterized in that One end of the boss inserted into the insulating member is interference-fitted with the insulating member and the mounting hole, and the conductive rivet is interference-fitted with the insulating seal.

5. The lithium-ion battery according to claim 1, wherein A gap is provided between the two adjacent surfaces of the positive electrode cover plate and the fixing plate. The positive electrode cover plate is provided with a liquid injection hole and a sealing cover capable of closing the liquid injection hole. The recessed portion is provided through the fixing plate.

6. A method for assembling a lithium-ion battery, for assembling the lithium-ion battery according to any one of claims 1 to 5, characterized in that: The steps include: S1: Fix the fixing plate to one end of the shell by welding or integral molding, then insert the winding core from the other end of the shell, and connect the fixing plate and the current collector of the core positive electrode by laser spot welding; S2: Install the guide plate into the shell and fix the guide plate to the negative electrode collector plate of the winding core by laser spot welding; S3: Install the negative electrode post on the negative electrode cover, install the negative electrode cover on the end of the shell away from the fixed plate, and use resistance welding to connect the guide plate and the negative electrode post through the center hole on the winding core; S4: Install the positive electrode cover and inject the electrolyte, and connect the positive electrode cover to the shell by welding.

7. The method for assembling a lithium-ion battery according to claim 6, wherein: Step S3 also The method comprises the following steps: firstly welding the negative electrode cover plate to the shell, and then using the upper and lower electrodes of a resistance welding machine to clamp the guide plate and the negative electrode column for welding.

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