High-capacity lithium battery structure based on inner wall conductive coating and preparation method of high-capacity lithium battery structure
By coating the inner wall of the lithium battery steel casing with a conductive coating that contacts the cell surface, the problem of limited contact area at the welding point is solved, achieving a lithium battery structure with low internal resistance and high reliability. This reduces manufacturing costs and makes the battery suitable for high-power batteries and cryogenic energy storage systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-24
- Publication Date
- 2026-03-27
AI Technical Summary
In existing 21700 lithium batteries, the electrical connection between the cell and the battery steel shell relies on bottom welding, which results in a limited contact area at the welding point, easily leading to high internal resistance, complex processes, and easy damage to the battery steel shell. Furthermore, long-term use can easily cause microcracks.
The battery uses a conductive coating to cover the inner wall of the steel shell and forms a surface contact with the battery cell through an elastic contact layer, replacing the traditional bottom welding. The conductive coating is composed of composite materials, including a nickel-based alloy layer and graphene metal particle binder, and is formed by electrostatic spraying.
It achieves current path dispersion, reduces internal resistance, improves product reliability and resistance to mechanical vibration, reduces manufacturing costs, and can be extended to high-power batteries and cryogenic energy storage systems.
Smart Images
Figure CN121748655A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to high-capacity lithium battery structure development technology, belongs to lithium ion battery manufacturing technology field, and particularly relates to a high-capacity lithium battery structure based on an inner wall conductive coating and a preparation method thereof. BACKGROUND
[0002] A lithium battery includes a battery steel shell and a core, and the core is a power storage unit of the battery and is composed of a positive electrode, a negative electrode, a separator and an electrolyte. The battery steel shell is a packaging shell of the core and plays a role in protecting the internal structure. Taking a 21700 type lithium battery as an example, the battery steel shell of a common 21700 type lithium battery (also known as a high-capacity lithium battery) is a cylindrical steel shell with a diameter of about 21 mm and a height of about 70 mm, and is mainly used for packaging a 21700 type lithium battery.
[0003] In the existing 21700 lithium battery, the core and the battery steel shell are usually connected in an electrical manner by welding (such as laser welding or resistance welding) through the bottom welding point. The existing electrical connection mode between the core and the battery steel shell has the following problems: the welding point has a limited contact area (generally 9 mm in diameter), which can easily cause the current path to concentrate, the internal resistance to increase, and the high internal resistance problem to occur; the existing welding method requires precise equipment (such as a laser welding machine), and the process is relatively complex and can easily cause failure due to poor welding quality; the welding point at the bottom of the battery steel shell is easily affected by heat during the welding process, which can reduce the strength of the battery shell and cause the mechanical stress to deteriorate, and the bottom of the battery steel shell is prone to micro-cracks after long-term use. SUMMARY
[0004] The present application provides a high-capacity lithium battery structure based on an inner wall conductive coating and a preparation method thereof, which aims to overcome the technical problems that the existing electrical connection between the core and the battery steel shell relies on the bottom welding method, the welding point has a limited contact area, which can easily cause the current path to concentrate, the internal resistance to increase, and the welding process to be relatively complex, and the bottom of the battery steel shell is prone to micro-cracks after long-term use.
[0005] A high-capacity lithium battery structure based on an inner wall conductive coating includes a battery steel shell and a core, the core is arranged inside the battery steel shell, the inner wall of the battery steel shell is covered with a conductive coating, the outer side of the core is provided with a conductive elastic layer, and the core forms a surface contact with the conductive coating through the elastic contact layer.
[0006] Further, the core includes a positive electrode, a separator, a negative electrode and an elastic contact layer from inside to outside, the elastic contact layer is an expanded graphite layer or a conductive silicone layer, and the elastic contact layer is expanded under pressure after the core is wound into the battery steel shell, so that the outermost circle of the elastic contact layer forms a self-adapting and close surface contact with the conductive coating of the inner wall of the battery steel shell.
[0007] Further, the material of the conductive coating is a composite conductive material, and the thickness of the conductive coating is controlled to be 10-50 μm.
[0008] Further, the conductive coating is a double-layer structure, the bottom layer is a high-adhesion transition layer (such as a nickel-based alloy layer), and the surface layer is a high-conductivity layer formed by spraying a mixture of graphene, metal particles (such as silver-copper alloy particles) and 5% PVDF binder ethanol-based slurry on the nickel-based alloy layer on the inner surface of the steel shell body by an electrostatic spraying process and then curing at 200°C.
[0009] A preparation method of a high-capacity lithium battery structure based on an inner wall conductive coating, which comprises the following steps: 1) steel shell pretreatment, the inner surface of the battery steel shell is cleaned by plasma cleaning, the oxide layer on the inner surface of the battery steel shell is removed, and a micron-level rough surface is formed on the inner surface, the roughness Ra of the rough surface is controlled to be 1-5 μm, and the purpose is to improve the adhesion of the subsequent conductive coating; 2) coating spraying, the inner surface of the steel shell body is sprayed by an electrostatic spraying process, the composite conductive material is sprayed on the inner surface of the steel shell body, and after the spraying is completed, the inner surface is cured by hot air curing to ensure that the inner surface of the steel shell body forms a stable and firm conductive coating, the thickness of the conductive coating is controlled to be 10-50 μm, and the thickness deviation is controlled to be ±2 μm; 3) cell assembly, the elastic contact layer is coated on the outside of the cell, then the cell is wound into the battery steel shell, and a gap is ensured between the cell and the inner bottom surface of the battery steel shell, then the battery steel shell is filled with electrolyte, sealed and filled with inert gas, and the cell and the conductive coating are kept in continuous compression, thereby obtaining a high-capacity lithium battery structure.
[0010] As can be seen from the above description of the present application, compared with the prior art, the advantages of the present application are that the high-capacity lithium battery structure (such as a 21700 model lithium battery) and its preparation method are designed ideally, the low-resistance contact mode between the battery steel shell inner wall conductive coating and the cell is used instead of the traditional welding mode between the cell and the battery steel shell, the cost is reduced and the efficiency is increased, the cell forms a surface contact with the conductive coating through the elastic contact layer, the current path is dispersed, the internal resistance is small, the problem of high internal resistance is not easy to occur, the power output is high, and the use of precision equipment (such as a laser welding machine) is saved, thereby greatly reducing the manufacturing cost of the product, and the cost can be reduced by 12%. The mechanical vibration resistance of the surface contact mode is better than that of the traditional spot welding mode, and the reliability of the product is good. The high-capacity lithium battery structure can be extended to large cylindrical batteries such as 4680 and square aluminum shell batteries, especially high-power power batteries, low-temperature energy storage systems and other scenes with strict requirements for low internal resistance. BRIEF DESCRIPTION OF DRAWINGS
[0011] Figure 1 is a schematic view of the front direction of the present application.
[0012] Figure 2 is a schematic view of the front direction of the present application. Figure 1 is a partial enlarged view of A in the middle.
[0013] Figure 3 is a schematic view of the top direction of the present application.
[0014] Figure 4 is a schematic view of the front direction of the present application. Figure 3 is a partial enlarged view of B in the middle.
[0015] Figure 5 is a partial sectional view of the steel shell body in the present application.
[0016] Figure 6 is a schematic view of the product with insulating spacer in the present application. DETAILED DESCRIPTION
[0017] Example 1 Reference is made to the drawings attached to the specification Figure 1 , Figure 2 , Figure 3 and Figure 4 . A high-capacity lithium battery structure based on an inner wall conductive coating includes a battery steel shell 1 and an electric core 2, which is arranged inside the battery steel shell 1, the inner wall of the battery steel shell 1 is covered with a conductive coating 3, and the outer side of the electric core 2 is pre-provided with a conductive elastic layer 4, and the electric core 2 forms a surface contact with the conductive coating 3 through the conductive elastic layer 4. The electric core 2 includes, from inside to outside, a positive electrode 21, a diaphragm 22, a negative electrode 23, and an elastic contact layer 4, the elastic contact layer 4 is an expanded graphite layer, after the electric core 2 is rolled into the battery steel shell 1, the elastic contact layer 4 will be gradually opened under pressure, and will expand along the interlayer direction, so that the outermost circle of the elastic contact layer 4 forms a self-adaptive close surface contact with the conductive coating 3 of the inner wall of the battery steel shell 1. A gap is left between the electric core 2 and the inner bottom surface of the battery steel shell 1. In addition, the conductive elastic layer 4 can also be a conductive silicone layer.
[0018] Reference is made to the drawings attached to the specification Figure 1 , Figure 2 and Figure 5 . The material of the conductive coating 3 is a composite conductive material, and the thickness of the conductive coating 3 is controlled at 10-50 μm (the optimal diameter is 30 μm). Specifically, the conductive coating is a double-layer structure, the bottom layer is a high-adhesion transition layer 31 (such as a nickel-based alloy layer), and the surface layer is a high-conductivity layer 32, which is formed by spraying a mixture of graphene, metal particles (such as silver-copper alloy particles) and 5% PVDF binder ethanol-based slurry on the nickel-based alloy layer of the inner surface of the steel shell body through an electrostatic spraying process and curing at 200°C.
[0019] Reference is made to the accompanying drawings that form a part of this specification Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 . A method for preparing a high-capacity lithium battery structure based on an inner wall conductive coating, comprising the following steps: 1) Steel shell pretreatment, the inner surface of the battery steel shell 1 is treated by plasma cleaning (i.e. argon plasma cleaning equipment), the oxide layer on the inner surface of the battery steel shell 1 is removed, and a micron-level rough surface is formed on the inner surface, the roughness Ra of the rough surface is controlled at 1-5 μm (the optimal roughness is 3 μm), the purpose is to improve the adhesion of the subsequent conductive coating 3.
[0020] 2) Coating spraying, the inner surface of the steel shell body 1 is sprayed by electrostatic spraying process, the composite conductive material is sprayed on the inner surface of the steel shell body 1, after the spraying is completed; the inner surface is treated by hot air curing to ensure that the inner surface of the steel shell body forms a stable and firm conductive coating 3, the thickness of the conductive coating 3 is controlled at 10-50 μm, and the thickness deviation is controlled at ± 2 μm. Specifically, two electrostatic spraying processes are used for spraying, first, the inner surface of the steel shell body 1 is sprayed by electrostatic spraying process, the nickel-based alloy particle material is uniformly sprayed on the inner surface of the steel shell body 1, after the spraying is completed, the inner surface is treated by hot air curing to ensure that the inner surface of the steel shell body forms a stable and firm nickel-based alloy layer (i.e. high adhesion transition layer 31), the thickness of the high adhesion transition layer 31 is controlled at 5-15 μm (the optimal thickness is 10 μm); second, the inner surface of the steel shell body 1 is sprayed by electrostatic spraying process, the composite conductive material composed of 18-22% graphene (the optimal content is 20%), 5%-10% metal particles (such as silver-copper alloy particles) (the optimal content is 8%) and 4-6% PVDF binder (the optimal content is 5%) ethanol-based slurry is uniformly sprayed on the nickel-based alloy layer on the inner surface of the steel shell body 1, after the spraying is completed; the inner surface is treated by 200°C hot air curing to ensure that the inner surface of the steel shell body forms a stable and firm high-conductive layer 32, the thickness of the high-conductive layer 32 is controlled at 10-30 μm (the optimal thickness is 20 μm).
[0021] 3) cell assembly, the cell 2 includes from inside to outside the positive electrode 21, the diaphragm 22, the negative electrode 23 and the elastic contact layer 4, and the elastic contact layer 4 is coated on the outside of the cell; the cell 2 is rolled into the battery steel shell 1, and a gap is ensured between the cell 2 and the inner bottom surface of the battery steel shell 1, then the battery steel shell 1 is injected with electrolyte, sealed and filled with inert gas (such as nitrogen, pressure 0.1-0.3MPa), the continuous compression force between the cell 2 and the conductive coating 3 is maintained, and after the inert gas is filled, the leak detector is used to test to ensure that the battery steel shell is sealed (purpose: to prevent pressure imbalance caused by nitrogen leakage), because the elastic contact layer 4 is pressed and gradually opened, it will expand along the interlayer direction, so that the outermost circle of the elastic contact layer 4 and the conductive coating 3 of the inner wall of the battery steel shell 1 form self-adaptive close surface contact. Get a high-capacity lithium battery structure. The test results of the high-capacity lithium battery structure are as follows: the internal resistance of the high-capacity lithium battery product is reduced by 40% (relative to the traditional welding process), the capacity retention rate is increased by 15% after 500 cycles; no contact failure is found through 10G vibration test and-40~85℃ thermal shock test.
[0022] Example two The implementation of this embodiment and example one is basically the same, the difference is that: refer to the attached drawings of the specification Figure 6 A high-capacity lithium battery structure based on the inner wall conductive coating further includes an insulating spacer 5, which is placed on the inner bottom surface of the battery steel shell 1 and below the bottom of the cell 2. The insulating spacer 5 is made of PP material or PC material.
[0023] The above is only a specific embodiment of the present application, but the design concept of the present application is not limited to this, any non-essential modification of the present application using this concept should be considered as an infringement of the protection scope of the present application.
Claims
1. A high-capacity lithium battery structure based on an inner wall conductive coating, comprising a battery steel casing and a battery cell, wherein the battery cell is disposed inside the battery steel casing, characterized in that, The inner wall of the battery steel shell is covered with a conductive coating, and a conductive elastic layer is pre-placed on the outer side of the battery cell. The battery cell forms surface contact with the conductive coating through an elastic contact layer.
2. The high-capacity lithium battery structure based on an inner wall conductive coating as described in claim 1, characterized in that: The battery cell includes, from the inside out, a positive electrode, a separator, a negative electrode, and an elastic contact layer. The elastic contact layer is an expanded graphite layer or a conductive silicone layer. After the battery cell is wound into the battery steel shell, the elastic contact layer is compressed and expands, so that the outermost ring of the elastic contact layer forms an adaptive and tight surface contact with the conductive coating on the inner wall of the battery steel shell.
3. The high-capacity lithium battery structure based on an inner wall conductive coating as described in claim 1, characterized in that: The conductive coating is made of a composite conductive material, and the thickness of the conductive coating is controlled between 10-50 μm.
4. A high-capacity lithium battery structure based on an inner wall conductive coating as described in claim 3, characterized in that: The conductive coating has a double-layer structure. The bottom layer is a high-adhesion transition layer, and the top layer is a high-conductivity layer. The high-conductivity layer is formed by spraying a mixture of graphene, metal particles and 5% PVDF binder in an ethanol-based slurry onto the inner surface of the steel shell body using an electrostatic spraying process and curing it at 200°C.
5. A method for preparing a high-capacity lithium battery structure based on an inner wall conductive coating, characterized in that, It includes the following steps: 1) Steel shell pretreatment: The inner surface of the battery steel shell is cleaned using plasma cleaning to remove the oxide layer and form a micron-level rough surface. The roughness Ra of this rough surface is controlled between 1-5 μm to improve the adhesion of the subsequent conductive coating. 2) Coating spraying: The inner surface of the steel shell is sprayed using an electrostatic spraying process to apply the composite conductive material to the inner surface of the steel shell. After spraying, the inner surface is cured using hot air curing to ensure that a stable and firm conductive coating is formed on the inner surface of the steel shell. The thickness of the conductive coating is controlled between 10-50 μm, and the thickness deviation is controlled within ±2 μm. 3) Cell assembly: An elastic contact layer is coated on the outside of the cell, and then the cell is rolled into the battery steel shell, ensuring that there is a gap between the cell and the inner bottom surface of the battery steel shell. After injecting electrolyte into the battery steel shell, it is sealed and filled with inert gas to maintain continuous pressure between the cell and the conductive coating, resulting in a high-capacity lithium battery structure.