A battery case stretch forming die

Abstract

The application discloses a battery shell stretch forming die, which comprises a punch and a stretch die, the stretch die comprises an upper die and a lower die, the upper die is provided with an upper stretch cavity, the upper die is provided with a die inlet at the upper part of the upper stretch cavity, the die inlet is provided with an inlet R angle, the inner diameter of the upper stretch cavity decreases from top to bottom, the lower die is provided with a lower stretch cavity, the inner diameter of the lower stretch cavity decreases from top to bottom, and the inner diameter of the lower end port of the upper stretch cavity is larger than that of the upper end port of the lower stretch cavity. The battery shell punched by the application has 3-4 grades of improved rust resistance, longer service life and higher safety performance.

Description

Technical Field

[0001] This invention relates to the field of stretching die technology, and more particularly to a stretching die for a battery casing. Background Technology

[0002] A lithium-ion battery is a rechargeable battery that primarily functions by the movement of lithium ions between the positive and negative electrodes. During charging and discharging, Li+ ions repeatedly insert and extract between the two electrodes: during charging, Li+ ions extract from the positive electrode, pass through the electrolyte, and insert into the negative electrode, leaving the negative electrode in a lithium-rich state; the reverse occurs during discharging. Due to their small size, light weight, high capacity, and environmental friendliness, lithium-ion batteries are widely used in industrial production and daily life.

[0003] The battery casing is an important component of lithium-ion batteries. Currently, lithium-ion battery casings on the market use methods such as... Figure 1 The battery casing is produced using the stretch forming die shown. However, because the stretching cavity in this die is a straight section and the radius (R) at the entrance is small (typically 0.5mm-1.0mm), the workpiece changes from coarse to thin during stretching. All material deformation and sliding occur at the point of the entrance R. Since the R is an arc, the workpiece can only contact the tangent point. In other words, the dimensions are already fixed once the workpiece enters the R, and stretching is complete. The subsequent working sections only serve to maintain and fix the dimensions. Throughout the process, the contact between the workpiece and the stretching die is a circular line contact from a circumferential perspective. The interaction time and area between the workpiece and the stretching die are short, resulting in a large degree of instantaneous material deformation. Therefore, battery casings produced using this stretch forming die have poor surface finish, resulting in a matte surface. Consequently, their corrosion resistance is poor, and their service life is short. Once the battery casing develops holes due to corrosion, leakage will occur, potentially rendering the battery unusable or even causing combustion and explosion. Therefore, a solution is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a stretch forming mold for battery casings, thereby solving the problems of poor rust resistance and short service life of existing battery casings.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A stretch forming die for a battery casing includes a punch and a stretching die. The stretching die includes an upper die and a lower die. The upper die has an upper stretching cavity, and a die inlet is provided on the upper part of the upper stretching cavity. An inlet radius (R-angle) is provided at the die inlet. The inner diameter of the upper stretching cavity decreases sequentially from top to bottom. The lower die has a lower stretching cavity, and the inner diameter of the lower stretching cavity decreases sequentially from top to bottom. The inner diameter of the lower end port of the upper stretching cavity is larger than the inner diameter of the upper end port of the lower stretching cavity.

[0007] As a preferred embodiment of the present invention, the inlet radius (R-angle) is 3mm.

[0008] As a preferred embodiment of the present invention, a guide opening is provided on the upper die at the upper part of the die inlet, and the diameter of the guide opening decreases from top to bottom.

[0009] As a preferred embodiment of the present invention, a blanking port is provided on the lower part of the lower drawing cavity on the lower die, and the diameter of the blanking port increases sequentially from top to bottom.

[0010] As a preferred embodiment of the present invention, the upper die is provided with a discharge port located at the lower part of the upper stretching cavity, and the diameter of the discharge port increases sequentially from top to bottom.

[0011] As a preferred embodiment of the present invention, the lower die is provided with a feed port located at the upper part of the lower stretching cavity, and the diameter of the feed port decreases sequentially from top to bottom.

[0012] In this application, the drawing die employs two dies: an upper die and a lower die. Both the upper and lower dies have conical working sections, with a dimensional difference of 0.02mm-0.04mm between the upper and lower openings of each section. This ensures that the workpiece's transition from coarse to fine is completed segment by segment within the drawing die during the drawing process, rather than instantaneously. This prolongs the material deformation time and slows down the deformation, thus reducing springback and fixing the dimensions. Simultaneously, this application increases the radius (R) at the entrance, making the workpiece enter the cavity more smoothly and easily. Furthermore, due to the segmented conical drawing, the material deformation is no longer concentrated at a single point on the entrance radius but is distributed across the entire contact surface of the two working sections. This increases the contact area between the workpiece and the drawing die, changing from line contact to surface contact, and prolonging the interaction time between the workpiece and the drawing die. Under the extrusion pressure, the material surface is continuously flattened and smoothed, resulting in a near-mirror-like glossy surface.

[0013] The beneficial effects of this invention are that the battery casing made using this application has a rust resistance that is improved by 3-4 levels, resulting in a longer battery life and higher safety performance. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of a traditional battery casing stretch forming die;

[0015] Figure 2 This is a schematic diagram of the structure of a stretch forming die for a battery casing;

[0016] Figure 3 This is a schematic diagram of the upper die.

[0017] Figure 4 This is a schematic diagram of the lower die structure. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0019] Please refer to Figures 2 to 4 As shown, Figure 2 This is a schematic diagram of the structure of a stretch forming die for a battery casing; Figure 3 This is a schematic diagram of the upper die. Figure 4 This is a schematic diagram of the lower die structure.

[0020] In this embodiment, a stretching die for a battery casing includes a punch 1 and a stretching die. The stretching die includes an upper die 2 and a lower die 3. The upper die 2 has an upper stretching cavity 21, and a die inlet 22 is provided on the upper die 2 at the upper part of the upper stretching cavity 21. The die inlet 22 has an inlet radius (R-angle) of 3mm. A guide opening 23 is provided on the upper die 2 at the upper part of the die inlet 22. The diameter of the guide opening 23 decreases from top to bottom. The inner diameter of the upper stretching cavity 21 decreases from top to bottom. A discharge port is provided at the lower part of the upper stretching cavity 21, and the diameter of the discharge port increases sequentially from top to bottom. A lower stretching cavity 31 is opened on the lower die 3, and the inner diameter of the lower stretching cavity 31 decreases sequentially from top to bottom. A blanking port 32 is provided on the lower die 3 at the lower part of the lower stretching cavity 31, and the diameter of the blanking port 32 increases sequentially from top to bottom. A feed port is provided on the lower die 3 at the upper part of the lower stretching cavity 31, and the diameter of the feed port decreases sequentially from top to bottom. The inner diameter of the lower end port of the upper stretching cavity 21 is larger than the inner diameter of the upper end port of the lower stretching cavity 31.

[0021] The battery casings stamped using this application have a good surface finish. The table below compares the surface roughness of glossy battery casings stamped using this application and matte battery casings stamped using traditional molds:

[0022]

[0023] As shown in the table above, the battery casing formed using this application has a better surface finish. From a microscopic perspective, the difference between its contour peaks and valleys is small, the surface unevenness is not serious, and corrosive media are not easily adsorbed and accumulated. Therefore, its rust prevention ability is higher.

[0024] To further verify the above conclusions, corrosion tests were conducted on both glossy and matte battery casings. The coating thickness was the same for both types of casings, and the results are shown in the table below:

[0025] Experimental Project Glossy battery case Matte battery case High temperature and high humidity test for 7 days No response Rust spots appeared Soak in 5% saline solution at 20℃ for 30 minutes No response Rust spots appeared Salt spray test for 2 hours ≥8 levels Level 4-5

[0026] As can be seen from the test data in the table above, the rust resistance of the battery casing formed using this application can be improved by 3-4 levels.

[0027] The above embodiments merely illustrate the basic principles and characteristics of the present invention. The present invention is not limited to the above embodiments. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A stretch forming die for a battery case comprising a punch and a stretch die, characterized by: The stretching die includes an upper die and a lower die. The working sections of both the upper die and the lower die are conical. The upper die has an upper stretching cavity, and a die inlet is provided on the upper die at the upper part of the upper stretching cavity. An inlet radius (R-angle) is provided at the die inlet. The inner diameter of the upper stretching cavity decreases from top to bottom. The lower die has a lower stretching cavity, and the inner diameter of the lower stretching cavity decreases from top to bottom. The inner diameter of the lower end port of the upper stretching cavity is larger than the inner diameter of the upper end port of the lower stretching cavity. The lower die is provided with a blanking port located at the lower part of the lower stretching cavity, and the diameter of the blanking port increases sequentially from top to bottom; The upper die has a discharge port located at the lower part of the upper stretching cavity, and the diameter of the discharge port increases sequentially from top to bottom.

2. The stretch forming die for a battery case according to claim 1, wherein: The inlet radius (R-angle) is 3mm.

3. The stretch forming die for a battery case according to claim 1, wherein: The upper die has a guide opening located above the die inlet, and the diameter of the guide opening decreases sequentially from top to bottom.

4. The stretch forming die for a battery casing according to claim 1, characterized in that: The lower die has a feed port located at the upper part of the lower stretching cavity, and the diameter of the feed port decreases from top to bottom.

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