Explosion-proof valve plate having optimized bursting value and manufacturing method, and battery case and manufacturing method

Abstract

Disclosed in the present invention are an explosion-proof valve plate having an optimized bursting value and a manufacturing method, and a battery case and a manufacturing method. The manufacturing method for the explosion-proof valve plate having an optimized bursting value comprises: obtaining an explosion-proof plate blank material; forming an explosion-proof score line on the explosion-proof plate blank material; and performing high-temperature annealing treatment on the explosion-proof plate blank material, so that the hardness of the explosion-proof score line area of the explosion-proof plate blank material is decreased to 100-200 HV. In the present invention, by performing high-temperature annealing on an explosion-proof plate blank material, the hardness of an explosion-proof score line area can be decreased to 100-200 HV, so that the stress of the explosion-proof score line area can be removed, and the hardness of the explosion-proof score line area can be reduced, thereby achieving a small and stable bursting value at the explosion-proof score line and meeting users' requirement on the range of the bursting value.

Description

Explosion-proof valve piece with optimized explosion value, manufacturing method thereof, battery shell and manufacturing method thereof TECHNICAL FIELD

[0001] The present application belongs to the field of new energy batteries, and particularly relates to an explosion-proof valve piece with optimized explosion value, a manufacturing method thereof, a battery shell and a manufacturing method thereof. BACKGROUND

[0002] In recent years, new energy batteries have developed rapidly, and power battery shells and energy storage battery shells are developing in the direction of large capacity and low cost. The advantages of stainless steel battery shells, such as easy weldability, high strength and non-limited material, make up for the shortcomings of aluminum and tinplate battery shells. An explosion-proof notch is generally provided on the explosion-proof valve of a stainless steel battery shell. In order to ensure the stability of the explosion value of the explosion-proof valve made of stainless steel material, the explosion-proof notch is generally made by laser etching or stamping. However, the process of making the explosion-proof notch by laser etching is complex, the cost is high, and the stability and consistency are poor. When the explosion-proof notch is made by stamping, the material is accumulated in the area of the explosion-proof notch due to stamping, the density becomes larger and the hardness becomes harder, which leads to a larger difficulty in explosion. SUMMARY

[0003] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present application is to provide an explosion-proof valve piece with optimized explosion value, a manufacturing method thereof, a battery shell and a manufacturing method thereof.

[0004] To solve the above-mentioned technical problem, the present application provides the following technical solution:

[0005] A manufacturing method of an explosion-proof valve piece with optimized explosion value, comprising the following steps:

[0006] S100, taking an explosion-proof piece blank;

[0007] S200, forming an explosion-proof notch on the explosion-proof piece blank;

[0008] S300, performing high-temperature annealing treatment on the explosion-proof piece blank, so that the hardness of the explosion-proof notch area of the explosion-proof piece blank is reduced to 100HV-200HV.

[0009] An explosion-proof valve piece is made by the manufacturing method of the explosion-proof valve piece with optimized explosion value.

[0010] A manufacturing method of a battery shell, comprising the following steps:

[0011] S910, forming an explosion-proof valve piece by using the manufacturing method of the explosion-proof valve piece with optimized explosion value according to any one of the above-mentioned manufacturing methods;

[0012] S920, taking a shell body with a pressure relief hole, the shape and size of the pressure relief hole being adapted to the shape and size of the outer contour of the explosion-proof valve piece;

[0013] S930, taking a reinforcing ring, the outer contour size of the reinforcing ring is greater than the outer contour size of the explosion-proof valve piece, and the inner contour size of the reinforcing ring is smaller than the outer contour size of the explosion-proof valve piece;

[0014] S940, fixing the explosion-proof valve piece in the pressure relief hole by the welding clamp, and fixing the reinforcing ring directly below the joint of the explosion-proof valve piece and the pressure relief hole;

[0015] S950, welding the explosion-proof valve piece in the pressure relief hole, and welding the inner side area of the reinforcing ring with the welding platform of the explosion-proof valve piece, and welding the outer side area of the reinforcing ring with the shell around the pressure relief hole.

[0016] A battery shell is made by the method of making a battery shell according to any one of the preceding.

[0017] In the present application, the explosion-proof notch is formed by stamping process, which is more stable, has better consistency, and has simple process, less process and low manufacturing cost. By high temperature annealing of the explosion-proof piece blank, the stress and hardness of the explosion-proof notch area are reduced by high temperature annealing to realize smaller and more stable blasting value to meet the customer's blasting value range requirement. The 3D printing vacuum heat treatment furnace can be automatically controlled by computer program during the whole annealing process, and the power is stable, which effectively solves the problems of unstable explosion-proof valve blasting value and large overall blasting value of the stainless steel explosion-proof valve piece. By selecting a reasonable residual thickness value of the explosion-proof notch, the tearing pressure value of the explosion-proof notch can be stabilized at about 1.2MPa. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The schematic embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation on the present application. In the drawings:

[0019] Fig. 1 is a flow chart of an embodiment of the method for making an explosion-proof valve piece with optimized blasting value according to the present application.

[0020] Fig. 2 is a schematic structural view of the explosion-proof piece blank after forming the explosion-proof notch thereon.

[0021] Fig. 3 is a top view of Fig. 2.

[0022] Fig. 4 is a sectional view of Fig. 3 along A-A direction.

[0023] Fig. 5 is an enlarged view of B in Fig. 4.

[0024] Fig. 6 is a schematic structural view of the explosion-proof valve piece.

[0025] Fig. 7 is a top view of Fig. 6.

[0026] Fig. 8 is a C-C sectional view of Fig. 7.

[0027] Fig. 9 is a grain size distribution map of the anti-explosion score area of a sample of anti-explosion valve sheet at 500 times magnification.

[0028] Fig. 10 is a grain size distribution map of the anti-explosion score area of another sample of anti-explosion valve sheet at 1000 times magnification.

[0029] Fig. 11 is a flow chart of an embodiment of the method for manufacturing battery shell.

[0030] Fig. 12 is an exploded view of the battery shell.

[0031] Fig. 13 is a sectional view of the reinforcing ring before welding.

[0032] The reference signs in the description are as follows: anti-explosion valve sheet - 100; score groove - 110; arc convex part - 111; annular recess - 112; welding platform - 120; reinforcing ring - 130; anti-explosion score - 200; first semicircular score - 211; second semicircular score - 212; first straight line segment score - 221; second straight line segment score - 222; shell - 300; narrow side - 310; pressure relief hole - 311; wide side - 320; opening - 330; top cover - 400; bottom cover - 500; gap - 600. DETAILED DESCRIPTION

[0033] The embodiments of the present application will be described below through specific concrete examples. The drawings provided in the following examples only schematically illustrate the basic concept of the present application, and the following examples and features in the examples can be combined with each other without conflict.

[0034] Example 1

[0035] Referring to Fig. 1, Fig. 1 is a flow chart of an embodiment of the method for manufacturing anti-explosion valve sheet with optimized burst value. The method for manufacturing anti-explosion valve sheet with optimized burst value in the embodiment includes the following steps:

[0036] S100, take an anti-explosion sheet blank. In the embodiment, the anti-explosion sheet blank is a stainless steel sheet. The stainless steel sheet has the advantages of easy weldability, high strength, and less material limitation, which fills the shortcomings of aluminum and tinplate materials.

[0037] S200, please refer to Figure 2, on the anti-explosion sheet blank is formed anti-explosion score 200. In this embodiment, the anti-explosion score 200 is formed on the anti-explosion sheet blank by stamping process. Of course, the score groove 110 can be first formed on the anti-explosion sheet blank by stamping process, and then the anti-explosion score 200 is formed in the score groove 110 by stamping process, which can be arranged adjacent to the outer edge of the groove bottom of the score groove 110. After stamping, the anti-explosion score 200 area is caused by stamping material accumulation, density becomes larger, hardness becomes hard, at this time, the hardness of the anti-explosion score 200 area of the anti-explosion sheet blank is generally 300HV-400HV, which leads to a larger blasting value, thereby affecting the stability of blasting.

[0038] Please refer to Figure 3, in this embodiment, the anti-explosion score 200 is runway-shaped, including symmetrically arranged first semicircular score 211 and second semicircular score 212 and first straight line segment score 221 connecting the first end of the first semicircular score 211 and the first end of the second semicircular score 212 and second straight line segment score 222 connecting the second end of the first semicircular score 211 and the second end of the second semicircular score 212. Of course, the anti-explosion score 200 can also adopt other shapes such as elliptical shape.

[0039] Please refer to Figure 4 and Figure 5, in this embodiment, the cross-sectional shape of the anti-explosion score 200 is trapezoidal; of course, in other embodiments, the cross-sectional shape of the anti-explosion score 200 can also be "V" or "U" or other shapes. The value of the lower base width of the cross section of the anti-explosion score 200 is in the range of 0-0.5mm. When the cross-sectional shape of the anti-explosion score 200 is trapezoidal, the angle a between the waist of the trapezoidal and the vertical direction (i.e. the height of the trapezoidal) and the value of the lower base width W1 of the trapezoidal will also have a certain influence on the tearing pressure value of the anti-explosion structure. The value of the angle a between the waist of the trapezoidal and the height of the trapezoidal is in the range of 5°-60°, preferably 25°≤a≤45°, and the value of the lower base width W of the trapezoidal is preferably 0.03mm≤W≤0.08mm.

[0040] Please continue to refer to FIG. 4 and FIG. 5, the tear gas pressure value at the explosion-proof notch 200 is mainly affected by the residual thickness value d1 of the explosion-proof notch 200; the residual thickness value of the explosion-proof notch 200 is defined as the thickness of the explosion-proof sheet blank remaining after being thinned at the explosion-proof notch 200. By selecting a suitable residual thickness value d1, the range of the tear gas pressure of the explosion-proof notch 200 can be limited. If the residual thickness value d1 of the explosion-proof notch 200 is small, the strength of the enclosed area of the explosion-proof notch 200 will be greatly reduced, and when the explosion-proof valve sheet 100 collides with other products during movement, it is extremely likely to cause the explosion-proof notch 200 to break, causing external gas to enter the battery through the broken opening of the explosion-proof valve sheet 100 and react with the material of the battery cell, thereby causing the battery to fail, and even possibly causing a battery explosion accident. If the value of t is large, when the internal gas pressure of the battery reaches the upper limit pressure, the pressure relief opening formed by tearing at the explosion-proof notch 200 will be smaller, so that the gas in the battery cannot be discharged in time, which may also cause the battery to over-expand and cause an explosion. In the embodiment, the residual thickness value of the explosion-proof notch 200 is 0.03mm-0.05mm.

[0041] When selecting the residual thickness value d1 of the explosion-proof notch 200, the influence of the thickness of the explosion-proof sheet blank also needs to be considered. In the embodiment, the thickness of the explosion-proof sheet blank is 0.15mm-0.3mm.

[0042] S300, the explosion-proof sheet blank is subjected to high-temperature annealing treatment to remove stress, so that the hardness of the explosion-proof notch 200 area of the explosion-proof sheet blank is reduced to 100HV-200HV, thereby obtaining the explosion-proof valve sheet 100. The high-temperature annealing process can reduce the stress and hardness of the explosion-proof notch 200 area of the explosion-proof valve sheet 100, thereby realizing a smaller and more stable burst value to meet the burst value requirements of the battery shell.

[0043] In this step, the annealing treatment of the explosion-proof sheet blank can include the following sub-steps:

[0044] S311, the explosion-proof sheet blank is placed in a vacuum furnace, and the vacuum furnace is subjected to vacuumizing. In the embodiment, the vacuum furnace uses a 3D printing vacuum heat treatment furnace, and the vacuumizing time is 40min-50min. After vacuumizing, the vacuum degree in the vacuum furnace is less than 0.1pa. In the embodiment, after vacuumizing for 40min-50min, the vacuum degree in the vacuum furnace is about 0.05pa.

[0045] Compared with the annealing of the previous aluminum material, the annealing of the stainless steel material explosion-proof valve sheet 100 requires higher temperature and longer time, and the whole annealing process requires higher temperature control and a cycle of nearly 17 hours, which is difficult to control. In this embodiment, a 3D printing vacuum heat treatment furnace is used, and the whole annealing process can be fully automatically controlled by a computer program, and the power is stable. It is an effective solution to solve the problem of unstable explosion-proof valve burst value of the stainless steel explosion-proof valve sheet 100, and the overall large burst value. It can make the tear pressure value of the explosion-proof notch 200 stable at about 1.2MPa.

[0046] S312, the temperature in the vacuum furnace is uniformly raised to 900-1300℃, in this embodiment, the temperature in the vacuum furnace is raised at a rate of 3-4℃ / min, and the final temperature in the vacuum furnace after heating is 1100℃.

[0047] S313, the temperature in the vacuum furnace is kept at 1100℃ for a predetermined time. In this step, the temperature in the vacuum furnace is kept at 1100℃ for 2 hours.

[0048] S314, the temperature in the vacuum furnace is naturally lowered to 200-300℃. In this step, the vacuum furnace does not need to be intervened.

[0049] S315, the vacuum furnace is filled with argon to quickly lower the temperature in the vacuum furnace to 70-90℃. By filling argon for about 2 hours, the temperature in the vacuum furnace can be lowered to 70-90℃.

[0050] S316, the explosion-proof sheet blank is taken out of the vacuum furnace, which is the finished product of the explosion-proof valve sheet.

[0051] As shown in Table 1, the comparison table of burst value test data of three types of explosion-proof valve sheet monomers without annealing treatment, explosion-proof valve sheet monomers after annealing treatment, and explosion-proof valve sheet monomers after annealing treatment welded on the battery cell.

[0052] Table 1

[0053] From the test data in Table 1, it can be seen that through high-temperature annealing treatment, the burst value of the explosion-proof valve sheet monomer is greatly reduced, and the reduction is more than 50%, and the burst value of the explosion-proof valve sheet 100 welded on the battery cell after high-temperature annealing treatment is about 1.2MPa, which meets the customer's requirements.

[0054] In the embodiment, the stamping process is used to form the explosion-proof score 200 on the explosion-proof sheet blank, the explosion-proof score 200 is more stable and has better consistency, the process is simple, the process is less, and the manufacturing cost is low. By annealing the explosion-proof sheet blank after stamping, the hardness of the explosion-proof score 200 region can be reduced from 300HV-400HV to 100HV-200HV, so that the stress of the explosion-proof score 200 region can be removed, and the hardness of the explosion-proof score 200 region can be adjusted.

[0055] The 3D printing vacuum heat treatment furnace can be automatically controlled by a computer program during the entire annealing process of about 17 hours, and the power is stable, which can effectively solve the problems of unstable explosion valve burst value and large overall burst value of the stainless steel explosion valve sheet, and can stabilize the tearing gas pressure value of the explosion-proof score 200 at about 1.2MPa.

[0056] In addition, the explosion-proof score 200 needs to reach a stable burst value of about 1.2MPa, in addition to ensuring the hardness of the explosion-proof score 200 region, the explosion-proof score 200 also needs to have a stable residual thickness value. In the embodiment, when the residual thickness value of the explosion-proof score 200 is 0.03mm-0.05mm, the CPK (Complex Process Capability index) reaches 1.33, which meets the requirements.

[0057] Embodiment 2

[0058] The embodiment is further improved on the basis of embodiment 1, and the explosion-proof valve sheet manufacturing method of the embodiment includes the following steps:

[0059] S100', take a 316L stainless steel sheet, the wall thickness of the stainless steel sheet is generally 0.15mm-0.20mm. In the embodiment, the wall thickness of the stainless steel sheet is preferably 0.18mm±0.005mm. It is found through many tests that different materials of the stainless steel sheet have a relatively obvious influence on the stability of the burst value of the explosion-proof valve sheet 100 after annealing treatment. After comparing many stainless steel materials, it is finally found that the explosion-proof valve sheet 100 made of 316L stainless steel material has the best stability of the burst value after annealing treatment.

[0060] S200', forming an explosion-proof score 200 on the explosion-proof sheet blank. The shape and cross-sectional shape of the explosion-proof score 200 can be the same as that of embodiment 1. This step can include the following sub-steps:

[0061] S210, please refer to FIG. 6 to FIG. 8, by stamping the middle part of the stainless steel sheet is concave to form a notch groove 110, while the middle part of the notch groove 110 is upward arch to form an arc-shaped convex part 111, so that the annular recess 112 is formed between the side wall of the notch groove 110 and the arc-shaped convex part 111. The area of the outer periphery of the notch groove 110 which is not concave downward forms a welding platform 120, which is used for welding the valve body and the battery shell.

[0062] The shape of the profile line of the notch groove 110 is preferably oval or track-shaped, so as to facilitate stamping. On this basis, the shape of the stainless steel sheet can also be preferably oval or track-shaped, of course, the shape of the stainless steel sheet can also be other shapes.

[0063] By forming an arc-shaped convex part 111 in the middle of the notch groove 110, the stress generated by the deformation of the stainless steel sheet during the stamping of the notch groove 110 can be released, so that the material consistency of the notch groove 110 area is better. The top end of the arc-shaped convex part 111 is generally lower than or flush with the plane of the welding platform 120, so as to avoid the arc-shaped convex part 111 being higher than the plane of the welding platform 120, which makes the battery need to occupy more installation space.

[0064] S220, please continue to refer to FIG. 6 to FIG. 8, by stamping to form an explosion-proof notch 200 at the bottom of the annular recess 112 of the stainless steel sheet, to obtain an explosion-proof valve sheet 100. The cross section of the explosion-proof notch 200 is a trapezoidal shape with a narrow bottom and a wide top, and the notch residual thickness of the explosion-proof notch 200 is generally 0.03mm-0.05mm, preferably 0.04mm. The notch residual thickness represents the remaining thickness of the stainless steel sheet at the explosion-proof notch 200.

[0065] In order to improve the stability of the burst value, high-precision stamping equipment with a precision greater than or equal to 2μm and high-precision stamping dies with a precision greater than or equal to 2μm are used in this step, so that the error of the notch residual thickness of the explosion-proof notch 200 is less than or equal to 2μm. Of course, the S210 step and the S220 step generally use the same stamping equipment.

[0066] The explosion-proof notch 200 is formed by stamping, which is more efficient than the laser etching method. However, after stamping, the material in the explosion-proof notch area is accumulated due to stamping, resulting in increased density and hardness. In addition, stress is also generated during the stamping of the notch groove 110, and the superposition of the two will cause the burst value of the explosion-proof notch to be larger, and will seriously affect the stability of the burst value. Therefore, it is necessary to find a way to reduce the influence of stress and improve the stability of the burst value.

[0067] S300', the anti-explosion valve sheet 100 is treated by adopting an annealing process. The anti-explosion valve sheet 100 is treated by adopting the annealing process, so that stress is removed, the hardness of the anti-explosion valve sheet 100 in the anti-explosion score area is reduced, the stress of the anti-explosion valve sheet 100 in the anti-explosion score area is reduced, a smaller and more stable blasting value is achieved, and the requirement of the blasting value of the battery shell is met. In this step, the method of treating the anti-explosion valve sheet 100 by adopting the annealing process can include the following sub-steps:

[0068] S321, the anti-explosion valve sheet 100 is placed in a vacuum furnace, and the vacuum furnace is vacuumized. The time of vacuumizing is about 45 min, and after vacuumizing, the vacuum degree of the vacuum furnace ranges from 0.001 pa to 0.1 pa, and in this embodiment, 0.005 pa is preferred.

[0069] S322, the temperature in the vacuum furnace is uniformly raised to 1000-1100℃, for example, it can be raised to 1000℃, 1050℃ or 1100℃.

[0070] S323, the vacuum furnace is kept for 60-120 min, for example, it can be kept for 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min.

[0071] S324, the anti-explosion valve sheet 100 is cooled to 300-500℃ with the furnace; for example, it can be cooled to 300℃, 350℃, 400℃, 450℃ or 500℃ with the furnace. In this step, the vacuum furnace does not need to be intervened.

[0072] S325, the vacuum furnace is filled with argon, so that the temperature in the vacuum furnace is rapidly reduced to 130-170℃; in this embodiment, the time of filling argon is about 150 min, so that the temperature in the vacuum furnace is rapidly reduced to about 150℃.

[0073] S326, the anti-explosion valve sheet 100 is taken out of the vacuum furnace, and the annealing treatment of the anti-explosion valve sheet 100 is ended.

[0074] Please refer to Table 2 for the false battery blasting test data of the anti-explosion valve sheet 100 adopting different stainless steel materials.

[0075] Table 2

[0076] A battery head manufacturer in China requires that the burst value of the battery shell is: the mean data (average value) of the burst value is not greater than 1.5 MPa, and the sigma data (standard deviation) is not greater than 0.05 MPa. According to the above table, the mean data of the burst value of Qianye's SUS304 material exceeds the upper limit of the standard, and although the sigma data is within the standard range, the overall index does not meet the standard requirements. The mean data of the burst value of Qianye's SUS304 tempering material exceeds the upper limit of the standard, and the sigma data is large, which do not meet the standard requirements. The mean data of the burst value of Rida's SUS304 material is very close to the upper limit of the standard, and the difference between the upper limit of the standard is within the error range, and the sigma data is large, which do not meet the standard requirements. Although the mean data of the burst value of Rida's SUS305 material is within the standard range, the sigma data is large, and the overall index does not meet the standard requirements. The mean data of the burst value of Rikong's SUS305 material exceeds the upper limit of the standard, although the sigma data is within the standard range, the overall index does not meet the standard requirements. The burst value of Qianye's SUS316L material is small, the mean data of the burst value completely meets the requirements, and the sigma data is stable at about 0.03, the mean value and the sigma data of the burst value meet the standard range, and there is a large margin between the upper limit of the standard, the mean data and the sigma data of the above other types of materials have obvious advantages, therefore, the SUS316L material is finally locked as the material for improving the burst stability of the explosion-proof valve piece 100 in this embodiment.

[0077] In this embodiment, by adopting special process parameters for annealing treatment of the explosion-proof valve piece 100, and forming an arc-shaped convex part 111 in the middle of the notch groove 110 to release stress, the crystal structure of the explosion-proof valve piece 100 in the explosion-proof notch 200 area can be changed, the grain size distribution is uniform, thereby reducing the stress and hardness of the explosion-proof valve piece 100 in the explosion-proof notch 200 area, and also reducing the fluctuation of the burst pressure of the explosion-proof valve piece 100. In addition, combined with the selection of the material of the explosion-proof valve piece 100, and improving the precision of the notch residual thickness of the explosion-proof notch 200, the explosion-proof valve piece 100 finally reaches a small and stable burst value. Please refer to FIG. 9 and FIG. 10, which are the grain size distribution diagrams of the explosion-proof notch 200 area of two explosion-proof valve piece 100 samples under 500 times and 1000 times magnification after being treated by the annealing process of this embodiment.

[0078] The application also discloses an explosion-proof valve piece with optimized burst value, which is made by the explosion-proof valve piece manufacturing method with optimized burst value according to any one of the above embodiments. The explosion-proof valve piece made by the above method not only has a lower burst value under the same parameters, but also has a more stable burst value, which can meet the requirements of battery manufacturers for burst value stability at the present stage.

[0079] Referring to FIG. 11, which is a flow chart of an embodiment of the method for manufacturing a battery shell according to the present application. The method for manufacturing a battery shell according to the present application comprises the following steps:

[0080] S910, the rupture disc 100 is manufactured by using the method for manufacturing a rupture disc with optimized burst value according to any of the above embodiments.

[0081] S920, referring to FIG. 12, a shell 300 with a pressure relief hole 311 is taken, the shape and size of the pressure relief hole 311 are adapted to the shape and size of the outer contour of the rupture disc 100. In the present embodiment, the shell 300 comprises a rectangular cylinder, a top cover 400 and a bottom cover 500 arranged at two openings 330 of the rectangular cylinder respectively, the rectangular cylinder comprises two wide sides 320 and two narrow sides 310, and the pressure relief hole 311 is arranged on one of the narrow sides 310.

[0082] S930, a reinforcing ring 130 is taken, the outer contour size of the reinforcing ring 130 is greater than the outer contour size of the rupture disc 100, and the inner contour size of the reinforcing ring 130 is smaller than the outer contour size of the rupture disc 100, so as to connect the rupture disc 100 and the shell 300. The reinforcing ring 130 is generally made of stainless steel ring with a thickness of 0.5mm-1mm, and in the present embodiment, the thickness of the reinforcing ring 130 is preferably 0.8mm. By arranging the reinforcing ring 130, not only the welding strength between the rupture disc 100 and the shell 300 can be increased, but also the gap 600 between the rupture disc 100 and the pressure relief hole 311 can be closed, so as to avoid that the welding slag generated in the welding process of the rupture disc 100 falls into the shell 300 from the gap 600 between the rupture disc 100 and the pressure relief hole 311.

[0083] S940, referring to FIG. 13, the rupture disc 100 is fixed in the pressure relief hole 311 by a welding clamp, and the reinforcing ring 130 is fixed right below the connection between the rupture disc 100 and the pressure relief hole 311.

[0084] S950, the explosion-proof valve sheet 100 is welded in the pressure relief hole 311, and the inner side area of the reinforcing ring 130 is welded and fixed with the welding platform 120 of the explosion-proof valve sheet, and the outer side area of the reinforcing ring 130 is welded and fixed with the shell 300 around the pressure relief hole 311. In this step, the fiber laser welding machine can be used for welding in a nitrogen environment, the welding speed is 80±20 mm / s, the LD power (i.e. semiconductor power) is 450 W±20 W, and the FIB power (i.e. fiber power) is 170 W±20 W; the LD power and the FIB power are used to control the width and depth of welding respectively. The nitrogen gas injection pressure is 0.1 MPa±0.05 MPa, and the nitrogen gas is injected into the welding area at the above-mentioned pressure, so that a protective gas environment can be formed in the welding area.

[0085] Of course, after the explosion-proof valve sheet 100 and the reinforcing ring 130 are welded and fixed at the pressure relief hole 311 of the rectangular cylinder, the top cover 400 and the bottom cover 500 also need to be welded and fixed at the two openings 330 of the rectangular cylinder respectively, so as to obtain the battery shell. The welding method of the top cover 400 and the bottom cover 500 is the prior art, which is not described here. In addition, the top cover 400 is also provided with electrodes, liquid injection holes and other structures, which are all prior art and are not related to the improvement points of the present application, so they are not shown in the figure.

[0086] The application also discloses a battery shell made by the method of any one of the above embodiments. The battery shell made by the method has lower burst value and better burst stability, can avoid the problem that the welding position of the explosion-proof valve sheet is first broken by high pressure before the explosion-proof notch is broken, can also avoid the problem that the welding slag falls into the shell 300 from the gap 600 between the explosion-proof valve sheet 100 and the pressure relief hole 311, and can improve the safety and stability of the battery.

[0087] The above embodiments only express the preferred embodiments of the application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the application, which are all within the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A method of making an explosion pressure optimized rupture disc, comprising: The method comprises the following steps: S100, taking a blank of explosion-proof sheet; S200, forming an explosion-proof notch on the blank of explosion-proof sheet; S300, performing high-temperature annealing treatment on the blank of explosion-proof sheet, so that the hardness of the explosion-proof notch area of the blank of explosion-proof sheet is reduced to 100HV-200HV.

2. The method of claim 1, wherein: the predetermined value is a burst pressure of the valve sheet; and the predetermined value is optimized by the step of: The blank of explosion-proof sheet is a stainless steel sheet. ​ 3. The method for manufacturing an explosion-proof valve plate with optimized burst value as described in claim 1, characterized in that: In the S200 step, the explosion-proof notch is formed on the blank of explosion-proof sheet by stamping process.

4. The method of claim 1, wherein: The cross-sectional shape of the explosion-proof notch is trapezoidal, "U" shaped or "V" shaped, and the residual thickness value of the explosion-proof notch is 0.03mm-0.05mm.

5. The method of claim 1, wherein: the predetermined value is a burst pressure of the valve sheet; and the predetermined value is optimized by the step of: In the S200 step, a notch groove is first formed on the blank of explosion-proof sheet by stamping process, and then the explosion-proof notch is formed in the notch groove by stamping process. ​ 6. A method of making an explosion pressure optimized rupture disc according to claim 1 wherein, The explosion-proof notch is in the shape of a runway and comprises symmetrically arranged first and second semicircular notches and two straight line segment widening notches connecting the corresponding end points of the first and second semicircular notches.

7. A method of manufacturing an explosion pressure optimized explosion valve sheet according to any one of claims 1 to 6, characterized in that, In the S300 step, the high-temperature annealing treatment on the blank of explosion-proof sheet comprises the following sub-steps: S311, placing the blank of explosion-proof sheet into a vacuum furnace and performing vacuumizing on the vacuum furnace; S312, uniformly raising the temperature in the vacuum furnace to 900-1300℃; S313, keeping the temperature for a predetermined time; S314, naturally lowering the temperature in the vacuum furnace to 200-300℃; S315, filling argon in the vacuum furnace to rapidly lower the temperature in the vacuum furnace to 70-90℃; S316, taking out the blank of explosion-proof sheet from the vacuum furnace.

8. The method for manufacturing an explosion-proof valve plate with optimized burst value as described in claim 7, characterized in that: In the S310 step, the vacuum furnace is a 3D printing vacuum heat treatment furnace; the vacuumizing time is 40-50min, and the vacuum degree in the vacuum furnace after vacuumizing is less than 0.1pa; in the S320 step, the temperature raising rate is 3-4℃ / min, and in the S330 step, the temperature keeping time is 2 hours.

9. A method of making an explosion pressure optimized rupture disc according to any one of claims 2 to 6, wherein, The S200 step comprises the following sub-steps: S210, by stamping, the middle part of the stainless steel sheet is depressed downward to form a notch groove, at the same time, the middle part of the notch groove is arched upward to form an arc-shaped protrusion, so that an annular recess is formed between the sidewall of the notch groove and the arc-shaped protrusion, and the area of the periphery of the notch groove which is not depressed downward forms a welding platform; S220, by stamping, an explosion-proof notch is formed at the bottom of the annular recess of the stainless steel sheet to obtain an explosion-proof valve sheet.

10. A method of making an explosion pressure optimized rupture disc according to claim 9, wherein, The stainless steel sheet is made of 316L stainless steel sheet.

11. A method of making an explosion pressure optimized rupture disc according to claim 9, wherein, In the S220 step, a high-precision stamping equipment with a precision greater than or equal to 2μm and a high-precision stamping die with a precision greater than or equal to 2μm are used.

12. A method of making an explosion pressure optimized rupture disc according to claim 9, wherein, In the S300 step, the annealing process for treating the explosion-proof valve sheet comprises the following sub-steps: S321, placing the explosion-proof valve sheet into a vacuum furnace and performing vacuumizing on the vacuum furnace; S322, uniformly raising the temperature in the vacuum furnace to 1000-1100℃; S323, keeping the temperature for 60-120min; S324, cooling the explosion-proof valve sheet to 300-500℃ along with the furnace; S325, filling argon into the vacuum furnace to rapidly decrease the temperature in the vacuum furnace to 130-170℃; S326, taking out the explosion-proof valve plate from the vacuum furnace.

13. The method for manufacturing an explosion-proof valve plate with optimized burst value as described in claim 9, characterized in that: The profile line of the score groove is in the shape of an ellipse or a racetrack; and / or The top end of the arc-shaped convex part is lower than or flush with the plane where the welding platform is located.

14. An explosion pressure optimized explosion valve plate, characterized by: The explosion-proof valve plate is made by the method of claim 1-13.

15. A method of making a battery case, comprising: The method comprises the following steps: The method comprises the following steps: S920, taking a shell with a pressure relief hole, the shape and size of the pressure relief hole being adapted to the shape and size of the outer contour of the explosion-proof valve plate; S930, taking a reinforcing ring, the outer contour size of the reinforcing ring being greater than the outer contour size of the explosion-proof valve plate, and the inner contour size of the reinforcing ring being smaller than the outer contour size of the explosion-proof valve plate; S940, fixing the explosion-proof valve plate in the pressure relief hole by the welding fixture, and fixing the reinforcing ring right below the joint of the explosion-proof valve plate and the pressure relief hole; S950, welding the explosion-proof valve plate in the pressure relief hole, and welding and fixing the inner side area of the reinforcing ring with the welding platform of the explosion-proof valve plate, and welding and fixing the outer side area of the reinforcing ring with the shell around the pressure relief hole.

16. The method of claim 15, wherein: In the step S950, the welding is performed in a nitrogen environment by using a fiber laser welding machine, the welding speed is 80±20mm / s, the LD power is 450W±20W, and the FIB power is 170W±20W.

17. The method of claim 15, wherein: The reinforcing ring is a stainless steel ring with a thickness of 0.5-1mm.

18. The method of claim 15, wherein: The shell comprises a rectangular cylinder, a top cover and a bottom cover arranged at two openings of the rectangular cylinder respectively, the rectangular cylinder comprises two wide sides and two narrow sides, the pressure relief hole is arranged on the narrow side, and in the step S500, the explosion-proof valve plate and the reinforcing ring are welded and fixed at the pressure relief hole of the rectangular cylinder, and then the top cover and the bottom cover are welded and fixed at the two openings of the rectangular cylinder respectively.

19. A battery housing, characterized by The battery shell is made by the method of claim 15-18.

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