Explosion-proof device, shell and secondary battery

Abstract

The invention provides an explosion-proof device, a shell and a secondary battery. The explosion-proof device is provided with a sheet-shaped base body. A part of one surface of the sheet-shaped base body is recessed by a certain depth to form a cavity. The cavity is defined by a bottom wall parallel to the sheet-shaped base body and a peripheral side wall connected with the bottom wall and the sheet-shaped base body. And at least one part of the peripheral side wall is thinned to form a blasting part of which the thickness is smaller than that of the bottom wall and smaller than that of the flaky base body. The blasting part is arranged on the peripheral side wall and is of a vertical structure (namely, the blasting part intersects with the plane of the sheet-shaped base body and the plane of the bottom wall), and the situation that a traditional blasting part is located in the sheet-shaped base body or the bottom wall and is parallel to the plane of the sheet-shaped base body or the bottom wall is avoided. According to the explosion-proof device, the explosion part is intersected with the plane of the sheet-shaped base body and the plane of the bottom wall instead of being parallel, so that the stress influence on the explosion part due to thermal expansion and cold contraction of the battery during charging and discharging and the internal and external pressure difference can be greatly reduced, and the service life of the explosion-proof device is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and in particular to an explosion-proof device, a shell and a secondary battery. Background Art

[0002] In modern society, more and more power tools and new energy vehicles are developing towards high capacity and high safety. Batteries are widely used in power tools and new energy vehicles due to their high capacity and other excellent characteristics. With the rapid development of electric vehicles, people not only pursue high capacity but also pay more attention to battery safety.

[0003] In order to pursue high capacity of secondary batteries, most commercial secondary batteries currently use high-voltage positive electrode materials. The use of high-voltage positive electrode materials will lead to unstable battery-electrolyte interface, and the structural instability of the positive electrode material itself will cause side reactions in the electrolyte and produce gas. Overcharging and over-discharging under high voltage will cause a large amount of gas to be generated inside the battery. At present, based on the gas production problem of secondary batteries, explosion-proof valves are installed on the batteries, especially on the top cover. When the pressure inside the battery reaches the set value of the explosion-proof valve, the explosion-proof valve explodes to release pressure to prevent the battery from exploding.

[0004] Most of the current explosion-proof valves are welded on the top cover sheet, and there are notches on the explosion-proof valve. However, when the internal air pressure of the battery is high, stress concentration will occur on the explosion-proof valve. This stress concentration acts on the notch, and the notch will rupture to release the pressure. This notch is the bursting part. During the normal use of the battery, the thermal expansion and contraction caused by charging and discharging, or the pressure from the inside to the outside and from the outside to the inside of the explosion-proof valve during the liquid injection and vacuuming process, will cause the explosion-proof valve to show up and down micro-wave movements. This action will reduce the strength of the notch of the explosion-proof valve, thereby affecting the life of the explosion-proof valve. Although, there are now reinforcement ribs on the explosion-proof valve to buffer the concentration of stress at the notch, so that the micro-wave shape of the explosion-proof valve is more uniform, thereby extending the life of the explosion-proof valve. However, the battery manufacturing process and use conditions are complex, and the external stress and internal pressure are also relatively complex. The reinforcement ribs of a single form cannot better meet the more complex battery use. Therefore, the improvement of the explosion-proof valve is still an issue that needs to be studied urgently. Summary of the invention

[0005] Based on the above problems, the present invention provides an explosion-proof device, a housing and a secondary battery. The explosion-proof device can reduce the influence of thermal expansion and contraction and pressure difference on the explosion-proof stability, thereby extending the service life of the explosion-proof device.

[0006] To achieve the above-mentioned purpose, the present invention provides an explosion-proof device on one hand, comprising a sheet-like substrate, a surface of which is partially recessed to a certain depth to form a cavity, the cavity being surrounded by a bottom wall parallel to the sheet-like substrate and a peripheral side wall connecting the bottom wall and the sheet-like substrate, at least a portion of the peripheral side wall being thinned to have a thickness less than that of the bottom wall and less than that of the bursting portion of the sheet-like substrate.

[0007] In the technical solution adopted by the present invention, the surface of the sheet substrate forms a cavity, and the peripheral side wall of the cavity forms a bursting part. Therefore, the present invention arranges the bursting part on the peripheral side wall, which is a vertical structure (i.e., it intersects with the planes of the sheet substrate and the bottom wall), rather than the traditional bursting part being inside the sheet substrate or the bottom wall and arranged parallel to the plane of the sheet substrate or the bottom wall. The bursting part in the explosion-proof device of the present invention is a vertical structure. Since it intersects with the planes of the sheet substrate and the bottom wall instead of being parallel, the stress effect on the bursting part caused by thermal expansion and contraction during battery charging and discharging and the internal and external pressure difference can be greatly reduced, thereby increasing the life of the explosion-proof device.

[0008] As a technical solution of the present invention, the lower surface of the sheet-like substrate is recessed upward to form the cavity.

[0009] As a technical solution of the present invention, the thickness of the peripheral side wall gradually decreases from the sheet-like base toward the bottom wall until it reaches a certain thickness.

[0010] As a technical solution of the present invention, the thickness of the peripheral side wall gradually decreases from the bottom wall toward the sheet-like base until it reaches a certain thickness.

[0011] As a technical solution of the present invention, a first annular groove which is recessed downward is provided on the upper surface of the sheet-like base body near the peripheral side wall, and the first annular groove surrounds the cavity.

[0012] As a technical solution of the present invention, the sum of the depth of the first annular groove and the depth of the cavity is greater than the thickness of the sheet-like substrate.

[0013] As a technical solution of the present invention, the upper surface of the sheet-like substrate is recessed downward to form the cavity.

[0014] As a technical solution of the present invention, a second annular groove recessed upward is provided on the lower surface of the sheet-like base body near the peripheral side wall, and the second annular groove surrounds the cavity.

[0015] As a technical solution of the present invention, the sum of the depth of the second annular groove and the depth of the cavity is greater than the thickness of the sheet-like substrate.

[0016] A second aspect of the present invention provides a housing, comprising a housing body and the aforementioned explosion-proof device disposed on the housing body, wherein the housing body and the explosion-proof device are an integrally formed structure or a split structure.

[0017] A third aspect of the present invention provides a secondary battery, comprising a shell, a battery cell accommodated in the shell and a top cover sealing the shell, the top cover comprising a top cover sheet, a pole and an explosion-proof device, the explosion-proof device is the aforementioned explosion-proof device, the explosion-proof device and the top cover sheet are an integrally formed structure or a split structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. 1 is a front view of a secondary battery according to an embodiment of the present invention.

[0019] Figure 2 The figure is a front view of a housing with an explosion-proof valve according to an embodiment of the present invention.

[0020] Figure 3 FIG. 1 is a top view of a housing with an explosion-proof valve according to an embodiment of the present invention.

[0021] Figure 4 The figure is a bottom view of a housing with an explosion-proof valve according to an embodiment of the present invention.

[0022] Figure 5 FIG. 4 is a cross-sectional view of a housing with an explosion-proof valve according to an embodiment of the present invention.

[0023] Figure 6 for Figure 5 A change diagram of .

[0024] Figure 7 for Figure 5 Another variation of .

[0025] Figure 8 It is a front view of a top cover according to another embodiment of the present invention.

[0026] Fig. 9 for Figure 8 Cross-sectional view along the AA direction.

[0027] Fig.10 for Figure 5 Enlarged view of the circled area.

[0028] Fig.11 for Figure 6 Enlarged view of the circled area.

[0029] Fig.12 for Fig.10 A change diagram of .

[0030] Fig.13 for Fig.10Another variation of .

[0031] Fig.14 for Fig.10 Another variation of .

[0032] Fig.15 for Figure 7 Enlarged view of the circled area.

[0033] Fig.16 for Fig.10 A dynamic picture of .

[0034] Component Symbols

[0035] 100-secondary battery; 10-shell body; 11-shell periphery; 13-shell bottom; 30-top cover; 31-first pole; 33-second pole; 35-seal; 50-explosion-proof device; 51-sheet substrate; 53-bottom wall; 55-side wall; 57-explosion part; 59a-first annular groove; 59b-second annular groove; 70-liquid injection hole; d1-depth of cavity; d2-thickness of sheet substrate; d3-thickness of bottom wall; d4-thickness of explosion part; S-cavity DETAILED DESCRIPTION

[0036] In order to better illustrate the purpose, technical solution and beneficial effects of the present invention, the present invention will be further described below in conjunction with the accompanying drawings. It should be noted that the description of the following drawings is a further explanation of the present invention and should not be used as a limitation on the scope of protection of the present invention. It should be noted that the secondary battery is usually placed vertically, and the end of the pole of the secondary battery top cover extending out and connected to the outside world is the top, that is, the top, and the other end is the bottom, that is, the bottom.

[0037] like Figures 1-2 As shown, the secondary battery 100 of the present invention includes a housing, a battery cell accommodated in the housing, and a top cover sealing the housing.

[0038] The shell includes a shell body 10 with an opening, and the shell body 10 includes a connected shell periphery 11 and a shell bottom 13. The shell periphery 11 and the shell bottom 13 can be an integrated structure, that is, formed by stretching a sheet. The shell periphery 11 and the shell bottom 13 can also be fixed by welding or bonding. The shell periphery 11 and the shell bottom 13 enclose a cavity with an opening, and the battery cell is accommodated in the cavity. The shell can be, but is not limited to, made of stainless steel, aluminum, carbon steel, magnesium alloy, etc., and it can also be made of insulating materials such as ceramics.

[0039] The battery cell may be a laminated structure or a wound structure. If wound, the battery cell includes a wound body formed by stacking a first pole piece, a separator and a second pole piece in sequence and then winding. If laminated, the battery cell is a combination of multiple laminated bodies formed by stacking a first pole piece, a separator and a second pole piece in sequence, preferably a wound structure. The battery cell may be a circular battery cell, or a flat battery cell, a square battery cell or other special-shaped structures. Of course, the shape of the shell needs to be similar to the shape of the battery cell to match it, and it may also be a circular structure, a square structure or other special-shaped structures.

[0040] The top cover and the shell can be fixed by welding, bonding or inserting after assembling the battery cell. The top cover includes a top cover sheet 30, a pole and a liquid injection hole 70. The pole includes a first pole 31 and a second pole 33. At least one of the first pole 31 and the second pole 33 is insulated from the top cover sheet 30 and sealed by a seal 35. The first pole 31 and the second pole 33 are electrically connected to the first pole piece and the second pole piece in the battery cell respectively.

[0041] The housing or the top cover of the present invention may be provided with an explosion-proof device 50. Figures 3 to 6 As shown, an explosion-proof device 50 is provided on the bottom 13 of the shell. The bottom 13 of the shell and the explosion-proof device 50 may be an integral structure or a split structure. If the bottom 13 of the shell and the explosion-proof device 50 are an integral structure, they may be formed by processes such as stamping and extrusion. If the bottom 13 of the shell and the explosion-proof device 50 are a split structure, they may be formed by welding or bonding. Preferably, the explosion-proof device 50 and the bottom 13 of the shell are an integral structure, and when preparing the shell, the shell periphery 11, the bottom 13 of the shell and the explosion-proof device 50 may be obtained by stretching the sheet material. The central axis of the explosion-proof device 50 coincides with the central axis of the shell body 10, and the explosion-proof device 50 is arranged in the exact center of the shell. If the battery cell is a wound battery cell, the explosion-proof device 50 may be placed in the center of the wound battery cell. Since there is usually a certain gap in the middle of the wound battery cell, the space utilization rate can be improved. Or as Figures 7 to 9 As shown, the top cover sheet 30 and the explosion-proof device 50 can be an integrated structure or a split structure. If the top cover sheet 30 and the explosion-proof device 50 are an integrated structure, they can be formed by stamping, extrusion and other processes. If the top cover sheet 30 and the explosion-proof device 50 are a split structure, they can be formed by welding or bonding.

[0042] like Figures 10 to 15As shown, the explosion-proof device 50 has a sheet substrate 51. The sheet substrate 51 is usually an aluminum sheet. A portion of a surface of the sheet substrate 51 is recessed to a certain depth to form a cavity S. The cavity S is surrounded by a bottom wall 53 parallel to the sheet substrate 51 and a peripheral side wall 55 connecting the bottom wall 53 and the sheet substrate 51. At least a portion of the peripheral side wall 55 is thinned to have a thickness less than the bottom wall 53 and less than the bursting portion 57 of the sheet substrate 51. That is, d4 is less than d3 and d4 is less than d2. The present invention arranges the bursting portion 57 on the peripheral side wall 55, which is a vertical structure (that is, it intersects with the planes of the sheet substrate 51 and the bottom wall 53), rather than the conventional bursting portion 57 being located inside the sheet substrate 51 or the bottom wall 53 and arranged parallel to the plane of the sheet substrate 51 or the bottom wall 53. The bursting part 57 in the explosion-proof device 50 of the present invention is a vertical structure. Since the planes of the sheet substrate 51 and the bottom wall 53 are intersecting rather than parallel, the stress effect of thermal expansion and contraction during battery charging and discharging and the internal and external pressure difference on the bursting part 57 can be greatly reduced, thereby increasing the life of the explosion-proof device 50.

[0043] Further Figures 10-12 As shown, the lower surface of the sheet substrate 51 is recessed upward to form a cavity S. Fig.10 As shown, the thickness of the peripheral side wall 55 gradually decreases from the bottom wall 53 to the sheet-like substrate 51 until it reaches a certain thickness. The gradual decrease in the thickness of the peripheral side wall 55 is conducive to relieving stress, and the thickness of the bursting portion 57 can be set according to the actual situation of the battery to meet the requirement of having a certain strength to stably burst. Fig.11 As shown, the thickness of the peripheral side wall 55 gradually decreases from the sheet substrate 51 to the bottom wall 53 until it reaches a certain thickness. Similarly, the gradual decrease in the thickness of the peripheral side wall 55 in this structure is also conducive to relieving stress, and the thickness of the bursting portion 57 can be set to a certain thickness according to the actual situation of the battery to meet the requirement of having a certain strength for stable bursting. Fig.12 As shown, the upper surface of the sheet-like base 51 is provided with a first annular groove 59a which is concave downward near the peripheral side wall 55, and the first annular groove 59a surrounds the cavity S. The first annular groove 59a thins the peripheral side wall 55 of the cavity S to form the thinnest part of the explosion-proof device 50 to form the bursting part 57. The sum of the depth of the first annular groove 59a and the depth of the cavity S is greater than the thickness of the sheet-like base 51, so as to ensure that the bursting part 57 not only has a certain strength but also can be burst in a timely and stable manner. Figures 10-12 In the structure, the peripheral side wall 55 is inclined to connect the bottom wall 53 and the sheet-like substrate 51, and the inclination angle can be 10° to 80°. The peripheral side wall 55 is inclined and the bursting part 57 is located on the wall of the peripheral side wall 55 instead of the junction of the peripheral side wall 55 and the bottom wall 53 or the junction of the peripheral side wall 55 and the sheet-like substrate 51, which is not only convenient for processing but also has a buffering effect on the air pressure, which is beneficial to pressure maintenance (such as Fig.16As shown, before the explosion, the explosion part 57 of this structure is deformed and can be maintained for a certain period of time), which is particularly suitable for lithium iron phosphate batteries that take a certain period of time to react to battery abnormalities. Before reaching the limit explosion value, the pressure can be maintained to prepare the lithium iron phosphate battery module or battery pack system for a response.

[0044] like Figures 13-14 As shown, the upper surface of the sheet substrate 51 is concave downward to form a cavity S. The lower surface of the sheet substrate 51 is provided with a second annular groove 59b that is concave upward near the peripheral side wall 55, and the second annular groove 59b surrounds the cavity S. The second annular groove 59b thins the peripheral side wall 55 of the cavity S to form the thinnest part of the explosion-proof device 50 to form the blasting part 57. The sum of the depth of the second annular groove 59b and the depth of the cavity S is greater than the thickness of the sheet substrate 51, so as to ensure that the blasting part 57 not only has a certain strength but also can blast in a timely and stable manner.

[0045] The cavity S can be Figures 10 to 14 The structure shown in FIG. 5 is formed by a bottom wall 53 and a peripheral side wall 55 on one side. Fig.15 As shown, the cavity S is surrounded by a bottom wall 53 and side walls 55 on both sides. This structure can be obtained by staggered depressions on the upper and lower surfaces of the sheet substrate 51 and forming the thinnest part on the side walls. This structure is simple, does not occupy additional space, and is convenient for subsequent battery assembly.

[0046] It should be noted that the ratio of the depth d1 of the cavity to the thickness d2 of the sheet substrate 51 is 0.5 to 4.0:1. That is, the bottom wall 53 may be completely protruded from the sheet substrate 51, or may not be protruded from the sheet substrate 51, or may be partially protruded from the sheet substrate 51. Preferably, continue as Figures 12-13 As shown, the bottom wall 53 may not protrude from the sheet substrate 51 at all, that is, one surface of the sheet substrate 51 itself is thinned to form the cavity S, and the other surface opposite is thinned to form the second annular groove 59b. This method not only does not occupy too much space inside the battery, but also the sheet substrate 5 will not be unable to be placed flat due to the protrusion of the plane. Fig.13 As shown, the peripheral side wall 55 is inclined to connect the bottom wall 53 and the sheet substrate 51, and the inclination angle can be 10° to 80°. The peripheral side wall 55 is inclined and the bursting part 57 is located on the wall of the peripheral side wall 55 rather than the junction of the peripheral side wall 55 and the bottom wall 53 or the junction of the peripheral side wall 55 and the sheet substrate 51. It is not only easy to process but also has a buffering effect on the air pressure, which is conducive to pressure maintenance. It is especially suitable for lithium iron phosphate batteries that require a certain amount of time to react to battery abnormalities. Before reaching the limit burst value, pressure can be maintained to prepare for the lithium iron phosphate battery module or battery pack system to respond. At least a portion of the peripheral side wall 55 can be thinned by extrusion, stretching, thinning, etc. In actual operation, the formation of the cavity S and the thinning process can be performed in one step at the same time.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. An explosion-proof device having a sheet-like substrate, characterized in that: A portion of a surface of the sheet-like substrate is recessed to a certain depth to form a cavity, and the cavity is surrounded by a bottom wall parallel to the sheet-like substrate and a peripheral side wall connecting the bottom wall and the sheet-like substrate, and at least a portion of the peripheral side wall is thinned to have a thickness less than the bottom wall and less than the bursting portion of the sheet-like substrate.

2. The explosion-proof device according to claim 1, characterized in that: The lower surface of the sheet-like base is recessed upward to form the cavity.

3. The explosion-proof device according to claim 2, characterized in that: The thickness of the peripheral side wall gradually decreases from the sheet-like base toward the bottom wall until it reaches a certain thickness.

4. The explosion-proof device according to claim 2, characterized in that: The thickness of the peripheral side wall gradually decreases from the bottom wall toward the sheet-like base until it reaches a certain thickness.

5. The explosion-proof device according to claim 2, characterized in that: A first annular groove which is recessed downwards is provided on the upper surface of the sheet-like base body near the peripheral side wall, and the first annular groove surrounds the cavity.

6. The explosion-proof device according to claim 5, characterized in that: The sum of the depth of the first annular groove and the depth of the cavity is greater than the thickness of the sheet-like substrate.

7. The explosion-proof device according to claim 1, characterized in that: The upper surface of the sheet-like base is recessed downward to form the cavity.

8. The explosion-proof device according to claim 7, characterized in that: A second annular groove that is recessed upward is provided on the lower surface of the sheet-like base body near the peripheral side wall, and the second annular groove surrounds the cavity.

9. The explosion-proof device according to claim 8, characterized in that: The sum of the depth of the second annular groove and the depth of the cavity is greater than the thickness of the sheet-like substrate.

10. A housing, characterized in that: The invention comprises a shell body and an explosion-proof device as claimed in any one of claims 1 to 9 arranged on the shell body, wherein the shell body and the explosion-proof device are an integrally formed structure or a split structure.

11. A secondary battery, comprising a housing, a battery cell contained in the housing, and a top cover sealing the housing, wherein the top cover comprises a top cover sheet, a pole, and an explosion-proof device, characterized in that: The explosion-proof device is the explosion-proof device according to any one of claims 1 to 9, and the explosion-proof device and the top cover sheet are an integrally formed structure or a split structure.

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