Top cover having integrally formed explosion-proof valve, battery casing, and processing method therefor

Abstract

A top cover having an integrally formed explosion-proof valve (11), comprising: a top cover main body (10); an explosion-proof valve (11) integrally formed with the top cover main body (10); the top cover main body (10) comprises an outer surface (101) and an inner surface (102) opposite the outer surface (101); the explosion-proof valve (11) comprises a valve main body (111) and a safety groove (112); the valve main body (111) comprises a recessed portion (103) extending toward the inner surface (102) of the top cover main body (10), a lower edge of the recessed portion (103) contracts inwardly and forms a protruding portion (104) extending toward the outer surface (101) of the top cover main body (10), and the safety groove (112) is provided on a top surface of the protruding portion (104). A battery casing (20) having the integrally formed explosion-proof valve (11), and a processing method for the top cover and the battery casing (20). The method comprises locally heating the safety groove (112) region to improve the microstructure thereof, so as to lower and stabilize the rupture pressure value.

Description

Top cover with integrally formed explosion valve, battery case and method of processing thereof TECHNICAL FIELD

[0001] The present invention belongs to the technical field of secondary batteries, and particularly relates to a top cover with an integrally formed explosion valve, a battery case and a processing method thereof. BACKGROUND

[0002] The main functions of the explosion valve of a secondary battery are: 1. When abnormal conditions such as thermal runaway occur inside the battery, the internal pressure of the cell rapidly increases, and the explosion valve can be opened in time and relieve the pressure when the whole cell uncontrollably expands or even explodes, thereby reducing the consequences of accidents such as fire and explosion of the battery and ensuring personal and property safety; 2. The explosion valve of the cell can compensate for the internal pressure changes of the cell caused by charging and discharging and other working processes to some extent, thereby prolonging the service life of the battery. Therefore, the explosion valve plays a very important role in the safe operation of the cell.

[0003] Most of the top cover sheets of the prior art secondary batteries are explosion valve split structure, that is, a special aluminum material explosion valve is welded on the punched top cover sheet. This method requires a separate device and process to prepare the explosion valve, which is relatively high in cost. The material of the separate explosion valve is a special material, only a few manufacturers can manufacture this material, and this material contains Fe, which has an adverse effect on the service life and safety of the cell.

[0004] Chinese invention patent CN115377574B and Chinese invention patent application CN116073042A disclose an integrated stamping process of a top cover sheet and an explosion valve, focusing on the stamping of a material belt in a mold, the stamping of an explosion valve and a safety notch of the explosion valve. However, the problems of unstable burst pressure value caused by stamping and the reduction and instability of the burst pressure value of the explosion valve caused by the shrinkage deformation of the cell after welding are not solved.

[0005] SUMMARY

[0006] The technical problem to be solved by the present invention is to effectively strengthen the protection of the safety notch of the explosion valve during the processing and assembly of the top cover and the battery case of the secondary battery by improving the structure design; and to reduce the burst pressure value and improve the stability of the integrally formed explosion valve in the top cover and the battery case of the secondary battery by improving the processing technology.

[0007] According to a first aspect of the present application, there is provided a top cover having an integrally formed explosion-proof valve, comprising: a top cover body; an explosion-proof valve integrally formed with the top cover body; the top cover body comprising an outer surface and an inner surface opposite to the outer surface; the explosion-proof valve comprising a valve body and a safety notch; the valve body comprising a recess extending towards the inner surface of the top cover body, a lower edge of the recess being inwardly recessed and forming a protrusion extending towards the outer surface of the top cover body, the safety notch being disposed on a top surface of the protrusion.

[0008] Optionally, the protrusion extends a distance less than the distance that the recess extends.

[0009] Optionally, the top surface of the protrusion is located at a position between 10% and 90% of the distance between the outer surface of the top cover body and the lower edge of the recess.

[0010] Optionally, the cross-sectional shape of the recess and the protrusion together is substantially V-shaped.

[0011] According to a second aspect of the present application, there is provided a top cover having an integrally formed explosion-proof valve, comprising: a top cover body; an explosion-proof valve integrally formed with the top cover body; the top cover body comprising an outer surface and an inner surface opposite to the outer surface; the explosion-proof valve comprising a valve body and a safety notch; the valve body comprising a recess extending towards the inner surface of the top cover body, the safety notch being disposed on a bottom surface of the recess; the top cover body further comprising a longitudinal groove extending along a longitudinal axis direction of the top cover body and extending towards the inner surface of the top cover body.

[0012] Optionally, the longitudinal groove is symmetrically disposed on both sides of the valve body.

[0013] Optionally, the cross-sectional shape of the longitudinal groove is substantially V-shaped.

[0014] Optionally, the longitudinal groove extends a distance greater than the distance that the recess extends towards the inner surface of the top cover body.

[0015] According to a third aspect of the present application, there is provided a secondary battery, comprising a battery cell, a battery case accommodating the battery cell, and the above-mentioned top cover having an integrally formed explosion-proof valve, the top cover being mounted on a top opening of the battery case and forming a closed space together with the battery case to seal the battery cell.

[0016] According to a fourth aspect of the present application, there is provided a battery case, comprising: a circumferential side wall and a bottom plate, the circumferential side wall and the bottom plate together with a top cover forming a closed space for accommodating a battery cell; the bottom plate comprising a bottom plate outer surface and a bottom plate inner surface opposite to the bottom plate outer surface, characterized in that: an integrally formed explosion-proof valve is arranged on the bottom plate; the explosion-proof valve comprising a valve body and a safety notch; the valve body comprising a recess extending towards the bottom plate inner surface, a lower edge of the recess being inwardly recessed and forming a protrusion extending towards the bottom plate outer surface, the safety notch being arranged on a top surface of the protrusion.

[0017] Optionally, the protrusion extends a distance less than the recess.

[0018] Optionally, the top surface of the protrusion is located at a position of 10-90% between the bottom plate outer surface and the lower edge of the recess.

[0019] Optionally, the cross-sectional shape of the recess and the protrusion together is substantially V-shaped.

[0020] According to a fifth aspect of the present application, there is provided a battery case, comprising: a circumferential side wall and a bottom plate, the circumferential side wall and the bottom plate together with a top cover forming a closed space for accommodating a battery cell; the bottom plate comprising a bottom plate outer surface and a bottom plate inner surface opposite to the bottom plate outer surface, characterized in that: an integrally formed explosion-proof valve is arranged on the bottom plate; the explosion-proof valve comprising a valve body and a safety notch; characterized in that: the valve body comprises a recess extending towards the bottom plate inner surface, the safety notch being arranged on a bottom surface of the recess; the bottom plate further comprising a longitudinal groove extending along a longitudinal axis direction of the bottom plate and extending towards the bottom plate inner surface.

[0021] Optionally, the longitudinal groove is symmetrically arranged on both sides of the bottom plate.

[0022] Optionally, the cross-sectional shape of the longitudinal groove is substantially V-shaped.

[0023] Optionally, the longitudinal groove extends a distance greater than the recess.

[0024] According to a sixth aspect of the present application, there is provided a secondary battery, comprising a battery cell, the above-mentioned battery case, and a top cover, the top cover being mounted on a top opening of the battery case and together with the battery case forming a closed space for sealing the battery cell.

[0025] According to a seventh aspect of the present application, there is provided a processing method of a top cover with an integrally formed explosion-proof valve, the method comprising locally heating the safety notch of the above-mentioned top cover to improve the metallographic structure of the safety notch.

[0026] Optionally, the local heating includes laser local heating, xenon lamp local irradiation heating and coil local induction heating.

[0027] Optionally, the local heating of the safety notch is performed by laser local heating, and the laser used includes a laser chiller, a laser generator, a light emitting head and a mechanical and electronic control device, with a laser power of 50-600W and a speed range of 2-100mm / s.

[0028] Optionally, the laser local heating of the safety notch includes half-circle, C-shaped or segmented heating.

[0029] According to an eighth aspect of the present application, there is provided a method for processing a battery shell, which comprises locally heating the safety notch of the bottom plate of the battery shell to improve the metallographic structure of the safety notch.

[0030] Optionally, the local heating includes laser local heating, xenon lamp local irradiation heating and coil local induction heating.

[0031] Optionally, the local heating of the safety notch is performed by laser local heating, and the laser used includes a laser chiller, a laser generator, a light emitting head and a mechanical and electronic control device, with a laser power of 50-600W and a speed range of 2-100mm / s.

[0032] Optionally, the laser local heating of the safety notch includes half-circle, C-shaped or segmented heating.

[0033] The top cover and the battery shell with the integrally formed explosion-proof valve of the present application have the following advantages:

[0034] 1) The V-shaped structure of the integrally formed explosion-proof valve can effectively reduce the adverse effects of the thermal shrinkage of the shell cover after welding on the burst pressure value and its stability.

[0035] 2) The integrally formed and stamped explosion-proof valve does not require additional processes for stamping and welding of the explosion-proof valve, thus reducing the number of processes, saving costs and improving production efficiency.

[0036] 3) The integrally formed stamping can be performed on cold-rolled plates with an initial plate thickness of 1.5-3mm, and the stamping thinning amount of the middle explosion-proof valve region of the top cover sheet and the battery shell bottom plate can reach 20-50%, with a wide application range.

[0037] 4) Local heating treatment can make the material structure at the notch more uniform and the material softer, and under the premise of not changing the overall strength of the top cover sheet, the burst pressure value is reduced and stabilized.

[0038] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. Attached Figure Description

[0039] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 is a perspective view (viewed from the outer surface side of the top cover) of an integrally molded explosion-proof valve according to a first embodiment of the present invention.

[0041] Figure 2 is a perspective view (viewed from the inner surface side of the top cover) of an integrally molded explosion-proof valve according to a first embodiment of the present invention.

[0042] Figure 3 is a side view of the top cover of an integrally molded explosion-proof valve according to a first embodiment of the present invention.

[0043] Figure 4 is a front view of the top cover of an integrally molded explosion-proof valve according to a first embodiment of the present invention.

[0044] Figure 5 is an AA cross-sectional view of the top cover of an integrally molded explosion-proof valve according to a first embodiment of the present invention.

[0045] Figure 6 is a partially enlarged view of part M of the top cover of the one-piece molded explosion-proof valve of the present invention in Figure 5.

[0046] Figure 7 is a perspective view (viewed from the outer surface side of the top cover) of an integrally molded explosion-proof valve according to a second embodiment of the present invention.

[0047] Figure 8 is a perspective view (viewed from the inner surface side of the top cover) of an integrally molded explosion-proof valve according to a second embodiment of the present invention.

[0048] Figure 9 is a side view of the top cover of an integrally molded explosion-proof valve according to a second embodiment of the present invention.

[0049] Figure 10 is a front view of the top cover of an integrally molded explosion-proof valve according to a second embodiment of the present invention.

[0050] Figure 11 is a BB cross-sectional view of the top cover of an integrally molded explosion-proof valve according to a second embodiment of the present invention.

[0051] Figure 12 is a perspective view of the battery casing according to the third embodiment of the present invention (viewed from the outer surface of the base plate).

[0052] Figure 13 is a front view of a battery casing according to a third embodiment of the present invention.

[0053] FIG. 14 is a C-C sectional view of a battery case according to a third embodiment of the present application.

[0054] FIG. 15 is a partial enlarged view of the N portion of the top cover of the integrally formed explosion-proof valve of the present application in FIG. 14.

[0055] FIG. 16 is a perspective view of a battery case according to a fourth embodiment of the present application (viewed from the outer surface side of the bottom plate).

[0056] FIG. 17 is a front view of a battery case according to the fourth embodiment of the present application.

[0057] FIG. 18 is a D-D sectional view of a battery case according to the fourth embodiment of the present application.

[0058] FIG. 19a is a metallographic view of the top cover plate material.

[0059] FIG. 19b is a metallographic view of the safety score before local heating.

[0060] FIG. 19c is a metallographic view of the safety score after local heating.

[0061] FIG. 20 is a schematic view of the laser local heating process of one embodiment of the present application.

[0062] FIG. 21 is a metallographic view of the safety score after laser local heating of one embodiment of the present application.

[0063] Reference numerals in the drawings: top cover body 10; explosion-proof valve 11; valve body 111; outer surface 101; inner surface 102; recess 103; recess lower edge 103a; protrusion 104; safety score 112; longitudinal groove 113; longitudinal groove lower edge 113a; battery case 20; circumferential side wall 26; bottom plate 27; case explosion-proof valve 21; case valve body 211; bottom plate outer surface 201; bottom plate inner surface 202; bottom plate recess 203; bottom plate recess lower edge 203a; bottom plate protrusion 204; bottom plate safety score 212; bottom plate longitudinal groove 213; bottom plate longitudinal groove 213a. DETAILED DESCRIPTION

[0064] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, like reference numerals refer to like elements throughout the description. The following exemplary embodiments are not representative of all embodiments consistent with the present application. Rather, they are merely examples of systems consistent with some aspects of the present application as detailed in the appended claims.

[0065] The description of illustrative embodiments according to principles of the present application is presented with reference to the accompanying drawings. The description is made in the context of the embodiments of the application disclosed herein and is made solely for the purpose of illustrating the principles of the application. Any reference to direction or orientation in the description of the embodiments of the application disclosed herein is merely to facilitate describing the embodiments and is not intended to limit the scope of the application in any way. Relative terms such as "downward", "upward", "horizontal", "vertical", "above", "below", "top", "bottom", "side", "end", "front", "rear", and the like as well as derivatives thereof (e.g., "horizontally", "downwardly", "upwardly", etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in any particular orientation unless explicitly indicated otherwise.

[0066] Terms such as "attached", "affixed", "connected", "coupled", "interconnected", and the like, refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly specified otherwise. Moreover, the features and benefits of the application are illustrated by reference to the exemplified embodiments. Accordingly, the application expressly should not be limited to such exemplary embodiments illustrating some possible non-limiting combination of features that can exist alone or in other combinations of features; the scope of the application being defined by the claims appended hereto.

[0067] As shown in FIGS. 1-6, according to a first embodiment of the present application, the top cover with integrated explosion-proof valve comprises: a top cover body 10; an explosion-proof valve 11 integrated with the top cover body 10; the top cover body 10 comprises an outer surface 101 and an inner surface 102 opposite to the outer surface; the explosion-proof valve 11 comprises a valve body 111 and a safety notch 112; the valve body 111 further comprises a recess 103 extending towards the inner surface 102 of the top cover body 10, the lower edge 103a of the recess 103 is inwardly recessed and forms a convex portion 104 extending towards the outer surface 102 of the top cover body 10, and the safety notch 112 is arranged on the convex portion 104.

[0068] The cross-sectional shape formed by the recess 103 and the convex portion 104 together is approximately V-shaped, wherein the convex portion 104 is approximately inversely arc-shaped due to being inwardly recessed and extending upwardly from the recess 103. When the top cover sheet is welded with the battery cell shell, the weld will shrink and deform, and the deformation of the V-shaped structure can compensate for the deformation at the notch, thereby avoiding or reducing the tensile stress at the notch and stabilizing the explosion value.

[0069] Referring to FIG. 6, according to one embodiment of the present application, the convex portion 104 extends a distance h1 that is less than a distance h2 that the concave portion 103 extends. Optionally, the upper surface of the convex portion 104 is located at a position that is between 10% and 90% of the distance between the outer surface of the top cover body 10 and the lower edge of the concave portion. Optionally, the upper surface of the convex portion 104 is located at a position that is 50% of the distance between the outer surface of the top cover body 10 and the lower edge of the concave portion.

[0070] It should be understood that because the safety notch 112 is disposed on the top surface of the convex portion 104, which is actually located between the outer surface of the top cover body 10 and the lower edge 103a of the concave portion 103, when the top cover is punched, transported, and assembled with the battery cell, the impact and collision forces from the outside are blocked by the outer surface of the top cover body 10 and the lower edge portion (i.e., the V-shaped region) of the concave portion 103, thereby avoiding potential damage to the fragile safety notch 112 region and ensuring the stability of the burst value.

[0071] As shown in FIGS. 7-11, according to a second embodiment of the present application, a top cover with an integrally formed explosion-proof valve includes a top cover body 10, an explosion-proof valve 11 integrally formed with the top cover body 10, the top cover body 10 including an outer surface 101 and an inner surface 102 opposite the outer surface, the explosion-proof valve 11 including a valve body 111 and a safety notch 112, the valve body 111 including a concave portion 103 extending toward the inner surface 102 of the top cover body 10, the safety notch 112 being disposed on the bottom surface of the concave portion 103. The top cover body further includes a longitudinal groove 113 extending along the longitudinal axis X direction of the top cover body and extending toward the inner surface of the top cover body.

[0072] According to one embodiment of the present application, the longitudinal groove 113 is symmetrically disposed on both sides of the valve body 111 along the transverse axis Y. The cross-sectional shape of the longitudinal groove 113 is generally V-shaped. When the battery cell shell is welded with the top cover sheet, the weld will shrink and deform, and the deformation of the V-shaped structure can compensate for the deformation at the notch, avoiding or reducing the tensile stress at the notch and stabilizing the burst value.

[0073] Referring to FIG. 11, according to one embodiment of the present application, the longitudinal groove 113 extends a distance h3 toward the inner surface 102 of the top cover body 10 that is greater than a distance h4 that the concave portion 103 extends.

[0074] It should be understood that, since the safety notch 112 is arranged on the bottom surface of the recess 103, its actual position is between the outer surface of the top cover body 10 and the lower edge 113a of the longitudinal groove 113, thus, when the top cover is punched, transported and the battery cell is assembled, the impact force and collision force from the outside will be blocked by the outer surface of the top cover body 10 and the lower edge 113a of the longitudinal groove 113 (i.e. the V-shaped area), thereby avoiding potential damage to the fragile safety notch 112 area and ensuring the stability of the burst value.

[0075] The material of the top cover plate according to the present application can include metal materials such as aluminum and steel.

[0076] According to one aspect of the present application, a secondary battery is provided, which includes a battery cell, a battery case accommodating the battery cell, and a top cover with an integrally formed explosion-proof valve as described above, the top cover being mounted on a top opening of the battery case and forming a closed space together with the battery case to seal the battery cell.

[0077] According to the third embodiment of the present application, the applicant also creatively proposes to integrally form an explosion-proof valve on the battery case through a punching process. Referring to FIGS. 12-15, a battery case 20 is provided, which includes a circumferential side wall 26 and a bottom plate 27, the circumferential side wall 26 and the bottom plate 27 forming a closed space together with a top cover to accommodate a battery cell; the bottom plate 27 includes a bottom plate outer surface 201 and a bottom plate inner surface 202 opposite to the bottom plate outer surface 201, and an integrally formed case explosion-proof valve 21 is arranged on the bottom plate 27; the case explosion-proof valve 21 includes a case valve body 211 and a bottom plate safety notch 212; the case valve body 211 includes a bottom plate recess 203 extending towards the bottom plate inner surface 201, a lower edge of the bottom plate recess 203 is inwardly recessed and forms a bottom plate protrusion 204 extending towards the bottom plate outer surface 201, and the bottom plate safety notch 212 is arranged on a top surface of the bottom plate protrusion 204.

[0078] The bottom plate recess 203 and the bottom plate protrusion 204 together form a V-shaped cross-sectional shape, wherein the bottom plate protrusion 204 is formed in a generally inverted arch shape due to the inwardly recessed and upwardly extending bottom plate recess 203. When the battery case 20 is welded with the top cover sheet, the weld will shrink and deform, and the deformation of the V-shaped structure can compensate for the deformation at the notch, thereby avoiding or reducing the tensile stress at the notch and stabilizing the burst value.

[0079] Referring to FIG. 15, according to one embodiment of the present application, the bottom plate protrusion 204 extends a distance h5 that is less than a distance h6 that the bottom plate recess 203 extends. Optionally, the upper surface of the bottom plate protrusion 204 is located between 10% and 90% of the distance between the bottom plate outer surface 201 and the lower edge of the bottom plate recess 203. Optionally, the upper surface of the bottom plate protrusion 204 is located at 50% of the distance between the bottom plate outer surface 201 and the lower edge of the bottom plate recess 203.

[0080] It should be understood that because the bottom plate safety score 212 is disposed on the top surface of the bottom plate protrusion 204, which is actually located between the bottom plate outer surface 201 and the lower edge 203a of the bottom plate recess 203, when the battery case 20 is punched, transported, and assembled with the battery cell, the impact and collision forces from the outside are blocked by the bottom plate outer surface 201 and the lower edge of the bottom plate recess 203 (i.e., the V-shaped area), thereby avoiding potential damage to the fragile bottom plate safety score 212 area and ensuring the stability of the burst value.

[0081] As shown in FIGS. 16-18, according to a fourth embodiment of the present application, a battery case 20 is provided, comprising a circumferential side wall 26 and a bottom plate 27, which together with a top cover form a closed space for accommodating a battery cell; the bottom plate 27 comprises a bottom plate outer surface 201 and a bottom plate inner surface 202 opposite to the bottom plate outer surface 201, characterized in that: an integrally formed case explosion-proof valve 21 is disposed on the bottom plate 27; the case explosion-proof valve 21 comprises a case valve body 211 and a case safety score 212; the case valve body 211 comprises a bottom plate recess 203 extending towards the bottom plate inner surface 202, and the bottom plate safety score 212 is disposed on the bottom surface of the bottom plate recess 203; the bottom plate 27 further comprises a bottom plate longitudinal groove 213a extending along the longitudinal axis direction of the bottom plate 27 and extending towards the bottom plate inner surface 203.

[0082] According to one embodiment of the present application, the bottom plate longitudinal groove 213 is symmetrically disposed on both sides of the case valve body 211 along the transverse axis Y. The cross-sectional shape of the bottom plate longitudinal groove 213 is generally V-shaped. When the battery case 20 is welded with the top cover sheet, the weld will shrink and deform, and the deformation of the score can be compensated by the V-shaped structure, avoiding or reducing the tensile stress at the score, thereby stabilizing the burst value.

[0083] Referring to FIG. 18, according to one embodiment of the present application, the bottom plate longitudinal groove 213 extends towards the bottom plate inner surface 202 of the battery case 20 a distance h7 that is greater than a distance h8 that the bottom plate recess 203 extends.

[0084] It should be understood that, since the bottom plate safety notch 212 is arranged on the bottom surface of the bottom plate recess 203, its actual position is between the bottom plate outer surface 201 of the battery case 20 and the lower edge 213a of the bottom plate longitudinal groove 213, therefore, during the stamping processing, transportation and cell assembly of the battery case, the impact force and collision force from the outside will be blocked by the bottom plate outer surface 201 and the lower edge 213a of the bottom plate longitudinal groove 213 (i.e. the V-shaped area), thereby avoiding potential damage to the fragile bottom plate safety notch 212 area and ensuring the stability of the burst value.

[0085] The material of the battery case of the present application can include metal materials such as aluminum, steel, etc.

[0086] According to still another aspect of the present application, a secondary battery is provided, which includes a battery cell, the above-mentioned battery case, and a top cover installed on the top opening of the battery case and forming a closed space sealing the battery cell together with the battery case 20.

[0087] The conventional single monomer explosion-proof valve is annealed after stamping, and the material is recrystallized to become soft, and then is welded with the stamped top cover. The structure of the explosion-proof valve integrated top cover and the battery case is that the explosion-proof valve part is integrally stamped with the top cover and the bottom plate of the battery case. Since the raw material of the top cover and the battery case is a cold-rolled plate, the organization itself is also a fibrous organization, and there is a certain anisotropy, and the stamped explosion-proof valve features a circular or racetrack shape, which will inevitably cause the grains at the notch to deform unevenly along the fiber direction and perpendicular to the fiber direction, and the anisotropy and unevenness of the fiber organization at the notch of the explosion-proof valve are further aggravated during the stamping process. And the stamping deformation can reach 85%-99%, which will also cause the material to become hard and brittle under such large deformation. These uneven material organizations at the notch will further cause uneven strength at the notch, and ultimately result in large fluctuations in the burst pressure value. At the same time, during the subsequent welding process of the explosion-proof valve integrated top cover with the case, tensile stress will be generated at the notch due to the shrinkage of the weld or the deformation of the top cover caused by the cell expansion, which has the risk of local cracking.

[0088] In order to solve the problem of uneven metallographic organization and cracking risk at the notch of the explosion-proof valve integrated top cover and the battery case bottom plate, it is necessary to improve the type of the organization at the notch and improve the uniformity and plasticity of the organization at the notch. High-temperature annealing treatment can cause recrystallization at the notch, forming a recrystallized organization, and thus improving the uniformity and plasticity of the material organization at the notch. However, if the explosion-proof valve integrated top cover and the battery case bottom plate are annealed as a whole, this will inevitably result in a decrease in the strength and hardness of other areas of the top cover and the battery case bottom plate, which cannot meet the working requirements of the cell.

[0089] In order to achieve the effect of local material structure uniformity and plasticity increase at the notch part of the explosion-proof valve integrated top cover and the battery shell bottom plate, and not to affect the strength and hardness of other parts, the safety notch of the explosion-proof valve integrated top cover and the battery shell bottom plate is locally heated to improve the metallographic structure of the explosion-proof valve notch area. Three different local heating methods are provided: laser local heating, xenon lamp local irradiation and coil local induction heating. By local heating of the explosion-proof valve notch of the integrated top cover, recrystallization of the material structure at the notch can be achieved, forming uniform and fine recrystallized structure, which can reduce the material strength at the notch and improve the plasticity at the notch, and make the burst pressure value stable.

[0090] Referring to FIGS. 19a, 19b and 19c, the top cover plate metallographic structure is fibrous structure, and the grains are elongated along the rolling direction. The metallographic structure of the safety notch before local heating is fine fibrous structure. After local heating, the material at the safety notch recrystallizes to form equiaxed recrystallized structure, the structure is more uniform, the material softens, the burst pressure value decreases and tends to be stable.

[0091] According to one embodiment of the present application, the laser used includes a laser cold water machine, a laser generator, a light emitting head and a mechanical and electronic control device, the laser power is 50W-600W, and the speed range is 2-100mm / s.

[0092] The explosion-proof valve notch is divided into a burst opening key section and a safety section. The burst opening key section is heated in a half-circle, C-shaped or segmented heating manner to refine the grains in this section and reduce the strength and brittleness of this section, thereby achieving the purpose of reducing the burst opening pressure and improving the stability of the burst pressure. The safety notch section of the explosion-proof valve is not heated or less heated, so as to maintain the strength of this area, thereby preventing the middle area of the explosion-proof valve from being separated from the top cover of the battery cell due to tearing after the explosion-proof valve is burst open, and protecting the safety of the battery pack and other parts.

[0093] According to one embodiment of the present application, the heating track of the half-circle heating is shown in FIG. 20. From position A to position E along B, C and D, the half-circle heating manner can limit the initiation area within the heated notch area, reduce the initiation area range, and make the burst pressure value more stable. After the burst, the sample at position C is taken for metallographic analysis. FIG. 21 is a metallographic graph thereof.

[0094] The applicant conducts a burst pressure test on the top cover with an integrally formed explosion-proof valve of the present application, and the test data is shown in Tables 1 and 2:

[0095] Table 1 is the test data of the bursting pressure of the integral top cover sample with a notch thickness of 0.12 mm. In Table 1, H1 is the thickness of the notch, in mm. S1 is the bursting pressure of the integral top cover after stamping without laser heating treatment, in MPa. L1 is the bursting pressure of the integral top cover after stamping and (180W) laser heating treatment, in MPa. As can be seen from Table 1, the maximum value of the bursting pressure of the S1 stamping state sample is 2.880 MPa, the minimum value is 2.438 MPa, the average value is 2.622 MPa, and the standard deviation is 0.134 MPa. The maximum value of the bursting pressure of the L1 sample after laser treatment is 2.427 MPa, the minimum value is 2.209 MPa, the average value is 2.348 MPa, and the standard deviation is 0.065 MPa. It can be seen that after 180W laser heating treatment, the bursting pressure of the integral top cover is reduced as a whole, and the discrete degree of the bursting pressure data relative to the average value is reduced, and the bursting pressure value is more stable.

[0096] Table 1

[0097] Table 2 is the test data of the bursting pressure of the integral top cover sample with a notch thickness of 0.10 mm. In Table 2, H2 is the thickness of the notch, in mm. S2 is the bursting pressure of the integral top cover after stamping without laser heating treatment, in MPa. L2 is the bursting pressure of the integral top cover after stamping and (300W) laser heating treatment, in MPa. As can be seen from Table 2, the maximum value of the bursting pressure of the S2 stamping state sample is 2.189 MPa, the minimum value is 2.057 MPa, the average value is 2.155 MPa, and the standard deviation is 0.055 MPa. The maximum value of the bursting pressure of the L2 sample after laser treatment is 1.854 MPa, the minimum value is 1.751 MPa, the average value is 1.793 MPa, and the standard deviation is 0.039 MPa. It can be seen that after 300W laser heating treatment, the bursting pressure of the integral top cover is reduced as a whole, and the discrete degree of the bursting pressure data relative to the average value is reduced, and the bursting pressure value is more stable.

[0098] Table 2

[0099] It should be understood that the above local heating treatment of the safety notch of the top cover and the bursting pressure test are also applicable to the safety notch of the battery shell bottom plate, and similar effects are obtained.

[0100] In summary, the present application, by means of the new structure of the integrally formed explosion valve top cover and battery shell, can offset the influence of the increased pre-stress in the scored area of the explosion valve caused by welding shrinkage after the cell shell cover is welded, so as to ensure that the explosion pressure change and the instability of the explosion pressure caused by the pre-stress of welding shrinkage are minimized after the cell is welded. On the other hand, the present application aims to solve the problem of large and uneven deformation of the material caused by the integrally formed explosion valve top cover and battery shell during stamping, which forms elongated fiber organization, which will lead to uneven material organization and high hardness at the safety score of the explosion valve, and further cause uneven strength and brittle cracking of the material at the score, ultimately resulting in unstable explosion pressure. Therefore, the technical solution provided by the present application mainly improves the structure of the integrally formed explosion valve top cover and battery shell, and performs local heating treatment on the safety score to recrystallize the material organization at the score, form uniform and fine recrystallized organization, reduce the hardness and strength of the material at the score, and improve the plasticity at the score, so as to stabilize the explosion pressure of the explosion valve. In addition, this technology can also reduce production cost and improve product quality and production efficiency.

[0101] The features and benefits of the application are illustrated by reference to specific embodiments. Accordingly, the application expressly should not be limited to such exemplary embodiments illustrating some possible non-limiting combinations of features, which features can exist in other combinations than those explicitly stated and / or shown in the examples.

[0102] The above-described embodiments are merely specific implementations of the present application, which are used to illustrate the technical solutions of the present application, rather than limit the same. The protection scope of the present application is not limited thereto, although the foregoing embodiments of the present application have been described in detail, those skilled in the art should understand that any person skilled in the art can modify or easily think of changes to the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some technical features; and these modifications, changes or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A top cover having an integrally formed explosion relief valve, comprising: A top cover body; an explosion-proof valve integrally formed with the top cover body; the top cover body comprising an outer surface and an inner surface opposite to the outer surface; the explosion-proof valve comprising a valve body and a safety notch; characterized in that: the valve body comprises a recess extending towards the inner surface of the top cover body, the lower edge of the recess is inwardly recessed and forms a convex portion extending towards the outer surface of the top cover body, and the safety notch is arranged on the top surface of the convex portion.

2. A top cover with an integrated explosion relief valve according to claim 1, characterized in that: The convex portion extends a distance less than the distance that the recess extends.

3. A top cover with an integrated explosion relief valve according to claim 2, characterized in that: The top surface of the convex portion is located at 10-90% of the position between the outer surface of the top cover body and the lower edge of the recess.

4. A top cover with an integrally formed explosion relief valve as defined in claim 1, characterized in that: The cross-sectional shape formed by the recess and the convex portion together is approximately V-shaped.

5. A secondary battery characterized by comprising: A battery cell, a battery case containing the battery cell, and a top cover according to any one of claims 1-4, the top cover being mounted on the top opening of the battery case and forming a closed space sealing the battery cell together with the battery case.

6. A top cover having an integrally formed explosion relief valve, comprising: A top cover body; an explosion-proof valve integrally formed with the top cover body; the top cover body comprising an outer surface and an inner surface opposite to the outer surface; the explosion-proof valve comprising a valve body and a safety notch; characterized in that: the valve body comprises a recess extending towards the inner surface of the top cover body, the safety notch is arranged on the bottom surface of the recess; and the top cover body further comprises a longitudinal groove extending along the longitudinal axis direction of the top cover body and extending towards the inner surface of the top cover body.

7. A top cover with an integrated explosion relief valve according to claim 6, characterized in that: The longitudinal groove is symmetrically arranged on both sides of the valve body.

8. A top cover with an integrated explosion relief valve according to claim 6, characterized in that: The cross-sectional shape of the longitudinal groove is approximately V-shaped.

9. A top cover with an integrally formed explosion relief valve as defined in claim 6, characterized in that: The longitudinal groove extends a distance greater than the distance that the recess extends.

10. A secondary battery characterized by comprising: A battery cell, a battery case containing the battery cell, and a top cover according to any one of claims 6-9, the top cover being mounted on the top opening of the battery case and forming a closed space sealing the battery cell together with the battery case.

11. A battery housing, comprising: A circumferential side wall and a bottom plate, the circumferential side wall and the bottom plate together with a top cover forming a closed space containing a battery cell; the bottom plate comprising a bottom plate outer surface and a bottom plate inner surface opposite to the bottom plate outer surface, characterized in that: an explosion-proof valve integrally formed with the bottom plate is arranged on the bottom plate; the explosion-proof valve comprising a valve body and a safety notch; the valve body comprising a recess extending towards the bottom plate inner surface, the lower edge of the recess being inwardly recessed and forming a convex portion extending towards the bottom plate outer surface, and the safety notch being arranged on the top surface of the convex portion.

12. The battery case of claim 11, wherein: The convex portion extends a distance less than the distance that the recess extends.

13. The battery case of claim 12, wherein: The top surface of the convex portion is located at 10-90% of the position between the bottom plate outer surface and the lower edge of the recess.

14. The battery case of claim 11, wherein: The cross-sectional shape formed by the recess and the convex portion together is approximately V-shaped.

15. A secondary battery characterized by comprising: A battery cell, a battery case according to claims 11-14, and a top cover, the top cover being mounted on the top opening of the battery case and forming a closed space sealing the battery cell together with the battery case.

16. A battery housing, comprising: A circumferential side wall and a bottom plate, the circumferential side wall and the bottom plate together with a top cover forming a closed space containing a battery cell; the bottom plate comprising a bottom plate outer surface and a bottom plate inner surface opposite to the bottom plate outer surface, characterized in that: an integrally formed explosion-proof valve is arranged on the bottom plate; the explosion-proof valve comprises a valve body and a safety notch; the valve body comprises a recess extending towards the bottom plate inner surface, and the safety notch is arranged on the bottom surface of the recess; the bottom plate further comprises a longitudinal groove extending along the longitudinal axis direction of the bottom plate and extending towards the bottom plate inner surface.

17. The battery case of claim 16, wherein: The longitudinal groove is symmetrically arranged on both sides of the bottom plate.

18. The battery case of claim 16, wherein: The cross-sectional shape of the longitudinal groove is approximately V-shaped.

19. The battery case of claim 16, wherein: The distance that the longitudinal groove extends towards the bottom plate inner surface is greater than the distance that the recess extends.

20. A secondary battery characterized by comprising: A battery cell, a battery shell according to claims 16-19, and a top cover, the top cover being mounted on the top opening of the battery shell and forming a closed space together with the battery shell to seal the battery cell.

21. A method of manufacturing a top cover having an integrally formed explosion relief valve, characterized by, The safety notch in the top cover according to any one of claims 1-4, 6-9 is locally heated to improve the metallographic structure of the safety notch.

22. The method of claim 21, wherein, The local heating includes laser local heating, xenon lamp local irradiation heating, and coil local induction heating.

23. The method of claim 21, wherein, The safety notch is locally heated by laser local heating; the laser used includes a laser chiller, a laser generator, a light-emitting head, and a mechanical and electronic control device, with a laser power of 50W-600W and a speed range of 2-100mm / s.

24. The method of claim 23, wherein, The laser local heating of the safety notch includes half-circle, C-shaped, or segmented heating.

25. A method of processing a battery case, characterized by, The safety notch of the bottom plate of the battery shell according to any one of claims 11-14, 16-19 is locally heated to improve the metallographic structure of the safety notch.

26. The method of claim 25, wherein, The local heating includes laser local heating, xenon lamp local irradiation heating, and coil local induction heating.

27. The method of claim 25, wherein The safety notch is locally heated by laser local heating; the laser used includes a laser chiller, a laser generator, a light-emitting head, and a mechanical and electronic control device, with a laser power of 50W-600W and a speed range of 2-100mm / s.

28. The method of claim 27, wherein, The laser local heating of the safety notch includes half-circle, C-shaped, or segmented heating.

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