Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery comprises a shell, an electrode assembly, a current collecting component and a cover plate, the shell comprises an end wall and a side wall surrounding the end wall; the electrode assembly is accommodated in the shell; the current collecting component is arranged at one end, facing the opening, of the electrode assembly and is electrically connected with the electrode assembly; the cover plate covers and seals the opening, a convex part protruding towards the interior of the shell surrounds the outer periphery of the cover plate, a recess is formed in the side, away from the electrode assembly, of the convex part, a limiting part surrounds the outer side of the convex part, and the limiting part extends towards the radial outer side of the cover plate and is fixedly connected with the end face of the opening; a weak part is arranged on the bottom wall of the recess, a pressure relief area is formed by surrounding the weak part, and the weak part is configured to be broken when the internal pressure of the secondary battery exceeds a threshold value, so that the current collecting component is far away from the electrode assembly along with the pressure relief area, and the technical problem that the pressure relief area of the explosion-proof valve is too small due to the limitation of transportation and use safety can be solved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and in particular to a secondary battery, a battery pack and an electronic device. Background Art

[0002] Large cylindrical batteries are increasingly favored by major automakers due to their high safety, long life, excellent fast charging performance, good battery consistency and low production cost.

[0003] Conventional large cylindrical batteries include a housing, an electrode assembly disposed within the housing, and a current collecting member disposed between the housing's end walls and the corresponding end faces of the electrode assembly. Furthermore, explosion-proof valves are constructed on one or both of the housing's end walls to facilitate opening and discharging the battery's internal contents in the event of thermal runaway. For transportation and operational safety considerations, the pressure relief area is generally limited. This limited area results in a high pressure required to open the explosion-proof valve, resulting in a slow response and reduced battery safety. Utility Model Content

[0004] The utility model provides a secondary battery, a battery pack and an electronic device, which are used to improve the technical problem that the pressure relief area of an explosion-proof valve is too small due to restrictions on transportation and use safety.

[0005] To achieve the above-mentioned purpose and other related purposes, the present invention provides a secondary battery, a battery pack and an electronic device, wherein the secondary battery comprises: a shell, an electrode assembly, a current collecting component and a cover plate; the shell comprises an end wall and a side wall surrounding the end wall, and an opening is formed at one end of the side wall facing away from the end wall; the electrode assembly is accommodated in the shell; the current collecting component is arranged at the end of the electrode assembly facing the opening, and the current collecting component is electrically connected to the electrode assembly; the cover plate covers and seals the opening, and the outer periphery of the cover plate is surrounded by a convex portion protruding toward the inside of the shell, and the side of the convex portion facing away from the electrode assembly is formed into a recess, and the outer side of the convex portion is surrounded by a limiting portion, which extends radially outward from the cover plate and is fixedly connected to the end face of the opening; a weak portion is provided on the bottom wall of the recess, and a pressure relief area is formed around the weak portion, and the weak portion is configured to break when the internal pressure of the secondary battery exceeds a threshold value.

[0006] In the above technical solution, a surrounding depression is provided on the outer periphery of the cover plate, and the weak portion is positioned on the bottom wall of the depression, thereby preventing the weak portion from direct contact with the outside world. The depression also provides protection for the weak portion, reducing the risk of damage and rupture during transportation and use. At the same time, a pressure relief area is formed around the weak portion. Because the depression is located on the outer periphery of the cover plate, a larger pressure relief area is obtained, which helps to increase the sensitivity of the weak portion and improve the pressure relief efficiency. Furthermore, when the internal pressure of the secondary battery exceeds a threshold, the weak portion ruptures, and the pressure relief area folds outward or completely detaches under the impact of the internal pressure, forming a pressure relief hole in the cover plate. At the same time, the current collecting member can be welded to the electrode assembly and ruptured under the impact of the internal pressure. Because the pressure relief area is sufficiently large, it is conducive to the current collecting member folding outward or directly detaching from the pressure relief hole, thereby reducing the obstruction caused by the current collecting member to the discharge of internal substances of the battery, thereby improving the safety of the secondary battery.

[0007] In an example of the secondary battery of the present invention, the current collecting member is welded to the electrode assembly and forms a first weld mark. Along the height direction of the secondary battery, the projection of the pressure relief area on the current collecting member covers at least 80% of the first weld mark.

[0008] In the above technical solution, the first weld mark corresponds to the connection area between the current collecting member and the electrode assembly, and the projection of the pressure relief area on the current collecting member covers at least 80% of the first weld mark. This can ensure that when the internal pressure of the secondary battery exceeds the threshold, at least 80% of the welded connection between the current collecting member and the electrode assembly will not be restricted by the cover plate, which is conducive to the separation of the current collecting member and the electrode assembly, thereby enabling the current collecting member to fold outward or directly detach from the pressure relief hole, thereby reducing the obstruction caused by the current collecting member to the discharge of internal substances of the battery.

[0009] In an example of the secondary battery of the present invention, the current collecting member is welded to the cover plate to form a second weld mark, and at least 50% of the second weld mark falls within the pressure relief area.

[0010] In the above technical solution, the second weld mark corresponds to the connection area between the current collecting member and the cover plate. The arrangement in which at least 50% of the second weld mark falls within the pressure relief area can achieve the effect of applying a pulling force to the current collecting member when the pressure relief area folds outward or detaches when the internal pressure of the secondary battery exceeds the threshold, thereby facilitating the current collecting member to fold or detach together with the pressure relief area.

[0011] In an example of the secondary battery of the present invention, the weak portion includes a continuous area and a discontinuous area, and the pressure relief area is configured to break along the continuous area and fold toward the outside of the shell when the pressure in the shell exceeds a threshold.

[0012] In the above technical solution, the outline of the weak part is not closed. When the pressure in the shell exceeds the threshold, the continuous area breaks, while the interrupted area does not break. The pressure relief area can be broken along the continuous area and folded toward the outside of the shell without detaching from the secondary battery and flying out. This setting can reduce the occurrence of serious problems such as short circuit and thermal failure between other secondary batteries in the battery module, and increase the safety performance at the battery module level.

[0013] In an example of the secondary battery of the present invention, the second weld mark at least partially overlaps with the bottom wall where the interruption area is located.

[0014] In the above technical solution, on the one hand, the thickness of the bottom wall where the interruption area is located is uniform and the surface is flat, which is convenient for welding and can improve the reliability of welding between the current collecting component and the cover plate; on the other hand, the current collecting component and the cover plate are at least partially connected in the interruption area. When pressure relief occurs, the current collecting component will apply tension to the cover plate, further limiting the flying out of the pressure relief area.

[0015] In an example of the secondary battery of the present invention, along the radial direction of the secondary battery, the distance from the weak portion to the inner side of the side wall is greater than or equal to 2 mm.

[0016] In the above technical solution, the distance from the weak part to the inner side of the side wall is limited to be greater than or equal to 2 mm, which can reduce the thermal impact on the weak part during welding of the limiting part and the side wall, thereby preventing the weak part from thermally deforming and affecting the welding connection between the cover plate and the current collecting component.

[0017] In an example of the secondary battery of the present invention, the weak portion is a notch or a thinned structure, and the notch or thinned structure is provided on a side of the bottom wall away from the electrode assembly.

[0018] In the above technical solution, the notch or thinning structure is set on the outer side of the cover plate, which is convenient for processing and for controlling the distance between the second weld mark and the weak part during welding. Moreover, since the weak part is located in the depression, it can be better protected and not easily damaged.

[0019] In an example of the secondary battery of the present invention, a corrosion-resistant layer is provided on the surface of the weak portion.

[0020] In the above technical solution, the provision of the corrosion-resistant layer has the functions of preventing rust and corrosion, which can alleviate the problem that the thinner weak parts are more easily damaged due to rust and corrosion, thereby increasing the service life of the secondary battery.

[0021] The utility model also provides a battery pack, which includes any one of the above-mentioned secondary batteries.

[0022] The utility model also provides an electronic device, which includes the above-mentioned battery pack.

[0023] In the secondary battery of the present invention, a surrounding depression is provided on the outer periphery of the cover plate, and the weak portion is arranged on the bottom wall of the depression to prevent the weak portion from direct contact with the outside world. The depression can provide protection for the weak portion, reducing the risk of damage and rupture of the weak portion during transportation and use. At the same time, a pressure relief area is formed around the weak portion. Since the depression is located on the outer periphery of the cover plate, a larger pressure relief area can be obtained, which is conducive to improving the sensitivity of the weak portion and improving the pressure relief efficiency. Moreover, when the internal pressure of the secondary battery exceeds a threshold, the weak portion breaks, and the pressure relief area folds outward or completely detaches under the impact of the internal pressure, and a pressure relief hole is formed in the cover plate. At the same time, the current collecting component can be welded to the electrode assembly and broken under the impact of the internal pressure. Since the pressure relief area is large enough, the current collecting component can be folded outward or directly detached from the pressure relief hole, thereby reducing the obstruction caused by the current collecting component to the discharge of internal substances of the battery, thereby improving the safety of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a schematic diagram of the overall structure of an embodiment of a secondary battery of the present utility model;

[0026] Figure 2 This is a schematic structural diagram of an electrode assembly of an embodiment of a secondary battery of the present invention;

[0027] Figure 3 for Figure 1 A partial enlarged view of point A in the middle;

[0028] Figure 4 A top view of an embodiment of a secondary battery of the present invention;

[0029] Figure 5 This is a structural diagram of a cover plate of an embodiment of a secondary battery of the present invention;

[0030] Figure 6 A top view of an embodiment of a secondary battery of the present invention;

[0031] Figure 7 is a schematic diagram of a battery pack according to an embodiment of the present invention;

[0032] Figure 8 FIG. 1 is a schematic diagram of an electronic device according to an embodiment of the present invention.

[0033] Component number description

[0034] 1. Electronic device; 10. Battery pack; 11. Working unit; 101. Housing; 102. Housing cover; 100. Secondary battery; 110. Housing; 111. End wall; 112. Side wall; 113. Opening; 120. Electrode assembly; 121. First electrode sheet; 1211. Negative electrode current collector; 1212. First coated area; 1213. First uncoated area; 122. Separator; 123. Second electrode sheet; 1231. Positive electrode current collector ; 1232, second coated area; 1233, second uncoated area; 124, first pole ear; 125, second pole ear; 130, current collecting component; 131, first weld mark; 140, cover plate; 141, convex portion; 142, concave portion; 1421, bottom wall; 143, limiting portion; 144, weak portion; 1441, continuous area; 1442, interrupted area; 145, pressure relief area; 146, second weld mark; 150, pole. DETAILED DESCRIPTION

[0035] The following describes the implementation of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation methods. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following examples and the features in the examples can be combined with each other unless there is a conflict. It should also be understood that the terms used in the examples of the present invention are for the purpose of describing specific implementation methods, not for the purpose of limiting the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under the conditions recommended by the manufacturers.

[0036] When numerical ranges are given in the examples, it should be understood that unless otherwise specified herein, both endpoints of each numerical range and any value between the endpoints may be used. Unless otherwise defined, all technical and scientific terms used in this utility model are consistent with the prior art as understood by those skilled in the art and the description of this utility model. Any prior art methods, equipment, and materials similar or equivalent to those in the examples of this utility model may also be used to implement this utility model.

[0037] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0038] A secondary battery includes an electrode assembly, which is a component where electrochemical reactions occur in the secondary battery and may include one or more electrode assemblies.

[0039] The secondary battery also includes a shell, a cover plate and a current collecting member. The shell includes an end wall and a side wall surrounding the end wall. One end of the side wall has an opening. The electrode assembly can be assembled into the shell through the opening of the shell. The cover plate is used to cover the opening of the shell to achieve sealing. The shell and the electrode assembly are electrically connected through the current collecting member. In addition, an explosion-proof valve is constructed on one or both end walls of the shell so that when the battery suffers thermal runaway, the explosion-proof valve opens to discharge the internal substances of the battery.

[0040] Considering the risk of weak parts being damaged and ruptured during transportation and use, the area of the pressure relief zone is generally not too large. However, the inventors found that due to the limitation of the area of the pressure relief zone, the pressure required to open the explosion-proof valve is relatively high, and the response is not sensitive, which will reduce the safety of the battery.

[0041] In view of this, the utility model provides a technical solution, in which the weak part is arranged on the bottom wall of the depression to avoid direct contact between the weak part and the outside world, and the depression can provide protection for the weak part, reducing the risk of damage and rupture of the weak part during transportation and use. At the same time, a pressure relief area is formed around the weak part. Since the depression is located at the outer periphery of the cover plate, a larger pressure relief area can be obtained, which is conducive to improving the sensitivity of the weak part and improving the pressure relief efficiency.

[0042] See also Figures 1 to 8 The present invention provides a secondary battery 100 , a battery pack 10 and an electronic device 1 . The secondary battery 100 includes a housing 110 , an electrode assembly 120 , a current collecting member 130 , a cover plate 140 and a terminal post 150 .

[0043] See also Figure 1The housing 110 includes an end wall 111 and a side wall 112 surrounding the end wall 111. The connection between the end wall 111 and the side wall 112 can be achieved in a variety of ways, as long as a stable seal and electrical connection can be established, such as integral stamping, integral casting, or separate welding. The shape of the side wall 112 is not limited and can be cylindrical or prismatic, or can be formed along any other closed-loop contour that matches the end wall 111. In this embodiment, the outer edge of the end wall 111 is circular, and the side wall 112 is cylindrical and surrounds the outer edge of the end wall 111. A circular opening 113 is formed at the end of the side wall 112 facing away from the end wall 111. A cavity is formed within the housing 110, enclosed by the end wall 111 and the side wall 112, for accommodating the electrode assembly 120, electrolyte, and other essential battery components. Specifically, the diameter of the housing 110 can be determined based on the specific dimensions of the electrode assembly 120, such as 18 mm, 21 mm, 46 mm, etc. The shell 110 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. In order to prevent the shell 110 from rusting during long-term use, a layer of rust-proof material such as metal nickel can be plated on the surface of the shell 110.

[0044] See also Figures 1 to 2 The electrode assembly 120 is housed in the housing 110. The electrode assembly 120 is a component where electrochemical reactions occur in the secondary battery 100. The housing 110 may contain one or more electrode assemblies 120. The electrode assembly 120 includes a first electrode sheet 121, a second electrode sheet 123, and a separator 122 stacked and wound to form a wound structure 126. The first electrode sheet 121 and the second electrode sheet 123 have opposite polarities. In some embodiments, the first electrode sheet 121 is a positive electrode sheet and the second electrode sheet 123 is a negative electrode sheet. In other embodiments, the first electrode sheet 121 is a negative electrode sheet and the second electrode sheet 123 is a positive electrode sheet.

[0045] See also Figures 1 to 2 In this embodiment, the first electrode sheet 121 is a negative electrode sheet, and the first electrode sheet 121 includes a negative electrode current collector 1211 and a negative electrode active material. The negative electrode active material is coated on the surface of the negative electrode current collector 1211; the negative electrode current collector 1211 includes a first coated area 1212 coated with the active material and a first uncoated area 1213 not coated with the active material. The first uncoated area 1213 is located at the end of the first electrode sheet 121. The first uncoated area 1213 extends out of the separator 122 along the winding axis direction of the electrode assembly 120 and is bent toward the winding axis to form a first electrode tab 124. The first electrode tab 124 is the corresponding negative electrode tab.

[0046] See also Figures 1 to 2The second electrode sheet 123 is a positive electrode sheet. Specifically, the second electrode sheet 123 includes a positive electrode current collector 1231 and a positive electrode active material. The positive electrode active material is coated on the surface of the positive electrode current collector 1231; the positive electrode current collector 1231 includes a second coated area 1232 coated with an active material and a second uncoated area 1233 not coated with an active material. The second uncoated area 1233 is located at the end of the second electrode sheet 123. The other end of the second uncoated area 1233 extends out of the diaphragm 122 along the winding axis direction of the electrode assembly 120 and is bent toward the winding axis to form a second electrode tab 125. The second electrode tab 125 is the corresponding positive electrode tab.

[0047] See also Figures 1 to 2 The separator 122 is disposed between the first electrode sheet 121 and the second electrode sheet 123 to separate the positive electrode active material layer from the negative electrode active material layer. Taking the lithium-ion secondary battery 100 as an example, the material of the positive electrode current collector 1231 can be aluminum, and the positive electrode active material layer includes a positive electrode active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The material of the negative electrode current collector 1211 can be copper, and the negative electrode active material layer includes a negative electrode active material, which can be carbon or silicon. The base material of the separator 122 can be polypropylene (PP) or polyethylene (PE), etc. To provide protection and insulation for the electrode assembly 120, an insulating film can also be coated on the outside of the electrode assembly 120. The insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other polymer materials.

[0048] See also Figure 1 and Figure 2 Furthermore, first tab 124 faces end wall 111 or opening 113, while second tab 125 faces the other end of housing 110. In this embodiment, second tab 125 faces end wall 111 and is electrically connected to pole 150, causing pole 150 to be positively charged. The tab facing opening 113 is first tab 124, and housing 110 is electrically connected to first tab 124, causing it to be negatively charged. However, in other embodiments, first tab 124 may be connected to pole 150, while second tab 125 may be connected to housing 110.

[0049] See also Figure 1The pole 150 is fixed to the end wall 111 and electrically connected to the electrode assembly 120. Specifically, the end wall 111 is provided with a pole 150 hole. The pole 150 is installed through the pole 150 hole and is insulated from the end wall 111. The end of the pole 150 facing the electrode assembly 120 passes through the end wall 111 to be directly electrically connected to the second pole tab 125 or through an indirect transfer. The structure of the pole 150 can be any suitable form that can pass through the end wall 111 and electrically connect to the second pole tab 125 of the electrode assembly 120. For example, the cross-section can be circular, square, prismatic, or a special-shaped profile that can achieve stable electrical conduction. The pole 150 hole corresponds to the shape of the pole 150. In this embodiment, the cross-section of the pole 150 is circular.

[0050] See also Figure 1 and Figure 3 The electrode assembly 120 is electrically connected to the housing 110 via the current collecting member 130. In a specific embodiment, the current collecting member 130 is welded to the first electrode tab 124. The welding method can be ultrasonic welding, resistance welding, laser welding, or the like, without limitation. In this embodiment, laser welding is used. The first electrode tab 124 is the negative electrode tab. Copper is preferably selected as the material of the current collecting member 130. It should be noted that the shape of the current collecting member 130 can be any rotationally symmetrical shape, such as a circle, square, regular polygon, petal, or other shape with a center of symmetry that can be aligned with the original shape after being rotated a certain angle around the center of symmetry. This is not limited to any shape that can achieve a stable and reliable electrical connection. The center of the current collecting member 130 is its own center of symmetry. To improve positioning, ease of processing, interchangeability, and uniformity during installation, the current collecting member 130 in this embodiment adopts a circular structure.

[0051] See also Figures 3 to 6The cover plate 140 covers and seals the opening 113, and the outer periphery of the cover plate 140 is surrounded by a protrusion 141 protruding toward the inside of the shell 110. It can be understood that the protrusion 141 surrounds the outer periphery of the cover plate 140 and is not limited to the case where the cover plate 140 is circular. For example, if the cover plate 140 is square or polygonal, the protrusion 141 can be a corresponding square or polygon. Preferably, the outer edge of the protrusion 141 cooperates with the side wall 112, and the protrusion 141 guides the assembly of the cover plate 140 and the opening 113, as well as the cooperation between the side wall 112 of the shell 110 and the cover plate 140. This arrangement can enable the cover plate 140 to be quickly positioned along the circumferential direction with the opening 113, thereby improving the welding efficiency and the radial position accuracy of the welding. At the same time, the protrusion 141 also has the effect of blocking the laser when welding the cover plate 140 and the side wall 112 of the shell 110. The connection method between the protrusion 141 and the cover plate 140 is not limited. It can be integrally stamped or obtained by machining on the cover plate 140 to remove material. In one embodiment of the secondary battery 100 of the present invention, the protrusion 141 is obtained by stamping. The side of the protrusion 141 facing away from the electrode assembly 120 is formed as a recess 142. The stamping method can form the recess 142 without wasting material. In some embodiments, the bottom wall 1421 of the recess 142 is used for welding to the current collecting member 130. This arrangement can accommodate the weld mark within the recess 142 to prevent affecting the flatness of the cover plate 140. The outer side of the protrusion 141 is surrounded by a limiting portion 143. The limiting portion 143 extends radially outward from the cover plate 140 and is fixedly connected to the end face of the opening 113. The provision of the limiting portion 143 can, on the one hand, achieve axial positioning of the cover plate 140 and the shell 110, and on the other hand, can increase the airtightness of the weld between the cover plate 140 and the side wall 112 of the shell 110.

[0052] Further, see Figures 3 to 6A weak portion 144 is provided on the bottom wall 1421 of the recess 142, and a pressure relief area 145 is formed around the weak portion 144. The weak portion 144 is configured to break when the internal pressure of the secondary battery 100 exceeds a threshold value; the weak portion 144 can be continuously provided on the bottom wall 1421, or can be provided with multiple segments at intervals. It should be noted that even if it is provided with multiple segments, the intervals between the multiple segments of the weak portion 144 need to be easy to tear to achieve a larger pressure relief area. The outline of the weak portion 144 can be a closed figure or an open figure, as long as a larger pressure relief area can be achieved. It can be understood that when the outline of the weak portion 144 is a closed figure, the pressure relief area 145 is completely separated from the secondary battery 100 under the impact of the internal pressure, and when the outline of the weak portion 144 is an open figure, the pressure relief area 145 is folded outward under the impact of the internal pressure. It should be noted that the weak portion 144 can be one or a combination of notches or thinning structures. The notches or thinning structures can be arranged only on the side of the bottom wall 1421 away from the electrode assembly 120, or only on the side facing the electrode assembly 120, or on both sides of the bottom wall 1421. As long as it can achieve rupture when the internal pressure of the secondary battery 100 exceeds the threshold, the above form is not limited.

[0053] In the above technical solution, the weak portion 144 is arranged on the bottom wall 1421 of the recess 142 surrounding the outer periphery of the cover plate 140, so as to avoid direct contact between the weak portion 144 and the outside world. The recess 142 can provide protection for the weak portion 144, thereby reducing the risk of damage and rupture of the weak portion 144 during transportation and use. At the same time, a larger pressure relief area 145 can be obtained, which is beneficial to improving the sensitivity of the weak portion 144 and the pressure relief efficiency. On the other hand, when the internal pressure of the secondary battery 100 is When the threshold value is exceeded, the weak portion 144 breaks, and the pressure relief area 145 folds outward or completely detaches under the impact of the internal pressure, and a pressure relief hole is formed in the cover plate 140; in addition, the welding between the current collecting component 130 and the electrode assembly 120 can be broken under the impact of the internal pressure. Since the pressure relief area 145 is large enough, it is conducive to the current collecting component 130 folding outward or directly detaching from the pressure relief hole, so as to reduce the obstruction of the current collecting component 130 to the discharge of internal substances of the battery, thereby improving the safety of the secondary battery 100.

[0054] See also Figure 4 and Figure 6In an example of the secondary battery 100 of the present invention, the current collecting member 130 is welded to the electrode assembly 120, and a first weld mark 131 is formed. The first weld mark 131 is formed through a heating and subsequent cooling process, and can represent the welding path of the current collecting member 130 and the electrode assembly 120. The shape of the first weld mark 131 is not limited, and can be a straight line, a curve (a wavy line, a circular arc, a sine curve, etc.), a broken line, or other irregular shapes. The number and position of the first weld marks 131 are also not limited, as long as a stable electrical connection between the current collecting member 130 and the electrode assembly 120 can be achieved. In this embodiment, four groups of first weld marks 131 are provided, and each group of first weld marks 131 includes three wavy curves. Figure 4 and Figure 6 The first weld mark 131 is for illustrative purposes only and is not intended to define the first weld mark 131. Along the height of the secondary battery 100, the projection of the pressure relief area 145 on the current collecting member 130 covers at least 80% of the first weld mark 131. This arrangement ensures that when the internal pressure of the secondary battery 100 exceeds a threshold, at least 80% of the welded connection between the current collecting member 130 and the electrode assembly 120 will not be restricted by the cover plate 140, facilitating separation of the current collecting member 130 and the electrode assembly 120. This allows the current collecting member 130 to fold outward from the pressure relief hole or directly detach, thereby reducing the obstruction caused by the current collecting member 130 to the discharge of internal substances from the battery.

[0055] In an example of the secondary battery 100 of the present invention, the current collecting member 130 is welded to the cover plate 140 and a second weld mark 146 is formed. The shape of the second weld mark 146 is not limited and can be a straight line, a curve (a wavy line, a circular arc, a sine curve, etc.), a broken line or other irregular shapes. The number and position of the second weld mark 146 are also not limited. For example, it can be welded to the bottom wall 1421 or to other positions of the cover plate 140. As long as a stable electrical connection between the current collecting member 130 and the cover plate 140 can be achieved, the second weld mark 146 can be an overall surrounding type or a spaced-apart multiple-segment arrangement. In this embodiment, the second weld mark 146 includes three spaced-apart arcs. Figure 4 and Figure 6 The second weld mark 146 is merely illustrative and does not define the second weld mark 146 . Preferably, at least 50% of the second weld mark 146 falls within the pressure relief region 145 . It will be appreciated that this ratio is 50% of the total cross-sectional area of the second weld mark 146 . This configuration applies tension to the current collecting member 130 when the pressure relief region 145 folds outward or detaches when the internal pressure of the secondary battery 100 exceeds a threshold, facilitating the folding or detachment of the current collecting member 130 along with the pressure relief region 145.

[0056] See also Figure 6In one example of a secondary battery 100 of the present invention, the weak portion 144 includes a continuous region 1441 and a discontinuous region 1442. That is, the outline of the weak portion 144 is not closed. The shape and length of the continuous region 1441 and the discontinuous region 1442 are not limited, as long as the discontinuous region 1442 is protected from tearing during pressure relief. The pressure relief region 145 is configured to break along the continuous region 1441 and fold outward from the housing 110 when the pressure within the housing 110 exceeds a threshold, rather than detaching from the secondary battery 100 and flying out. This configuration can reduce the possibility of serious problems such as short circuits and thermal failures between other secondary batteries 100 within the battery module, thereby enhancing safety performance at the battery module level.

[0057] See also Figure 6 In one example of the secondary battery 100 of the present invention, the second weld mark 146 at least partially overlaps with the bottom wall 1421 where the interruption region 1442 is located. On the one hand, the interruption region 1442 has a uniform thickness and a flat surface, making it convenient for welding and improving the reliability of the weld between the current collecting member 130 and the cover plate 140. On the other hand, the current collecting member 130 and the cover plate 140 are at least partially connected in the interruption region 1442. When pressure relief occurs, the current collecting member 130 applies tension to the cover plate 140, further preventing the pressure relief region 145 from flying out.

[0058] See also Figure 3 In one example of the secondary battery 100 of the present invention, the distance a from the weak portion 144 to the inner side of the sidewall 112 along the radial direction of the secondary battery 100 is defined as "a," and a is further specified to be greater than or equal to 2 mm. This specified range can reduce the thermal impact on the weak portion 144 during welding of the stopper 143 and the sidewall 112, preventing thermal deformation of the weak portion 144 that could affect the welded connection between the cap plate 140 and the current collecting member 130.

[0059] See also Figure 3 In one example of the secondary battery 100 of the present invention, the weak portion 144 is a notch or a thinned structure, and the notch or thinned structure is disposed on the side of the bottom wall 1421 facing away from the electrode assembly 120. That is, the notch or thinned structure is disposed on the outer side of the cover plate 140. This arrangement facilitates processing and also facilitates controlling the distance between the second weld mark 146 and the weak portion 144 during welding. Moreover, because the weak portion 144 is located within the recess 142, it is well protected and not easily damaged.

[0060] Considering that machining the weak portion 144 will damage the nickel plating on the surface of the cover plate 140, in one embodiment of the secondary battery 100 of the present invention, a corrosion-resistant layer is provided on the surface of the weak portion 144. This provides rust and corrosion protection for the weak portion 144, alleviating the problem of thinner weak portions 144 being more susceptible to damage due to rust and corrosion, thereby extending the service life of the secondary battery 100.

[0061] See also Figure 7 The present invention further provides a battery pack 10, which includes any of the aforementioned secondary batteries 100. In one embodiment of the present invention's battery pack 10, the battery pack 10 includes a housing 101, a housing cover 102, and a plurality of secondary batteries 100. The plurality of secondary batteries 100 are placed in the housing 101 and are connected in series or in parallel, or in a combination of series and parallel. The housing cover 102 seals the housing 101 to protect the plurality of secondary batteries 100. It should be noted that, in addition to the present invention's secondary batteries 100, the battery pack 10 may also include a battery pack 10 thermal management system, a circuit board, and other components. The battery pack 10 may be a battery module, a battery pack, an energy storage cabinet, or the like; these will not be described in detail here.

[0062] See also Figure 8 The present invention also provides an electronic device 1, which includes the above-mentioned battery pack 10. The working part 11 is electrically connected to the battery pack 10 to obtain electrical energy support. As an example, the electronic device 1 is a vehicle, and the vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc., but is not limited to this. The working part 11 is the vehicle body, and the battery pack 10 is arranged at the bottom of the vehicle body and provides electrical energy support for the driving of the vehicle or the operation of electrical components in the vehicle. However, in some other embodiments, the electronic device 1 can also be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. Spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.; the working part 11 can be a unit component that can obtain electrical energy from the battery pack 10 and perform corresponding work, such as a fan blade rotation unit, a vacuum cleaner suction unit, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys; electric tools include metal cutting tools, grinding tools, assembly tools, and railway tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The present embodiment does not impose any particular restrictions on the electronic device 1.

[0063] The secondary battery of the present invention positions the weak portion on the recessed bottom wall, preventing direct contact between the weak portion and the outside world. The recess also provides protection for the weak portion, reducing the risk of damage or rupture during transportation and use. Furthermore, a pressure relief area is formed around the weak portion. Because the recess is located on the outer periphery of the cover plate, a larger pressure relief area is provided, which helps increase the sensitivity of the weak portion and improves pressure relief efficiency. Therefore, the present invention effectively overcomes some practical problems in the prior art and thus has high utility value and practical significance. The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by persons of ordinary skill in the art without departing from the spirit and technical principles disclosed herein shall be covered by the claims of the present invention.

Claims

1. A secondary battery, characterized in that: include: The housing comprises an end wall and a side wall surrounding the end wall, wherein an opening is formed at one end of the side wall facing away from the end wall; an electrode assembly, housed in the housing; a current collecting member, disposed at one end of the electrode assembly facing the opening, the current collecting member being electrically connected to the electrode assembly; a cover plate, covering and sealing the opening, wherein the outer periphery of the cover plate is surrounded by a convex portion protruding toward the interior of the shell, the convex portion is formed into a recess on a side facing away from the electrode assembly, and the outer side of the convex portion is surrounded by a limiting portion, the limiting portion extending radially outward from the cover plate and fixedly connected to the end surface of the opening; A weak portion is provided on the bottom wall of the depression, a pressure relief area is formed around the weak portion, and the weak portion is configured to break when the internal pressure of the secondary battery exceeds a threshold value.

2. The secondary battery according to claim 1, wherein The current collecting member is welded to the electrode assembly and forms a first weld mark. Along the height direction of the secondary battery, the projection of the pressure relief area on the current collecting member covers at least 80% of the first weld mark.

3. The secondary battery according to claim 1, wherein The current collecting member is welded to the cover plate and forms a second weld mark, and at least 50% of the second weld mark falls into the pressure relief area.

4. The secondary battery according to claim 3, wherein The weak portion includes a continuous area and a discontinuous area, and the pressure relief area is configured to break along the continuous area and fold toward the outside of the shell when the pressure in the shell exceeds a threshold.

5. The secondary battery according to claim 4, wherein The second weld mark at least partially coincides with the bottom wall where the interruption area is located.

6. The secondary battery according to claim 1, wherein Along the radial direction of the secondary battery, a distance from the weak portion to the inner side of the side wall is greater than or equal to 2 mm.

7. The secondary battery according to claim 1, wherein The weak portion is a notch or a thinned structure, and the notch or the thinned structure is arranged on a side of the bottom wall away from the electrode assembly.

8. The secondary battery according to claim 1, wherein The surface of the weak portion is provided with a corrosion-resistant layer.

9. A battery pack, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 8.

10. An electronic device, characterized in that: A battery pack comprising the battery pack according to claim 9.

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