Secondary batteries, battery packs, and electronic devices

Abstract

This invention provides a secondary battery that improves upon the problem of internal material discharge being hindered by the current collector when the secondary battery experiences a loss of thermal control. [Solution] A secondary battery, a battery pack, and an electronic device are provided, the secondary battery comprising a casing, an electrode assembly, and a current collector. The casing includes an end wall, on which an explosion-proof valve is installed. The electrode assembly is housed within the casing and includes a tab facing the end wall. The current collector is positioned between the electrode assembly and the end wall and is electrically connected to the tab. The current collector has a weak point, configured to rupture when the internal pressure of the secondary battery exceeds a threshold, with a portion of the current collector bending away from the electrode assembly to reduce the isolation to the reduced pressure region. Along the radial direction of the current collector, if the span of the weak point is a, the minimum central angle passing through the center of the current collector and covering the weak point is α, and the minimum radial width of the region covered by the current collector at angle α is b, then 0.4b ≤ a ≤ 0.9b.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, specifically to secondary batteries, battery packs and electronic devices.

Background Art

[0002] In the prior art, in order to ensure the normal pressure reduction of the secondary battery and reduce the risk of battery explosion, the structure is usually such that one or two end walls of the casing have explosion-proof valves. When the pressure in the casing exceeds the threshold value, the explosion-proof valve opens, and when the secondary battery generates a situation where thermal control is impossible, the explosion-proof valve opens to enable the discharge of the internal substances of the secondary battery. Even when the explosion-proof valve opens smoothly when the secondary battery generates a situation where thermal control is impossible, the current collecting member still causes a great hindrance to the discharge of the internal substances of the secondary battery, which will reduce the safety of the secondary battery.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The present invention provides a secondary battery, a battery pack and an electronic device, which improve the technical problem that the discharge of internal substances is hindered by the current collecting member when the secondary battery generates a situation where thermal control is impossible.

Means for Solving the Problems

[0004] To achieve the above-mentioned objectives and other related objectives, the present invention provides a secondary battery, a battery pack and an electronic device, the secondary battery comprising a casing, an electrode assembly and a current collector. The casing includes an end wall on which an explosion-proof valve is installed. The electrode assembly is housed within the casing and includes a tab facing the end wall. The current collector is installed between the electrode assembly and the end wall and is electrically connected to the tab, and the current collector has at least one weak point, which is configured to rupture when the internal pressure of the secondary battery exceeds a threshold, so that at least a portion of the current collector bends away from the electrode assembly, reducing the blockage to the reduced pressure region. Along the radial direction of the current collector, if the span of the weak point is a, the minimum central angle passing through the center of the current collector and covering the weak point is α, and the minimum radial width of the region covered by the current collector at angle α is b, then 0.4b ≤ a ≤ 0.9b.

[0005] In the above-described technical solution, the current collector member is provided with at least one weak point, which is configured to rupture when the internal pressure of the secondary battery exceeds a threshold, and at least a portion of the current collector member is bent away from the electrode assembly, reducing the blockage to the pressure-reducing region on the end wall. The radial span of the weak point in the current collector is defined as a, that is, the distance from the point furthest from the center of the current collector to the point closest to the center of the current collector in the weak point. Considering the possibility that the outer circumference of the current collector may have various shapes, the minimum central angle α that passes through the center of the current collector and covers the weak point is defined, and the minimum radial width of the region covered by the current collector at angle α is defined as b, that is, the minimum radial width of the actual portion of the current collector covered by the weak point, and is limited to 0.4b ≤ a ≤ 0.9b. This installation prevents the weak point from penetrating the current collector radially, prevents the current collector from splitting into multiple pieces due to the weak point, and at the same time strengthens the structural strength of the current collector, improves the flatness of the current collector, reduces the difficulty of welding the current collector and tab, and improves the reliability of the welded connection.

[0006] In one embodiment of the secondary battery of the present invention, if R1 is the maximum distance from the weak point to the center of the current collector along the radial direction of the current collector, and R2 is the minimum distance from the explosion-proof valve to the center of the end wall, then R2 - R1 ≤ 3 mm.

[0007] In the above-described technical solution, limiting R2-R1 ≤ 3mm means that the maximum distance between the pressure-reducing region formed on the current collector after a portion of the current collector is folded back and the pressure-reducing region formed on the end wall after the explosion-proof valve is opened is limited to 3mm or less, thereby enabling fracture folding at a greater limit of the weak point and further reducing the obstruction to the discharge of internal materials.

[0008] In one embodiment of the secondary battery of the present invention, the current collector member includes a center hole, and if the minimum distance from the weak portion to the edge of the center hole is c, then c ≤ 2 mm.

[0009] In the above-described technical plan, having c ≤ 2 mm, that is, the distance between the point closest to the center hole of the weak point and the center hole itself being 2 mm or less, is advantageous for improving the depressurization effect by taking advantage of the fact that one end of the weak point closest to the center hole is more likely to rupture during depressurization.

[0010] In one embodiment of the secondary battery of the present invention, R2-R1≧c.

[0011] In the above-described technical solution, setting R2-R1≧c can be understood as limiting the distance between the point closest to the center hole of the weak point and the center hole to be less than or equal to the distance between the point closest to the explosion-proof valve of the weak point and the explosion-proof valve. This setting ensures the flatness and structural strength of the current collector member, while simultaneously making the end closest to the center hole of the weak point more prone to tearing during depressurization. This creates an effect of folding back from the inside to the outside along the radial direction of the current collector member, which is advantageous for improving the depressurization effect.

[0012] In one embodiment of the secondary battery of the present invention, there are multiple vulnerable parts, and at least one of the multiple vulnerable parts is not in communication with any of the other vulnerable parts.

[0013] In the above-described technical solution, by installing the current collector so that none or only a small number of weak points are connected to each other, it is possible to prevent the current collector from easily fracturing at the points where multiple weak points of the current collector are connected during transportation or welding processes. Furthermore, it is possible to improve the structural strength and surface flatness of the current collector, and it is possible to reduce the difficulty of welding the current collector and tab, thereby improving the reliability of the welded connection.

[0014] In one embodiment of the secondary battery of the present invention, there are at least three weak points, all of which are distributed along the circumferential direction of the current collector, and if β is the rotation angle of the outermost radial contour of the space between two adjacent weak points, then β ≤ 120°.

[0015] In the above-described technical solution, having at least three weak points makes it possible to divide the current collector member into at least three of the above-mentioned spacing regions along its circumferential direction. The spacing region is the part between two adjacent weak points on the circumferential direction of the current collector member. After a weak point ruptures under the action of internal pressure, the spacing region can fold back from the inside to the outside, reducing the shielding of the end wall to the depressurized region. Three or more weak points are more advantageous for folding back after rupture compared to the case of one or two weak points, and the smaller the angle of rotation, the easier the folding back becomes. Limiting β ≤ 120° is advantageous for folding back the spacing region on one side, and on the other side, it makes the distribution of weak points more uniform, further equalizes the force acting on the spacing region, is advantageous for the synchronous rupture of weak points, and reduces the probability that the folding back of individual spacing regions will not be successful.

[0016] In one embodiment of the secondary battery of the present invention, a current collector and a casing are welded together to form at least one first weld mark, and two points located on both sides of the first weld mark in the circumferential direction along the circumferential direction of the current collector are connected to the center of the current collector to form a central angle γ, and the region enclosed by each weak point or the space between two adjacent weak points can form a bent portion when the internal pressure of the secondary battery exceeds a threshold, the minimum central angle that passes through the center of the current collector and covers the bent portion is δ, and each δ central angle and the γ central angle overlap at least partially.

[0017] In the above-described technical solution, the space between two adjacent weak points can form a bent section under the action of internal pressure exceeding a threshold, and if the weak point is in the shape of a broken line or curve, the area it encloses can also form a bent section under the action of internal pressure exceeding a threshold. Furthermore, limiting the overlap of each δ central angle and γ central angle to at least a portion allows at least a part of the welded portion between the current collector and the casing to act as a pivot point for the bending section when the bending section folds outward. This configuration is advantageous for the smooth folding of the bending section and further improves the safety of the secondary battery.

[0018] In one embodiment of the secondary battery of the present invention, the minimum distance between the first weld mark and the weak point is 1 mm or more.

[0019] In the above-described technical solution, this installation allows for a safety distance of 1 mm or more between the weak point and the first weld mark, preventing problems such as explosion points and weld penetrations from occurring during the welding process of the current collector member to the casing, thereby reducing hidden safety hazards and improving welding quality.

[0020] In one embodiment of the secondary battery of the present invention, a current collector and a tab are welded together to form at least one second weld mark, and the minimum distance between the second weld mark and the weak point is 1 mm or more.

[0021] In the above-described technical solution, this installation allows for a safety distance of 1 mm or more between the weak point and the second weld mark, preventing problems such as explosion points and weld penetrations from occurring during the welding process of the current collector member to the tab, thereby reducing hidden safety hazards and improving welding quality.

[0022] The present invention also provides a battery pack comprising a secondary battery as described in any one of the above.

[0023] The present invention also provides an electronic device, which includes the aforementioned battery pack.

Advantages of the Invention

[0024] In the secondary battery of the present invention, a plurality of fragile portions are provided on the current collector member. The fragile portions are configured to break when the internal pressure of the secondary battery exceeds a threshold value. At least a part of the current collector member bends in a direction away from the electrode assembly, reducing the shielding of the pressure reduction region on the end wall. Define the distance from the point farthest from the center of the current collector member of the fragile portion to the point closest to the center of the current collector member of the fragile portion as a, that is, define the span of the fragile portion in the radial direction of the current collector member as a. Considering the possibility that the outer periphery of the current collector member has various shapes, further define the minimum central angle α that covers the fragile portion through the center of the current collector member. Define the minimum radial width of the region covered by the α angle of the current collector member as b, that is, define the minimum radial width of the entity of the portion covered by the fragile portion on the current collector member as b, and limit it to 0.4b ≤ a ≤ 0.9b. This installation can prevent the fragile portion from penetrating the current collector member along the radial direction, affect the structural strength of the current collector member, and further make the current collector member prone to cracking into a plurality of independent structures by the fragile portion during the transportation and welding processes, preventing it from affecting the flatness of the entire current collector member. This installation can enhance the structural strength of the current collector member, enable the current collector member to have a higher flatness, reduce the difficulty of welding the current collector member and the tab, and improve the reliability of the welded connection.

[0025] To more clearly explain the technical solutions in the embodiments of the present invention or the prior art, the attached drawings that need to be used in the description of the embodiments or the prior art will be briefly introduced below. It is obvious that the attached drawings in the following description are only some embodiments of the present invention, and those skilled in the art can also obtain other embodiments based on these attached drawings without creative labor.

Brief Description of the Drawings

[0026] [Figure 1] It is a schematic diagram of the overall structure of an embodiment of the secondary battery of the present invention. [Figure 2] It is a schematic diagram of the electrode assembly structure of an embodiment of the secondary battery of the present invention. [Figure 3]This is a schematic diagram of the welding of the first current collector member and the electrode assembly of an embodiment of the secondary battery of the present invention. [Figure 4] This is a schematic diagram of the welding of the first current collector member and the electrode assembly of another embodiment of the secondary battery of the present invention. [Figure 5] This is a schematic diagram of an embodiment of the battery pack of the present invention. [Figure 6] This is a schematic diagram of an embodiment of the electronic device of the present invention.

Embodiments for Carrying Out the Invention

[0027] Hereinafter, embodiments of the present invention will be described through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.The present invention can be further implemented or applied in other different specific embodiments, and various modifications or changes can be made without departing from the spirit of the present invention based on different viewpoints and applications of each item in this specification.It should be noted that, without contradiction, the following examples and the features in the examples can be combined with each other.Also, it should be understood that the terms used in the embodiments of the present invention are for describing specific specific implementation scenarios and are not for limiting the protection scope of the present invention.Test methods not specifically specified in the following examples are usually carried out according to normal conditions or according to the conditions recommended by each manufacturer.

[0028] In this embodiment, when a numerical range is shown, it should be understood that, unless otherwise explained in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints can be selected.Unless otherwise defined, all technical and scientific terms used in the present invention, together with the understanding of the existing technology by those skilled in the art and the description of the present invention, can be used to implement the present invention using any method, equipment, and material of the existing technology similar or equivalent to the methods, equipment, and materials in the embodiments of the present invention.

[0029] Furthermore, terms such as "up," "down," "left," "right," "middle," and "one" used herein are merely for the purpose of clarifying the description and are not used to limit the scope within which the present invention can be implemented. Any changes or adjustments to their relative relationships are considered to fall within the scope within which the present invention can be implemented, provided that there is no substantial change in the technical content.

[0030] A secondary battery includes a casing and an electrode assembly, the electrode assembly being housed within the casing, and the electrode assembly being the component in the secondary battery where electrochemical reactions occur. The casing can contain one or more electrode assemblies.

[0031] Electrode assemblies are primarily formed by winding or stacking positive and negative electrode plates, with a separator typically placed between them. The positive electrode plate includes a positive electrode current collector and a positive electrode active material, which is coated on the surface of the positive electrode current collector. The positive electrode current collector includes a coated area with the active material and an uncoated area where the active material is not applied, with the uncoated area forming the positive electrode tab of the electrode assembly after winding. The negative electrode plate includes a negative electrode current collector and a negative electrode active material, which is coated on the surface of the negative electrode current collector. The negative electrode current collector includes a coated area with the active material and an uncoated area where the active material is not applied, with the uncoated area forming the negative electrode tab of the electrode assembly after winding.

[0032] The secondary battery further includes a current collector positioned between the end wall of the casing and the corresponding end face of the electrode assembly, the current collector being welded to a positive or negative electrode tab to form a tab connection, and explosion-proof valves configured on one or two end walls of the casing, allowing the valves to open and discharge internal materials of the battery when the battery experiences thermal uncontrollability.

[0033] However, the inventors discovered that when a secondary battery experiences thermal uncontrollability, even if the explosion-proof valve opens smoothly, the current collector still significantly obstructs the discharge of internal materials from the secondary battery, thereby reducing the safety of the secondary battery. To solve this problem, in some current collectors, the inventors have made it possible to reduce the obstruction to the discharge of internal materials by cutting off adjacent tab connections of the current collector and folding them back when the pressure is reduced. However, this installation reduces the overall strength of the current collector, affects the flatness of the current collector, increases the difficulty of welding the current collector and tab, and reduces the reliability of the welded connection between the current collector and tab.

[0034] In view of this, the present invention provides a technical solution in which a plurality of weak points are provided on the current collector member, and the weak points are configured to rupture when the internal pressure of the secondary battery exceeds a threshold, and at least a portion of the current collector member is bent away from the electrode assembly, reducing the blockage to the reduced pressure region on the end wall, and improving the technical problem in which the discharge of internal material when the secondary battery becomes uncontrollable by heat is obstructed by the current collector member.

[0035] Referring to Figures 1 to 6, the present invention provides a type of secondary battery 100, which includes a casing 110, an electrode assembly 120, an electrode column 130, and a current collector.

[0036] Referring to Figure 1, the casing 110 includes end walls, and specifically, in this embodiment, the casing 110 includes a first end wall 114 and a second end wall 111 installed opposite each other, and a side wall 112 surrounding the first end wall 114 and the second end wall 111. To ensure normal depressurization of the secondary battery 100 and reduce the risk of explosion of the secondary battery 100, an explosion-proof valve 115 is usually installed on the first end wall 114 and / or the second end wall 111, and the shape of the explosion-proof valve 115 can be circular, petal-shaped, rectangular, elliptical, polygonal or other irregular shape, and the explosion-proof valve 115 may be a closed shape or an open shape, and the explosion-proof valve 115 may have notches or a thin-walled structure, etc., but is not limited thereto, as long as the explosion-proof valve 115 can open when the internal pressure of the secondary battery 100 reaches a threshold, forming a depressurization region and performing depressurization, thereby achieving directional detonation of the secondary battery 100.

[0037] Referring to Figure 1, the connections between the first end wall 114 and the side wall 112, and between the second end wall 111 and the side wall 112 can be realized in various ways, as long as a stable sealing and electrical connection relationship can be formed, for example, by integral press molding, integral casting, or partial welding. The enclosure of the side wall 112 is not limited and can be cylindrical or prismatic, or it can be enclosed along any other closed loop contour that can fit the first end wall 114 and the second end wall 111. In one embodiment, the outer edges of the first end wall 114 and the second end wall 111 are circular, the side wall 112 cylindrically encloses the outer edges of the first end wall 114 and the second end wall 111, the second end wall 111 and the side wall 112 are integrally molded, and a circular opening 113 is formed at one end of the side wall 112 closest to the first end wall 114. A housing chamber is formed within the casing 110, which is enclosed by the second end wall 111 and the side wall 112, and is used to house the electrode assembly 120, electrolyte, and other necessary battery components. Specifically, the diameter size of the casing 110 can be determined based on the specific dimensions of the electrode assembly 120, such as 18 mm, 21 mm, or 46 mm. The material of the casing 110 can be various, such as copper, iron, aluminum, steel, or aluminum alloy. To prevent the casing 110 from rusting during long-term use, a layer of rust-preventive material such as metallic nickel can be plated onto the surface of the casing 110.

[0038] Referring to Figures 1 and 2, the electrode assembly 120 is housed within the casing 110 and includes tabs facing the end walls. Specifically, the electrode assembly 120 is the component in the secondary battery 100 where the electrochemical reaction occurs. The casing 110 may contain one or more electrode assemblies 120. The electrode assembly 120 includes a wound structure 126 formed by stacking and winding a first electrode plate 123, a second electrode plate 121, and a separator 122. The polarities of the first electrode plate 123 and the second electrode plate 121 are opposite, with the first electrode plate 123 being the positive electrode plate and the second electrode plate 121 being the negative electrode plate in some embodiments, and the first electrode plate 123 being the negative electrode plate and the second electrode plate 121 being the positive electrode plate in some other embodiments.

[0039] Referring to Figures 1 and 2, in this embodiment, the first electrode plate 123 is a negative electrode plate and includes a negative electrode current collector 1231 and a negative electrode active material, the negative electrode active material being applied to the surface of the negative electrode current collector 1231. The negative electrode current collector 1231 includes a first coated region 1232 to which the active material is applied and a first uncoated region 1233 to which the active material is not applied, the first uncoated region 1233 being located at the end of the first electrode plate 123 and the first uncoated region 1233 extending from the separator 122 along the winding axis of the electrode assembly 120 and formed by bending toward the winding axis, the first tab 124 being the corresponding negative electrode tab.

[0040] Referring to Figures 1 and 2, the second electrode plate 121 is a positive electrode plate, specifically comprising a positive electrode current collector 1211 and a positive electrode active material, the positive electrode active material being coated on the surface of the positive electrode current collector 1211. The positive electrode current collector 1211 comprises a second coated region 1212 to which the active material is coated and a second uncoated region 1213 to which the active material is not coated, the second uncoated region 1213 located at the end of the second electrode plate 121, and the second uncoated region 1213 extends from the separator 122 along the other end of the electrode assembly 120 in the winding axis direction and is formed by bending toward the winding axis, the second tab 125 being the corresponding positive electrode tab.

[0041] Referring to Figures 1 and 2, the separator 122 is placed between the first electrode plate 121 and the second electrode plate 123, separating the positive electrode active material layer from the negative electrode active material layer. Taking lithium-ion secondary battery 100 as an example, the material of the positive electrode current collector 1211 can be aluminum, and the positive electrode active material layer contains a positive electrode active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The material of the negative electrode current collector 1231 can be copper, and the negative electrode active material layer contains a negative electrode active material, which can be carbon or silicon, etc. The substrate material of the separator 122 can be polypropylene (PP) or polyethylene (PE), etc. To provide protection and insulation to the battery core, an insulating film can be coated on the outside of the battery core. This insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other polymer materials.

[0042] Referring to Figures 1 and 2, if the first tab 124 faces the first end wall 114 or the second end wall 111, the second tab 125 faces the other end of the casing 110. In this embodiment, the second tab 125 faces the second end wall 111 and is electrically connected to the pole column 130, making the pole column 130 positively charged. The first tab 124 faces the first end wall 114, and the casing 110 and the first tab 124 are electrically connected, thereby becoming negatively charged. However, in other embodiments, the first tab 124 can be connected to the pole column 130 and the second tab 125 can be connected to the casing 110.

[0043] Referring to Figures 1 and 2, the electrode column 130 penetrates the second end wall 111 and is insulated from the second end wall 111. The structural form of the electrode column 130 can be any suitable form that penetrates the second end wall 111 and is electrically connected to the first electrode plate 123 or the second electrode plate 121, for example the cross section can be circular, square, prismatic or an irregularly shaped contour that can achieve stable conductivity, and one end of the electrode column 130 facing the electrode assembly 120 penetrates the second end wall 111 and is directly or indirectly electrically connected to the first tab 124 or the second tab 125, for example the electrode column 130 is The electrode column 130 can be indirectly electrically connected to the first electrode plate 123 through an electrical component, and one end of the electrode column 130 away from the electrode assembly 120 is exposed to the outside of the casing 110 to form a corresponding electrode. The electrode column 130 can be positive or negative. For example, in one embodiment, the electrode column 130 is electrically connected to the first electrode plate 123, and if the polarity of the first electrode plate 123 is positive, the electrode column 130 is positive and the casing 110 forms a corresponding negative electrode. In another embodiment, if the polarity of the first electrode plate 123 is negative, the electrode column 130 is negative and the casing 110 forms a corresponding positive electrode. In this embodiment, a mounting hole for the electrode column 130 is provided on the second end wall 111, and the electrode column 130 is sealed and insulated and mounted inside the mounting hole. The electrode column 130 is indirectly electrically connected to the second tab 125 through a current collector. To facilitate distinction and understanding, the current collector that is electrically connected to the second tab 125 is named the second current collector 150. One end of the electrode column 130 that is away from the electrode assembly 120 is exposed to the outside of the casing 110 and is positively charged. The second current collector 150 is connected to the positive electrode tab, and it is preferable to select aluminum metal as the material.

[0044] The electrode column 130 is made of a conductive metallic material. The material of the electrode column 130 can be aluminum. If the material of the electrode column 130 is aluminum, the riveting process can be easily carried out. In this embodiment, the material of the electrode column 130 is aluminum and its polarity is positive, and corresponding to the electrode column 130, the material of the casing 110 is low carbon steel and correspondingly forms the negative electrode, and the electrode column 130 and the casing 110 are electrically insulated. Electrical insulation between the electrode column 130 and the second end wall 111 of the casing 110 can be achieved in various ways. For example, insulation can be achieved by placing an insulating washer between the electrode column 130 and the second end wall 111. Alternatively, insulation can be achieved by forming an insulating coating layer on a portion of the electrode column 130. Alternatively, a combination of some of the above methods can be applied.

[0045] Furthermore, referring to Figure 1, the electrode assembly 120 is electrically connected to the casing 110 through a current collector. Specifically, the current collector is welded to the first tab 124. For the sake of distinction and understanding, the current collector electrically connected to the first tab 124 is named the first current collector 140. While ultrasonic welding, resistance welding, laser welding, etc., can be used for the welding method, the invention is not limited to these. In this embodiment, laser welding is used, and the first current collector 140 is connected to the negative electrode tab. It is preferable to select copper metal as the material. It needs to be explained that the shapes of the first current collector 140 and the second current collector 150 can be any rotationally symmetrical shape, such as a circle, square, regular polygon, petal shape, or any other shape having a center of symmetry that can overlap with the original shape after being rotated by a certain angle around the center of symmetry, but is not limited to this, as long as it can realize a stable and reliable electrical connection relationship, the centers of the first current collector 140 and the second current collector 150 are their own centers of symmetry. In order to improve positioning, ease of processing, interchangeability and uniformity during the installation process of the current collectors, both the first current collector 140 and the second current collector 150 in this embodiment adopt a circular structure.

[0046] Referring to Figures 3 and 4, at least one vulnerable portion 141 is provided on the current collector member, and depending on whether the explosion-proof valve 115 is installed on the first end wall 114 or the second end wall 111, the vulnerable portion 141 may be installed on the first current collector member 140 or on the second current collector member 150. In some embodiments, when the explosion-proof valve 115 is installed on the first end wall 114, the vulnerable portion 141 is installed on the first current collector member 140. In some other embodiments, when the explosion-proof valve 115 is installed on the second end wall 111, the vulnerable portion 141 is installed on the second current collector member 150. In some further embodiments, when the explosion-proof valve 115 is installed on both the first end wall 114 and the second end wall 111, the vulnerable portion 141 is installed in both the first current collector member 140 and the second current collector member 150. The number of weak points 141 is not limited and can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or more; the shape of the weak points 141 can be varied, for example, a straight line, a curve (wavy line, arc line, sine curve, etc.), a broken line, other irregular shapes, or a variety of combinations thereof; the structure of the weak points 141 can be notched, thinned, perforated, or a combination of two or more of the above; however, the above is not limited, as long as the weak points 141 of the secondary battery 100 rupture when the internal pressure of the secondary battery 100 exceeds a threshold, at least a part of the current collector bends away from the electrode assembly 120, reducing shielding to the depressurized area on the adjacent first end wall 114 or second end wall 111, allowing the material inside the secondary battery 100 to be smoothly discharged, thereby achieving directional detonation of the secondary battery 100.

[0047] Furthermore, referring to Figures 3 and 4, along the radial direction of the first current collector 140, the distance from the furthest point of the weak portion 141 away from the center of the first current collector 140 to the nearest point of the weak portion 141 away from the center of the first current collector 140 is defined as a, that is, the span of the weak portion 141 in the radial direction of the first current collector 140 is defined as a, and considering the possibility that the outer circumference of the first current collector 140 may have various shapes, the minimum central angle α that passes through the center of the first current collector 140 and covers the weak portion 141 is defined as b, and the minimum radial width of the region covered by angle α of the first current collector 140 is defined as b. By defining b as the minimum radial width of the actual portion covered by the weak portion 141 on the first current collector member 140, and limiting it to 0.4b ≤ a ≤ 0.9b, it can be, for example, 0.4b, 0.5b, 0.6b, 0.7b, 0.8b, or 0.9b. This configuration allows the weak portion 141 to penetrate the current collector member radially, preventing the current collector member from splitting into multiple pieces due to the weak portion 141. At the same time, it can enhance the structural strength of the current collector member, improve the flatness of the current collector member, reduce the difficulty of welding the current collector member and tab, and improve the reliability of the welded connection.

[0048] Referring to Figures 3 and 4, in one embodiment of the secondary battery 100 of the present invention, an explosion-proof valve 115 is installed on the first end wall 114 and a vulnerable portion 141 is installed on the first current collector member 140. The maximum distance from the vulnerable portion 141 to the center of the first current collector member 140 along the radial direction of the first current collector member 140 is R1, and the minimum distance from the explosion-proof valve 115 to the center of the first end wall 114 is R2, with R2-R1 ≤ 3 mm. That is, the pressure reduction region formed on the first current collector member 140 after a part of the first current collector member 140 is folded back and the explosion-proof valve The maximum distance between the valve 115 and the pressure-reducing region formed on the end wall after it opens is limited to 3 mm or less. R2 may be greater than or less than R1. When R2 > R1, the value of R2-R1 can be 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm, etc. When R2 ≤ R1, the value of R2-R1 can be -3 mm, -2 mm, -1 mm, 0 mm, etc. All of the above installations can achieve a greater limit of folding after the rupture of the weak part 141 and further reduce the obstruction to the discharge of internal material. It should be explained that the explosion-proof valve 115 shown in Figures 3 and 4 is actually located on the first end wall 114. To make it easier to understand the positional relationship between the explosion-proof valve 115 and the weak part 141, the explosion-proof valve 115 is projected onto the current collector. In this embodiment, the first end wall 114 and the current collector are installed coaxially.

[0049] Referring to Figures 3 and 4, in one embodiment of the secondary battery 100 of the present invention, the first current collector 140 includes a center hole 144, and the minimum distance from the fragile portion 141 to the edge of the center hole 144 is c, preferably c ≤ 2 mm, and can be, for example, 0.2 mm, 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, or 2 mm, where c ≤ 2 mm, that is, the distance between the position of the fragile portion 141 closest to the center hole 144 and the center hole 144 is 2 mm or less. This arrangement is advantageous because one end of the fragile portion 141 closest to the center hole 144 is more likely to break when the pressure is reduced, which is advantageous for improving the pressure reduction effect.

[0050] Referring to FIGS. 3 and 4, in one embodiment of the secondary battery 100 of the present invention, preferably, R2 - R1 ≧ c, and since R2 - R1 is a variable with c greater than 0, it can be first seen that R1 < R2. This arrangement enables the first current collector member 140 to have relatively high structural strength and flatness. Next, the arrangement of R2 - R1 ≧ c is understood to limit that the distance between the position closest to the center hole 144 of the vulnerable part 141 and the center hole 144 is less than or equal to the distance between the position closest to the explosion-proof valve 115 of the vulnerable part 141 and the explosion-proof valve 115. The specific value of R2 - R1 is determined by the value of c. This arrangement can ensure the flatness and structural strength of the current collector member, and at the same time, can realize that one end closer to the center hole 144 of the vulnerable part 141 is more likely to break during decompression, forming an effect of folding back from the inside to the outside along the radial direction of the current collector member. This arrangement is more advantageous for improving the decompression effect.

[0051] Referring to FIGS. 3 and 4, in one embodiment of the secondary battery 100 of the present invention, at least one of the plurality of vulnerable parts 141 is not in communication with any of the other vulnerable parts 141. By arranging such that none of the plurality of vulnerable parts 141 communicate with each other or the communication is minimized, it is possible to prevent easy breakage at the communication portions of the plurality of vulnerable parts 141 of the first current collector member 140 during transportation or welding processes. Also, the structural strength and surface flatness of the first current collector member 140 can be improved. Further, the difficulty of welding the first current collector member 140 and the tab can be reduced, and the reliability of the welded connection can be improved. In one embodiment, referring to FIG. 3, there is no communication between the plurality of vulnerable parts 141 along the circumferential direction of the first current collector member 140.

[0052] Referring to Figures 3 and 4, in one embodiment of the secondary battery 100 of the present invention, the multiple weak points 141 are distributed along the circumferential direction of the first current collector member 140, the number of weak points 141 is at least 3, and can be, for example, 3, 4, 5, 6, 7, 8, 9 or more, and the rotation angle of the radial outermost contour of the spacing region between two adjacent weak points 141 is denoted as β. It should be explained that the spacing region is the portion between two adjacent weak points 141 on the circumferential direction of the first current collector member 140, and the rotation angle β ≤ 120°, and can be, for example, 30°, 45°, 60°, 75°, 90°, 100°, 115° or 120°. Having at least three weak points 141 allows the first current collector 140 to be divided into at least three of the above-mentioned spacing regions along its circumferential direction. After a weak point 141 ruptures under the action of internal pressure, the spacing region can fold back from the inside to the outside, reducing shielding of the end wall to the depressurized region. Three or more weak points 141 are more advantageous for folding back after rupture compared to the case of one or two weak points 141, and folding becomes easier as the rotation angle β is smaller. Limiting β ≤ 120° is advantageous for folding back the spacing region, on the one hand, and on the other hand, the distribution of weak points 141 becomes more uniform, the force acting on the spacing region becomes more uniform, which is advantageous for the synchronous rupture of weak points 141, and the probability of individual spacing regions failing to fold back is reduced.

[0053] Referring to Figures 3 and 4, in one embodiment of the secondary battery 100 of the present invention, the first current collector 140 and the casing 110 are welded together to form at least one first weld mark 142, and along the circumferential direction of the first current collector 140, two points located on both sides of the first weld mark 142 are connected to the center of the first current collector 140 to form a central angle γ, and the region surrounded by each weak part 141 or the space between two adjacent weak parts 141 can form a bent part 145 when the internal pressure of the secondary battery 100 exceeds a threshold. It is necessary to explain that when the weak part 141 is of the linear type shown in Figure 3, the space between two adjacent weak parts 141 can form a bent part 145 under the action of internal pressure exceeding a threshold, and when the weak part 141 is of the folded type shown in Figure 4, the region surrounded by the weak part 141 itself can also form a bent part 145 under the action of internal pressure exceeding a threshold. Furthermore, a minimum central angle δ is defined that passes through the center of the first current collector member 140 and covers the bent portion 145. Preferably, each δ central angle and γ central angle are limited to at least partially overlapping. This configuration ensures that when the bent portion 145 folds outward, at least a portion of the welded portion between the first current collector member 140 and the casing 110 acts as a pivot point for the bending portion 145. This configuration is advantageous for the smooth folding of the bent portion 145 and further improves the safety of the secondary battery 100.

[0054] Referring to Figures 3 and 4, in one embodiment of the secondary battery 100 of the present invention, the minimum distance between the first weld mark 142 and the weak point 141 is 1 mm or more, and this distance is indicated by W1 as shown in Figures 3 and 4, and is, for example, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, or 4 mm. This setup ensures that the weak point 141 and the first weld mark 142 are at least 1 mm apart, preventing problems such as explosion points and weld penetrations during the welding process of the first current collector 140 and the casing 110, reducing hidden safety hazards, and improving welding quality.

[0055] Referring to Figures 3 and 4, in one embodiment of the secondary battery 100 of the present invention, the first current collector 140 and the tab are welded together to form at least one second weld mark 143, and the minimum distance between the second weld mark 143 and the weak point 141 is 1 mm or more, which is indicated by W2 in Figures 3 and 4, and is, for example, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, or 4 mm. With this setup, the weak point 141 and the second weld mark 143 can have a safety distance of 1 mm or more, preventing the occurrence of problems such as explosion point and weld penetration during the welding process of the first current collector 140 and the tab, reducing hidden safety hazards and improving welding quality.

[0056] It is necessary to explain that the above technical solution also applies when an explosion-proof valve 115 is installed on the second end wall 111 and a vulnerable part 141 is installed on the second current collector 150. Although the specific structure will not be described in detail, this technical solution can reduce the obstruction to the reduced pressure region and improve the safety performance of the secondary battery 100, whether it is used only on the first current collector 140, only on the second current collector 150, or on both simultaneously.

[0057] In one embodiment of the secondary battery 100 of the present invention, referring to Figure 3, the weak portion 141 is a linear notch, four weak portions 141 are evenly distributed in the circumferential direction of the first current collector member 140, and none of the four weak portions 141 are in communication with each other, with a=12.8mm, b=18.2mm, R1=17.7mm, R2=20.2mm, R2-R1=2.5mm, c=0.9mm, β=90°, the two central angles γ and δ have an overlapping portion, and w1=12mm, w2=3.6mm.

[0058] In another embodiment of the secondary battery 100 of the present invention, referring to Figure 4, the weak portion 141 is a bent notch, the angle between the bends is 90°, the corner of the bend is close to the center of the first current collector 140, the opening 113 faces the outer circumference of the first current collector 140, four weak portions 141 are evenly distributed in the circumferential direction of the first current collector 140, none of the four weak portions 141 are in communication with each other, a=14.2mm, b=18.25mm, R1=18mm, R2=20.2mm, R2-R1=2.2mm, c=0.25mm, β=90°, the two central angles γ and δ have an overlapping portion, w1=8.6mm, w2=0.65mm.

[0059] In both of the above embodiments, the vulnerable portion 141 installed can reduce the shielding of the first current collector 140 to the reduced pressure region on the first end wall 114 when the secondary battery 100 experiences a loss of thermal control. The technical solutions of the above embodiments can also be applied to the second current collector 150 and the second end wall 111 and achieve the same effect, so they will not be described in detail.

[0060] Referring to Figure 5, the present invention further provides a battery pack 10 which includes a secondary battery 100 according to any one of the above, and in one embodiment of the battery pack 10 of the present invention, the battery pack 10 includes a casing 101, a casing cover 102 and a plurality of secondary batteries 100, the plurality of secondary batteries 100 arranged in the casing 101 and connected to each other in series, parallel, or a mixture of series and parallel, and the casing cover 102 is sealed on the casing 101 and provides protection for the plurality of secondary batteries 100. It is necessary to explain that the battery pack 10 may include parts other than the secondary battery 100 of the present invention, such as a battery pack 10 thermal management system and a circuit board, and the battery pack 10 may be a battery module, a battery package, a power storage cabinet, etc., which will not be explained in detail here.

[0061] Referring to Figure 6, the present invention further provides an electronic device 1, which includes the battery pack 10 described above. A work unit 11 is electrically connected to the battery pack 10 to obtain power support. In one embodiment, the electronic device 1 is a vehicle, which may be a gasoline car, a gas car, or a new energy car, and the new energy car may be, but is not limited to, a pure electric car, a hybrid car, or a range extender car. The work unit 11 is the vehicle body, and the battery pack 10 is installed at the bottom of the vehicle body to provide power support for the vehicle's movement or the operation of in-vehicle electrical components. However, in several other embodiments, the electronic device 1 may further be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, and a power tool. Spacecraft include airplanes, rockets, spacecraft, and spaceships. The work unit 11 may also be a unit component that receives power from the battery pack 10 and performs a corresponding task, such as a fan blade rotation unit or a vacuum cleaner suction work unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The embodiments of the present invention do not impose any special limitations on the above-mentioned electronic device 1.

[0062] In the secondary battery of the present invention, multiple weak points are provided on the current collector, and the weak points are configured to rupture when the internal pressure of the secondary battery exceeds a threshold, causing at least a portion of the current collector to bend away from the electrode assembly and reducing shielding to the reduced pressure region on the end wall. The distance from the point of the weak point furthest from the center of the current collector to the point of the weak point furthest from the center of the current collector is defined as a, and the minimum central angle α that passes through the center of the current collector and covers the weak point is defined, and the minimum radial width of the region covered by the current collector at angle α is defined as b, and is limited to 0.4b ≤ a ≤ 0.9b. This configuration prevents the weak points from penetrating the current collector radially, further enhances the structural strength of the current collector, gives the current collector high flatness, reduces the difficulty of welding the current collector and tab, and improves the reliability of the welded connection. Therefore, the present invention effectively overcomes some of the practical problems in existing technology and has very high utility and significance. The above embodiments exemplify the principle and effects of the present invention and do not limit the present invention. Anyone familiar with this technology may modify or change the above embodiments without violating the spirit and scope of the invention. Accordingly, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical concept disclosed herein should still be included within the scope of protection of the invention. [Industrial applicability]

[0063] The secondary battery, battery pack, and electronic device of the present invention can be applied to the field of battery technology. [Explanation of Symbols]

[0064] 1:Electronic equipment 10: Battery pack 11: Work Unit 101: Box body 102: Box cover 100: Secondary battery 110: Casing 111: Second End Wall 112: Side wall 113:Aperture 114: First end wall 115: Explosion-proof valve 120: Electrode Assembly 121:Second pole plate 1211: Positive electrode current collector 1212: Second coating area 1213: Second uncoated area 122: Separator 123: 1st pole plate 1231: Negative electrode current collector 1232: First coating area 1233: First uncoated area 124: Tab 1 125: Tab 2 126: Winding structure 130: Polar column 140: First current collector 141: Vulnerable parts 142: First weld mark 143: Second weld mark 144: Center hole 145: Bending section 150: Second current collector

Claims

1. A casing including an end wall, on which an explosion-proof valve is installed, An electrode assembly housed within the casing and including a tab facing the end wall, A current collector member installed between the electrode assembly and the end wall and electrically connected to the tab, wherein the current collector member is provided with at least one weak point, the weak point is configured to break when the internal pressure of the secondary battery exceeds a threshold, and at least a portion of the current collector member is bent away from the electrode assembly to reduce the interruption to the reduced pressure region, A secondary battery in which, along the radial direction of the current collector, the span of the weak portion is a, the minimum central angle passing through the center of the current collector and covering the weak portion is α, and the minimum radial width of the region covered by the current collector at angle α is b, such that 0.4b ≤ a ≤ 0.9b.

2. The secondary battery according to claim 1, wherein, along the radial direction of the current collector, R1 is the maximum distance from the weak portion to the center of the current collector, and R2 is the minimum distance from the explosion-proof valve to the center of the end wall, so R2 - R1 ≤ 3 mm.

3. The secondary battery according to claim 2, wherein the current collecting member includes a center hole, and the minimum distance from the weak portion to the edge of the center hole is c, so c ≤ 2 mm.

4. The secondary battery according to claim 3, wherein R2 - R1 ≥ c.

5. The secondary battery according to claim 1, wherein there are multiple vulnerable parts, and at least one of the multiple vulnerable parts is not in communication with any of the other vulnerable parts.

6. The secondary battery according to claim 1, wherein the number of weak points is at least three, all of the weak points are distributed along the circumferential direction of the current collector, and if β is the rotation angle of the outermost radial contour of the space between two adjacent weak points, then β ≤ 120°.

7. The secondary battery according to claim 6, wherein the current collector and the casing are welded together to form at least one first weld mark, two points located on both sides of the first weld mark in the circumferential direction along the circumferential direction of the current collector are each connected to the center of the current collector to form a central angle γ, the region enclosed by each of the weak parts or the region between each of two adjacent weak parts forms a bent portion when the internal pressure of the secondary battery exceeds a threshold, the minimum central angle that passes through the center of the current collector and covers the bent portion is δ, and each of the δ central angle and the γ central angle at least partially overlap.

8. The secondary battery according to claim 7, wherein the minimum distance between the first weld mark and the weak portion is 1 mm or more.

9. The secondary battery according to claim 1, wherein the current collector and the tab are welded together to form at least one second weld mark, and the minimum distance between the second weld mark and the weak portion is 1 mm or more.

10. The secondary battery according to claim 1, wherein the weak portion is one or more of the following: notches, thinning, or perforations.

11. The secondary battery according to claim 1, wherein there are multiple weak points, the multiple weak points are distributed along the circumferential direction of the current collector, and each weak point is installed extending along the radial direction of the current collector.

12. The secondary battery according to claim 5, wherein a plurality of sets of weak points are provided on the current collector, each of the weak points is provided extending along the radial direction of the current collector, and one end of each set of weak points near the center of the current collector is in communication with one another.

13. The secondary battery according to claim 5, wherein the current collecting member includes a plurality of vulnerable parts, and none of the plurality of vulnerable parts are in communication with each other.

14. A battery pack comprising a secondary battery according to any one of claims 1 to 13.

15. An electronic device comprising the battery pack described in claim 14.

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