Secondary battery and electric device

Abstract

The invention discloses a secondary battery and electric equipment, the secondary battery comprises a shell and an electrode assembly, the electrode assembly is accommodated in the shell, the shell comprises a shell body and a shell cover, and the shell cover comprises a first edge and a second edge adjacent to the first edge. The shell cover is provided with a groove at least comprising a first groove section and a second groove section, and the first groove section and the second groove section are in a curve shape when observed in the thickness direction of the shell cover. The first groove section comprises a first end connected with the second groove section and a second end serving as the tail end of the groove, the first groove section extends in the direction away from the second edge, and the first groove section is parallel to the first edge or gradually away from the first edge in the extending direction from the first end to the second end. And when the internal pressure of the secondary battery is too high, the groove can be broken for pressure relief and air exhaust, so that the risk that the secondary battery catches fire and explodes is reduced. And the first groove section can guide cracks of the groove, so that the possibility that the shell cover is exploded along with the groove is reduced, and the safety of the secondary battery is improved.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a secondary battery and electrical equipment. Background Art

[0002] With the development of various electronic devices, secondary batteries have become an indispensable part of daily life. For example, mobile phones, tablets, laptops and digital cameras all require secondary batteries to provide power for normal operation. At present, the quality and safety requirements of secondary batteries are getting higher and higher. For example, in the case of unconventional operations such as fire and severe impact, the secondary battery is prone to heat up and the internal gas increases, which may cause fire and explosion. For this reason, the outer shell of the secondary battery is usually provided with grooves to ensure that the grooves can rupture when the internal pressure of the secondary battery is too high, thereby relieving the pressure of the secondary battery. Summary of the invention

[0003] With respect to the secondary battery in the prior art, the inventors have discovered that when the groove ruptures to release the pressure of the secondary battery, the ends of the cracks in the groove often extend to the edges of the shell cover on both sides, causing most of the shell cover to separate from the shell body, so that the shell cover explodes along with the groove, and the exploded shell cover is relatively sharp and can easily injure people.

[0004] In view of the above situation, it is necessary to provide a secondary battery with improved safety.

[0005] The first aspect of the present application provides a secondary battery, comprising a shell and an electrode assembly, wherein the electrode assembly is accommodated in the shell, the shell comprising a shell and a shell cover, the shell being a metal shell, and the shell and the shell cover being fixedly connected. The shell cover comprises a first edge and a second edge adjacent to the first edge. The shell cover is provided with a groove, the groove comprising at least a first groove section and a second groove section, and the first groove section and the second groove section are curved when viewed along a first direction, and the first direction is the thickness direction of the shell cover. The first groove section comprises a first end and a second end, the first end is connected to the second groove section, the second end is the end of the groove, the first groove section extends in a direction away from the second edge, and along the extension direction from the first end to the second end, the first groove section is parallel to the first edge or the first groove section gradually moves away from the first edge.

[0006] The shell cover is provided with a groove. When the secondary battery heats up and the internal gas increases, the groove can rupture to release the pressure and exhaust the secondary battery, thereby helping to reduce the risk of fire and explosion of the secondary battery. In addition, the first groove section extends in a direction away from the second edge. Along the extension direction from the first end to the second end, the first groove section is parallel to the first edge or the first groove section gradually moves away from the first edge. When the groove ruptures, the first groove section can guide the crack of the groove, so that the crack of the groove is away from the first edge of the shell cover, thereby helping to reduce the possibility of the shell cover exploding together with the groove, and helping to improve the safety of the secondary battery.

[0007] In one or more of the above embodiments, the groove further includes a third groove section, and when viewed along the first direction, the third groove section is curved. The third groove section includes a third end and a fourth end, the third end is connected to an end of the second groove section away from the first groove section, the fourth end is the end of the groove, the third groove section extends in a direction away from the first edge, and along the extension direction from the third end to the fourth end, the third groove section is parallel to the second edge or the third groove section gradually moves away from the second edge. When the groove breaks, the third groove section can guide the crack of the groove, so that the crack of the groove is away from the second edge of the shell cover, which is conducive to further reducing the possibility of the shell cover bursting together with the groove, and is conducive to further improving the safety of the secondary battery.

[0008] In one or more of the above embodiments, the first groove segment and / or the third groove segment transitions with the second groove segment with a rounded corner, which is beneficial to reduce the possibility of repeated etching at the connection between the first groove segment and the third groove segment and the second groove segment during etching, and facilitates the processing and forming of the groove.

[0009] In one or more of the above embodiments, when viewed along the first direction, the first groove segment and / or the third groove segment is in a straight line. When the groove is broken, the straight first groove segment can better guide the crack of the groove away from the first edge of the shell cover, and the straight third groove segment can better guide the crack of the groove away from the second edge of the shell cover, thereby further reducing the possibility of the shell cover bursting together with the groove, and further improving the safety of the secondary battery.

[0010] In one or more of the above embodiments, the housing has a first bisector and a second bisector, the first bisector bisects the first edge and is parallel to the second edge, the second bisector bisects the second edge and is parallel to the first edge, and the first bisector intersects the second bisector. When viewed along the first direction, the groove does not overlap with the first bisector and the groove does not overlap with the second bisector. The groove is provided at the angle where the first edge and the second edge intersect. When the secondary battery heats up and the internal gas increases, the groove can be ruptured to release the pressure and exhaust the secondary battery.

[0011] In one or more of the above embodiments, the distance between the first end and the first edge is d1, the distance between the third end and the second edge is d2, d1≥1mm and / or d2≥1mm. By setting d1≥1mm, the shortest distance between the first groove section and the first edge can be made not too small, and by setting d2≥1mm, the shortest distance between the third groove section and the second edge can be made not too small. When the groove breaks, it is helpful to further reduce the possibility of the shell cover bursting together with the groove, which is helpful to further improve the safety of the secondary battery.

[0012] In one or more of the above embodiments, the angle between the first groove section and the first edge is θ1, the angle between the third groove section and the second edge is θ2, 30°≤θ1≤60° and / or 30°≤θ2≤60°. By setting 30°≤θ1 and / or 30°≤θ2, when the length of the first groove section is constant, along the extension direction from the first end to the second end, the first groove section can be further away from the first edge, so that the first groove section can better guide the crack of the groove away from the first edge of the shell cover, and when the length of the third groove section is constant, along the extension direction from the third end to the fourth end, the third groove section can be further away from the second edge, so that the third groove section can better guide the crack of the groove away from the second edge of the shell cover, thereby helping to further reduce the possibility of the shell cover bursting together with the groove, and helping to further improve the safety of the secondary battery. By setting θ1≤60° and / or θ2≤60°, when the length of the first groove segment is constant, the first groove segment will not be too far away from the first edge along the extension direction from the first end to the second end; when the length of the third groove segment is constant, the third groove segment will not be too far away from the second edge along the extension direction from the third end to the fourth end. When the secondary battery heats up and the internal gas increases, it is beneficial for the groove to rupture in time to release the pressure and exhaust the secondary battery. At the same time, it is beneficial for the first groove segment to better play the role of guiding the crack away from the first edge of the shell cover, and the third groove segment to better play the role of guiding the crack away from the second edge of the shell cover.

[0013] In one or more of the above embodiments, when observed along the first direction, the second groove segment is in the shape of an arc, the center of the second groove segment and the intersection of the first edge and the second edge are located on the same side of the second groove segment, and the extension line of the second groove segment intersects with the first edge and the second edge respectively, so that the second groove segment is bent toward the center of the shell cover. The arc shape of the second groove segment can make the process of etching the second groove segment more continuous, which can facilitate the processing and forming of the groove. In addition, as the secondary battery heats up and the internal gas increases, the middle part of the shell cover is subjected to greater force and is more likely to deform. Therefore, by bending the second groove segment toward the center of the shell cover, it is beneficial to make the groove closer to the center of the shell cover, so that the groove is more likely to rupture and form a larger pressure relief port, thereby facilitating the rapid discharge of the gas inside the secondary battery for pressure relief.

[0014] In one or more of the above embodiments, the outer shell is a steel shell, and the shell body and the shell cover are connected by welding.

[0015] In one or more of the above embodiments, along the first direction, the depression depth of the groove is n1, the thickness of the shell cover is n2, and 0.35n2≤n1≤0.75n2. By setting 0.35n2≤n1, the depression depth of the groove will not be too small. When the secondary battery heats up and the internal gas increases, it is beneficial for the groove to rupture in time to release the pressure and exhaust the secondary battery. By setting n1≤0.75n2, the depression depth of the groove will not be too large, which can make the shell cover have a higher structural strength, which is beneficial to improve the ability of the shell to resist falling and damage.

[0016] In one or more of the above embodiments, the maximum width of the groove is W, and 0.05 mm ≤ W ≤ 0.2 mm.

[0017] The second aspect of the present application provides an electrical device, comprising the secondary battery of the first aspect of the present application. The possibility of the shell cover in the secondary battery exploding together with the groove is low, so the secondary battery is safer, which is conducive to improving the safety of the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A front view of a secondary battery provided in accordance with an embodiment of the present application.

[0019] Figure 2 A top view of a secondary battery provided in accordance with an embodiment of the present application.

[0020] Figure 3 for Figure 2 Magnified view of area A.

[0021] Figure 4 A schematic diagram of a groove provided in the second embodiment of the present application.

[0022] Figure 5 A schematic diagram of a groove provided in the third embodiment of the present application.

[0023] Figure 6 A schematic diagram of a groove provided in the fourth embodiment of the present application.

[0024] Figure 7 For along Figure 2 Cross-section along section line BB.

[0025] Figure 8 For along Figure 2 Cross-section along the center line CC.

[0026] Fig. 9 An overall schematic diagram of an electrical device provided in one embodiment of the present application.

[0027] Main component symbols 1000, electrical equipment; 100, secondary battery; 10, outer shell; 10a, first bisector; 10b, second bisector; 101, pit; 11, shell; 111, bottom wall; 112, side wall; 12, shell cover; 121, first edge; 122, second edge; 123, third edge; 124, fourth edge; 20, electrode assembly; 21, negative electrode sheet; 22, positive electrode sheet; 23, diaphragm; 30, groove; 31, first groove section; 311, first end; 312, second end; 32, second groove section; 33, third groove section; 331, third end; 332, fourth end; 40, tab; 41, negative electrode tab; 42, positive electrode tab; 50, pole; 60, insulating member; X, first direction; O, center of circle. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0029] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a centrally disposed element at the same time. When an element is considered to be "disposed on" another element, it may be directly disposed on the other element or there may be a centrally disposed element at the same time.

[0030] Unless otherwise specified, the term "plurality" as used herein means two or more than two.

[0031] The terms "first", "second", etc. are only used to distinguish different objects and shall not be understood as indicating or implying relative importance or implying the quantity, specific order or primary and secondary relationship of the technical features indicated.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0033] It should be understood that, considering the actual processing tolerance factors, in the technical solution of the present application, when the two elements are arranged parallel / vertically and in the same direction, there may be a certain angle between the two elements, and a tolerance of 0-±10% is allowed between the two elements. A tolerance of 0-±10% is allowed between the two elements greater than, equal to or less than.

[0034] An embodiment of the present application provides a secondary battery, including a shell and an electrode assembly, wherein the electrode assembly is accommodated in the shell, the shell includes a shell and a shell cover, the shell is a metal shell, and the shell and the shell cover are fixedly connected. The shell cover includes a first edge and a second edge adjacent to the first edge. The shell cover is provided with a groove, the groove includes at least a first groove section and a second groove section, and when viewed along a first direction, the first groove section and the second groove section are curved, and the first direction is the thickness direction of the shell cover. The first groove section includes a first end and a second end, the first end is connected to the second groove section, the second end is the end of the groove, the first groove section extends in a direction away from the second edge, and along the extension direction from the first end to the second end, the first groove section is parallel to the first edge or the first groove section gradually moves away from the first edge.

[0035] In the secondary battery of the present application, the shell cover is provided with a groove. When the secondary battery heats up and the internal gas increases, the groove can rupture to release the pressure and exhaust the secondary battery, thereby helping to reduce the risk of fire and explosion of the secondary battery. In addition, the first groove section extends in a direction away from the second edge. Along the extension direction from the first end to the second end, the first groove section is parallel to the first edge or the first groove section gradually moves away from the first edge. When the groove ruptures, the first groove section can guide the crack of the groove, so that the crack of the groove is away from the first edge of the shell cover, thereby helping to reduce the possibility of the shell cover exploding together with the groove, and helping to improve the safety of the secondary battery.

[0036] Some embodiments of the present application will be described below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0037] See also Figures 1 to 8 An embodiment of the present application provides a secondary battery 100 , including a housing 10 and an electrode assembly 20 , wherein the electrode assembly 20 is accommodated in the housing 10 .

[0038] See also Figure 1 The housing 10 includes a shell 11 and a shell cover 12, and the shell 11 and the shell cover 12 are arranged opposite to each other along a first direction X, and the first direction X is the thickness direction of the housing 10. The housing 10 is a metal shell, and the shell 11 and the shell cover 12 are fixedly connected. The housing 10 includes but is not limited to a steel shell, and the connection method of the shell 11 and the shell cover 12 includes but is not limited to riveting connection, adhesive connection, fusion connection and welding connection. In some embodiments, the housing 10 is a steel shell, and the shell 11 and the shell cover 12 are connected by welding.

[0039] See also Figures 2 to 6 The shell cover 12 includes a first edge 121 and a second edge 122, the second edge 122 is adjacent to the first edge 121, and the edges of the shell cover 12 include but are not limited to the first edge 121 and the second edge 122. In some embodiments, see Figure 2The shell cover 12 further includes a third edge 123 and a fourth edge 124 . The third edge 123 is disposed opposite to the first edge 121 , and the fourth edge 124 is disposed opposite to the second edge 122 .

[0040] In some embodiments, see Figure 2 The housing 10 has a first bisector 10a and a second bisector 10b. The so-called first bisector 10a bisects the first edge 121 and is parallel to the second edge 122. The so-called second bisector 10b bisects the second edge 122 and is parallel to the first edge 121. The first bisector 10a and the second bisector 10b intersect. The first bisector 10a and the second bisector 10b can jointly divide the housing cover 12 into a plurality of regions. For example, when the edges of the housing cover 12 are the first edge 121, the second edge 122, the third edge 123 and the fourth edge 124, the first bisector 10a and the second bisector 10b divide the housing cover 12 into four regions, wherein each region includes an angle where two adjacent edges intersect.

[0041] In some embodiments, see Figure 7 and Figure 8 The shell 11 includes a bottom wall 111 and a side wall 112. The side wall 112 is connected to the periphery of the bottom wall 111 and forms a pit 101 with the bottom wall 111. In some embodiments, the shell cover 12 is plate-shaped, the shell cover 12 covers the pit 101, and part of the shell cover 12 is fixedly connected to the side wall 112. In some embodiments, the outer shell 10 is a steel shell, and the shell cover 12 is connected to the side wall 112 by welding.

[0042] The pit 101 is filled with an electrolyte, and the electrolyte includes an electrolyte salt. In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt. The electrolyte salt includes, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), bistrifluoromethanesulfonyl imide lithium LiN(CF3SO2)2 (LiTFSI), bis(fluorosulfonyl)imide lithium Li(N(SO2F)2) (LiFSI), lithium hexafluorocesium oxide (LiCsF6), lithium perchlorate (LiClO4) or lithium trifluoromethanesulfonate (LiCF3SO3).

[0043] See also Figure 7 and Figure 8, the electrode assembly 20 is disposed in the pit 101. The electrode assembly 20 includes a negative electrode sheet 21, a positive electrode sheet 22 and a separator 23, and the separator 23 separates the negative electrode sheet 21 from the positive electrode sheet 22. In some embodiments, the electrode assembly 20 is a stacked structure, a plurality of negative electrode sheets 21 and a plurality of positive electrode sheets 22 are alternately stacked, and the separator 23 is disposed between any adjacent negative electrode sheets 21 and positive electrode sheets 22. In some embodiments, the electrode assembly 20 is a winding structure, a single negative electrode sheet 21 and a single positive electrode sheet 22 are stacked and then wound, and the separator 23 is disposed between the negative electrode sheet 21 and the positive electrode sheet 22.

[0044] In some embodiments, the negative electrode plate 21 includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is arranged on two opposite sides of the negative electrode current collector along the thickness direction. The positive electrode plate 22 includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is arranged on two opposite sides of the positive electrode current collector along the thickness direction. The negative electrode current collector includes but is not limited to copper foil, copper alloy foil, nickel foil, titanium foil, nickel foam or copper foam, and the positive electrode current collector includes but is not limited to aluminum foil and aluminum alloy foil. In some embodiments, the negative electrode current collector is copper foil, and the positive electrode current collector is aluminum foil. The material of the negative electrode active material layer includes but is not limited to graphite, hard carbon, soft carbon, silicon, silicon oxygen material and silicon carbon material. The material of the positive electrode active material layer includes but is not limited to lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate and lithium manganese oxide.

[0045] In some embodiments, the diaphragm 23 is an insulating film material such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film.

[0046] See also Figures 3 to 6 The shell cover 12 is provided with a groove 30, the groove 30 has two separated ends, and the concave direction of the groove 30 is parallel to the first direction X. When the secondary battery 100 heats up and the internal gas increases, the groove 30 can be broken to release the pressure and exhaust the secondary battery 100, which is conducive to reducing the risk of fire and explosion of the secondary battery 100. In some embodiments, the groove 30 can be formed by laser etching on the shell cover 12 according to a set path.

[0047] In some embodiments, see Figure 2 , viewed along the first direction X, the groove 30 does not overlap with the first bisector 10a and the groove 30 does not overlap with the second bisector 10b. The groove 30 is provided at the angle where the first edge 121 and the second edge 122 intersect. When the secondary battery 100 heats up and the internal gas increases, the groove 30 can be ruptured to release the pressure and exhaust the secondary battery 100.

[0048] See also Figures 3 to 6The groove 30 includes at least a first groove section 31 and a second groove section 32. The first groove section 31 and the second groove section 32 are connected. When observed along the first direction X, the first groove section 31 and the second groove section 32 are curved. The so-called curve includes any continuous line, such as a straight line, a broken line, and an arc.

[0049] The first groove section 31 includes a first end 311 and a second end 312, the first end 311 is connected to the second groove section 32, the second end 312 is the end of the groove 30, and the first groove section 31 extends in a direction away from the second edge 122. Along the extension direction from the first end 311 to the second end 312, the first groove section 31 is parallel to the first edge 121, or the first groove section 31 gradually moves away from the first edge 121. When the groove 30 is broken, the first groove section 31 can guide the crack of the groove 30, so that the crack of the groove 30 is away from the first edge 121 of the shell cover 12, which is conducive to reducing the possibility of the shell cover 12 bursting together with the groove 30, and is conducive to improving the safety of the secondary battery 100.

[0050] In some embodiments, see Figure 3 The first groove section 31 and the second groove section 32 are transitioned with a rounded corner, which is beneficial to reduce the possibility of repeated etching at the connection between the first groove section 31 and the second groove section 32 during the etching process, and facilitates the processing and forming of the groove 30.

[0051] In some embodiments, see Figure 3 , Figure 5 and Figure 6 , the first groove section 31 is in a straight line. When the groove 30 is broken, the straight first groove section 31 can better guide the crack of the groove 30 away from the first edge 121 of the shell cover 12, thereby further reducing the possibility of the shell cover 12 bursting together with the groove 30, and further improving the safety of the secondary battery 100. In some embodiments, please refer to Figure 4 , the first groove section 31 is in an arc shape.

[0052] In some embodiments, the first groove section 31 is in a straight line shape, and the angle between the first groove section 31 and the first edge 121 is θ1, 30°≤θ1≤60°. For example, the value of θ1 is 30°, 35°, 40°, 45°, 50°, 55° or 60°. By setting 30°≤θ1, when the length of the first groove section 31 is constant, along the extension direction from the first end 311 to the second end 312, the first groove section 31 can be further away from the first edge 121, so that the first groove section 31 can better guide the crack of the groove 30 away from the first edge 121 of the shell cover 12, thereby helping to further reduce the possibility of the shell cover 12 bursting together with the groove 30, and helping to further improve the safety of the secondary battery 100. By setting θ1≤60°, when the length of the first groove section 31 is constant, along the extension direction from the first end 311 to the second end 312, the first groove section 31 will not be too far away from the first edge 121. When the secondary battery 100 heats up and the internal gas increases, it is beneficial for the groove 30 to rupture in time to release the pressure and exhaust the secondary battery 100. At the same time, it is beneficial for the first groove section 31 to better play the role of guiding the crack away from the first edge 121 of the shell cover 12.

[0053] In some embodiments, the length of the first slot segment 31 is greater than or equal to 1 mm. For example, the length of the first slot segment 31 is 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm. It should be understood that since the groove 30 is formed on the shell cover 12, the length of the first slot segment 31 is limited by the size of the shell cover 12. In some embodiments, the length of the first slot segment 31 is not so large that the distance between the second end 312 and the first bisector 10a is greater than 0.

[0054] In some embodiments, the distance between the first end 311 and the first edge 121 is d1, and d1 ≥ 1 mm. For example, the value of d1 is 1 mm, 1.2 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm. By setting d1 ≥ 1 mm, the shortest distance between the first groove section 31 and the first edge 121 can be made not too small. When the groove 30 is broken, it is beneficial to further reduce the possibility of the shell cover 12 bursting together with the groove 30, which is beneficial to further improve the safety of the secondary battery 100. It should be understood that since the groove 30 is formed on the shell cover 12, the maximum value of d1 is limited by the size of the shell cover 12. In some embodiments, the maximum value of d1 is less than the distance between the first edge 121 and the second bisector 10b.

[0055] In some embodiments, see Figure 3 and Figure 6, viewed along the first direction X, the second groove segment 32 is in an arc shape, and the curvature of the second groove segment 32 is not limited, for example, the second groove segment 32 is in a quarter arc shape. The arc shape of the second groove segment 32 can make the etching process of the second groove segment 32 more continuous, which can facilitate the processing and forming of the groove 30. In some embodiments, please refer to Figure 4 , viewed along the first direction X, the second slot segments 32 are in the shape of multiple connected arcs. Figure 5 , viewed along the first direction X, the second slot section 32 is in a straight line shape.

[0056] In some embodiments, see Figure 3 The center O of the second slot segment 32 and the intersection of the first edge 121 and the second edge 122 are located on the same side of the second slot segment 32. The extension line of the second slot segment 32 (refer to Figure 3 The two dotted lines at the first end 311 and the third end 331 of the secondary battery 100 intersect with the first edge 121 and the second edge 122 respectively. As the secondary battery 100 heats up and the internal gas increases, the middle part of the shell cover 12 is subjected to greater force and is more likely to deform. Therefore, by bending the second groove section 32 toward the center of the shell cover 12, it is beneficial to make the groove 30 closer to the center of the shell cover 12, so that the groove 30 is more likely to break and form a larger pressure relief port, thereby facilitating the rapid discharge of gas inside the secondary battery 100 for pressure relief. In some embodiments, refer to Figure 6 , the center O of the second slot segment 32 and the intersection of the first edge 121 and the second edge 122 are located on different sides of the second slot segment 32. It should be understood that Figure 3 and Figure 6 The center O shown is only for better illustrating that the intersection of the first edge 121 and the second edge 122 is located on the same side or different side of the second groove section 32 . The existence of the center O does not actually affect the processing of the shell cover 12 .

[0057] In some embodiments, see Figures 3 to 6 , the groove 30 also includes a third groove section 33. When viewed along the first direction X, the third groove section 33 is in a curved shape. The third groove section 33 includes a third end 331 and a fourth end 332. The third end 331 is connected to the end of the second groove section 32 away from the first groove section 31. The fourth end 332 is the end of the groove 30. The third groove section 33 extends in a direction away from the first edge 121. Along the extension direction from the third end 331 to the fourth end 332, the third groove section 33 is parallel to the second edge 122 or the third groove section 33 gradually moves away from the second edge 122. When the groove 30 is broken, the third groove section 33 can guide the crack of the groove 30, so that the crack of the groove 30 is away from the second edge 122 of the shell cover 12, which is conducive to further reducing the possibility of the shell cover 12 bursting together with the groove 30, and is conducive to further improving the safety of the secondary battery 100.

[0058] In some embodiments, see Figure 3 The third groove section 33 and the second groove section 32 are transitioned with a rounded corner, which is beneficial to reduce the possibility of repeated etching at the connection between the third groove section 33 and the second groove section 32 during the etching process, and facilitates the processing and forming of the groove 30.

[0059] In some embodiments, see Figure 3 , Figure 5 and Figure 6 , the third groove section 33 is in a straight line. When the groove 30 is broken, the straight third groove section 33 can better guide the crack of the groove 30 away from the second edge 122 of the shell cover 12, thereby further reducing the possibility of the shell cover 12 bursting together with the groove 30, and further improving the safety of the secondary battery 100. In some embodiments, please refer to Figure 4 , the third groove section 33 is in an arc shape.

[0060] In some embodiments, the third groove section 33 is in a straight line, and the angle between the third groove section 33 and the second edge 122 is θ2, 30°≤θ2≤60°. For example, the value of θ2 is 30°, 35°, 40°, 45°, 50°, 55° or 60°. By setting 30°≤θ2, when the length of the third groove section 33 is constant, along the extension direction from the third end 331 to the fourth end 332, the third groove section 33 can be further away from the second edge 122, so that the third groove section 33 can better guide the crack of the groove 30 away from the second edge 122 of the shell cover 12, thereby helping to further reduce the possibility of the shell cover 12 bursting together with the groove 30, and helping to further improve the safety of the secondary battery 100. By setting θ2≤60°, when the length of the third groove section 33 is constant, the third groove section 33 will not be too far away from the second edge 122 along the extension direction from the third end 331 to the fourth end 332. When the secondary battery 100 heats up and the internal gas increases, it is beneficial for the groove 30 to rupture in time to release the pressure and exhaust the secondary battery 100, and it is also beneficial for the third groove section 33 to better play the role of guiding the crack away from the second edge 122 of the shell cover 12.

[0061] In some embodiments, the length of the third slot segment 33 is greater than or equal to 1 mm. For example, the length of the third slot segment 33 is 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm. It should be understood that since the groove 30 is formed on the shell cover 12, the length of the third slot segment 33 is limited by the size of the shell cover 12. In some embodiments, the length of the third slot segment 33 is not so large that the distance between the fourth end 332 and the second bisector 10b is greater than 0.

[0062] In some embodiments, the distance between the third end 331 and the second edge 122 is d2, d2 ≥ 1mm. For example, the value of d2 is 1mm, 1.2mm, 1.5mm, 2mm, 2.5mm or 3mm. By setting d2 ≥ 1mm, the shortest distance between the third groove section 33 and the second edge 122 can be made not too small. When the groove 30 is broken, it is beneficial to further reduce the possibility of the shell cover 12 bursting together with the groove 30, which is beneficial to further improve the safety of the secondary battery 100. It should be understood that since the groove 30 is formed on the shell cover 12, the maximum value of d2 is limited by the size of the shell cover 12. In some embodiments, the maximum value of d2 is less than the distance between the second edge 122 and the first bisector 10a.

[0063] In some embodiments, see Figure 8 , along the first direction X, the depression depth of the groove 30 is n1, the thickness of the shell cover 12 is n2, 0.35n2≤n1≤0.75n2. For example, the value of n1 is 0.35n2, 0.4n2, 0.5n2, 0.6n2 and 0.75n2. By setting 0.35n2≤n1, the depression depth of the groove 30 will not be too small. When the secondary battery 100 heats up and the internal gas increases, it is beneficial for the groove 30 to rupture in time to relieve the pressure and exhaust the secondary battery 100. By setting n1≤0.75n2, the depression depth of the groove 30 will not be too large, which can make the shell cover 12 have a higher structural strength, which is beneficial to improve the ability of the shell 10 to resist falling and damage.

[0064] In some embodiments, the thickness n2 of the housing cover 12 is 0.05 mm to 0.2 mm. For example, the value of n2 is 0.05 mm, 0.1 mm, 0.15 mm or 0.2 mm.

[0065] In some embodiments, the width of each cross section of the groove 30 may be the same or different, but the maximum width of the groove 30 is W, 0.02 mm ≤ W ≤ 0.5 mm. For example, the value of W is 0.02 mm, 0.05 mm, 0.1 mm, 0.2 mm, 0.3 mm or 0.5 mm.

[0066] In some embodiments, see Figure 7 and Figure 8 The secondary battery 100 includes a tab 40 connected to the electrode assembly 20, and the tab 40 includes a negative tab 41 and a positive tab 42. The negative tab 41 is electrically connected to the negative current collector, and the positive tab 42 is electrically connected to the positive current collector. The connection method between the negative tab 41 and the negative current collector and the positive tab 42 and the positive current collector includes but is not limited to integral cutting and welding. The negative tab 41 and the positive tab 42 may extend out of the electrode assembly 20 in the same or different directions.

[0067] In some embodiments, the number of negative electrode tabs 41 and positive electrode tabs 42 are both multiple, and the multiple negative electrode tabs 41 are stacked in sequence along the first direction X, and then welded together to form a negative electrode tab bundle, and the negative electrode tab bundle is welded to the housing 10 (see Figure 7 ). A plurality of positive electrode tabs 42 are stacked in sequence along the first direction X, and are welded together to form a positive electrode tab bundle. The positive electrode tab bundle is welded to the pole 50, and the pole 50 is insulated and arranged in the housing 10 (see Figure 8 ). In some embodiments, the positive electrode tab bundle is electrically connected to the pole 50 through an adapter, and the material of the adapter includes but is not limited to conductive materials such as copper, aluminum, nickel, and nickel alloy. In some embodiments, see Figure 6 The pole 50 is insulated and arranged on the housing 10 through an insulating member 60, and the insulating member 60 includes but is not limited to an insulating gasket and an insulating sleeve, the insulating gasket is arranged between the contact surface of the pole 50 and the housing 10, and the insulating sleeve is wrapped around the outer periphery of the pole 50. The material of the insulating member 60 includes but is not limited to plastic and rubber.

[0068] See also Fig. 9 One embodiment of the present application provides an electric device 1000, comprising the secondary battery 100 as described above. The shell cover 12 in the secondary battery 100 is less likely to explode together with the groove 30, so that the safety of the secondary battery 100 is higher, which is conducive to improving the safety of the electric device 1000. The electric device 1000 includes, but is not limited to, electronic devices such as electronic book players, mobile phones, fax machines, copiers, printers, headphones, video recorders, LCD TVs, recorders, radios, cameras, tablet computers, and laptop computers.

[0069] In order to verify the effect of the solution provided in the present application on the secondary battery 100 , the inventors of the present application conducted the following experiment. The experiment included 1 group of comparative examples and 14 groups of embodiments. Each group of comparative examples and embodiments included 50 secondary batteries 100 .

[0070] The preparation process of the secondary battery 100 in Example 1 includes the following steps: Preparation of positive electrode sheet 22: The positive electrode active material lithium cobalt oxide, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride (PVDF) are dissolved in N-methylpyrrolidone (NMP) solution at a weight ratio of 97.5:1:1.5 to form a positive electrode slurry. Aluminum foil is used as a positive electrode current collector, and the positive electrode slurry is coated on the positive electrode current collector. After drying, cold pressing, and slitting, the positive electrode sheet 22 is obtained.

[0071] Preparation of the negative electrode sheet 21: Mix the negative electrode active material artificial graphite, the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene butadiene rubber (SBR) in a weight ratio of 96:1.5:2.5, add deionized water, and stir evenly under the action of a vacuum mixer to obtain a negative electrode slurry; evenly coat the negative electrode slurry on the negative electrode collector copper foil; dry, and then cold press, cut, and slit to obtain the negative electrode sheet 21.

[0072] Preparation of the diaphragm 23: The base material layer of the diaphragm 23 is polyethylene (PE), and an alumina ceramic layer is coated on both sides of the base material layer of the diaphragm 23. Finally, a binder polyvinylidene fluoride (PVDF) is coated on both sides of the ceramic layer and dried.

[0073] Preparation of electrolyte: In a dry argon atmosphere glove box, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were mixed in a mass ratio of 3:5:2, lithium salt LiPF6 was added, and the mixture was mixed evenly to obtain an electrolyte, wherein the mass percentage concentration of LiPF6 was 12.5%.

[0074] The etching process of the groove 30: fix the shell cover 12 in a special fixture; set the laser etching path according to the required notch shape and notch positioning; adjust the laser energy according to the required notch depth n1=0.055mm and the thickness n2=0.1mm of the shell cover 12, and use high-precision laser equipment to notch the surface of the shell cover 12. Prepare the shell cover 12, ensure that the inside of the shell 11 is clean and dust-free, weld the positive electrode tab 42 and the negative electrode tab 41 to the positive electrode lead-in terminal and the negative electrode lead-in terminal on the shell 11 respectively, and ensure good electrical connection; put the stacked electrode assembly 20 into the shell 11 to ensure good fit between the electrode assembly 20 and the shell 11; assemble the shell cover 12 and the shell 11, and seal them by laser welding to ensure the airtightness of the secondary battery 100.

[0075] The preparation process of the secondary battery 100 in Comparative Example 1 is substantially the same as that of Example 1, except that the groove 30 of the secondary battery 100 in Comparative Example 1 does not include the first groove section 31 and the third groove section 33 .

[0076] The manufacturing process of the secondary battery 100 in the second embodiment is substantially the same as that in the first embodiment, except that the groove 30 of the secondary battery 100 in the second embodiment does not include the third groove section 33 .

[0077] The preparation process of the secondary battery 100 in Examples 3 and 4 is substantially the same as that in Example 1, except that the distance between the first end 311 and the first edge 121 and the distance between the third end 331 and the second edge 122 in Examples 3 and 4 are different from those in Example 1.

[0078] The preparation process of the secondary battery 100 in Examples 5 to 10 is substantially the same as that in Example 1, except that the angle between the first groove segment 31 and the first edge 121 and the angle between the third groove segment 33 and the second edge 122 in Examples 5 to 10 are different from those in Example 1.

[0079] The manufacturing process of the secondary battery 100 in Examples 11 to 14 is substantially the same as that in Example 1, except that the recessed depth of the recess 30 in Examples 11 to 14 is different from that in Example 1.

[0080] After the secondary batteries 100 in the comparative examples and the embodiments were prepared, all the secondary batteries 100 in each group were subjected to a hot box test to observe the explosion of the groove 30 and the shell cover 12. All the secondary batteries 100 in each group were subjected to a drop test to observe the drop failure of the secondary batteries 100. After the test, the experimental results were recorded in Table 1.

[0081] The specific process of hot box testing is: 1) The secondary battery 100 to be tested is pretreated under the following conditions: after standing at a test temperature of 20°C (±5°C) for 60 minutes, it is discharged to 3.0V with a constant current of 0.7C and allowed to stand for 10 minutes; it is then charged to 4.25V with a constant current of 0.5C, and then charged to 0.05C with a constant voltage of 4.25V.

[0082] 2) After the pretreatment is completed, the secondary battery 100 is placed vertically in a hot box for testing, wherein the temperature in the hot box is raised to 130±2°C at 5±2°C / min and maintained for 60 minutes. During the test, if the secondary battery 100 does not burn or explode, it means that the hot box test has passed, otherwise, the hot box test has failed.

[0083] 3) 50 secondary batteries are tested, and the number of secondary batteries 100 that pass the test is N, then the hot box test pass rate of this group of experimental secondary batteries 100 is N / 50.

[0084] 4) Observe the explosion conditions of the edges of the shell covers 12 of all the secondary batteries 100 that have passed the hot box test, and count the number of secondary batteries 100 with the edges of the shell covers 12 being M. Then, the explosion rate of the shell covers 12 of the experimental secondary batteries 100 is M / N×100%.

[0085] The specific process of the drop test is: 1) The secondary battery 100 is fully charged in an environment of 23±2°C.

[0086] 2) Take a photo of the secondary battery 100 and record the OCV (Open Circuit Voltage) and impedance of the electrochemical device.

[0087] 3) The secondary battery 100 is made to freely fall from a height of 1.5 meters onto a concrete surface with its six surfaces and four corners facing downwards, wherein the height refers to the distance from the lowest point of the secondary battery 100 to the concrete surface.

[0088] 4) Leave the secondary battery 100 to stand for 1 hour and observe whether the secondary battery 100 explodes, emits smoke, or catches fire.

[0089] 5) After the secondary battery 100 is left to stand for 12 hours, the OCV of the secondary battery 100 is tested to see whether it is greater than or equal to 90% of the initial OCV value before the drop.

[0090] 6) If the secondary battery 100 does not explode, smoke, or catch fire, and the OCV of the secondary battery 100 is greater than or equal to 90% of the initial OCV value before the drop, the test is passed. The number of secondary batteries 100 that passed the test in this group of experiments is T, and the drop pass rate of the secondary batteries 100 in this group of experiments is T / 50.

[0091] Table 1 In Table 1, the explosion rate of the shell cover 12 of the secondary battery 100 in Examples 1 to 14 is significantly lower than the explosion rate of the shell cover 12 of the secondary battery 100 in Comparative Example 1. That is, the present application reduces the possibility of the shell cover 12 exploding along with the groove 30 by making the groove 30 include the first groove section 31 and / or the third groove section 33, which helps to improve the safety of the secondary battery 100.

[0092] In Table 1, according to Example 1, Example 3 and Example 4, the explosion rate of the shell cover 12 of the secondary battery 100 in Example 1 and Example 4 is significantly lower than the explosion rate of the shell cover 12 of the secondary battery 100 in Example 3. That is, the present application is conducive to further reducing the possibility of the shell cover 12 exploding together with the groove 30 by setting d1≥1mm and / or d2≥1mm, which is conducive to further improving the safety of the secondary battery 100.

[0093] In Table 1, according to Example 1, Example 5 to Example 10, the explosion rate of the shell cover 12 of the secondary battery 100 in Example 1, Example 6 to Example 10 is significantly lower than the explosion rate of the shell cover 12 of the secondary battery 100 in Example 5, and the hot box test pass rate of the secondary battery 100 in Example 1, Example 5 to Example 9 is significantly higher than the hot box test pass rate of the secondary battery 100 in Example 10. That is to say, the present application is conducive to further reducing the possibility of the shell cover 12 exploding with the groove 30 by setting 30°≤θ1 and / or 30°≤θ2, which is conducive to further improving the safety of the secondary battery 100. By setting θ1≤60° and / or θ2≤60°, it is conducive to the timely rupture of the groove 30 to relieve the pressure and exhaust the secondary battery 100, which helps the first groove section 31 and the third groove section 33 to better play a guiding role.

[0094] In Table 1, according to Example 1, Example 11 to Example 14, the hot box test pass rate of the secondary battery 100 in Example 1, Example 12 to Example 14 is significantly higher than the hot box test pass rate of the secondary battery 100 in Example 11, and the drop pass rate of the secondary battery 100 in Example 1, Example 11 to Example 13 is significantly higher than the drop pass rate of the secondary battery 100 in Example 14. That is to say, the present application is conducive to the timely rupture of the groove 30 to relieve the pressure and exhaust the secondary battery 100 by setting 0.35n2≤n1. By setting n1≤0.75n2, it is conducive to improving the ability of the housing 10 to resist drop damage.

[0095] In addition, those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not intended to limit the present application. As long as they are within the essential scope of the present application, appropriate changes and modifications to the above embodiments are within the scope disclosed in the present application.

Claims

1. A secondary battery, comprising a housing and an electrode assembly, wherein the electrode assembly is accommodated in the housing, characterized in that: The shell includes a shell and a shell cover, the shell is a metal shell, and the shell and the shell cover are fixedly connected; the shell cover includes a first edge and a second edge adjacent to the first edge; the shell cover is provided with a groove, the groove includes at least a first groove section and a second groove section, and when observed along a first direction, the first groove section and the second groove section are curved, and the first direction is the thickness direction of the shell cover; the first groove section includes a first end and a second end, the first end is connected to the second groove section, and the second end is the end of the groove, the first groove section extends in a direction away from the second edge, and along the extension direction from the first end to the second end, the first groove section is parallel to the first edge or the first groove section gradually moves away from the first edge.

2. The secondary battery according to claim 1, characterized in that: The groove also includes a third groove section, and when viewed along the first direction, the third groove section is curved; the third groove section includes a third end and a fourth end, the third end is connected to an end of the second groove section away from the first groove section, and the fourth end is the end of the groove, the third groove section extends in a direction away from the first edge, and along the extension direction from the third end to the fourth end, the third groove section is parallel to the second edge or the third groove section gradually moves away from the second edge.

3. The secondary battery according to claim 2, characterized in that: The first slot segment and / or the third slot segment transitions to the second slot segment with a rounded corner.

4. The secondary battery according to claim 2 or 3, characterized in that: When viewed along the first direction, the first slot segment and / or the third slot segment is in a straight line shape.

5. The secondary battery according to claim 4, characterized in that: The shell has a first bisector and a second bisector, the first bisector bisects the first edge and is parallel to the second edge, the second bisector bisects the second edge and is parallel to the first edge, and the first bisector intersects with the second bisector; when viewed along the first direction, the groove does not overlap with the first bisector and the groove does not overlap with the second bisector.

6. The secondary battery according to claim 5, characterized in that: The distance between the first end and the first edge is d1, the distance between the third end and the second edge is d2, d1≥1 mm and / or d2≥1 mm.

7. The secondary battery according to claim 4, characterized in that: The included angle between the first slot segment and the first edge is θ1, the included angle between the third slot segment and the second edge is θ2, 30°≤θ1≤60° and / or 30°≤θ2≤60°.

8. The secondary battery according to claim 1, characterized in that: Observed along the first direction, the second slot segment is in an arc shape, the center of the second slot segment and the intersection of the first edge and the second edge are located on the same side of the second slot segment, and the extension line of the second slot segment intersects the first edge and the second edge respectively.

9. The secondary battery according to claim 1, characterized in that: The outer shell is a steel shell, and the shell body and the shell cover are connected by welding.

10. The secondary battery according to claim 1, characterized in that: Along the first direction, the recessed depth of the groove is n1, the thickness of the shell cover is n2, and 0.35n2≤n1≤0.75n2.

11. The secondary battery according to any one of claims 1 to 10, characterized in that: The maximum width of the groove is W, 0.05mm≤W≤0.2mm.

12. An electrical equipment, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 11.

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