Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, battery pack and electronic device, the secondary battery includes: shell and electrode subassembly, shell includes end wall and surrounding the side wall of end wall, side wall and end wall are integrally stretched and formed, side wall and end wall are connected through transition fillet, and the electrode subassembly includes the end wall and end wall. The transition fillet comprises a first boundary line connected with the outer surface of the end wall and a second boundary line connected with the outer surface of the side wall; the electrode assembly is accommodated in the shell; the distance between the first boundary line and the second boundary line along the radial direction of the secondary battery is W1, the distance between the first boundary line and the second boundary line along the height direction of the secondary battery is H1, and H1 / W1 is greater than or equal to 1, so that the strength of a connecting area between the end wall and the side wall can be improved, and the service life of the battery can be prolonged.

Description

TECHNICAL FIELD

[0001] The utility model relates to a battery technical field, concretely relates to a secondary battery, battery pack and electronic device. BACKGROUND

[0002] At present, cylindrical batteries are widely used in various industries due to their mature production process, high yield, low processing cost, good safety performance and heat dissipation performance.

[0003] In order to ensure the capacity density of the battery and the strength of the shell, the current manufacturing process usually limits the thickness of the end wall and the side wall when stretching the shell, however, the connection area between the end wall and the side wall is a corner during the stretch forming, which will cause stress concentration in the connection area, and has a certain influence on the strength of the battery shell and the service life of the battery. SUMMARY

[0004] The utility model provides a secondary battery, battery pack and electronic device to improve the strength of the connection area between the end wall and the side wall and improve the service life of the battery.

[0005] To achieve the above object and other related purposes, the utility model provides a secondary battery, battery pack and electronic device, the secondary battery includes: shell and electrode assembly, the shell includes end wall and the side wall around the end wall, the side wall and the end wall are integrally stretch formed, the side wall and the end wall are connected through transition fillet, and the transition fillet includes the first intersection line of the outer surface of the end wall and the second intersection line of the outer surface of the side wall;The electrode assembly is contained in the shell;Along the radial direction of the secondary battery, the distance of the first intersection line and the second intersection line is W1, along the height direction of the secondary battery, the distance of the first intersection line and the second intersection line is H1, and H1 / W1 is greater than or equal to 1.

[0006] In the above technical scheme, the side wall and the end wall are connected through the transition fillet, and the distance of the first intersection line and the second intersection line in the transition fillet along the height direction of the secondary battery is greater than or equal to the distance along the radial direction of the secondary battery, which can realize the smooth transition of the transition fillet to the side wall, first, it can alleviate the risk of rupture during stretching of the shell, second, the smooth transition fillet can reduce the possibility of interference between the shell and the tooling equipment, and third, the smooth transition fillet can also reduce the internal stress in the transition fillet, which is beneficial to the improvement of the strength and service life of the shell.

[0007] In the secondary battery example of the utility model, the side wall includes a variable wall thickness area and a uniform thickness area, the variable wall thickness area extends from the transition fillet to the uniform thickness area, and the thickness of the variable wall thickness area gradually stretches to the same thickness as the uniform thickness area, and H1 / W1 is less than or equal to 3.

[0008] In the technical solution, the variable wall thickness area can realize smooth transition from the transition round corner to the uniform wall thickness area of the side wall, which can prevent tensile fracture caused by sharp transition and facilitate the release of internal stress, thereby improving the strength and service life of the shell.H1 / W1≤3 limits the height of the transition round corner within a proper range, which can prevent the height of H1 from being too large to affect the entry of the electrode assembly into the shell, and prevent the unnecessary overlap of the variable wall thickness area and the electrode assembly, thereby improving the electrical performance of the secondary battery.

[0009] In the example of the secondary battery, H1-W1≤0.2mm.

[0010] In the technical solution, the difference between H1 and W1 is kept within 0.2mm, which can ensure the smoothness of the transition round corner and further limit the unnecessary overlap of the variable wall thickness area and the electrode assembly, thereby alleviating the technical problem of uneven pressure on the electrode assembly and improving the electrical performance of the secondary battery.

[0011] In the example of the secondary battery, the secondary battery further comprises a pole column penetrating the end wall, the pole column is electrically connected with the electrode assembly, and the distance from the second boundary line to the outside of the end wall is less than the distance from one end of the pole column close to the electrode assembly to the outside of the end wall along the height direction of the secondary battery.

[0012] In the technical solution, the distance from the second boundary line to the outside of the end wall is less than the distance from the lower surface of the pole column to the outside of the end wall, which can avoid the influence of the transition round corner on the entry of the electrode assembly into the shell, and the space of the shell can be fully utilized to improve the energy density of the secondary battery.

[0013] In the example of the secondary battery, the wall thickness of the end wall is A, and 1≤W1 / A≤2.5.

[0014] In the technical solution, the limitation of W1 / A≥1 can weaken the stress concentration of the transition round corner, thereby alleviating the problems of fracture and damage of the plating layer of the shell during the stretching process, and the limitation of W1 / A≤2.5 can prevent the transition round corner from occupying too much internal space of the shell, thereby improving the space utilization and energy density of the secondary battery.

[0015] In the example of the secondary battery, 0.8mm≤W1≤2mm.

[0016] In the technical solution, the setting can weaken the stress concentration of the transition round corner, thereby alleviating the problems of fracture and damage of the plating layer of the shell during the stretching process, and can prevent the transition round corner from occupying too much internal space of the shell, thereby improving the space utilization and energy density of the secondary battery.

[0017] In the secondary battery example of the utility model, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a diaphragm laminated and wound to form a winding body, the positive electrode sheet includes a first coating area coated with a positive electrode active material and a first non-coating area without the positive electrode active material, the negative electrode sheet includes a second coating area coated with a negative electrode active material and a second non-coating area without the negative electrode active material, along the axial direction of the electrode assembly, the electrode assembly includes a reaction area and two non-reaction areas respectively located on both sides of the reaction area, the reaction area is the part where the first coating area and the second coating area coincide along the radial direction of the electrode assembly, the non-reaction area is the part with only the first coating area or only the second coating area, the distance from the boundary line between the non-reaction area close to the one side of the end wall and the reaction area to the inner side of the end wall is L1, the distance from the one end of the variable wall thickness area away from the transition fillet to the inner side of the end wall is L2, L1 >= L2.

[0018] In the above technical solution, during the charging and discharging process of the battery, since the first coating area and the second coating area in the reaction area of the electrode assembly coincide along the radial direction of the electrode assembly, the reaction area expands cumulatively in the radial direction, the expansion force is large, and a large pressure is applied to the side wall, and the non-reaction area of the electrode assembly does not expand because it only has the first coating area or the second coating area, so the distance from the boundary line between the non-reaction area and the reaction area to the inner side of the end wall is greater than or equal to the distance from the one end of the variable wall thickness area away from the transition fillet to the inner side of the end wall, which can realize that the reaction area does not coincide with the variable wall thickness area, but coincides with the uniform wall thickness area of the side wall, which can prevent the reaction area from pressing the variable wall thickness area first during expansion, thereby preventing the shell from being broken at the variable wall thickness area, and the pressure applied to the side wall during the expansion of the electrode assembly is uniform, thereby improving the safety performance of the battery.

[0019] In the secondary battery example of the utility model, the thickness difference of the uniform thickness area wall thickness is less than or equal to 0.08mm.

[0020] In the above technical solution, the thickness difference of the uniform thickness area wall thickness is less than or equal to 0.08mm, which helps to maintain the uniform strength of the side wall and avoid forming areas with different strengths on the side wall. When the electrode assembly expands, the side wall with uniform thickness can provide uniform pressure to the electrode assembly, thereby ensuring that the electrode assembly is evenly supported during the expansion process. This helps to prevent the shell from being broken due to the existence of weak areas when bearing internal pressure. In addition, the durability and safety of the shell are improved, and the overall performance of the battery is also optimized.

[0021] In the secondary battery example of the utility model, the transition fillet includes a third boundary line connected with the inner surface of the end wall and a fourth boundary line connected with the inner surface of the side wall, along the radial direction of the secondary battery, the distance between the third boundary line and the fourth boundary line is W2, along the height direction of the secondary battery, the distance between the third boundary line and the fourth boundary line is H2, 1 <= H2 / W2 <= 3.

[0022] In the technical solution, the distance between the third junction line and the fourth junction line along the height direction of the secondary battery is greater than or equal to the distance along the radial direction of the secondary battery, which can realize the smooth transition of the transition fillet to the side wall, on the one hand, the risk of fracture of the shell during stretching can be alleviated, on the other hand, the smooth transition fillet can also reduce the internal stress inside the transition fillet, which is beneficial to the improvement of the strength of the shell. H2 / W2≤3 limits the height H2 of the transition fillet within a suitable range, on the one hand, the unnecessary overlap of the variable wall thickness area and the electrode assembly is avoided, and the uneven pressure on the electrode assembly is prevented, thereby improving the electrical performance of the battery. On the other hand, it can also prevent the transition fillet from occupying too much space inside the shell, which is beneficial to improve the space utilization and energy density of the secondary battery.

[0023] In an example of the secondary battery of the utility model, 0.3mm≤W2≤0.9mm.

[0024] In the technical solution, the limitation can not only weaken the stress concentration of the transition fillet, thereby alleviating the problems of fracture of the shell during stretching and damage of the plating layer, but also prevent the transition fillet from occupying too much space inside the shell, which is beneficial to improve the space utilization and energy density of the secondary battery.

[0025] The utility model also provides a battery pack, the battery pack includes the secondary battery of any one of the above.

[0026] The utility model also provides an electronic device, the electronic device includes the battery pack of above.

[0027] In the secondary battery of the utility model, the side wall and the end wall are connected through the transition fillet, the distance between the first junction line and the second junction line in the transition fillet along the height direction of the secondary battery is greater than the distance along the radial direction of the secondary battery, which can realize the smooth transition of the transition fillet to the side wall. First, the risk of fracture of the shell during stretching can be alleviated, second, the smooth transition fillet can reduce the possibility of interference between the shell and the tooling equipment, and third, the smooth transition fillet can also reduce the internal stress inside the transition fillet, which is beneficial to the improvement of the strength and service life of the shell. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the utility model or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the utility model, and those skilled in the art can also obtain other embodiments according to these drawings without creating any creative labor.

[0029] Figure 1 It is a structural schematic view of an embodiment of the secondary battery of the utility model;

[0030] Figure 2 Structure diagram of the shell of the secondary battery according to an embodiment of the present application;

[0031] Figure 3 Structure diagram of the electrode assembly of the secondary battery according to an embodiment of the present application; Figure 2 Enlarged view of part B;

[0032] Figure 4 Structure diagram of the electrode assembly of the secondary battery according to an embodiment of the present application;

[0033] Figure 5 Structure diagram of the electrode assembly of the secondary battery according to an embodiment of the present application; Figure 1 Enlarged view of part A;

[0034] Figure 6 Structure diagram of the square shell battery according to an embodiment of the present application;

[0035] Figure 7 Sectional view of the square shell battery according to an embodiment of the present application;

[0036] Figure 8 Structure diagram of the battery pack according to an embodiment of the present application;

[0037] Figure 9 Structure diagram of the electronic device according to an embodiment of the present application.

[0038] Element number explanation

[0039] 1, electronic device; 10, battery pack; 11, working part; 101, box body; 102, box cover; 100, secondary battery; 110, shell; 111, end wall; 112, side wall; 1121, variable wall thickness area; 1122, uniform thickness area; 113, opening; 114, transition fillet; 1141, first boundary line; 1142, second boundary line; 1143, third boundary line; 1144, fourth boundary line; 120, electrode assembly; 121, positive plate; 1211, positive current collector; 1212, first coating area; 1213, first non-coating area; 122, separator; 123, negative plate; 1231, negative current collector; 1232, second coating area; 1233, second non-coating area; 124, positive tab; 125, negative tab; 126, winding body; 127, reaction area; 128, non-reaction area; 130, pole; 140, end cover. DETAILED DESCRIPTION

[0040] The embodiments of the present application will be described in detail with specific examples. Those skilled in the art can easily understand other advantages and functions of the present application from the content disclosed in the specification. The present application can also be implemented or applied in other different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following examples and features in the examples can be combined with each other without conflict. It should also be understood that the terms used in the embodiments of the present application are for describing specific specific embodiments, not for limiting the protection scope of the present application. The test methods in the following examples are not specified, and are usually performed under conventional conditions or under conditions recommended by the manufacturers.

[0041] When the embodiments give a numerical range, it should be understood that, unless otherwise stated by the present application, each numerical range and any number between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present application are consistent with the understanding of the prior art by those skilled in the art and the description of the present application. Any method, device and material of the prior art similar or equivalent to the method, device and material in the embodiments of the present application can be used to realize the present application.

[0042] It should be understood that the terms such as "up", "down", "left", "right", "middle" and "one" in the specification are only for the convenience of clear description, not for limiting the scope of the present application. The change or adjustment of the relative relationship without substantial change of the technical content is also regarded as the scope of the present application.

[0043] The secondary battery includes an electrode assembly, which is a component where an electrochemical reaction occurs in the secondary battery, and can include one or more electrode assemblies.

[0044] The secondary battery further includes a case, an end cover and a pole, the case includes an end wall and a side wall surrounding the end wall, the end wall and the side wall are integrally stretch formed, one end of the side wall has an opening, the electrode assembly can be assembled into the case through the opening of the case, the end cover is used to cover the opening of the case to realize sealing, and the pole is electrically connected with the electrode assembly through the end wall to guide the electric energy generated by the electrode assembly out.

[0045] The secondary battery uses the structure of assembling the electrode assembly with the steel case, which is encapsulated by the case to isolate the external environment, and plays a protective role in the electrochemical reaction of the internal active material. At the same time, the side wall of the case has a greater constraint effect on the radial expansion of the electrode assembly. With the improvement of the performance requirements of the battery, in order to ensure the capacity density of the battery and the strength of the case, in some embodiments, the thickness of the end wall and the side wall is limited when the case is stretched.

[0046] However, the inventors find that the connection area between the end wall and the side wall is a corner during the stretch forming, which causes stress concentration in the connection area, and has certain influence on the strength of the battery shell and the service life of the battery. Therefore, the connection area needs to be improved during the design and manufacturing process to improve the strength and service life of the battery shell.

[0047] In view of this, the utility model provides a technical scheme, the side wall and the end wall are connected through the transition fillet, the distance between the first intersection line and the second intersection line in the transition fillet along the height direction of the secondary battery is greater than or equal to the distance along the radial direction of the secondary battery, which can realize the gentle transition of the transition fillet to the side wall, and is beneficial to the improvement of the strength and service life of the shell.

[0048] Please refer to Figures 1 to 9 The utility model provides a kind of secondary battery 100, which comprises a shell 110, an electrode assembly 120, a pole 130 and an end cover 140.

[0049] Please refer to Figure 1 And Figure 2 The shell 110 includes an end wall 111 and a side wall 112 surrounding the end wall 111. The side wall 112 and the end wall 111 are integrally stretch formed. The stretch forming process is a stamping process that uses a stretch die to press a sheet blank into a hollow piece with various openings 113. Specifically, in this embodiment, a suitable die is first selected according to the target shape of the shell 110. For example, the shape of the shell 110 can be a square shell, a cylindrical shell or a polygonal prism shell, etc. Then the blank is stamped. In the first step, the end wall 111, the side wall 112 and the rudiment of the cavity are stamped out. To ensure the reliability of the stretch forming and avoid stretch fracture, different size dies are replaced multiple times and the stamping is performed multiple times until the stretch forming reaches the preset size.

[0050] In some embodiments, the shape of the shell 110 can be a square shell, as shown in Figure 6 And Figure 7 In this embodiment, as shown in Figure 1 The outer edge of the end wall 111 is circular, and the side wall 112 is in the form of a cylinder surrounding the outer edge of the end wall 111 and has a circular opening 113 at the end away from the end wall 111. The end wall 111 and the side wall 112 enclose a receiving cavity in the shell 110 for accommodating the electrode assembly 120, electrolyte and other necessary components of the battery. Specifically, the diameter of the shell 110 can be determined according to the specific size of the electrode assembly 120, such as 18 mm, 21 mm, 46 mm, etc. The shell 110 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. To prevent rusting of the shell 110 during long-term use, a layer of rust-resistant material such as metallic nickel can be plated on the surface of the shell 110.

[0051] Considering that the directions of the end wall 111 and the side wall 112 change, the connection area between the end wall 111 and the side wall 112 is a corner, which causes a problem of stress concentration in the connection area. In the embodiment, referring to Figure 3 and Figure 5 , the side wall 112 and the end wall 111 are connected through a transition round corner 114. The transition round corner 114 can be tangent to the side wall 112 or connected to the side wall 112. The transition round corner 114 can be tangent to the end wall 111 or connected to the end wall 111. No limitation is made to this. Preferably, the transition round corner 114 is tangent to both the end wall 111 and the side wall 112, which can avoid the occurrence of a corner point and improve the flatness of the surface.

[0052] Further, referring to Figure 3 and Figure 5 , the transition round corner 114 includes a first boundary line 1141 connected to the outer surface of the end wall 111 and a second boundary line 1142 connected to the outer surface of the side wall 112. The distance between the first boundary line 1141 and the second boundary line 1142 along the radial direction of the secondary battery 100 is W1, and the distance between the first boundary line 1141 and the second boundary line 1142 along the height direction of the secondary battery 100 is H1, and H1 / W1≥1. That is, the distance between the first boundary line 1141 and the second boundary line 1142 in the transition round corner 114 along the height direction of the secondary battery 100 is greater than or equal to the distance along the radial direction of the secondary battery 100. This setting can achieve a smooth transition of the transition round corner 114 to the side wall 112, can alleviate the risk of fracture of the shell 110 when stretched, in addition, the smooth transition round corner 114 can reduce the possibility of interference between the shell 110 and the tooling equipment when the secondary battery 100 is placed in the tooling equipment for subsequent processes, and again, the smooth transition round corner can also reduce the internal stress in the transition round corner 114, which is beneficial to the improvement of the strength and service life of the shell 110.

[0053] It should be noted that the first boundary line 1141 is the outermost edge line that is coplanar with the outer surface of the end wall 111, and the second boundary line 1142 is the edge line on the side wall 112 that is closest to the end wall 111 and coplanar with the outer surface of the side wall 112. The measurement method of W1 and H1 is as follows: along the height direction of the secondary battery 100, a cross section of the shell 110 is made, and an extension line is made along the outer surface of the end wall 111 and the outer surface of the side wall 112, respectively. The two extension lines intersect at a point. W1 is the distance from the intersection point to the first boundary line 1141, and H1 is the distance from the intersection point to the second boundary line 1142.

[0054] Referring to Figure 1 , Figure 4 and Figure 5The electrode assembly 120 is accommodated in the case 110, and is a component in which an electrochemical reaction occurs in the lithium ion secondary battery 100. One or more electrode assemblies 120 can be included in the case 110. The electrode assembly 120 includes a positive electrode tab 121, a negative electrode tab 123, and a separator 122 laminated and wound to form a wound body 126. Specifically, the positive electrode tab 121 includes a positive electrode current collector 1211 and a positive electrode active material coated on a surface of the positive electrode current collector 1211; the positive electrode current collector 1211 includes a first coated region 1212 coated with the active material and a first uncoated region 1213 not coated with the active material, the first uncoated region 1213 being located at an end of the positive electrode tab 121, the first uncoated region 1213 extending beyond the separator 122 in a direction of a winding axis of the electrode assembly 120 and being bent toward the winding axis to form a positive electrode tab 124. The negative electrode tab 123 includes a negative electrode current collector 1231 and a negative electrode active material coated on a surface of the negative electrode current collector 1231; the negative electrode current collector 1231 includes a second coated region 1232 coated with the active material and a second uncoated region 1233 not coated with the active material, the second uncoated region 1233 being located at an end of the negative electrode tab 123, the second uncoated region 1233 extending beyond the separator 122 in the direction of the winding axis of the electrode assembly 120 and being bent toward the winding axis to form a negative electrode tab 125.

[0055] Referring to Figure 1 , Figure 4 and Figure 5 , the separator 122 is disposed between the positive electrode tab 121 and the negative electrode tab 123 to separate the positive electrode active material layer and the negative electrode active material layer. In the case of the lithium ion secondary battery 100, the material of the positive electrode current collector 1211 can be aluminum, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material can be lithium cobaltate, lithium iron phosphate, ternary lithium, or lithium manganate, etc. The material of the negative electrode current collector 1231 can be copper, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material can be carbon or silicon, etc. The base material of the separator 122 can be polypropylene (PP) or polyethylene (PE), etc. In order to protect and insulate the electrode assembly 120, an insulating film can be coated on the outside of the electrode assembly 120, and the insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other high-molecular polymer materials.

[0056] Referring to Figure 1 , Figure 4 and Figure 5Further, the positive tab 124 faces the end wall 111 or the opening 113, and the negative tab 125 faces the other end of the shell 110. In this embodiment, the positive tab 124 faces the end wall 111, and the pole 130 is electrically connected to the positive tab 124 to make the pole 130 positively charged. The negative tab 125 faces the opening 113, and the shell 110 is electrically connected to the negative tab 125 to make the shell 110 negatively charged. However, in another embodiment, the negative tab 125 can be connected to the pole 130, and the positive tab 124 can be connected to the shell 110.

[0057] Referring to Figure 1 In this embodiment, the secondary battery 100 further comprises a pole 130. Specifically, the pole 130 penetrates the end wall 111 and is insulated from the end wall 111. The pole 130 is directly or indirectly electrically connected to the positive tab 124 at one end of the pole 130 that penetrates the end wall 111 and faces the electrode assembly 120. The pole 130 can have any suitable form that allows the pole 130 to penetrate the end wall 111 and be electrically connected to the positive tab 124 of the electrode assembly 120. For example, the pole 130 can have a circular, square, prismatic, or any other suitable cross-sectional shape that allows stable electrical conduction. The pole 130 hole corresponds to the shape of the pole 130. In this embodiment, the pole 130 has a circular cross-section.

[0058] Referring to Figure 1 In this embodiment, the secondary battery 100 further comprises an end cover 140. The end cover 140 is sealingly installed in the opening 113. The outer edge of the end cover 140 corresponds to the shape of the opening 113 and is connected to the side wall 112 to seal the opening 113.

[0059] Since the end wall 111 is only stamped in the first step and does not undergo subsequent stretching, the wall thickness of the end wall 111 is approximately equal to the thickness of the original material, i.e., the blank. The side wall 112, however, needs to be stamped multiple times until it is stretched to the predetermined size. Abrupt changes in size can easily lead to stress concentration, reduced elongation, and reduced structural strength. Referring to Figures 1 to 3 and Figure 5 In one example of the secondary battery 100 of the present application, the side wall 112 comprises a variable-thickness region 1121 and a uniform-thickness region 1122. The variable-thickness region 1121 extends from the transition fillet 114 to the uniform-thickness region 1122, and the thickness of the variable-thickness region 1121 gradually increases to the same thickness as the uniform-thickness region 1122. It can be understood that the thicker end of the variable-thickness region 1121 is connected to the transition fillet 114, and the thickness is equal to the thickness at the connection between the transition fillet 114 and the variable-thickness region 1121. The provision of the variable-thickness region 1121 allows for a gradual transition from the transition fillet 114 to the uniform-thickness region of the side wall 112. This can prevent stretching fractures caused by abrupt transitions and facilitate the release of internal stress, thereby improving the strength and service life of the shell 110.

[0060] Please refer to Figures 1 to 3 and Figure 5 Since the thick part of the variable-thickness region 1121 occupies more internal space of the shell 110, further, the limitation of H1 / W1≤3 can limit the height of the transition round corner 114 within a suitable range, on the one hand, preventing the height of H1 from being too large to affect the entry of the electrode assembly 120 into the shell, and on the other hand, preventing the unnecessary overlap of the variable-thickness region 1121 and the electrode assembly 120, and the technical problem of uneven pressure on the electrode assembly 120, thereby improving the electrical performance of the secondary battery 100.

[0061] Please refer to Figures 1 to 3 and Figure 5 In an example of the secondary battery 100 of the present application, H1-W1≤0.2mm, for example, it can be 0.05mm, 0.1mm, 0.15mm or 0.2mm. Keeping the difference between H1 and W1 within 0.2mm can not only ensure the smoothness of the transition round corner 114, but also further limit the unnecessary overlap of the variable-thickness region 1121 and the electrode assembly 120, to alleviate the technical problem of uneven pressure on the electrode assembly 120, thereby improving the electrical performance of the secondary battery 100.

[0062] Since the end of the pole 130 towards the electrode assembly 120 is directly or indirectly electrically connected to the positive electrode tab 124 of the electrode assembly 120, to prevent the transition round corner 114 from affecting the electrical connection between the electrode assembly 120 and the pole 130 due to occupying more internal space of the shell 110, in an example of the secondary battery 100 of the present application, please refer to Figure 1 and Figure 5 The distance from the second boundary line 1142 to the outside of the end wall 111 is less than the distance from the end of the pole 130 close to the electrode assembly 120 to the outside of the end wall 111 along the height direction of the secondary battery 100. This setting can avoid the transition round corner 114 affecting the entry of the electrode assembly 120 into the shell, and at the same time, the space of the shell 110 can be fully utilized to improve the energy density of the secondary battery 100.

[0063] Please refer to Figure 2 and Figure 3 In an example of the secondary battery 100 of the present application, the wall thickness of the end wall 111 is A, and 1≤W1 / A≤2.5. The limitation of W1 / A≥1 can weaken the stress concentration of the transition round corner 114, thereby alleviating the problem of fracture of the shell 110 during stretching and damage to the plating layer, and the limitation of W1 / A≤2.5 can prevent the transition round corner 114 from occupying too much internal space of the shell 110, which is beneficial to improve the space utilization and energy density of the secondary battery.

[0064] In the secondary battery 100 example of the utility model, the radial distance W1 of the first boundary line 1141 and the second boundary line 1142 is limited to the range of 0.8mm≤W1≤2mm, for example, it can be 0.8mm, 1.0mm, 1.2mm, 1.5mm, 1.8mm or 2mm etc., the setting can weaken the stress concentration of the transition fillet 114, then relieve the problem of the shell 110 fracture and plating damage in the stretching process, also can prevent the transition fillet 114 from occupying too much inside space of the shell 110, improve the space utilization and energy density of the secondary battery.

[0065] Please refer to Figure 4 And Figure 5 In the secondary battery 100 example of the utility model, along the axial direction of the electrode assembly 120, the electrode assembly 120 includes a reaction zone 127 and two non-reaction zones 128 located on both sides of the reaction zone 127, and the reaction zone 127 is the part where the first coating area 1212 and the second coating area 1232 coincide in the radial direction of the electrode assembly 120. During the charging and discharging process of the battery, since the first coating area 1212 and the second coating area 1232 in the reaction zone 127 of the electrode assembly 120 coincide in the radial direction of the electrode assembly 120, the reaction zone 127 expands in the radial direction, and the expansion force is large, which can exert a large pressure on the side wall 112. The non-reaction zone 128 is the part with only the first coating area 1212 or only the second coating area 1232. The non-reaction zone 128 does not expand. It should be noted that when the positive electrode tab 124 is close to the end wall 111, the non-reaction zone 128 on the side close to the end wall 111 is the part with only the first coating area 1212, and when the negative electrode tab 125 is close to the end wall 111, the non-reaction zone 128 on the side close to the end wall 111 is the part with only the second coating area 1232. In this embodiment, the positive electrode tab 124 is close to the end wall 111, and the non-reaction zone 128 on the side close to the end wall 111 has only positive active material and no negative active material, so there is no movement of lithium ions in the non-reaction zone 128, and no expansion occurs.

[0066] Further, please refer to Figure 4 And Figure 5 The distance from the boundary line between the non-reaction zone 128 on the side close to the end wall 111 and the reaction zone 127 to the inside of the end wall 111 is defined as L1, and the distance from the end of the variable wall thickness zone 1121 away from the transition fillet 114 to the inside of the end wall 111 is defined as L2, and L1≥L2 is limited. The reaction zone 127 does not coincide with the variable wall thickness zone 1121, but coincides with the uniform wall thickness zone of the side wall 112, which can prevent the reaction zone 127 from pressing the variable wall thickness zone 1121 first when expanding, causing the shell 110 to break at the variable wall thickness zone 1121, and also can achieve uniform pressure on the side wall 112 when the electrode assembly 120 expands, thereby improving the safety performance of the battery.

[0067] Referring to Figure 2 and Figure 3 In an example of the secondary battery 100 of the utility model, the thickness difference of the wall thickness of the thickness uniform region 1122 is less than or equal to 0.08mm, for example, can be 0, 0.01mm, 0.03mm, 0.05mm, 0.06mm, 0.07mm or 0.08mm, etc., which helps to maintain the uniform strength of the side wall 112, avoiding the formation of areas with uneven strength on the side wall 112. When the electrode assembly 120 expands, the side wall 112 with uniform thickness can provide uniform pressure to the electrode assembly 120, thereby ensuring that the electrode assembly 120 is evenly supported during expansion. It helps to prevent the shell 110 from rupturing when subjected to internal pressure due to the presence of weak areas. In addition, the durability and safety of the shell 110 are improved, and the overall performance of the battery is also optimized.

[0068] Referring to Figure 2 , Figure 3 and Figure 5 In an example of the secondary battery 100 of the utility model, the transition fillet 114 includes a third boundary line 1143 connected to the inner surface of the end wall 111 and a fourth boundary line 1144 connected to the inner surface of the side wall 112. Along the radial direction of the secondary battery 100, the distance between the third boundary line 1143 and the fourth boundary line 1144 is W2, and along the height direction of the secondary battery 100, the distance between the third boundary line 1143 and the fourth boundary line 1144 is H2, and 1≤H2 / W2≤3 is defined. Specifically, the setting of H2 / W2≥1 can realize the smooth transition of the transition fillet 114 to the side wall 112, on the one hand, it can alleviate the risk of rupture when the shell 110 is stretched, on the other hand, the smooth transition of the fillet can also reduce the internal stress inside the transition fillet 114, which is beneficial to the strength improvement of the shell 110. H2 / W2≤3 limits the height H2 of the transition fillet 114 within a suitable range, on the one hand, it avoids unnecessary overlap of the variable wall thickness region 1121 and the electrode assembly 120, preventing uneven pressure on the electrode assembly 120, thereby improving the electrical performance of the battery. On the other hand, it can also prevent the transition fillet 114 from occupying too much space inside the shell 110, which is beneficial to improving the space utilization and energy density of the secondary battery.

[0069] It should be noted that the third boundary line 1143 is the outermost circumferential line coplanar with the inner surface of the end wall 111, and the fourth boundary line 1144 is the line on the inner side of the side wall 112 closest to the end wall 111 and coplanar with the inner surface of the side wall 112. The measurement method of W2 and H2 is as follows: along the height direction of the secondary battery 100, a cross section of the shell 110 is made, and an extension line is made along the inner surface of the end wall 111 and the inner surface of the side wall 112, respectively. The two extension lines intersect at a point, W2 is the distance from the intersection point to the third boundary line 1143, and H2 is the distance from the intersection point to the fourth boundary line 1144. Please refer to Figure 2 、 Figure 3 and Figure 5 In an example of the secondary battery 100 of the present application, 0.3mm≤W2≤0.9mm, for example, it can be 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm or 0.9mm, etc. W2 in the above range can not only weaken the stress concentration of the transition fillet 114, thereby relieving the problem of cracking of the shell 110 during stretching and damage to the plating layer, but also can prevent the transition fillet 114 from occupying too much space inside the shell 110, which is beneficial to improve the space utilization and energy density of the secondary battery.

[0070] Please refer to Figure 8 The present application also provides a battery pack 10, which comprises the secondary battery 100 of any one of the above, and in an embodiment of the battery pack 10 of the present application, the battery pack 10 comprises a box body 101, a box cover 102 and a plurality of secondary batteries 100. The plurality of secondary batteries 100 are placed in the box body 101 and are connected in series or parallel with each other, or a combination of series and parallel connection. The box cover 102 is covered on the box body 101 to protect the plurality of secondary batteries 100. It should be noted that the battery pack 10 can also include a battery pack 10 thermal management system, a circuit board and other parts in addition to the secondary battery 100 of the present application. The battery pack 10 can be a battery module or a battery pack, and a storage battery cabinet, etc. Here, it will not be described one by one.

[0071] Please refer to Figure 9The application further provides an electronic device 1 comprising the battery pack 10. The working part 11 is electrically connected with the battery pack 10 to obtain power support. As an example, the electronic device 1 is a vehicle, which can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric vehicle, a hybrid vehicle or a range extended vehicle, but is not limited thereto. The working part 11 is a vehicle body, and the battery pack 10 is arranged at the bottom of the vehicle body and provides power support for driving of the vehicle or operation of electrical elements in the vehicle. However, in some other embodiments, the electronic device 1 can also be a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spacecraft, etc. The working part 11 can be a unit component capable of obtaining power of the battery pack 10 and making corresponding work, such as a fan blade rotating unit of a fan or a dust suction working unit of a dust collector. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric automobile toy, an electric ship toy and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator and an electric planer, etc. The embodiments of the application do not specially limit the above-mentioned electronic device 1.

[0072] The secondary battery of the utility model, the side wall and the end wall are connected through the transition fillet, the distance between the first interface line and the second interface line in the transition fillet along the height direction of the secondary battery is greater than the distance along the radial direction of the secondary battery, this setting can realize the gentle transition of the transition fillet to the side wall, first, can relieve the risk of fracture when the shell is stretched, second, the smooth transition fillet can reduce the possibility of interference between the shell and the tooling equipment, third, the gently transitioned fillet can also reduce the internal stress inside the transition fillet, which is beneficial to the improvement of the strength and service life of the shell. Therefore, the utility model effectively overcomes some practical problems in the prior art, thereby having high utilization value and use significance. The above embodiments only exemplarily illustrate the principle and effect of the utility model, and are not used to limit the utility model. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the utility model. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the utility model should be covered by the claims of the utility model.

Claims

1. A secondary battery characterized by comprising: The secondary battery comprises: a shell comprising an end wall and a side wall surrounding the end wall, the side wall and the end wall being integrally stretch-formed, the side wall and the end wall being connected by a transition round corner, the transition round corner comprising a first interface line connected with an outer surface of the end wall and a second interface line connected with an outer surface of the side wall; an electrode assembly accommodated in the shell; wherein, along a radial direction of the secondary battery, a distance between the first interface line and the second interface line is W1, along a height direction of the secondary battery, a distance between the first interface line and the second interface line is H1, and H1 / W1≥1.

2. The secondary battery according to claim 1, characterized by The side wall comprises a variable-thickness region and a uniform-thickness region, the variable-thickness region extending from the transition round corner to the uniform-thickness region, and a thickness of the variable-thickness region gradually stretching to be the same as a thickness of the uniform-thickness region, wherein H1 / W1≤3.

3. The secondary battery according to claim 2, characterized by H1-W1≤0.2mm.

4. The secondary battery according to claim 2, characterized by The secondary battery further comprises a pole post penetrating through the end wall, the pole post being electrically connected with the electrode assembly, along the height direction of the secondary battery, a distance from the second interface line to an outer side of the end wall being less than a distance from an end of the pole post close to the electrode assembly to the outer side of the end wall.

5. The secondary battery according to claim 2, characterized by A wall thickness of the end wall is A, wherein 1≤W1 / A≤2.

5.

6. The secondary battery according to claim 5, characterized by 0.8mm≤W1≤2mm.

7. The secondary battery according to claim 2, characterized by The electrode assembly comprises a wound body formed by stacking and winding a positive electrode sheet, a negative electrode sheet and a separator, the positive electrode sheet comprising a first coated region coated with a positive electrode active material and a first uncoated region not coated with the positive electrode active material, the negative electrode sheet comprising a second coated region coated with a negative electrode active material and a second uncoated region not coated with the negative electrode active material, along an axial direction of the electrode assembly, the electrode assembly comprising a reaction region and two non-reaction regions respectively located on two sides of the reaction region, the reaction region being a portion in which the first coated region and the second coated region coincide in a radial direction of the electrode assembly, the non-reaction region being a portion in which only the first coated region or only the second coated region exists, a distance from a boundary line between the non-reaction region close to the end wall and the reaction region to an inner side of the end wall being L1, and a distance from an end of the variable-thickness region away from the transition round corner to the inner side of the end wall being L2, wherein L1≥L2.

8. The secondary battery according to claim 7, characterized by A thickness difference of the uniform-thickness region is less than or equal to 0.08mm.

9. The secondary battery according to claim 2, characterized by The transition round corner comprises a third interface line connected with an inner surface of the end wall and a fourth interface line connected with an inner surface of the side wall, along a radial direction of the secondary battery, a distance between the third interface line and the fourth interface line is W2, along a height direction of the secondary battery, a distance between the third interface line and the fourth interface line is H2, and 1≤H2 / W2≤3.

10. The secondary battery according to claim 9, characterized by 0.3mm≤W2≤0.9mm.

11. A battery pack, characterized by The secondary battery comprises any one of the secondary batteries in claims 1 to 10.

12. An electronic device, comprising: The battery pack comprises the battery in claim 11.

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