Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery comprises a shell and an electrode assembly, the shell comprises an end wall and a side wall surrounding the end wall, and the axis of the shell is a first axis; the electrode assembly is accommodated in the shell, the electrode assembly comprises a winding structure formed by laminating and winding a positive pole piece, a negative pole piece and a diaphragm, the number of winding turns of the negative pole piece is greater than 40, and the axis of the winding structure is a second axis; when the SOC of the secondary battery 100 is smaller than 5%, the second axis is located in a cylindrical area with the first axis as the axis and the diameter d1 being phi 0.6 mm, and the technical problem of battery performance deterioration caused by local barren solution lithium precipitation of the electrode assembly can be solved.

Description

Technical Field

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

[0002] The existing large cylindrical batteries generally use a structure in which an electrode assembly is assembled with a steel shell. The shell is used for encapsulating to isolate the external environment, protecting the electrochemical reaction of the internal active substances. At the same time, the side wall of the shell has a large restraining effect on the radial expansion of the electrode assembly. In large cylindrical batteries, as the number of winding turns of the electrode sheet increases, the radial expansion amount of the electrode assembly also increases accordingly. It is detected that among the large cylindrical batteries of the same batch, some have the problem that the electrolyte between the electrode sheets is extruded in the later stage of cycling, resulting in local liquid deficiency and lithium precipitation, and the performance of the cylindrical battery deteriorates sharply, with great potential safety hazards. Summary of the Utility Model

[0003] In view of the above-mentioned disadvantages of the prior art, the utility model provides a secondary battery, a battery pack and an electronic device to improve the technical problem of battery performance deterioration caused by local liquid deficiency and lithium precipitation of the electrode assembly.

[0004] To achieve the above-mentioned purpose and other related purposes, the utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery includes a shell and an electrode assembly; the shell includes an end wall and a side wall surrounding the end wall, and the axis of the shell is the first axis; the electrode assembly is accommodated in the shell, and the electrode assembly includes a winding structure formed by laminating and winding a positive electrode sheet, a negative electrode sheet and a separator, wherein the number of winding turns of the negative electrode sheet is greater than 40 turns, and the axis of the winding structure is the second axis; in a state where the SOC (State of Charge) of the secondary battery is less than 5%, the second axis is located in a cylindrical region with the first axis as the axis and a diameter d1 of φ0.6 mm.

[0005] In the above technical solution, considering that the number of winding turns of the electrode sheet in a large cylindrical battery is usually greater than 40 turns, the increase in the number of turns leads to a corresponding increase in the accumulated expansion amount of the electrode assembly. When the electrode assembly is eccentric to one side of the shell, the influence of the uneven stress of the shell on the electrode assembly will be more obvious. By defining that in a state where the SOC of the secondary battery is less than 5% (State of Charge), the second axis is located in a cylindrical region with the first axis as the axis and a diameter d1 of φ0.6 mm, the coaxiality of the electrode assembly and the shell can be improved, so that there is a relatively uniform safety gap between the electrode assembly and the inner wall of the shell, alleviating the problem of uneven stress of the shell on the electrode assembly during the charge and discharge process of the battery, improving the problem of local liquid deficiency and lithium precipitation, and achieving the effect of improving the safety performance.

[0006] In an example of the secondary battery of the present utility model, the electrode assembly further includes a finishing adhesive that winds more than one turn around the outer periphery of the winding structure. Along the winding direction of the winding structure, the terminal of the finishing adhesive bypasses the starting end of the finishing adhesive and forms an overlapping portion, and the distance between the overlapping portion and the side wall is greater than or equal to 0.2 mm.

[0007] In the above technical solution, in order to better fix the winding structure, a finishing adhesive is wound around the outer periphery of the winding structure, and the terminal of the finishing adhesive bypasses the starting end of the finishing adhesive and forms an overlapping portion. The radial dimension of the position where the overlapping portion is located is relatively large. Therefore, the distance between the overlapping portion and the side wall is limited to be greater than or equal to 0.2 mm to achieve a safe gap between the overlapping portion and the side wall, and relieve the problem that when the battery expands during charging, the overlapping portion is easily squeezed with the side wall, resulting in the extrusion of the electrolyte and local lithium deposition.

[0008] In an example of the secondary battery of the present utility model, the secondary battery further includes a pole column, a first current collector member, and a coating layer. The pole column penetrates the end wall and is insulated from the end wall. The end of the positive electrode tab includes a positive electrode ear bent toward the second axis. One side of the first current collector member is fixedly connected to the pole column, and the other side of the first current collector member is fixedly connected to the positive electrode ear. The coating layer at least insulates the positive electrode ear from the housing. The coating layer includes a first covering portion and a second covering portion connected to the first covering portion. The first covering portion covers the edge of the first current collector member, and the second covering portion covers the outer periphery of one end of the electrode assembly close to the first current collector member. The second covering portion includes a compressible elastic layer, and the thickness b of the second covering portion ranges from: b ≤ 0.2 mm.

[0009] In the above technical solution, in order to insulate and isolate the exposed ear close to the outer side of the winding structure from the housing, a coating layer is provided at the edge of the first current collector member and one end of the electrode assembly close to the first current collector member. The coating layer can, on the one hand, insulate the positive electrode ear from the housing, and on the other hand, can wrap the exposed positive electrode ear to protect the positive electrode ear and reduce the risk of the positive electrode ear breaking and falling into the battery to cause a short circuit. Further, the second covering portion includes a compressible elastic layer, and the thickness range of the second covering portion is b ≤ 0.2 mm. On the one hand, the second covering portion with a certain thickness can play a pre-guiding role when the electrode assembly is placed in the housing, so that there is at least a gap equal to the thickness of the second covering portion between the electrode assembly and the side wall, improving the coaxiality of the electrode assembly and the housing, reducing the problem of uneven stress of the housing on the electrode assembly caused by the electrode assembly being eccentric to one side of the housing, and improving the problem of local poor-liquid lithium deposition, so as to achieve the effect of improving the safety performance. In addition, the second covering portion has a compressible property, which can reduce the thickness when the battery expands and reduce the effect of stress concentration.

[0010] In an example of the secondary battery of the present utility model, the first covering portion also includes an elastic layer and is integrally formed with the second covering portion. The encapsulation layer further includes a first adhesive layer for adhesively fixing the elastic layer to the electrode assembly and the first current collector member.

[0011] In the above technical solution, the integrally formed structure of the first covering portion and the second covering portion can simplify the process of packaging the encapsulation layer and improve the processing efficiency.

[0012] In an example of the secondary battery of the present utility model, the second covering portion includes a base layer integrally formed with the first covering portion, an elastic layer, and a second adhesive layer for adhesively bonding the base layer and the elastic layer.

[0013] In the above technical solution, only the second covering portion is provided with an elastic layer, which can improve the coaxiality of the electrode assembly and the housing while having a relatively low material cost.

[0014] In an example of the secondary battery of the present utility model, the end portion of the positive electrode tab includes a positive electrode ear that extends out of the separator along the second axis toward the end wall and is bent toward the second axis. The secondary battery further includes at least an insulating plastic for isolating the positive electrode ear and the housing. The insulating plastic includes a first insulator and a second insulator. The first insulator is located between the positive electrode ear and the end wall, and the second insulator is located between the side wall and the electrode assembly.

[0015] In the above technical solution, the insulating plastic can isolate and insulate the positive electrode ear and the housing. The first insulator is mainly used to isolate the positive electrode ear and the end wall, and the second insulator is mainly used to isolate the exposed positive electrode ear and the side wall. At the same time, the second insulator can also play a role in limiting the position between the electrode assembly and the side wall, so that there is at least a gap of the thickness of the second insulator between the electrode assembly and the side wall, which can improve the coaxiality of the electrode assembly and the housing, reduce the problem of uneven stress on the electrode assembly caused by the electrode assembly being eccentric to one side of the housing, and improve the problem of local poor liquid segregation and lithium deposition, so as to achieve the effect of improving the safety performance.

[0016] In an example of the secondary battery of the present utility model, a chamfer is provided on the inner wall of the end of the second insulator away from the first insulator.

[0017] In the above technical solution, the provision of the chamfer can play a role in pre-guiding when the electrode assembly is placed into the housing, improve the assembly efficiency, and can also reduce the contact area between the electrode assembly and the second insulator, which is beneficial to heat dissipation.

[0018] In an example of the secondary battery of the present utility model, a third adhesive layer for adhesively fixing the second insulator and the side wall is provided on the outer side of the second insulator.

[0019] In the above technical solution, the third adhesive layer is used for bonding and fixing between the second insulator and the side wall, avoiding gaps between the second insulator and the side wall, preventing interference when the second insulator is inserted into the housing during the installation of the electrode assembly. This setting facilitates the insertion of the electrode assembly into the housing, and can achieve the effects of improving the assembly efficiency and assembly quality.

[0020] In an example of the secondary battery of the present utility model, the end of the negative electrode tab includes a negative electrode tab that extends out of the separator in a direction away from the end wall along the second axis and is bent toward the second axis. The secondary battery further includes a second current collector member, the second current collector member includes a current collector body and a housing connection portion provided on the outer peripheral edge of the current collector body. The current collector body is fixedly connected to the negative electrode tab, the housing connection portion is fixedly connected to the side wall, the radius of the outer edge of the housing connection portion is greater than the radius of the electrode assembly, the axis of the second current collector member is the third axis, and the third axis is located within a cylindrical region with the second axis as the axis and a diameter d2 of φ0.2 mm.

[0021] In the above technical solution, since the second current collector member can play a certain limiting role on the electrode assembly after welding the housing connection portion and the housing, the third axis is limited to be within a cylindrical region with the second axis as the axis and a diameter d2 of φ0.2 mm. On the one hand, it can improve the coaxiality between the electrode assembly and the second current collector member, and further improve the coaxiality between the electrode assembly and the housing. On the other hand, it ensures a safe gap between the motor assembly and the side wall, reduces the problem of uneven stress on the electrode assembly caused by the housing due to the eccentricity of one side of the housing, and improves the problem of local poor liquid segregation and lithium precipitation, so as to achieve the effect of improving the safety performance.

[0022] The present utility model also provides a battery pack, which includes the secondary battery of any one of the above.

[0023] The present utility model also provides an electronic device, which includes the above battery pack.

[0024] For the secondary battery of the present utility model, the axis of the housing is the first axis, and the axis of the winding structure in the electrode assembly is the second axis. Considering that the results obtained by detecting in the state of the secondary battery during charging and expansion are inaccurate, it is limited that in the state where the SOC of the secondary battery is less than 5%, the second axis is located within a cylindrical region with the first axis as the axis and a diameter d1 of φ0.6 mm. This improves the coaxiality between the electrode assembly and the housing, makes the safety gap between the electrode assembly and the inner wall of the housing more uniform, alleviates the problem of uneven stress on the electrode assembly by the housing during the charge and discharge process of the battery, and improves the problem of local poor liquid segregation and lithium precipitation, so as to achieve the effect of improving the safety performance. Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other embodiments can be obtained based on these drawings.

[0026] Figure 1 Schematic diagram of the overall structure of an example of a secondary battery of the present invention;

[0027] Figure 2 Schematic diagram of the electrode assembly structure of an example of a secondary battery of the present invention;

[0028] Figure 3 Cross-sectional view of an example of a secondary battery of the present invention;

[0029] Figure 4 For Figure 1 Partial enlarged view at A in

[0030] Figure 5 For Figure 4 Partial enlarged view at B in

[0031] Figure 6 Schematic diagram of the overall structure of an example of a secondary battery of the present invention;

[0032] Figure 7 For Figure 6 Partial enlarged view at C in

[0033] Figure 8 For Figure 7 Partial enlarged view at D in

[0034] Figure 9 Schematic diagram of the overall structure of an example of a secondary battery of the present invention;

[0035] Figure 10 For Figure 9 Partial enlarged view at E in

[0036] Figure 11 For Figure 10 Partial enlarged view at F in

[0037] Figure 12 Cross-sectional view of an example of a secondary battery of the present invention;

[0038] Figure 13 Schematic diagram of an example of a battery pack of the present invention;

[0039] Figure 14 Schematic diagram of an example of an electronic device of the present invention.

[0040] Description of Component Labels

[0041] 1. Electronic device; 10. Battery pack; 11. Working part; 101. Box body; 102. Box cover; 100. Secondary battery; 110. Housing; 111. End wall; 112. Side wall; 113. Opening; 114. First axis; 120. Electrode assembly; 121. Positive electrode plate; 1211. Positive current collector; 1212. First coating area; 1213. First uncoated area; 122. Separator; 123. Negative electrode plate; 1231. Negative current collector; 1232. Second coating area; 1233. Second uncoated area; 124. Negative electrode tab; 125. Positive electrode tab; 126. Winding structure; 1261. Second axis; 127. Winding hole; 128. End sealing glue; 1281. Starting end; 1282. Terminal end; 1283. Overlapping part; 129. Coating layer; 1291. First coating part; 1292. Second coating part; 1293. Elastic layer; 1294. First adhesive layer; 1295. Base layer; 1296. Second adhesive layer; 130. Cover plate; 140. Terminal post; 150. First current collecting member; 160. Second current collecting member; 161. Current collecting body; 162. Housing connecting part; 163. Third axis; 170. Insulating plastic; 171. First insulator; 172. Second insulator; 173. Chamfer; 174. Third adhesive layer. Specific Embodiments

[0042] The following specific examples illustrate the embodiments of the present utility model. Those skilled in the art can easily understand other advantages and effects of the present utility model from the content disclosed in this specification. The present utility model can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present utility model. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. It should also be understood that the terms used in the embodiments of the present utility model are for the purpose of describing specific implementation manners and are not intended to limit the protection scope of the present utility model. The test methods without specific conditions noted in the following embodiments are usually in accordance with conventional conditions or the conditions recommended by each manufacturer.

[0043] When an embodiment gives a numerical range, it should be understood that unless otherwise specified in the present utility model, any value between the two endpoints of each numerical range and any value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present utility model, based on the understanding of those skilled in the art of the prior art and the description of the present utility model, can also use any methods, devices, and materials similar or equivalent to the methods, devices, and materials in the embodiments of the present utility model to implement the present utility model.

[0044] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of clear description, rather than to limit the scope of implementation of the present utility model. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope of implementation of the present utility model.

[0045] The secondary battery includes an electrode assembly, which is a component in the secondary battery where an electrochemical reaction occurs and can include one or more electrode assemblies.

[0046] The secondary battery further includes a housing, a cover plate and a terminal post. The housing includes an end wall and a side wall surrounding the end wall. One end of the side wall has an opening, and the electrode assembly can be assembled into the housing through the opening of the housing. The cover plate is used to cover the opening of the housing to achieve sealing. The terminal post passes through the end wall and is electrically connected to the electrode assembly to export the electrical energy generated by the electrode assembly.

[0047] The existing secondary batteries generally use a structure in which the electrode assembly is assembled with a steel housing. The external environment is isolated through the housing encapsulation to protect the electrochemical reaction of the internal active substances. At the same time, the side wall of the housing has a large restraining effect on the radial expansion of the electrode assembly. With the improvement of the battery performance requirements, the number of winding turns of the electrode sheet in the large cylindrical battery is usually greater than 40 turns. The increase in the number of turns leads to a corresponding increase in the accumulated expansion amount of the electrode assembly. In addition, secondary batteries mostly use silicon-based negative electrodes with higher energy storage capacity, but the silicon-based negative electrode will undergo more significant volume expansion during charge and discharge. The inventor found that when the electrode assembly is eccentric to one side of the housing, the influence of the uneven stress of the housing on the electrode assembly will be more obvious. One side of the eccentric housing is subjected to greater force, and the electrolyte between the electrode sheets is extruded in the later stage of the cycle, resulting in local liquid deficiency and lithium precipitation, and the performance of the cylindrical battery deteriorates sharply, posing a great potential safety hazard.

[0048] In view of this, the present utility model provides a technical solution, in which the second axis is defined within a cylindrical region with the first axis as the axis and a diameter d1 of φ0.6 mm. This setting improves the coaxiality of the electrode assembly and the housing, reduces the problem of uneven stress of the housing on the electrode assembly caused by the eccentricity of the electrode assembly to one side of the housing, and improves the problem of local liquid deficiency and lithium precipitation, so as to achieve the effect of improving the safety performance.

[0049] Please refer to Figures 1 to 14 , the present utility model provides a secondary battery 100, which includes: a housing 110, an electrode assembly 120, a terminal post 140 and a cover plate 130.

[0050] Please refer to Figure 1, the housing 110 includes an end wall 111 and a side wall 112 surrounding the end wall 111. As long as a stable sealing and electrical connection relationship can be formed, the connection between the end wall 111 and the side wall 112 can be achieved in various ways, such as integral stamping, integral casting, or separate welding. The surrounding of the side wall 112 is not limited. It can surround in a cylindrical or prismatic shape, or surround along any other closed-loop contour that can match the end wall 111. Define the axis of the housing 110 as the first axis 114. In this embodiment, the outer edge of the end wall 111 is circular, and the side wall 112 surrounds the outer edge of the end wall 111 in a cylindrical shape, and a circular opening 113 is formed at one end of the side wall 112 facing away from the end wall 111. An accommodation cavity is formed inside the housing 110 surrounded by the end wall 111 and the side wall 112 for accommodating the electrode assembly 120, electrolyte, and other necessary battery components. Specifically, the diameter of the housing 110 can be determined according to the specific size of the electrode assembly 120, such as 18mm, 21mm, 46mm, etc. The material of the housing 110 can be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. In order to prevent the housing 110 from rusting during long-term use, a layer of rust-proof material such as metallic nickel can also be plated on the surface of the housing 110.

[0051] Please refer to Figures 1 to 2 , the electrode assembly 120 is disposed inside the housing 110, and the electrode assembly 120 is a component that undergoes an electrochemical reaction in the secondary battery 100. One or more electrode assemblies 120 can be included in the housing 110. The electrode assembly 120 includes a positive electrode plate 121, a negative electrode plate 123, and a winding structure 126 formed by laminating and axially winding a separator 122 around the housing 110. A winding hole 127 is formed at the center of the winding structure 126, and the axis of the winding structure 126 is defined as the second axis 1261. It should be noted that the second axis 1261 of the winding structure 126 is determined as follows: First, perform a CT or cross-section on the secondary battery 100, then draw a line segment connecting the radial two ends of the electrode assembly 120 at positions near both ends of the electrode assembly 120, and then connect the midpoints of the two line segments. This connecting line is the second axis 1261. Please refer to Figure 1 .

[0052] Please refer to Figures 1 to 2 , the positive electrode plate 121 includes a positive electrode current collector 1211 and a positive electrode active material layer coated on the positive electrode current collector 1211. A first coating area 1212 coated with the positive electrode active material layer and a first uncoated area 1213 not coated with the positive electrode active material layer are formed on the positive electrode current collector 1211. The first coating area 1212 and the first uncoated area 1213 are arranged axially along the housing 110. The first uncoated area 1213 extends to the outside of the separator 122 at one end in the height direction of the secondary battery 100 and bends toward the second axis 1261 to form a stacked positive electrode tab 125.

[0053] Please refer to Figures 1 to 2 , the negative electrode tab 123 includes a negative electrode current collector 1231 and a negative electrode active material layer coated on the negative electrode current collector 1231. A second coated area 1232 coated with the negative electrode active material layer and a second uncoated area 1233 not coated with the negative electrode active material layer are formed on the negative electrode current collector 1231. The second coated area 1232 and the second uncoated area 1233 are arranged along the axial direction of the housing 110. The second uncoated area 1233 extends to the outside of the separator 122 at the other end in the height direction of the secondary battery 100 and bends toward the second axis 1261 to form a stacked negative electrode tab 124.

[0054] Please refer to Figures 1 to 2 , the separator 122 is disposed between the positive electrode tab 121 and the negative electrode tab 123 to isolate the positive electrode active material layer and the negative electrode active material layer. Taking the lithium-ion secondary battery 100 as an example, the material of the positive electrode current collector 1211 can be aluminum, and the positive electrode active material layer includes a positive electrode active material, which can be lithium cobaltate, lithium iron phosphate, ternary lithium, lithium manganate, etc. The material of the negative electrode current collector 1231 can be copper, and the negative electrode active material layer includes a negative electrode active material, which can be carbon or silicon, etc. The base material of the separator 122 can be polypropylene (PP for short) or polyethylene (PE for short), etc. To protect and insulate the battery cell, an insulating film can also be coated on the outside of the battery cell. The insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET for short), polyvinyl chloride (PVC for short), or other polymer materials.

[0055] Please refer to Figure 1 and Figure 2 , further, in the present utility model, the positive electrode tab 125 faces the end wall 111 or the opening 113, then the negative electrode tab 124 faces the other end of the housing 110. In this embodiment, the positive electrode tab 125 faces the end wall 111 and is electrically connected to the terminal 140 to make the terminal 140 positively charged. The negative electrode tab 124 faces the opening 113, and the housing 110 is electrically connected to the negative electrode tab 124, so as to be negatively charged. However, in other embodiments, the negative electrode tab 124 can also be connected to the terminal 140, and the positive electrode tab 125 can be connected to the housing 110.

[0056] Please refer to Figure 1, the cover plate 130 is hermetically installed on the opening 113; the outer edge shape of the cover plate 130 corresponds to the shape of the opening 113 and is connected to the side wall 112 to seal the opening 113. In a specific embodiment, a rolling groove recessed towards the inside of the housing 110 is rolled out in the area near the outer end on the side wall 112 of the housing 110. The rolling groove can limit the axial displacement of the electrode assembly 120. One side of the rolling groove forms an annular step around the housing 110. The cover plate 130 is placed on this step. A sealing ring is provided between the cover plate 130 and the side wall 112. The edge of the opening 113 is sealed by caulking so that the cover plate 130 presses the sealing ring to form a reliable connection.

[0057] Considering that the number of winding turns of the negative electrode tab 123 in the secondary battery 100 in the present application is usually greater than 40 turns, the increase in the number of turns leads to a corresponding increase in the accumulated expansion amount of the electrode assembly 120. In addition, in some embodiments, the secondary battery 100 uses a silicon-based negative electrode with higher energy storage capacity. The silicon-based negative electrode will undergo more significant volume expansion during charge and discharge. When the electrode assembly 120 is eccentric to one side of the housing 110, the influence of the uneven stress of the housing 110 on the electrode assembly 120 will be more obvious. Further, please refer to Figure 3 , in the state where the secondary battery 100 is less than 5% SOC, the second axis 1261 is located within a cylindrical region with the first axis 114 as the axis and a diameter d1 of φ0.6 mm. It is defined that the second axis 1261 is located within a cylindrical region with the first axis 114 as the axis and a diameter d1 of φ0.6 mm. This setting improves the coaxiality of the electrode assembly 120 and the housing 110, reduces the problem of uneven stress of the housing 110 on the electrode assembly 120 caused by the electrode assembly 120 being eccentric to one side of the housing 110, and improves the problem of local poor liquid lithium precipitation, so as to achieve the effect of improving safety performance. It should be noted that since the position of the second axis 1261 and the position of the first axis 114 in this technical solution are both determined when the electrode assembly 120 is not expanded, in order to avoid inaccurate results that may be obtained when detecting in the charging and expanding state of the secondary battery 100, it is defined in the state where the secondary battery 100 is less than 5% SOC, that is, when the power of the secondary battery 100 is lower than 5%. In addition, the number of winding turns of the negative electrode tab 123 is determined by taking a CT or screenshot of the electrode assembly 120 and then observing the number of turns of the negative electrode tab 123.

[0058] Please refer to Figure 3, in an example of the secondary battery 100 of the present utility model, the electrode assembly 120 further includes a tail glue 128 that winds more than one turn around the outer circumference of the winding structure 126. The height of the tail glue 128 along the axial direction of the electrode assembly 120 is not limited. It can be the height that completely covers the winding structure 126, or it can partially cover it. The tail glue 128 can be a single segment or multiple segments, and the multiple segments of tail glue 128 are arranged at intervals along the axial direction of the electrode assembly 120. Further, along the winding direction of the winding structure 126, the terminal 1282 of the tail glue 128 bypasses the starting end 1281 of the tail glue 128 and forms an overlapping portion 1283. This setting can make the starting end 1281 of the tail glue 128 be pressed by the terminal 1282 to improve the fixing effect of the tail glue 128. However, the overlapping portion 1283 will increase the local radial thickness of the winding structure 126. Therefore, in order to alleviate the influence of the overlapping portion 1283 on the coaxiality of the electrode assembly 120 and the housing 110, the distance between the overlapping portion 1283 and the side wall 112 is greater than or equal to 0.2 mm. For example, it can be 0.2 mm, 0.22 mm, 0.25 mm, 0.27 mm, 0.28 mm, 0.3 mm, 0.32 mm, or 0.35 mm, etc., so as to achieve a safe gap between the overlapping portion 1283 and the side wall 112 and alleviate the problem that when the battery expands during charging, the overlapping portion 1283 is likely to be squeezed with the side wall 112, resulting in the extrusion of the electrolyte and the occurrence of local lithium plating.

[0059] Please refer to Figure 4 , in an example of the secondary battery 100 of the present utility model, the secondary battery 100 further includes a pole column 140. Specifically, the pole column 140 penetrates the end wall 111 and is insulated from the end wall 111. One end of the pole column 140 facing the electrode assembly 120 passes through the end wall 111 and is directly electrically connected to the positive electrode tab 125 or is electrically connected through an indirect transfer. The structural form of the pole column 140 can be any suitable form that can pass through the end wall 111 and be electrically connected to the positive electrode tab 125 of the electrode assembly 120. For example, the cross-section can be circular, square, prismatic, or a special-shaped profile that can achieve stable electrical conduction. The hole of the pole column 140 corresponds to the shape of the pole column 140. In this embodiment, the cross-section of the pole column 140 is circular.

[0060] Further, please refer to Figure 4 and Figure 5, in this embodiment, the secondary battery 100 further includes a first current collector member 150. One side of the first current collector member 150 is fixedly connected to the terminal 140, and the other side of the first current collector member 150 is fixedly connected to the positive electrode tab 125. There are various ways to connect the first current collector member 150 and the positive electrode tab 125. For example, it can be a welding connection or a conductive adhesive bonding connection. As long as the electrical connection between the first current collector member 150 and the positive electrode tab 125 can be achieved and the current conduction requirement is satisfied. In this embodiment, the welding connection method is adopted, and the first current collector member 150 and the terminal 140 are also connected by welding.

[0061] Further, in order to insulate and isolate the exposed tab near the outer side of the winding structure 126 from the housing 110, a rubber coating layer 129 is provided at the edge of the first current collector member 150 and one end of the electrode assembly 120 close to the first current collector member 150. Please refer to Figure 1 and Figures 4 to 8 , the rubber coating layer 129 at least isolates the positive electrode tab 125 and the housing 110. The rubber coating layer 129 includes a first covering portion 1291 and a second covering portion 1292 connected to the first covering portion 1291. The first covering portion 1291 and the second covering portion 1292 can be integrally provided or separately provided, and there is no limitation in this regard. As long as the first covering portion 1291 covers the edge of the first current collector member 150 and the second covering portion 1292 covers the outer periphery of one end of the electrode assembly 120 close to the first current collector member 150. The setting of the rubber coating layer 129 can, on the one hand, isolate the positive electrode tab 125 and the housing 110, and on the other hand, can wrap the exposed positive electrode tab 125 to protect the positive electrode tab 125 and reduce the risk of the positive electrode tab 125 breaking and falling into the battery interior to cause a short circuit.

[0062] Please continue to refer to Figure 1 and Figures 4 to 8, further, the second covering portion 1292 includes a compressible elastic layer 1293. On the one hand, the second covering portion 1292 with a certain thickness can play a pre-guiding role when the electrode assembly 120 is placed into the housing 110, so that there is at least a gap equal to the thickness of the second covering portion 1292 between the electrode assembly 120 and the side wall 112, improving the coaxiality of the electrode assembly 120 and the housing 110, reducing the problem of uneven stress on the electrode assembly 120 caused by the electrode assembly 120 being eccentric to one side of the housing 110, improving the problem of local lean electrolyte lithium deposition, and achieving the effect of improving the safety performance. In addition, the second covering portion 1292 has compressible performance, which can reduce the thickness when the battery expands and reduce the effect of stress concentration. Preferably, the range of the thickness b of the second covering portion 1292 is: b≤0.2mm. For example, it can be 0.1mm, 0.12mm, 0.14mm, 0.15mm, 0.16mm, 0.18mm or 0.2mm, etc. The second covering portion 1292 with a thickness within this range can not only realize the pre-guiding of the electrode assembly 120 but also does not affect the insertion of the electrode assembly 120 into the housing.

[0063] In an example of the secondary battery 100 of the present invention, please refer to Figure 1 and Figures 4 to 5 , the first covering portion 1291 also includes an elastic layer 1293 and is integrally formed with the second covering portion 1292. This setting can realize the integrated blanking and packaging of the first covering portion 1291 and the second covering portion 1292, simplify the process of packaging the encapsulation layer 129, and improve the processing efficiency. The encapsulation layer 129 further includes a first adhesive layer 1294 for adhesively fixing the elastic layer 1293 to the electrode assembly 120 and the first current collector member 150. It should be noted that the material of the elastic layer 1293 can be any elastic and insulating material, which is not limited herein. For example, polyethylene foam, ethylene-vinyl acetate copolymer foam, polyurethane foam or polypropylene foam, etc. The first adhesive layer 1294 can be any material that can adhesively fix the elastic layer 1293 to the electrode assembly 120 and the first current collector member 150, which is also not limited herein. For example, it can be: silicone adhesive, polyurethane adhesive, epoxy resin adhesive, acrylic adhesive or synthetic rubber adhesive, etc.

[0064] In another example of the secondary battery 100 of the present invention, please refer to Figures 6 to 8, the second covering portion 1292 includes a base layer 1295 integrally formed with the first covering portion 1291, an elastic layer 1293, and a second adhesive layer 1296 that bonds the base layer 1295 and the elastic layer 1293. That is, both the first covering portion 1291 and the second covering portion 1292 include a base layer 1295. In this embodiment, the base layer 1295 is integrally formed, or it can be separately provided. Only the base layer 1295 covers the edge of the first current collector member 150. This setting can increase the capacity of the secondary battery 100 in the height direction; only the elastic layer 1293 is provided in the second covering portion 1292. This setting can improve the coaxiality of the electrode assembly 120 and the housing 110 while having a relatively low material cost. It should be noted that the material of the base layer 1295 can be polyimide tape, polytetrafluoroethylene tape, epoxy film tape, etc., and the material of the elastic layer 1293 can be any elastic and insulating material, which is not limited herein. For example, polyethylene foam, ethylene-vinyl acetate copolymer foam, polyurethane foam, or polypropylene foam, etc. The first adhesive layer 1294 can be any material that can bond and fix the elastic layer 1293 to the electrode assembly 120, which is also not limited herein. For example, it can be: silicone adhesive, polyurethane adhesive, epoxy resin adhesive, acrylic adhesive, or synthetic rubber adhesive, etc.

[0065] Please refer to Figures 9 to 11, in an example of the secondary battery 100 of the present utility model, the secondary battery 100 further includes an insulating plastic 170 that at least isolates the positive electrode tab 125 and the housing 110. The insulating plastic 170 can isolate and insulate the positive electrode tab 125 and the housing 110. The material of the insulating plastic 170 is not limited and can be any one of soluble polytetrafluoroethylene (Perfluoroalkoxy, abbreviated as PFA), polybutylene terephthalate (Polybutylene Terephthalate, abbreviated as PBT), and liquid crystal polymer (Liquid Crystal Polymer, abbreviated as LCP) PP, polyphenylene sulfide (Polyphenylene Sulfide, abbreviated as PPS), and polycarbonate (Polycarbonate, abbreviated as PC). The insulating plastic 170 includes a first insulator 171 and a second insulator 172. The first insulator 171 is located between the positive electrode tab 125 and the end wall 111. In this embodiment, the positive electrode tab 125 is electrically connected to the terminal 140 through a first current collecting member 150. Therefore, further, the first insulator 171 is located between the first current collecting member 150 and the end wall 111, and is used to isolate the first current collecting member 150 and the end wall 111. The second insulator 172 is located between the side wall 112 and the electrode assembly 120, and is used to isolate the exposed positive electrode tab 125 and the side wall 112. At the same time, the second insulator 172 can also play a role in limiting the position between the electrode assembly 120 and the side wall 112, so that there is at least a gap with the thickness of the second insulator 172 between the electrode assembly 120 and the side wall 112, which can improve the coaxiality of the electrode assembly 120 and the housing 110, reduce the problem of uneven stress on the electrode assembly 120 caused by the electrode assembly 120 being eccentric to one side of the housing 110, and improve the problem of local lean electrolyte lithium deposition, so as to achieve the effect of improving the safety performance.

[0066] Please refer to Figure 10 and Figure 11 , in an example of the secondary battery 100 of the present utility model, a chamfer 173 is provided on the inner wall of the end of the second insulator 172 away from the first insulator 171. That is, the chamfer 173 is provided on the side where the electrode assembly 120 is inserted into the housing 110. This setting can play a pre-guiding role when the electrode assembly 120 is placed into the housing 110, improve the assembly efficiency, and can also reduce the contact area between the electrode assembly 120 and the second insulator 172, which is beneficial to heat dissipation.

[0067] Considering that the chamfer 173 of the second insulator 172 is relatively thin and is easily bent towards the inside of the housing 110, thereby interfering with the insertion of the electrode assembly 120 into the housing and affecting the assembly quality. In an example of the secondary battery 100 of the present utility model, please refer to Figure 10 and Figure 11, a third adhesive layer 174 for bonding and fixing the second insulator 172 and the side wall 112 is provided on the outer side of the second insulator 172. This setting prevents the second insulator 172 from interfering when the electrode assembly 120 is inserted into the housing 110, and at the same time avoids the existence of a gap between the second insulator 172 and the side wall 112, which is more conducive to the insertion of the electrode assembly 120 into the housing, and can achieve the effect of improving the assembly efficiency and assembly quality.

[0068] Please refer to Figure 12 , in an example of the secondary battery 100 of the present invention, the secondary battery 100 further includes a second current collector member 160. The second current collector member 160 includes a current collector body 161 and a housing connection portion 162 provided on the outer peripheral edge of the current collector body 161. The current collector body 161 is fixedly connected to the negative electrode tab 124, and the housing connection portion 162 is fixedly connected to the side wall 112. The housing connection portion 162 can be an integral annular structure or one or more fan-shaped annular structures, as long as the current conduction requirement and welding strength requirement between the second current collector member 160 and the housing 110 are satisfied. The radius of the outer edge of the housing connection portion 162 is greater than the radius of the electrode assembly 120. The axis of the second current collector member 160 is the third axis 163. Since after the housing connection portion 162 and the housing 110 are welded, the second current collector member 160 can play a certain limiting role on the electrode assembly 120, the third axis 163 is located within a cylindrical region with the second axis 1261 as the axis and a diameter d2 of φ0.2 mm. This setting can, on the one hand, improve the coaxiality of the electrode assembly 120 and the second current collector member 160, and then improve the coaxiality of the electrode assembly 120 and the housing 110. On the other hand, it ensures that there is a safe gap between the motor assembly and the side wall 112, reduces the problem of uneven stress on the electrode assembly 120 caused by the electrode assembly 120 being eccentric to one side of the housing 110, and improves the problem of local poor liquid and lithium precipitation, so as to achieve the effect of improving safety performance.

[0069] Please refer to Figure 13 , the present invention also provides a battery pack 10. The battery pack 10 includes the secondary battery 100 of any one of the above. In an embodiment of the battery pack 10 of the present invention, the battery pack 10 includes 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 in parallel with each other, or in a mixed connection of series and parallel. The box cover 102 covers the box body 101 to protect the plurality of secondary batteries 100. It should be noted that the battery pack 10 may 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 invention. The battery pack 10 can be a battery module or a battery pack, an energy storage electric cabinet, etc.; details are not described herein one by one.

[0070] Please refer to Figure 14, the present utility model further provides an electronic device 1, and the electronic device 1 includes the above-mentioned battery pack 10. The working part 11 is electrically connected to the battery pack 10 to obtain power support. As an example, the electronic device 1 is a vehicle, and the vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc., but is not limited thereto. The working part 11 is the vehicle body, and the battery pack 10 is arranged at the bottom of the vehicle body and provides power support for the running of the vehicle or the operation of the electrical components in the vehicle. However, in some other embodiments, the electronic device 1 can also be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spaceship, etc.; the working part 11 can be a unit component that can obtain the electric energy of the battery pack 10 and perform corresponding work, such as the fan blade rotation unit of a fan, the dust suction working unit of a vacuum cleaner, etc. The electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle 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 assembly electric tool and a railway electric tool, for example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact electric drill, a concrete vibrator and a planer, etc. The embodiments of the present application do not impose special restrictions on the above-mentioned electronic device 1.

[0071] For the secondary battery of the present utility model, the axis of the housing is the first axis, and the axis of the winding hole in the electrode assembly is the second axis. In the state where the SOC of the secondary battery is less than 5%, it is defined that the second axis is located in a cylindrical region with the first axis as the axis and a diameter d1 of φ0.6 mm. This setting improves the coaxiality of the electrode assembly and the housing, reduces the problem of uneven stress on the electrode assembly caused by the eccentricity of the housing on one side of the electrode assembly, and improves the problem of local poor liquid and lithium precipitation, so as to achieve the effect of improving the safety performance. Therefore, the present utility model effectively overcomes some practical problems in the prior art and thus has high utilization value and practical significance. The above embodiments are only illustrative of the principles and effects of the present utility model and are not used to limit the present utility model. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present utility model. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present utility model should still be covered by the claims of the present utility model.

Claims

1. A secondary battery, characterized in that, Comprising: A housing, including an end wall and a side wall surrounding the end wall, the axis of the housing being the first axis; An electrode assembly, accommodated in the housing, the electrode assembly including a winding structure formed by laminating and winding a positive electrode tab, a negative electrode tab, and a separator, wherein the number of winding turns of the negative electrode tab is greater than 40 turns, and the axis of the winding structure is the second axis; Wherein, in a state where the state of charge (SOC) of the secondary battery is less than 5%, the second axis is located within a cylindrical region with the first axis as the axis and a diameter d1 of φ0.6 mm.

2. The secondary battery according to claim 1, characterized in that, The electrode assembly further includes a finishing adhesive that winds more than one turn around the outer periphery of the winding structure. Along the winding direction of the winding structure, the terminal of the finishing adhesive bypasses the starting end of the finishing adhesive and forms a overlapping portion, and the distance between the overlapping portion and the side wall is greater than or equal to 0.2 mm.

3. The secondary battery according to claim 1, wherein The secondary battery further includes a terminal, a first current collector member, and a rubber coating layer. The terminal penetrates the end wall and is insulated from the end wall. The end of the positive electrode tab includes a positive electrode ear bent toward the second axis. One side of the first current collector member is fixedly connected to the terminal, and the other side of the first current collector member is fixedly connected to the positive electrode ear. The rubber coating layer at least isolates the positive electrode ear and the housing. The rubber coating layer includes a first coating portion and a second coating portion connected to the first coating portion. The first coating portion covers the edge of the first current collector member, and the second coating portion covers the outer periphery of one end of the electrode assembly close to the first current collector member. The second coating portion includes a compressible elastic layer, and the thickness b of the second coating portion ranges from: b ≤ 0.2 mm.

4. The secondary battery according to claim 3, characterized in that, The first coating portion also includes the elastic layer and is integrally formed with the second coating portion. The rubber coating layer further includes a first adhesive layer that adhesively fixes the elastic layer to the electrode assembly and the first current collector member.

5. The secondary battery according to claim 3, characterized in that, The second coating portion includes a base layer integrally formed with the first coating portion, the elastic layer, and a second adhesive layer that bonds the base layer and the elastic layer.

6. The secondary battery according to claim 1, characterized in that, The end of the positive electrode tab includes a positive electrode ear that extends out of the separator in the direction of the end wall along the second axis and is bent toward the second axis. The secondary battery further includes an insulating plastic that at least isolates the positive electrode ear and the housing. The insulating plastic includes a first insulator and a second insulator. The first insulator is located between the positive electrode ear and the end wall, and the second insulator is located between the side wall and the electrode assembly.

7. The secondary battery according to claim 6, characterized in that, The inner wall of one end of the second insulator away from the first insulator is provided with a chamfer.

8. The secondary battery according to claim 7, wherein The outer side of the second insulator is provided with a third adhesive layer that adhesively fixes the second insulator and the side wall.

9. The secondary battery according to claim 1, characterized in that, The end portion of the negative electrode plate includes a negative electrode tab that extends out of the separator in a direction away from the end wall along the second axis and is bent toward the second axis. The secondary battery further includes a second current collector member, which includes a current collector body and a housing connection portion provided on the outer peripheral edge of the current collector body. The current collector body is fixedly connected to the negative electrode tab, the housing connection portion is fixedly connected to the side wall, the radius of the outer edge of the housing connection portion is greater than the radius of the electrode assembly, the axis of the second current collector member is the third axis, and the third axis is located within a cylindrical region with the second axis as the axis and a diameter d2 of φ0.2 mm.

10. A battery pack, characterized in that, A secondary battery including any one of claims 1 to 9.

11. An electronic device, characterized in that, A battery pack including claim 10.

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