Rechargeable batteries, battery packs, and electronic devices

Abstract

To provide a secondary battery, battery pack, and electronic device that improve the technical problem of battery performance degradation caused by lithium deposition due to localized electrolyte deficiency in the electrode assembly. [Solution] The secondary battery includes an outer shell and an electrode assembly. The outer shell includes end walls and side walls surrounding the end walls, and the axis of the outer shell is the first axis. The electrode assembly is housed within the outer shell and includes a wound structure in which a positive electrode plate, a negative electrode plate, and a separator are stacked and wound. Here, the number of turns of the negative electrode plate exceeds 40, and the axis of the wound structure is the second axis. When the SOC of the secondary battery 100 is less than 5%, the second axis is aligned with the first axis and is located within a cylindrical region with a diameter d1 of 0.6 mm, thereby improving the technical problem of degradation of battery performance caused by eccentricity of the electrode assembly to one side of the outer shell.

Description

Technical Field

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

Background Art

[0002] Conventional large-diameter cylindrical batteries generally use a structure that combines an electrode assembly and a steel outer shell. The outer shell seals to block the external environment and plays a role in protecting the electrochemical reaction of the internal active material. At the same time, the side wall of the outer shell has a large restraining force against the radial expansion of the electrode assembly. In large-diameter cylindrical batteries, the number of turns of the electrode plate increases, and the radial expansion amount of the electrode assembly also increases. Through inspection, in the same lot of large-diameter cylindrical batteries, there are some cases where the electrolyte is extruded between the electrode plates in the later stage of the cycle. As a result, local electrolyte shortage and lithium precipitation occur, and it has been confirmed that the performance of the cylindrical battery deteriorates rapidly, posing a significant safety risk.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In view of the above drawbacks of the prior art, the present invention provides a secondary battery, a battery pack, and an electronic device for improving the technical problem that the battery performance deteriorates due to lithium precipitation caused by local electrolyte shortage in the electrode assembly.

Means for Solving the Problems

[0004] To achieve the above and other related objectives, the present invention provides a secondary battery, a battery pack, and an electronic device. The secondary battery includes a shell and an electrode assembly. The shell includes end walls and side walls surrounding the end walls, and the axis of the shell is the first axis. The electrode assembly is housed within the shell and includes a wound structure in which a positive electrode plate, a negative electrode plate, and a separator are stacked and wound. Here, the number of turns of the negative electrode plate exceeds 40, and the axis of the wound structure is the second axis. When the state of charge (SOC) of the secondary battery is less than 5%, the second axis is centered on the first axis and is located within a cylindrical region with a diameter d1 of 0.6 mm.

[0005] In the above proposed technology, considering that the number of turns of the electrode plates in a large-diameter cylindrical battery usually exceeds 40, the cumulative expansion of the electrode assembly increases with the increase in the number of turns. If the electrode assembly is eccentric to one side of the outer shell, the non-uniformity of the stress on the electrode assembly due to the outer shell becomes more pronounced. When the state of charge (SOC) of the secondary battery is less than 5%, the second axis is limited to the first axis and the diameter d1 is located within a cylindrical region with a diameter of 0.6 mm. This improves the coaxiality between the electrode assembly and the outer shell, ensures a uniform safety gap between the electrode assembly and the inner wall of the outer shell, mitigates the problem of non-uniform stress applied by the outer shell to the electrode assembly during the battery's charging and discharging process, improves the problem of lithium deposition due to localized electrolyte deficiency, and enhances safety performance.

[0006] In an example of the secondary battery of the present invention, the electrode assembly further includes a finishing adhesive that wraps around the outer circumference of the winding structure one or more times, wherein the end of the finishing adhesive extends beyond the beginning of the finishing adhesive along the winding direction of the winding structure, forming an overlap, and the distance between the overlap and the side wall is 0.2 mm or more.

[0007] In the above technical solution, in order to properly fix the winding structure, a finishing adhesive is wrapped around the outer circumference of the winding structure. The end of the finishing adhesive extends beyond the beginning of the finishing adhesive, forming an overlap. Since the radial dimension of the overlap is larger, the distance between the overlap and the side wall is limited to 0.2 mm or more to ensure a safe gap between the overlap and the side wall. This prevents the electrolyte from being pushed out due to the overlap being compressed against the side wall during battery charging expansion, thereby improving the problem of localized lithium deposition.

[0008] In an example of the secondary battery of the present invention, the secondary battery further includes a terminal, a first current collector, and a coating layer, wherein the terminal penetrates an end wall and is insulated from the end wall, the end of the positive electrode plate includes a positive electrode tab bent toward a second axis, one side of the first current collector is fixedly connected to the terminal, the other side of the first current collector is fixedly connected to the positive electrode tab, the coating layer insulates at least the positive electrode tab from the outer shell, the 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, the second coating portion covers the outer circumference of the end of the electrode assembly near the first current collector, the second coating portion includes a compressible elastic layer, and the thickness b of the second coating portion is in the range of b ≤ 0.2 mm.

[0009] In the above technical solution, a covering layer is provided on the edge of the first current collector and on one end of the electrode assembly near the first current collector to insulate the exposed positive electrode tab near the outside of the winding structure from the outer shell. The covering layer can insulate the positive electrode tab from the outer shell on the one hand, and can also enclose the exposed positive electrode tab on the other hand, protecting the positive electrode tab and reducing the risk of the positive electrode tab breaking and falling into the battery and causing a short circuit. Furthermore, the second covering portion includes a compressible elastic layer, and the thickness b of the second covering portion is in the range of b ≤ 0.2 mm. The second covering portion of a certain thickness acts as a preliminary guide when inserting the electrode assembly into the outer shell, and a gap of at least the thickness of the second covering portion exists between the electrode assembly and the side wall, improving the coaxiality of the electrode assembly and the outer shell, reducing the problem of uneven stress on the electrode assembly in the outer shell due to the electrode assembly being eccentric to one side of the outer shell, improving the problem of lithium deposition due to localized electrolyte deficiency, and improving safety performance. In addition, because the second covering portion has the characteristic of being compressible, its thickness decreases when the battery expands, which also reduces stress concentration.

[0010] In an example of the secondary battery of the present invention, the first covering portion also includes an elastic layer and is integrally molded with the second covering portion, and the covering layer further includes a first adhesive layer that adheres and fixes the elastic layer to the electrode assembly and the first current collector.

[0011] In the above-described technical solution, since the first and second coating portions are integrally molded, the packaging process for the coating layer can be simplified and processing efficiency can be improved.

[0012] In an example of the secondary battery of the present invention, the second coating portion includes a base layer, an elastic layer, and a second adhesive layer that bond the base layer and the elastic layer, all integrally molded with the first coating portion.

[0013] In the above technical solution, by providing an elastic layer only in the second coating portion, it is possible to improve the coaxiality between the electrode assembly and the outer shell while reducing material costs.

[0014] In an example of the secondary battery of the present invention, the end of the positive electrode plate protrudes beyond the separator in the direction of the end wall along a second axis and includes a positive electrode tab that is bent toward the second axis, and the secondary battery further includes an insulating plastic that insulates at least the positive electrode tab from the outer shell, the insulating plastic including a first insulator and a second insulator, the first insulator located between the positive electrode tab and the end wall and the second insulator located between the side wall and the electrode assembly.

[0015] In the above technical solution, the insulating plastic plays the role of insulating the positive electrode tab from the outer shell. The first insulator mainly insulates the positive electrode tab from the end wall, and the second insulator mainly insulates the exposed positive electrode tab from the side wall. At the same time, the second insulator plays a positioning role between the electrode assembly and the side wall. A gap of at least the thickness of the second insulator exists between the electrode assembly and the side wall, thereby improving the coaxiality of the electrode assembly from the outer shell. This reduces the problem of uneven stress on the electrode assembly from the outer shell due to the electrode assembly being eccentric to one side of the outer shell, improves the problem of lithium deposition due to localized electrolyte deficiency, and enhances safety performance.

[0016] In an example of the secondary battery of the present invention, a chamfer is provided on the inner wall of one end of the second insulator that is farther from the first insulator.

[0017] In the above technical solution, the chamfering acts as a preliminary guide when inserting the electrode assembly into the outer shell, improving assembly efficiency, reducing the contact area between the electrode assembly and the second insulator, and promoting heat dissipation.

[0018] In an example of the secondary battery of the present invention, a third adhesive layer is provided on the outside of the second insulator to bond and fix the second insulator to the side wall.

[0019] In the above technical solution, the third adhesive layer is used to bond and fix the second insulator and the side wall, preventing gaps from forming between the second insulator and the side wall, and preventing interference by the second insulator when inserting the electrode assembly into the outer shell. This configuration facilitates the insertion of the electrode assembly into the outer shell, resulting in improved assembly efficiency and assembly quality.

[0020] In an example of the secondary battery of the present invention, the end of the negative electrode plate protrudes beyond the separator in a direction away from the end wall along the second axis and includes a negative electrode tab bent toward the second axis, the secondary battery further includes a second current collector, the second current collector includes a current collector body and an outer shell connection portion provided on the outer periphery of the current collector body, the current collector body is fixedly connected to the negative electrode tab and the outer shell connection portion is fixedly connected to the side wall, the radius of the outer edge of the outer shell connection portion is greater than the radius of the electrode assembly, the axis of the second current collector is the third axis, the third axis is centered on the second axis and is located within a cylindrical region with a diameter d2 of 0.2 mm.

[0021] In the above technical solution, after welding the outer shell connection to the outer shell, the second current collector performs a certain positioning action relative to the electrode assembly. By limiting the third axis to be located within a cylindrical region with a diameter d2 of 0.2 mm, with the second axis as the axis, the coaxiality between the electrode assembly and the second current collector is improved, as is the coaxiality between the electrode assembly and the outer shell. Furthermore, a safe gap is secured between the electrode assembly and the side wall, reducing the problem of uneven stress on the electrode assembly in the outer shell caused by the electrode assembly being eccentric to one side of the outer shell, improving the problem of lithium deposition due to localized electrolyte deficiency, and thus improving safety performance.

[0022] The present invention further provides a battery pack including any of the above-mentioned secondary batteries.

[0023] The present invention further provides an electronic device including the above-mentioned battery pack. [Effects of the Invention]

[0024] In the secondary battery of the present invention, taking the axis of the outer shell as the first axis and the axis of the winding structure of the electrode assembly as the second axis, in consideration of the fact that the test results obtained in the charged and expanded state of the secondary battery are inaccurate, when the SOC of the secondary battery is less than 5%, by limiting that the second axis is centered on the first axis and is located within a cylindrical region with a diameter d1 of 0.6 mm, the coaxiality of the electrode assembly and the outer shell is improved, a uniform safety gap is provided between the electrode assembly and the inner wall of the outer shell, the problem of non-uniform stress of the outer shell on the electrode assembly during the charge and discharge process of the battery is alleviated, the problem of lithium precipitation due to local electrolyte deficiency is improved, and the effect of improving the safety performance is obtained.

Brief Description of the Drawings

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings necessary for the description of the embodiments or the prior art are briefly introduced below. The following drawings are only some embodiments of the present invention, and it is obvious that those skilled in the art can obtain other embodiments based on these drawings without creative labor.

[0026] [Figure 1] It is a schematic diagram showing the overall structure of an example of the secondary battery of the present invention. [Figure 2] It is a schematic diagram showing the structure of the electrode assembly of an example of the secondary battery of the present invention. [Figure 3] It is a cross-sectional view of an example of the secondary battery of the present invention. [Figure 4] It is a cross-sectional view of an example of the secondary battery of the present invention. [Figure 5] It is a partial enlarged view of the location A in FIG. 1. [Figure 6] It is a partial enlarged view of the location B in FIG. 5. [Figure 7] It is a schematic diagram showing the overall structure of an example of the secondary battery of the present invention. [Figure 8] It is a partial enlarged view of the location C in FIG. 7. [Figure 9] It is a partial enlarged view of the location D in FIG. 8. [Figure 10] It is a schematic diagram showing the overall structure of an example of the secondary battery of the present invention. [Figure 11] This is a magnified view of area E in Figure 10. [Figure 12] This is a magnified view of section F in Figure 11. [Figure 13] This is a cross-sectional view of an example of a secondary battery of the present invention. [Figure 14] This is a schematic diagram showing an example of the battery pack of the present invention. [Figure 15] This is a schematic diagram showing an example of the electronic device of the present invention. [Modes for carrying out the invention]

[0027] The embodiments of the present invention will be described below through specific examples, but those skilled in the art will readily understand other advantages and effects of the present invention from the disclosures herein. The present invention can be carried out or applied by different specific embodiments, and each detail herein can be modified or changed in various ways without departing from the spirit of the invention, based on different viewpoints and applications. The following embodiments and features of embodiments are combinable, provided they do not contradict each other. Furthermore, the terms used in the embodiments of the present invention are for describing specific embodiments and do not limit the scope of protection of the present invention. Test methods in the following embodiments that do not specifically mention conditions generally follow conventional conditions or conditions recommended by each manufacturer.

[0028] Where numerical ranges are indicated in the examples, any number at both ends of each range and any number between those ends is selectable, unless otherwise specified in the present invention. Unless otherwise defined, all technical and scientific terms used in the present invention have the meanings that a person skilled in the art would understand from the prior art and the description of the present invention, and the present invention can also be realized using any prior art method, apparatus, or material equivalent to or similar to the methods, apparatus, or materials of the examples of the present invention.

[0029] Furthermore, terms such as "up," "down," "left," "right," "middle," and "one" used herein are for the purpose of clarifying the description and do not limit the scope of the invention. Changes or adjustments to these relative relationships, even if they do not result in a substantial change to the technical content, are considered to fall within the scope of the invention.

[0030] A secondary battery includes an electrode assembly, which is a component in which an electrochemical reaction occurs within the secondary battery, and may include one or more electrode assemblies.

[0031] The secondary battery further includes an outer shell, a cover plate, and terminals, the outer shell including end walls and side walls surrounding the end walls, with an opening at one end of the side walls, the electrode assembly being assembled inside the outer shell through the opening in the outer shell, the cover plate closing and sealing the opening in the outer shell, and the terminals passing through the end walls and electrically connecting to the electrode assembly to derive the power generated by the electrode assembly to the outside.

[0032] Conventional rechargeable batteries are generally constructed by combining an electrode assembly with a steel outer shell. The outer shell seals the battery from the external environment and protects the electrochemical reactions of the internal active material. At the same time, the side walls of the outer shell exert a strong restraining force against the radial expansion of the electrode assembly. As battery performance improves, the number of turns of the electrode plates in large-diameter cylindrical batteries usually exceeds 40. This increase in the number of turns relatively increases the cumulative expansion of the electrode assembly. Rechargeable batteries often employ silicon-based negative electrodes, which have higher energy storage capacity. However, silicon-based negative electrodes exhibit more significant volume expansion during the charge and discharge process. The inventors discovered that when the electrode assembly is eccentric to one side of the outer shell, the non-uniformity of the stress on the electrode assembly by the outer shell becomes more pronounced, resulting in greater stress on the eccentric side. In the later stages of the cycle, the electrolyte is pushed out between the electrode plates, causing localized electrolyte shortages and lithium deposition, leading to a rapid deterioration of the cylindrical battery's performance and creating a serious safety risk.

[0033] In view of this, the present invention provides a technical solution that limits the second axis to being centered on the first axis and having a diameter d1 within a cylindrical region with a diameter of 0.6 mm. This configuration improves the coaxiality of the electrode assembly and the outer shell, reduces the problem of uneven stress on the electrode assembly of the outer shell due to the eccentricity of the electrode assembly to one side of the outer shell, improves the problem of lithium deposition due to localized electrolyte deficiency, and has the effect of improving safety performance.

[0034] Referring to Figures 1 to 15, the present invention provides a secondary battery 100, which includes an outer casing 110, an electrode assembly 120, terminals 140, and a cover plate 130.

[0035] Referring to Figure 1, the outer shell 110 includes an end wall 111 and a side wall 112 surrounding the end wall 111. The connection between the end wall 111 and the side wall 112 can be achieved in various ways, such as by integral press molding, integral casting, or partial welding, as long as a stable sealing and electrical connection relationship can be formed. The enclosing shape of the side wall 112 is not limited and may be cylindrical or prismatic, or it may be enclosed in any closed-loop contour that fits the end wall 111. The axis of the outer shell 110 is defined as the first axis 114. In this embodiment, the outer edge of the end wall 111 is circular, the side wall 112 encloses 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 furthest from the end wall 111. Within the outer shell 110 enclosed by the end wall 111 and the side wall 112, a housing cavity is formed to accommodate the electrode assembly 120, electrolyte, and other battery necessary components. Specifically, the diameter of the outer shell 110 is determined according to the specific dimensions of the electrode assembly 120, for example, 18 mm, 21 mm, or 46 mm. The material of the outer shell 110 can be various, such as copper, iron, aluminum, steel, or aluminum alloy, and to prevent rusting of the outer shell 110 during long-term use, the surface of the outer shell 110 can be plated with a rust-preventive material such as metallic nickel.

[0036] Referring to Figures 1 and 2, the electrode assembly 120 is located inside the outer shell 110, and the electrode assembly 120 is a component in the secondary battery 100 where an electrochemical reaction occurs. The outer shell 110 can contain one or more electrode assemblies 120. The electrode assembly 120 includes a winding structure 126 formed by stacking a positive electrode plate 121, a negative electrode plate 123, and a separator 122, and winding it in the axial direction of the outer shell 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. The method for determining the second axis 1261 of the winding structure 126 is to first obtain the CT or cross-section of the secondary battery 100, and then take line segments connecting the radial ends of the electrode assembly 120 at positions close to both ends of the electrode assembly 120, and connect the midpoints of the two line segments. This connected line is defined as the second axis 1261 (see Figure 1).

[0037] Referring to Figures 1 and 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. The positive electrode current collector 1211 has a first coated region 1212 coated with the positive electrode active material layer and a first uncoated region 1213 not coated with the positive electrode active material layer. The first coated region 1212 and the first uncoated region 1213 are arranged along the axial direction of the outer shell 110, and the first uncoated region 1213 extends out of the separator 122 at one end in the height direction of the secondary battery 100, and is folded toward the second axis 1261 to form a positive electrode tab 125 that is stacked.

[0038] Referring to Figures 1 and 2, the negative electrode plate 123 includes a negative electrode current collector 1231 and a negative electrode active material layer coated on the negative electrode current collector 1231. The negative electrode current collector 1231 has a second coated region 1232 coated with the negative electrode active material layer and a second uncoated region 1233 not coated with the negative electrode active material layer. The second coated region 1232 and the second uncoated region 1233 are arranged along the axial direction of the outer shell 110, and the second uncoated region 1233 extends out of the separator 122 at the other end in the height direction of the secondary battery 100, and is folded toward the second axis 1261 to form a negative electrode tab 124 that is stacked.

[0039] Referring to Figures 1 and 2, the separator 122 is positioned between the positive electrode plate 121 and the negative electrode plate 123, separating the positive electrode active material layer from the negative electrode active material layer. Taking the lithium-ion secondary battery 100 as an example, the material of the positive electrode current collector 1211 may be aluminum, and the positive electrode active material layer contains positive electrode active material, which may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The material of the negative electrode current collector 1231 may be copper, and the negative electrode active material layer contains negative electrode active material, which may be carbon or silicon. The base material of the separator 122 may be polypropylene (PP) or polyethylene (PE). To protect and insulate the battery cells, an insulating film can be applied to the outside of the battery cells. This insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other polymer materials.

[0040] Referring to Figures 1 and 2, in the present invention, when the positive electrode tab 125 faces the end wall 111 or the opening 113, the negative electrode tab 124 faces the other end of the outer shell 110. In this embodiment, the positive electrode tab 125 faces the end wall 111 and is electrically connected to the terminal 140, making the terminal 140 the positive electrode, while the negative electrode tab 124 faces the opening 113 and the outer shell 110 is electrically connected to the negative electrode tab 124, making it the negative electrode. However, in another embodiment, the negative electrode tab 124 may be connected to the terminal 140 and the positive electrode tab 125 may be connected to the outer shell 110.

[0041] Referring to Figure 1, the cover plate 130 is sealed into the opening 113, the outer edge shape of the cover plate 130 corresponds to the shape of the opening 113, and it is connected to the side wall 112 to seal the opening 113. In a specific embodiment, a roll groove that is recessed toward the inside of the outer shell 110 is roll-formed in a region near the outer end of the side wall 112 of the outer shell 110, the roll groove restricts the axial displacement of the electrode assembly 120, one side of the roll groove forms an annular step surrounding the outer shell 110, the cover plate 130 is placed in this step, a seal ring is provided between the cover plate 130 and the side wall 112, and the edge of the opening 113 is crimped and sealed, with the cover plate 130 compressing the seal ring and forming a highly reliable connection.

[0042] In the secondary battery 100 of this application, the number of turns of the negative electrode plate 123 usually exceeds 40, and the cumulative expansion of the electrode assembly 120 increases with increasing number of turns. Furthermore, current secondary batteries 100 often employ silicon-based negative electrodes, which have higher energy storage capacity. However, considering that silicon-based negative electrodes undergo more significant volume expansion during the charge and discharge process, if the electrode assembly 120 is eccentric to one side of the outer shell 110, the effect of non-uniform stress from the outer shell 110 on the electrode assembly 120 becomes more pronounced. Moreover, referring to Figure 3, when the SOC of the secondary battery 100 is less than 5%, the second axis 1261 is limited to being located within a cylindrical region with a diameter d1 of 0.6 mm, with the first axis 114 as its axis. This configuration improves the coaxiality of the electrode assembly 120 and the outer shell 110, reduces the problem of uneven stress caused by the eccentricity of the electrode assembly 120 to one side of the outer shell 110, improves the problem of lithium deposition due to localized electrolyte deficiency, and enhances safety performance. In this technical solution, the positions of the second axis 1261 and the first axis 114 are both determined when the electrode assembly 120 is not expanded. To avoid the possibility of obtaining inaccurate results when measuring the secondary battery 100 in a charged and expanded state, the measurement is limited to when the state of charge (SOC) of the secondary battery 100 is less than 5%. When the energy of the secondary battery 100 is less than 5%, the number of turns of the negative electrode plate 123 is determined by observing the number of turns of the negative electrode plate 123 using the CT or cross-section of the electrode assembly 120.

[0043] Referring to Figure 4, in an example of the secondary battery 100 of the present invention, the electrode assembly 120 further includes a finishing adhesive 128 that wraps around the outer circumference of the winding structure 126 one or more times. The finishing adhesive 128 is not limited to the axial height of the electrode assembly 120, and can completely or partially cover the finishing adhesive 128. The finishing adhesive 128 may be one segment or multiple segments, and the multiple segments of the finishing adhesive 128 are spaced apart along the axial direction of the electrode assembly 120. Furthermore, along the winding direction of the winding structure 126, the end 1282 of the finishing adhesive 128 extends beyond the start end 1281, forming an overlap 1283. In this configuration, the starting end 1281 of the finishing adhesive 128 is held down by the ending end 1282, which enhances the fixing effect of the finishing adhesive 128. However, since the overlapping portion 1283 increases the local radial thickness of the winding structure 126, the distance between the overlapping portion 1283 and the side wall 112 is 0.2 mm or more, and may be, for example, 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, thereby ensuring a safe gap between the overlapping portion 1283 and the side wall 112, and mitigating the problem of electrolyte being pushed out and localized lithium deposition occurring due to the overlapping portion 1283 being compressed against the side wall 112 during battery charging expansion.

[0044] Referring to Figure 5, in an example of the secondary battery 100 of the present invention, the secondary battery 100 further includes a terminal 140, specifically, the terminal 140 penetrates the end wall 111 and is insulated from the end wall 111, and one end of the terminal 140 facing the electrode assembly 120 penetrates the end wall 111 and is electrically connected directly or indirectly to the positive electrode tab 125. The structure of the terminal 140 is any suitable shape that penetrates the end wall 111 and is electrically connected to the positive electrode tab 125 of the electrode assembly 120, for example, the cross section may be circular, square, prismatic, or an irregularly shaped contour that ensures stable conductivity, and the hole in the terminal 140 corresponds to the shape of the terminal 140, in this embodiment the cross section of the terminal 140 is circular.

[0045] Furthermore, referring to Figures 5 and 6, in this embodiment, the secondary battery 100 further includes a first current collector 150, one side of which is fixedly connected to a terminal 140, and the other side of which is fixedly connected to a positive electrode tab 125. There are various methods for connecting the first current collector 150 and the positive electrode tab 125, such as welding or using a conductive adhesive, as long as it ensures an electrical connection between the first current collector 150 and the positive electrode tab 125 and satisfies the conductivity requirements. In this embodiment, welding is used, and the first current collector 150 and the terminal 140 are also fixed by welding.

[0046] Furthermore, in order to insulate and isolate the exposed tabs near the outside of the winding structure 126 from the outer shell 110, a covering layer 129 is provided on the edge of the first current collector member 150 and on one end of the electrode assembly 120 near the first current collector member 150. Referring to Figures 1 and 5 to 9, the covering layer 129 isolates at least the positive electrode tab 125 from the outer shell 110. The covering 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 may be an integrated structure or separate structures, but are not limited to this. It is sufficient that the first covering portion 1291 covers the edge of the first current collector member and the second covering portion 1292 covers the outer circumference of one end of the electrode assembly 120 near the first current collector member 150. The installation of the covering layer 129 can, on the one hand, isolate the positive electrode tab 125 from the outer shell 110, and on the other hand, protect the exposed positive electrode tab 125, thereby providing protection to the positive electrode tab 125 and reducing the risk of the positive electrode tab 125 breaking and falling into the battery, causing a short circuit.

[0047] Referring further to Figures 1 and 5-9, the second coating portion 1292 also includes a compressible elastic layer 1293. The second coating portion 1292, having a certain thickness, acts as a preliminary guide when inserting the electrode assembly 120 into the outer shell 110. A gap of at least the thickness of the second coating portion 1292 exists between the electrode assembly 120 and the side wall 112, improving the coaxiality of the electrode assembly 120 and the outer shell 110. This reduces the problem of uneven stress on the electrode assembly 120 in the outer shell 110 due to the electrode assembly 120 being eccentric to one side of the outer shell 110, improving the problem of lithium deposition due to localized electrolyte deficiency, and thus improving safety performance. In addition, the compressible nature of the second coating portion 1292 reduces its thickness when the battery expands, thereby reducing stress concentration. Preferably, the thickness b of the second covering portion 1292 is in the range of b ≤ 0.2 mm, and may be, for example, 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.18 mm, or 0.2 mm. A second covering portion 1292 with a thickness within this range can serve as a preliminary guide for the electrode assembly 120 and does not affect the insertion of the electrode assembly 120 into the outer shell.

[0048] In an example of the secondary battery 100 of the present invention, referring to Figures 1 and 5-6, the first coating portion 1291 also includes an elastic layer 1293 and is integrally molded with the second coating portion 1292. This configuration allows for the integral molding and packaging of the first coating portion 1291 and the second coating portion 1292, simplifying the packaging process for the coating layer 129 and improving processing efficiency. The coating layer 129 further includes a first adhesive layer 1294 that adheres and fixes the elastic layer 1293 to the electrode assembly 120 and the first current collector 150. The material of the elastic layer 1293 may be any material having elastic and insulating properties, and is not limited thereto, for example, polyethylene foam, ethylene vinyl acetate copolymer foam, polyurethane foam, or polypropylene foam. The first adhesive layer 1294 may be made of any material capable of adhering and fixing the elastic layer 1293 to the electrode assembly 120 and the first current collector 150, and is not limited thereto. For example, it may be a silicone adhesive, polyurethane adhesive, epoxy resin adhesive, acrylic adhesive, or synthetic rubber adhesive.

[0049] In another example of the secondary battery 100 of the present invention, referring to Figures 7 to 9, the second covering portion 1292 includes a base layer 1295 integrally molded 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 molded, but it may also be a separate structure. The edge of the first current collector member 150 is covered only by the base layer 1295, and this configuration increases the capacity of the secondary battery 100 in the height direction. By providing the elastic layer 1293 only in the second covering portion 1292, this configuration improves the coaxiality of the electrode assembly 120 and the outer shell 110 while simultaneously reducing material costs. The material of the base layer 1295 may be polyimide tape, polytetrafluoroethylene tape, or epoxy film tape, and the material of the elastic layer 1293 may be any material that is elastic and insulating, but is not limited thereto, such as polyethylene foam, ethylene vinyl acetate copolymer foam, polyurethane foam, or polypropylene foam. The first adhesive layer 1294 may be any material that can adhere and fix the elastic layer 1293 to the electrode assembly 120, but is not limited thereto, such as silicone adhesive, polyurethane adhesive, epoxy resin adhesive, acrylic adhesive, or synthetic rubber adhesive.

[0050] Referring to Figures 10 to 12, in an example of the secondary battery 100 of the present invention, the secondary battery 100 further includes an insulating plastic 170 that insulates at least the positive electrode tab 125 from the outer shell 110, and the insulating plastic 170 plays a role in isolating and insulating the positive electrode tab 125 from the outer shell 110. The material of the insulating plastic 170 is not limited and may be any of soluble polytetrafluoroethylene (Perfluoroalkoxy, abbreviated as PFA), polybutylene terephthalate (Polybutylene Terephthalate, abbreviated as PBT), liquid crystal polymer (Liquid Crystal Polymer, abbreviated as LCP), PP, polyphenylene sulfide (Polyphenylene Sulfide, abbreviated as PPS), or 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 via a first current collector 150. Therefore, the first insulator 171 is also located between the first current collector 150 and the end wall 111 and is used to isolate the first current collector 150 from 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 from the side wall 112. Furthermore, the second insulator 172 plays a positioning role between the electrode assembly 120 and the side wall 112, and a gap of at least the thickness of the second insulator 172 exists between the electrode assembly 120 and the side wall 112, which improves the coaxiality of the electrode assembly 120 and the outer shell 110, reduces the problem of uneven stress on the electrode assembly 120 from the outer shell 110 due to the electrode assembly 120 being eccentric to one side of the outer shell 110, improves the problem of lithium deposition due to localized electrolyte deficiency, and has the effect of improving safety performance.

[0051] Referring to Figures 11 and 12, in an example of the secondary battery 100 of the present invention, a chamfer 173 is provided on the inner wall of the end of the second insulator 172 that is farther from the first insulator 171. That is, the chamfer 173 is provided on the side into which the electrode assembly 120 is inserted into the outer shell 110. This configuration acts as a preliminary guide when inserting the electrode assembly 120 into the outer shell 110, improving assembly efficiency, and also reduces the contact area between the electrode assembly 120 and the second insulator 172, thereby promoting heat dissipation.

[0052] Considering that the chamfered portion 173 of the second insulator 172 is thin and easily bends inward toward the outer shell 110, potentially interfering with the insertion of the electrode assembly 120 into the outer shell and affecting assembly quality, in an example of the secondary battery 100 of the present invention, referring to Figures 11 and 12, a third adhesive layer 174 is provided on the outside of the second insulator 172 to bond and fix the second insulator 172 to the side wall 112. This configuration prevents the second insulator 172 from interfering when the electrode assembly 120 is inserted into the outer shell 110, while simultaneously avoiding the formation of a gap between the second insulator 172 and the side wall 112. Furthermore, it facilitates the insertion of the electrode assembly 120 into the outer shell, resulting in improved assembly efficiency and assembly quality.

[0053] Referring to Figure 13, in an example of the secondary battery 100 of the present invention, the secondary battery 100 further includes a second current collector 160, the second current collector 160 including a current collector body 161 and an outer shell connection portion 162 provided on the outer periphery of the current collector body 161. The current collector body 161 is fixedly connected to a negative electrode tab 124, and the outer shell connection portion 162 is fixedly connected to a side wall 112, the outer shell connection portion 162 may be an overall annular structure or one or more fan-shaped annular structures, as long as the conductivity requirements and weld strength requirements between the second current collector 160 and the outer shell 110 are met. The radius of the outer edge of the outer shell connection portion 162 is larger than the radius of the electrode assembly 120, and the axis of the second current collector member 160 is the third axis 163. After welding the outer shell connection portion 162 and the outer shell 110, the second current collector member 160 performs a certain positioning action relative to the electrode assembly 120. The third axis 163 is located within a cylindrical region with a diameter d2 of 0.2 mm, with the second axis 1261 as its axis. This configuration improves the coaxiality between the electrode assembly 120 and the second current collector member 160, improves the coaxiality between the electrode assembly 120 and the outer shell 110, ensures a safe gap between the electrode assembly and the side wall 112, reduces the problem of uneven stress on the electrode assembly 120 from the outer shell 110 due to the electrode assembly 120 being eccentric to one side of the outer shell 110, improves the problem of lithium deposition due to localized electrolyte deficiency, and improves safety performance.

[0054] Referring to Figure 14, the present invention further provides a battery pack 10 which includes any of the above secondary batteries 100. In one embodiment of the battery pack 10 of the present invention, the battery pack 10 includes a housing 101, a housing lid 102, and a plurality of secondary batteries 100. The plurality of secondary batteries 100 are arranged inside the housing 101 and connected to each other in series, parallel, or a combination of series and parallel. The housing lid 102 seals the housing 101 and protects the plurality of secondary batteries 100. In addition to the secondary batteries 100 of the present invention, the battery pack 10 may also include a thermal management system for the battery pack 10, a circuit board, etc. The battery pack 10 may be a battery module, a battery pack, or an energy storage cabinet, etc., but these will not be described in detail here.

[0055] Referring to Figure 15, the present invention further provides an electronic device 1, which includes the battery pack 10. The actuation unit 11 is electrically connected to the battery pack 10 and receives power. As an example, the electronic device 1 is a vehicle, which is a fuel-powered vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle is, but is not limited to, a pure electric vehicle, a hybrid vehicle, or a range-extender vehicle. The actuation unit 11 is the vehicle body, and the battery pack 10 is located at the bottom of the vehicle body and supplies power to the vehicle's movement or the operation of in-vehicle electrical components. However, in other embodiments, the electronic device 1 is a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, or a power tool. Spacecraft include airplanes, rockets, space shuttles, and other spacecraft. The actuation unit 11 is a unit component that receives power from the battery pack 10 and performs a corresponding operation, such as a fan blade rotation unit or a vacuum cleaner suction unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, electric airplane toys, and so on. Power tools include metal cutting power tools, grinding power tools, assembly power tools, railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The embodiments of this application do not impose any special limitations on the electronic device 1 described above.

[0056] The secondary battery of the present invention has the axis of the outer shell as the first axis and the axis of the winding hole of the electrode assembly as the second axis, and when the State of Charge (SOC) of the secondary battery is less than 5%, the second axis is limited to being located within a cylindrical region with a diameter d1 of 0.6 mm radius, with the first axis as the axis. This configuration improves the coaxiality of the electrode assembly and the outer shell, reduces the problem of uneven stress on the electrode assembly from the outer shell due to the eccentricity of the electrode assembly to one side of the outer shell, improves the problem of lithium deposition due to localized electrolyte deficiency, and achieves the effect of improving safety performance. Therefore, the present invention effectively overcomes several practical problems of the prior art and has very high utility and significance. The above embodiments are illustrative in explaining the principle and effect of the present invention and do not limit the present invention. Those skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations that those skilled in the art can complete without departing from the spirit and technical idea disclosed in the present invention are included in the claims of the present invention. [Industrial applicability]

[0057] The secondary battery of the present invention improves the coaxiality between the electrode assembly and the outer shell, ensures a uniform safety gap between the electrode assembly and the inner wall of the outer shell, mitigates the problem of uneven stress on the electrode assembly from the outer shell during the battery's charging and discharging process, improves the problem of lithium deposition due to localized electrolyte deficiency, and enhances safety performance. [Explanation of symbols]

[0058] 1 Electronic equipment 10 battery packs 11 Operating part 101 cabinets 102 Casing cover 100 Secondary battery 110 Outer shell 111 End wall 112 Side wall 113 Aperture 114 First axis 120 Electrode Assembly 121 Positive electrode plate 1211 Positive electrode current collector 1212 First Coating Area 1213 First uncoated area 122 Separator 123 Negative electrode plate 1231 Negative electrode current collector 1232 Second coating area 1233 Second uncoated area 124 Negative Electrode Tabs 125 Positive Tab 126-wound structure 1261 Second axis 127 winding holes 128 Finishing adhesive 1281 Starting point 1282 Termination 1283 Overlapping section 129 Covering layer 1291 First covering part 1292 Second covering part 1293 Elastic layer 1294 First adhesive layer 1295 basal layer 1296 Second adhesive layer 130 Lid plate 140 terminals 150 First current collector 160 Second current collector 161 Current collector body 162 Outer shell connection part 163 Third axis 170 Insulating Plastic 171 First Insulator 172 Second insulator 173 Chamfering 174 Third adhesive layer

Claims

1. An outer shell including an end wall and a side wall surrounding the end wall, the axis of which is the first axis, An electrode assembly comprising a winding structure housed within the aforementioned outer shell, in which a positive electrode plate, a negative electrode plate, and a separator are stacked and wound, wherein the number of turns of the negative electrode plate exceeds 40, and the axis of the winding structure is the second axis, Equipped with, A secondary battery characterized in that, when the state of charge (SOC) of the secondary battery is less than 5%, the second axis is located within a cylindrical region with a diameter d1 of φ0.6 mm, with the first axis as its axis.

2. The secondary battery according to claim 1, wherein the electrode assembly further includes a finishing adhesive that wraps around the outer circumference of the winding structure one or more times, and the end of the finishing adhesive is positioned beyond the start end of the finishing adhesive along the winding direction of the winding structure, forming an overlap, and the distance between the overlap and the side wall is 0.2 mm or more.

3. The secondary battery according to claim 1, further comprising a terminal, a first current collector member, and a coating layer, wherein the terminal penetrates the end wall and is insulated from the end wall, the end of the positive electrode plate includes a positive electrode tab bent toward the second axis, one side of the first current collector member is fixedly connected to the terminal, the other side of the first current collector member is fixedly connected to the positive electrode tab, the coating layer insulates at least the positive electrode tab from the outer shell, the 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, the second coating portion covers the outer circumference of the end of the electrode assembly near the first current collector member, the second coating portion includes a compressible elastic layer, and the thickness b of the second coating portion is in the range b ≤ 0.2 mm.

4. The secondary battery according to claim 3, wherein the first covering portion also includes the elastic layer and is integrally molded with the second covering portion, and the covering layer further includes a first adhesive layer that adheres and fixes the elastic layer to the electrode assembly and the first current collector.

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

6. The secondary battery according to claim 1, wherein the end of the positive electrode plate protrudes beyond the separator in the direction of the end wall along the second axis and includes a positive electrode tab that is bent toward the second axis, and further includes an insulating plastic that insulates at least the positive electrode tab from the outer shell, wherein the insulating plastic includes a first insulator and a second insulator, the first insulator located between the positive electrode tab and the end wall, and the second insulator located between the side wall and the electrode assembly.

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

8. The secondary battery according to claim 7, characterized in that a third adhesive layer is provided on the outside of the second insulator for bonding and fixing the second insulator and the side wall together.

9. The secondary battery according to claim 1, further comprising a negative electrode plate whose end protrudes beyond the separator in a direction away from the end wall along the second axis and includes a negative electrode tab bent toward the second axis, the second current collector member comprising a current collector body and an outer shell connecting portion provided on the outer periphery of the current collector body, the current collector body being fixedly connected to the negative electrode tab, the outer shell connecting portion being fixedly connected to the side wall, the radius of the outer edge of the outer shell connecting portion being greater than the radius of the electrode assembly, the axis of the second current collector member being the third axis, and the third axis being located within a cylindrical region with a diameter d2 of φ0.2 mm and the second axis as its axis.

10. A battery pack characterized by including a secondary battery according to any one of claims 1 to 9.

11. An electronic device characterized by including the battery pack described in claim 10.

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