Secondary battery, battery pack, and electronic device

Abstract

The embodiment of the utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery comprises a shell; the electrode assembly is arranged in the shell, the first pole piece, the first diaphragm, the second pole piece and the second diaphragm are sequentially stacked and then wound to form the electrode assembly, the ending end of the second pole piece exceeds the ending end of the first pole piece in the winding direction of the electrode assembly, and the second pole piece comprises a tail section exceeding the ending end of the first pole piece; a preset area is defined by a gap between one side, facing a winding center hole of the electrode assembly, of the tail section and the second pole piece of the adjacent inner ring; at least one part of the insulating part is fixed in the preset area in the height direction of the electrode assembly, and the thickness of the insulating part is not larger than that of the first pole piece. According to the embodiment, the problem that the local stress is too large after the electrode assembly is expanded can be solved at least.

Description

Technical Field

[0001] This utility model relates to a secondary battery, a battery pack, and an electronic device. Background Technology

[0002] In the field of new energy power batteries, the application of rechargeable batteries is becoming increasingly widespread. These batteries (such as lithium-ion batteries) can be used in vehicles, energy storage, mobile phones, tablets, wearable devices, power banks, e-cigarettes, digital products, power tools, power units, and other electronic devices. One type of rechargeable battery is the cylindrical battery, which includes a casing and an electrode assembly. The electrode assembly consists of a positive electrode, a first separator, a negative electrode, and a second separator, which are stacked sequentially and wound to form the electrode assembly, which is then encapsulated within the casing. The expansion of the electrode assembly within the casing of a rechargeable battery generates high expansion pressure, which may affect battery performance. Utility Model Content

[0003] In view of the problems existing in the related technologies, the purpose of this utility model is to provide a secondary battery, battery pack and electronic device to at least alleviate the problem of excessive local stress after the electrode assembly expands.

[0004] To achieve the above objectives, embodiments of this application provide a secondary battery comprising: a casing; an electrode assembly disposed within the casing, wherein a first electrode, a first separator, a second electrode, and a second separator are sequentially stacked and wound to form the electrode assembly, wherein in the winding direction of the electrode assembly, the tail end of the second electrode extends beyond the tail end of the first electrode, the second electrode includes a tail section extending beyond the tail end of the first electrode, and a predetermined region is defined by the gap between the tail section and the adjacent inner ring of the second electrode on the side facing the winding center hole of the electrode assembly; and an insulating member, at least a portion of which is fixed within the predetermined region along the height direction of the electrode assembly, the thickness of which is not greater than the thickness of the first electrode.

[0005] In some embodiments, the insulating element is an insulating tape connected to the side of the tail section facing the winding center hole.

[0006] In some embodiments, in the winding direction, the starting end of the insulating tape is located within a preset area, and the ending end of the insulating tape extends beyond the preset area.

[0007] In some embodiments, the length by which the end of the second electrode extends beyond the end of the first electrode in the winding direction is L, and the distance between the beginning of the insulating tape and the end of the first electrode is L1, wherein L>L1≥3mm.

[0008] In some embodiments, the insulating tape includes a substrate and an adhesive layer. The substrate is made of PET, the thickness of the insulating tape is d, the thickness of the first electrode is D, and the value of d / D ranges from 0.0625 to 0.875.

[0009] In some embodiments, the second electrode includes a current collector and an active material layer disposed on a portion of the surface of the current collector, wherein opposite ends of the insulating strip along the height direction extend beyond opposite ends of the active material layer.

[0010] In some embodiments, the insulating element is a pad connected to the end of the first electrode, the pad including an end portion away from the end of the first electrode, and at least the end portion of the pad having a decreasing thickness along the winding direction.

[0011] In some embodiments, the first electrode is a positive electrode, which includes a positive active material, including a lithium-containing nickel-cobalt-manganese composite oxide; the second electrode is a negative electrode, which includes a negative active material, including a silicon-based material; the secondary battery is a cylindrical battery; and the insulating component is used to reduce the stress on the electrode assembly from the tail end of the second electrode after the electrode assembly expands and squeezes the outer casing.

[0012] Embodiments of this application also provide a battery pack comprising any of the cylindrical batteries described above.

[0013] Embodiments of this application also provide an electronic device that includes the battery pack described above.

[0014] The beneficial technical effects of this utility model are as follows:

[0015] By placing an insulating component with a thickness no greater than that of the first electrode in a predetermined region defined between the end of the second electrode and the end of the first electrode, the thickness change at the end of the second electrode can be mitigated, allowing for a smooth transition of the stepped structure at the end. Therefore, after the electrode assembly expands and compresses the housing, the stress generated by the thickness change at the end of the second electrode is reduced, thereby alleviating the stress on the inner ring of the electrode assembly at the end of the second electrode. This reduces quality problems such as lithium plating, electrode deformation, and even electrode breakage caused by localized stress concentration, improving battery performance and lifespan. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1A and Figure 1B The diagram shows a cross-sectional view of a portion of an electrode assembly in an existing cylindrical battery before and after expansion.

[0018] Figure 1C The equivalent plastic strain curves of the multilayer electrode at the end of the adjacent negative electrode of an existing cylindrical battery are shown.

[0019] Figure 2 A perspective view of a secondary battery according to an embodiment of this application is shown.

[0020] Figure 3 A cross-sectional view of a secondary battery according to an embodiment of this application is shown.

[0021] Figure 4A This is a cross-sectional view of the electrode assembly of a secondary battery according to an embodiment of this application in a section perpendicular to the axis.

[0022] Figure 4B yes Figure 4A A magnified view of the area at the ends of the first and second electrodes.

[0023] Figure 5A This is a schematic diagram of a pad disposed at the end of the first electrode according to an embodiment of this application.

[0024] Figure 5B and Figure 5C These are schematic diagrams of pads disposed at the end of the first electrode sheet according to different embodiments of this application.

[0025] Figure 6 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle. Detailed Implementation

[0026] To better understand the spirit of the embodiments of this application, the following description is based on some preferred embodiments of this application.

[0027] Embodiments of this application will be described in detail below. Throughout this specification, identical or similar components and components having identical or similar functions are indicated by similar reference numerals. The embodiments described herein with reference to the accompanying drawings are illustrative and diagrammatic in nature and are intended to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0028] As used herein, the terms “approximately,” “substantially,” “substantially,” and “about” are used to describe and indicate minor variations. When used in conjunction with an event or situation, the terms may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately.

[0029] In this specification, unless otherwise specified or limited, relative terms such as “central,” “longitudinal,” “lateral,” “front,” “rear,” “right,” “left,” “inner,” “outer,” “lower,” “higher,” “horizontal,” “vertical,” “above,” “below,” “above,” “below,” “top,” “bottom,” and their derivatives (e.g., “horizontally,” “downward,” “upward,” etc.) should be interpreted as referring to the directions described in the discussion or depicted in the accompanying drawings. These relative terms are used for descriptive convenience only and do not require that this application be constructed or operated in a particular orientation.

[0030] For ease of description, "first," "second," "third," etc., can be used in this article to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe the corresponding components.

[0031] Cylindrical batteries (such as cylindrical lithium-ion batteries) have been widely used in electric vehicles and other fields in recent years due to their high energy density, low cost, and high production efficiency. On the one hand, compared to pouch and prismatic batteries, cylindrical batteries have a more compact internal structure and occupy less internal space. On the other hand, the positive and negative electrodes of cylindrical batteries often use high-nickel ternary materials and silicon materials, making them more prone to volume expansion. Furthermore, cylindrical batteries generally use steel shells with higher structural rigidity and strength as the outer casing material. Combining these three aspects, the expansion of the electrode components in a cylindrical battery will generate higher expansion pressure within the internal core.

[0032] Figure 1A and Figure 1B Schematic cross-sectional views of a portion of the electrode assembly in a cylindrical battery before and after expansion are shown, respectively. It should be understood that... Figure 1A and Figure 1B The positive electrode and separator are not shown. (Reference) Figure 1A As shown, the electrode assembly 12 is wound using a layer-by-layer winding method. Because its winding structure is in the form of an Archimedean spiral, there will inevitably be a tiny step at the ends of the positive and negative electrode plates 15. Specifically, as... Figure 1A As shown, at the end 15e of the negative electrode 15, there is a small step 30. The total thickness of the positive and negative electrodes on one side S1 of this end 15e is one more layer thicker than the total thickness of the positive and negative electrodes on the other side S2 of this end 15e. Furthermore, because the expansion pressure inside the cylindrical battery is high, the outer shell of the electrode assembly has high rigidity and is not easily deformed. Therefore, after expansion, as... Figure 1BAs shown, the negative electrode 15 is pressed tightly against the side wall 20 of the outer casing. The step 30 formed by the end 15e of the negative electrode 15 will interact with the side wall 20 (as shown by forces F1 and F2). At this time, the inner ring electrode of the end 15e will be subjected to an additional shear force due to the presence of the step. According to calculation results, a large local stress will be generated in such a step area, causing local deformation of the electrode, and the effect of this step will affect the multilayer electrode inside the step. Figure 1C As shown in the test results, the impact range of the step can even exceed 5 layers. The 67th layer is the closest to the end of the negative electrode. Local stress concentration can also lead to lithium plating, and even electrode breakage due to excessive shear stress. Since the group margin of cylindrical batteries can be as high as 97% to 98%, which is much higher than that of prismatic batteries, the outermost negative electrode of cylindrical batteries is more prone to electrode breakage at the end of the cycle.

[0033] In current cylindrical battery designs, tape is typically used to wrap the electrode components, which can reduce stress concentration in the "step area" to some extent, but the improvement is limited. Using foam or other similar fillers to wrap the outer surface of the core would encroach on the internal space of the cylindrical battery, affecting its energy density. To address these issues, this application provides a secondary battery.

[0034] Figure 2 A perspective view of a secondary battery 100 according to an embodiment of this application is shown. Figure 3 A cross-sectional view of a secondary battery 100 according to an embodiment of this application is shown.

[0035] Combination Figures 2 to 3As shown, the secondary battery 100 includes a casing, which comprises a housing 200 and a cover plate 220. Specifically, the housing 200 includes a peripheral sidewall 109 and an end wall 111 connected to one end of the peripheral sidewall 109. An opening 205 is provided at the other end of the peripheral sidewall 109 opposite to the end wall 111, and the cover plate 220 covers the opening 205 of the housing 200. The cover plate 220 can be used to encapsulate the electrode assembly 120 and the electrolyte together with the housing 200. The housing 200 can be made of any of a variety of available materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The housing 200 can be cylindrical and define a receiving cavity in which the electrode assembly 120 is disposed. The outer diameter of the housing 200 can be determined according to the specific diameter of the electrode assembly 120; for example, the outer diameter of the housing 200 can be, for example, 18 mm, 21 mm, 46 mm, etc. In some embodiments, the secondary battery 100 may be a 4680 cylindrical battery (outer diameter 46mm, height 80mm), or a 4695 cylindrical battery (outer diameter 46mm, height 95mm), or a 46120 cylindrical battery (outer diameter 46mm, height 120mm).

[0036] The electrode assembly 120 can be formed primarily by sequentially stacking and winding a positive electrode sheet, a negative electrode sheet, and a separator located between the positive and negative electrode sheets. The positive electrode sheet, negative electrode sheet, and separator can be wound around an axis Lc. Furthermore, the electrode assembly 120 also has a winding center hole 120c, and the axis Lc can be the axis of the winding center hole 120c. The wound electrode assembly 120 can have a winding center hole 120c. In some embodiments, the positive electrode sheet may include a positive current collector and a positive active material layer, the positive active material layer being coated on a portion of the surface of the positive current collector. The uncoated area of ​​the positive current collector not covered by the positive electrode coating area is used to form a positive electrode tab 125. The negative electrode sheet may include a negative current collector and a negative active material layer, the negative active material layer being coated on a portion of the surface of the negative current collector. The uncoated area of ​​the negative current collector not covered by the negative electrode coating area is used to form a negative electrode tab 124.

[0037] An inwardly protruding groove 113 (also referred to as a crimping portion) is formed on the peripheral sidewall of the housing 200 near the opening 205. An electrode assembly 120 is disposed between the end wall 111 and the groove 113, and the groove 113 restricts the movement of the electrode assembly 120 in the height direction Z and its opposite direction between the end wall 111 and the groove 113. The direction from the opening 205 to the end wall 111 is the height direction Z. The end of the peripheral sidewall 109 of the housing 200 on the opening 205 side can be configured as a rolled edge portion 32, which extends radially inward into the housing 200, perpendicular to the height direction Z. The rolled edge portion 32 and the groove 113 are spaced apart along the height direction Z, and the groove 113 and the rolled edge portion 32 can jointly clamp the cover plate 220. The cover plate 220 can be electrically insulated from the housing 200.

[0038] The cover plate 220 may have a weak part. When the battery experiences thermal runaway, the high-temperature and high-pressure emissions inside can be discharged to the outside through the weak part on the cover plate 220 after breaking through the bottom of the battery, thereby achieving good discharge of the emissions.

[0039] The negative electrode tab 124 of the electrode assembly 120 faces the opening 205 and can be electrically connected to the housing 200 via a negative electrode current collector 201 located between the cover plate 220 and the electrode assembly 120, thereby making the housing 200 negatively charged. The negative electrode current collector 201 can be welded to the housing 200 by laser welding. Specifically, the welding position of the negative electrode current collector 201 to the housing 200 is located on the side of the groove 113 facing the electrode assembly 120.

[0040] The secondary battery 100 may further include a terminal post 160, which passes through and is insulated from the end wall 111. The terminal post 160 can be electrically connected to the positive electrode tab 125 of the electrode assembly 120 via a positive current collector 202 located between the terminal post 160 and the electrode assembly 120, thereby making the terminal post 160 positively charged. In some embodiments, the terminal post 160 can be welded to the positive current collector 202 by laser penetration welding.

[0041] In one example of the secondary battery 100 of the present invention, the method for manufacturing the secondary battery 100 of the present invention includes the following steps:

[0042] Winding: A winding structure formed by stacking and winding negative electrode sheet, separator and positive electrode sheet, the uncoated part of the negative current collector of negative electrode sheet and the positive current collector of positive electrode sheet is used as positive electrode tab 125 and negative electrode tab 124, and the positive electrode tab 125 and negative electrode tab 124 are bent along the radial direction of electrode assembly 120.

[0043] Welding of current collectors to electrode assemblies: The positive current collector 202 and the negative current collector 201 are welded to the surface areas of the bent positive electrode tab 125 and the negative electrode tab 124, respectively.

[0044] Installation into the housing: The electrode assembly 120, which has been welded to the negative current collector 201 and the positive current collector 202, is installed into the housing 200 through the opening 205. The method of installing the electrode assembly 120 in this step is not limited. For example, it can be installed manually or by a robot.

[0045] Install pole 160.

[0046] Electrolyte injection: The method of electrolyte injection is not limited, and injection can be carried out through opening 205. In this embodiment, electrolyte is injected through opening 205, which reduces the step of opening an injection hole in the end wall 111. The existing opening 205 can be used directly for injection, simplifying the process and reducing costs.

[0047] Sealing: The cover plate 220 is sealed and installed on the opening 205. There are various sealing methods, and this is not limited to one. In some embodiments, a rolling groove 113 recessed towards the center of the housing 200 is first formed on the outer periphery of the housing 200 to restrict the movement of the electrode assembly 120 along the height direction Z. Then, a mechanical sealing process is used to press and seal the cover plate 220 to form a rolled edge 32, thereby sealing and installing the cover plate 220 on the opening 205 of the housing 200. This step is a mature process, low in cost, and highly efficient.

[0048] Figure 4A This is a cross-sectional view of the electrode assembly 120 of a cylindrical battery according to an embodiment of this application, in a section perpendicular to the axis Lc. It should be understood that the wound electrode assembly 120 has a wound central hole 120c, and the axis Lc of the wound central hole 120c extends in the Z direction (see...). Figure 3 ), Figure 4A The XY plane shown is a cross-section perpendicular to the axis Lc. The orthographic projection of the axis Lc along the axial direction of the winding center hole 120c onto the cross-section forms a projection point P. The winding center hole 120c is located in... Figure 4A The cross-section shown can have a circular shape. The projection point P can be the center of the circle surrounding the central hole 120c.

[0049] See Figure 4A The electrode assembly 120 may include a first electrode 121, a first separator, a second electrode 122, and a second separator. The first electrode 121, the first separator, the second electrode 122, and the second separator are sequentially stacked and wound along the winding direction D to form the electrode assembly 120. Furthermore, the secondary battery may also include an electrolyte, which may be located between the first electrode 121, the separator, and the second electrode 122. In some embodiments, the first electrode 121 is a positive electrode, and the second electrode 122 is a negative electrode.

[0050] The positive electrode sheet can include a positive current collector and a positive active material layer coated on both sides of the positive current collector. The portion of the positive current collector not coated with the positive active material layer constitutes the positive electrode tab. The negative electrode sheet can include a negative current collector and a negative active material layer coated on both sides of the negative current collector. The portion of the negative current collector not coated with the negative active material layer constitutes the negative electrode tab. Taking a lithium-ion battery as an example, the material of the positive current collector can be aluminum, and the positive active material layer can include positive active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. For high-nickel ternary lithium batteries, the positive active material can be a ternary material composed of nickel, cobalt, and manganese (or aluminum), where the nickel content is usually relatively high, generally above 60%. The material of the negative current collector can be copper, and the negative active material layer can include negative active material, which can be carbon or silicon, etc.

[0051] By coating a positive electrode active material layer on the positive electrode sheet, the positive electrode active material layer contains lithium ions. When the positive electrode active material layer comes into contact with the electrolyte and the battery is charged, the lithium ions in the positive electrode active material layer will move through the electrolyte to the negative electrode active material layer and be embedded in the negative electrode active material layer. This process is the lithium ion activation process, which is also the battery charging process.

[0052] See Figure 4A In the winding direction D of the electrode assembly 120, the terminal end 122e of the second electrode 122 extends beyond the terminal end 121e of the first electrode 121, allowing the second electrode 122 to cover the terminal end 121e of the first electrode 121. Therefore, lithium ions detached from the positive active material layer of the first electrode 121 (positive electrode) can be smoothly inserted into the negative active material layer of the second electrode 122 (negative electrode), thus preventing lithium plating at the terminal end of the negative electrode.

[0053] To achieve electrical insulation, the first diaphragm 141 and the second diaphragm 142 form the outermost ring of the electrode assembly 120 along the winding direction D. The terminal ends 141e of the first diaphragm 141 and 142e of the second diaphragm 142 constitute the terminal ends of the electrode assembly 120. Figure 4A In the illustrated embodiment, the terminal ends 141e of the first diaphragm 141 and 142e of the second diaphragm 142 are substantially aligned. It should be understood that in this application, alignment means that the terminal ends 141e and 142e of the first diaphragm 141 and the second diaphragm 142 differ by less than 5 mm. In other embodiments, the terminal ends 141e and 142e of the first diaphragm 141 and the second diaphragm 142 may not be aligned.

[0054] In addition, the cylindrical battery may also include a termination insulating film 300, which can be used to fix the termination ends of the electrode assembly to fix the first electrode 121, the first separator 141, the second electrode 122, and the second separator 142, and maintain the tightness of the winding of the electrode assembly 120. The termination insulating film 300 may be disposed on the termination ends 141e of the first separator 141 and / or the termination ends 142e of the second separator 142 exposed on the outer peripheral surface of the electrode assembly 120. In this embodiment, the termination insulating film 300 wraps around the electrode assembly 120 at least once in the winding direction D. In some embodiments, the distance E1 by which the termination end 300e of the termination insulating film 300 extends beyond the starting end 300s of the termination insulating film 300 beyond the winding end can be 0-3 mm.

[0055] In some embodiments, the finishing insulating film 300 may be synthesized, for example, from PP (polypropylene), PE (polyethylene), PET (polyethylene terephthalate), PVC (polyvinyl chloride) or other polymer materials.

[0056] In some embodiments, in the winding direction D of the electrode assembly 120, the starting end 122s of the second electrode 122 extends beyond the starting end 121s of the first electrode 121. By configuring the starting end 122s of the second electrode 122 to extend beyond the starting end 121s of the first electrode 121, lithium ions detached from the positive active material layer of the first electrode 121 (positive electrode) can be readily inserted into the negative active material layer of the second electrode 122 (negative electrode), thereby preventing lithium plating at the starting end on the negative electrode. Similarly, in the opposite direction of the winding direction D, the starting end 122s of the second electrode 122 extends beyond the starting end 121s of the first electrode 121. In this way, lithium ions that detach from the positive active material layer of the first electrode 121 (positive electrode) can be smoothly inserted into the negative active material layer of the second electrode 122 (negative electrode) in the inner ring of the electrode assembly, thereby avoiding lithium plating at the starting end on the second electrode 122.

[0057] Figure 4B yes Figure 4A A magnified view of region Ae at the termination points of the first and second electrodes. (Reference) Figure 4A and Figure 4B As shown, the second electrode 122 includes a tail section 122p that extends beyond the end 121e of the first electrode 121. A predetermined region Sp is defined by the gap between the tail section 122p on the side facing the winding center hole 120c of the electrode assembly and the adjacent inner ring of the second electrode 122.

[0058] An insulating tape 400 is disposed within the preset area Sp and fixed to the end 122e of the second electrode 122. The length direction of the insulating tape 400 is along the height direction Z of the electrode assembly 120, and the insulating tape 400 extends along the height direction Z.

[0059] The thickness of the insulating tape 400 is no greater than the thickness of the first electrode 121. If the thickness of the insulating tape 400 is greater than the thickness of the first electrode 121, the end 122e of the second electrode 122 may be raised, which will affect the diameter of the cell assembly and cause a thickness difference. When the electrode assembly expands during use, lithium plating is likely to occur.

[0060] The above-described technical solution of this application, by providing an insulating strip 400 (which can be called an insulating element) in the preset region Sp at the end 122e of the second electrode 122, and the thickness of the insulating strip 400 is no greater than the thickness of the first electrode 121, can mitigate the thickness change at the end 122e of the second electrode 122, allowing the stepped structure at the end 122e to transition smoothly. Therefore, after the electrode assembly 120 expands and compresses the sidewall 109 of the housing 200, the stress generated by the thickness change at the end 122e of the second electrode 122 is reduced, thereby alleviating the stress (such as shear stress) experienced by the electrode assembly 120 within the inner ring of the end 122e of the second electrode 122. Thus, it reduces quality problems such as lithium plating, electrode deformation, and even electrode breakage caused by localized stress concentration, improving battery performance and lifespan.

[0061] In embodiments where the secondary battery is a cylindrical battery, the group margin of a cylindrical battery can be as high as 97% to 98%, which is much higher than that of other types of secondary batteries (such as prismatic batteries). Therefore, the outermost negative electrode of a cylindrical battery is more prone to electrode breakage at the end of the cycle. By setting the aforementioned insulating strip 400 in the cylindrical battery, in addition to mitigating the lithium plating problem caused by local stress concentration, the risk of electrode breakage caused by local stress concentration is also effectively reduced.

[0062] In addition, in embodiments where the secondary battery is a cylindrical battery, the positive electrode (such as the first electrode 121) includes a positive electrode active material, which may include a lithium-containing nickel-cobalt-manganese composite oxide. Because cylindrical batteries aim for maximum energy density, the spacing between the first electrode 121 and the second electrode 122 is very small. When the positive electrode material generally includes a ternary material containing lithium and nickel-cobalt-manganese, the stress will be significant during battery expansion. Therefore, for cylindrical batteries with the aforementioned positive electrode material, it is necessary to provide an insulating strip 400 to alleviate the problem of localized stress concentration. In some embodiments, the negative electrode (such as the second electrode 122) includes a negative electrode active material, which includes a silicon-based material. The silicon-based material may include, for example, silicon-carbon materials, silicon-oxygen materials, etc. During battery use, the expansion and stress generated by the silicon-based material will also be significant. Therefore, for cylindrical batteries with silicon-based negative electrode materials, it is also necessary to provide an insulating strip 400 to alleviate the problem of localized stress concentration.

[0063] In some embodiments, the insulating tape 400 can be an insulating adhesive tape and can be fixedly bonded to the surface of the end 122e of the second electrode 122. In embodiments where the insulating tape 400 is an insulating adhesive tape, the insulating tape may include a substrate and an adhesive layer, and the substrate material may be PET. In some embodiments, the thickness of the insulating tape 400 is d, the thickness of the first electrode 121 is D, and the value of d / D can range from 0.0625 to 0.875 (0.0625≤d / D≤0.875). In some embodiments, the thickness d can range from 20μm to 70μm, preferably 30μm. The thickness D can range from 80μm to 320μm. By configuring 0.0625≤d / D, it can be ensured that the thickness of the insulating tape 400 can provide sufficient support within the preset area Sp. Furthermore, by configuring d / D≤0.875, it can be avoided that during battery use, the electrode expands, causing stress concentration at the insulating tape 400, resulting in indentations on the electrode and a potential risk of lithium plating.

[0064] The insulating tape 400 is fixed to the side of the second electrode 122 facing the winding center hole 120c, that is, the insulating tape 400 contacts the surface 122a of the second electrode 122 facing the winding center hole 120c. Since this surface 122a faces the inner layers of the electrode sheets at the end 122e of the second electrode 122, placing the insulating tape 400 on this surface 122a is more beneficial in reducing stress on the inner layer electrode sheets. In addition, the insulating tape 400 is placed on the surface 122a that extends beyond the end 121e of the first electrode 121, so the portion of the surface 122a covered by the insulating tape 400 does not face the first electrode 121, and placing the insulating tape 400 at this location will not affect the battery performance.

[0065] More specifically, along the winding direction D, the insulating tape 400 has a starting end 400s and a ending end 400e. The starting end 400s of the insulating tape 400 is located within a preset region Sp, and the ending end 400e of the insulating tape extends beyond the preset region Sp, that is, the ending end 400e of the insulating tape 400 extends beyond the ending end 122e of the second electrode 122, in order to mitigate the thickness change at the ending end 122e of the second electrode 122. The starting end 400s of the insulating tape 400 can be located between the ending end 121e of the first electrode 121 and the ending end 122e of the second electrode 122, which makes it easier to set the insulating tape 400 during battery production. In embodiments where the insulating tape 400 is an insulating adhesive tape, the insulating tape 400 can be adhered to the ending end 122e of the second electrode 122.

[0066] Along the winding direction D, the length of the tail section 122p is L, meaning the length by which the end 122e of the second electrode 122 extends beyond the end 121e of the first electrode 121 is L, and the distance between the starting end 400s of the insulating tape 400 and the ending end 121e of the first electrode 121 is L1. In some embodiments, L > L1 ≥ 3 mm. If L1 is less than 3 mm, the insulating tape 400 will cover too much area of ​​the active material layer of the second electrode 122, which may lead to lithium plating.

[0067] The length of the insulating tape 400 along the height direction Z can be greater than the width of the active material layer of the second electrode 122 along the height direction Z, so that the upper end of the insulating tape 400 along the height direction Z extends beyond the upper end of the active material layer of the second electrode 122, and the lower end of the insulating tape 400 along the height direction Z extends beyond the lower end of the active material layer of the second electrode 122. This ensures that the insulating tape 400 can mitigate the thickness change at the end 122e of the second electrode 122 throughout the entire height direction Z of the active material layer of the second electrode 122.

[0068] In some embodiments, the thickness of the insulating tape 400 is greater than 20 micrometers. If the thickness of the insulating tape 400 is less than 20 micrometers, it cannot effectively mitigate the thickness change at the termination end 122e to reduce stress. In embodiments where the insulating tape 400 is an insulating adhesive tape, the insulating tape 400 may include a substrate layer and an adhesive layer stacked in the thickness direction of the insulating tape 400, wherein the adhesive layer can be used to bond to the termination end 122e of the second electrode 122. The material of the substrate layer is one of silicone, PP, PE, PET, and PI (polyimide).

[0069] Figure 5A This is a schematic diagram of a pad disposed at the end of the first electrode sheet according to an embodiment of this application. (In conjunction with...) Figure 4A and Figure 5AAs shown, the spacer 450 is disposed within the preset area Sp, and the spacer 450 is connected to the end 121e of the first electrode 121. The thickness of the spacer 450 is not greater than the thickness of the first electrode 121. Figure 5A In the embodiment shown, by providing a pad 450 (which can be called an insulating element) connected to the termination end 121e within the preset region Sp, the thickness change at the termination end 122e of the second electrode 122 can be mitigated, allowing the stepped structure at the termination end 122e to transition smoothly. Therefore, after the electrode assembly 120 expands and compresses the sidewall 109 of the housing 200, the stress generated by the thickness change at the termination end 122e of the second electrode 122 is reduced, thereby alleviating the stress (such as shear stress) experienced by the electrode assembly 120 within the inner ring of the termination end 122e of the second electrode 122. Thus, quality problems such as lithium plating, electrode deformation, and even electrode breakage caused by localized stress concentration are mitigated, improving battery performance and lifespan.

[0070] In embodiments where the secondary battery is a cylindrical battery, by providing a pad 450 in the cylindrical battery, the lithium plating problem caused by local stress concentration is mitigated, and the risk of cylindrical battery electrode breakage due to local stress concentration is effectively reduced. Furthermore, as mentioned above, it is also necessary to provide a pad 450 to mitigate the problem of local stress concentration for cylindrical battery cathode materials including ternary materials containing lithium (nickel-cobalt-manganese) and / or anode materials including silicon-based materials.

[0071] Figure 5B This is a partially enlarged schematic diagram showing a pad being provided at the end of the first electrode according to some embodiments. (Reference) Figure 5B As shown, the pad 450 can be fixed to the end 121e of the first electrode 121 by the insulating tape 405, such that the pad 450 is arranged after the end 121e of the first electrode 121 along the winding direction D. The insulating tape 405 can be adhesive tape, and the insulating tape 405 can be bonded to the side surface 121a of the first electrode 121 facing away from the winding center hole of the electrode assembly 120.

[0072] In this embodiment, the pad 450 may be adjacent to the terminal end 121e of the first electrode 121. In some embodiments, the thickness of the end portion of the pad 450, at least away from the terminal end 122e, gradually decreases along the winding direction D. In this embodiment, the pad 450 has a right-angled trapezoidal cross-sectional shape, and the thickness of the pad 450 gradually decreases along the winding direction D to mitigate the thickness change at the terminal end 122e of the second electrode 122. In some embodiments, the pad 450 may be made of a polymer material resistant to electrolyte corrosion, such as PP.

[0073] In some embodiments, the maximum thickness of the pad 450 is not greater than the maximum thickness of the first electrode 121. In some embodiments, the ratio of the length of the pad 450 along the winding direction D to the height of the pad 450 along the radial direction of the electrode assembly can be between 2 and 5. A larger pad length is beneficial for alleviating stress concentration, but excessive length may lead to problems such as difficulty in bending. Setting the aspect ratio of the pad 450 between 2 and 5 can alleviate the problem of stress concentration and also overcome the problem of difficulty in bending.

[0074] Figure 5C This is a schematic diagram of an insulating strip and pad disposed at the end of the first electrode sheet according to another embodiment of this application. Figure 5B The difference in the illustrated embodiment is that the pad 450 has a right-angled triangular cross-sectional shape. In this embodiment, to prevent the tip of the triangular pad 450 from piercing the diaphragm and electrode, the tip of the triangular pad 450 can be rounded to avoid sharp corners and burrs. Alternatively, tape can be used to wrap the tip of the triangular pad 450 to avoid sharp corners and burrs. In this embodiment, the aspect ratio of the pad 450 can be between 2 and 5.

[0075] In other embodiments, the pad 450 may have any other suitable shape, such as a regular shape, an irregular shape, or a combination thereof, as long as it can mitigate the thickness variation at the end 122e of the second electrode 122.

[0076] The above describes the embodiments of this application with the first electrode as the positive electrode and the second electrode as the negative electrode. However, it should be understood that in other embodiments, the first electrode can be the negative electrode and the second electrode can be the positive electrode.

[0077] See Figure 6This application also provides an electronic device 1000. For ease of explanation, the following embodiments use a vehicle as an example. A battery pack 1002 is installed inside the vehicle. The battery pack 1002 can be located at the bottom, front, or rear of the vehicle body 1001. The battery pack 1002 can be used to power the vehicle; for example, it can serve as the vehicle's operating power source. The working part of the electronic device 1000 is electrically connected to the battery pack 1002 to obtain electrical power. The vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, but are not limited thereto. The working part is the vehicle body, and the battery pack 1002 is located at the bottom of the vehicle body, providing electrical power for the vehicle's movement or the operation of its internal electrical components. However, in other embodiments, the electronic device 1000 can also be a mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working unit can obtain electrical energy from the battery pack 1002 and perform corresponding work, such as the fan blade rotation unit of a fan, the vacuuming unit of a vacuum cleaner, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application embodiment does not impose special limitations on the above-described electronic device 1000. The battery pack 1002 may include multiple secondary batteries, such as cylindrical batteries.

[0078] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A secondary battery characterized by comprising: The secondary battery comprises: a housing; an electrode assembly arranged in the housing, a first tab, a first separator, a second tab and a second separator being sequentially stacked and wound to form the electrode assembly, in a winding direction of the electrode assembly, a tail end of the second tab exceeding a tail end of the first tab, the second tab comprising a tail section exceeding the tail end of the first tab, a space between the tail section on a side facing a winding center hole of the electrode assembly and the second tab of an adjacent inner ring defining a preset area; an insulating member, at least a portion of the insulating member being fixed in the preset area along a height direction of the electrode assembly, a thickness of the insulating member being not greater than a thickness of the first tab.

2. The secondary battery according to claim 1, wherein the insulating member is an insulating tape, the insulating tape being connected to the side of the tail section facing the winding center hole.

3. The secondary battery according to claim 2, wherein in the winding direction, a starting end of the insulating tape is located in the preset area, and a tail end of the insulating tape exceeds the preset area.

4. The secondary battery according to claim 3, wherein a length of the tail section of the second tab in the winding direction is L, and a distance between the starting end of the insulating tape and the tail end of the first tab is L1, wherein L > L1 ≥ 3 mm.

5. The secondary battery according to claim 2, wherein the insulating tape comprises a base material and a glue layer, a material of the base material is PET, a thickness of the insulating tape is d, and a thickness of the first tab is D, a value of d / D is in a range of 0.0625-0.

875.

6. The secondary battery according to claim 2, wherein the second tab comprises a current collector and an active material layer arranged on a part of a surface of the current collector, and opposite ends of the insulating tape along the height direction both exceed opposite ends of the active material layer.

7. The secondary battery according to claim 1, wherein the insulating member is a pad, the pad being connected to the tail end of the first tab, the pad comprises a terminal part away from the tail end of the first tab, and at least the terminal part of the pad decreases in thickness along the winding direction.

8. The secondary battery according to claim 1, wherein the first tab is a positive tab, the positive tab comprising a positive active material, the positive active material comprising a lithium-containing nickel-cobalt-manganese composite oxide, the second tab is a negative tab, the negative tab comprising a negative active material, the negative active material comprising a silicon-based material, the secondary battery is a cylindrical battery, and the insulating member is used to reduce stress on the electrode assembly from the tail end of the second tab after the electrode assembly expands to press the housing.

9. A battery pack characterized by comprising: The secondary battery according to any one of claims 1-8.

10. An electronic device, comprising: The battery pack according to claim 9.

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