Secondary battery, battery pack, and electronic device

Abstract

The present application provides a secondary battery, a battery pack and an electronic device, the secondary battery comprising: a housing for defining an accommodating cavity; the cover plate covers the opening of the shell so as to seal the accommodating cavity; the electrode assembly is located in the containing cavity, the electrode assembly comprises a first pole piece, a second pole piece and a diaphragm between the first pole piece and the second pole piece, and in the winding direction of the electrode assembly, the first pole piece comprises a starting section, a middle section and an ending section which are sequentially connected; the starting section and the ending section are respectively spaced from the starting end and the ending end of the first tab in a preset distance, and the first insulating tape at least partially covers the first active material layer of the starting section and covers the area of the first active material layer at the starting end in the width direction; and the second insulating tape at least partially covers the first active material layer at the ending section and covers the area of the first active material layer at the ending end in the width direction. According to the technical scheme, at least the self-discharge risk of the secondary battery can be reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of battery, more specifically, a secondary battery, battery pack and electronic device. BACKGROUND

[0002] In the field of new energy power battery, the application of secondary battery is more and more widely, such as the secondary battery (for example, lithium ion battery) can be applied to the car, energy storage, mobile phone, tablet computer, wearable device, mobile power supply, electronic cigarette, digital product, electric tool, power device, energy storage device and other electronic devices. One of the secondary battery is cylindrical battery, which includes a shell and an electrode assembly, the electrode assembly includes a positive electrode sheet, a first separator, a negative electrode sheet and a second separator, which are stacked in sequence and then wound into an electrode assembly, and then packaged in the shell. However, the existing secondary battery still has the risk of high temperature self-discharge. SUMMARY

[0003] In view of the problems in the related art, the purpose of the utility model is to provide a secondary battery, battery pack and electronic device to at least reduce the risk of battery self-discharge.

[0004] To achieve the above purpose, the embodiment of the present application provides a secondary battery, which comprises: a shell for defining a receiving cavity, and the shell has an opening; a cover plate covering the opening of the shell to cover the receiving cavity; an electrode assembly located in the receiving cavity, the electrode assembly comprising a first electrode sheet, a second electrode sheet and a separator located between the first electrode sheet and the second electrode sheet, which are stacked in sequence and then wound into an electrode assembly, the first electrode sheet comprising a first current collector, the coating area of the first current collector being covered by a first active material layer along the two opposite surfaces in the thickness direction, the first current collector not covered by the first active material layer being a first tab of the first electrode sheet, the first electrode sheet comprising a starting section, an intermediate section and an ending section connected in sequence in the winding direction of the electrode assembly, the starting section being 1 / 10-1 / 4 of the overall length of the first active material layer from the starting end of the first electrode sheet in the winding direction, and the starting section being preset from the starting end of the first tab, the ending section being 1 / 10-1 / 4 of the overall length of the first active material layer from the ending end of the first electrode sheet in the reverse direction of the winding direction, and the ending section being preset from the starting end of the first tab, wherein the direction from the coating area to the first tab is the width direction of the first electrode sheet; a first insulating tape at least partially covering the first active material layer of the starting section and covering the area of the first active material layer at the starting end in the width direction; a second insulating tape at least partially covering the first active material layer of the ending section and covering the area of the first active material layer at the ending end in the width direction.

[0005] In some embodiments, the first insulating tape is arranged on the opposite sides of the first electrode sheet in the thickness direction thereof, and the second insulating tape is arranged on the opposite sides of the first electrode sheet in the thickness direction thereof.

[0006] In some embodiments, the maximum length of the second insulating tape is less than the maximum length of the first insulating tape along the winding direction.

[0007] In some embodiments, the maximum length L1 of the first insulating tape along the winding direction satisfies: 3mm≤L1≤π×n1×d1, where n1 is a constant between 0.5 and 2, and d1 is the diameter of the center hole of the electrode assembly.

[0008] In some embodiments, the maximum length L2 of the second insulating strip along the winding direction satisfies: 3mm≤L2≤π×d2, where d2 is the inner diameter of the shell.

[0009] In some embodiments, the maximum width of at least one of the first insulating strip and the second insulating strip along the height direction of the electrode assembly ranges from h0 to h0+5mm, where h0 is the maximum width of the first active material layer along the height direction.

[0010] In some embodiments, the first electrode is a positive electrode and the second electrode is a negative electrode. In the winding direction, the end of the second electrode extends beyond the end of the first electrode, and in the opposite direction of the winding direction, the beginning of the second electrode extends beyond the beginning of the first electrode.

[0011] In some embodiments, the secondary battery is a cylindrical battery.

[0012] Embodiments of this application also provide a battery pack, which includes any of the above-described secondary batteries.

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

[0014] The above-mentioned technical solution of this application, by setting a first insulating strip and a second insulating strip at the starting and ending sections of the first electrode sheet respectively, can protect the starting and ending areas of the first electrode sheet, isolate the self-discharge path formed by the deposited metal piercing the separator, prevent the formation of the internal electronic path of the battery, and reduce the risk of self-discharge of the secondary battery without changing the original battery shell material and battery chemical system. Attached Figure Description

[0015] 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.

[0016] Figure 1A perspective view of a secondary battery according to an embodiment of this application is shown.

[0017] Figure 2 A cross-sectional view of a secondary battery according to an embodiment of this application is shown.

[0018] Figure 3 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.

[0019] Figure 4 This is a cross-sectional schematic diagram of the first electrode sheet of an electrode assembly according to some embodiments in the thickness direction.

[0020] Figure 5 The planar schematic diagrams of the first electrode in its unfolded state are shown respectively.

[0021] Figure 6A and Figure 6B A planar schematic diagram of the first and second surfaces of a first electrode sheet covered by an insulating strip, in its unfolded state, is shown according to some embodiments.

[0022] Figure 7 A schematic diagram showing a comparison of storage tests between the secondary battery provided in this application and secondary batteries in the prior art is illustrated.

[0023] Figure 8 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle. Detailed Implementation

[0024] To better understand the spirit of the embodiments of this application, the following description is based on some preferred embodiments of this application.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The casing of existing rechargeable batteries is typically made of metal. During battery use, the metal in the casing oxidizes and deposits on the negative electrode surface, then reduces. This deposition often occurs at the beginning and end of the electrode winding, causing metal buildup. This deposited metal can easily puncture the separator, leading to internal short circuits and self-discharge. For example, current 46-series cylindrical batteries use nickel-plated SPCC or SPCE steel casings for encapsulating electrode components. During the use of cylindrical batteries, such as during high-temperature storage, the electrolyte decomposition byproduct HF corrodes the steel casing. The Ni and Fe on the steel casing surface oxidize and deposit on the negative electrode surface, leading to self-discharge. Existing battery designs can reduce electrolyte corrosion of the casing through chemical system and process optimization, but a high risk of self-discharge still exists.

[0030] An embodiment of this application provides a secondary battery. Figure 1 A perspective view of a secondary battery 100 according to an embodiment of this application is shown. Figure 2 A cross-sectional view of a secondary battery 100 according to an embodiment of this application is shown. In the following description, a cylindrical battery is used as an example to illustrate the embodiments of this application.

[0031] Combination Figures 1-2As 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 housing 200 defines a receiving cavity in which the electrode assembly 120 is located. 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).

[0032] 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 central hole 120c, and the axis Lc can be the axis of the central hole 120c. The wound electrode assembly 120 can have a central 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 first tab 125 (such as a positive tab). 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 second tab 124 (such as a negative tab).

[0033] 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. The 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 Z direction 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 axial direction of the electrode assembly 120, i.e., the height direction of the secondary battery, which is parallel to the Z direction. The end of the peripheral sidewall 109 of the housing 200 on the opening 205 side can be configured as a rolled edge 32, which extends radially inward into the housing 200, perpendicular to the Z direction. The rolled edge 32 and the groove 113 are spaced apart along the Z direction, and the groove 113 and the rolled edge 32 can together clamp the cover plate 220. The cover plate 220 can be electrically insulated from the housing 200.

[0034] 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.

[0035] The second tab 124 of the electrode assembly 120 faces the opening 205 and can be electrically connected to the housing 200 via a negative current collector 201 located between the cover plate 220 and the electrode assembly 120, thereby making the housing 200 negatively charged. The negative current collector 201 can be welded to the housing 200 by laser welding. Specifically, the welding position of the negative current collector 201 to the housing 200 is located on the side of the groove 113 facing the electrode assembly 120.

[0036] The secondary battery 100 may further include a terminal post 160 that passes through and is insulated from the end wall 111. The terminal post 160 can be electrically connected to a first 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.

[0037] 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:

[0038] Winding: A winding structure formed by stacking and winding negative electrode sheet, separator and positive electrode sheet, wherein the uncoated portions of the negative current collector of negative electrode sheet and the positive current collector of positive electrode sheet are used as first tab 125 and second tab 124, and the first tab 125 and second tab 124 are bent radially along the electrode assembly 120.

[0039] 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 first electrode tab 125 and the second electrode tab 124, respectively.

[0040] 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.

[0041] Install pole 160.

[0042] 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.

[0043] 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 in the Z direction. 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.

[0044] Figure 3 This is a cross-sectional view of the electrode assembly 120 of a secondary 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 central hole 120c, the axis Lc of which extends in the Z direction (see...). Figure 3 ), Figure 3 The XY plane shown is a cross-section perpendicular to the axis Lc. The center hole 120c is located in... Figure 3 The cross-section shown can have a circular shape.

[0045] See Figure 3 The electrode assembly 120 may include a first electrode 121, a first separator 141, a second electrode 122, and a second separator 142. Furthermore, the secondary battery may also include an electrolyte, which may be located between the first electrode 121, the first separator 141, the second electrode 122, and the second separator 142.

[0046] The first electrode 121, the first diaphragm 141, the second electrode 122, and the second diaphragm 142 are sequentially stacked and wound along the winding direction D to form the electrode assembly 120. Specifically, the first electrode 121 is wound from its starting end 121s to its ending end 121e along the winding direction D, and the second electrode 122 is wound from its starting end 122s to its ending end 122e. The first diaphragm 141 and the second diaphragm 142 isolate the first electrode 121 from the second electrode 122.

[0047] In some embodiments, the first electrode 121 is a positive electrode, and the second electrode 122 is a negative electrode. By coating the positive electrode with a positive active material layer containing lithium ions, when the positive active material layer comes into contact with the electrolyte and the battery is charged, the lithium ions in the positive active material layer will move through the electrolyte to the negative active material layer and embed themselves in it. This process is the lithium ion activation process, which is also the battery charging process.

[0048] In the winding direction D, the end 122e of the second electrode 122 extends beyond the end 121e of the first electrode 121, allowing the second electrode 122 to cover the 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 readily inserted into the negative active material layer of the second electrode 122 (negative electrode), thus preventing lithium plating at the end of the negative electrode. For similar reasons, in the direction opposite to the winding direction D, the beginning end 122s of the second electrode 122 also extends beyond the beginning end 121s of the first electrode 121; that is, at the beginning of the winding of the electrode assembly 120, the second electrode 122 is wound a longer distance than the first electrode 121. Therefore, lithium ions detached from the positive active material layer of the first electrode 121 (positive electrode) can be successfully inserted into the negative active material layer of the second electrode 122 (negative electrode), thereby avoiding lithium plating at the beginning of the negative electrode.

[0049] Figure 4 This is a schematic cross-sectional view of the first electrode sheet of an electrode assembly according to some embodiments, in the thickness direction. (Reference) Figure 4 As shown, the first electrode 121 may include a first current collector 18 and a first active material layer 16. The first active material layer 16 covers a portion of the opposing surfaces of the first current collector 18 along its thickness direction. The first current collector 18 includes a coated area 181 and an uncoated area 182 connected to each other. The first active material layer 16 is not disposed on the opposing surfaces of the uncoated areas 182. The direction Z from the coated area 181 to the uncoated area 182 is the width direction of the first electrode 121, and the width direction of the first electrode 121 is parallel to the height direction of the secondary battery. The uncoated area 182 can be used as a first tab 125 (such as a positive tab).

[0050] In some embodiments, the first electrode 121 is a positive electrode, and the second electrode 122 is a negative electrode. The first current collector 18 is a positive current collector, and the first active material layer 16 is a positive active material layer. 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 a positive active material, such as lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. For high-nickel ternary lithium batteries, the positive active material can be a ternary material composed of nickel, cobalt, and manganese (or aluminum), wherein the nickel content is usually relatively high, generally above 60%. Similarly, the negative electrode 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. The material of the negative current collector can be copper, and the negative active material layer can include a negative active material, such as carbon or silicon.

[0051] The first electrode 121 has a first surface 1211 and a second surface 1212 opposite each other in its thickness direction. Figure 5 The diagrams show the first pole piece 121 in its unfolded state. (Reference) Figure 5 As shown, the first electrode 121 extends from its starting end 121s to its ending end 121e in the length direction of the first electrode 121, and can correspond to its winding direction D in the electrode assembly. The width direction of the first electrode 121, perpendicular to its length direction, can correspond to direction Z. The starting end 125a of the first tab 125 is adjacent to the starting end 121s of the first electrode 121, and the ending end 125b of the first tab 125 is adjacent to the ending end 121e of the first electrode 121.

[0052] In the winding direction D, the first electrode 121 includes a starting segment Sa, an intermediate segment Sm, and a ending segment Sb connected in sequence. The starting segment Sa is connected to the starting end 121s of the first electrode 121, and the starting segment Sa is at a predetermined distance from the starting end 125a of the first electrode tab 125. Specifically, the starting segment Sa is located at 1 / 10 to 1 / 4 of the total length from the starting end 121s of the first electrode 121 to the first active material layer 16 along the winding direction D. The length of the starting segment Sa along the winding direction D can be 1 / 10 to 1 / 4 of the total length of the first active material layer 16. The ending segment Sb is connected to the ending end 121e of the first electrode 121, and the ending segment Sb is at a predetermined distance from the ending end 125b of the first electrode tab 125. Specifically, the ending segment Sb is located at 1 / 10 to 1 / 4 of the total length from the ending end 121e of the first electrode 121 to the first active material layer 16 in the opposite direction of the winding direction D. The length of the final segment Sb along the winding direction D can be 1 / 10 to 1 / 4 of the overall length of the first active material layer 16. In some embodiments, the starting segment Sa is the first two turns of the first electrode 121 wound along the winding direction D, and the length of the starting segment Sa can be equal to π × the diameter of the central hole 120c × 2. In some embodiments, the length of the starting segment Sa is at least about 1 cm. In some embodiments, the final segment Sb is the last turn of the first electrode 121 wound along the winding direction D, and the length of the final segment Sb can be equal to π × the outer diameter of the electrode assembly 120.

[0053] Figure 6A and Figure 6B Planar schematic diagrams of a first surface 1211 and a second surface 1212 of a first electrode sheet covered by an insulating tape, in an unfolded state, are shown according to some embodiments. (Combined with...) Figure 5 and Figure 6A and Figure 6B As shown, the first insulating tape 191 can at least partially cover the first active material layer 16 of the initial segment Sa. In Figure 6A and Figure 6B In the illustrated embodiment, the first insulating tape 191 completely covers the first active material layer 16 of the starting segment Sa. In some embodiments, the first insulating tape 191 may cover the first active material layer 16 in the starting segment Sa of the first electrode 121 on at least one side in the thickness direction of the first electrode 121, and the coverage length may be 1 / 10 to 1 / 4 of the length of the first active material layer 16 along the winding direction D. The second insulating tape 193 may at least partially cover the first active material layer 16 of the ending segment Sb. Figure 6A and Figure 6BIn the illustrated embodiment, the second insulating tape 193 completely covers the first active material layer 16 of the terminal section Sb. In some embodiments, the second insulating tape 193 may cover the first active material layer 16 in the terminal section Sb of the first electrode 121 on at least one side in the thickness direction of the first electrode 121, and the coverage length may be 1 / 10 to 1 / 4 of the length of the first active material layer 16 along the winding direction D.

[0054] Furthermore, the first insulating tape 191 covers the region of the first active material layer 16 at the starting end 121s in the Z direction (i.e., the width direction of the first electrode 121), that is, it completely covers the starting end of the first active material layer 16 in the electrode width direction. The second insulating tape 193 covers the region of the first active material layer 16 at the ending end 121e in the Z direction, that is, it completely covers the ending end of the first active material layer 16 in the electrode width direction. In some embodiments, the opposite ends of the first insulating tape 191 and the second insulating tape 193 along the Z direction may extend beyond the opposite ends of the first active material layer 16 (e.g., ...). Figure 6A and Figure 6B (As shown). In this way, the overall width range of both the starting segment Sa and the ending segment Sb can be protected by the first insulating tape 191 and the second insulating tape 193. Since the starting segment Sa and the ending segment Sb are spaced apart from the first electrode tab 125 in the winding direction D, the first insulating tape 191 and the second insulating tape 193 will not cover any part of the first electrode tab 125 to avoid affecting the first electrode tab.

[0055] In some embodiments, the first insulating tape 191 and the second insulating tape 193 may be insulating tape. In other embodiments, the first insulating tape 191 and the second insulating tape 193 may be other types of insulating tape.

[0056] By setting a first insulating strip 191 and a second insulating strip 193 on the starting section Sa and the ending section Sb respectively, and by having the first insulating strip 191 and the second insulating strip 193 cover the width range of the first active material layer 16 in the electrode width direction at the starting end 121s and the ending end 121e respectively, protection can be formed in the starting end 121s and the ending end 121e area of ​​the first electrode 121, isolating the self-discharge path formed by the deposited metal piercing the separator and preventing the formation of internal electronic pathways in the battery, thereby reducing the risk of self-discharge of the secondary battery without changing the original battery casing material and battery chemical system. In addition, setting the starting section Sa to be 1 / 10 to 1 / 4 of the overall length from the starting end 121s to the first active material layer 16 and setting the ending section Sb to be 1 / 10 to 1 / 4 of the overall length from the ending end 121e to the first active material layer 16, it is convenient to adhere the first insulating strip 191 and the second insulating strip 193 in the starting section Sa and the ending section Sb. If the areas of the starting segment Sa and the ending segment are smaller than or below the above range, the process window is too small, and wrinkles are easily generated during the application of the first insulating tape 191 and the second insulating tape 193.

[0057] In embodiments where the secondary battery is a cylindrical battery, because cylindrical batteries have high energy density and a small gap between the outer ring of the casing and the electrode assembly, the electrode assembly of a cylindrical battery experiences high expansion stress during battery charging and discharging, making it more prone to high-temperature self-discharge risk. By providing the aforementioned first insulating strip 191 and second insulating strip 193 in the cylindrical battery, protection can be formed at the starting end 121s and ending end 121e regions of the first electrode 121 of the cylindrical battery, isolating the self-discharge path formed by the deposited metal piercing the separator and preventing the formation of internal electronic pathways in the cylindrical battery, thereby reducing the self-discharge risk of the cylindrical battery without changing the original battery casing material and battery chemical system.

[0058] In some embodiments, a first insulating strip 191 is disposed on a first surface 1211 and a second surface 1212 on opposite sides of the first electrode 121 along its thickness direction. The first insulating strip 191 covers the first active material layer 16 in the starting segment Sa on both the first surface 1211 and the second surface 1212. In some embodiments, a second insulating strip 193 is disposed on a first surface 1211 and a second surface 1212 on opposite sides of the first electrode 121 along its thickness direction. The second insulating strip 193 covers the first active material layer 16 in the ending segment Sb on both the first surface 1211 and the second surface 1212. By disposing the first insulating strip 191 and the second insulating strip 193 on both the first surface 1211 and the second surface 1212, the starting segment Sa and the ending segment Sb at the starting end 121s and the ending end 121e of the first electrode 121 can be protected more effectively, reducing the risk of self-discharge of the secondary battery. In addition, the first insulating tape 191 on the first surface 1211 can be bonded to the second insulating tape 193 on the second surface 1212, which can solve the problem of insufficient adhesion when the insulating tape is bonded to the active material layer.

[0059] In some embodiments, a first insulating strip 191 may extend from the first surface 1211 through the starting end 121s to the second surface 1212, and in the Z direction at least across the width of the first electrode 121, such that the first insulating strip 191 does not expose any part of the starting segment Sa. A second insulating strip 193 may extend from the first surface 1211 through the ending end 121e to the second surface 1212, and in the Z direction at least across the width of the first electrode 121, such that the second insulating strip 193 does not expose any part of the ending segment Sb.

[0060] Specifically, the first insulating tape 191 has an outer edge 191s1 on the first surface 1211 that is furthest from the starting end 121s, and an outer edge 191s2 on the second surface 1212 that is furthest from the starting end 121s. Both outer edges 191s and 191s2 are located between the starting end 121s and the starting end 125a of the first tab 125. In this way, the first insulating tape 191 does not extend into the area of ​​the first tab 125, thus avoiding interference with the first tab area. Similarly, the second insulating tape 193 has an outer edge 193s1 on the first surface 1211 that is furthest from the ending end 121e, and an outer edge 193s2 on the second surface 1212 that is furthest from the ending end 121e. Both outer edges 193s1 and 193s2 are located between the ending end 121e and the ending end 125b of the first tab 125. In this way, the second insulating strip 193 will not extend into the area of ​​the first tab 125, thus avoiding interference with the area of ​​the first tab.

[0061] In some embodiments, the maximum length of the first insulating tape 191 is L1. The maximum length L1 is the longer of the length of the first insulating tape 191 on the first surface 1211 and the length on the second surface 1212. In some embodiments, the length of the first insulating tape 191 on the first surface 1211 is the same as the length of the first insulating tape 191 on the second surface 1212 (within the range of process variations). Figure 6A and Figure 6B The length of the first insulating strip 191 on both the first surface 1211 and the second surface 1212 is shown as L1. The maximum length L1 of the first insulating strip 191 can be the same as the length of the starting segment Sa in the winding direction D. In some embodiments, the maximum length L1 can be 1 / 10 to 1 / 4 of the overall length of the first active material layer 16 along the winding direction D.

[0062] Furthermore, the maximum length of the second insulating tape 193 is L2. The maximum length L2 is the longer of the length of the second insulating tape 193 on the first surface 1211 and the length on the second surface 1212. In some embodiments, the length of the second insulating tape 193 on the first surface 1211 is the same as the length of the second insulating tape 193 on the second surface 1212 (within the range of process variations). Figure 6A and Figure 6B The length of the second insulating strip 193 on both the first surface 1211 and the second surface 1212 is shown as L2. The maximum length L2 of the second insulating strip 193 can be the same as the length of the tail section Sb in the winding direction D. In some embodiments, the maximum length L2 can be 1 / 10 to 1 / 4 of the overall length of the first active material layer 16 along the winding direction D.

[0063] In some embodiments, the maximum length L1 of the first insulating tape 191 is less than the maximum length L2 of the second insulating tape 193. Typically, the distance between the starting end 121s of the first electrode 121 and the starting end 125a of the first tab 125 along the winding direction is short, so the first insulating tape 191 can have a smaller maximum length L1, which can provide good protection for the area of ​​the starting end 121s.

[0064] In some embodiments, the maximum length L1 of the first insulating tape 191 satisfies: 3mm ≤ L1 ≤ π × n1 × d1, where n1 is a constant between 0.5 and 2, and d1 is the diameter of the center hole of the electrode assembly. It should be understood that d1 can be equal to the diameter of the winding needle used to wind the electrode assembly. In other words, L1 is greater than or equal to 3mm and less than or equal to n1 times the circumference of the winding needle. In some embodiments, 3mm ≤ d1 ≤ 9mm. In some embodiments, 4mm ≤ d1 ≤ 8mm. This length range of the first insulating tape 191 effectively avoids the formation of a self-discharge path while also avoiding any impact on battery performance.

[0065] In some embodiments, the maximum length L2 of the second insulating strip 193 satisfies: 3mm ≤ L2 ≤ π × n2 × d2, where d2 is the inner diameter of the shell. In some embodiments, n2 is any applicable constant used to indicate that L2 is less than or equal to n2 times the inner wall circumference of the shell. Preferably, n2 equals 1, 3mm ≤ L2 ≤ π × n2 × d2, that is, L2 is less than or equal to the inner wall circumference of the shell. The inner diameter d2 of the shell can be determined by the following formula: d2 = d4 - 2 × d3, where d4 is the outer diameter of the shell and d3 is the thickness of the shell. Such a length range of the second insulating strip 193 can prevent interference with the first tab region of the first electrode plate.

[0066] The maximum width of the first insulating strip 191 and the maximum width of the second insulating strip 193 both range from h0 to h0+5mm. Here, h0 is the maximum width of the first active material layer 16 of the first electrode 121 along the Z direction. In some embodiments, the maximum width of the first insulating strip 191 is the same as the maximum width of the second insulating strip 193. In this embodiment, the maximum width of both the first insulating strip 191 and the second insulating strip 193 is shown as h1, where h0≤h1≤h0+5mm. In some embodiments, the width h0 can be determined by the following formula: h2-8mm≤h0≤h2-20mm, where h2 is the height of the secondary battery; for example, for a 4680 cylindrical battery, h2=80mm. In other embodiments, the maximum width of the first insulating strip 191 and the maximum width of the second insulating strip 193 may be different. The aforementioned width range of the first insulating strip 191 and the second insulating strip 193 can limit the maximum width of the first insulating strip 191 and the second insulating strip 193 from being greater than the width h0 of the first electrode 121 by no more than 5 mm. This can effectively protect the starting end 121s and the ending end 121e while avoiding any impact on battery performance.

[0067] Figure 7 A schematic diagram comparing the storage test results of the secondary battery provided in this application with those of secondary batteries in the prior art is shown. See also... Figure 7 As shown, under a high temperature of 55°C, storage tests were conducted on the secondary battery provided in this application (including the aforementioned first insulating strip 191 and second insulating strip 193) and a secondary battery in the prior art (excluding the aforementioned first insulating strip 191 and second insulating strip 193) at 100% SOC (State of Charge). In this diagram, line C1 corresponds to the secondary battery of this application, and lines C2 and C3 correspond to the secondary batteries of the prior art. Figure 7 It is evident that, compared to existing secondary batteries, the technical solution of this application significantly improves the capacity retention rate during high-temperature storage testing by avoiding battery self-discharge.

[0068] See Figure 8 This 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 of the above-described secondary batteries, such as cylindrical batteries.

[0069] 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 in that, include: A housing for defining a receiving cavity, and the housing having an opening; A cover plate that closes to the opening of the housing to seal the receiving cavity; An electrode assembly is located in the receiving cavity. The electrode assembly includes a first electrode, a second electrode, and a diaphragm located between the first electrode and the second electrode after being stacked and wound sequentially. The first electrode includes a first current collector. The two surfaces of the coating area of ​​the first current collector opposite to each other along its thickness direction are covered by a first active material layer. The first current collector not covered by the first active material layer is the first tab of the first electrode. In the winding direction of the electrode assembly, the first electrode includes a starting segment, a middle segment, and a closing segment connected sequentially. The starting segment is located at 1 / 10 to 1 / 4 of the total length of the first electrode from the starting end of the first electrode to the first active material layer along the winding direction, and the starting segment is at a predetermined distance from the starting end of the first tab. The closing segment is located at 1 / 10 to 1 / 4 of the total length of the first active material layer from the closing end of the first electrode in the opposite direction of the winding direction, and the closing segment is at a predetermined distance from the starting end of the first tab. The direction from the coating area to the first tab is the width direction of the first electrode. A first insulating tape at least partially covers the first active material layer of the starting segment and covers the region of the first active material layer at the starting end in the width direction. The second insulating tape at least partially covers the first active material layer of the terminal section, and covers the area of ​​the first active material layer at the terminal end in the width direction.

2. The secondary battery according to claim 1, characterized in that, The first insulating strip is disposed on opposite sides of the first electrode sheet along its thickness direction. The second insulating strip is disposed on opposite sides of the first electrode along its thickness direction.

3. The secondary battery according to claim 1, characterized in that, Along the winding direction, the maximum length of the second insulating tape is less than the maximum length of the first insulating tape.

4. The secondary battery according to claim 3, characterized in that, The maximum length L1 of the first insulating tape along the winding direction satisfies: 3mm≤L1≤π×n1×d1, where n1 is a constant between 0.5 and 2, and d1 is the diameter of the central hole of the electrode assembly.

5. The secondary battery according to claim 3, characterized in that, The maximum length L2 of the second insulating tape along the winding direction satisfies: 3mm≤L2≤π×d2, where d2 is the inner diameter of the shell.

6. The secondary battery according to claim 1, characterized in that, The maximum width of either the first insulating tape or the second insulating tape along the width direction ranges from h0 to h0+5mm, where h0 is the maximum width of the first active material layer along the width direction.

7. The secondary battery according to claim 1, characterized in that, The first electrode is the positive electrode, and the second electrode is the negative electrode. In the winding direction, the terminal end of the second electrode extends beyond the terminal end of the first electrode. In the opposite direction to the winding direction, the starting end of the second electrode extends beyond the starting end of the first electrode.

8. The secondary battery according to claim 1, characterized in that, The secondary battery is a cylindrical battery.

9. A battery pack, characterized in that, The secondary battery includes any one of claims 1 to 8.

10. An electronic device, characterized in that, Includes the battery pack as described in claim 9.

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