Secondary battery, battery pack and electronic device

Abstract

To provide a secondary battery, a battery pack, and an electronic device in which a positive electrode tab is less likely to be displaced after collapse in a press bending process.SOLUTION: The secondary battery includes a casing, an electrode assembly and a current collecting member. The electrode assembly is accommodated in the casing, the electrode assembly includes a winding structure formed by stacking and winding a positive electrode plate, a negative electrode plate and a separator, the positive electrode plate includes a positive electrode coating region, a positive electrode non-coating region and an insulation layer covering at least a boundary between the positive electrode coating region and the positive electrode non-coating region, and the positive electrode non-coating region extends outside the separator and is bent toward a winding axis to form a positive electrode non-coating region stacking zone. The current collecting member is welded to the positive electrode non-application region stacking zone. The insulating layer includes a first insulating layer facing the winding shaft and a second insulating layer away from the winding shaft, the first insulating layer and the second insulating layer both extend along the direction of the winding shaft to the positive electrode non-coating region stacking zone, and a height h1 of the first insulating layer is greater than a height h2 of the second insulating layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of batteries, and more particularly to a type of secondary battery, battery pack and electronic device. [Background technology]

[0002] As one of the most core components of new energy vehicles, lithium-ion batteries have advantages such as high energy density, long cycle life, safety and environmental friendliness, and are becoming the mainstream trend in the era of electrification. Lithium-ion batteries are divided into hard-case batteries, soft-pack batteries and cylindrical batteries in terms of their form, and among them, cylindrical batteries are attracting attention due to their advantages such as high volumetric energy density, simple structure, ease of assembly and ease of standardization.

[0003] A cylindrical battery cell is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet, and one end of the positive electrode sheet that is not coated with a positive active material is folded toward the center of the cylindrical battery to form a positive electrode non-coated region laminated area. A current collector is then pressed and welded to the positive electrode non-coated region laminated area. Because the positive electrode sheet is typically aluminum foil with a relatively high hardness, when the current collector and the positive electrode non-coated region laminated area are pressed together, the positive electrode non-coated region laminated area can collapse and shift during the press bending process. Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above-mentioned drawbacks of the prior art, the present invention provides a secondary battery for improving the technical problem of displacement after collapse of the positive electrode non-coated region lamination area during the press bending process. [Means for solving the problem]

[0005] To achieve the above and other related objectives, the present invention provides a secondary battery. The secondary battery includes a casing, an electrode assembly, and a current collecting member. The electrode assembly is housed in the casing, and the electrode assembly includes a wound structure formed by stacking and winding a positive electrode sheet, a negative electrode sheet, and a separator. The positive electrode sheet includes a positive electrode-coated region coated with a positive electrode active material layer and a positive electrode-uncoated region not coated with a positive electrode active material layer, and an insulating layer covering at least the boundary between the positive electrode-coated region and the positive electrode-uncoated region. The positive electrode-uncoated region extends outside the separator at one end of the electrode assembly in the winding axis direction and is folded toward the winding axis to form a positive electrode-uncoated region stacked area. The current collecting member at least partially covers the positive electrode-uncoated region stacked area and is welded to the positive electrode-uncoated region stacked area. The insulating layers include a first insulating layer disposed on a first side of the positive electrode sheet facing the winding axis and a second insulating layer disposed on a second side away from the winding axis, the first insulating layer and the second insulating layer both extending along the direction of the winding axis into the positive electrode non-coated region stacking area, and the height h1 of the first insulating layer along the direction of the winding axis is greater than the height h2 of the second insulating layer.

[0006] In the above technical solution, the insulating layer covers at least the boundary between the positive electrode coated region and the positive electrode uncoated region and extends to the folded portion of the positive electrode uncoated region stacked area. That is, the insulating layer at least partially covers the positive electrode uncoated region and can act as a support against the crimping force from the current collecting member when the positive electrode uncoated region stacked area is folded. Furthermore, the first insulating layer is located on the first side facing the winding axis, i.e., below the positive electrode uncoated region stacked area after folding, and can directly provide the positive electrode uncoated region stacked area with a counteracting force that resists the pressure from the current collecting member. Setting the height of the first insulating layer higher than the height of the second insulating layer further improves the support force for the positive electrode uncoated region stacked area, alleviating the problem of post-collapse slippage of the positive electrode uncoated region stacked area, improving the flatness of the welding surface of the positive electrode uncoated region stacked area, and improving the welding yield rate.

[0007] In one example of the secondary battery of the present invention, the difference between h1 and h2 is t, and 0.2 mm≦t≦1.5 mm.

[0008] In the above technical solution, the height difference t between the first insulating layer and the second insulating layer is in the range of 0.2 mm≦t≦1.5 mm, which ensures a safe distance between the first insulating layer and the non-positive electrode region lamination area and reduces the risk of the first insulating layer being crushed by the non-positive electrode region lamination area and causing powder to fall.

[0009] In one example of the secondary battery of the present invention, the radial dimension of the portion of the outermost tab that is shifted rearward from the outer periphery of the electrode assembly is a, and a≦1.5 mm. Here, the rearward shifted portion refers to the portion along the outermost radial direction of the electrode assembly between the base of the positive electrode non-coated region and the outermost positive electrode non-coated region.

[0010] In the above technical solution, the rearward-shifted portion is formed by bending the positive electrode non-coated region lamination area toward the winding axis and then crimping the lamination area after bending, and then bending the positive electrode non-coated region lamination area from its base toward the radially outward direction of the electrode assembly. Setting a value of a≦1.5 mm increases the annular width of the lamination number stability zone of the positive electrode non-coated region lamination area, which is suitable for welding, making welding easier. Furthermore, the slope of the slope formed by the rearward-shifted positive electrode non-coated region lamination area is reduced, thereby reducing the gap between the positive electrode non-coated region lamination area and the current collecting member, thereby improving the reliability and convenience of welding.

[0011] In one example of the secondary battery of the present invention, on a reference plane formed by the winding axis and any one of the diameter lines on the end surface of the electrode assembly, the outer periphery of the wound structure cuts n laps of the positive electrode non-coated region, and when the total thickness of the positive electrode sheet, separator, and negative electrode sheet is b, the ratio a / b <nである。

[0012] In the above technical solution, with the setting of a / b < n, it may accommodate the displaced part after the collapse of the non-coated positive electrode region lamination area where the tabless annular region is located at the outermost periphery in the winding structure, and by ensuring that the displaced part behind the non-coated positive electrode region lamination area does not exceed the outer periphery of the electrode assembly, the probability of affecting the accommodation of the electrode assembly in the casing can be reduced.

[0013] In an exemplary embodiment of the secondary battery of the present invention, from the outer periphery to the inner periphery of the electrode assembly, the non-coated positive electrode region lamination area sequentially includes a region with an increasing number of laminations, a region with a stable number of laminations, and a region with a decreasing number of laminations. The non-coated positive electrode region lamination area located in the region with a decreasing number of laminations extends in a direction away from the current collector member.

[0014] In the above technical solution, a concave slope may be formed at a position close to the winding axis of the electrode assembly. On the one hand, this slope serves to guide the electrolyte, and on the other hand, it prevents the upward warping of the non-coated positive electrode region lamination area located in the region with a decreasing number of laminations, and can improve the stability and convenience of the welding between the current collector member and the non-coated positive electrode region lamination area.

[0015] In an exemplary embodiment of the secondary battery of the present invention, the annular width of the non-coated positive electrode region lamination area is r, the annular width of the region with a stable number of laminations is c, and c / r ≥ 0.35.

[0016] In the above technical solution, the setting of c / r ≥ 0.35 is advantageous for ensuring the range of the region with a stable number of laminations, improving the reliability of welding, reducing the internal resistance, and improving the performance of the secondary battery.

[0017] In an exemplary embodiment of the secondary battery of the present invention, the insulating layer includes ceramic fillers.

[0018] In the above technical solution, on the premise of ensuring the insulation property, the ceramic fillers have relatively high hardness and can provide a more stable supporting force.

[0019] In an exemplary embodiment of the secondary battery of the present invention, the brightness of the first insulating layer is different from that of the second insulating layer.

[0020] In the above technical solution, by observing the difference in brightness between the first insulating layer and the second insulating layer, the front and back of the positive electrode sheet can be effectively distinguished, and the situation where the positive electrode sheet is placed upside down can be prevented. In addition, since the insulating layer is not involved in the chemical reaction, distinguishing the front and back of the positive electrode sheet by the insulating layer does not require additional marking, and the impact on the battery is relatively small.

[0021] The present invention further provides a battery pack, which includes any of the secondary batteries described above.

[0022] The present invention further provides an electronic device, which includes the battery pack described above. [Effects of the Invention]

[0023] In the secondary battery of the present invention, the insulating layer covers at least the boundary between the positive electrode coated region and the positive electrode uncoated region and extends to the folded portion of the positive electrode uncoated region. That is, the insulating layer at least partially covers the unfolded region of the positive electrode uncoated region, and can provide support against the crimping force from the current collecting member when the positive electrode uncoated region is folded. Furthermore, the first insulating layer is located on the first side facing the winding axis, i.e., below the positive electrode uncoated region after folding, and can directly provide the positive electrode uncoated region with a counteracting force that resists the pressure from the current collecting member. By setting the height of the first insulating layer higher than the height of the second insulating layer, the support force for the positive electrode uncoated region can be further improved, alleviating the problem of post-collapse displacement of the positive electrode uncoated region, improving the flatness of the welding surface of the positive electrode uncoated region, and increasing the rate of good welding results. [Brief explanation of the drawings]

[0024] In order to more clearly describe the embodiments of the present invention or the technical solutions in the prior art, the drawings necessary for use in the description of the embodiments or related art are briefly introduced below. Obviously, the drawings described below are only embodiments of the present application, and those skilled in the art can obtain other embodiments based on these drawings without expending creative efforts.

[0025] [Figure 1] 1 is a structural schematic diagram of an embodiment of a secondary battery of the present invention; [Figure 2] 1 is a structural schematic diagram of an electrode assembly in an embodiment of a secondary battery of the present invention; [Figure 3] 1 is a cross-sectional view of an electrode assembly in an embodiment of a secondary battery of the present invention. [Figure 4] FIG. 2 is a cross-sectional view of a single positive electrode sheet in an embodiment of the secondary battery of the present invention. [Figure 5] 3 is a structural schematic diagram of a positive electrode non-coated region lamination area in an embodiment of the secondary battery of the present invention. FIG. [Figure 6] 1 is a schematic diagram of an embodiment of a battery pack of the present invention. [Figure 7] 1 is a schematic diagram of an embodiment of an electronic device of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present invention will be described through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed herein. The present invention can be implemented or applied in further different specific embodiments, and the details of each item in this specification can be modified or changed in various ways based on different perspectives and applications without departing from the spirit of the present invention. It should be noted that the following examples and features in the examples can be combined with each other, where not inconsistent. It should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments and are not intended to limit the scope of protection of the present invention. In the following examples, test methods for which specific conditions are not noted generally follow general conditions or conditions recommended by each manufacturer.

[0027] When an example shows a range of values, it should be understood that the two endpoints of each range and any value between those two endpoints can be selected unless otherwise specified in the present invention. Unless otherwise defined, all technical and scientific terms used in the present invention are based on the understanding of well-known techniques by those skilled in the art and the description of the present invention, and the present invention can also be realized using any methods, devices, and materials well-known in the art that are similar or equivalent to the methods, devices, and materials in the examples of the present invention.

[0028] It should be noted that the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are used for the convenience of clarifying the description and do not limit the scope of the present invention. Any change or adjustment of their relative relationships should be considered within the scope of the present invention as long as there is no substantial change in the technical content.

[0029] A secondary battery includes a casing and an electrode assembly, the electrode assembly being housed within the casing and being the component where the electrochemical reaction occurs in the secondary battery. The casing may contain one or more electrode assemblies.

[0030] An electrode assembly is typically formed by winding or stacking a positive electrode sheet and a negative electrode sheet, with a separator typically provided between the positive and negative electrode sheets. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material, with the positive electrode active material coated on the surface of the positive electrode current collector. The positive electrode current collector includes a positive electrode coated area where the active material is coated and a positive electrode uncoated area where the active material is not coated, and the positive electrode uncoated area forms the positive electrode uncoated area stacked area of ​​the electrode assembly after winding. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material, with the negative electrode active material coated on the surface of the negative electrode current collector. The negative electrode current collector includes a negative electrode coated area where the active material is coated and a negative electrode uncoated area where the active material is not coated, and the uncoated area forms the negative electrode uncoated area stacked area of ​​the electrode assembly after winding. Taking lithium-ion secondary batteries as an example, the positive electrode current collector is made of aluminum, the positive electrode active material layer contains a positive electrode active material, such as lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The negative electrode current collector is made of copper, and the negative electrode active material layer contains a negative electrode active material, such as carbon or silicon. The separator is made of polypropylene (PP) or polyethylene (PE). To protect and insulate the cell, an insulating film may be coated on the outside of the cell, which may be made of PP, PE, PET, PVC, or other high-molecular polymer materials.

[0031] However, the inventors discovered that in existing secondary batteries, the positive electrode sheet is generally made of aluminum foil, which has a relatively high hardness, and therefore when the current collecting member and the positive electrode non-coated region are crimped together, the positive electrode non-coated region may collapse and shift during the press bending process, which affects the flatness of the welding surface of the entire positive electrode non-coated region, creating a large gap between the current collecting member and the positive electrode non-coated region, and affecting the reliability of the welding between the current collecting member and the positive electrode non-coated region.

[0032] In consideration of this, the present invention provides a technical solution in which an insulating layer is provided below the positive electrode non-coated region lamination area, the insulating layer including a first insulating layer provided on a first side of the positive electrode sheet facing the winding axis, and a second insulating layer located on a second side opposite the first side. By providing the first insulating layer with a height greater than that of the second insulating layer, the support force for the positive electrode non-coated region lamination area is further improved, the problem of post-collapse displacement of the positive electrode non-coated region lamination area is alleviated, the flatness of the welded surface of the positive electrode non-coated region lamination area is improved, and the rate of non-defective welds is increased.

[0033] 1 to 7, the present invention provides a secondary battery 100, which includes a casing 110, an electrode assembly 120, a current collecting member 130, an insulating layer 128, a terminal 150, and a cover plate 160.

[0034] Referring to FIG. 1 , the casing 110 includes an end wall 111 and a side wall 112 surrounding the end wall 111. The connection between the end wall 111 and the side wall 112 may be realized in various ways, as long as a stable seal and electrical connection can be formed. For example, it may be formed by integral pressing, integral casting, or split welding. The side wall 112 may be cylindrical or prismatic, or may be formed along any other closed loop contour that matches the end wall 111, but is not limited to these. In one embodiment, the outer edge of the end wall 111 is circular, and the side wall 112 cylindrically surrounds the outer edge of the end wall 111, with a circular opening 113 formed at the end of the side wall 112 remote from the end wall 111. A storage space is formed within the casing 110, surrounded by the end wall 111 and the side wall 112, and is used to house the electrode assembly 120, electrolyte, and other necessary battery components. Specifically, the diameter of the casing 110 may be determined based on the specific dimensions of the electrode assembly 120, and may be, for example, 18 mm, 21 mm, 46 mm, etc. The casing 110 may be made of a variety of materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. To prevent the casing 110 from rusting during long-term use, the surface of the casing 110 may be coated with an anti-rust material such as metallic nickel.

[0035] 1 to 3, the electrode assembly 120 is housed in the casing 110 and includes a wound structure formed by stacking and winding a positive electrode sheet 121, a negative electrode sheet 123, and a separator 122. The positive electrode sheet 121 includes a positive electrode current collector 1211 and a positive electrode active material, with the positive electrode active material being coated on the surface of the positive electrode current collector 1211. The positive electrode current collector 1211 includes a positive electrode coated region 1212 coated with the active material, a positive electrode uncoated region 1213 not coated with the active material, and an insulating layer 128 covering at least the boundary between the positive electrode coated region 1212 and the positive electrode uncoated region 1213. The positive electrode uncoated region 1213 extends outside the separator 122 at one end of the electrode assembly 120 in the direction of the winding axis 127 and is folded toward the winding axis 127 to form a stacked positive electrode uncoated region stacked region 125. The negative electrode sheet 123 includes a negative electrode current collector 1231 and a negative electrode active material, and the negative electrode active material is coated on the surface of the negative electrode current collector 1231. The negative electrode current collector 1231 includes a negative electrode coated region 1232 coated with the active material and a negative electrode uncoated region 1233 not coated with the active material, and the negative electrode uncoated region 1233 extends outside the separator 122 at one end in the direction of the winding axis 127 of the electrode assembly 120 and is folded in the direction of the winding axis 127 to form a laminated negative electrode uncoated region stacked region 124.

[0036] Referring to FIG. 1 , the current collecting member 130 includes a first current collecting member 131 and a second current collecting member 132. The materials of the first current collecting member 131 and the second current collecting member 132 are selected according to the polarity of the tabs to which they are connected. For example, when the second current collecting member 132 is connected to the positive electrode non-coated region lamination area 125, the second current collecting member 132 may be made of aluminum metal, and in this case, the first current collecting member 131 is connected to the negative electrode non-coated region lamination area 124 and may be made of copper metal. When the second current collecting member 132 is connected to the negative electrode non-coated region lamination area 124, the second current collecting member 132 may be made of copper metal, and in this case, the first current collecting member 131 is connected to the positive electrode non-coated region lamination area 125 and may be made of aluminum metal. The shapes and structures of the second current collecting member 132 and the first current collecting member 131 are not limited, as long as they can achieve a stable and reliable electrical connection. In this embodiment, the first current collecting member 131 at least partially covers the positive electrode non-coated region laminated area 125 and is welded to the positive electrode non-coated region laminated area 125. The second current collecting member 132 at least partially covers the negative electrode non-coated region laminated area 124 and is welded to the negative electrode non-coated region laminated area 124. The material of the first current collecting member 131 is aluminum metal.

[0037] 4 , the insulating layer 128 covers at least the boundary between the positive electrode coated region 1212 and the positive electrode uncoated region 1213 and extends to the folded portion 126 of the positive electrode uncoated region laminated region 125. That is, the insulating layer 128 can partially overlap the positive electrode coated region 1212 or be disposed in contact with the positive electrode coated region 1212. During actual processing, the folded portion 126 of the positive electrode uncoated region laminated region 125 forms a rounded corner, and the insulating layer 128 at least partially covers the positive electrode uncoated region 1213, thereby providing support against the compressive force from the current collecting member 130 when the positive electrode uncoated region laminated region 125 is folded. Both of the above two types of insulating layer 128 may at least partially cover the positive electrode uncoated region 1213, thereby providing support against the compressive force from the current collecting member 130 when the positive electrode uncoated region laminated region 125 is folded. Preferably, in this embodiment, the insulating layer 128 partially overlaps the positive electrode coating area 1212, and this arrangement has a better supporting effect.

[0038] 3 and 4 , the insulating layer 128 includes a first insulating layer 1281 disposed on a first side 1214 facing the winding axis 127 of the positive electrode sheet 121, and a second insulating layer 1282 disposed on a second side 1215 away from the winding axis 127. Both the first insulating layer 1281 and the second insulating layer 1282 extend along the direction of the winding axis 127 toward the positive electrode non-coated region stacked area 125. That is, the first insulating layer 1281 is located below the positive electrode non-coated region stacked area 125 after bending, and can directly apply a reaction force to the positive electrode non-coated region stacked area 125 that resists pressure from the current collecting member 130. Furthermore, along the direction of the winding axis 127, the height h1 of the first insulating layer 1281 is greater than the height h2 of the second insulating layer 1282. This installation further improves the support force of the positive electrode non-coated region lamination area 125, alleviates the problem of displacement after collapse of the positive electrode non-coated region lamination area 125, improves the flatness of the welding surface of the positive electrode non-coated region lamination area 125, and increases the rate of good welding products.

[0039] Referring to FIG. 1 , the terminal 150 penetrates the end wall 111 and is insulated from the end wall 111. The structural form of the terminal 150 may be any suitable form capable of penetrating the end wall 111 and electrically connecting with the positive electrode sheet 121 or the negative electrode sheet 123. For example, the cross section may be circular, rectangular, prismatic, or have a contoured shape capable of achieving stable electrical conductivity. One end of the terminal 150 facing the electrode assembly 120 penetrates the end wall 111 and is electrically connected to the tab directly or indirectly. For example, the terminal 150 may be electrically connected to the positive electrode sheet 121 via the first current collecting member 131 or to the negative electrode sheet 123 via the second current collecting member 132. The other end of the terminal 150 facing away from the electrode assembly 120 is exposed to the outside of the casing 110 and forms a corresponding electrode. The electrical conductivity of the terminal 150 may be either positive or negative. For example, in one embodiment, when the terminal 150 is electrically connected to the positive electrode non-coated region stacked area 125, the terminal 150 becomes the positive electrode, and the casing 110 forms the corresponding negative electrode. In another embodiment, when the terminal 150 is electrically connected to the negative electrode non-coated region stacked area 124, the terminal 150 becomes the negative electrode, and the casing 110 forms the corresponding positive electrode. A terminal 150 mounting hole is provided in the end wall 111, and the terminal 150 is mounted in the terminal 150 mounting hole in a sealed and insulated state. This structure of the casing 110 improves mounting efficiency and provides better assembly and sealing properties than a casing 110 type having openings 113 at both ends.

[0040] Referring to FIG. 1 , the terminal 150 is made of a conductive metal material. The terminal 150 may be made of aluminum. If the terminal 150 is made of aluminum, riveting can be easily performed. In this embodiment, the terminal 150 is made of aluminum and has a positive polarity. The casing 110 is made of low-carbon steel corresponding to the terminal 150, forming a corresponding negative polarity, and the terminal 150 and the casing 110 are electrically insulated. Electrical insulation between the terminal 150 and the end wall 111 of the casing 110 may be achieved in various ways. For example, insulation may be achieved by placing an insulating washer between the terminal 150 and the end wall 111. Alternatively, insulation may be achieved by forming an insulating coating layer on a portion of the terminal 150. Alternatively, several of the above methods may be combined.

[0041] 1 , the cover plate 160 is attached to the opening 113 in a sealing manner. The outer edge shape of the cover plate 160 corresponds to the shape of the opening 113 and connects with the side wall 112 to seal the opening 113. In a specific embodiment, the periphery of the cover plate 160 has a convex portion protruding toward the inside of the casing 110, and the side of the convex portion away from the electrode assembly 120 is formed as a first recess. The orthogonal projection shape of this first recess may be, but is not limited to, a ring, a rectangle, or other irregular shape. The convex portion includes a first side wall 112 that fits with the inner wall of the casing 110, and the first side wall 112 fits with the side wall 112 close to the opening 113. The protrusion is for guiding the assembly of the cover plate 160 and the opening 113, and the fit between the side wall 112 of the casing 110 and the cover plate 160 allows for quick circumferential positioning between the cover plate 160 and the opening 113, thereby improving welding efficiency and radial positioning accuracy of the welding.

[0042] 4 , in one example of the secondary battery 100 of the present invention, the difference between h1 and h2 is t, which satisfies 0.2 mm≦t≦1.5 mm. For example, it may be 0.2 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, or 1.5 mm. This arrangement maintains a safe distance between the first insulating layer 1281 and the positive electrode non-coated region stacked area 125, reducing the risk of the first insulating layer 1281 being crushed by the positive electrode non-coated region stacked area 125 and causing powder to fall.

[0043] 5 , in one example of the secondary battery 100 of the present invention, the radial dimension of the portion of the outermost tab that is shifted backward toward the outer periphery of the electrode assembly 120 is a, where a≦1.5 mm. For example, a may be 0.1 mm, 0.2 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, or 1.5 mm. The shifted backward portion is the portion between the base of the positive electrode non-coated region 1213 and the outermost radial position of the outermost positive electrode non-coated region 1213 of the electrode assembly 120. The shifted backward portion is formed by being folded and protruding from the base of the positive electrode non-coated region stacking region 125 toward the radially outer side of the electrode assembly 120 during the process of bending the positive electrode non-coated region stacking region 125 toward the winding axis 127 and the process of folding and compressing. Setting a≦1.5 mm increases the annular width of the lamination number stable zone of the positive electrode non-coated region lamination zone 125, which is suitable for welding, and is advantageous for welding. It also reduces the inclination of the slope formed by the rearwardly shifted positive electrode non-coated region lamination zone 125, thereby reducing the gap between the positive electrode non-coated region lamination zone 125 and the current collecting member 130, thereby improving the reliability and convenience of welding.

[0044] Referring to FIGS. 2 and 5, in an example of the secondary battery 100 of the present invention, on a reference plane formed by the winding axis 127 and any one radial line of the end face of the electrode assembly, the outer periphery of the winding structure cuts n circumferences of the non-coated positive electrode regions 1213. n is an arbitrary numerical value and is not limited thereto. The total thickness of the positive electrode sheet 121, the separator 122, and the negative electrode sheet 123 is b. Further, a / b < n, where a is the radial dimension of the portion where the tab is shifted backward toward the outer periphery of the electrode assembly 120, and b is the thickness of one unit of the positive electrode sheet 121, the separator 122, and the negative electrode sheet 123. The numerical value of b is not limited and is determined according to the actual situation. a / b represents the quantity of one unit of the positive electrode sheet 121, the separator 122, and the negative electrode sheet 123 covered by the portion where the tab is shifted backward toward the outer periphery of the electrode assembly 120. By arranging in this way, the annular region without a tab in the winding structure can accommodate the portion where the non-coated positive electrode region laminated area 125 located at the outermost periphery is displaced after collapse, so that the portion shifted backward of the non-coated positive electrode region laminated area 125 does not exceed the outer periphery of the electrode assembly 120, and the probability of affecting the insertion of the electrode assembly 120 into the casing can be reduced.

[0045] Referring to FIG. 5, in an example of the secondary battery 100 of the present invention, from the outer periphery to the inner periphery of the electrode assembly 120, the non-coated positive electrode region laminated area 125 includes a region 1251 where the number of laminations increases, a region 1252 where the number of laminations is stable, and a region 1253 where the number of laminations decreases in sequence. The non-coated positive electrode region laminated area 125 located in the region 1253 where the number of laminations decreases extends in a direction away from the current collector member 130. By arranging in this way, an inclined surface recessed at a position close to the winding axis 127 of the electrode assembly 120 is formed. On the one hand, this inclined surface serves to guide the flow of the electrolyte, and on the other hand, it prevents the upward warping of the non-coated positive electrode region laminated area 125 located in the region 1253 where the number of laminations decreases, and can improve the stability and convenience of the welding between the first current collector member 131 and the non-coated positive electrode region laminated area 125.

[0046] 5 , in one example of the secondary battery 100 of the present invention, the annular width of the positive electrode non-coated region stacking zone 125 is r, the annular width of the stack number stable zone 1252 is c, and c / r is greater than or equal to 0.35 (e.g., 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, or 0.8). Having c / r within this range ensures the range of the stack number stable zone 1252, improves welding reliability, reduces internal resistance, and is advantageous for improving the performance of the secondary battery 100.

[0047] Referring to FIG. 4 , in one example of a secondary battery 100 of the present invention, the insulating layer 128 contains a ceramic filler. The ceramic filler may include at least one of aluminum oxide, boehmite, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, and magnesium nitride. However, the present invention is not limited to these materials, and ceramic fillers used in the insulating layer 128 of other electrode sheets may also be used. The ceramic filler in the present invention may be selected from any one of the materials listed above, or may be selected from any two or more of the materials listed above. While ensuring insulation, the ceramic filler has relatively high hardness and can provide more stable support.

[0048] Referring to FIG. 4 , in one example of the secondary battery 100 of the present invention, the first insulating layer 1281 and the second insulating layer 1282 have different brightnesses. This difference in brightness can be achieved by adding different colorants or different ratios of the same colorants to the first insulating layer 1281 or the second insulating layer 1282. The colorants include, but are not limited to, at least one of titanium chrome brown, titanium nickel yellow, bismuth vanadate, chromium oxide green, cobalt green, cobalt blue, Prussian blue, cadmium red, cadmium yellow, lithopone, carbon black, iron oxide red, and iron oxide yellow. That is, the colorant can be any one of the materials listed above, or a combination of any two or more of the materials listed above. Observing the difference in brightness between the first insulating layer 1281 and the second insulating layer 1282 can effectively distinguish the front and back of the positive electrode sheet 121 and prevent the positive electrode sheet 121 from being turned over. Furthermore, since the insulating layer 128 does not participate in chemical reactions, the front and back of the positive electrode sheet 121 can be distinguished through the insulating layer 128, eliminating the need for additional markings and causing relatively little impact on the battery.

[0049] 6, the present invention further provides a battery pack 10, which includes any of the secondary batteries 100 described above. In one embodiment of the battery pack 10 of the present invention, the battery pack 10 includes a case 101, a case cover 102, and a plurality of secondary batteries 100, the plurality of secondary batteries 100 being disposed within the case 101 and connected to each other in series, parallel, or a combination of series and parallel, and the case cover 102 covering the case 101 to protect the plurality of secondary batteries 100. It should be noted that the battery pack 10 may include, in addition to the secondary battery 100 of the present invention, components such as a thermal management system and a circuit board for the battery pack 10, and the battery pack 10 may be a battery module, a battery pack, an energy storage cabinet, etc. This will not be described in further detail here.

[0050] Referring to FIG. 7 , the present invention further provides an electronic device 1, which includes the battery pack 10 described above. An actuator 11 is electrically connected to the battery pack 10 to receive power. For example, the electronic device 1 is a vehicle, which may be a gasoline-powered vehicle, a gas-powered vehicle, or a new energy vehicle. The new energy vehicle may be, but is not limited to, a pure electric vehicle, a hybrid vehicle, or a range-extended vehicle. The actuator 11 is a vehicle body, and the battery pack 10 is installed at the bottom of the body and provides power for driving the vehicle or operating electrical components inside the vehicle. However, in other embodiments, the electronic device 1 may be a mobile phone, a portable device, a laptop, a boat, space equipment, an electric toy, an electric tool, or the like. Space equipment includes airplanes, rockets, space shuttles, and spacecraft. The actuator 11 may be a unit component that receives power from the battery pack 10 and performs a corresponding operation, such as a blade rotation unit of an electric fan or a suction unit of a vacuum cleaner. The electric toys include stationary and mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys. The power tools include metal cutting power tools, grinding power tools, assembly power tools, and railroad power tools, such as power drills, power grinders, power wrenches, power screwdrivers, power hammers, impact drills, concrete vibrators, and power planers. The embodiments of the present invention do not impose any particular restrictions on the electronic device 1.

[0051] In the secondary battery of the present invention, the insulating layer covers at least the boundary between the positive electrode coated region and the positive electrode uncoated region and extends to the folded portion of the positive electrode uncoated region stacked area. That is, the insulating layer may at least partially cover the positive electrode uncoated region, and can act as a support against the crimping force from the current collecting member when the positive electrode uncoated region stacked area is folded. Furthermore, the first insulating layer is located on the first side facing the winding axis, i.e., below the positive electrode uncoated region stacked area after folding, and can directly provide the positive electrode uncoated region stacked area with a counteracting force that resists the pressure from the current collecting member. By setting the height of the first insulating layer higher than the height of the second insulating layer, the support force for the positive electrode uncoated region stacked area can be further improved, the problem of post-collapse displacement of the positive electrode uncoated region stacked area can be alleviated, the flatness of the welded surface of the positive electrode uncoated region stacked area can be improved, and the welding yield rate can be improved. Therefore, the present invention effectively overcomes practical problems in the known art and has great utility and significance. The above examples are intended to illustrate the principles and effects of the present invention and are not intended to limit the present invention. Those skilled in the art may make modifications or changes to the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be included in the scope of the claims of the present invention. [Industrial Applicability]

[0052] An object of the present invention is to provide a secondary battery, a battery pack, and an electronic device that solve the technical problem that the laminated area of ​​the positive electrode non-coated region collapses and shifts during the press bending process. [Explanation of symbols]

[0053] 1 Electronic equipment 10 Battery Pack 11. Operating unit 101 cases 102 Case Cover 100 Secondary battery 110 Casing 111 End Wall 112 Side wall 113 Aperture 120 Electrode Assembly 121 Positive electrode sheet 1211 Positive electrode current collector 1212 Positive electrode coating area 1213 Positive electrode non-coated area 1214 First aspect 1215 Second aspect 122 Separator 123 Negative electrode sheet 1231 Negative electrode current collector 1232 Negative electrode coating area 1233 Negative electrode non-coated area 124 Negative electrode non-coated area stacked area 125 Positive electrode non-coated area laminated area 1251 Increased number of layers area 1252 Stacking number stability area 1253 Area with reduced number of stacked layers 126 Bending section 127 Winding shaft 128 Insulating Layer 1281 First insulating layer 1282 Second insulating layer 130 Current collecting member 131 First current collecting member 132 Second current collecting member 150 terminals 160 Lid plate

Claims

1. A casing; an electrode assembly accommodated in the casing, the electrode assembly including a wound structure formed by stacking and winding a positive electrode sheet, a negative electrode sheet, and a separator, the positive electrode sheet including a positive electrode coated region where a positive electrode active material layer is coated, a positive electrode uncoated region where the positive electrode active material layer is not coated, and an insulating layer covering at least a boundary between the positive electrode coated region and the positive electrode uncoated region, the positive electrode uncoated region extending outside the separator at one end in a direction of a winding axis of the electrode assembly and folded toward the winding axis to form a positive electrode uncoated region stacked area; a current collecting member at least partially covering the positive electrode non-coated region laminated area and welded to the positive electrode non-coated region laminated area. wherein the insulating layer includes a first insulating layer provided on a first side of the positive electrode sheet facing the winding axis and a second insulating layer provided on a second side away from the winding axis, the first insulating layer and the second insulating layer both extend along the direction of the winding axis into the positive electrode non-coated region stacking area, and a height h1 of the first insulating layer is greater than a height h2 of the second insulating layer along the direction of the winding axis.

2. 2. The secondary battery according to claim 1, wherein the difference between h1 and h2 is t, and 0.2 mm≦t≦1.5 mm.

3. 2. The secondary battery according to claim 1, wherein a radial dimension of a portion of the positive electrode non-coated region stacked area located at the outermost periphery that is shifted toward the outer periphery of the electrode assembly is a, where a≦1.5 mm, and the shifted portion is a portion between a base portion of the positive electrode non-coated region and the outermost radial direction of the outermost positive electrode non-coated region of the outermost periphery of the electrode assembly.

4. 4. The secondary battery according to claim 3, wherein, on a reference plane formed by the winding axis and any one of the longitudinal lines on the end surface of the electrode assembly, the outer periphery of the wound structure cuts through n peripheries of the positive electrode non-coated region, the sum of the thicknesses of the positive electrode sheet, the separator, and the negative electrode sheet is b, and a / b<n.

5. 2. The secondary battery according to claim 1, wherein the positive electrode non-coated region stacking zone includes, from the outer periphery toward the inner periphery of the electrode assembly, a stacking number increasing zone, a stacking number stable zone, and a stacking number decreasing zone, in that order, and the positive electrode non-coated region stacking zone located in the stacking number decreasing zone extends in a direction away from the current collecting member.

6. 6. The secondary battery according to claim 5, wherein the annular width of the positive electrode non-coated region stacking zone is r, the annular width of the stack number stable zone is c, and c / r≧0.

35.

7. The secondary battery according to claim 1 , wherein the insulating layer contains a ceramic filler.

8. 8. The secondary battery according to claim 7, wherein the first insulating layer and the second insulating layer have different brightnesses.

9. A battery pack comprising the secondary battery according to any one of claims 1 to 8.

10. An electronic device comprising the battery pack of claim 9.

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