Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery includes: a case; the electrode assembly is accommodated in the shell and is formed by laminating a positive plate, a diaphragm and a negative plate; in a preset direction, a first positive electrode surface of a positive electrode current collector of the positive plate comprises a first positive electrode coating region and a first positive electrode uncoated region, and a second positive electrode surface of the positive electrode current collector of the positive plate comprises a second positive electrode coating region and a second positive electrode uncoated region; the first insulating layer covers a part of the first positive electrode uncoated region and a part of the first positive electrode thinned region of the first positive electrode active material layer; the second insulating layer covers part of the second positive electrode uncoated area, and the second insulating layer and the second positive electrode active material layer are not overlapped in the thickness direction of the positive electrode current collector. By arranging the specific structure of the first insulating layer and the second insulating layer, the yield of the battery cell is effectively improved.

Description

TECHNICAL FIELD

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

[0002] In recent years, with the rapid development of electric vehicles, consumer electronics and new energy storage systems, battery technology is an important factor for the development of electric vehicles.

[0003] In the development of battery technology, how to improve the yield of the battery cell is an urgent technical problem in battery technology. UTILITY MODEL CONTENTS

[0004] The utility model solves the technical problems that the prior art has the above technical problems, provides a secondary battery, a battery pack and an electronic device.

[0005] The utility model solves the above technical problems through the following technical schemes:

[0006] A secondary battery, characterized in that it comprises:

[0007] A shell;

[0008] An electrode assembly accommodated in the shell, the electrode assembly is formed by laminating a positive electrode sheet, a separator and a negative electrode sheet, the electrode assembly comprises a first end provided with a positive electrode tab and a second end provided with a negative electrode tab, and the second end to the first end is a preset direction;

[0009] The positive electrode sheet comprises a positive electrode current collector, a positive electrode active material layer and an insulating layer, the positive electrode current collector comprises a first positive electrode surface and a second positive electrode surface arranged along the thickness direction, the positive electrode active material layer comprises a first positive electrode active material layer and a second positive electrode active material layer, along the preset direction, the first positive electrode surface comprises a first positive electrode coating area covered with the first positive electrode active material layer and a first positive electrode non-coating area not covered with the first positive electrode active material layer, and the second positive electrode surface comprises a second positive electrode coating area covered with the second positive electrode active material layer and a second positive electrode non-coating area not covered with the second positive electrode active material layer;

[0010] Along the preset direction, the first positive electrode active material layer comprises a first positive electrode flat area and a first positive electrode thinning area, and the second positive electrode active material layer comprises a second positive electrode flat area and a second positive electrode thinning area;

[0011] The insulating layer comprises a first insulating layer and a second insulating layer, the first insulating layer covers part of the first positive electrode non-coating area and part of the first positive electrode thinning area; the second insulating layer covers part of the second positive electrode non-coating area, and along the thickness direction of the positive electrode current collector, the projection of the second insulating layer and the second positive electrode active material layer do not overlap.

[0012] In the technical solution, by setting the first insulating layer to cover part of the first positive electrode non-coating area and part of the first positive electrode thinning area, the thickness of the thinning area (the area where the positive electrode thinning area of the positive electrode active material layer is located) can be effectively compensated, thereby reducing the thickness difference between the thinning area and the main area (the area where the positive electrode flat area of the positive electrode active material layer is located), so that effective compaction can be achieved in the area where the first insulating layer overlaps the first positive electrode thinning area (part of the area where the positive electrode active material layer is located) during hot pressing, thereby achieving the same bonding effect as the main area and preventing the electrode assembly from loosening between layers and causing the diaphragm to wrinkle, thereby effectively improving the yield of the battery cell. Further, by setting the second insulating layer to cover part of the second positive electrode non-coating area, and along the thickness direction of the positive electrode current collector, the second insulating layer and the second positive electrode active material layer do not overlap, that is, the second insulating layer does not cover the second positive electrode thinning area, thereby avoiding the thickness of the thinning area being greater than the thickness of the main area, and the phenomenon of drumming, which leads to the phenomenon that coating cannot be completed, thereby further effectively improving the yield of the battery cell.

[0013] Preferably, along the preset direction, the width of the overlapping area of the first insulating layer along the thickness direction of the positive electrode current collector is 1.5mm-2.5mm.

[0014] Preferably, along the preset direction, the first positive electrode non-coating area includes a first positive electrode adjacent area and a first surface of the positive electrode tab protruding from the first positive electrode adjacent area, and the second positive electrode non-coating area includes a second positive electrode adjacent area and a second surface of the positive electrode tab protruding from the second positive electrode adjacent area.

[0015] Along the preset direction, the width of the first insulating layer on the first positive electrode adjacent area is 6.5mm-9.5mm, and the width of the first insulating layer on the first surface of the positive electrode tab is 3mm-5mm; and / or,

[0016] Along the preset direction, the width of the second insulating layer on the second positive electrode adjacent area is 5mm-7mm, and the width of the second insulating layer on the second surface of the positive electrode tab is 3mm-5mm.

[0017] Preferably, along the thickness direction of the positive electrode current collector, the thickness of the first insulating layer near one end of the first positive electrode active material layer is 60-95% of the thickness of the first positive electrode flat area; and / or,

[0018] Along the thickness direction of the positive electrode current collector, the thickness of the second insulating layer is 10-30% of the thickness of the second positive electrode flat area.

[0019] Preferably, along the preset direction, the width of the first positive electrode thinning area is 2-10mm; and / or,

[0020] Along the preset direction, the width of the second positive electrode thinning area is 2-10mm.

[0021] Preferably, the first positive electrode active material layer comprises LFP; and / or, the second positive electrode active material layer comprises LFP; and / or,

[0022] The insulating layer comprises inorganic insulating filler and binder, the mass fraction of the inorganic insulating filler is 70-90% and the mass fraction of the binder is 10-30% based on the mass of the insulating layer.

[0023] Preferably, the second insulating layer has a spacing between one end of the second positive electrode active material layer and the second positive electrode active material layer; or,

[0024] The second insulating layer abuts one end of the second positive electrode active material layer and the second positive electrode active material layer.

[0025] Preferably, the secondary battery further comprises a cover plate assembly, the cover plate assembly is arranged on the shell and cooperates with the shell to define a containing cavity, and the electrode assembly is contained in the containing cavity; and / or,

[0026] The secondary battery is a square battery; and / or, the electrode assembly is a laminated electrode assembly.

[0027] A battery pack comprising the secondary battery.

[0028] An electronic device comprising the battery pack.

[0029] The positive effects of the utility model lie in:

[0030] In the prior art, since the current laminated electrode assembly is prone to diaphragm wrinkles on the positive tab side after heat pressing in the assembly process, thereby causing low voltage problems of the finished product battery, the main cause of the problem is that the thickness of the edge thinning area of the laminated electrode assembly is thinner than the thickness of the main area during heat pressing, the edge thinning area cannot be compacted, the diaphragm and the electrode sheet (including the positive sheet and the negative sheet) are poorly adhered, the first diaphragm is adhered to the pressing plate in the moment when the pressing plate is lifted, an internal and external pressure difference is generated, the diaphragm in the edge thinning area is loose and wrinkles are caused.

[0031] In the utility model, the first insulating layer is arranged on the part of the first positive electrode non-coating area and the part of the first positive electrode thinning area, which can effectively compensate the thickness of the thinning area (the area where the positive electrode thinning area of the positive electrode active material layer is located), thereby reducing the thickness difference between the thinning area and the main area (the area where the positive electrode flat area of the positive electrode active material layer is located), so that the first insulating layer covering the overlapping area of the first positive electrode thinning area (the area where the part of the positive electrode thinning area of the positive electrode active material layer is located) can be effectively compacted during heat pressing, thereby realizing the same bonding effect as the main area and preventing the electrode assembly from being loose between layers to cause diaphragm wrinkles, thereby effectively improving the yield of the battery. Further, the second insulating layer is arranged on the part of the second positive electrode non-coating area, and the second insulating layer and the second positive electrode active material layer do not overlap in the thickness direction of the positive electrode current collector, that is, the second insulating layer does not cover the second positive electrode thinning area, thereby avoiding the thickness of the thinning area being greater than the thickness of the main area and causing the edge to be raised, which causes the coating to be unable to complete the winding, thereby further effectively improving the yield of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a three-dimensional explosion structure schematic view of the secondary battery of a preferred embodiment of the utility model.

[0033] Figure 2 It is a partial three-dimensional structure schematic view of the secondary battery of a preferred embodiment of the utility model.

[0034] Figure 3 It is a partial sectional view structure schematic view of the electrode assembly of the secondary battery of a preferred embodiment of the utility model.

[0035] Figure 4 It is a partial sectional view structure schematic view of the positive sheet of the secondary battery of a preferred embodiment of the utility model.

[0036] Figure 5 It is a partial sectional view structure schematic view of the negative sheet of the secondary battery of a preferred embodiment of the utility model.

[0037] Figure 6 It is a partial structure schematic view of the positive sheet of the secondary battery of a preferred embodiment of the utility model when it is unfolded.

[0038] Figure 7 Another angle's partial structure schematic view of the positive plate of the secondary battery of a preferred embodiment of the present application.

[0039] Figure 8 Structure schematic view of the battery pack of a preferred embodiment of the present application.

[0040] Figure 9 Structure schematic view of the electronic device of a preferred embodiment of the present application.

[0041] Explanation of reference signs

[0042] Electronic device 1000

[0043] Battery pack 100

[0044] Working part 300

[0045] Box body 310

[0046] Box cover 320

[0047] Secondary battery 1

[0048] Shell 10

[0049] Accommodating cavity 13

[0050] Electrode assembly 20

[0051] Positive plate 21

[0052] Positive current collector 211

[0053] First positive surface 2111

[0054] First positive coating area 21111

[0055] First positive uncoated area 21112

[0056] First positive abutment area 21113

[0057] First surface of positive tab 21114

[0058] Second positive surface 2112

[0059] Second positive coating area 21121

[0060] Second positive uncoated area 21122

[0061] Second positive abutment area 21123

[0062] Second surface of positive tab 21124

[0063] Positive active material layer 212

[0064] First positive electrode active material layer 213

[0065] First positive flat region 2131

[0066] First positive electrode thinning region 2132

[0067] Second positive electrode active material layer 214

[0068] Second positive pole flat region 2141

[0069] Second positive electrode thinning region 2142

[0070] Insulation layer 215

[0071] First insulating layer 2151

[0072] Overlapping region 21511

[0073] Second insulating layer 2152

[0074] Diaphragm 22

[0075] Negative electrode 23

[0076] Negative current collector 231

[0077] Negative electrode active material layer 232

[0078] Negative electrode flat region 233

[0079] Negative electrode thinning region 234

[0080] Cover assembly 40

[0081] Cover body 41

[0082] Injection hole 411

[0083] Insulating component 42

[0084] Electrode terminal 43

[0085] Top cover 50

[0086] Preset direction Q

[0087] Thickness direction T Detailed Implementation

[0088] The present invention will be described more clearly and completely below with reference to the accompanying drawings, using a preferred embodiment.

[0089] In the prior art, after hot pressing during the assembly process of the stacked electrode assembly, diaphragm wrinkles are easily generated on the positive electrode tab side, which leads to low voltage problems in the finished battery cell. The main reason for this problem is that the thickness of the thinned area at the edge of the stacked electrode assembly is thinner than the thickness of the main body area during hot pressing. The thinned area cannot be compacted during hot pressing, resulting in poor adhesion between the diaphragm and the electrode (including the positive electrode and the negative electrode). When the hot pressing plate is lifted, the first layer of diaphragm adheres to the pressing plate, generating an internal and external pressure difference. The diaphragm in the thinned area that is not compacted loosens and causes wrinkles.

[0090] like Figure 1 and Figure 2 As shown, this embodiment provides a secondary battery 1. The secondary battery 1 includes a housing 10 and an electrode assembly 20, the electrode assembly 20 being housed within the housing 10.

[0091] like Figure 3 As shown, the electrode assembly 20 is formed by stacking a positive electrode 21, a separator 22, and a negative electrode 23. The stacking includes either winding the stacked electrodes to form a wound electrode assembly 20 or stacking the stacked electrodes to form a stacked electrode assembly 20. The electrode assembly 20 includes a first end with a positive electrode tab and a second end with a negative electrode tab, the direction from the second end to the first end being a preset direction Q.

[0092] like Figure 4 As shown, the positive electrode sheet 21 includes a positive current collector 211, a positive active material layer 212, and an insulating layer 215. The positive current collector 211 includes a first positive electrode surface 2111 and a second positive electrode surface 2112 disposed along the thickness direction T. The positive active material layer 212 includes a first positive active material layer 213 and a second positive active material layer 214. Along a preset direction Q, the first positive electrode surface 2111 includes a first positive electrode coated area 21111 covered by the first positive active material layer 213 and a first positive electrode uncoated area 21112 not covered by the first positive active material layer 213. The second positive electrode surface 2112 includes a second positive electrode coated area 21121 covered by the second positive active material layer 214 and a second positive electrode uncoated area 21122 not covered by the second positive active material layer 214.

[0093] Along the preset direction Q, the first positive electrode active material layer 213 includes a first positive electrode flat region 2131 and a first positive electrode thinning region 2132, and the second positive electrode active material layer 214 includes a second positive electrode flat region 2141 and a second positive electrode thinning region 2142.

[0094] The insulating layer 215 includes a first insulating layer 2151 and a second insulating layer 2152. The first insulating layer 2151 covers a portion of the uncoated area 21112 of the first positive electrode and a portion of the thinned area 2132 of the first positive electrode. The second insulating layer 2152 covers a portion of the uncoated area 21122 of the second positive electrode, and the projection of the second insulating layer 2152 and the second positive electrode active material layer 214 do not overlap along the thickness direction T of the positive electrode current collector 211.

[0095] In this way, by setting the first insulating layer 2151 to cover part of the first positive electrode uncoated area 21112 and part of the first positive electrode thinning area 2132, the thickness of the thinned area (the area where the positive electrode thinning area of ​​the positive electrode active material layer 212 is located) can be effectively compensated, thereby reducing the thickness difference between the thinned area and the main body area (the area where the positive electrode straight area of ​​the positive electrode active material layer 212 is located). Thus, during hot pressing, the area where the first insulating layer 2151 covers the first positive electrode thinning area 2132 (the area where part of the positive electrode thinning area of ​​the positive electrode active material layer 212 is located) can be effectively compacted, thereby achieving the same bonding effect as the main body area, preventing the electrode assembly 20 from having interlayer loosening and causing wrinkles in the separator 22, thereby effectively improving the yield of the battery cell. Furthermore, by providing a second insulating layer 2152 covering a portion of the uncoated area 21122 of the second positive electrode, and ensuring that the second insulating layer 2152 does not overlap with the second positive electrode active material layer 214 along the thickness direction T of the positive electrode current collector 211, i.e., the second insulating layer 2152 does not cover the thinned area 2142 of the second positive electrode, meaning that there is a gap between the end of the second insulating layer 2152 near the second positive electrode active material layer 214 and the second positive electrode active material layer 214, or the end of the second insulating layer 2152 near the second positive electrode active material layer 214 abuts against the second positive electrode active material layer 214, thereby avoiding the phenomenon that the thickness of the thinned area is greater than the thickness of the main body area, resulting in bulging edges and preventing the coating from being completed and rolled up, thus further effectively improving the yield of the battery cell. In addition, providing the first insulating layer 2151 and the second insulating layer 2152 also has the beneficial technical effect of improving the strength of the positive electrode tab and improving the situation of the positive electrode tab being inserted backwards. The first insulating layer 2151 and the second insulating layer 2152 can be either a tape structure or a coating structure.

[0096] It should be noted that, since the first insulating layer 2151 covers part of the uncoated area 21112 of the first positive electrode and part of the thinned area 2132 of the first positive electrode, the end of the first insulating layer 2151 near the flat area 2131 of the first positive electrode is on the thinned area 2132 of the first positive electrode, while the end of the first insulating layer 2151 away from the flat area 2131 of the first positive electrode is on the uncoated area 21112 of the first positive electrode.

[0097] In this embodiment, the first positive electrode active material layer 213 and the second positive electrode active material layer 214 are symmetrically arranged with respect to the positive electrode current collector 211, that is, the first positive electrode flat region 2131 and the second positive electrode flat region 2141 are symmetrically arranged with respect to the positive electrode current collector 211; similarly, the first positive electrode thinning region 2132 and the second positive electrode thinning region 2142 are symmetrically arranged with respect to the positive electrode current collector 211.

[0098] like Figure 6 As shown, in this embodiment, along the preset direction Q, the first uncoated positive electrode area 21112 includes a first positive electrode adjacent area 21113 and a first surface 21114 of the positive electrode tab protruding from the first positive electrode adjacent area 21113. Along the preset direction Q, the width w11 of the first insulating layer 2151 on the first positive electrode adjacent area 21113 is 6.5mm-9.5mm, and the width w12 of the first insulating layer 2151 on the first surface 21114 of the positive electrode tab is 3mm-5mm. By providing the first insulating layer 2151 on the first surface 21114 of the positive electrode tab, the strength of the positive electrode tab can be improved, and the situation of reverse insertion of the positive electrode tab can be mitigated.

[0099] Please refer to the following: Figure 4 Along the preset direction Q, the width w3 of the overlapping area 21511 of the first insulating layer 2151 along the thickness direction T of the positive current collector 211 and the first positive electrode thinning area 2132 is 1.5mm-2.5mm. By setting the range of values ​​for the width w3 of the overlapping area 21511 of the first insulating layer 2151 along the thickness direction T of the positive current collector 211 and the first positive electrode thinning area 2132, the bonding effect between the electrode sheet and the separator 22 after edge hot pressing is ensured, while preventing the problem of excessive thickness caused by an excessively large width w3 of the overlapping area 21511.

[0100] The width w1 of the first insulating layer 2151 is equal to the sum of the width w11 of the first insulating layer 2151 on the first positive electrode adjacent region 21113, the width w12 of the first insulating layer 2151 on the first surface 21114 of the positive electrode tab, and the width w3 of the overlapping region 21511 of the first insulating layer 2151 and the first positive electrode thinning region 2132 (w1 = w11 + w12 + w3). By setting the range of the width w1 of the first insulating layer 2151, on the one hand, it can avoid the first insulating layer 2151 being too small, thus failing to achieve the technical effect of reducing the thickness difference between the thinning region and the main body region, as well as the insulation effect; on the other hand, it can avoid the first insulating layer 2151 being too large, thus affecting the conductivity of the positive electrode tab.

[0101] like Figure 7As shown, along the preset direction Q, the second positive electrode uncoated area 21122 includes a second positive electrode adjacent area 21123 and a second surface 21124 of the positive electrode tab protruding from the second positive electrode adjacent area 21123. Along the preset direction Q, the width w21 of the second insulating layer 2152 on the second positive electrode adjacent area 21123 is 5mm-7mm, and the width w22 of the second insulating layer 2152 on the second surface 21124 of the positive electrode tab is 3mm-5mm. The width w2 of the second insulating layer 2152 is equal to the sum of the width w21 of the second insulating layer 2152 on the second positive electrode adjacent area 21123 and the width w22 of the second insulating layer 2152 on the second surface 21124 of the positive electrode tab. By setting the range of the width w2 of the second insulating layer 2152, on the one hand, it can be avoided that the width w2 of the second insulating layer 2152 is too small, thus failing to provide insulation; on the other hand, it can be avoided that the width w2 of the second insulating layer 2152 is too large, thus affecting the conductivity of the positive electrode tab. Furthermore, by setting the second insulating layer 2152 on the second surface 21124, the strength of the positive electrode tab can be improved, and the situation of reverse insertion of the positive electrode tab can be mitigated.

[0102] Preferably, along the thickness direction T of the positive electrode current collector 211, the thickness t1 of the first insulating layer 2151 near the end of the first positive electrode active material layer 213 is 60%-95% of the thickness t2 of the first positive electrode straight region 2131. By using the relationship between the thickness t1 of the first insulating layer 2151 near the end of the first positive electrode active material layer 213 and the thickness t2 of the first positive electrode straight region 2131, the thickness difference between the thinned region and the main body region is reduced, while preventing the thickness of the thinned region from exceeding the thickness of the main body region and thus avoiding edge bulging.

[0103] It should be noted that the thickness t1 of the first insulating layer 2151 near the end of the first positive electrode active material layer 213 refers to the distance from the outer surface of the first insulating layer 2151 near the end of the first positive electrode active material layer 213 to the first positive electrode surface 2111 of the positive electrode current collector 211 along the thickness direction T of the positive electrode current collector 211.

[0104] Along the thickness direction T of the positive electrode current collector 211, the thickness t3 of the second insulating layer 2152 is 10%-30% of the thickness t4 of the second positive electrode straight region 2141. By setting the relationship between the thickness t3 of the second insulating layer 2152 and the thickness t4 of the second positive electrode straight region 2141, while ensuring that the second insulating layer 2152 plays an insulating role, it avoids the second insulating layer 2152 being too thick, which would increase the overall thickness of the thinned region and exceed the thickness of the main body region, resulting in a bulging edge phenomenon.

[0105] Specifically, the thickness of the first insulating layer 2151 is 10μm-30μm. By limiting the range of the thickness of the first insulating layer 2151, the first insulating layer 2151 reduces the thickness difference between the thinned area and the main body area, while preventing the thickness of the thinned area from exceeding the thickness of the main body area and thus avoiding bulging. The thickness of the first insulating layer 2151 is the distance from the outer surface of the first insulating layer 2151 to the first positive electrode surface 2111 of the positive current collector 211.

[0106] Specifically, the thickness t3 of the second insulating layer 2152 is 10μm-30μm. By limiting the range of the thickness t3 of the second insulating layer 2152, while the first insulating layer 2151 provides insulation, it avoids the second insulating layer 2152 from being too thick, which would increase the overall thickness of the thinned area and exceed the thickness of the main body area, resulting in a bulging edge phenomenon. The thickness of the second insulating layer 2152 is the distance from the outer surface of the second insulating layer 2152 to the second positive electrode surface 2112 of the positive electrode current collector 211.

[0107] Preferably, along the preset direction Q, the width k1 of the first positive electrode thinning region 2132 is 2mm-10mm. By limiting the range of values ​​for the width k1 of the first positive electrode thinning region 2132, the excessive width k1 of the first positive electrode thinning region 2132 is avoided from affecting the energy density of the battery.

[0108] Along the preset direction Q, the width k2 of the second positive electrode thinning region 2142 is 2mm-10mm. By limiting the range of values ​​for the width k2 of the second positive electrode thinning region 2142, the excessive width k2 of the second positive electrode thinning region 2142 is avoided from affecting the energy density of the battery.

[0109] The first positive electrode active material layer 213 includes LFP (lithium iron phosphate). In the prior art, when the first positive electrode active material layer 213 includes LFP, a fusion problem can occur between the first positive electrode active material layer 213 and the first insulating layer 2151. That is, a gap can easily form between the first positive electrode active material layer 213 and the first insulating layer 2151, exposing the positive electrode current collector 211. In this embodiment, the first insulating layer 2151 largely covers the first positive electrode active material layer 213, thereby avoiding the situation where the positive electrode current collector 211 is exposed, that is, avoiding the fusion problem between the first positive electrode active material layer 213 and the first insulating layer 2151. In other embodiments, the first positive electrode active material layer 213 may not include LFP.

[0110] In this embodiment, the second positive electrode active material layer 214 also includes LFP (lithium iron phosphate). In other embodiments, the second positive electrode active material layer 214 may not include LFP.

[0111] Insulating layer 215 comprises inorganic insulating filler and binder, wherein the inorganic insulating filler accounts for 70%-90% of the mass and the binder accounts for 10%-30% of the mass based on the mass of insulating layer 215. Specifically, the first insulating layer 2151 comprises inorganic insulating filler and binder, wherein the inorganic insulating filler accounts for 70%-90% of the mass and the binder accounts for 10%-30% of the mass based on the mass of the first insulating layer 2151; the second insulating layer 2152 comprises inorganic insulating filler and binder, wherein the inorganic insulating filler accounts for 70%-90% of the mass and the binder accounts for 10%-30% of the mass based on the mass of the second insulating layer 2152.

[0112] In other embodiments, the insulating layer 215 may also be an adhesive tape, which includes a substrate and an adhesive layer, wherein the substrate is PET (Polyethylene terephthalate).

[0113] In this embodiment, the end of the second insulating layer 2152 near the second positive electrode active material layer 214 abuts against the second positive electrode active material layer 214, preventing the second insulating layer 2152 from occupying too much space and affecting the area where the positive electrode tab is located, thereby avoiding affecting the energy density of the battery. However, it is not limited to this. In other embodiments, there may be a gap between the end of the second insulating layer 2152 near the second positive electrode active material layer 214 and the second positive electrode active material layer 214.

[0114] like Figure 5 As shown, in this embodiment, specifically, the negative electrode sheet 23 includes a negative electrode current collector 231; a portion of at least one side of the negative electrode current collector 231 along the thickness direction T is covered with a negative electrode active material layer 232. Along a direction opposite to the preset direction Q, the negative electrode active material layer 232 includes an adjoining negative electrode straight region 233 and a negative electrode thinning region 234.

[0115] The thickness direction of the negative electrode current collector 231 is in the same direction as the thickness direction T of the positive electrode current collector 211. The negative electrode current collector 231 includes a first negative electrode surface and a second negative electrode surface arranged opposite to each other along the thickness direction T.

[0116] A portion of at least one side of the negative electrode current collector 231 along the thickness direction T is covered with a negative electrode active material layer 232. That is, a portion of at least one of the first negative electrode surface and the second negative electrode surface is covered with the negative electrode active material layer 232. In this embodiment, portions of both the first and second negative electrode surfaces are covered with the negative electrode active material layer 232. The negative electrode active material layers 232 located on the first and second negative electrode surfaces are symmetrically arranged with respect to the negative electrode current collector 231. However, this is not a limitation; in other embodiments, a portion of one of the first and second negative electrode surfaces may be covered with the negative electrode active material layer 232.

[0117] Please refer to the following: Figure 1 and Figure 2 In this embodiment, the secondary battery 1 is a square battery. However, it is not limited to this; in other embodiments, the secondary battery 1 can also be a cylindrical battery or other types of batteries.

[0118] In this embodiment, the electrode assembly 20 is a stacked electrode assembly 20.

[0119] In this embodiment, the first insulating layer 2151 covers a portion of the uncoated area 21112 and a portion of the thinned area 2132 of the first positive electrode, and the second insulating layer 2152 covers a portion of the uncoated area 21122 of the second positive electrode. The second insulating layer 2152 and the second positive electrode active material layer 214 do not overlap along the thickness direction T of the positive electrode current collector 211. This specific arrangement can effectively improve the yield rate of the battery cell when applied to a square battery.

[0120] The secondary battery 1 also includes a cover assembly 40, which covers the housing 10 and, together with the housing 10, defines a receiving cavity 13, in which the electrode assembly 20 is received. The cover assembly 40 includes a cover body 41 and an insulating member 42. The cover body 41 has a through-hole 411 along its thickness direction T. The insulating member 42 is located between the cover body 41 and the electrode assembly 20.

[0121] The cover plate assembly 40 also includes electrode terminals 43. One end of the electrode terminal 43 is electrically connected to the tabs leading out from the electrode assembly 20, and the other end passes through the first electrode lead-out hole on the insulating member 42 and the second electrode lead-out hole on the cover plate body 41 in sequence. The tabs leading out from the positive electrode plate 21 are positive electrode tabs, and the tabs leading out from the negative electrode plate 23 are negative electrode tabs. The positive electrode tabs and negative electrode tabs are electrically connected to the corresponding electrode terminals 43, respectively.

[0122] The secondary battery 1 also includes a top cover 50 disposed on the cover assembly 40.

[0123] like Figure 8As shown, this utility model also provides a battery pack 100, which includes the aforementioned secondary battery 1. In one embodiment of the battery pack 100, the battery pack 100 includes a housing 310, a cover 320, and multiple secondary batteries 1. The multiple secondary batteries 1 are placed in the housing 310 and are connected in series, parallel, or a combination of series and parallel connections. The cover 320 seals the housing 310 to protect the multiple secondary batteries 1. It should be noted that, in addition to the secondary battery 1 of this utility model, the battery pack 100 may also include a battery pack thermal management system, circuit board, etc. The battery pack 100 can be a battery module, a battery pack, an energy storage cabinet, etc.; these will not be described in detail here.

[0124] like Figure 9 As shown, this utility model also provides an electronic device 1000, which includes the aforementioned battery pack 100. A working part 300 is electrically connected to the battery pack 100 to obtain electrical power. As an example, the electronic device 1000 is a vehicle, which 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 300 is the vehicle body, and the battery pack 100 is located at the bottom of the vehicle body, providing electrical power for the vehicle's operation 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, and power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working part 300 can be a unit component capable of obtaining electrical power from the battery pack 100 and performing corresponding work, such as a fan blade rotation unit or a vacuum cleaner suction unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, 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 does not impose any special limitations on the aforementioned electronic device 1000.

[0125] While specific embodiments of this utility model have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this utility model is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this utility model, but all such changes and modifications fall within the scope of protection of this utility model.

Claims

1. A secondary battery characterized by comprising: It includes: a shell; an electrode assembly accommodated in the shell, the electrode assembly being formed by stacking a positive electrode sheet, a separator, and a negative electrode sheet, the electrode assembly including a first end provided with a positive electrode tab and a second end provided with a negative electrode tab, the second end to the first end being a preset direction; the positive electrode sheet includes a positive electrode current collector, a positive electrode active material layer, and an insulating layer, the positive electrode current collector includes a first positive electrode surface and a second positive electrode surface arranged along the thickness direction, the positive electrode active material layer includes a first positive electrode active material layer and a second positive electrode active material layer, along the preset direction, the first positive electrode surface includes a first positive electrode coating area covered with the first positive electrode active material layer and a first positive electrode non-coating area not covered with the first positive electrode active material layer, and the second positive electrode surface includes a second positive electrode coating area covered with the second positive electrode active material layer and a second positive electrode non-coating area not covered with the second positive electrode active material layer; along the preset direction, the first positive electrode active material layer includes a first positive electrode flat area and a first positive electrode thinning area, and the second positive electrode active material layer includes a second positive electrode flat area and a second positive electrode thinning area; the insulating layer includes a first insulating layer and a second insulating layer, the first insulating layer covers part of the first positive electrode non-coating area and part of the first positive electrode thinning area; the second insulating layer covers part of the second positive electrode non-coating area, and along the thickness direction of the positive electrode current collector, the projection of the second insulating layer and the second positive electrode active material layer do not overlap.

2. The secondary battery according to claim 1, wherein Along the preset direction, the width of the overlapping area of the first insulating layer along the thickness direction of the positive electrode current collector and the first positive electrode thinning area is 1.5-2.5 mm.

3. The secondary battery according to claim 1, wherein Along the preset direction, the first positive electrode non-coating area includes a first positive electrode adjacent area and a first surface of the positive electrode tab protruding from the first positive electrode adjacent area, and the second positive electrode non-coating area includes a second positive electrode adjacent area and a second surface of the positive electrode tab protruding from the second positive electrode adjacent area; along the preset direction, the width of the first insulating layer on the first positive electrode adjacent area is 6.5-9.5 mm, and the width of the first insulating layer on the first surface of the positive electrode tab is 3-5 mm; and / or, along the preset direction, the width of the second insulating layer on the second positive electrode adjacent area is 5-7 mm, and the width of the second insulating layer on the second surface of the positive electrode tab is 3-5 mm.

4. The secondary battery according to claim 1, wherein Along the thickness direction of the positive electrode current collector, the thickness of the first insulating layer near one end of the first positive electrode active material layer is 60-95% of the thickness of the first positive electrode flat area; and / or, along the thickness direction of the positive electrode current collector, the thickness of the second insulating layer is 10-30% of the thickness of the second positive electrode flat area.

5. The secondary battery according to claim 1, wherein along the preset direction, the width of the first positive electrode thinning area is 2-10 mm; and / or, along the preset direction, the width of the second positive electrode thinning area is 2-10 mm.

6. The secondary battery according to claim 1, wherein The first positive electrode active material layer comprises LFP; and / or, the second positive electrode active material layer comprises LFP.

7. The secondary battery according to claim 1, wherein The second insulating layer has a spacing between one end of the second positive electrode active material layer and the second positive electrode active material layer; or, The second insulating layer abuts one end of the second positive electrode active material layer.

8. The secondary battery according to any one of claims 1 to 7, wherein The secondary battery further comprises a cover plate assembly, the cover plate assembly being provided on the shell and defining a receiving cavity together with the shell, the electrode assembly being received in the receiving cavity; and / or The secondary battery is a square battery; and / or, the electrode assembly is a laminated electrode assembly.

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

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

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