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 of a winding structure formed by winding a positive plate, a diaphragm and a negative plate; a first negative electrode surface of a negative electrode current collector of the negative plate is covered with a first negative electrode active material layer, and a second negative electrode surface is covered with a second negative electrode active material layer; the negative plate comprises a negative plate starting end, a first position, a second position and a negative plate ending end along the winding direction; the group margin of the secondary battery is 94%-99%, the area between the first position and the second position is a preset area on the surface, away from the center hole, of the second negative electrode active material layer, and a first insulating layer is continuously arranged in the preset area in the winding direction. By arranging the first insulating layer, the safety problem caused by lithium separation can be avoided, and the safety performance of the secondary battery is greatly improved.

Description

Technical Field

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

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

[0003] In the development of battery technology, how to improve battery safety is a technical problem that urgently needs to be solved. Utility Model Content

[0004] The technical problem to be solved by this utility model is to overcome the above-mentioned technical problems of the prior art and provide a secondary battery, battery pack and electronic device.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution:

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

[0007] case;

[0008] An electrode assembly is housed within the housing, and the electrode assembly is a wound structure formed by stacking and winding a positive electrode sheet, a separator, and a negative electrode sheet.

[0009] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector includes a first negative electrode surface and a second negative electrode surface disposed along the thickness direction. The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer. The first negative electrode active material layer covers a portion of the first negative electrode surface, and the second negative electrode active material layer covers a portion of the second negative electrode surface. The first negative electrode surface is disposed radially toward the center hole of the winding structure.

[0010] Along the winding direction of the winding structure, the negative electrode sheet sequentially includes a negative electrode sheet start end, a first position, a second position, and a negative electrode sheet end end; the positive electrode sheet sequentially includes a positive electrode sheet start end and a positive electrode sheet end end. No positive electrode sheet is correspondingly disposed on the side away from the central hole from the first position through the second position to the negative electrode sheet end end. Along the radial direction of the winding structure, the first position and the second position are respectively located on the line connecting the center point of the positive electrode sheet end end and the center hole, and on the extension line of the connecting line, and both the first position and the second position are adjacent to the positive electrode sheet end end.

[0011] The secondary battery has a group margin of 94%-99%. The second negative electrode active material layer is located on the surface away from the central hole, and the area between the first position and the second position is a preset area. The preset area is continuously provided with a first insulating layer along the winding direction.

[0012] In this technical solution, by continuously setting a first insulating layer along the winding direction in a preset area, lithium ions can be prevented from diffusing from the preset area of ​​the negative electrode sheet to the outside of the area away from the central hole, thus avoiding lithium deposition on the surface of the outermost second negative electrode active material layer away from the central hole, avoiding safety problems caused by lithium deposition, and greatly improving the safety performance of the secondary battery.

[0013] Preferably, one side of the first insulating layer extends beyond or aligns with the side of the second negative electrode active material layer near the positive electrode tab along the width direction;

[0014] The group margin is the ratio of the maximum diameter of the electrode assembly to the maximum diameter of the housing when the secondary battery is fully discharged.

[0015] Preferably, along the height direction of the winding structure, the width of the first insulating layer is 12.5%-37.5% of the width of the preset region; or,

[0016] The area of ​​the first insulating layer is 4%-10% of the area of ​​the preset region.

[0017] Preferably, the first insulating layer is at least partially disposed on the surface of the second negative electrode active material layer opposite to the central hole, between the second position and the end of the negative electrode sheet.

[0018] Preferably, the first insulating layer includes a first substrate and a first adhesive layer located on the surface of the first substrate, wherein the material of the first substrate is PET or PI; and / or,

[0019] The number of the first insulating layers located in the preset area is one.

[0020] Preferably, the outermost ring of the electrode assembly further includes an insulating film, and the orthographic projections of the insulating film and the first insulating layer do not overlap along the radial direction of the winding structure;

[0021] The insulating film includes a second substrate and a second adhesive layer located on the surface of the second substrate, wherein the material of the second substrate is PET or PI.

[0022] Preferably, the positive electrode sheet includes a positive current collector, and along the height direction of the winding structure, the positive current collector includes a positive electrode coated area covered by the positive electrode active material layer and a positive electrode uncoated area not covered by the positive electrode active material layer; the negative electrode current collector includes a negative electrode coated area covered by the negative electrode active material layer and a negative electrode uncoated area not covered by the negative electrode active material layer.

[0023] The uncoated positive electrode region includes a positive electrode tab and a positive electrode connection region connecting the positive electrode tab and the coated positive electrode region; the uncoated negative electrode region includes a negative electrode tab and a negative electrode connection region connecting the negative electrode tab and the coated negative electrode region.

[0024] Wherein, at least a portion of the positive electrode connection region is covered by a second insulating layer; and / or, at least a portion of the negative electrode connection region is covered by a third insulating layer.

[0025] Preferably, the housing includes a surrounding sidewall, one end of which is formed with an opening; the end of the housing near the opening includes a press-fit portion recessed into the housing.

[0026] The secondary battery also includes:

[0027] Cover plate, installed in the opening;

[0028] An insulating seal is provided around the periphery of the cover plate to insulate and seal the cover plate and the housing;

[0029] A collector plate is disposed between the electrode assembly and the cover plate and is electrically connected to the housing. The connecting piece of the collector plate is located on the side of the crimping part facing the electrode assembly and is welded to the crimping part.

[0030] And / or,

[0031] The secondary battery is a cylindrical battery;

[0032] And / or,

[0033] The maximum diameter of the housing is 40mm-50mm, and when the secondary battery is fully discharged, the minimum distance between the outer periphery of the electrode assembly and the inner surface of the housing ranges from 0.2mm to 0.8mm.

[0034] A battery pack characterized in that it includes a secondary battery as described above.

[0035] An electronic device characterized in that it includes a battery pack as described above.

[0036] The positive and progressive effects of this utility model are as follows:

[0037] When the group margin of the secondary battery is 94%-99%, since the outermost negative electrode (the area from the first position through the second position to the end of the negative electrode) does not have a positive electrode on the side away from the central hole, there is no corresponding positive electrode active material layer. At this time, because the group margin is large, the distance between the outermost negative electrode and the inner surface of the casing is relatively short. During the expansion process of battery charging and discharging, lithium ions will jump from the positive electrode active material layer of the outermost positive electrode to the outside of the outermost negative electrode, causing lithium plating safety issues.

[0038] The first and second positions of the negative electrode are both located on the connecting line between the end of the positive electrode and the center hole, and both positions are adjacent to the end of the positive electrode. Since the first and second positions are sequentially arranged on the negative electrode along the winding direction, and the first and second positions are respectively located on the connecting line between the end of the positive electrode and the center hole, and on the extension line of the connecting line, the first and second positions are radially adjacent to the end of the positive electrode. That is, the first position is located on the connecting line between the center point of the end of the positive electrode and the center hole, and is located adjacent to the side of the end of the positive electrode closer to the center hole; the second position is located on the extension line of the connecting line between the end of the positive electrode and the center hole, and is located adjacent to the side of the end of the positive electrode away from the center hole; the negative electrode is wound from the first position to the second position to form a complete loop.

[0039] This invention prevents lithium ions from diffusing from the predetermined area of ​​the negative electrode sheet to the outer side away from the central hole by continuously setting a first insulating layer on the surface of the second negative electrode active material layer away from the central hole in a predetermined region between the first and second positions. This avoids lithium deposition on the outermost surface of the second negative electrode active material layer away from the central hole, thus preventing safety issues caused by lithium deposition and greatly improving the safety performance of the secondary battery. Specifically, the second negative electrode active material layer covers a portion of the second negative electrode surface of the negative electrode current collector, and along the radial direction of the winding structure, the second negative electrode surface is located on the side of the negative electrode current collector away from the central hole of the winding structure. Attached Figure Description

[0040] Figure 1 This is a cross-sectional view of a secondary battery according to a preferred embodiment of the present invention.

[0041] Figure 2 for Figure 1 A magnified schematic diagram of part A in the middle.

[0042] Figure 3 for Figure 1 A magnified schematic diagram of part B in the middle section.

[0043] Figure 4This is a three-dimensional structural diagram of the electrode assembly of a secondary battery according to a preferred embodiment of the present invention.

[0044] Figure 5 This is a cross-sectional view of the electrode assembly of a secondary battery according to a preferred embodiment of the present invention.

[0045] Figure 6 for Figure 5 A magnified schematic diagram of part C in the middle.

[0046] Figure 7 This is a partial cross-sectional view of the electrode assembly of a secondary battery according to a preferred embodiment of the present invention.

[0047] Figure 8 for Figure 7 A magnified schematic diagram of part E in the middle section.

[0048] Figure 9 for Figure 7 A magnified schematic diagram of part F in the middle section.

[0049] Figure 10 This is a partial cross-sectional view of a single-turn positive electrode sheet of a secondary battery according to a preferred embodiment of the present invention.

[0050] Figure 11 This is a partial cross-sectional view of a single-turn negative electrode sheet of a secondary battery according to a preferred embodiment of the present invention.

[0051] Figure 12 This is a partial structural diagram of the negative electrode sheet of a secondary battery according to a preferred embodiment of the present invention when unfolded.

[0052] Figure 13 This is a schematic diagram of the battery pack structure according to a preferred embodiment of the present invention.

[0053] Figure 14 This is a schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention.

[0054] Explanation of reference numerals in the attached figures

[0055] Electronic devices 1000

[0056] Battery pack 100

[0057] Work Department 300

[0058] Box 310

[0059] Box lid 320

[0060] Secondary battery 1

[0061] Casing 10

[0062] Side wall 11

[0063] Opening 12

[0064] end wall 13

[0065] Receiving cavity 14

[0066] Electrode assembly 20

[0067] 201 winding structure

[0068] Center Hole 2011

[0069] Positive electrode 21

[0070] Positive current collector 211

[0071] Positive electrode active material layer 2111

[0072] Positive electrode coating area 212

[0073] Uncoated region 213 of positive electrode

[0074] Positive electrode 2131

[0075] Positive connection region 2132

[0076] Positive electrode starting end 217

[0077] Positive electrode end 218

[0078] Diaphragm 22

[0079] Diaphragm initiation end 221

[0080] Diaphragm end 222

[0081] Negative electrode 23

[0082] Negative current collector 231

[0083] First negative electrode surface 23101

[0084] Second negative electrode surface 23102

[0085] Negative electrode active material layer 2311

[0086] First negative electrode active material layer 23111

[0087] Second negative electrode active material layer 23112

[0088] Negative electrode coating area 232

[0089] Uncoated area of ​​negative electrode 233

[0090] Negative electrode tab 2331

[0091] Negative electrode connection region 2332

[0092] negative electrode starting end 235

[0093] First position 236

[0094] Second position 237

[0095] negative electrode end 238

[0096] First insulating layer 25

[0097] First side 251

[0098] Second side 252

[0099] Second insulating layer 26

[0100] Third insulating layer 27

[0101] Insulating film 28

[0102] crimping part 30

[0103] Cover plate 40

[0104] Insulating seal 50

[0105] First Collector Disk 61

[0106] Second collection disk 62

[0107] 70 pole

[0108] Insulating component 80

[0109] Preset area K

[0110] The winding direction P of the wound structure

[0111] Radial R of the wound structure Detailed Implementation

[0112] The present invention will be described more clearly and completely below with reference to the accompanying drawings, using a preferred embodiment.

[0113] like Figures 1 to 3 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.

[0114] like Figures 4 to 12 As shown, the electrode assembly 20 is a wound structure 201 formed by stacking and winding a positive electrode 21, a separator 22 and a negative electrode 23.

[0115] The negative electrode sheet 23 includes a negative electrode current collector 231 and a negative electrode active material layer 2311. The negative electrode current collector 231 includes a first negative electrode surface 23101 and a second negative electrode surface 23102 disposed along the thickness direction. The negative electrode active material layer 2311 includes a first negative electrode active material layer 23111 and a second negative electrode active material layer 23112. The first negative electrode active material layer 23111 covers a portion of the first negative electrode surface 23101, and the second negative electrode active material layer 23112 covers a portion of the second negative electrode surface 23102. The first negative electrode surface 23101 is disposed toward the central hole 2011 of the winding structure 201 along the radial direction R of the winding structure 201, and the second negative electrode surface 23102 is disposed away from the central hole 2011.

[0116] Along the winding direction P of the winding structure 201, the negative electrode 23 sequentially includes a negative electrode starting end 235, a first position 236, a second position 237, and a negative electrode ending end 238. The positive electrode 21 sequentially includes a positive electrode starting end 217 and a positive electrode ending end 218. No positive electrode 21 is correspondingly provided on the side away from the central hole 2011 from the first position 236 through the second position 237 to the negative electrode ending end 238. Along the radial direction R of the winding structure 201, the first position 236 and the second position 237 are respectively located on the connecting line between the center point of the positive electrode ending end 218 and the center hole 2011, and on the extension line of the connecting line. Both the first position 236 and the second position 237 are adjacent to the positive electrode ending end 218.

[0117] The secondary battery 1 has a group margin of 94%-99%. The second negative electrode active material layer 23112 is located on the surface away from the central hole 2011, and the area between the first position 236 and the second position 237 is a preset area K. The preset area K is continuously provided with a first insulating layer 25 along the winding direction P.

[0118] It should be noted that when the group margin of the secondary battery 1 is 94%-99%, since the outermost negative electrode 23 (the area of ​​the negative electrode 23 from the first position 236 through the second position 237 to the negative electrode end 238) does not have a positive electrode 21 on the side away from the central hole 2011, there is no corresponding positive electrode active material layer 2111. At this time, because the group margin is large, the distance between the outermost negative electrode 23 and the inner surface of the casing 10 is relatively small. During the expansion process of battery charging and discharging, lithium ions will jump from the positive electrode active material layer 2111 of the outermost positive electrode 21 to the outside of the outermost negative electrode 23, causing lithium plating safety issues. Furthermore, since the first position 236 and the second position 237 are sequentially arranged on the negative electrode 23 along the winding direction P, and the first position 236 and the second position 237 are respectively located on the connecting line between the positive electrode end 218 and the center hole 2011, and on the extension line of the connecting line, the first position 236 and the second position 237 are both adjacent to the positive electrode end 218 in the radial direction R. That is, the first position 236 is located on the connecting line between the center point of the positive electrode end 218 and the center hole 2011, and is located adjacent to the side of the positive electrode end 218 closer to the center hole; the second position 237 is located on the extension line of the connecting line between the positive electrode end 218 and the center hole 2011, and is located adjacent to the side of the positive electrode end 218 away from the center hole; the first position 236 to the second position 237 of the negative electrode 23 are wound to form a complete loop.

[0119] This embodiment, by continuously providing a first insulating layer 25 along the winding direction P in a preset region K, prevents lithium ions from diffusing to the outer side of the preset region K away from the central hole 2011, thus avoiding lithium deposition on the surface of the outermost second negative electrode active material layer 23112 away from the central hole 2011, preventing safety issues caused by lithium deposition, and greatly improving the safety performance of the secondary battery 1. The first position 236 to the second position 237 of the negative electrode sheet 23 refers to all positions including the first position 236, the second position 237, and all positions between the first position 236 and the second position 237. The second negative electrode surface 23102 of the negative electrode current collector 231 is positioned away from the central hole 2011, that is, the second negative electrode surface 23102 faces the housing 10.

[0120] It should also be noted that the outermost negative electrode 23 may have one or more turns. Regardless of whether it is one or more turns, as long as the first insulating layer 25 is continuously provided along the winding direction P in the preset region K closest to the positive electrode end 218, it can prevent lithium ions from diffusing into the preset region K to the outside of that region away from the central hole 2011. For turns farther from the positive electrode end 218, the probability of lithium ions jumping over is low due to the greater distance. Furthermore, regardless of whether the first insulating layer 25 is located in the middle of the second negative electrode active material layer 23112 along the height direction in the preset region K, or near the edge of the second negative electrode active material layer 23112, as long as the first insulating layer 25 is continuously provided along the winding direction P in the preset region K, it can form an insulating structure continuously provided along the winding direction P, thereby preventing lithium ions from diffusing into the preset region K to the outside of that region away from the central hole 2011.

[0121] Furthermore, on the surface of the second negative electrode active material layer 23112 opposite to the central hole 2011, at least partially between the second position 237 and the negative electrode end 238, a first insulating layer 25 is provided to prevent lithium ions from diffusing from the region between the second position 237 and the negative electrode end 238 of the negative electrode 23 to the outside of that region away from the central hole 2011. This further reduces the amount of lithium removed from the corresponding region of the positive electrode 21. The region between the second position 237 and the negative electrode end 238 includes the second position 237, the negative electrode end 238, and all positions located between them.

[0122] The number of first insulating layers 25 located in the preset region K is one. That is, the number of first insulating layers 25 provided in the region between the first position 236 and the second position 237 on the surface of the second negative electrode active material layer 23112 away from the central hole 2011, is one, so that the first insulating layer 25 is a continuous integral structure to ensure its continuous insulation performance along the winding direction P.

[0123] Furthermore, in this embodiment, the first insulating layer 25 disposed between the second position 237 and the negative electrode terminal 238 is a continuous structure and is connected to the first insulating layer 25 disposed within the preset region K, thereby forming a continuous integral structure. This continuous integral structure starts from the first position 236, passes through the second position 237, and ends at the position before the negative electrode terminal 238; that is, the number of first insulating layers 25 is one. This integral structure, starting from the first position 236 and ending at the negative electrode terminal 238, is wound at least one turn. In other embodiments, the ending position of the first insulating layer 25 may also coincide with the negative electrode terminal 238.

[0124] However, it is not limited to this. In other embodiments, the first insulating layer 25 provided only between the second position 237 and the negative electrode end 238 may be a multi-segment structure with intervals.

[0125] Preferably, one side of the first insulating layer 25 along its width direction (denoted as the first side 251) extends beyond or aligns with the side of the second negative electrode active material layer 23112 near the positive electrode tab 2131, and the other side of the first insulating layer along its width direction (denoted as the second side 252) extends toward the other side of the second negative electrode active material layer 23112. This better prevents lithium ions from diffusing in the preset region K to the outside of that region away from the central hole 2011, thereby reducing the amount of lithium stripping from the positive electrode sheet 21 in the corresponding region, thus avoiding safety problems caused by lithium plating and greatly improving the safety performance of the secondary battery. The width direction of the first insulating layer 25 is in the same direction as the height direction H of the winding structure 201. Similarly, the first insulating layer 25 located between the second position 237 and the negative electrode sheet termination end 238 also has its first side 251 extending beyond or aligning with the side of the second negative electrode active material layer 23112 near the positive electrode tab 2131, and its second side 252 extending toward the other side of the second negative electrode active material layer 23112.

[0126] Please refer to the following: Figure 5 The outermost ring of the electrode assembly 20 also includes an insulating film 28. Along the radial direction R of the winding structure 201, the orthographic projections of the insulating film 28 and the first insulating layer 25 do not overlap. That is, along the height direction H of the winding structure 201, a portion of the winding structure 201 is covered by the insulating film 28, and the insulating film 28 and the first insulating layer 25 are staggered to avoid the superposition of the electrode assembly 20's thickness, which would affect the diameter of the electrode assembly 20, thereby improving the energy density. Furthermore, the insulating film 28 also serves to fix the outer ring diaphragm 22, preventing the diaphragm 22 from loosening. The insulating film 28 can be synthesized from PP, PE, PET, PVC, PI, or other polymer materials. The diaphragm 22 includes a starting end 221 and a closing end 222. The insulating film 28 includes, but is not limited to, a finishing tape used to fix the closing end of the diaphragm 22. That is, the insulating film 28 can be a finishing tape or other insulating structures, such as a Mylar film. Regardless of the structure of the insulating film 28, its radial R along the winding structure 201 and its orthographic projection along the first insulating layer 25 do not overlap.

[0127] Please refer to the following: Figure 12Specifically, along the height direction H of the winding structure 201, the width h1 of the first insulating layer 25 is 5mm-15mm, for example, it can be 5mm, 7mm, 10mm, 13.5mm, or 15mm. By setting the range of the width h1 of the first insulating layer 25, on the one hand, it avoids the width h1 of the first insulating layer 25 being too large, which would affect the energy density of the battery; on the other hand, it avoids the width h1 of the first insulating layer 25 being too small, which would fail to prevent lithium-ion diffusion.

[0128] Along the height direction H of the winding structure 201, the width h1 of the first insulating layer 25 is 12.5%-37.5% of the width h2 of the preset region K, for example, it can be 12.5%, 17.5%, 25%, 30%, or 37.5%. In this way, by setting the relationship between the width h1 of the first insulating layer 25 and the width h2 of the preset region K, on ​​the one hand, the width h1 of the first insulating layer 25 is avoided from being too large, which would affect the energy density of the battery; on the other hand, the width h1 of the first insulating layer 25 is avoided from being too small, which would prevent lithium-ion diffusion.

[0129] The area of ​​the first insulating layer 25 is 4%-10% of the area of ​​the preset region K, for example, it can be 12.5%, 17.5%, 25%, 30%, or 37.5%. In this way, by setting the relationship between the area of ​​the first insulating layer 25 and the area of ​​the preset region K, on ​​the one hand, it avoids the first insulating layer 25 being too large, which would affect the energy density of the battery; on the other hand, it avoids the first insulating layer 25 being too small, which would fail to prevent lithium-ion diffusion.

[0130] The thickness t of the first insulating layer 25 is between 10μm and 65μm, for example, it can be 10μm, 25μm, 37.5μm, 53.5μm, or 65μm. By setting the range of the thickness t of the first insulating layer 25, on the one hand, it avoids the thickness t of the first insulating layer 25 being too large, which would affect the energy density of the battery; on the other hand, it avoids the thickness t of the first insulating layer 25 being too small, which would fail to prevent lithium-ion diffusion.

[0131] In this embodiment, the first insulating layer 25 includes a first substrate and a first adhesive layer on the surface of the first substrate. The material of the first substrate is PET (Polyethylene terephthalate). However, it is not limited to this. In other embodiments, the material of the first substrate of the first insulating layer 25 may also be other insulating materials, such as PI (Polyimide). The insulating film 28 includes a second substrate and a second adhesive layer on the surface of the second substrate. The material of the second substrate is PET or PI.

[0132] When secondary battery 1 is fully discharged, the group margin is the ratio of the maximum diameter of electrode assembly 20 to the maximum inner diameter of housing 10, where the inner diameter of housing 10 is the diameter of the cavity inside housing 10. The fully discharged state refers to the state where the secondary battery's SOC is close to 0%. SOC (State of Charge) refers to the battery's state of charge, specifically the percentage of usable capacity that can be released under specified discharge conditions. Usable capacity refers to the maximum amount of electricity a battery can release under specified charge and discharge conditions, i.e., the remaining charge of the battery. Secondary battery 1 is fully discharged when its SOC is 0%. However, in some batteries, the SOC may be slightly greater than 0% during full discharge; in this case, the state of charge slightly greater than 0% is considered the fully discharged state of the secondary battery. For pre-made rechargeable batteries, the empty state is the rated capacity known from the nameplate of rechargeable battery 1 at the factory. Then, rechargeable battery 1 is first charged to a full state at a charging rate of 0.33C. Charging is considered complete when the charging current decreases to 0.01C, indicating a fully charged state (e.g., the state corresponding to when rechargeable battery 1 can be charged to its rated capacity). The fully discharged state is the state when rechargeable battery 1 has released its rated capacity as displayed. The discharge rate can be selected as 0.33C. For example, for a 42Ah cylindrical battery, a charging current of 0.33C can be selected. Charging is stopped when the current decreases to 0.01C (i.e., charging is considered complete). Then, it is discharged externally at a rate of 0.33C. When the 42Ah capacity is released, the state is considered fully discharged. In some specific experiments, in order to quickly determine the empty state, for secondary batteries containing silicon anodes, the cutoff voltage can be 2.5V to indicate the empty state, while for anodes containing only carbon materials, the cutoff voltage can be 2.75V to indicate the empty state.

[0133] Preferably, the positive electrode 21 includes a positive current collector 211. Along the height direction H of the winding structure 201, the positive current collector 211 includes a positive electrode coated region 212 covered by the positive electrode active material layer 2111 and a positive electrode uncoated region 213 not covered by the positive electrode active material layer 2111. The negative current collector 231 includes a negative electrode coated region 232 covered by the negative electrode active material layer 2311 and a negative electrode uncoated region 233 not covered by the negative electrode active material layer 2311. The positive electrode uncoated region 213 includes a positive electrode tab 2131 and a positive electrode connection region 2132 connecting the positive electrode tab 2131 and the positive electrode coated region 212. The negative electrode uncoated region 233 includes a negative electrode tab 2331 and a negative electrode connection region 2332 connecting the negative electrode tab 2331 and the negative electrode coated region 232. At least a portion of the positive electrode connection region 2132 is covered by a second insulating layer 26; at least a portion of the negative electrode connection region 2332 is covered by a third insulating layer 27.

[0134] Thus, by providing the second insulating layer 26, the risk of deformation of the positive electrode connection region 2132 can be reduced, and the insulation performance of the positive electrode connection region 2132 can be improved, thereby significantly improving the safety and reliability of battery performance. Similarly, by providing the third insulating layer 27, the risk of deformation of the negative electrode connection region 2332 can be reduced, and the insulation performance of the negative electrode connection region 2332 can be improved, thereby significantly improving the safety and reliability of battery performance. The second insulating layer 26 and the first insulating layer 25 at least partially overlap at their corresponding radial R positions, making the area more compact. This prevents misalignment of the positive electrode plate 21 and the negative electrode plate 23 during battery vibration operation, avoiding contact between the positive electrode plate 21 and the negative electrode plate 23, which could cause a short circuit and improve safety.

[0135] In other embodiments, at least a portion of the positive electrode connection region 2132 may be covered by the second insulating layer 26, or at least a portion of the negative electrode connection region 2332 may be covered by the third insulating layer 27.

[0136] Specifically, the positive electrode connection region 2132 includes a first side facing away from the central hole 2011 along the radial direction R of the wound structure 201 and a second side facing the central hole 2011. At least a portion of both the first and second sides is covered with a second insulating layer 26. Thus, by covering at least a portion of both the first and second sides of the positive electrode connection region 2132 with the second insulating layer 26, the risk of deformation of the positive electrode connection region 2132 can be effectively reduced, and the insulation performance of the positive electrode connection region 2132 can be improved, thereby significantly improving the safety and reliability of the battery performance. The second insulating layer 26 mainly consists of boehmite and PVDF (polyvinylidene fluoride). Boehmite accounts for 80%; PVDF accounts for 20%. The thickness of the second insulating layer 26 is 1.5μm-2.5μm, for example, it can be 1.5μm, 1.7μm, 2μm, 2.1μm, 2.3μm, or 2.5μm. By setting the thickness range of the second insulating layer 26, it is possible to avoid the second insulating layer 26 being too thin, which would make it difficult to obtain the required electrical insulation and support strength; at the same time, it is also possible to avoid the second insulating layer 26 being too thick, which would lead to a longer curing time for the coating layer and an increase in the overall thickness of the structure. Preferably, the thickness of the second insulating layer 26 is 2 μm.

[0137] Please refer to the following: Figure 10 In this embodiment, both the first and second sides of the positive electrode connection region 2132 are covered with the second insulating layer 26. However, this is not a limitation. In other embodiments, only the first side of the positive electrode connection region 2132 may be covered with the second insulating layer 26, or only the second side of the positive electrode connection region 2132 may be covered with the second insulating layer 26. Adjustments can be made according to design requirements.

[0138] The second insulating layer 26 includes a color developer to distinguish whether the side coated with the second insulating layer 26 is the front or back side of the positive electrode 21 through the color development effect of the color developer, including but not limited to distinguishing the areal density of the front and back sides of the positive electrode 21. The main component of the color developer is bismuth vanadate, and its color is yellow.

[0139] In this embodiment, the second side of the positive electrode connection region 2132 may be covered with a second insulating layer 26 containing a color developer, and the second insulating layer 26 containing the color developer is yellow; the first side of the positive electrode connection region 2132 may be covered with a second insulating layer 26 without a color developer, and the second insulating layer 26 without a color developer is white, so that the front and back of the positive electrode sheet 21 are different in color, thereby achieving the ability to quickly distinguish the front and back of the positive electrode sheet 21 by utilizing the color development effect of the color developer in the second insulating layer 26.

[0140] Furthermore, since the first insulating layer 25 is usually a color different from white, such as blue, yellow, or green, it can form a good color difference with the second insulating layer 26, which is yellow and contains a color developer and is located at the end 218 of the positive electrode sheet. This makes it easier for the CCD to accurately identify the edge of the first insulating layer 25, effectively preventing the risk of missing the first insulating layer 25 and thus ensuring the yield rate.

[0141] Please refer to the following: Figures 1 to 3 In this embodiment, the housing 10 includes a surrounding sidewall 11, one end of which has an opening 12; the end of the housing 10 near the opening 12 includes a crimping portion 30 recessed into the housing 10. The secondary battery 1 also includes a cover plate 40, an insulating seal 50, and a current collector. The cover plate 40 is mounted on the opening 12. The insulating seal 50 surrounds the periphery of the cover plate 40 to insulate and seal the cover plate 40 and the housing 10. The current collector is disposed between the electrode assembly 20 and the cover plate 40 and is electrically connected to the housing 10. The connecting piece of the current collector is located on the side of the crimping portion 30 facing the electrode assembly 20 and is welded to the crimping portion 30. In this way, by setting the connecting piece of the current collector plate to be located on the side of the crimping part 30 facing the electrode assembly 20 and welded to the crimping part 30, that is, the welding area of ​​the current collector plate and the electrode tab is located at the end closer to the electrode assembly 20 than the crimping part 30, the influence of the crimping part 30 on the welding area of ​​the electrode tab and the current collector plate can be prevented, thereby improving the welding strength of the electrode tab and the current collector plate.

[0142] Furthermore, the housing 10 also includes an end wall 13, and a side wall 11 is disposed around the end wall 13 and located at the end of the side wall 11 away from the opening 12. The end wall 13 and the side wall 11 enclose a receiving cavity 14 within the housing 10 for accommodating the electrode assembly 20, electrolyte, and other necessary battery components. The connection between the end wall 13 and the side wall 11 can be achieved in various ways, such as integral stamping, integral casting, or separate welding.

[0143] The secondary battery 1 also includes a terminal post 70, which passes through the end wall 13 and is insulated from the end wall 13 by an insulating member 80.

[0144] The current collector includes a first current collector 61 and a second current collector 62. The first current collector 61 is disposed between the electrode assembly 20 and the end wall 13; the second current collector 62 is disposed between the electrode assembly 20 and the cover plate 40. In this embodiment, the first current collector 61 corresponds to the positive electrode tab 2131, and the positive electrode tab 2131 is electrically connected to the electrode post 70 through the first current collector 61; the second current collector 62 corresponds to the negative electrode tab 2331, and the negative electrode tab 2331 is electrically connected to the housing 10 through the second current collector 62. However, this is not a limitation. In other embodiments, the first current collector 61 may correspond to the negative electrode tab 2331, and the second current collector 62 may correspond to the positive electrode tab 2131.

[0145] In this embodiment, the welding sequence of the first current collector 61 and the second current collector 62 of the secondary battery 1 to the electrode assembly 20 is as follows: First, place the first current collector 61; then, press the electrode assembly 20 together on both the positive and negative sides (the pressing process can increase the contact between the current collector and the electrode assembly 20 and avoid poor welding); the first current collector 61 is welded using line welding instead of spot welding. This is because the negative electrode tab 2331 is relatively soft, and after two pressings, the second current collector 62 and the electrode assembly 20 will be closer together. Spot welding would cause the diaphragm 22 to be burned due to concentrated heat. Wire welding, with less heat, can avoid burning the diaphragm 22 and causing a short circuit between the positive and negative electrodes; next, place the second current collector 62; press the electrode assembly 20 together on both the positive and negative sides again; finally, weld the second current collector 62.

[0146] In this embodiment, the secondary battery 1 is a cylindrical battery. Cylindrical batteries have advantages such as high energy density, long cycle life, and good safety performance. However, it is not limited to this; in other embodiments, the secondary battery 1 can also be a prismatic battery or other shaped batteries.

[0147] Applying the specific structure of the first insulating layer 25 in this embodiment to a cylindrical battery can prevent lithium ions from diffusing from the preset region K of the negative electrode 23 to the outside of that region away from the central hole 2011, thereby reducing the amount of lithium de-lithiation of the corresponding positive electrode 21, thus avoiding safety problems caused by lithium plating and greatly improving the safety performance of the secondary battery.

[0148] In particular, since the cylindrical electrode assembly 20 of the cylindrical battery aims for the ultimate energy density, the electrode sheets will expand to some extent, thus reducing the electrode layer spacing. Furthermore, since the casing 10 of the cylindrical battery is usually made of high-strength steel, the cylindrical steel casing exerts a greater constraint on the electrode assembly 20 compared to casings made of other materials, which further leads to a smaller electrode layer spacing, making it easier for lithium plating to occur. The design of the first insulating layer 25 in this embodiment can prevent lithium ions from diffusing from the preset region K of the negative electrode 23 to the outside of that region away from the central hole 2011, which can better address the problem of lithium plating in cylindrical batteries due to the small electrode layer spacing and improve its safety.

[0149] Specifically, the maximum diameter of the casing 10 is 40mm-50mm. When the secondary battery 1 is fully discharged, the minimum distance between the outer periphery of the electrode assembly 20 and the inner surface of the casing 10 ranges from 0.2mm to 0.8mm. As mentioned above, on the one hand, since the cylindrical electrode assembly 20 of the cylindrical battery aims for maximum energy density, the assembly gap cannot be too large. Therefore, under the condition that the maximum diameter of the casing 10 is 40mm-50mm, the minimum distance between the outer periphery of the electrode assembly 20 and the inner surface of the casing 10 is controlled to be less than or equal to 0.8mm to avoid the electrode assembly 20 being too small and affecting the energy density of the secondary battery. On the other hand, if the minimum distance between the outer periphery of the electrode assembly 20 and the inner surface of the casing 10 is less than 0.2mm, not only will the lithium plating on the outermost negative electrode 23 be more severe, but also, during the assembly process, due to the small assembly gap and the high requirement for the electrode assembly 20 to be inserted into the casing, poor insertion into the casing is likely to occur. As can be seen from the above, by controlling the minimum distance between the outer periphery of the electrode assembly 20 and the inner surface of the housing 10 to be within the range of 0.2mm-0.8mm, the secondary battery 1 can achieve the optimal energy density while meeting the assembly gap requirements.

[0150] like Figure 13As 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 connected in series or 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.

[0151] like Figure 14 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.

[0152] 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 in that, It includes: case; An electrode assembly is housed within the housing, and the electrode assembly is a wound structure formed by stacking and winding a positive electrode sheet, a separator, and a negative electrode sheet. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector includes a first negative electrode surface and a second negative electrode surface disposed along the thickness direction. The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer. The first negative electrode active material layer covers a portion of the first negative electrode surface, and the second negative electrode active material layer covers a portion of the second negative electrode surface. The first negative electrode surface is disposed radially toward the center hole of the winding structure. Along the winding direction of the winding structure, the negative electrode sheet sequentially includes a negative electrode sheet start end, a first position, a second position, and a negative electrode sheet end end; the positive electrode sheet sequentially includes a positive electrode sheet start end and a positive electrode sheet end end. No positive electrode sheet is correspondingly disposed on the side away from the central hole from the first position through the second position to the negative electrode sheet end end. Along the radial direction of the winding structure, the first position and the second position are respectively located on the line connecting the center point of the positive electrode sheet end end and the center hole, and on the extension line of the connecting line, and both the first position and the second position are adjacent to the positive electrode sheet end end. The secondary battery has a group margin of 94%-99%. The second negative electrode active material layer is located on the surface away from the central hole, and the area between the first position and the second position is a preset area. The preset area is continuously provided with a first insulating layer along the winding direction.

2. The secondary battery as described in claim 1, characterized in that, The first insulating layer extends beyond or aligns with the side of the second negative electrode active material layer near the positive electrode tab along its width direction. The group margin is the ratio of the maximum diameter of the electrode assembly to the maximum diameter of the housing when the secondary battery is fully discharged.

3. The secondary battery as described in claim 2, characterized in that, Along the height direction of the winding structure, the width of the first insulating layer is 12.5%-37.5% of the width of the preset region; or, The area of ​​the first insulating layer is 4%-10% of the area of ​​the preset region.

4. The secondary battery as described in claim 2, characterized in that, The first insulating layer is at least partially disposed on the surface of the second negative electrode active material layer opposite to the central hole, between the second position and the end of the negative electrode sheet.

5. The secondary battery as described in claim 1, characterized in that, The first insulating layer includes a first substrate and a first adhesive layer located on the surface of the first substrate, wherein the material of the first substrate is PET or PI; and / or, The number of the first insulating layers located in the preset area is one.

6. The secondary battery as described in claim 1, characterized in that, The outermost ring of the electrode assembly also includes an insulating film, and the orthographic projections of the insulating film and the first insulating layer do not overlap along the radial direction of the winding structure. The insulating film includes a second substrate and a second adhesive layer located on the surface of the second substrate, wherein the material of the second substrate is PET or PI.

7. The secondary battery as described in claim 1, characterized in that, The positive electrode sheet includes a positive current collector. Along the height direction of the winding structure, the positive current collector includes a positive electrode coated area covered by the positive electrode active material layer and a positive electrode uncoated area not covered by the positive electrode active material layer. The negative current collector includes a negative electrode coated area covered by the negative electrode active material layer and a negative electrode uncoated area not covered by the negative electrode active material layer. The uncoated positive electrode region includes a positive electrode tab and a positive electrode connection region connecting the positive electrode tab and the coated positive electrode region; the uncoated negative electrode region includes a negative electrode tab and a negative electrode connection region connecting the negative electrode tab and the coated negative electrode region. Wherein, at least a portion of the positive electrode connection region is covered by a second insulating layer; and / or, at least a portion of the negative electrode connection region is covered by a third insulating layer.

8. The secondary battery as described in claim 1, characterized in that, The housing includes a surrounding sidewall, one end of which is formed with an opening; the end of the housing near the opening includes a press-fit portion recessed into the housing. The secondary battery also includes: Cover plate, installed in the opening; An insulating seal is provided around the periphery of the cover plate to insulate and seal the cover plate and the housing; A collector plate is disposed between the electrode assembly and the cover plate and is electrically connected to the housing. The connecting piece of the collector plate is located on the side of the crimping part facing the electrode assembly and is welded to the crimping part. And / or, The secondary battery is a cylindrical battery; And / or, The maximum diameter of the housing is 40mm-50mm, and when the secondary battery is fully discharged, the minimum distance between the outer periphery of the electrode assembly and the inner surface of the housing ranges from 0.2mm to 0.8mm.

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

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

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