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 first pole piece, a diaphragm and a second pole piece; the first pole piece comprises a first current collector, and a conductive layer and an insulating layer cover a partial region of at least one surface of the first current collector along a preset direction; the conductive layer is covered with a first active material layer, and the first active material layer at least partially covers the insulating layer; the thickness of the conductive layer is m, the thickness of the insulating layer is n, and n is smaller than or equal to m. By pre-coating the insulating layer and controlling the thickness of the insulating layer, the edges of the first active material layer and the insulating layer can be clear, and a fusion region is effectively prevented from being generated between the first active material layer and the insulating layer, so that the fixed edge is stable after lamination or winding, and the yield is greatly improved; and moreover, the thickness of the insulating layer is controlled, the material consumption is reduced, and the production cost is also effectively reduced.

Description

TECHNICAL FIELD

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

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

[0003] In the development of battery technology, how to improve the safety of battery and reduce the cost of battery is an urgent technical problem in battery technology. UTILITY MODEL CONTENTS

[0004] The utility model solves the technical problems that the prior art is to overcome the above-mentioned technical problems, provide a kind of secondary battery, battery pack and electronic device.

[0005] The utility model is to solve the above-mentioned technical problems by the following technical schemes:

[0006] A kind of secondary battery, it is characterized in that, the secondary battery includes:

[0007] Shell;

[0008] Electrode assembly, is housed in the shell, the electrode assembly is formed by the lamination of first pole piece, diaphragm and second pole piece;The first pole piece includes first current collector, and the part region of at least one side of the first current collector is covered with conductive layer and insulating layer along preset direction, the preset direction is the length direction or width direction of the first current collector;

[0009] Further, first active material layer is covered on the conductive layer, and the first active material layer at least partially covers the insulating layer, and the insulating layer is at least partially located outside the outer periphery of the first active material layer in the orthographic projection of the first current collector in thickness direction;

[0010] Supposing the thickness of the conductive layer is m, the thickness of the insulating layer is n, then n≤m.

[0011] In the technical solution, the first active material layer is coated on the conductive layer, and the first active material layer at least partially covers the insulating layer, that is, the conductive layer and the insulating layer are coated on the first current collector before the first active material layer, the insulating layer is coated in advance, and the edges of the first active material layer and the insulating layer are clear. This is because the first active material layer and the insulating layer are generally coated by extrusion, so the thickness of the insulating layer is uncontrollable, generally 15-30 μm, thereby causing the edges of the first active material layer and the insulating layer to be unclear. In the embodiment, the insulating layer is coated in advance to avoid the edges of the first active material layer and the insulating layer being unclear due to simultaneous extrusion coating, effectively avoiding fusion of the two, that is, ensuring the edges of the first active material layer to be straight, thereby the edges of the first active material layer can be accurately recognized by a CCD after the lamination or winding, the distance between the edges of the first active material layer and the edges of the second active material layer such as the separator and the second pole piece can be accurately recognized, the distance between the pole piece and the separator (the distance between the edges of the first active material layer of the first pole piece and the edges of the separator, and the distance between the edges of the first active material layer and the edges of the second active material layer of the second pole piece) is controlled, the consistency of the electrode assembly is ensured, and the yield is greatly improved. Furthermore, before the first pole piece is wound or laminated to prepare the electrode assembly, in order to improve the production rhythm and the utilization rate of the site, the first current collector is generally pre-wound into a large roll (referred to as a pole roll) before the first active material layer is coated. At this time, if m is less than n, that is, the thickness of the conductive layer is less than the thickness of the insulating layer, the hardness of the area provided with the insulating layer in the pole roll is greater than the area provided with the conductive layer, thereby causing the edges of the insulating layer to be raised, the edges of the pole roll in the radial direction from the center to the periphery are more and more inclined, the difference in the diameter of the pole roll at the positions corresponding to the conductive layer and the insulating layer is more and more large, and the first current collector is easily torn, thereby causing a safety hazard. By setting the thickness m of the conductive layer to be greater than or equal to the thickness n of the insulating layer, the edges of the pole roll in the radial direction from the center to the periphery can be kept at a relatively flat position, the edges of the insulating layer are effectively prevented from being raised, the difference in the diameter of the pole roll at the positions corresponding to the conductive layer and the insulating layer is relatively close, the first current collector is not easily torn, and the safety hazard is reduced. Therefore, when the first current collector is used to coat the first pole piece, and the first pole piece and the separator are wound or laminated, the yield of the wound and laminated electrode assembly can be greatly improved. At the same time, the thickness of the insulating layer is controlled, the material is reduced, and the production cost is effectively reduced.

[0012] Preferably, 0.5 μm≤m<1 μm.

[0013] Preferably, the insulating layer comprises inorganic insulating fillers and a binder, the mass percentage of the inorganic insulating fillers is 70-90% and the mass percentage of the binder is 10-30% based on the mass of the insulating layer.

[0014] Preferably, the cumulative volume percentage of the inorganic insulating fillers reaches 50% at a particle size D50, and the relationship between D50 and n of the inorganic insulating fillers satisfies 2≤n / D50≤5; and / or,

[0015] Preferably, the cumulative volume percentage of the inorganic insulating fillers reaches 90% at a particle size D90, and the D90 of the inorganic insulating fillers is less than 0.8 μm.

[0016] Preferably, along the preset direction, the insulating layer comprises a first area not covered by the first active material layer and a second area covered by the first active material layer, the width of the first area is w1, and the width of the second area is w2.

[0017] Preferably, 3 mm≤w1+w2≤20 mm, or 0.1≤w1 / (w1+w2)≤1.

[0018] Preferably, along the preset direction, the first active material layer comprises a flat area and a thinned area connected to each other, and the width of the thinned area is w3.

[0019] Preferably, 0

[0020] Preferably, along the preset direction, the minimum distance between the insulating layer and the conductive layer is w4, wherein 0≤w4≤1 mm.

[0021] Preferably, the first pole piece is a positive pole piece, and the first active material layer comprises lithium iron phosphate; and / or,

[0022] 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 receiving cavity, and the electrode assembly is received in the receiving cavity; and / or,

[0023] The secondary battery is a square battery; and / or, the electrode assembly is a wound electrode assembly.

[0024] Preferably, the shell comprises a surrounding side wall and an opening formed at one end of the side wall; the shell further comprises a crimping portion, the crimping portion is formed at one end of the side wall close to the opening and is recessed towards the inside of the shell.

[0025] The secondary battery further comprises:

[0026] a cover plate mounted on the opening.

[0027] an insulating seal member surrounding a periphery of the cover plate to insulate and seal the cover plate and the case;

[0028] a current collector plate disposed between the electrode assembly and the cover plate and electrically connected to the case, a connecting tab of the current collector plate being located on a side of the crimping portion facing the electrode assembly and being welded to the crimping portion;

[0029] and / or,

[0030] The secondary battery is a cylindrical battery.

[0031] A battery pack including the secondary battery as described above.

[0032] An electronic device including the battery pack as described above.

[0033] The positive progress effect of the utility model lies in:

[0034] The utility model discloses a first current collector's at least one side is covered with conductive layer and insulating layer in turn, and the first active material layer is covered on the conductive layer, and the first active material layer at least partially covers the insulating layer, that is, through pre-coating conductive layer and insulating layer, can reduce the cost, and, make the edge of first active material layer and insulating layer clear, effectively avoid the fusion area of both, that is, guarantee the edge of first active material layer straight, thereby after the lamination or winding, the CCD can accurately identify the edge of first active material layer, facilitate the accurate identification of the spacing between the edge of first active material layer and the edge of second active material layer such as diaphragm, second pole piece, guarantee the consistency of electrode assembly, greatly improve the yield rate, and through setting up the thickness m of conductive layer is greater than or equal to the thickness n of insulating layer, can make the edge radial direction of pole roll keep in the relatively flat position from the center to the periphery, effectively avoid the edge of insulating layer of pole roll before winding, thereby, the diameter difference of pole roll in the position corresponding to the conductive layer and insulating layer of pole roll is relatively close, not easy to cause the tearing of first current collector, reduce the security risk, so that when the first pole piece is coated by using the first current collector, the yield rate of winding and laminated electrode assembly can be greatly improved when the first pole piece and diaphragm are wound or laminated. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is the three-dimensional explosion structure schematic view of secondary battery of a preferred embodiment of the utility model.

[0036] Figure 2 It is the partial three-dimensional structure schematic view of secondary battery of a preferred embodiment of the utility model.

[0037] Figure 3 A partial cross-sectional structure schematic view of a first electrode plate of a secondary battery according to a preferred embodiment of the present application.

[0038] Figure 4 A partial cross-sectional structure schematic view of a first electrode plate of a secondary battery according to a preferred embodiment of the present application.

[0039] Figure 5 A partial cross-sectional structure schematic view of a first electrode plate of a secondary battery according to a preferred embodiment of the present application. Figure 4 A partial enlarged structure schematic view of part A.

[0040] Figure 6 A partial cross-sectional structure schematic view of a first electrode plate of a secondary battery according to a preferred embodiment of the present application.

[0041] Figure 7 A partial enlarged structure schematic view of part B. Figure 6

[0042] Figure 8 A cross-sectional structure schematic view of a secondary battery according to a preferred embodiment of the present application.

[0043] Figure 9 A partial enlarged structure schematic view of part C. Figure 8

[0044] A structure schematic view of a battery pack according to a preferred embodiment of the present application. Figure 10

[0045] A structure schematic view of an electronic device according to a preferred embodiment of the present application. Figure 11 BRIEF DESCRIPTION OF DRAWINGS

[0046] Electronic device 1000

[0047] Battery pack 100

[0048] Working part 300

[0049] Box body 310

[0050] Box cover 320

[0051] Secondary battery 1

[0052] Housing 10

[0053] Receiving cavity 13

[0054] Electrode assembly 20

[0055] First electrode plate 21

[0056]

[0057] ​​First current collector 211

[0058] Conductive layer 212

[0059] Insulating layer 213

[0060] First region 2131

[0061] Second region 2132

[0062] First active material layer 214

[0063] Flat region 2141

[0064] Thinned region 2142

[0065] Separator 22

[0066] Second electrode tab 23

[0067] Second current collector 231

[0068] Second active material layer 234

[0069] Cover plate assembly 40

[0070] Cover plate body 41

[0071] Liquid injection hole 411

[0072] Insulating member 42

[0073] Electrode terminal 43

[0074] Top cover 50

[0075] Housing 30

[0076] Side wall 31

[0077] Opening 32

[0078] End wall 33

[0079] Crimped portion 34

[0080] Cover plate 60

[0081] Insulating seal 70

[0082] First current collecting plate 81

[0083] Second current collecting plate 82

[0084] Pole 90

[0085] Pre-set direction Q

[0086] Thickness direction T DETAILED DESCRIPTION

[0087] A preferred embodiment is described below in conjunction with the accompanying drawings so as to make the present application more clearly and completely understood.

[0088] As shown in Figure 1 and Figure 2 , the present embodiment provides a secondary battery 1. The secondary battery 1 includes a housing 10 and an electrode assembly 20 accommodated in the housing 10.

[0089] As shown in Figures 3 to 5 , the electrode assembly 20 is formed by stacking a first electrode sheet 21, a separator 22 and a second electrode sheet 23 (the stacking includes forming a wound electrode assembly by winding after the stacking or forming a laminated electrode assembly by laminating after the stacking); the first electrode sheet 21 includes a first current collector 211, and a conductive layer 212 and an insulating layer 213 are covered on a partial region of at least one side of the first current collector 211 in a predetermined direction Q. The predetermined direction Q is a length direction or a width direction of the first current collector 211.

[0090] A first active material layer 214 is covered on the conductive layer 212, and the first active material layer 214 at least partially covers the insulating layer 213; in a thickness direction T of the first current collector 211, an orthographic projection of the insulating layer 213 is at least partially located outside a peripheral edge of the first active material layer 214; a thickness of the conductive layer 212 is m, and a thickness of the insulating layer 213 is n, and then n≤m.

[0091] Thus, by setting the partial area of one side of the first current collector 211 to be covered with the conductive layer 212 and the insulating layer 213 in the preset direction Q, the conductive layer 212 is covered with the first active material layer 214, and the first active material layer 214 at least partially covers the insulating layer 213, that is, the conductive layer 212 and the insulating layer 213 are coated on the first current collector 211 before the first active material layer 214, by pre-coating the conductive and insulating layers 213, the edges of the first active material layer 214 and the insulating layer 213 can be clear. Because the first active material layer 214 and the insulating layer 213 are generally coated by extrusion (paste is extruded through a pad), so the thickness of the insulating layer 213 is uncontrollable, generally 15-30 μm, thus causing the edges of the first active material layer 214 and the insulating layer 213 to be unclear; while in this embodiment, by pre-coating the conductive and insulating layers 213, avoiding the edges of the first active material layer 214 and the insulating layer 213 to be unclear due to simultaneous extrusion coating, effectively avoiding the fusion area of the two, that is, ensuring the edges of the first active material layer 214 to be straight, so that after stacking or winding, the CCD can accurately identify the edges of the first active material layer 214, facilitating accurate identification of the distance between the edges of the first active material layer 214 and the second active material layer 234 of the separator 22 and the second pole piece 23, controlling the distance between the pole pieces and the separator (the distance between the edge of the first active material layer 214 of the first pole piece 21 and the edge of the separator 22, and the distance between the edge of the first active material layer 214 and the edge of the second active material layer 234 of the second pole piece 23), ensuring the consistency of the electrode assembly 20, and greatly improving the yield. Moreover, before the first pole piece 21 is wound or stacked to prepare the electrode assembly 20, in order to improve the production rhythm and site utilization, the first current collector 211 is often pre-stored as a large roll (referred to as a pole roll) before coating the first active material layer 214, at this time, if m is less than n, that is, the thickness of the conductive layer 212 is less than the thickness of the insulating layer 213, so the hardness of the area where the insulating layer 213 is arranged in the pole roll is greater than the area where the conductive layer 212 is arranged, which will cause the edge where the insulating layer 213 is arranged to be raised, so that the edge of the pole roll in the radial direction from the center to the outer periphery is more and more inclined, causing the difference in the diameter of the pole roll at the positions corresponding to the conductive layer 212 and the insulating layer 213 of the pole roll to be more and more different, which is easy to cause the first current collector 211 to be torn, bringing safety hazards.In the embodiment, by setting the thickness m of the conductive layer 212 to be greater than or equal to the thickness n of the insulating layer 213, the edge of the pole piece in the radial direction can be kept at a relatively flat position from the center to the outer periphery, effectively avoiding the edge of the insulating layer 213 from being raised, so that the difference in diameter of the pole piece at the corresponding positions of the conductive layer 212 and the insulating layer 213 of the pole piece is relatively small, and the first current collector 211 is not easily torn, reducing the safety hazard. Therefore, when the first current collector 211 is used for coating to form the first pole piece 21, and the first pole piece 21 and the separator 22 are wound or laminated, the yield of the wound and laminated electrode assembly 20 can be greatly improved. At the same time, by controlling the thickness of the insulating layer 213, the material is reduced, and the production cost is also effectively reduced.

[0092] It should be noted that the conductive layer 212 and the insulating layer 213 are pre-coated on the first current collector 211, and the pre-coating includes but is not limited to the method of gravure coating the conductive layer 212 and the insulating layer 213.

[0093] Specifically, in the embodiment, along the preset direction Q, the partial regions on the two surfaces of the first current collector 211 opposite to each other in the thickness direction T are sequentially covered with the conductive layer 212 and the insulating layer 213, and the conductive layer 212 and the insulating layer 213 on the two surfaces are both covered with the first active material layer 214. The layer structures on the two surfaces of the first current collector 211 opposite to each other in the thickness direction T are symmetrically arranged with respect to the first current collector 211. However, this is not limiting, and in other embodiments, along the preset direction Q, the partial region on one surface of the first current collector 211 is covered with the conductive layer 212 and the insulating layer 213, and the conductive layer 212 and the insulating layer 213 on the surface are covered with the first active material layer 214.

[0094] The second pole piece 23 includes a second current collector 231, and the partial regions on the two surfaces of the second current collector 231 opposite to each other in the thickness direction T are both covered with the second active material layer 234. The two second active material layers 234 are symmetrically arranged with respect to the second current collector 231. However, this is not limiting, and in other embodiments, the partial region on one surface of the second current collector 231 can be covered with the second active material layer 234.

[0095] In the embodiment, 0.5 μm≤m<1 μm, for example, can be 0.5 μm, 0.6 μm, 0.75 μm, 0.8 μm or 0.99 μm, etc. Or, 0.5 μm<n<1 μm, for example, can be 0.55 μm, 0.6 μm, 0.75 μm, 0.8 μm or 0.99 μm. In this way, by controlling the thickness m of the conductive layer 212, on the one hand, the thickness m of the conductive layer 212 is avoided to be too small, and the conductive performance of the first current collector 211 cannot be improved. On the other hand, the thickness m of the conductive layer 212 is avoided to be too large, which leads to the overall volume of the electrode assembly 20 being too large, thereby affecting the overall energy density. By controlling the thickness n of the insulating layer 213, on the one hand, the thickness n of the insulating layer 213 is avoided to be too small, thereby not playing the role of insulation. On the other hand, the thickness n of the insulating layer 213 is avoided to be too large, thereby affecting the flexibility of the insulating layer 213. It should be noted that the pre-coating method of gravure coating can realize the thickness of the conductive layer and the insulating layer being less than or equal to 1 μm, and the thickness of the coating formed by the extrusion coating method is thicker, and the minimum thickness is about 10 μm.

[0096] The insulating layer 213 includes inorganic insulating fillers and a binder. The mass percentage of the inorganic insulating fillers is 70%-90% based on the mass of the insulating layer 213, and the mass percentage of the binder is 10%-30%.

[0097] Preferably, the cumulative particle size distribution volume percentage of the inorganic insulating fillers reaches 50% when the corresponding particle size is D50, and the relationship between D50 of the inorganic insulating fillers and n satisfies: 2≤n / D50≤5, for example, can be 2, 2.9, 3, 3.5, 4.9 or 5, etc. As described above, the pre-coating method of gravure coating is not limited to be used to realize the control of 0.5 μm≤m<1 μm, or 0.5 μm<n<1 μm, and on this basis, the relationship between D50 of the inorganic insulating fillers and n satisfies: 2≤n / D50≤5, which can effectively realize the coating of the thickness range of the insulating layer 213 as described above, thereby effectively controlling the thickness of the insulating layer 213, so that the edge of the pole piece in the radial direction from the center to the outer periphery is kept at a relatively flat position, effectively avoiding the edge of the insulating layer 213 being raised, thereby the diameter difference of the pole piece at the positions corresponding to the conductive layer 212 and the insulating layer 213 of the pole piece is relatively close, and the first current collector 211 is not easily torn, thereby reducing the safety hazard. When the first current collector 211 is used to coat the first pole piece 21, the yield of the wound and laminated electrode assembly 20 can be greatly improved when the first pole piece 21 and the separator 22 are wound or laminated.

[0098] Preferably, the cumulative particle size distribution volume percentage of the inorganic insulating filler reaches 90% at a particle size D90, and the D90 of the inorganic insulating filler is less than 0.8 μm. As described above, the pre-coating method other than gravure coating needs to be used to control 0.5 μm≤m<1 μm, or 0.5 μm<n<1 μm, and on this basis, the D90 of the inorganic insulating filler is limited to be less than 0.8 μm, which can effectively achieve the coating to meet the thickness range of the insulating layer 213, thereby effectively controlling the thickness of the insulating layer 213, and enabling the edge of the pole piece in the radial direction to remain at a relatively flat position from the center to the outer periphery, effectively avoiding the edge of the insulating layer 213 from being raised, so that the diameter difference of the pole piece at the position corresponding to the conductive layer 212 and the insulating layer 213 of the pole piece is relatively close, and the first current collector 211 is not easily torn, thereby reducing the safety hazard, and when the first current collector 211 is used for coating to form the first pole piece 21, the first pole piece 21 and the separator 22 are wound or laminated, which can greatly improve the yield of the wound and laminated electrode assembly 20.

[0099] Along the preset direction Q, the insulating layer 213 includes a first region 2131 not covered by the first active material layer 214 and a second region 2132 covered by the first active material layer 214, the width of the first region 2131 is w1, and the width of the second region 2132 is w2; wherein 3 mm≤w1+w2≤20 mm, for example, it can be 3 mm, 5 mm, 7 mm, 10 mm, 14 mm or 20 mm, etc.; or, 0.1≤w1 / (w1+w2)≤1, for example, it can be 0.1, 0.4, 0.5, 0.75, 0.9 or 1, etc. In this way, by setting the value range of the width of the insulating layer 213, the flexibility of the insulating layer 213 can be effectively ensured. By setting the proportion range of the width of the first region 2131 to the width of the insulating layer 213, it can be ensured that the first region 2131 always exceeds the edge of the first active material layer 214 by a certain width along the preset direction Q, thereby ensuring the flexibility of the insulating layer 213 while ensuring the insulation function of the insulating layer 213, and in the case of wide coating of the insulating layer 213, the tab of the first pole piece 21 can still be normally bent; and the tab of the first pole piece 21 will not directly contact the second pole piece 23 in an extreme environment, for example, when the tab is inserted upside down.

[0100] In the preset direction Q, the first active material layer 214 comprises the connected flat area 2141 and the thinned area 2142, the width of the thinned area 2142 is w3, and w3 is in mm; wherein 0

[0101] In the preset direction Q, the minimum distance between the insulating layer 213 and the conductive layer 212 is w4, wherein 0≤w4≤1mm, for example, it can be 0, 0.4mm, 0.5mm, 0.75mm, 0.9mm or 1mm, etc. By controlling the minimum distance w4, the space occupied by the insulating layer 213 is avoided to affect the area where the tab is located, so as to avoid affecting the energy density of the battery, and the bottom of the first active material layer 214 can be reasonably contacted with the conductive layer 212 to improve the conductivity. At the same time, because the reserved w4 is in a suitable range, the quality of the pre-coating of the insulating layer 213 and the conductive layer 212 can be controlled.

[0102] Please refer to Figure 4 and Figure 5 In an embodiment of the present embodiment, the minimum distance w4 between the insulating layer 213 and the conductive layer 212 is 0. Since w4 is 0, w4 is not indicated in Figure 4 and Figure 5 . That is, the insulating layer 213 is arranged close to the conductive layer 212, so that the insulating layer 213 occupies the least space and avoids affecting the area where the tab is located to the maximum extent.

[0103] Preferably, as shown in Figure 6 and Figure 7 In an embodiment of the present embodiment, the minimum distance w4 between the insulating layer 213 and the conductive layer 212 is 1mm. That is, the insulating layer 213 and the conductive layer 212 are arranged at intervals, and part of the first current collector 211 is exposed. Since the color of the first current collector 211 and the color of the conductive layer 212 are quite different, by arranging the insulating layer 213 and the conductive layer 212 at intervals, the edge of the conductive layer 212 can be easily grabbed, and the interval arrangement of the insulating layer 213 and the conductive layer 212 makes the edges of the two more flat.

[0104] In the embodiment, the first tab 21 is a positive tab, and the second tab 23 is a negative tab. Since the material of the metal part of the positive tab is usually aluminum, and the material of the metal part of the negative tab is usually copper, the hardness of the metal part of the positive tab is higher than that of the metal part of the negative tab. The insulation layer 213 arranged on the positive tab can reduce the risk of deformation of the positive tab, and improve the insulation performance of the positive tab, thereby greatly improving the safety and reliability of the battery performance. However, it is not limited thereto, and in other embodiments, the second tab 23 can be a positive tab, and the first tab 21 can be a negative tab.

[0105] The first active material layer 214 is a positive active material layer, and the first active material layer 214 includes lithium iron phosphate. When the positive active material is lithium iron phosphate, the first active material layer 214 and the insulation layer 213 are coated at the same time, which is more likely to be fused, causing the edge to be unclear. By pre-coating the insulation layer 213, the problem of unclear edge of the first active material layer 214 and the insulation layer 213 of the electrode active material being lithium iron phosphate can be better improved.

[0106] The electrode assembly 20 is a wound electrode assembly, or the electrode assembly 20 is a stacked electrode assembly.

[0107] Please refer to Figure 1 and Figure 2 In an embodiment of the embodiment, the secondary battery 1 is a square battery. However, it is not limited thereto, and in other embodiments, the secondary battery 1 can also be a cylindrical battery or other shaped battery.

[0108] The specific structure of the insulation layer 213 in the embodiment is applied to a square battery. By pre-coating the insulation layer 213, the edge of the first active material layer 214 and the insulation layer 213 can be clear, the fusion area between the two can be effectively avoided, the edge of the first active material layer 214 can be accurately identified, the consistency of the electrode assembly 20 can be ensured, and the yield can be greatly improved. Further, by setting the thickness m of the conductive layer 212 to be greater than or equal to the thickness n of the insulation layer 213, the edge of the insulation layer 213 can be effectively prevented from being raised, thereby greatly improving the yield. At the same time, by controlling the thickness of the insulation layer 213, the material is reduced, and the production cost is also effectively reduced. Further, since the tabs of the first tab 21 and the tabs of the second tab 23 of the square battery are led out on the same side, by controlling the coating thickness of the insulation layer 213, the insulation of the tabs of the first tab 21 and the tabs of the second tab 23 can be better achieved.

[0109] 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. The insulating member 42 is located between the cover body 41 and the electrode assembly 20.

[0110] 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 first electrode plate 21 are called first tabs, and the tabs leading out from the second electrode plate 23 are called second tabs. The first tabs and the second tabs are respectively electrically connected to the corresponding electrode terminals 43.

[0111] The secondary battery 1 also includes a top cover 50 disposed on the cover assembly 40.

[0112] By setting the thickness of the conductive layer to m and the thickness of the insulating layer to n in the square battery, where n≤m and the units of m and n are both μm, the strength of the electrode tabs can be enhanced and the phenomenon of electrode tab insertion can be reduced by setting 3mm≤w1+w2≤20mm when the electrode tabs of the square battery are directly connected to the adapter or terminal.

[0113] like Figure 8 and Figure 9 As shown, in another embodiment of this invention, 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, this is not a limitation; in other embodiments, the secondary battery 1 can also be a prismatic battery or other shaped batteries. The casing 30 of the cylindrical battery is cylindrical.

[0114] The specific structure of the insulation layer 213 in this embodiment is applied to a cylindrical battery. By pre-applying the conductive insulation layer 213, the edges of the first active material layer 214 and the insulation layer 213 can be clearly defined, effectively avoiding the fusion of the two, facilitating accurate identification of the edge of the first active material layer 214, ensuring the consistency of the electrode assembly 20, and greatly improving the yield rate. Furthermore, by setting the thickness m of the conductive layer 212 to be greater than or equal to the thickness n of the insulation layer 213, the edge of the insulation layer 213 can be effectively prevented from being raised, thereby greatly improving the yield rate. At the same time, by controlling the thickness of the insulation layer 213, the material usage is reduced, and the production cost is also effectively reduced. Furthermore, by controlling the application thickness of the insulation layer 213, the flexibility of the insulation layer 213 can be effectively improved. In the case of wide application of the insulation layer 213, the tab of the first electrode sheet 21 can still be normally bent. Furthermore, in extreme environments, such as when the tab is inserted upside down, the tab of the first electrode sheet 21 will not directly contact the second electrode sheet 23.

[0115] The electrode assembly 20 is accommodated in the shell 30, which includes a surrounding side wall 31 and an opening 32 formed at one end of the side wall 31. The shell 30 also includes a crimping portion 34 formed at one end of the side wall 31 close to the opening 32 and recessed towards the inside of the shell 30. The secondary battery 1 also includes a cover plate 60, an insulating seal 70, and a current collector. The cover plate 60 is mounted to the opening 32. The insulating seal 70 surrounds the periphery of the cover plate 60 to insulate and seal the cover plate 60 and the shell 30. The current collector is arranged between the electrode assembly 20 and the cover plate 60 and is electrically connected to the shell 30. The connecting tab of the current collector is located on the side of the crimping portion 34 facing the electrode assembly 20 and is welded to the crimping portion 34. In this way, by arranging the connecting tab of the current collector on the side of the crimping portion 34 facing the electrode assembly 20 and welding it to the crimping portion 34, i.e. the welding area of the current collector to the tab is located closer to the electrode assembly 20 than the crimping portion 34, thereby preventing the crimping portion 34 from affecting the welding area of the tab to the current collector, and thus improving the welding strength of the tab to the current collector.

[0116] Further, the shell 30 also includes an end wall 33, and the side wall 31 surrounds the end wall 33 and is located at the end of the side wall 31 away from the opening 32. The end wall 33 and the side wall 31 surround the accommodation cavity in the shell 30 for accommodating the electrode assembly 20, the electrolyte, and other necessary components of the battery. The connection between the end wall 33 and the side wall 31 can be achieved in various ways, such as one-piece stamping, one-piece casting, or separate welding.

[0117] The secondary battery 1 also includes a pole 90 that passes through the end wall 33 and is insulated from the end wall 33.

[0118] The current collector plate includes a first current collector plate 81 and a second current collector plate 82, wherein the first current collector plate 81 is arranged between the electrode assembly 20 and the end wall 33; and the second current collector plate 82 is arranged between the electrode assembly 20 and the cover plate 60. In the embodiment, the first current collector plate 81 corresponds to the positive tab of the positive plate, and the positive tab is electrically connected to the pole 90 through the first current collector plate 81; and the second current collector plate 82 corresponds to the negative tab of the negative plate, and the negative tab is electrically connected to the shell 30 through the second current collector plate 82. However, the first current collector plate 81 can correspond to the negative tab, and the second current collector plate 82 can correspond to the positive tab in other embodiments.

[0119] The preparation method of the secondary battery in the embodiment is as follows:

[0120] 1. Preparation of the positive plate: lithium iron phosphate is used as the positive active material, the positive active material, polyvinylidene fluoride as the binder, and small-particle conductive carbon black (hereinafter referred to as Super P) as the conductive agent are mixed in a weight ratio of 98:1:1, N-methyl pyrrolidone (NMP) is added, and the system is stirred to be uniform and transparent under the action of a vacuum stirrer to obtain a positive slurry; the positive slurry is uniformly coated on the positive current collector of aluminum foil material; the aluminum foil is dried at room temperature, then transferred to an oven for drying, and then cold-pressed and cut to obtain the positive plate.

[0121] 2. Preparation of the negative plate: artificial graphite is used as the negative active material, Super P is used as the conductive agent, carboxymethyl cellulose sodium (CMC-Na) is used as the thickening agent, and styrene butadiene rubber (SBR) is used as the binder, which are mixed in a mass ratio of 96:1:1:2, deionized water is added, and a negative slurry is obtained under the action of a vacuum stirrer; the negative slurry is uniformly coated on the negative current collector of copper foil material; the copper foil is dried at room temperature, then transferred to an oven for drying, and then cold-pressed and cut to obtain the negative plate.

[0122] 3. Preparation of the electrolyte: in an argon atmosphere glove box with a water content of <10 ppm, battery-grade (i.e., a purity grade meeting the performance requirements of the battery) ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and ethyl acetate (EA) are mixed in a mass ratio of 1:1:2:6 to form an organic solvent. Other components are added according to the electrolyte composition described in the table below, and the mixture is uniformly mixed to obtain the electrolyte.

[0123] 4. Preparation of the separator: a polypropylene film (PP) with a thickness of 12 μm is used as the isolation film, and the above-prepared positive plate, isolation film, and negative plate are sequentially laminated, so that the separator is located between the positive plate and the negative plate to play a role of isolation. Then, the separator is wrapped with an aluminum plastic film, transferred to a vacuum oven for drying at 120°C, and then injected with the above-prepared electrolyte 3.0 g / Ah, sealed, and subjected to electrolyte formation to finally prepare a soft-pack battery (i.e., a lithium ion battery) with a capacity of 1 Ah.

[0124] As Figure 10 shown, the utility model still provides a kind of battery pack 100, battery pack 100 includes above-mentioned secondary battery 1, in the embodiment of the utility model battery pack 100, battery pack 100 includes box 310, box cover 320 and multiple secondary batteries 1, multiple secondary batteries 1 are placed in box 310, and are connected in series or parallel with each other, or series and parallel hybrid, box cover 320 is capped on box 310, to protect multiple secondary batteries 1.It needs to be explained, battery pack 100 except the utility model secondary battery 1 also can include battery pack 100 thermal management system, circuit board etc.Parts, battery pack 100 can be battery module also can be battery pack, energy storage electric cabinet etc.;Here will not be explained one by one.

[0125] As Figure 11 shown, the utility model still provides a kind of electronic device 1000, electronic device 1000 includes above-mentioned battery pack 100.Working part 300 is electrically connected with battery pack 100, to obtain electric energy support.As an example, electronic device 1000 is vehicle, and vehicle can be fuel automobile, gas automobile or new energy automobile, and new energy automobile can be pure electric vehicle, hybrid vehicle or range extended vehicle etc., but not limited to this.Working part 300 is vehicle body, and battery pack 100 is arranged at the bottom of vehicle body, and provides electric energy support for the running of vehicle or the operation of electrical element in vehicle.However in some other embodiments, electronic device 1000 can also be mobile phone, portable device, notebook computer, ship, spacecraft, electric toy and electric tool etc.Spacecraft includes airplane, rocket, space shuttle and spaceship etc.Working part 300 can be the unit component that can obtain the electric energy of battery pack 100 and make corresponding work, for example, fan blade rotating unit of fan, dust collection working unit of dust collector etc.Electric toy includes fixed or mobile electric toy, for example, game machine, electric car toy, electric ship toy and electric plane toy etc.Electric tool includes metal cutting electric tool, grinding electric tool, assembly electric tool and railway electric tool, for example, electric drill, electric grinder, electric wrench, electric screwdriver, electric hammer, impact drill, concrete vibrator and electric planer etc.The embodiment of the application does not make special limitation to above-mentioned electronic device 1000.

[0126] Although the specific embodiments of the utility model are described above, those skilled in the art should understand that this is only illustrative, and the protection scope of the 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 the utility model, and these changes and modifications all fall within the protection scope of the utility model.

Claims

1. A secondary battery characterized by comprising: The secondary battery comprises: a shell; an electrode assembly accommodated in the shell, the electrode assembly being formed by stacking a first electrode sheet, a separator, and a second electrode sheet; the first electrode sheet comprises a first current collector, a conductive layer, and an insulating layer are covered on a partial area of at least one side of the first current collector along a preset direction, the preset direction being a length direction or a width direction of the first current collector; further, a first active material layer is covered on the conductive layer, and the first active material layer at least partially covers the insulating layer, a normal projection of the insulating layer in a thickness direction of the first current collector is at least partially located outside a peripheral edge of the first active material layer; assuming that a thickness of the conductive layer is m and a thickness of the insulating layer is n, then n≤m.

2. The secondary battery according to claim 1, wherein 0.5 μm≤m<1 μm.

3. The secondary battery according to claim 1, wherein along the preset direction, the insulating layer comprises a first area not covered by the first active material layer and a second area covered by the first active material layer, a width of the first area is w1, and a width of the second area is w2; wherein, 3 mm≤w1+w2≤20 mm, or 0.1≤w1 / (w1+w2)≤1.

4. The secondary battery according to claim 3, wherein along the preset direction, the first active material layer comprises a flat area and a thinned area connected to each other, and a width of the thinned area is w3; wherein, 0<w2 / w3≤1.

05.

5. The secondary battery according to claim 1, wherein along the preset direction, a minimum distance between the insulating layer and the conductive layer is w4, wherein, 0≤w4≤1 mm.

6. The secondary battery according to any one of claims 1 to 5, wherein the first electrode sheet is a positive electrode sheet, and the first active material layer comprises lithium iron phosphate; and / or, 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 an accommodation cavity, and the electrode assembly is accommodated in the accommodation cavity; and / or, the secondary battery is a square battery; and / or, the electrode assembly is a wound electrode assembly.

7. The secondary battery of any one of claims 1 to 5, wherein: the shell comprises a surrounding side wall and an opening formed at one end of the side wall; the shell further comprises a crimping portion formed at one end of the side wall close to the opening and recessed towards the inside of the shell; the secondary battery further comprises: a cover plate installed at the opening; an insulating sealing member surrounding a periphery of the cover plate to insulate and seal the cover plate and the shell; a current collecting disc arranged between the electrode assembly and the cover plate and electrically connected to the shell, a connecting sheet of the current collecting disc being located on a side of the crimping portion facing the electrode assembly and being welded to the crimping portion; and / or, the secondary battery is a cylindrical battery. The secondary battery of any one of claims 1 to 7.

8. A battery pack characterized by comprising: The battery pack of claim 8.

9. An electronic device, comprising: The battery pack of claim 8.

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