Composite current collector, pole piece, battery and electric device

Abstract

The invention provides a composite current collector, a pole piece, a battery and a power utilization device, the composite current collector comprises a current collector and two switching tabs, the two switching tabs are respectively connected with the current collector, the composite current collector is provided with an active material area, a transition area, a connection area and an external connection tab area, the transition area is connected between the active material area and the connection area, and the external connection tab area is connected with the connection area. The connecting area is a joint of the current collector and the transfer tab; the connecting area comprises a first connecting section and a second connecting section, the first connecting section is connected with the transition area, the second connecting section is connected with the external tab area, the length of the first connecting section is greater than that of the external tab area, and the length of the second connecting section is greater than or equal to that of the external tab area; or the length of the first connecting section, the length of the second connecting section and the length of the external tab area are equal to the width of the active material area. The length of the first connecting section in the composite current collector is greater than that of the external tab region, so that the problem that the overcurrent capacity and the heat conduction capacity of the connecting region are insufficient when the composite current collector discharges at a high rate is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a composite current collector, a pole piece, a battery and an electrical device. Background Art

[0002] As an important auxiliary material of the battery, the current collector plays an important role in supporting active materials and conducting current. Since the current collector does not contribute to the capacity of the battery, it is also called inactive weight. In order to improve the energy density of the battery, a composite current collector is designed. The composite current collector is a new type of polymer-metal composite foil with a "sandwich" structure. Compared with traditional current collectors, the composite current collector has the advantages of improving battery acupuncture safety and reducing the quality of the current collector. However, since the polymer base film of the composite current collector is not conductive, the conductive layers on both sides need to be connected to copper foil or aluminum foil as transfer tabs, which increases the complexity of the process. In addition, the current flow performance and conductivity of the composite current collector are worse than those of traditional metal foil current collectors, and the tabs are severely heated during high-rate discharge. Summary of the invention

[0003] In order to solve the problems of thin conductive layer thickness, insufficient current carrying capacity and insufficient thermal conductivity of the existing composite current collector, the present invention provides a composite current collector, a pole piece, a battery and an electrical device.

[0004] In a first aspect, the present invention provides a composite current collector, comprising a current collector and two transfer tabs, wherein the two transfer tabs are respectively connected to the current collector, the composite current collector having a transition region, a connection region, an external tab region, and an active material region for coating active materials, wherein the transition region is connected between the active material region and the connection region, the connection region is a connection between the current collector and the transfer tab, and the external tab region is connected to a side of the connection region away from the transition region;

[0005] The connection area includes a first connection segment and a second connection segment, the first connection segment is connected to the transition area, the second connection segment is connected to the external pole lug area, the length of the first connection segment is greater than the length of the external pole lug area, and the length of the second connection segment is greater than or equal to the length of the external pole lug area; or, the length of the first connection segment, the length of the second connection segment and the length of the external pole lug area are all equal to the width of the active material area.

[0006] Optionally, the length of the first connecting section is greater than or equal to the second connecting section;

[0007] The length of the first connecting section is less than or equal to the length of the transition zone;

[0008] The length of the transition zone is less than or equal to the width of the active material zone.

[0009] Optionally, the width of the connection zone is 0 to 10 mm; and / or the width of the transition zone is 0 to 2 mm; and / or the length of the active material zone is 6 to 800 mm and the width is 4 to 600 mm.

[0010] Optionally, the active material region is located on the current collector, and the external tab region is located on at least one of the transfer tabs; the current collector has a first transition region and a first connection region, and the first transition region is connected between the active material region and the first connection region;

[0011] Each of the transfer tabs has a second transition region and a second connection region, the second transition region is connected to the second connection region, and the external tab region is connected to a side of the second connection region away from the second transition region;

[0012] The second transition zone is located at one side of the first transition zone to form the transition zone; the second connection zone is located at one side of the first connection zone, and the second connection zone is connected to the first connection zone and then cut to form the connection zone.

[0013] Optionally, the height of the first transition zone is greater than or equal to the width of the second transition zone; and the width of the first connection zone is greater than or equal to the width of the second connection zone.

[0014] Optionally, the switching tab is a copper-containing metal strip or an aluminum-containing metal strip, the copper-containing metal strip is a copper strip or a copper alloy strip, and the mass content of copper in the copper-containing metal strip is greater than or equal to 80%;

[0015] The aluminum-containing metal strip is an aluminum strip or an aluminum alloy strip, and the mass content of aluminum in the aluminum-containing metal strip is greater than or equal to 80%.

[0016] Optionally, the adapter tab has a thickness of 3 to 12 μm and a width of 4 to 40 mm.

[0017] Optionally, the current collector and the transfer tab are welded by a welding head, or crimped by a pressing head;

[0018] The width of the welding head or the pressing head is a mm, 2≤a≤10;

[0019] The widths of the two transfer tabs are the same or different, and the width of the wider transfer tab is ≥ (a+0.5) mm.

[0020] In a second aspect, the present invention further provides a pole piece, comprising an active material layer and a composite current collector as described above, wherein the current collector comprises a base film and a conductive layer located on both sides of the base film, and the active material layer is arranged on a side of at least one of the conductive layers away from the base film.

[0021] Optionally, when the active material layer completely covers the conductive layer, at least part of the surface of the active material region, the first transition region and the first connection region is provided with the active material layer;

[0022] When the active material layer is disposed on a portion of the surface of the conductive layer, the active material layer is disposed on at least a portion of the surface of the active material region.

[0023] Optionally, the base film has a thickness of 0.5 to 30 μm; and / or the conductive layer has a thickness of 0.1 to 15 μm.

[0024] Optionally, when the current collector is a positive electrode current collector, the conductive layer includes at least one of carbon materials, conductive polymers, copper, aluminum, gold, silver, iron, nickel, zinc and alloys thereof; the active material layer includes one or more of lithium nickel cobalt manganese oxide, lithium iron manganese phosphate, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium manganese rich base, lithium nickel manganese oxide and lithium vanadium phosphate.

[0025] Optionally, when the current collector is a negative electrode current collector, the conductive layer includes at least one of carbon materials, conductive polymers, lithium-containing metal strips, copper, aluminum, gold, silver, iron, nickel, zinc and alloys thereof; the negative electrode active material layer includes one or more of metallic lithium, lithium alloys, graphite, silicon, silicon carbon and silicon oxygen.

[0026] In a third aspect, the present invention further provides a battery, comprising a pole piece as described in any one of the above items.

[0027] Optionally, the battery is a liquid battery, a semi-solid battery or a solid battery.

[0028] In a fourth aspect, the present invention further provides an electrical device, comprising a battery as described in any one of the above items.

[0029] In the present invention, the length of the first connection section is greater than the length of the external pole ear area, and the length of the second connection section is greater than or equal to the length of the external pole ear area, which effectively improves the flow capacity of the connection area where the transfer pole ear and the current collector are connected, and improves the problem of heating in the pole ear area under rate discharge caused by the thin conductive layer of the composite current collector, thereby avoiding thermal runaway of the battery. The rate discharge capacity of the composite current collector pole piece is improved, which is conducive to expanding the application of the composite current collector pole piece to high-rate discharge scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic structural diagram of a composite current collector provided by one embodiment of the present invention;

[0031] Figure 2 is a schematic structural diagram of a composite current collector provided by another embodiment of the present invention;

[0032] Figure 3 is a schematic structural diagram of a composite current collector provided by another embodiment of the present invention;

[0033] Figure 4 is a schematic structural diagram of a composite current collector provided by another embodiment of the present invention;

[0034] Figure 5 It is a schematic structural diagram of a current collector and a transfer tab of a composite current collector provided in one embodiment of the present invention.

[0035] The reference numerals in the drawings of the specification are as follows:

[0036] 1. Current collector; 2. Transfer tab; 3. Active material area; 4. Transition area; 41. First transition area; 42. Second transition area; 5. Connection area; 51. First connection section; 52. Second connection section; 53. First connection area; 54. Second connection area; 6. External tab area. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] In the description of the present invention, it should be understood that the terms "longitudinal", "radial", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In order to illustrate the technical solution of the present invention, specific embodiments are provided below for illustration.

[0040] like Figure 1 to Figure 5As shown, a composite current collector according to an embodiment of the present invention comprises a current collector 1 and two transfer tabs 2, wherein the two transfer tabs 2 are respectively connected to the current collector 1, and the composite current collector 1 comprises a transition zone 4, a connection zone 5, an external tab zone 6 and an active material zone 3 for coating active materials, wherein the transition zone 4 is connected between the active material zone 3 and the connection zone 5, the connection zone 5 is the connection between the current collector 1 and the transfer tab 2, and the external tab zone 6 is connected to a side of the connection zone 5 away from the transition zone 4.

[0041] The connection area 5 includes a first connection segment 51 and a second connection segment 52, wherein the first connection segment 51 is connected to the transition area 4, and the second connection segment 52 is connected to the external tab area 6, wherein the length of the first connection segment 51 is greater than the length of the external tab area 6, and the length of the second connection segment 52 is greater than or equal to the length of the external tab area 6. Alternatively, the length of the first connection segment 51, the length of the second connection segment 52, and the length of the external tab area 6 are all equal to the width of the active material area 3, in which case the transfer tab 2 connected to the current collector 1 is a full tab, and the current flow capacity reaches the strongest.

[0042] In this embodiment, the length of the first connection section 51 is greater than the length of the external pole ear area 6, and the length of the second connection section 52 is greater than or equal to the length of the external pole ear area 6, which effectively improves the flow capacity of the connection area 5 where the transfer pole ear 2 and the current collector 1 are connected, and improves the problem of heating in the pole ear area under rate discharge caused by the thin conductive layer of the composite current collector 1, thereby avoiding thermal runaway of the battery. The rate discharge capability of the pole piece of the composite current collector 1 is improved, which is conducive to expanding the application of the pole piece of the composite current collector 1 to high-rate discharge scenarios.

[0043] Specifically, the width of the current collector 1 is 50 to 810 mm.

[0044] like Figure 1 to Figure 4 As shown, in some embodiments of the present invention, the length of the first connecting section 51 is greater than or equal to the second connecting section 52.

[0045] The length of the first connecting section 51 is less than or equal to the length of the transition zone 4 .

[0046] The length of the transition zone 4 is less than or equal to the width of the active material zone 3 .

[0047] That is to say, the connection area 5 is rectangular or stepped. When the connection area 5 is rectangular, its length is L3 and its width is M3. The length of the transition area 4 is L2 and its width is M2, and L3≤L2.

[0048] When the connection area 5 is stepped, the length of the first connection section 51 is L31, the width is M31, L31≤L2; the length of the second connection section 52 is L32, the width is M32, L32≤L31, M31+M32=M3. The length of the external tab area 6 is L4, L4≤L3, the width of the external tab area 6 is M4, and the range of M4 is 0-30 mm.

[0049] In some embodiments of the present invention, the width of the connection zone 5 is 0-10 mm. And / or, the width of the transition zone 4 is 0-2 mm. And / or, the length of the active material zone 3 is 6-800 mm and the width is 4-600 mm. Specifically, Figure 1 As shown, the active material region has a length of L1 and a width of M1.

[0050] like Figure 5 As shown, in some embodiments of the present invention, the active material region 3 is located on the current collector 1, and the external tab region 6 is located on at least one of the transfer tabs 2. The current collector 1 has a first transition region 41 and a first connection region 53, and the first transition region 41 is connected between the active material region 3 and the first connection region 53.

[0051] Each of the transfer tabs 2 has a second transition region 42 and a second connection region 54 . The second transition region 42 is connected to the second connection region 54 . The external tab region 6 is connected to a side of the second connection region 54 away from the second transition region 42 .

[0052] The second transition zone 42 is located on one side of the first transition zone 41 to form the transition zone 4. The second connection zone 54 is located on one side of the first connection zone 53, and the second connection zone 54 is connected to the first connection zone 53 and then cut to form the connection zone 5. Specifically, the projection of the first transition zone 41 on the second transition zone 42 covers the second transition zone 42, and the projection of the first connection zone 53 on the second connection zone 54 covers the second connection zone 54. After the current collector 1 and the transfer tab 2 are connected by welding or crimping the first connection zone 53 and the second connection zone 54, the first connection zone 53 and the second connection zone 54 are cut to form a rectangular or stepped connection zone 5.

[0053] In some embodiments of the present invention, the height of the first transition region 41 is greater than or equal to the width of the second transition region 42. The width of the first connection region 53 is greater than or equal to the width of the second connection region 54.

[0054] In some embodiments of the present invention, the switching tab 2 is a copper-containing metal strip or an aluminum-containing metal strip, the copper-containing metal strip is a copper strip or a copper alloy strip, and the mass content of copper in the copper-containing metal strip is greater than or equal to 80%.

[0055] The aluminum-containing metal strip is an aluminum strip or an aluminum alloy strip, and the mass content of aluminum in the aluminum-containing metal strip is greater than or equal to 80%.

[0056] In some embodiments of the present invention, the thickness of the transfer tab 2 is 3-12 μm, and the width is 4-40 mm.

[0057] In some embodiments of the present invention, the current collector 1 and the transition tab 2 are welded by a welding head or crimped by a pressing head.

[0058] The width of the welding head or the pressing head is a mm, 2≤a≤10.

[0059] The widths of the two transfer tabs 2 are the same or different, and the width of the wider transfer tab 2 is ≥ (a+0.5) mm.

[0060] Specifically, the two transition tabs 2 are aligned close to one side of the current collector 1 . When the two transition tabs 2 have different widths, the widths of their second connection areas 54 may also be different, and the transition tab 2 with a narrower width does not have an external tab area 6 .

[0061] In a second aspect, an embodiment of the present invention further provides a pole piece, comprising an active material layer and a composite current collector 1 as described in any one of the above embodiments, wherein the current collector 1 comprises a base film and a conductive layer located on both sides of the base film, and the active material layer is arranged on a side of at least one of the conductive layers away from the base film. Specifically, the area in the pole piece corresponding to the transition area 4 is a blank area.

[0062] In some embodiments of the present invention, when the active material layer completely covers the conductive layer, at least part of the surface of the active material region 3 , the first transition region 41 and the first connection region 53 is provided with the active material layer.

[0063] When the active material layer is disposed on a portion of the surface of the conductive layer, the active material layer is disposed on at least a portion of the surface of the active material region 3 .

[0064] In some embodiments of the present invention, the thickness of the base film is 0.5-30 μm, and / or the thickness of the conductive layer is 0.1-15 μm.

[0065] In some embodiments of the present invention, when the current collector 1 is a positive electrode current collector, the conductive layer includes at least one of carbon materials, conductive polymers, copper, aluminum, gold, silver, iron, nickel, zinc and alloys thereof. The active material layer includes one or more of lithium nickel cobalt manganese oxide, lithium iron manganese phosphate, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium rich manganese base, lithium nickel manganese oxide, and lithium vanadium phosphate. This embodiment does not limit this. When the current collector 1 is a positive electrode current collector, the active material layer can be prepared by a dry method or a wet method.

[0066] Furthermore, when the electrode sheet is a positive electrode sheet, the active material region 3 of the current collector 1 includes a ceramic coating region, and the ceramic coating region is connected to the transition region 4 .

[0067] In some embodiments of the present invention, when the current collector 1 is a negative electrode current collector, the conductive layer includes at least one of carbon materials, conductive polymers, lithium-containing metal strips, copper, aluminum, gold, silver, iron, nickel, zinc and alloys thereof. The active material layer includes one or more of metallic lithium, lithium alloys, graphite, silicon, silicon carbon and silicon oxygen.

[0068] The lithium alloy is an alloy formed by metallic lithium and one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth. The mass content of metallic lithium in the lithium alloy is 0.5% to 99.5%.

[0069] It should be noted that when the current collector 1 is a negative electrode current collector, the thickness of the active material layer is 0 to 100 μm, and when the thickness of the active material layer is 0, the conductive layer is a lithium-containing metal strip, and the lithium-containing metal strip includes a pure lithium strip or a lithium alloy strip. The lithium-containing metal strip can be used as a conductive layer and a negative electrode active material layer at the same time, and the thickness of the lithium-containing metal strip is 1 to 50 μm.

[0070] The active material layer can be prepared by rolling, physical vapor deposition (PVD), coating, etc. The conductive layer can be prepared on the base film by physical vapor deposition (PVD), chemical vapor deposition (CVD) or water electroplating.

[0071] On the other hand, an embodiment of the present invention further provides a battery, comprising a pole piece as described in any one of the above embodiments.

[0072] In some embodiments of the present invention, the battery is a liquid battery, a semi-solid battery or a solid battery. The semi-solid battery includes a positive electrode sheet, a negative electrode sheet and a gel electrolyte, or the semi-solid battery includes a positive electrode sheet, a negative electrode sheet, a solid electrolyte and 0.5% to 50% electrolyte.

[0073] Furthermore, the battery may be a laminated soft-pack battery, a wound battery or a cylindrical battery.

[0074] When the battery is a liquid battery, the liquid battery further includes a separator and an electrolyte.

[0075] The diaphragm includes polypropylene PP, polyethylene PE and composite films thereof. Furthermore, at least one side of the diaphragm is provided with a ceramic coating.

[0076] The electrolyte includes a lithium salt, a solvent and an additive, wherein the solvent includes one or more of a carbonate compound, an ether compound and a nitrile compound. The lithium salt includes LiPF 6 、LiClO4 , LiBF 4 、LiAsF 6 、LiCF 3 SO, LiTFSI, LiFSI, LiTNFSI, LiFNFSI, LiBOB, LiN(CF 3 SO 2 ) 2 and LiC(SO 2 CF 3 ) 3 The additives include film-forming additives, conductive additives, flame retardant additives, overcharge protection additives, additives for controlling the water and HF content in the electrolyte, general additives for improving low-temperature performance, and additives for improving the interface stability of the metal lithium negative electrode, such as fluoroethylene carbonate FEC, lithium nitrate LiNO 3 .

[0077] Specifically, the carbonate compound includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and γ-butyrolactone.

[0078] The ether compound includes one or more of tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxydimethyl ether and 1,2-dimethoxyethane.

[0079] The nitrile compound includes acetonitrile.

[0080] When the battery is a solid-state battery, the solid-state battery further includes a solid electrolyte, and the solid electrolyte includes one of an inorganic solid electrolyte, a polymer solid electrolyte and a composite solid electrolyte. Specifically, the composite solid electrolyte is an electrolyte based on a polymer matrix and an inorganic filler.

[0081] The inorganic solid electrolyte includes one or more of an oxide solid electrolyte, a sulfide solid electrolyte and a halide solid electrolyte.

[0082] The polymer solid electrolyte includes a polymer matrix and a lithium salt.

[0083] The composite solid electrolyte comprises a polymer matrix and an inorganic filler. Specifically, the composite method of the polymer matrix and the inorganic filler includes but is not limited to dispersion and mixing, or the inorganic filler is filled in the gap of the polymer matrix.

[0084] Specifically, the oxide solid electrolyte includes one or more of a NASICON electrolyte, a perovskite electrolyte, and a Garnet garnet electrolyte. Specifically, the NASICON electrolyte includes LATP (Li 1.3 Al 0.3 Ti1.7 (PO 4 ) 3 )、LAGP(Li 1.5 Al 0.5 Ge 1.5 P 3 O 12 Garnet garnet electrolytes include lithium lanthanum zirconium oxide LLZO, with a conductivity of 10- 3 S / cm, and has good stability to lithium metal.

[0085] The sulfide solid electrolyte includes binary compounds and ternary compounds. The binary compound includes Li 2 S-SiS 2 , Li 2 SP 2 S 5 , Li 2 S-GeS 2 , ternary compounds include Li 2 S-MS 2 -P 2 S 5 and Li 6 PS 5 One or more of X, wherein X is selected from at least one of F, Cl, Br and I, and M is selected from at least one of Si, Ge, Sn and Al.

[0086] The halide solid electrolyte includes Li a MX 4 Class, Li a MX 6 Class and Li a MX 8 Class, M is a divalent metal ion, a trivalent metal ion or other valence metal ion, and X is a halogen. Specifically, the halide solid electrolyte includes Li 2 MnCl 4 , Li 2 ZnCl 4 ,LiYb 4 、LiAlF 4 , Li 3 YC 6 , Li 3 BrCl 6 and Li 6 CoCl 8 One or more of .

[0087] The polymer matrix includes one or more of polyethylene oxide, polycarbonate, polytrimethylene carbonate, polymethyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoroethylene copolymer and lithium polyacrylate.

[0088] The lithium salt includes LiAsF 6 、LiPF 6 、LiClO 4 , LiTFSI, LiFSI and LiBF 4 One or more of .

[0089] The inorganic filler includes LATP, LLZO, Al 2 O 3 and one or more of a metal-organic framework.

[0090] The gel electrolyte includes at least one solid electrolyte in the above embodiments and at least one electrolyte solution in the above embodiments.

[0091] An embodiment of the present invention further provides an electrical device, comprising the battery as described in the above embodiment.

[0092] The composite current collector of the present invention is further described below in conjunction with specific embodiments.

[0093] Example 1

[0094] This embodiment is used to illustrate the composite current collector and pole piece disclosed in the present invention.

[0095] The active material layer covers part of the surface of the conductive layer on both sides of the composite current collector, and the connection area 5 is rectangular in shape, with a length L3 = 20 mm and a height M3 = 6 mm. The external tab area 6 has a length L4 = 10 mm and a width M4 = 20 mm.

[0096] Example 2

[0097] This embodiment is used to illustrate the composite current collector and pole piece disclosed in the present invention.

[0098] The active material layer covers part of the surface of the conductive layer on both sides of the composite current collector. The connection area 5 is stepped. The length of the first connection section 51 is L31 = 30 mm, and the height is M31 = 2 mm. The length of the second connection section 52 is L32 = 20 mm, and the height is M32 = 4 mm. The length of the external tab area 6 is L4 = 10 mm, and the width is M4 = 20 mm.

[0099] Example 3

[0100] This embodiment is used to illustrate the composite current collector and pole piece disclosed in the present invention.

[0101] The active material layer covers the entire surface of the conductive layer on both sides of the composite current collector. The active material area 3, the first transition area 41, and the first connection area 53 on both sides of the current collector 1 are coated with active material layers. The connection area 5 is in a stepped shape. The length of the first connection section 51 is L31 = 30 mm, and the height is M31 = 2 mm. The length of the second connection section 52 is L32 = 20 mm, and the height is M32 = 4 mm. The length of the external tab area 6 is L4 = 10 mm, and the width is M4 = 20 mm.

[0102] Comparative Example 1

[0103] This comparative example is used to illustrate the composite current collector and pole piece disclosed in the present invention.

[0104] The active material layer covers part of the surface of the conductive layer on both sides of the composite current collector, and the connection area 5 is rectangular in shape, with a length L3 = 10 mm and a height M3 = 6 mm. The external tab area 6 has a length L4 = 10 mm and a width M4 = 20 mm.

[0105] Performance Testing

[0106] In the above embodiments and comparative examples, lithium batteries are prepared according to the contents of this application and the disclosed schemes, and performance tests are carried out. For all embodiments and comparative examples, the pole piece size is fixed: the negative pole piece adopts a 3.5um pure copper current collector, the active material area size is 60*78mm, the blank area size is 60*2mm, a single-pole ear design is adopted, the pole ear area size is 10*12mm, the short side of the pole piece is connected to the short side of the pole ear, and the negative active material is a metal lithium with a thickness of 20μm. The positive pole piece adopts a 6.5μm PP composite aluminum current collector, the base film is a 4.5μm PET material, and the thickness of the metal conductive layer on both sides of the base film is 1μm; the positive electrode transfer pole ear belt is a pure aluminum belt with a thickness of 12μm and a width of 30mm. The size of the positive active material area M1*L1 is 58*76mm, the size of the blank area L2*M2 is 58*2mm, and a single-pole ear design is adopted. The positive and negative pole ears are facing each other. The positive electrode active material is high nickel ternary NCM811 with a surface capacity of 4 mAh / cm 2 . The electrolyte is 1 mol LiTFSI, 50% DOL + 50% DME. The injection volume is 2.5g / Ah; the diaphragm is a 10μm uncoated PP diaphragm; the thickness of the aluminum-plastic film is 113μm. The positive electrode adopts the composite current collector design in the above-mentioned embodiment and comparative example, and is assembled with the diaphragm, electrolyte, and aluminum-plastic film into a soft-pack laminated battery with 5 positive electrodes and 6 negative electrodes, respectively, with a cut-off voltage of 3-4.25V, and the 25°C room temperature rate performance test is carried out in the following test steps. Specific test data are shown in Table 1.

[0107] Table 1

[0108] serial number Energy density / Wh / kg Tabs@40℃ Example 1 407 <![CDATA[2C 5 th Loop]]> Example 2 401 Complete the process Example 3 408 Complete the process Comparative Example 1 410 <![CDATA[1C 3 rd Loop]]>

[0109] From the test results of Examples 1 to 3 and Comparative Example 1, it can be seen that the length of the connection area 5 for welding is increased compared with the external tab area 6, and the tab area temperature improvement effect under rate discharge in Examples 1 to 3 is obvious compared with Comparative Document 1. In particular, Example 2 in which the connection area 5 adopts a stepped design can complete a 5C rate cycle without a significant increase in the tab temperature.

[0110] By comparing Example 2 and Example 3, it can be seen that the connection area 5 and the external tab area 6 of the two are designed the same, but the active material in Example 3 covers the entire surface of the conductive layer. Therefore, while Example 3 has comparable rate discharge performance to Example 2, compared with Example 2, Example 3 also has an improvement in battery energy density.

[0111] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A composite current collector, characterized in that: The composite current collector comprises a current collector and two transfer tabs, wherein the two transfer tabs are respectively connected to the current collector, the composite current collector comprises a transition region, a connection region, an external tab region and an active material region for coating active materials, the transition region is connected between the active material region and the connection region, the connection region is the connection between the current collector and the transfer tab, and the external tab region is connected to a side of the connection region away from the transition region; The connection area includes a first connection segment and a second connection segment, the first connection segment is connected to the transition area, the second connection segment is connected to the external pole lug area, the length of the first connection segment is greater than the length of the external pole lug area, and the length of the second connection segment is greater than or equal to the length of the external pole lug area; or, the length of the first connection segment, the length of the second connection segment and the length of the external pole lug area are all equal to the width of the active material area.

2. The composite current collector according to claim 1, characterized in that: The length of the first connecting segment is greater than or equal to the second connecting segment; the length of the first connecting segment is less than or equal to the length of the transition zone; the length of the transition zone is less than or equal to the width of the active material zone.

3. The composite current collector according to claim 1, characterized in that: The width of the connection zone is 0 to 10 mm; and / or the width of the transition zone is 0 to 2 mm; and / or the length of the active material zone is 6 to 800 mm and the width is 4 to 600 mm.

4. The composite current collector according to any one of claims 1 to 3, characterized in that: The active material region is located on the current collector, and the external tab region is located on at least one of the transfer tabs; the current collector has a first transition region and a first connection region, and the first transition region is connected between the active material region and the first connection region; Each of the transfer tabs has a second transition region and a second connection region, the second transition region is connected to the second connection region, and the external tab region is connected to a side of the second connection region away from the second transition region; The second transition zone is located at one side of the first transition zone to form the transition zone; the second connection zone is located at one side of the first connection zone, and the second connection zone is connected to the first connection zone and then cut to form the connection zone.

5. The composite current collector according to claim 4, characterized in that: The height of the first transition zone is greater than or equal to the width of the second transition zone; the width of the first connection zone is greater than or equal to the width of the second connection zone.

6. The composite current collector according to claim 4, characterized in that: The switching tab is a copper-containing metal strip or an aluminum-containing metal strip, the copper-containing metal strip is a copper strip or a copper alloy strip, and the mass content of copper in the copper-containing metal strip is greater than or equal to 80%; The aluminum-containing metal strip is an aluminum strip or an aluminum alloy strip, and the mass content of aluminum in the aluminum-containing metal strip is greater than or equal to 80%.

7. The composite current collector according to claim 6, characterized in that: The transfer tab has a thickness of 3 to 12 μm and a width of 4 to 40 mm.

8. The composite current collector according to claim 7, characterized in that: The current collector and the transfer tab are welded by a welding head or crimped by a pressing head; The width of the welding head or the pressing head is a mm, 2≤a≤10; The widths of the two transfer tabs are the same or different, and the width of the wider transfer tab is ≥ (a+0.5) mm.

9. A pole piece, characterized in that: The composite current collector comprises an active material layer and any one of claims 4 to 8, wherein the current collector comprises a base film and conductive layers located on both sides of the base film, and the active material layer is arranged on a side of at least one of the conductive layers away from the base film.

10. The pole piece according to claim 9, characterized in that: When the active material layer completely covers the conductive layer, at least part of the surface of the active material region, the first transition region and the first connection region is provided with the active material layer; When the active material layer is disposed on a portion of the surface of the conductive layer, the active material layer is disposed on at least a portion of the surface of the active material region.

11. The pole piece according to claim 9, characterized in that: The base film has a thickness of 0.5 to 30 μm; and / or the conductive layer has a thickness of 0.1 to 15 μm.

12. The pole piece according to claim 9, characterized in that: The current collector is a positive electrode current collector, the conductive layer includes at least one of carbon materials, conductive polymers, copper, aluminum, gold, silver, iron, nickel, zinc and alloys thereof; the active material layer includes one or more of lithium nickel cobalt manganese oxide, lithium iron manganese phosphate, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium manganese rich base, lithium nickel manganese oxide and lithium vanadium phosphate.

13. The pole piece according to claim 9, characterized in that: The current collector is a negative electrode current collector, the conductive layer includes at least one of carbon materials, conductive polymers, lithium-containing metal strips, copper, aluminum, gold, silver, iron, nickel, zinc and alloys thereof; the negative electrode active material layer includes one or more of metallic lithium, lithium alloys, graphite, silicon, silicon carbon and silicon oxygen.

14. A battery, characterized in that: A pole piece comprising any one of claims 9 to 13.

15. The battery according to claim 14, characterized in that The battery is a liquid battery, a semi-solid battery or a solid battery.

16. An electrical device, characterized in that: Comprising the battery according to claim 14 or 15.

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