Current collector, electrode sheet including the current collector, and electrochemical device

Abstract

The present invention provides a current collector, an electrode sheet including the current collector, and an electrochemical device. The current collector of the present invention includes an insulating layer, a metal conductive layer, and a non-metallic conductive layer; the metal conductive layer is disposed on at least one functional surface of the insulating layer, and the non-metallic conductive layer is disposed on a functional surface of the metal conductive layer away from the insulating layer; the metal conductive layer includes a plurality of metal conductive units, and the plurality of metal conductive units are spaced apart on the insulating layer. When the current collector of the present invention is abused by needle puncture, the insulating layer undergoes tensile deformation, and since the plurality of metal conductive units are spaced apart on the insulating layer, the impedance of the ruptured area of ​​the current collector will rise sharply, reducing heat generation, thereby preventing the occurrence of thermal runaway.

Description

Technical Field

[0001] The present invention belongs to the field of batteries and relates to a current collector and an electrode sheet and an electrochemical device comprising the current collector. Background Art

[0002] Lithium-ion batteries are widely used secondary batteries, and safety performance is an important topic in lithium-ion battery research.

[0003] The needle penetration test is a critical safety indicator for lithium-ion batteries. Conventional lithium-ion batteries use metal foil as the current collector, typically aluminum foil for the positive electrode and copper foil for the negative electrode. During the needle penetration test, the current collector ruptures and stretches, forming a funnel-shaped fracture surface. This causes the current collector to contact the electrodes, resulting in a short circuit, which in turn leads to intense heat generation and ultimately thermal runaway.

[0004] Therefore, how to develop a new type of current collector that can effectively reduce the probability of short circuit caused by current collector rupture during the puncture process, thereby significantly improving the pass rate of the puncture test and improving the safety performance of the battery is a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The present invention provides a current collector, which has a special structure design so that the current collector has good safety performance during a needle penetration test and is not prone to thermal runaway.

[0006] The present invention also provides an electrode sheet and an electrochemical device. Since they include the above-mentioned current collector, the electrode sheet and the electrochemical device also have good safety performance, especially a high pass rate in the needle penetration abuse test, and are not prone to thermal runaway.

[0007] A first aspect of the present invention provides a current collector. Figure 1 This is a schematic structural diagram of a current collector provided by one embodiment of the present invention. Figure 2 A schematic diagram of the structure of a current collector provided in another embodiment of the present invention is shown in FIG. Figure 1 and Figure 2 As shown, the current collector of the present invention includes an insulating layer 101, a metal conductive layer 102 and a non-metallic conductive layer 103, wherein the metal conductive layer 102 is disposed on at least one functional surface of the insulating layer 101, and the non-metallic conductive layer 103 is disposed on a functional surface of the metal conductive layer 102 away from the insulating layer 101;

[0008] The metal conductive layer 102 includes a plurality of metal conductive units, and the plurality of metal conductive units are distributed at intervals on the insulating layer 101 .

[0009] The functional surfaces of the insulating layer 101 and the metal conductive layer 102 refer to the two largest surfaces of the insulating layer 101 and the metal conductive layer 102, respectively. The metal conductive layer 102 and the non-metal conductive layer 103 of the present invention can be provided on only one side of the insulating layer 101 (e.g. Figure 1 ), or may be provided on both sides of the insulating layer 101 (eg Figure 2 ).

[0010] The plurality of metal conductive units distributed at intervals on the insulating layer 101 refers to the plurality of metal conductive units existing independently and not connected to each other, and current cannot be conducted in the interval area. The present invention does not specifically limit the form of the plurality of metal conductive units distributed at intervals on the insulating layer 101. Figures 3 to 7 Schematic diagrams of the metal conductive layer of the current collector according to an embodiment of the present invention, wherein the black area represents a plurality of metal conductive units, and the blank area represents a region without metal conductive units, such as Figures 3 to 7 As shown, several metal conductive units can be distributed in a grid-like manner (such as Figure 3 ), or it can be distributed as stripes (e.g. Figure 4 ), can also be presented as island-like interval distribution (such as Figure 5 ), or appear as circular intervals (such as Figure 6 ), or can be presented as a honeycomb hexagonal distribution (such as Figure 7 ).

[0011] Generally speaking, the conductivity of metal materials is much greater than that of non-metallic materials. Therefore, if only a non-metallic conductive layer is covered on the surface of the insulating layer, the conductivity of the current collector will be very poor, thereby affecting the rate performance of the battery; if a continuous metal conductive layer is covered on the surface of the insulating layer, the conductivity of the current collector will be too high, and the metal conductive layer will be difficult to break when it is stretched and deformed, so that the current collector always maintains high conductivity and cannot cut off the current transmission in time, which is prone to thermal runaway and insufficient battery safety performance; if only a discontinuously distributed metal conductive layer is covered on the surface of the insulating layer, the current collector will not work normally because the current cannot be transmitted normally.

[0012] Based on the above considerations, the current collector designed in the present invention first arranges a metal conductive layer with several metal conductive units spaced apart on the surface of the insulating layer, and then arranges a non-metallic conductive layer on the surface of the metal conductive layer. Through the combination of the spaced apart metal conductive layer and the non-metallic conductive layer with lower conductivity, the current collector obtains moderate conductivity and can perform normal current transmission. Moreover, since several metal conductive units are spaced apart on the insulating layer, during the needle puncture abuse test, after the insulating layer undergoes tensile deformation, both the metal conductive layer and the non-metallic conductive layer can be easily broken, and the impedance of the broken area will rise sharply, thereby reducing the heat release generated by the battery short circuit, preventing the battery from experiencing thermal runaway, and thus ensuring the safety of the battery.

[0013] It is understandable that the greater the proportion of the total area of ​​the plurality of metal conductive units to the area of ​​the insulating layer, the better the conductivity of the current collector, but at the same time the safety performance will be slightly worse. Depending on the conductivity and safety requirements of the battery, the total area of ​​the plurality of metal conductive units can be adjusted to the area of ​​the insulating layer within a range of 50% to 98%. Exemplarily, the proportion of the total area of ​​the plurality of metal conductive units to the area of ​​the insulating layer is 50%, 60%, 70%, 80%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or any point within the range of the aforementioned values.

[0014] Furthermore, the spacing between each two adjacent metal conductive units is d, and 0.001mm<d<0.5mm. Controlling d within this range helps the current collector achieve both good conductivity and safety. Exemplarily, the spacing d between each two adjacent metal conductive units is 0.001mm, 0.005mm, 0.01mm, 0.05mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.4mm, 0.5mm, or any value within the range of any two of the foregoing values.

[0015] In a specific embodiment, the thickness of the insulating layer of the present invention is 1 to 20 μm, examples of which are 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm or any point within the range of any two of the aforementioned values.

[0016] In a specific embodiment, the thickness of the metal conductive layer of the present invention is 50nm to 3μm, exemplified by 50nm, 100nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm or any point within the range composed of any two of the foregoing values.

[0017] In a specific embodiment, the thickness of the non-metallic conductive layer of the present invention is 1-5 μm, exemplified by 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any point within the range consisting of any two of the aforementioned values.

[0018] The material of the insulating layer of the present invention is selected from organic polymers, or a mixture of organic polymers and inorganic fillers.

[0019] When selected from a mixture of organic polymers and inorganic fillers, the inorganic filler can enhance the strength of the insulating layer. Furthermore, while inorganic fillers also have insulating properties, their flexibility is inferior to that of organic polymers, so a small amount is sufficient. Therefore, to improve the strength of the insulating layer, the mass of the inorganic filler can be controlled to account for 0.01% to 5% of the insulating layer's mass. Exemplarily, the mass content of the inorganic filler in the insulating layer is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or any value within a range consisting of any two of the aforementioned values.

[0020] If the particles of the inorganic filler are too large, the mechanical strength of the insulating layer will decrease. When the particle size of the inorganic filler is greater than the thickness of the insulating layer, the inorganic filler will not be completely embedded in the polymer, resulting in it being unusable. When the particles of the inorganic filler are too small, the difficulty of dispersing the inorganic filler in the polymer will increase. In summary, the average particle size D50 of the inorganic filler of the present invention is controlled to be 5 to 1000 mm, and / or, preferably, the D99 particle size of the inorganic filler is also controlled to be within the range of 5 to 1000 nm. Exemplarily, the average particle size D50 of the inorganic filler in the insulating layer is 5 nm, 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm or any point value within the range composed of any two of the above values.

[0021] The above-mentioned organic polymer is selected from at least one of poly(terephthalate), polyamide, polyimide (PI), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), poly(p-phenylene terephthalamide), polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl formal, polyvinyl butyral, polyurethane, polyacrylonitrile, polyvinyl acetate, polyoxymethylene, phenolic resin, epoxy resin, acrylic resin, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), silicone rubber, polycarbonate, polysulfone, polyethersulfone, and polyphenylene ether, preferably poly(terephthalate) and / or polypropylene.

[0022] The above-mentioned inorganic filler is selected from at least one of aluminum oxide, silicon carbide, silicon oxide, glass fiber, titanium dioxide, zirconium dioxide, magnesium hydroxide, aluminum hydroxide, boehmite, barium sulfate, barium titanate, aluminum titanate, zinc oxide, boron nitride, aluminum nitride, magnesium nitride, attapulgite, zinc phosphate, zinc borate, and graphene oxide.

[0023] The material of the metal conductive layer of the present invention is selected from at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, aluminum-zirconium alloy, and stainless steel, preferably at least one of aluminum and copper.

[0024] The non-metallic conductive layer of the present invention comprises a carbon-based conductive agent and a binder. The carbon-based conductive agent is selected from at least one of conductive carbon black, graphene, carbon nanotubes, and carbon fibers, preferably at least one of acetylene black, SuperP, and Ketjen Black. The binder is selected from at least one of polyvinylidene fluoride, polyacrylic acid, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polytetrafluoroethylene, and polyimide.

[0025] Furthermore, the mass fraction of the binder in the non-metallic conductive layer is 20% to 95%, preferably 60% to 90%. Exemplarily, the mass fraction of the binder in the non-metallic conductive layer is 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or any point in the range of any two of the foregoing values.

[0026] To further enhance the safety of the battery, in addition to the carbon-based conductive agent and binder, inorganic powder may be added to the non-metallic conductive layer. Preferably, the mass fraction of the inorganic powder in the non-metallic conductive layer is 0.1% to 40%. Exemplarily, the mass fraction of the inorganic powder in the non-metallic conductive layer is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, or any value within a range consisting of any two of the aforementioned values.

[0027] Specifically, the inorganic powder is selected from at least one of aluminum oxide, silicon oxide, titanium oxide, calcium oxide, zinc oxide, magnesium oxide, yttrium oxide, hafnium oxide, zirconium oxide, tin oxide, cerium oxide, nickel oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, boehmite, barium sulfate, fluorphlogopite, fluoroapatite, apatite, mullite, aluminum titanate, calcium carbonate, silicon carbide, silicon nitride, cubic boron nitride, hexagonal boron nitride, graphene oxide, mesoporous molecular sieve, aluminum nitride, magnesium nitride, attapulgite, cerium titanate, calcium titanate, barium titanate, zinc phosphate, zinc borate, lithium phosphate, lithium borate, lithium silicate, lithium sulfate, perovskite-type electrolyte, Garnet-type electrolyte, and NASICON-type electrolyte.

[0028] The molecular formula of the above perovskite electrolyte is Li 3z La 2 / 3-z TiO3, wherein 0<z<2 / 3; the molecular formula of the above-mentioned Garnet-type electrolyte is Li 7-a La3Zr 2-a M a O 12 , is a garnet structure, wherein M is Ta, Nb or W, 0≤a≤2; the molecular formula of the above-mentioned NASICON type solid electrolyte is Li 1+x+y Al x (Ti m Zr n Ge r ) 2-x Si y P 3-y O 12 , where 0≤x≤2, 0≤y≤3, 0≤m≤1, 0≤n≤1, 0≤r≤1, m+n+r=1, or the molecular formula is Li 1+2x Zr 2-x Ca x (PO4)3, where 0.1≤x≤0.4.

[0029] Furthermore, if the particles of the inorganic powder are too large, the non-metallic conductive layer will be uneven, affecting the integrity of the non-metallic conductive layer, deteriorating the conductive network, and affecting the conductivity of the non-metallic conductive layer. When the particles of the inorganic powder are too small, the inorganic powder is prone to agglomeration. Taking the above into consideration, the average particle size D50 of the inorganic powder of the present invention is controlled to be 5 to 1000 nm, and / or, it is preferred that the D99 particle size is simultaneously controlled within the range of 5 to 1000 nm.

[0030] The outermost layer of the current collector of the present invention utilizes a non-metallic conductive layer. The conductivity of the non-metallic conductive layer is much lower than that of the metallic conductive layer. Therefore, the surface resistance of the current collector is relatively high, which facilitates higher battery safety. Preferably, the surface resistance of the current collector of the present invention is ≥5Ω / □, and more preferably, the surface resistance of the current collector of the present invention is between 5Ω / □ and 2000Ω / □.

[0031] The present invention does not specifically limit the preparation method of the current collector, and conventional methods in the art can be adopted. For example, a metal conductive layer is first formed on the insulating layer by at least one of bonding, vapor deposition, electroless plating, and electroplating, and then the components in the non-metal conductive layer are formulated into a slurry and coated on the metal conductive layer, and the current collector of the present invention can be obtained after drying; wherein, the spaced distribution pattern of several metal conductive units in the metal conductive layer can be achieved by first forming a continuous metal conductive layer on the insulating layer and then etching part of the metal by local etching, or by locally shielding the surface of the insulating layer and then plating the metal on the surface of the insulating layer by means of vapor deposition, electroless plating, electroplating, etc.

[0032] The second aspect of the present invention provides an electrode sheet, which includes the current collector provided by the first aspect of the present invention.

[0033] The electrode sheet of the present invention can be a positive electrode sheet or a negative electrode sheet.

[0034] The above positive electrode sheet includes a current collector and a positive electrode active layer. The positive electrode active layer at least includes a positive electrode active material, and may further include components such as a conductive agent and a binder.

[0035] The present invention does not specifically limit the type of the positive electrode active material, as long as it can reversibly insert and extract lithium ions. Specifically, the positive electrode active material can be a lithium transition metal composite oxide, wherein the transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Ti, Zn, V, Al, Zr, Ce, and Mg. In order to make the positive electrode active material have high structural stability and electrochemical performance, elements with high electronegativity, such as one or more of S, F, Cl, and I, can also be doped in the lithium transition metal composite oxide. Exemplarily, the lithium transition metal composite oxide is selected from LiNi 1-y Co y O2(0 < y < 1), LiNi a Co b Al 1-a-b O2(0 < a < 1, 0 < b < 1, 0 < a + b < 1), LiMn2O4, LiNiO2, LiCoO2, LiMn 1-m-n Ni m Co n O2(0 < m < 1, 0 < n < 1, 0 < m + n < 1), LiMPO4 (M is selected from one or more of Fe, Mn, and Co), and one or more of Li3V2(PO4)3.

[0036] Conductive agents in the positive electrode active layer include, but are not limited to, carbon-based materials, metal-based materials, conductive polymers, or mixtures thereof. In some embodiments, the carbon-based material is selected from one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the metal-based material is selected from metal powders or metal fibers of copper, nickel, aluminum, silver, and the like. In some embodiments, the conductive polymer is selected from polyphenylene derivatives.

[0037] The binder in the positive electrode active layer can be selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile rubber (NBR), aqueous acrylic resin, polyvinyl alcohol, polyvinyl butyral, polyurethane, fluorinated rubber, carboxymethyl cellulose (CMC), and polyacrylic acid (PAA).

[0038] The positive electrode sheet can be prepared according to conventional methods in the art. Generally, the positive electrode active material and components such as the conductive agent and the binder are dispersed in a solvent (such as N-methylpyrrolidone) to form a uniform positive electrode slurry. The positive electrode slurry is then coated on the positive electrode current collector. After drying and other processes, the positive electrode sheet is obtained.

[0039] The negative electrode sheet includes a current collector and a negative electrode active layer. The negative electrode active layer includes at least a negative electrode active material and may further include components such as a conductive agent and a binder.

[0040] The negative electrode active material of the present invention can adopt conventional negative electrode active materials in the field, for example, it can be one or more of metallic lithium, natural graphite, artificial graphite, mesophase microcarbon beads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structured lithium titanate and Li-Al alloy.

[0041] The selectable range of the conductive agent in the negative electrode active layer is the same as that in the positive electrode active layer, and will not be described in detail here.

[0042] The binder in the negative electrode active layer can be selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile rubber (NBR), aqueous acrylic resin, polyvinyl alcohol, polyvinyl butyral, polyurethane, fluorinated rubber, carboxymethyl cellulose (CMC), polyacrylic acid (PAA), epoxy resin, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl pyrrolidone, and nylon.

[0043] The negative electrode sheet can be prepared by referring to conventional methods in the art, for example, dispersing the negative electrode active material, conductive agent, binder and other components in a solvent (such as water) to form a uniform negative electrode slurry, and then coating the negative electrode slurry on the negative electrode collector. After drying and other processes, the negative electrode sheet is obtained.

[0044] In order to obtain higher energy density, the negative electrode sheet is preferably a metal lithium negative electrode sheet and a negative electrode sheet of an alloy containing metal lithium. The specific preparation method is: in a low humidity environment (usually in a dry room with a dew point temperature below -30°C), a roller press or other pressing equipment is used to mechanically press the metal lithium strip (foil), lithium alloy strip (foil) and current collector, so that the metal lithium strip (foil), lithium alloy strip (foil) and current collector are tightly attached together, leaving a certain blank area on the edge of the current collector for subsequent electrode ear welding.

[0045] A third aspect of the present invention provides an electrochemical device comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet and / or the negative electrode sheet is the electrode sheet provided by the second aspect of the present invention.

[0046] There is no particular limitation on the above-mentioned isolation membrane. Any known porous structure isolation membrane with electrochemical stability and chemical stability can be selected, for example, it can be a single-layer or multi-layer film of one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0047] The electrolyte solution includes an organic solvent and an electrolyte salt. The organic solvent, serving as a medium for transporting ions during the electrochemical reaction, can be any organic solvent known in the art for use in electrochemical device electrolytes. The electrolyte salt, serving as a source of ions, can be any electrolyte salt known in the art for use in electrochemical device electrolytes.

[0048] The organic solvent in the above electrolyte can be ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), difluoroethylene carbonate (DFEC), dimethyl fluorocarbonate, ethyl methyl fluorocarbonate, ethylpropyl carbonate (EPC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methylpropyl carbonate (MPC), methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate (EA), propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate Ester, methyl difluoroacetate, ethyl difluoroacetate, γ-butyrolactone (GBL), γ-valerolactone, δ-valerolactone, ethylene glycol dimethyl ether (DME), triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, fluoroether F-EPE, fluoroether D2, fluoroether HFPM, fluoroether MFE, fluoroether EME, tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,3-dioxolane (DOL), 1,4-dioxane (DOX), sulfolane, dimethyl sulfoxide (DMSO), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), diethyl sulfone (ESE), dichloromethane, and one or more of dichloroethane are mixed in any proportion.

[0049] The electrolyte salt in the above-mentioned electrolyte solution can be lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluoroantimonate (LiSbF6), lithium difluorophosphate (LiPF2O2), 4,5-dicyano-2-trifluoromethylimidazolium lithium (LiDTI), lithium bis(oxalato)borate (LiBOB), lithium bis(malonate)borate (LiBMB), lithium difluorooxalatoborate (LiDFOB), lithium bis(difluoromalonate)borate (LiBDFMB), lithium (malonate oxalate)borate (LiMOB), lithium (difluoromalonate oxalate)borate (LiBMB ... LiDFMOB), lithium tetracyanoborate, lithium tetrakis(trifluoromethyl)borate, lithium pentafluoroethyl trifluoroborate, lithium dicyanooxalatoborate, lithium bismalonate borate, lithium tris(oxalato)phosphate (LiTOP), lithium tris(difluoromalonate)phosphate (LiTDFMP), lithium tetrafluorooxalatophosphate (LiTFOP), lithium difluorobisoxalatophosphate (LiDFOP), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (LiN(SO2F)(SO2CF3)), lithium nitrate (LiNO3), lithium fluoride (LiF), LiN(SO2C n F 2n+1 )2、LiN(SO2F)(SO2C n F 2n+1) (n is an integer of 2 to 10) are mixed in any proportion.

[0050] The positive electrode sheet, separator, and negative electrode sheet are stacked or wound in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation to obtain a battery cell; the battery cell is placed in a packaging shell, injected with electrolyte and sealed to prepare an electrochemical device.

[0051] The present invention also provides applications of the electrochemical device. The electrochemical device of the present invention can be used in various well-known applications. For example, it can be applied to mobile computers, laptop computers, mobile phones, e-book players, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD televisions, portable cleaners, calculators, memory cards, portable recorders, radios, backup power supplies, automobiles, motorcycles, electric boats, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, cameras, large household batteries, energy storage power stations, and the like.

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] 1. The current collector of the present invention is formed by arranging a metal conductive layer with a plurality of metal conductive units spaced apart on the surface of the insulating layer, and then arranging a non-metallic conductive layer on the surface of the metal conductive layer. The combination of the spaced apart metal conductive layer and the non-metallic conductive layer with lower conductivity enables the battery to obtain higher safety performance. Since the plurality of metal conductive units in the metal conductive layer are spaced apart, during the needle puncture abuse process, the insulating layer undergoes tensile deformation, and the impedance of the entire current collector in the rupture area will increase sharply, thereby reducing the heat generated by the short circuit in the rupture area and avoiding thermal runaway of the battery.

[0054] 2. Since the electrochemical device of the present invention includes an electrode sheet containing the above-mentioned current collector, the electrochemical device has higher safety performance, especially a higher pass rate in the needle penetration abuse test. At the same time, the electrochemical device also has lower impedance and higher rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a schematic structural diagram of a current collector according to an embodiment of the present invention;

[0056] Figure 2 This is a schematic structural diagram of a current collector according to another embodiment of the present invention;

[0057] Figure 3 Schematic diagram of a metal conductive layer of a current collector according to an embodiment of the present invention;

[0058] Figure 4 Schematic diagram of a metal conductive layer of a current collector according to an embodiment of the present invention;

[0059] Figure 5 Schematic diagram of a metal conductive layer of a current collector according to an embodiment of the present invention;

[0060] Figure 6 Schematic diagram of a metal conductive layer of a current collector according to an embodiment of the present invention;

[0061] Figure 7 Schematic diagram of a metal conductive layer of a current collector according to an embodiment of the present invention;

[0062] Figure 8 Schematic diagram of the metal conductive layer of the current collector according to a pair of ratios of the present invention.

[0063] Description of reference numerals:

[0064] 101: insulation layer;

[0065] 102: metal conductive layer;

[0066] 103: Non-metallic conductive layer. DETAILED DESCRIPTION

[0067] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0068] Unless otherwise stated, the percentages and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are commercially available.

[0069] 1. Preparation of current collector

[0070] Example 1

[0071] The preparation method of the current collector of this embodiment includes the following steps:

[0072] 1) Select a PET film with a thickness of 4.5 μm as the insulating layer;

[0073] 2) A plain woven stainless steel mesh (wire diameter 0.3 mm, pore size 0.8 mm) was used to cover the surface of the PET film for shielding. A metal aluminum layer was deposited on both surfaces of the PET film by vacuum coating. The thickness of the aluminum layer was 1 μm. The deposited aluminum layer consisted of several discontinuous grids (distribution form refers to Figure 6 ) of a metal aluminum unit;

[0074] 3) A non-metallic conductive layer with a thickness of 3 μm is coated on the surface of the aluminum layer by gravure roller coating. The formula of the non-metallic conductive layer slurry is: 0.5 wt% carbon nanotubes + 0.5 wt% CMC + 99 wt% deionized water. The final current collector is recorded as Z1.

[0075] Example 2

[0076] The preparation method of the current collector in this embodiment is basically the same as that in Example 1, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.5wt% carbon nanotubes + 2wt% PVDF + 97.5wt% NMP, and the final current collector is recorded as Z2.

[0077] Example 3

[0078] The preparation method of the current collector in this embodiment is basically the same as that in Example 1, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.1wt% carbon nanotubes + 0.9wt% acetylene black + 1wt% CMC + 98wt% deionized water, and the final current collector is recorded as Z3.

[0079] Example 4

[0080] The preparation method of the current collector in this embodiment is basically the same as that in Example 1, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.5wt% graphene + 0.5wt% acetylene black + 1wt% CMC + 98wt% deionized water, and the final current collector is recorded as Z4.

[0081] Example 5

[0082] The preparation method of the current collector in this embodiment is basically the same as that in Example 1, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.5wt% carbon nanotubes + 2wt% PVDF + 97.5wt% NMP, and the final current collector is recorded as Z5.

[0083] Example 6

[0084] The preparation method of the current collector in this embodiment is basically the same as that in Example 1, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.5wt% carbon nanotubes + 2wt% PVDF + 0.2wt% nano-alumina (average particle size D50 is 800nm, particle size D99 is 890nm) + 97.3wt% NMP, and the final current collector is recorded as Z6.

[0085] Example 7

[0086] The preparation method of the current collector in this embodiment is basically the same as that in Example 1, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.5wt% carbon nanotubes + 2wt% PVDF + 0.8wt% Garnet-type electrolyte (specifically lithium lanthanum zirconium tantalum oxide LLZTO, with an average particle size D50 of 600nm and a particle size D99 of 920nm) + 96.7wt% NMP, and the final current collector is recorded as Z7.

[0087] Example 8

[0088] The preparation method of the current collector in this embodiment is basically the same as that in Example 1, except that, in step 1), the PET film used for the insulating layer is mixed with 1% by mass of nano-silicon oxide with an average particle size D50 of 50 nm and a particle size D99 of 80 nm; in step 3), the formula of the coated non-metallic conductive layer slurry is 0.5wt% carbon nanotubes + 0.5wt% CMC + 0.6wt% NASICON type electrolyte (specifically lithium aluminum titanium phosphate LATP, with an average particle size D50 of 300 nm and a particle size D99 of 600 nm) + 98.4wt% deionized water, and the final current collector is recorded as Z8.

[0089] Example 9

[0090] The preparation method of the current collector of this embodiment includes the following steps:

[0091] 1) Select a PET film with a thickness of 4.5 μm as the insulating layer;

[0092] 2) A metal aluminum layer is deposited on both surfaces of the PET film by vacuum coating, and the thickness of the aluminum layer is 1 μm. A grid-shaped paraffin protective layer (the grid shape is square, the grid side length is 0.2 mm, and the distance between each two adjacent grids is 0.05 mm) is sprayed on the surface of the metal aluminum layer. The metal aluminum layer sprayed with the paraffin protective layer is then immersed in 0.5 mol / L sodium hydroxide alkali solution to etch the metal aluminum. After the etching is completed, the residual alkali solution is removed by washing with deionized water, and the paraffin protective layer is removed by washing with petroleum ether to obtain a plurality of discontinuous grid distributions (the distribution form is referenced). Figure 3 ) of a metal aluminum unit;

[0093] 3) A non-metallic conductive layer with a thickness of 3 μm is coated on the surface of the aluminum layer by gravure roller coating. The formula of the non-metallic conductive layer slurry is: 0.5 wt% carbon nanotubes + 0.5 wt% CMC + 99 wt% deionized water. The final current collector is recorded as Z9.

[0094] Example 10

[0095] The preparation method of the current collector of this embodiment includes the following steps:

[0096] 1) Select a PET film with a thickness of 4.5 μm as the insulating layer;

[0097] 2) A metal aluminum layer with a thickness of 8 μm was bonded to the insulating layer by a polyurethane adhesive, and then the metal aluminum layer was slowly corroded in a 0.5 mol / L sodium hydroxide solution until the thickness of the metal aluminum layer was 0.8 μm. Due to the uneven corrosion, the resulting metal aluminum layer included several discrete "island-like" distributions (distribution form reference Figure 5 ) of the metal aluminum unit, the average distance between each two adjacent metal aluminum units is 0.22 mm, and then washed with deionized water to remove residual alkali solution;

[0098] 3) A 3 μm thick non-metallic conductive layer was coated on the surface of the aluminum layer by gravure roller coating, wherein the coating slurry formula was: 0.5 wt% carbon nanotubes + 0.5 wt% CMC + 99 wt% deionized water, and the final current collector was recorded as Z10.

[0099] Example 11

[0100] The preparation method of the current collector of this embodiment includes the following steps:

[0101] 1) Select a PET film with a thickness of 2 μm as the insulating layer;

[0102] 2) A metal aluminum layer with a thickness of 8 μm was bonded to the insulating layer by a polyurethane adhesive, and then a protective layer (the material of the protective layer was an etching protective glue) with a spaced square grid (the grid side length was 0.2 mm, and the distance between each two adjacent grids was 0.05 mm) was sprayed on the surface of the metal aluminum layer. The metal aluminum layer was then immersed in 0.5 mol / L sodium hydroxide alkali solution to etch it. After washing with deionized water to remove the residual alkali solution, it was washed with NMP to remove the etching protective glue, and a plurality of grid-like discontinuous distributions (distribution form reference Figure 3 ) of the metal aluminum layer of the metal aluminum unit;

[0103] 3) A 2 μm thick non-metallic conductive layer was coated on the surface of the aluminum layer by gravure roller coating, wherein the coating slurry formula was: 0.5 wt% carbon nanotubes + 0.5 wt% CMC + 99 wt% deionized water. The final current collector was denoted as Z11.

[0104] Comparative Example 1

[0105] The preparation method of the current collector of this comparative example comprises the following steps:

[0106] 1) Select a PET film with a thickness of 2 μm as the insulating layer;

[0107] 2) A 3 μm thick metal aluminum layer was bonded to the insulating layer by a polyurethane adhesive, and then a continuously distributed square mesh protective layer (the material of the protective layer was an etching protective glue) was sprayed on the surface of the metal aluminum layer (the side length of the grid hole in the unsprayed area was 0.2 mm, and the distance between each two adjacent grid holes was 0.05 mm). The metal aluminum layer was then immersed in 0.5 mol / L sodium hydroxide alkali solution to etch it. After washing with deionized water to remove the residual alkali solution, it was washed with NMP to remove the etching protective glue, and a grid-like continuous distribution was obtained (the distribution form refers to Figure 8 ) of a metallic aluminum layer;

[0108] 3) A 2 μm thick non-metallic conductive layer was coated on the surface of the aluminum layer by gravure roller coating, wherein the coating slurry formula was: 0.5 wt% carbon nanotubes + 0.5 wt% CMC + 99 wt% deionized water, and the final current collector was recorded as Z12.

[0109] Comparative Example 2

[0110] The preparation method of the current collector of this comparative example comprises the following steps:

[0111] 1) Select a PET film with a thickness of 4.5 μm as the insulating layer;

[0112] 2) A metal aluminum layer was deposited on both surfaces of the PET film by vacuum coating. The thickness of the aluminum layer was 1 μm. The final current collector was designated as Z13.

[0113] Comparative Example 3

[0114] The preparation method of the current collector of this comparative example comprises the following steps:

[0115] 1) Select a PET film with a thickness of 4.5 μm as the insulating layer;

[0116] 2) depositing a metal aluminum layer on both surfaces of the PET film by vacuum coating, with a thickness of 1 μm;

[0117] 3) A non-metallic conductive layer with a thickness of 3 μm is coated on the surface of the aluminum layer by gravure roller coating. The formula of the non-metallic conductive layer slurry is: 0.5 wt% carbon nanotubes + 0.5 wt% CMC + 99 wt% deionized water. The final current collector is recorded as Z14.

[0118] Example 12

[0119] The preparation of the current collector of this embodiment includes the following steps:

[0120] 1) A biaxially oriented polypropylene film (BOPP) with a thickness of 4 μm was selected as the insulating layer;

[0121] 2) Use a plain woven stainless steel mesh (wire diameter 0.1mm, aperture 0.5mm) to cover the surface of the BOPP film for shielding, and then deposit a metal copper layer on both surfaces of the BOPP film by sputtering. The copper layer deposition thickness is 0.5μm, and the deposited copper layer includes several discontinuous grid distributions (distribution form refers to Figure 6 ) of a metallic copper unit;

[0122] 3) A 2 μm thick non-metallic conductive layer was coated on the surface of the copper layer by gravure roller coating, wherein the coating slurry formula was: 1 wt% carbon nanotubes + 1 wt% CMC + 98 wt% deionized water. The final current collector was recorded as F1.

[0123] Example 13

[0124] The preparation method of the current collector in this embodiment is basically the same as that in Example 12, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 1wt% carbon nanotubes + 2wt% PVDF + 97wt% NMP, and the final current collector is recorded as F2.

[0125] Example 14

[0126] The preparation method of the current collector in this embodiment is basically the same as that in Example 12, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.2wt% carbon nanotubes + 0.8wt% Ketjen black + 1wt% CMC + 0.5wt% SBR + 97.5wt% deionized water, and the final current collector is recorded as F3.

[0127] Example 15

[0128] The preparation method of the current collector in this embodiment is basically the same as that in Example 12, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.5wt% graphene + 0.5wt% acetylene black + 1wt% CMC + 98wt% deionized water, and the final current collector is recorded as F4.

[0129] Example 16

[0130] The preparation method of the current collector in this embodiment is basically the same as that in Example 12, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 1wt% carbon nanotubes + 2wt% PVDF + 97wt% NMP, and the final current collector is recorded as F5.

[0131] Example 17

[0132] The preparation method of the current collector in this embodiment is basically the same as that in Example 12, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.5wt% carbon nanotubes + 2wt% PVDF + 0.2wt% nano-alumina (average particle size D50 is 200nm, particle size D99 is 300nm) + 97.3wt% NMP, and the final current collector obtained is F6.

[0133] Example 18

[0134] The preparation method of the current collector in this embodiment is basically the same as that in Example 12, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.5wt% carbon nanotubes + 2wt% PVDF + 0.8wt% Garnet-type electrolyte (specifically lithium lanthanum zirconium niobium oxide LLZNO, with an average particle size D50 of 400nm and a particle size D99 of 790nm) + 96.7wt% NMP, and the final current collector is F7.

[0135] Example 19

[0136] The preparation method of the current collector in this embodiment is basically the same as that in Example 12, except that in step 3), the formula of the coated non-metallic conductive layer slurry is 0.5wt% carbon nanotubes + 0.5wt% polyacrylic acid + 0.5wt% SBR + 0.5wt% NASICON type electrolyte (specifically lithium aluminum titanium phosphate LATP, with an average particle size D50 of 600nm and a particle size D99 of 930nm) + 98wt% deionized water, and the final current collector obtained is F8.

[0137] Example 20

[0138] The preparation method of the current collector of this embodiment includes the following steps:

[0139] 1) A biaxially oriented polypropylene film (BOPP) with a thickness of 4 μm was selected as the insulating layer;

[0140] 2) A plain woven stainless steel mesh (wire diameter 0.1 mm, pore size 0.5 mm) was used to cover the surface of the BOPP film for shielding. Then, a metal copper layer was deposited on both surfaces of the BOPP film by sputtering. The copper layer was deposited to a thickness of 50 nm. Then, a 950 nm thick metal copper layer was deposited on the 50 nm deposited copper layer by electroplating (the total thickness of the deposited copper layer was 1 μm). The deposited metal copper layer included several discontinuous grid distributions (the distribution form refers to Figure 6 ) of a metallic copper unit;

[0141] 3) A 2 μm thick non-metallic conductive layer was coated on the surface of the copper layer by gravure coating, wherein the coating slurry formula was: 1 wt% carbon nanotubes + 2 wt% PVDF + 97 wt% NMP, and the final current collector was recorded as F9.

[0142] Example 21

[0143] The preparation method of the current collector of this embodiment includes the following steps:

[0144] 1) A biaxially oriented polypropylene film (BOPP) with a thickness of 4 μm was selected as the insulating layer;

[0145] 2) A metal copper layer was deposited on both surfaces of the BOPP film by sputtering, with a thickness of 0.5 μm. A grid-shaped paraffin protective layer (the grid shape was square, the side length was 0.4 mm, and the spacing between each two adjacent grids was 0.1 mm) was sprayed on the surface of the metal copper layer. The metal copper was then etched in a 0.1 mol / L nitric acid solution. After etching, the residual acid was removed by washing with deionized water, and then the paraffin protective layer was removed by washing with petroleum ether to obtain a plurality of discontinuous grid distributions (the distribution form is referenced). Figure 3 ) of a metallic copper unit;

[0146] 3) A 2 μm thick non-metallic conductive layer was coated on the surface of the copper layer by gravure roller coating. The formula of the non-metallic conductive layer slurry was: 0.5 wt% carbon nanotubes + 0.5 wt% CMC + 99 wt% deionized water. The final current collector was denoted as F10.

[0147] Example 22

[0148] The preparation method of the current collector of this embodiment includes the following steps:

[0149] 1) A biaxially oriented polypropylene film (BOPP) with a thickness of 4 μm was selected as the insulating layer;

[0150] 2) A metal copper layer was deposited on both surfaces of the BOPP film by sputtering, with a thickness of 0.5 μm. A grid-shaped PVDF-HFP protective layer (the grid shape was square, the side length was 0.4 mm, and the spacing between each two adjacent grids was 0.1 mm) was sprayed on the surface of the metal copper layer. The metal copper was then etched in a 0.1 mol / L nitric acid solution. After etching, the residual acid was removed by washing with deionized water, and the PVDF-HFP protective layer was removed by washing with NMP to obtain a plurality of discontinuous grid distributions (the distribution form is referenced). Figure 3 ) of a metallic copper unit;

[0151] 3) A 2 μm thick non-metallic conductive layer was coated on the surface of the copper layer by gravure roller coating. The coating slurry formula was: 0.5 wt% carbon nanotubes + 0.5 wt% CMC + 99 wt% deionized water. The final current collector was denoted as F11.

[0152] Comparative Example 4

[0153] The preparation method of the current collector of this comparative example comprises the following steps:

[0154] 1) A biaxially oriented polypropylene film (BOPP) with a thickness of 4 μm was selected as the insulating layer;

[0155] 2) A metal copper layer is deposited on both surfaces of the BOPP film by sputtering, with a thickness of 0.5 μm. Then, a continuously distributed square mesh protective layer (the material of the protective layer is an etching protective glue) is sprayed on the surface of the metal copper layer (the side length of the grid hole in the unsprayed area is 0.4 mm, and the distance between each two adjacent grid holes is 0.1 mm). The metal copper layer is then immersed in a 0.1 mol / L nitric acid solution to etch it. After washing with deionized water to remove the residual acid solution, the etching protective glue is removed with NMP to obtain a grid-like continuous distribution (distribution form reference Figure 8 ) of a metallic copper layer;

[0156] 3) A 2 μm thick non-metallic conductive layer was coated on the surface of the aluminum layer by gravure roller coating, wherein the coating slurry formula was: 0.5 wt% carbon nanotubes + 0.5 wt% CMC + 99 wt% deionized water, and the final current collector was recorded as F12.

[0157] Comparative Example 5

[0158] The preparation method of the current collector of this comparative example comprises the following steps:

[0159] 1) A biaxially oriented polypropylene film (BOPP) with a thickness of 4 μm was selected as the insulating layer;

[0160] 2) A metal copper layer was deposited on both surfaces of the BOPP film by sputtering. The thickness of the copper layer was 0.5 μm. The final current collector was designated as F13.

[0161] Comparative Example 6

[0162] The preparation method of the current collector of this comparative example comprises the following steps:

[0163] 1) A biaxially oriented polypropylene film (BOPP) with a thickness of 4 μm was selected as the insulating layer;

[0164] 2) Depositing a metallic copper layer on both surfaces of the BOPP film by sputtering, with a copper layer deposition thickness of 1 μm;

[0165] 3) A 2 μm thick non-metallic conductive layer was coated on the surface of the aluminum layer by gravure roller coating, wherein the coating slurry formula was: 0.5 wt% carbon nanotubes + 0.5 wt% CMC + 99 wt% deionized water. The final current collector was recorded as F14.

[0166] 2. Preparation of positive electrode

[0167] Weigh 970 g, 15 g, and 15 g of the positive electrode active material lithium cobalt oxide, acetylene black conductive agent, and binder polyvinylidene fluoride (PVDF) respectively, disperse them in 400 g of N-methylpyrrolidone (NMP), and stir them thoroughly to form a uniform positive electrode slurry. The positive electrode slurry is coated on the positive electrode current collectors Z1 to Z14, and then dried, rolled, and cut to obtain positive electrode sheets P1 to P14.

[0168] 3. Preparation of negative electrode sheet

[0169] 970 g, 10 g, 10 g, and 10 g of graphite (a negative electrode active material), carbon black (a conductive agent), styrene-butadiene rubber (SBR) (a binder), and sodium carboxymethyl cellulose (CMC) (a thickener) were respectively weighed and dispersed in 1100 g of deionized water. The mixture was stirred thoroughly to form a uniform negative electrode slurry. The negative electrode slurry was then coated on negative electrode current collectors F1 to F14. The negative electrode sheets N1 to N14 were then obtained by drying, rolling, and cutting.

[0170] 4. Preparation of lithium-ion batteries

[0171] The positive electrode sheet, a wet-process PE separator with an alumina coating (the substrate thickness is 9 μm, the alumina coating thickness is 2 μm), and the negative electrode sheet are welded to the positive and negative electrode tabs and then wound to obtain a battery cell. The battery cell is placed in an aluminum-plastic film packaging shell and sealed, and then the electrolyte is injected. After aging, formation, and sorting, a lithium-ion battery is obtained;

[0172] Among them, the electrolyte includes solvent, lithium salt and additives, the solvent is a mixed solvent with a volume ratio of EC:EMC of 3:7, the lithium salt is LiPF6, the concentration of lithium salt in the electrolyte is 1.2 mol / L, and the additives include VC, FEC and HTCN. The mass content of VC in the electrolyte is 2%, the mass content of FEC in the electrolyte is 4%, and the mass content of HTCN in the electrolyte is 2%.

[0173] Specifically, in the above preparation process, the positive electrode sheet P1 is matched with the negative electrode sheet N1, the positive electrode sheet P2 is matched with the negative electrode sheet N2, the positive electrode sheet P3 is matched with the negative electrode sheet N3, the positive electrode sheet P4 is matched with the negative electrode sheet N4, the positive electrode sheet P5 is matched with the negative electrode sheet N5, the positive electrode sheet P6 is matched with the negative electrode sheet N6, the positive electrode sheet P7 is matched with the negative electrode sheet N7, the positive electrode sheet P8 is matched with the negative electrode sheet N8, the positive electrode sheet P9 is matched with the negative electrode sheet N9, the positive electrode sheet P10 is matched with the negative electrode sheet N10, the positive electrode sheet P11 is matched with the negative electrode sheet N11, the positive electrode sheet P12 is matched with the negative electrode sheet N12, the positive electrode sheet P13 is matched with the negative electrode sheet N13, and the positive electrode sheet P14 is matched with the negative electrode sheet N14. The obtained lithium-ion batteries are recorded as D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, and D14 respectively.

[0174] 5. Current collector and lithium-ion battery performance test

[0175] 1) Current Collector Surface Sheet Resistance Test: A four-probe tester was used in the test environment: room temperature 23±2°C, 0.1MPa, relative humidity ≤65%. The sample to be tested was cleaned and placed horizontally on the test bench. The four-probe tester was lowered to ensure good contact with the conductive layer on the current collector surface. The automatic test mode was then adjusted to calibrate the sample's current range. Sheet resistance was measured at the appropriate current range. Eight to ten data points were collected from the same sample for accuracy and error analysis. The average value was recorded as the current collector surface sheet resistance. The test results are shown in Table 1.

[0176] 2) Testing the percentage of the total area of ​​the metal conductive units in the metal conductive layer of the current collector relative to the area of ​​the insulating layer: The current collector surface was photographed using an optical microscope equipped with imaging capabilities. The images showed a significant difference between the metal conductive and insulating regions. Matlab software was then used to calculate the total area of ​​the metal conductive regions in the images. The percentage of the total area of ​​the metal conductive units relative to the area of ​​the insulating layer was calculated by dividing the total area of ​​the metal conductive regions by the total area of ​​the image. The test results are shown in Table 1.

[0177] 3) Lithium-ion battery safety performance test

[0178] At 25°C, charge the lithium-ion battery at a constant current rate of 0.2C to the upper limit voltage (4.48V), and then charge at a constant voltage until the current is less than or equal to 0.05C. Then, pierce the battery with a steel needle with a diameter of 5±0.5mm at a speed of 25±5mm / s from the direction perpendicular to the battery plate. The puncture position should be close to the geometric center of the punctured surface (the steel needle stays in the battery cell). Keep the steel needle in the lithium-ion battery, monitor the changes in temperature and voltage of the lithium-ion battery, and observe whether the battery has smoke or fire.

[0179] Battery temperature test: Use a multi-channel thermometer to attach thermocouples at the geometric center of the puncture surface and back of the battery to be nailed. After the nailing is completed, perform a five-minute battery temperature tracking test and then record the battery temperature at five minutes to obtain the battery temperature rise.

[0180] Battery voltage test: Connect the positive and negative poles of the battery to be pierced to the voltage measuring instrument. After the piercing is completed, perform a five-minute battery voltage tracking test and then record the battery voltage at five minutes.

[0181] The test results are shown in Table 2.

[0182] Table 1

[0183]

[0184]

[0185] It can be seen from Table 1 that, whether used as a positive current collector or a negative current collector, the current collector having the structure of an insulating layer-discontinuously distributed metal conductive layer-non-metallic conductive layer of the present invention has the largest surface square resistance (positive current collector reference Z1 to Z11, negative current collector reference F1 to F11), followed by the current collector having an insulating layer-continuous network distributed metal conductive layer-non-metallic conductive layer structure (positive current collector reference Z12, negative current collector reference F12), then the current collector having an insulating layer-metal conductive layer (the metal conductive layer fully covers the insulating layer)-non-metallic conductive layer structure (positive current collector reference Z14, negative current collector reference F14), and finally the current collector having an insulating layer-metal to conductive layer structure (positive current collector reference Z13, negative current collector reference F13). This proves that the current collector surface of the present invention has a higher square resistance, which is beneficial for the battery to obtain higher safety performance.

[0186] Table 2

[0187]

[0188]

[0189] As shown in Table 2, lithium-ion batteries (D1-D11) containing the current collectors of the present invention exhibited significantly lower temperature rises during the needle penetration test compared to lithium-ion batteries D12-D14, with no smoke or fire observed. This significantly improved safety performance. It is worth noting that the inclusion of inorganic powders in the non-metallic conductive layers of the positive and negative current collectors used in batteries D6, D7, and D8 lowered the temperature rise during the needle penetration test, resulting in improved safety compared to other batteries.

[0190] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A current collector, characterized in that: It comprises an insulating layer, a metal conductive layer and a non-metallic conductive layer; the metal conductive layer is arranged on at least one functional surface of the insulating layer, and the non-metallic conductive layer is arranged on a functional surface of the metal conductive layer away from the insulating layer; The metal conductive layer includes a plurality of metal conductive units, and the plurality of metal conductive units are distributed at intervals on the insulating layer; The non-metallic conductive layer includes inorganic powder, the average particle size D50 of the inorganic powder is 5-1000 nm, and / or the D99 particle size of the inorganic powder is 5-1000 nm.

2. The current collector according to claim 1, characterized in that The total area of ​​the plurality of metal conductive units accounts for 50% to 98% of the area of ​​the insulating layer.

3. The current collector according to claim 1 or 2, characterized in that: The distance between every two adjacent metal conductive units is d, and 0.001 mm < d < 0.5 mm.

4. The current collector according to claim 1 or 2, characterized in that: The thickness of the insulating layer is 1-20 μm; And / or, the thickness of the metal conductive layer is 50 nm to 3 μm; And / or, the thickness of the non-metallic conductive layer is 1-5 μm.

5. The current collector according to claim 1 or 2, characterized in that: The material of the insulating layer is selected from organic polymers, or a mixture of organic polymers and inorganic fillers; The average particle size D50 of the inorganic filler is 5 to 1000 mm, and / or the particle size D99 of the inorganic filler is 5 to 1000 nm.

6. The current collector according to claim 1 or 2, characterized in that: The material of the metal conductive layer is selected from at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, aluminum-zirconium alloy, and stainless steel.

7. The current collector according to claim 1 or 2, characterized in that: The non-metallic conductive layer includes a carbon-based conductive agent and a binder; the mass fraction of the inorganic powder in the non-metallic conductive layer is 0.1% to 40%.

8. The current collector according to claim 1 or 2, characterized in that: The surface resistance of the current collector is ≥5Ω / □.

9. An electrode sheet, characterized in that: The current collector comprises the current collector according to any one of claims 1 to 8.

10. An electrochemical device, characterized in that The present invention comprises the current collector according to any one of claims 1 to 8 or the electrode sheet according to claim 9.

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