Membrane-free multi-layer current collector and application thereof in solid-state lithium ion battery

Abstract

The invention discloses a diaphragm-free multi-layer current collector and application thereof in a solid-state lithium ion battery, and relates to the technical field of lithium ion battery materials, and the diaphragm-free multi-layer current collector is prepared by the following steps: performing plasma etching on a polyethylene glycol terephthalate layer, and evaporating aluminum plating layers on two sides to obtain a diaphragm-free multi-layer current collector; coating and rolling LFP bottom coating slurry, solid electrolyte layer slurry, positive electrode active material layer slurry and positive electrode ceramic insulating layer slurry on the surface of the aluminum plating layer in sequence to obtain a positive electrode multi-layer current collector; plasma etching is carried out on the polyethylene terephthalate layer, magnetron sputtering and water adding are carried out on the two sides to electroplate a copper plating layer, the surface of the copper plating layer is sequentially coated and rolled with a lithium supplementing layer, negative electrode active material layer slurry and negative electrode ceramic insulation layer slurry, and a negative electrode multi-layer current collector is obtained; and sequentially carrying out cutting, lamination winding, packaging, 2-3g / Ah liquid electrolyte injection, formation and aging on the positive electrode multi-layer current collector and the negative electrode multi-layer current collector to obtain the solid-state lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery materials, in particular to a diaphragm-free multilayer current collector and its application in solid-state lithium ion batteries. BACKGROUND

[0002] Lithium ion batteries are the core carriers of new energy storage technologies, with advantages such as high energy density, long cycle life, environmental protection, and portability, and are widely used in new energy vehicles, energy storage systems, and other fields. However, the existing technology has the following core pain points, which restrict its further development: Firstly, traditional lithium batteries use aluminum foil and copper foil current collectors for positive and negative electrodes respectively, resulting in a heavy battery; although composite current collectors can be used to reduce weight, the interface compatibility of composite current collectors with electrolyte and active materials is poor, which easily leads to high impedance or interface peeling.

[0003] Secondly, the liquid electrolyte of existing lithium batteries accounts for 20%-30% of the battery volume, and the use of liquid electrolyte is high, flammable, and prone to liquid leakage, which increases the risk of battery thermal runaway; at the same time, the interface side reaction increases the consumption of electrolyte, and excessive liquid injection further aggravates the safety hazard. Thirdly, there is lithium loss in the first cycle of the battery negative electrode, and existing lithium supplement technologies mostly use active material mixed lithium supplement agent or prepare a separate lithium supplement layer, but there are still problems such as low utilization rate of lithium supplement agent, easy reaction with current collector, and damage to interface stability. Finally, the positive and negative electrodes are mostly isolated by a diaphragm structure, but the diaphragm not only increases the weight of the battery, but also needs to be coated with a ceramic layer for protection, and it is difficult to accurately protect against the differentiated failure risks of positive and negative electrodes, in addition, the interface reaction between the diaphragm and the electrolyte and the electrode will further consume the electrolyte. Therefore, it is of great significance to develop a new type of solid-state lithium ion battery that can balance safety, energy density, and cost. SUMMARY

[0004] The purpose of the present application is to provide a diaphragm-free multilayer current collector and its application in solid-state lithium ion batteries to solve the problems in the prior art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions: A diaphragm-free multilayer current collector, comprising a positive multilayer current collector and a negative multilayer current collector; the structure of the positive multilayer current collector is sequentially from bottom to top: positive composite current collector, LFP bottom coating layer, solid-state electrolyte layer, positive active material layer, and positive ceramic insulation layer; the structure of the negative multilayer current collector is sequentially from bottom to top: negative composite current collector, lithium supplement layer, negative active material layer, and negative ceramic insulation layer.

[0006] Furthermore, the preparation method of the positive electrode multilayer current collector is as follows: the polyethylene terephthalate (PET) layer is plasma etched, aluminum coating is deposited on both sides, and LFP undercoating slurry, solid electrolyte layer slurry, positive electrode active material layer slurry and positive electrode ceramic insulating layer slurry are sequentially coated and rolled on the surface of the aluminum coating to obtain the positive electrode multilayer current collector. The preparation method of the negative electrode multilayer current collector is as follows: the polyethylene terephthalate (PET) layer is plasma etched, and copper plating is applied by magnetron sputtering on both sides. The lithium replenishment layer slurry, the negative electrode active material layer slurry, and the negative electrode ceramic insulating layer slurry are sequentially coated and rolled on the surface of the copper plating layer to obtain the negative electrode multilayer current collector.

[0007] Furthermore, the LFP undercoating slurry is prepared as follows: lithium iron phosphate, polyacrylonitrile and conductive carbon black are added to deionized water and mixed to make the solid content 50-60% to obtain the LFP undercoating slurry; In the preparation of LFP undercoat slurry, by mass fraction, it contains 90%-92% lithium iron phosphate, 3%-5% polyacrylonitrile and 3%-5% conductive carbon black.

[0008] Further, the solid electrolyte layer slurry is prepared as follows: garnet-type lithium lanthanum zirconium oxide, polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide are added to N-methylpyrrolidone and mixed to make the solid content 50-60% to obtain the solid electrolyte layer slurry; In the preparation of the solid electrolyte layer slurry, the mass ratio of garnet-type lithium lanthanum zirconium oxide, polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide is (55-65):(25-35):(8-12).

[0009] Furthermore, the preparation method of the positive electrode active material layer slurry is as follows: nickel-cobalt-manganese ternary material, carbon nanotubes and polyvinylidene fluoride are added to N-methylpyrrolidone and mixed to make the solid content 60%-70% to obtain the positive electrode active material layer slurry; In the preparation process of the positive electrode active material layer slurry, by mass fraction, it contains 88%-92% nickel-cobalt-manganese ternary materials, 3%-6% carbon nanotubes, and 3%-6% polyvinylidene fluoride.

[0010] Further, the preparation method of the positive electrode ceramic insulating layer slurry is as follows: S1: Dissolve aluminum chloride in an ethanol aqueous solution, then add a mixture of oleic acid and oleylamine, stir and mix well, heat at 150-170℃ for 6-8 hours, cool to room temperature, disperse and precipitate with cyclohexane and ethanol, centrifuge and wash, crush and sieve to obtain alumina nanowires; S2: Add alumina nanowires and polyacrylic acid to deionized water and mix to make the solid content 40%-50% to obtain positive electrode ceramic insulating layer slurry; In the preparation of the positive electrode ceramic insulating layer slurry, the mass ratio of aluminum chloride, oleic acid and oleylamine is 1:(1-3):(4-6); by mass fraction, it contains 85%-92% alumina nanowires and 8%-15% polyacrylic acid.

[0011] Further, the preparation method of the lithium replenishment slurry is as follows: S1: 3-mercapto-1,2,4-triazole is placed in anhydrous toluene solution, lithium metal powder is added under argon protection, the reaction is carried out at room temperature for 2-4 hours, filtered, washed with anhydrous toluene, and then evenly placed on a reaction vessel, and subjected to acetylene chemical vapor precipitation at 80-120℃ for 30-60 minutes to obtain carbon-coated lithium metal powder; S2: Under an argon atmosphere, carbon-coated lithium metal powder and styrene-butadiene rubber are added to deionized water and mixed to make the solid content 40%-50% to obtain a lithium replenishment slurry. In the preparation of the lithium replenishment slurry, the mass ratio of 3-mercapto-1,2,4-triazole to lithium metal powder is (10-20):1; by mass fraction, it contains 85%-92% carbon-coated lithium metal powder and 8%-15% styrene-butadiene rubber.

[0012] Furthermore, the preparation method of the negative electrode active material is as follows: artificial graphite or carbon silicon composite material, styrene-butadiene rubber and sodium carboxymethyl cellulose are added to deionized water and mixed to make the solid content 50%-60% to obtain a negative electrode active material slurry; In the preparation of negative electrode active material slurry, by mass fraction, it consists of 90%-95% artificial graphite or carbon silicon composite material, 1%-5% styrene-butadiene rubber and 1%-5% sodium carboxymethyl cellulose.

[0013] Furthermore, the preparation method of the negative electrode ceramic insulator is as follows: alumina nanowires, garnet-type lithium lanthanum zirconium oxide and polyurethane are added to deionized water and mixed to make the solid content 40%-50% to obtain a negative electrode ceramic insulation layer slurry. In the preparation of the negative electrode ceramic insulating layer slurry, by mass fraction, it consists of 76%-85% alumina nanowires, 7%-9% garnet-type lithium lanthanum zirconium oxide, and 8%-15% polyurethane.

[0014] The application of a membrane-free multilayer current collector in a solid-state lithium-ion battery includes the following steps: S1: Ethylene carbonate and ethyl methyl carbonate are mixed evenly, then lithium hexafluorophosphate and lithium difluorophosphate are added, and the mixture is stirred and mixed to obtain a liquid electrolyte. S2: The positive electrode multilayer current collector and the negative electrode multilayer current collector are sequentially cut, stacked and wound, packaged, injected with 2-3g / Ah liquid electrolyte, formed and aged to obtain a solid-state lithium-ion battery; In the preparation process of solid-state lithium-ion batteries, the mass ratio of ethylene carbonate, ethyl methyl carbonate, lithium hexafluorophosphate and lithium difluorophosphate is (10-13):(10-20):(3-5):(1-1.5).

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. The lithium battery positive electrode of this invention adopts a multilayer current collector with a "five-layer progressive composite structure". First, a composite aluminum current collector serves as the supporting base, balancing the lightweight nature of the electrode and structural strength. A polymer layer is plasma-etched to improve the adhesion between the composite current collector and the LFP undercoat. Second, an LFP undercoat is formed from lithium iron phosphate, a binder, and a conductive agent, creating a transition between the composite aluminum current collector and the solid electrolyte. This improves interfacial compatibility, ensures interface adhesion, and reduces impedance. Third, the solid electrolyte layer uses garnet-type lithium lanthanum zirconium oxide to provide a high ion conduction channel, polyethylene oxide to provide flexibility, and lithium bis(trifluoromethanesulfonyl)imide to enhance ion dissociation, thereby replacing more than 70% of the liquid electrolyte and reducing the risk of battery flammability and material costs. Fourth, the positive electrode active material layer is composed of nickel-cobalt-manganese ternary materials, carbon nanotubes, polyvinylidene fluoride, and N-methylpyrrolidone, improving electron conduction uniformity and promoting the bonding between the active material and the solid electrolyte layer, thus enhancing structural stability and ensuring capacity output. Fifth, the ceramic insulating layer uses alumina nanowires as the main insulator. Its three-dimensional framework structure not only improves the strength and toughness of the coating but also enhances the interfacial adhesion between the coating and the electrode, effectively inhibiting the dissolution of transition metals in the active material, blocking micro-short circuit paths, and increasing the thermal runaway threshold. In summary, the multilayer current collector for positive electrodes prepared in this invention can effectively solve the pain points of traditional positive electrode sheets, such as poor compatibility, high electrolyte dependence, and insufficient safety protection.

[0016] 2. The lithium battery negative electrode sheet of this invention adopts a multilayer current collector with a "four-layer functional guiding structure". First, plasma etching of the polymer layer improves surface roughness and promotes the bonding between the substrate and the lithium replenishment layer. At the same time, the thinning of the copper plating layer can effectively suppress the "piercing driving force" during lithium dendrite growth, reducing the risk of short circuit. Second, the lithium replenishment layer is initially coated with 3-mercapto-1,2,4-triazole to coat the lithium metal powder, and then carbon-coated lithium metal powder formed by acetylene chemical vapor deposition is used as the lithium replenishing agent. This avoids the oxidation of the lithium replenishing agent and accurately replenishes the lithium consumption of the active material in the first cycle. At the same time, styrene-butadiene rubber is used as a binder to give the coating elasticity, ensuring both lithium replenishment efficiency and maintaining interface stability. Third, the negative electrode active material layer uses artificial graphite or carbon-silicon composite material as the active ingredient, and styrene-butadiene rubber and sodium carboxymethyl cellulose as binders to promote uniform dispersion of artificial graphite and improve coating toughness. Fourth, the negative electrode ceramic insulating layer uses alumina nanowires and garnet-type lithium lanthanum zirconium oxide as active ingredients, which effectively inhibits lithium dendrite puncture while ensuring ion conduction channels and avoiding excessive impedance. High-elasticity polyurethane is used as a binder to effectively prevent coating cracking. This negative electrode ceramic insulating layer effectively inhibits the growth rate of lithium dendrites, avoids excessive reaction between the active ingredients and the electrolyte, and reduces electrolyte consumption. In summary, the multilayer current collector for negative electrodes prepared in this invention effectively solves the problems of high initial lithium loss, high risk of lithium dendrite puncture, and high current collector weight ratio in traditional negative electrode sheets.

[0017] 3. The lithium-ion battery prepared by this invention reduces the dissolution of transition metals in the positive electrode by more than 50%, reduces the lithium dendrite growth rate in the negative electrode by more than 80%, and lowers the thermal runaway temperature to above 300℃, significantly improving battery safety. The utilization rate of the lithium replenishment layer reaches over 90%, the initial efficiency of the battery exceeds 95%, and electrochemical performance is improved. Simultaneously, the lithium-ion battery uses a ceramic insulating coating instead of a separator structure, reducing interfacial reactions between the separator and the electrolyte / electrode, and lowering interfacial impedance. Furthermore, all coatings are applied using existing blade coating equipment, eliminating the need for additional separator-related production processes, facilitating mass production conversion. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a solid-state lithium-ion battery composed of a membraneless multilayer current collector according to the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the following examples, the CAS number for lithium iron phosphate is 15365-14-7; the CAS number for polyacrylonitrile is 25014-41-9; the CAS number for polyethylene oxide is 68441-17-8; the CAS number for lithium bis(trifluoromethanesulfonyl)imide is 90076-65-6; the CAS number for N-methylpyrrolidone is 872-50-4; the CAS number for polyvinylidene fluoride is 24937-79-9; the CAS number for oleic acid is 112-80-1; the CAS number for oleylamine is 112-90-3; and the CAS number for polyacrylic acid is 9003-01- 4; CAS number for 3-mercapto-1,2,4-triazole is 3179-31-5; CAS number for styrene-butadiene rubber is 9003-55-8; CAS number for sodium carboxymethyl cellulose is 9004-32-4; ​​CAS number for polyurethane is 51852-81-4; CAS number for ethylene carbonate is 96-49-1; CAS number for ethyl methyl carbonate is 623-53-0; CAS number for lithium hexafluorophosphate is 21324-40-3; CAS number for lithium difluorophosphate is 24389-25-1; the model number for nickel-cobalt-manganese ternary materials is NCM811.

[0021] Example 1: A membraneless multilayer current collector and its application in solid-state lithium-ion batteries: Step 1: Preparation of the positive electrode multilayer current collector: S11: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and aluminum coating is deposited on both sides to obtain the positive electrode composite current collector. S12: Add 90g of lithium iron phosphate, 5g of polyacrylonitrile and 5g of conductive carbon black to deionized water, mix to form an LFP undercoating slurry with a solid content of 55%, coat it on the surface of the positive electrode composite current collector, and dry it at 120-150℃ to obtain the LFP undercoating. S13: Add 55g of garnet-type lithium lanthanum zirconium oxide, 35g of polyethylene oxide, 10g of lithium bis(trifluoromethanesulfonyl)imide and 0.5g of zinc oxide powder to N-methylpyrrolidone, mix to form a solid electrolyte layer slurry with a solid content of 60%, coat it on the surface of the LFP undercoating layer, and dry it at 230℃ to obtain the solid electrolyte layer. S14: Add 90g of nickel-cobalt-manganese ternary material, 5g of carbon nanotubes and 5g of polyvinylidene fluoride to N-methylpyrrolidone, mix well to form a positive electrode active material layer slurry with a solid content of 68%, coat it on the surface of the solid electrolyte layer, dry it at 150℃ and roll it at 10MPa to obtain the positive electrode active material layer. S15: Add 55g of garnet-type lithium lanthanum zirconium oxide, 35g of polyethylene oxide, 10g of lithium bis(trifluoromethanesulfonyl)imide, 0.5g of zinc oxide powder and 0.3g of aluminum oxide to N-methylpyrrolidone, mix to form a solid electrolyte sheet slurry with a solid content of 60%, coat it on the positive electrode active material layer, and dry it at 220℃ to obtain a solid electrolyte sheet; S16: Add 1g of aluminum chloride to a mixture of 1ml of oleic acid and 4ml of oleylamine, stir for 20min, react at 150℃ for 6h, cool to room temperature, disperse and precipitate with cyclohexane and ethanol, centrifuge and wash, crush and sieve to obtain alumina nanowires. S17: Add 90g of alumina nanowires and 10g of polyacrylic acid to deionized water, mix to form a positive electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of a solid electrolyte sheet, and dry it at 160℃ to obtain a positive electrode multilayer current collector. Step 2: Preparation of the negative electrode multilayer current collector: S21: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and copper plating is added by magnetron sputtering on both sides to obtain the negative electrode composite current collector. S22: Place 10 ml of 3-mercapto-1,2,4-triazole in anhydrous toluene solution, add 1 g of lithium metal powder under argon protection, react at room temperature for 2 h, filter, wash with anhydrous toluene, and then uniformly place on a reaction vessel under argon protection for acetylene chemical vapor precipitation at 80 °C for 30 min to obtain carbon-coated lithium metal powder. S23: Under an argon atmosphere, 90g of carbon-coated lithium metal powder and 10g of styrene-butadiene rubber are added to deionized water and mixed to form a lithium replenishment slurry with a solid content of 50%. The slurry is coated onto the surface of the negative electrode composite current collector and dried at 70°C to make the lithium replenishment amount 7% of the theoretical capacity of the battery, thus obtaining the lithium replenishment layer. S24: Add 92g of silicon-carbon composite material, 3g of conductive graphite, 2g of carbon nanotubes, 2g of styrene-butadiene rubber and 1g of sodium carboxymethyl cellulose to deionized water, mix to form a negative electrode active material slurry with a solid content of 50%, coat it onto the surface of the lithium replenishment layer, dry it at 140℃, and roll it at 3MPa to obtain the negative electrode active material layer. S25: Add 85g of alumina nanowires, 5g of garnet-type lithium lanthanum zirconium oxide and 10g of polyurethane to deionized water, mix to form a negative electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of the negative electrode active material layer, and dry it at 160℃ to obtain a negative electrode multilayer current collector. Step 3: Assemble the battery: S31: Mix 10ml ethylene carbonate and 20ml methyl ethyl carbonate evenly, add 4g lithium hexafluorophosphate and 1g lithium difluorophosphate, stir and mix well to obtain liquid electrolyte. S32: The positive electrode multilayer current collector and the negative electrode multilayer current collector are assembled using a stacking process. The electrode assembly is then placed into an aluminum-plastic film shell and pre-encapsulated under a vacuum of -0.095MPa. Liquid electrolyte is injected at a rate of 2-3g / Ah, and vacuum-sealed under a pressure of 0.15MPa. The battery is charged to 3.65V at a constant current of 0.1C, allowed to stand for 2 hours for formation, and then aged at 45℃ for 48 hours to obtain a lithium-ion battery.

[0022] Example 2: A membraneless multilayer current collector and its application in solid-state lithium-ion batteries: Step 1: Preparation of the positive electrode multilayer current collector: S11: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and aluminum coating is deposited on both sides to obtain the positive electrode composite current collector. S12: Add 90g of lithium iron phosphate, 5g of polyacrylonitrile and 5g of conductive carbon black to deionized water, mix to form an LFP undercoating slurry with a solid content of 55%, coat it on the surface of the positive electrode composite current collector, and dry it at 120-150℃ to obtain the LFP undercoating. S13: Add 55g of garnet-type lithium lanthanum zirconium oxide, 35g of polyethylene oxide, 10g of lithium bis(trifluoromethanesulfonyl)imide and 0.5g of zinc oxide powder to N-methylpyrrolidone, mix to form a solid electrolyte layer slurry with a solid content of 60%, coat it on the surface of the LFP undercoating layer, and dry it at 230℃ to obtain the solid electrolyte layer. S14: Add 90g of nickel-cobalt-manganese ternary material, 5g of carbon nanotubes and 5g of polyvinylidene fluoride to N-methylpyrrolidone, mix well to form a positive electrode active material layer slurry with a solid content of 68%, coat it on the surface of the solid electrolyte layer, dry it at 150℃ and roll it at 10MPa to obtain the positive electrode active material layer. S15: Add 55g of garnet-type lithium lanthanum zirconium oxide, 35g of polyethylene oxide, 10g of lithium bis(trifluoromethanesulfonyl)imide, 0.5g of zinc oxide powder and 0.3g of aluminum oxide to N-methylpyrrolidone, mix to form a solid electrolyte sheet slurry with a solid content of 60%, coat it on the positive electrode active material layer, and dry it at 220℃ to obtain a solid electrolyte sheet; S16: Add 1g of aluminum chloride to a mixture of 2ml of oleic acid and 5ml of oleylamine, stir for 20min, react at 160℃ for 7h, cool to room temperature, disperse and precipitate with cyclohexane and ethanol, centrifuge and wash, crush and sieve to obtain alumina nanowires. S17: Add 90g of alumina nanowires and 10g of polyacrylic acid to deionized water, mix to form a positive electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of a solid electrolyte sheet, and dry it at 160℃ to obtain a positive electrode multilayer current collector. Step 2: Preparation of the negative electrode multilayer current collector: S21: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and copper plating is added by magnetron sputtering on both sides to obtain the negative electrode composite current collector. S22: Place 15 ml of 3-mercapto-1,2,4-triazole in anhydrous toluene solution, add 1 g of lithium metal powder under argon protection, react at room temperature for 3 h, filter, wash with anhydrous toluene, and then uniformly place on a reaction vessel under argon protection for acetylene chemical vapor precipitation at 100 °C for 45 min to obtain carbon-coated lithium metal powder. S23: Under an argon atmosphere, 90g of carbon-coated lithium metal powder and 10g of styrene-butadiene rubber are added to deionized water and mixed to form a lithium replenishment slurry with a solid content of 50%. The slurry is coated onto the surface of the negative electrode composite current collector and dried at 70°C to make the lithium replenishment amount 7% of the theoretical capacity of the battery, thus obtaining the lithium replenishment layer. S24: Add 92g of silicon-carbon composite material, 3g of conductive graphite, 2g of carbon nanotubes, 2g of styrene-butadiene rubber and 1g of sodium carboxymethyl cellulose to deionized water, mix to form a negative electrode active material slurry with a solid content of 50%, coat it onto the surface of the lithium replenishment layer, dry it at 140℃, and roll it at 3MPa to obtain the negative electrode active material layer. S25: Add 85g of alumina nanowires, 5g of garnet-type lithium lanthanum zirconium oxide and 10g of polyurethane to deionized water, mix to form a negative electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of the negative electrode active material layer, and dry it at 160℃ to obtain a negative electrode multilayer current collector. Step 3: Assemble the battery: S31: Mix 10ml ethylene carbonate and 20ml methyl ethyl carbonate evenly, add 4g lithium hexafluorophosphate and 1g lithium difluorophosphate, stir and mix well to obtain liquid electrolyte. S32: The positive electrode multilayer current collector and the negative electrode multilayer current collector are assembled using a stacking process. The electrode assembly is then placed into an aluminum-plastic film shell and pre-encapsulated under a vacuum of -0.095MPa. Liquid electrolyte is injected at a rate of 2-3g / Ah, and vacuum-sealed under a pressure of 0.15MPa. The battery is charged to 3.65V at a constant current of 0.1C, allowed to stand for 2 hours for formation, and then aged at 45℃ for 48 hours to obtain a lithium-ion battery.

[0023] Example 3: A membraneless multilayer current collector and its application in solid-state lithium-ion batteries: Step 1: Preparation of the positive electrode multilayer current collector: S11: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and aluminum coating is deposited on both sides to obtain the positive electrode composite current collector. S12: Add 90g of lithium iron phosphate, 5g of polyacrylonitrile and 5g of conductive carbon black to deionized water, mix to form an LFP undercoating slurry with a solid content of 55%, coat it on the surface of the positive electrode composite current collector, and dry it at 120-150℃ to obtain the LFP undercoating. S13: Add 55g of garnet-type lithium lanthanum zirconium oxide, 35g of polyethylene oxide, 10g of lithium bis(trifluoromethanesulfonyl)imide and 0.5g of zinc oxide powder to N-methylpyrrolidone, mix to form a solid electrolyte layer slurry with a solid content of 60%, coat it on the surface of the LFP undercoating layer, and dry it at 230℃ to obtain the solid electrolyte layer. S14: Add 90g of nickel-cobalt-manganese ternary material, 5g of carbon nanotubes and 5g of polyvinylidene fluoride to N-methylpyrrolidone, mix well to form a positive electrode active material layer slurry with a solid content of 68%, coat it on the surface of the solid electrolyte layer, dry it at 150℃ and roll it at 10MPa to obtain the positive electrode active material layer. S15: Add 55g of garnet-type lithium lanthanum zirconium oxide, 35g of polyethylene oxide, 10g of lithium bis(trifluoromethanesulfonyl)imide, 0.5g of zinc oxide powder and 0.3g of aluminum oxide to N-methylpyrrolidone, mix to form a solid electrolyte sheet slurry with a solid content of 60%, coat it on the positive electrode active material layer, and dry it at 220℃ to obtain a solid electrolyte sheet; S16: Add 1g of aluminum chloride to a mixture of 3ml of oleic acid and 6ml of oleylamine, stir for 20min, react at 170℃ for 8h, cool to room temperature, disperse and precipitate with cyclohexane and ethanol, centrifuge and wash, crush and sieve to obtain alumina nanowires. S17: Add 90g of alumina nanowires and 10g of polyacrylic acid to deionized water, mix to form a positive electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of a solid electrolyte sheet, and dry it at 160℃ to obtain a positive electrode multilayer current collector. Step 2: Preparation of the negative electrode multilayer current collector: S21: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and copper plating is added by magnetron sputtering on both sides to obtain the negative electrode composite current collector. S22: Place 20 ml of 3-mercapto-1,2,4-triazole in anhydrous toluene solution, add 1 g of lithium metal powder under argon protection, react at room temperature for 4 h, filter, wash with anhydrous toluene, and then uniformly place on a reaction vessel under argon protection for acetylene chemical vapor precipitation at 120 °C for 60 min to obtain carbon-coated lithium metal powder. S23: Under an argon atmosphere, 90g of carbon-coated lithium metal powder and 10g of styrene-butadiene rubber are added to deionized water and mixed to form a lithium replenishment slurry with a solid content of 50%. The slurry is coated onto the surface of the negative electrode composite current collector and dried at 70°C to make the lithium replenishment amount 7% of the theoretical capacity of the battery, thus obtaining the lithium replenishment layer. S24: Add 92g of silicon-carbon composite material, 3g of conductive graphite, 2g of carbon nanotubes, 2g of styrene-butadiene rubber and 1g of sodium carboxymethyl cellulose to deionized water, mix to form a negative electrode active material slurry with a solid content of 50%, coat it onto the surface of the lithium replenishment layer, dry it at 140℃, and roll it at 3MPa to obtain the negative electrode active material layer. S25: Add 85g of alumina nanowires, 5g of garnet-type lithium lanthanum zirconium oxide and 10g of polyurethane to deionized water, mix to form a negative electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of the negative electrode active material layer, and dry it at 160℃ to obtain a negative electrode multilayer current collector. Step 3: Assemble the battery: S31: Mix 10ml ethylene carbonate and 20ml methyl ethyl carbonate evenly, add 4g lithium hexafluorophosphate and 1g lithium difluorophosphate, stir and mix well to obtain liquid electrolyte. S32: The positive electrode multilayer current collector and the negative electrode multilayer current collector are assembled using a stacking process. The electrode assembly is then placed into an aluminum-plastic film shell and pre-encapsulated under a vacuum of -0.095MPa. Liquid electrolyte is injected at a rate of 2-3g / Ah, and vacuum-sealed under a pressure of 0.15MPa. The battery is charged to 3.65V at a constant current of 0.1C, allowed to stand for 2 hours for formation, and then aged at 45℃ for 48 hours to obtain a lithium-ion battery.

[0024] Example 4: A membraneless multilayer current collector and its application in solid-state lithium-ion batteries: Step 1: Preparation of the positive electrode multilayer current collector: S11: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and aluminum coating is deposited on both sides to obtain the positive electrode composite current collector. S12: Add 90g of lithium iron phosphate, 5g of polyacrylonitrile and 5g of conductive carbon black to deionized water, mix to form an LFP undercoating slurry with a solid content of 55%, coat it on the surface of the positive electrode composite current collector, and dry it at 120-150℃ to obtain the LFP undercoating. S13: 62g of garnet-type lithium lanthanum zirconium oxide, 28g of polyethylene oxide, 10g of lithium bis(trifluoromethanesulfonyl)imide and 0.8g of graphene are added to N-methylpyrrolidone and mixed to form a solid electrolyte layer slurry with a solid content of 60%. The slurry is coated on the surface of the LFP undercoating layer and dried at 220℃ to obtain the solid electrolyte layer. S14: Add 90g of nickel-cobalt-manganese ternary material, 5g of carbon nanotubes and 5g of polyvinylidene fluoride to N-methylpyrrolidone, mix well to form a positive electrode active material layer slurry with a solid content of 68%, coat it on the surface of the solid electrolyte layer, dry it at 150℃ and roll it at 10MPa to obtain the positive electrode active material layer. S15: 62.5g of garnet-type lithium lanthanum zirconium oxide, 28g of polyethylene oxide, 10g of lithium bis(trifluoromethanesulfonyl)imide and 0.8g of graphene are added to N-methylpyrrolidone and mixed to form a solid electrolyte sheet slurry with a solid content of 60%. The slurry is coated on the positive electrode active material layer and dried at 220℃ to obtain a solid electrolyte sheet. S16: Add 1g of aluminum chloride to a mixture of 3ml of oleic acid and 6ml of oleylamine, stir for 20min, react at 170℃ for 8h, cool to room temperature, disperse and precipitate with cyclohexane and ethanol, centrifuge and wash, crush and sieve to obtain alumina nanowires. S17: Add 90g of alumina nanowires and 10g of polyacrylic acid to deionized water to form a positive electrode ceramic insulating layer slurry with a solid content of 45%. Coat the slurry onto the surface of a solid electrolyte sheet and dry at 160℃ to obtain a positive electrode multilayer current collector; Step 2: Prepare a negative electrode multilayer current collector: Step 2: Preparation of the negative electrode multilayer current collector: S21: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and copper plating is added by magnetron sputtering on both sides to obtain the negative electrode composite current collector. S22: Place 20 ml of 3-mercapto-1,2,4-triazole in anhydrous toluene solution, add 1 g of lithium metal powder under argon protection, react at room temperature for 4 h, filter, wash with anhydrous toluene, and then uniformly place on a reaction vessel under argon protection for acetylene chemical vapor precipitation at 120 °C for 60 min to obtain carbon-coated lithium metal powder. S23: Under an argon atmosphere, 90g of carbon-coated lithium metal powder and 10g of styrene-butadiene rubber are added to deionized water and mixed to form a lithium replenishment slurry with a solid content of 50%. The slurry is coated onto the surface of the negative electrode composite current collector and dried at 70°C to make the lithium replenishment amount 9% of the theoretical capacity of the battery, thus obtaining the lithium replenishment layer. S24: Add 27.6g of carbon silicon composite material, 64.4g of artificial graphite, 3g of conductive graphite, 2g of carbon nanotubes, 2g of styrene-butadiene rubber and 1g of sodium carboxymethyl cellulose to deionized water, mix to form a negative electrode active material slurry with a solid content of 52%, coat it onto the surface of the lithium replenishment layer, dry it at 140℃, and roll it at 2MPa to obtain the negative electrode active material layer; S25: Add 85g of alumina nanowires, 5g of garnet-type lithium lanthanum zirconium oxide and 10g of polyurethane to deionized water, mix to form a negative electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of the negative electrode active material layer, and dry it at 160℃ to obtain a negative electrode multilayer current collector. Step 3: Assemble the battery: S31: Mix 10ml ethylene carbonate and 20ml methyl ethyl carbonate evenly, add 4g lithium hexafluorophosphate and 1g lithium difluorophosphate, stir and mix well to obtain liquid electrolyte. S32: The positive electrode multilayer current collector and the negative electrode multilayer current collector are assembled using a stacking process. The electrode assembly is then placed into an aluminum-plastic film shell and pre-encapsulated under a vacuum of -0.095MPa. Liquid electrolyte is injected at a rate of 2-3g / Ah, and vacuum-sealed under a pressure of 0.15MPa. The battery is charged to 3.65V at a constant current of 0.1C, allowed to stand for 2 hours for formation, and then aged at 45℃ for 48 hours to obtain a lithium-ion battery.

[0025] Example 5: A membraneless multilayer current collector and its application in solid-state lithium-ion batteries: Step 1: Preparation of the positive electrode multilayer current collector: S11: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and aluminum coating is deposited on both sides to obtain the positive electrode composite current collector. S12: Add 90g of lithium iron phosphate, 5g of polyacrylonitrile and 5g of conductive carbon black to deionized water, mix to form an LFP undercoating slurry with a solid content of 55%, coat it on the surface of the positive electrode composite current collector, and dry it at 120-150℃ to obtain the LFP undercoating. S13: Add 60g of garnet-type lithium lanthanum zirconium oxide, 30g of polyethylene oxide and 10g of lithium bis(trifluoromethanesulfonyl)imide to N-methylpyrrolidone, mix to form a solid electrolyte layer slurry with a solid content of 60%, coat it on the surface of the LFP undercoating layer, and dry it at 220℃ to obtain the solid electrolyte layer. S14: Add 92g of nickel-cobalt-manganese ternary material, 3g of carbon nanotubes and 5g of polyvinylidene fluoride to N-methylpyrrolidone, mix well to form a positive electrode active material layer slurry with a solid content of 65%, coat it on the surface of the solid electrolyte layer, dry it at 140℃ and roll it at 8MPa to obtain the positive electrode active material layer. S15: Add 1g of aluminum chloride to a mixture of 3ml of oleic acid and 6ml of oleylamine, stir for 20min, react at 170℃ for 8h, cool to room temperature, disperse and precipitate with cyclohexane and ethanol, centrifuge and wash, crush and sieve to obtain alumina nanowires. S16: Add 90g of alumina nanowires and 10g of polyacrylic acid to deionized water, mix to form a positive electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of the positive electrode active material layer, and dry it at 160℃ to obtain a positive electrode multilayer current collector. Step 2: Preparation of the negative electrode multilayer current collector: S21: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and copper plating is added by magnetron sputtering on both sides to obtain the negative electrode composite current collector. S22: Place 20 ml of 3-mercapto-1,2,4-triazole in anhydrous toluene solution, add 1 g of lithium metal powder under argon protection, react at room temperature for 4 h, filter, wash with anhydrous toluene, and then uniformly place on a reaction vessel under argon protection for acetylene chemical vapor precipitation at 120 °C for 60 min to obtain carbon-coated lithium metal powder. S23: Under an argon atmosphere, 90g of carbon-coated lithium metal powder and 10g of styrene-butadiene rubber are added to deionized water and mixed to form a lithium replenishment slurry with a solid content of 50%. The slurry is coated onto the surface of the negative electrode composite current collector and dried at 70°C to make the lithium replenishment amount 6% of the theoretical capacity of the battery, thus obtaining the lithium replenishment layer. S24: Add 95g of artificial graphite, 2.5g of styrene-butadiene rubber and 2.5g of sodium carboxymethyl cellulose to deionized water, mix to form a negative electrode active material slurry with a solid content of 55%, coat it onto the surface of the lithium replenishment layer, dry it at 130℃, and roll it at 5MPa to obtain the negative electrode active material layer. S25: Add 85g of alumina nanowires, 5g of garnet-type lithium lanthanum zirconium oxide and 10g of polyurethane to deionized water, mix to form a negative electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of the negative electrode active material layer, and dry it at 160℃ to obtain a negative electrode multilayer current collector. Step 3: Assemble the battery: S31: Mix 10ml ethylene carbonate and 20ml methyl ethyl carbonate evenly, add 4g lithium hexafluorophosphate and 1g lithium difluorophosphate, stir and mix well to obtain liquid electrolyte. S32: The positive electrode multilayer current collector and the negative electrode multilayer current collector are assembled using a stacking process. The electrode assembly is then placed into an aluminum-plastic film shell and pre-encapsulated under a vacuum of -0.095MPa. Liquid electrolyte is injected at a rate of 2-3g / Ah, and vacuum-sealed under a pressure of 0.15MPa. The battery is charged to 3.65V at a constant current of 0.1C, allowed to stand for 2 hours for formation, and then aged at 45℃ for 48 hours to obtain a lithium-ion battery.

[0026] Comparative Example 1: A membraneless multilayer current collector and its application in solid-state lithium-ion batteries: Step 1: Preparation of positive electrode multilayer current collector: Step S15 was not performed; S16: Add 90g of alumina and 10g of polyacrylic acid to deionized water and mix to form a positive electrode ceramic insulating layer slurry with a solid content of 45%. Coat the surface of the positive electrode active material layer and dry at 160℃ to obtain a positive electrode multilayer current collector. Step 2: Preparation of the negative electrode multilayer current collector: S21: At 80W, the polyethylene terephthalate layer is plasma etched for 45s, and copper plating is added by magnetron sputtering on both sides to obtain the negative electrode composite current collector. S22: Under an argon atmosphere, 90g of lithium ferrite and 10g of styrene-butadiene rubber are added to deionized water and mixed to form a lithium replenishment slurry with a solid content of 50%. The slurry is coated onto the surface of the negative electrode composite current collector and dried at 70°C to make the lithium replenishment amount 6% of the theoretical capacity of the battery, thus obtaining the lithium replenishment layer. S23: Add 95g of artificial graphite, 2.5g of styrene-butadiene rubber and 2.5g of sodium carboxymethyl cellulose to deionized water, mix to form a negative electrode active material slurry with a solid content of 55%, coat it onto the surface of the lithium replenishment layer, dry it at 130℃, and roll it at 5MPa to obtain the negative electrode active material layer. S24: Add 85g of alumina, 5g of garnet-type lithium lanthanum zirconium oxide and 10g of polyurethane to deionized water, mix to form a negative electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of the negative electrode active material layer, and dry it at 160℃ to obtain a negative electrode multilayer current collector. The remaining steps are the same as in Example 5.

[0027] Comparative Example 2: A membraneless multilayer current collector and its application in solid-state lithium-ion batteries: S1: 92g of nickel-cobalt-manganese ternary material, 3g of carbon nanotubes and 5g of polyvinylidene fluoride were added to N-methylpyrrolidone and mixed to form a positive electrode active material slurry with a solid content of 65%. The slurry was coated on the surface of a conventional aluminum foil, dried at 140°C and rolled at 8MPa to obtain a positive electrode sheet. S2: Add 95g of artificial graphite, 2.5g of styrene-butadiene rubber and 2.5g of sodium carboxymethyl cellulose to deionized water, mix to form a negative electrode active material slurry with a solid content of 55%, coat it onto the surface of a traditional copper foil, dry it at 130℃, and roll it at 5MPa to obtain a negative electrode sheet. S3: Prepare a polypropylene-polyethylene composite membrane, and spray an alumina ceramic layer on one side to obtain a conventional membrane; S4: Mix 10ml ethylene carbonate and 20ml methyl ethyl carbonate evenly, add 4g lithium hexafluorophosphate and 1g lithium difluorophosphate, stir and mix well to obtain liquid electrolyte; S5: The electrode is assembled in the order of positive electrode - traditional separator - negative electrode using a stacking process. The electrode assembly is then placed into an aluminum-plastic film shell and pre-encapsulated under a vacuum of -0.095MPa. Liquid electrolyte is injected at a rate of 2-3g / Ah, and vacuum-sealed under a pressure of 0.15MPa. The battery is then charged to 3.65V at a constant current of 0.1C, allowed to stand for 2 hours for formation, and then aged at 45℃ for 48 hours to obtain a lithium-ion battery.

[0028] Comparative Example 3: A membraneless multilayer current collector and its application in solid-state lithium-ion batteries: Step 1: Preparation of the positive electrode multilayer current collector: S11: Add 90g of lithium iron phosphate, 5g of polyacrylonitrile and 5g of conductive carbon black to deionized water, mix to form an LFP undercoating slurry with a solid content of 55%, coat it on the surface of a conventional aluminum foil, and dry it at 120-150℃ to obtain an LFP undercoating. S12: Add 60g of garnet-type lithium lanthanum zirconium oxide, 30g of polyethylene oxide and 10g of lithium bis(trifluoromethanesulfonyl)imide to N-methylpyrrolidone, mix to form a solid electrolyte layer slurry with a solid content of 60%, coat it on the surface of the LFP undercoating layer, and dry it at 220℃ to obtain the solid electrolyte layer. S13: 62.5g of garnet-type lithium lanthanum zirconium oxide, 28g of polyethylene oxide, 10g of lithium bis(trifluoromethanesulfonyl)imide and 0.8g of graphene are added to N-methylpyrrolidone and mixed to form a solid electrolyte sheet slurry with a solid content of 60%. The slurry is coated on the solid electrolyte layer and dried at 220℃ to obtain a solid electrolyte sheet. S14: Add 92g of nickel-cobalt-manganese ternary material, 3g of carbon nanotubes and 5g of polyvinylidene fluoride to N-methylpyrrolidone, mix well to form a positive electrode active material layer slurry with a solid content of 65%, coat it on the surface of a solid electrolyte sheet, dry it at 140℃ and roll it at 8MPa to obtain the positive electrode active material layer. S15: Add 1g of aluminum chloride to a mixture of 3ml of oleic acid and 6ml of oleylamine, stir for 20min, react at 170℃ for 8h, cool to room temperature, disperse and precipitate with cyclohexane and ethanol, centrifuge and wash, crush and sieve to obtain alumina nanowires. S16: Add 90g of alumina nanowires and 10g of polyacrylic acid to deionized water, mix to form a positive electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of a solid electrolyte sheet, and dry it at 160℃ to obtain a positive electrode multilayer current collector. Step 2: Preparation of the negative electrode multilayer current collector: S21: Add 95g of artificial graphite, 2.5g of styrene-butadiene rubber and 2.5g of sodium carboxymethyl cellulose to deionized water, mix to form a negative electrode active material slurry with a solid content of 55%, coat it onto the surface of a traditional copper foil, dry it at 130℃, and roll it at 5MPa to obtain a negative electrode active material layer. S22: Add 85g of alumina nanowires, 5g of garnet-type lithium lanthanum zirconium oxide and 10g of polyurethane to deionized water, mix to form a negative electrode ceramic insulating layer slurry with a solid content of 45%, coat it on the surface of the negative electrode active material layer, and dry it at 160℃ to obtain a negative electrode multilayer current collector. The remaining steps are the same as in Example 5.

[0029] Testing: The lithium-ion batteries prepared in the above examples and comparative examples were subjected to electrochemical performance tests.

[0030] 150℃ Hot Chamber Test: After the lithium-ion battery is fully charged, the temperature of the test chamber is increased to 150℃ at a rate of 5℃ / min, and maintained at this temperature for 2 hours. After 1 hour of observation, check whether the battery catches fire or explodes.

[0031] Thermal runaway temperature and resistance to lithium dendrite formation were tested: The system was evaluated using a battery management system.

[0032] Capacity retention test: The lithium battery is charged at a constant current of 1C to 3.65V, then charged at a constant voltage of 0.02C, and then discharged at a constant current of 1C to 2.5V. After 2000 cycles, the capacity retention rate is calculated.

[0033] The experimental results are shown in Table 1 below.

[0034] Table 1. Performance Test Data of Lithium-ion Batteries

[0035]

[0036] Conclusion: This invention, through a multi-coating design including a separator-less design, a composite current collector, and a lithium replenishment layer, reduces the weight of lithium-ion batteries, decreases electrolyte consumption, enhances resistance to lithium dendrite formation, and improves safety and cycle life.

[0037] In Comparative Example 1, the positive and negative electrode ceramic insulating layer slurries used alumina as the main insulator. Due to the lack of alumina nanowires to form a three-dimensional structure, the strength and toughness of the positive and negative electrode ceramic insulating coatings were reduced, increasing the risk of coating peeling and reducing the interfacial adhesion between the coating and the electrode; it also reduced the electrode's resistance to lithium dendrite formation. At the same time, the negative electrode lithium replenishment layer used lithium ferrite as the lithium replenishing agent, which reduced the coulombic efficiency and initial capacity of the first cycle.

[0038] In Comparative Example 2, aluminum foil and copper foil were used as current collectors, the positive and negative electrode coatings retained only the active material layer, and a lithium-ion battery was prepared using a polypropylene-polyethylene composite separator. Compared with the lithium-ion battery prepared in this invention, the electrochemical performance was worse.

[0039] In Comparative Example 3, aluminum foil and copper foil were used as current collectors, and the lithium replenishment layer was removed from the multilayer current collectors of the negative electrode. The battery was assembled using a separatorless design, which reduced the battery's first-efficiency cycle stability, decreased the battery weight and resistance to lithium dendrite formation, and could not work synergistically with the separatorless design of this invention to achieve the optimal electrochemical performance of the battery.

[0040] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A diaphragmless multilayer current collector, characterized in that: The membraneless multilayer current collector includes a positive electrode multilayer current collector and a negative electrode multilayer current collector; the structure of the positive electrode multilayer current collector, from bottom to top, consists of a positive electrode composite current collector, an LFP undercoat layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode ceramic insulating layer; the structure of the negative electrode multilayer current collector, from bottom to top, consists of a negative electrode composite current collector, a lithium replenishment layer, a negative electrode active material layer, and a negative electrode ceramic insulating layer.

2. The diaphragmless multilayer current collector according to claim 1, characterized in that: The preparation method of the positive electrode multilayer current collector is as follows: the polyethylene terephthalate (PET) layer is plasma etched, aluminum coating is deposited on both sides, and LFP undercoating slurry, solid electrolyte layer slurry, positive electrode active material layer slurry and positive electrode ceramic insulating layer slurry are sequentially coated and rolled on the surface of the aluminum coating to obtain the positive electrode multilayer current collector. The preparation method of the negative electrode multilayer current collector is as follows: the polyethylene terephthalate (PET) layer is plasma etched, and copper plating is applied by magnetron sputtering on both sides. The lithium replenishment layer slurry, the negative electrode active material layer slurry, and the negative electrode ceramic insulating layer slurry are sequentially coated and rolled on the surface of the copper plating layer to obtain the negative electrode multilayer current collector.

3. The diaphragmless multilayer current collector according to claim 2, characterized in that: The LFP undercoating slurry is prepared as follows: lithium iron phosphate, polyacrylonitrile and conductive carbon black are added to deionized water and mixed to make the solid content 50-60% to obtain the LFP undercoating slurry. In the preparation of LFP undercoat slurry, by mass fraction, it contains 90%-92% lithium iron phosphate, 3%-5% polyacrylonitrile and 3%-5% conductive carbon black.

4. The diaphragmless multilayer current collector according to claim 2, characterized in that: The solid electrolyte layer slurry is prepared as follows: Garnet-type lithium lanthanum zirconium oxide, polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide are added to N-methylpyrrolidone and mixed to make the solid content 50-60% to obtain the solid electrolyte layer slurry. In the preparation of the solid electrolyte layer slurry, the mass ratio of garnet-type lithium lanthanum zirconium oxide, polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide is (55-65):(25-35):(8-12).

5. The diaphragmless multilayer current collector according to claim 2, characterized in that: The preparation method of the positive electrode active material layer slurry is as follows: nickel-cobalt-manganese ternary material, carbon nanotubes and polyvinylidene fluoride are added to N-methylpyrrolidone and mixed to make the solid content 60%-70% to obtain the positive electrode active material layer slurry. In the preparation process of the positive electrode active material layer slurry, by mass fraction, it contains 88%-92% nickel-cobalt-manganese ternary materials, 3%-6% carbon nanotubes, and 3%-6% polyvinylidene fluoride.

6. The diaphragmless multilayer current collector according to claim 2, characterized in that: The preparation method of the positive electrode ceramic insulating layer slurry is as follows: S1: Dissolve aluminum chloride in an ethanol aqueous solution, then add a mixture of oleic acid and oleylamine, stir and mix well, heat at 150-170℃ for 6-8 hours, cool to room temperature, disperse and precipitate with cyclohexane and ethanol, centrifuge and wash, crush and sieve to obtain alumina nanowires. S2: Add alumina nanowires and polyacrylic acid to deionized water and mix to make the solid content 40%-50% to obtain positive electrode ceramic insulating layer slurry; In the preparation of the positive electrode ceramic insulating layer slurry, the mass ratio of aluminum chloride, oleic acid and oleylamine is 1:(1-3):(4-6); by mass fraction, it contains 85%-92% alumina nanowires and 8%-15% polyacrylic acid.

7. The diaphragmless multilayer current collector according to claim 2, characterized in that: The preparation method of the lithium replenishment slurry is as follows: S1: 3-mercapto-1,2,4-triazole is placed in anhydrous toluene solution, lithium metal powder is added under argon protection, the reaction is carried out at room temperature for 2-4 hours, filtered, washed with anhydrous toluene, and then evenly placed on a reaction vessel, and acetylene chemical vapor precipitation is carried out at 80-120℃ for 30-60 minutes to obtain carbon-coated lithium metal powder. S2: Under an argon atmosphere, carbon-coated lithium metal powder and styrene-butadiene rubber are added to deionized water and mixed to make the solid content 40%-50% to obtain a lithium replenishment slurry. In the preparation of the lithium replenishment slurry, the mass ratio of 3-mercapto-1,2,4-triazole to lithium metal powder is (10-20):1; by mass fraction, it contains 85%-92% carbon-coated lithium metal powder and 8%-15% styrene-butadiene rubber.

8. A diaphragmless multilayer current collector according to claim 2, characterized in that: The preparation method of the negative electrode active material is as follows: add artificial graphite or carbon silicon composite material, styrene-butadiene rubber and sodium carboxymethyl cellulose to deionized water, mix to make the solid content 50%-60%, and obtain negative electrode active material slurry; In the preparation of negative electrode active material slurry, by mass fraction, it consists of 90%-95% artificial graphite or carbon silicon composite material, 1%-5% styrene-butadiene rubber and 1%-5% sodium carboxymethyl cellulose.

9. A diaphragmless multilayer current collector according to claim 2, characterized in that: The preparation method of the negative electrode ceramic insulator is as follows: alumina nanowires, garnet-type lithium lanthanum zirconium oxide and polyurethane are added to deionized water and mixed to make the solid content 40%-50% to obtain a negative electrode ceramic insulation layer slurry. In the preparation of the negative electrode ceramic insulating layer slurry, by mass fraction, it consists of 76%-85% alumina nanowires, 7%-9% garnet-type lithium lanthanum zirconium oxide, and 8%-15% polyurethane.

10. The application of a membraneless multilayer current collector in solid-state lithium-ion batteries, characterized in that: Using the multilayer current collector according to any one of claims 1-9 to prepare a solid-state lithium-ion battery includes the following steps: S1: Mix ethylene carbonate and methyl ethyl carbonate evenly, then add lithium hexafluorophosphate and lithium difluorophosphate, stir and mix evenly to obtain a liquid electrolyte; S2: The positive electrode multilayer current collector and the negative electrode multilayer current collector are sequentially cut, stacked and wound, packaged, injected with 2-3g / Ah liquid electrolyte, formed and aged to obtain a solid-state lithium-ion battery; In the preparation process of solid-state lithium-ion batteries, the mass ratio of ethylene carbonate, ethyl methyl carbonate, lithium hexafluorophosphate and lithium difluorophosphate is (10-13):(10-20):(3-5):(1-1.5).

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