A high-conductivity nano-carbon-coated current collector and its preparation method

Abstract

The present invention discloses a highly conductive nano-carbon-coated current collector and a preparation method thereof. In order to improve the conductive properties of the current collector, the present invention prepares a conductive adhesive with high conductivity. In order to enhance the conductive properties of the conductive adhesive, the present invention first increases the amount of conductive carbon material added. At the same time, in order to avoid performance degradation caused by excessive conductive carbon material, the present invention further prepares a branched modified polyurethane acrylate resin, and utilizes its spherical spatial structure to reduce the overall viscosity of the adhesive, improve its flow properties, and increase the compatibility and dispersibility of the conductive carbon material in the system. In addition, the branched modified polyurethane acrylate resin also has a large number of acrylic groups, which can further increase the complexity of the cross-linked network, effectively improve the viscosity of the adhesive, and avoid the degradation of the bonding performance on the basis of improving the conductive ability.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, in particular to a highly conductive nano-carbon-coated current collector and a preparation method thereof. Background Art

[0002] Currently, in the manufacturing process of non-aqueous secondary batteries, in order to improve the battery's rate performance and the adhesion of the active material to the electrode, a layer of conductive material is usually coated on the surface of the current collector. The manufacturing process of this layer is usually to add a conductive agent and a binder into water, stir and disperse them, and then coat them on the surface of the current collector. However, since the binder is traditional acrylic glue, which is an insulating material, as the amount of glue added increases, the conductivity of the conductive layer becomes weaker. Excessive addition of conductive material will cause poor compatibility, agglomeration, and decreased adhesion, affecting the normal use of the current collector. Summary of the Invention

[0003] The object of the present invention is to provide a highly conductive nano-carbon-coated current collector and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions: a highly conductive nano-carbon-coated current collector having the following characteristics: the highly conductive nano-carbon-coated current collector comprises a current collector and a highly conductive nano-carbon-coated layer coated on both sides of the current collector;

[0005] Wherein, the current collector is any one of copper foil, aluminum foil, and copper-aluminum alloy foil;

[0006] The highly conductive nano carbon coating layer is formed by coating and drying a conductive adhesive.

[0007] Furthermore, the total thickness of the highly conductive nano-carbon-coated current collector is 3-20 μm; and the thickness of the current collector is 2-18 μm.

[0008] Furthermore, the thickness of the highly conductive nano-carbon coating layer is 0.5-1 μm.

[0009] Furthermore, the conductive adhesive comprises the following components, measured by weight: 10-15 parts of methyl methacrylate, 5-8 parts of hydroxyethyl methacrylate, 3-5 parts of vinyl acetate, 8-12 parts of isobornyl methacrylate, 15-25 parts of branched modified polyurethane acrylate resin, 0.1-0.3 parts of initiator, 0.3-0.5 parts of emulsifier, 10-25 parts of conductive carbon material, 40-50 parts of water, 0.5-1 parts of defoaming agent, 0.5-1 parts of dispersant, and 1-10 parts of isopropyl alcohol;

[0010] Wherein, the conductive carbon material is any one of conductive carbon black, CNT, graphene, and carbon nanofiber.

[0011] Furthermore, the preparation method of the branched modified polyurethane acrylate resin comprises the following steps:

[0012] a. P-phenylene diisocyanate was dissolved in DMF, dibutyltin diisocyanate was added, mixed well, heated to 35-38 ° C, and after the temperature was constant, 1,3,5-cyclohexanetriol was added dropwise, nitrogen atmosphere was protected, and the reaction was kept warm for 1-2 hours. The temperature was raised to 75-80 ° C, the reaction was continued for 4-6 hours, and the temperature was lowered to 45-55 ° C. Bis-mercaptoethyl sulfide was added dropwise, and the reaction was stirred for 1-1.5 hours. Isophorone diisocyanate was continued to be added dropwise. After the reaction was allowed to proceed for 2-4 hours, pentaerythritol was added, the temperature was raised to 75-80 ° C, the reaction was continued for 3-6 hours, and the excess solvent was removed by rotary evaporation to obtain a branched polyurethane polyol;

[0013] b. Under nitrogen atmosphere, isophorone diisocyanate and p-hydroxyanisole were dissolved in DMF, heated to 45-50 ° C, a DMF solution of hydroxypropyl methacrylate was added dropwise. After the addition was completed, the reaction was continued for 2-3h. The branched polyurethane polyol obtained in step a was added, heated to 75-80 ° C, and the reaction was allowed to proceed for 4-8h. The excess solvent was evaporated in vacuo to obtain a branched modified polyurethane acrylate resin.

[0014] Furthermore, in step a, the molar ratio of p-phenylene diisocyanate, dibutyltin diisocyanate, 1,3,5-cyclohexanetriol, bis-mercaptoethyl sulfide, isophorone diisocyanate, and pentaerythritol is (2.5-3.2): (0.01-0.03): 1: (2.5-3): (2.5-3): (2.2-3.2) by mole.

[0015] Furthermore, in step b, the mass ratio of isophorone diisocyanate, p-hydroxyanisole, hydroxypropyl methacrylate, and branched polyurethane polyol is (1.8-2.1): (0.01-0.02): (1.1-1.4) by mole:

[0016] (8-8.6).

[0017] Furthermore, the initiator is azobisisobutyronitrile; the emulsifier is nonylphenol polyoxyethylene ether; the defoamer is an organosilicon defoamer; and the dispersant is sodium dodecylbenzene sulfonate.

[0018] A method for preparing a highly conductive nano-carbon-coated current collector comprises the following steps:

[0019] S1. Methyl methacrylate, hydroxyethyl methacrylate, vinyl acetate, isobornyl methacrylate and a branched modified polyurethane acrylate resin were mixed, an emulsifier and water were added, and the mixture was stirred to obtain an acrylic monomer emulsion;

[0020] S2. The initiator is dissolved in isopropanol to obtain an initiator dropwise solution. The acrylic monomer emulsion prepared in step S1 is heated to 85-95°C and the initiator dropwise solution is slowly added dropwise thereto. After the addition is completed, the reaction is kept warm for 2-4 hours and then cooled to 30-45°C. A dispersant, a defoaming agent and a conductive carbon material are added and stirred for 0.5-1 hour to obtain a conductive adhesive.

[0021] S3. Apply the conductive adhesive to both sides of the current collector, heat it to 105-120°C, and dry it for 2-4 minutes to obtain a highly conductive nano-carbon-coated current collector.

[0022] In order to enhance the conductivity of the highly conductive nano-carbon coating layer, the present invention prepares a conductive adhesive and increases the amount of conductive carbon material added therein to ensure the conductive performance of the nano-conductive carbon coating layer. However, the addition of the conductive carbon material reduces the viscosity and coating performance of the conductive adhesive and affects its overall uniformity. Therefore, to avoid this phenomenon, the present invention further prepares a branched modified polyurethane acrylate resin with a branched structure.

[0023] The present invention first uses 1,3,5-cyclohexanetriol as a core molecule, adds it dropwise to p-phenylene diisocyanate, and reacts to form a three-arm compound with an isocyanate terminal group. The three-arm compound is further mixed with bismercaptoethyl sulfide, and the order of addition is controlled to control the terminal group of the reaction product to be an active mercapto group. The three-arm compound is further reacted with isophorone diisocyanate to generate an isocyanate terminal reaction product. The three-arm compound is then mixed with pentaerythritol again to finally form a branched polyurethane polyol with a terminal hydroxyl group.

[0024] On this basis, the present invention further mixes isophorone diisocyanate and hydroxypropyl methacrylate, limits the order of dropwise addition and reaction conditions, and prepares an acrylic monomer with a free isocyanate group. The acrylic monomer is then further mixed with a branched polyurethane polyol having a branched structure to generate a branched modified polyurethane acrylate resin. The branched modified polyurethane acrylate resin has a quasi-spherical spatial structure, which can effectively reduce the viscosity of the adhesive, thereby improving the dispersibility of the conductive carbon material in the adhesive. In addition, the end group of the modified polyurethane acrylate resin has a large number of active groups, which can form a denser cross-linked network, thereby improving the viscosity of the conductive adhesive.

[0025] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: in order to improve the conductivity of the current collector, the present invention prepares a conductive adhesive with high conductivity; in order to enhance the conductivity of the conductive adhesive, the present invention first increases the amount of conductive carbon material added, and at the same time, in order to avoid the performance degradation caused by excessive conductive carbon material, the present invention further prepares a branched modified polyurethane acrylate resin, and utilizes its spherical spatial structure to reduce the overall viscosity of the adhesive, improve its flow properties, and increase the compatibility and dispersion properties of the conductive carbon material in the system. In addition, the branched modified polyurethane acrylate resin also has a large number of acrylic groups, which can further improve the complexity of the cross-linked network, effectively improve the viscosity of the adhesive, and avoid the degradation of the bonding performance on the basis of improving the conductivity. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] Example 1.

[0028] A method for preparing a highly conductive nano-carbon-coated current collector comprises the following steps:

[0029] S1. In parts by weight, 10 parts of methyl methacrylate, 5 parts of hydroxyethyl methacrylate, 3 parts of vinyl acetate, 8 parts of isobornyl methacrylate and 15 parts of branched modified polyurethane acrylate resin were mixed, 0.3 parts of nonylphenol polyoxyethylene ether emulsifier and 80 parts of water were added, and the mixture was stirred to obtain an acrylic monomer emulsion;

[0030] The preparation method of the branched modified polyurethane acrylate resin comprises the following steps:

[0031] a. In molar parts, 2.5 mol of p-phenylene diisocyanate was dissolved in DMF, 0.01 mol of dibutyltin disilicate was added, mixed well, heated to 35 ° C, and after constant temperature, 1 mol of 1,3,5-cyclohexanetriol was added dropwise under nitrogen atmosphere for 1 hour, heated to 75 ° C, and the reaction was continued for 4 hours, cooled to 45 ° C, 2.5 mol of bis-mercaptoethyl sulfide was added dropwise, stirred for 1 hour, and then 2.5 mol of isophorone diisocyanate was added dropwise. After 2 hours of reaction, 2.2 mol of pentaerythritol was added, heated to 75 ° C, and the reaction was continued for 3 hours. The excess solvent was removed by rotary evaporation to obtain a branched polyurethane polyol;

[0032] b. By mass, under a nitrogen atmosphere, 18 parts of isophorone diisocyanate and 0.1 parts of p-hydroxyanisole were dissolved in DMF, the temperature was raised to 45 ° C, 11 parts of hydroxypropyl methacrylate in a DMF solution were added dropwise, and after the addition was completed, the reaction was continued for 2h, 80 parts of the branched polyurethane polyol obtained in step a were added, the temperature was raised to 75 ° C, the reaction was allowed to proceed for 4h, and the excess solvent was evaporated in vacuo to obtain a branched modified polyurethane acrylate resin.

[0033] S2. By weight, 0.1 parts of azobisisobutyronitrile initiator were dissolved in 1 part of isopropanol to obtain an initiator dropwise solution. The acrylic monomer emulsion prepared in step S1 was heated to 85 ° C and the initiator dropwise solution was slowly added thereto. After the addition was completed, the reaction was kept warm for 2 hours, then cooled to 30 ° C, 0.5 parts of sodium dodecylbenzenesulfonate dispersant, 0.5 parts of silicone defoamer and 55 parts of conductive carbon black were added, and stirring was continued for 0.5-1 hour to obtain a conductive adhesive;

[0034] S3. Apply the conductive adhesive to both sides of the current collector, heat it to 105°C, and dry it for 2 minutes to obtain a highly conductive nano-carbon-coated current collector.

[0035] Example 2.

[0036] Compared with Example 1, this example increases the amount of branched modified polyurethane acrylate resin added in step S1;

[0037] A method for preparing a highly conductive nano-carbon-coated current collector comprises the following steps:

[0038] S1. In parts by weight, 10 parts of methyl methacrylate, 5 parts of hydroxyethyl methacrylate, 3 parts of vinyl acetate, 8 parts of isobornyl methacrylate and 25 parts of branched modified polyurethane acrylate resin were mixed, 0.3 parts of nonylphenol polyoxyethylene ether emulsifier and 80 parts of water were added, and the mixture was stirred to obtain an acrylic monomer emulsion;

[0039] The preparation method of the branched modified polyurethane acrylate resin comprises the following steps:

[0040] a. In molar parts, 2.5 mol of p-phenylene diisocyanate was dissolved in DMF, 0.01 mol of dibutyltin disilicate was added, mixed well, heated to 35 ° C, and after constant temperature, 1 mol of 1,3,5-cyclohexanetriol was added dropwise under nitrogen atmosphere for 1 hour, heated to 75 ° C, and the reaction was continued for 4 hours, cooled to 45 ° C, 2.5 mol of bis-mercaptoethyl sulfide was added dropwise, stirred for 1 hour, and then 2.5 mol of isophorone diisocyanate was added dropwise. After 2 hours of reaction, 2.2 mol of pentaerythritol was added, heated to 75 ° C, and the reaction was continued for 3 hours. The excess solvent was removed by rotary evaporation to obtain a branched polyurethane polyol;

[0041] b. By mass, under a nitrogen atmosphere, 18 parts of isophorone diisocyanate and 0.1 parts of p-hydroxyanisole were dissolved in DMF, the temperature was raised to 45 ° C, 11 parts of hydroxypropyl methacrylate in a DMF solution were added dropwise, and after the addition was completed, the reaction was continued for 2h, 80 parts of the branched polyurethane polyol obtained in step a were added, the temperature was raised to 75 ° C, the reaction was allowed to proceed for 4h, and the excess solvent was evaporated in vacuo to obtain a branched modified polyurethane acrylate resin.

[0042] S2. By weight, 0.1 parts of azobisisobutyronitrile initiator were dissolved in 1 part of isopropanol to obtain an initiator dropwise solution. The acrylic monomer emulsion prepared in step S1 was heated to 85 ° C and the initiator dropwise solution was slowly added thereto. After the addition was completed, the reaction was kept warm for 2 hours, then cooled to 30 ° C, 0.5 parts of sodium dodecylbenzenesulfonate dispersant, 0.5 parts of silicone defoamer and 55 parts of conductive carbon black were added, and stirring was continued for 0.5-1 hour to obtain a conductive adhesive;

[0043] S3. Apply the conductive adhesive to both sides of the current collector, heat it to 105°C, and dry it for 2 minutes to obtain a highly conductive nano-carbon-coated current collector.

[0044] Example 3.

[0045] Compared with Example 2, this example increases the amount of p-phenylenediisocyanate added in step a;

[0046] A method for preparing a highly conductive nano-carbon-coated current collector comprises the following steps:

[0047] S1. In parts by weight, 10 parts of methyl methacrylate, 5 parts of hydroxyethyl methacrylate, 3 parts of vinyl acetate, 8 parts of isobornyl methacrylate and 25 parts of branched modified polyurethane acrylate resin were mixed, 0.3 parts of nonylphenol polyoxyethylene ether emulsifier and 80 parts of water were added, and the mixture was stirred to obtain an acrylic monomer emulsion;

[0048] The preparation method of the branched modified polyurethane acrylate resin comprises the following steps:

[0049] a. In molar parts, 3.2 mol of p-phenylene diisocyanate was dissolved in DMF, 0.01 mol of dibutyltin silicate in February was added, mixed evenly, heated to 35 ° C, and after constant temperature, 1 mol of 1,3,5-cyclohexanetriol was added dropwise under nitrogen atmosphere for 1 hour, heated to 75 ° C, and the reaction was continued for 4 hours, cooled to 45 ° C, 2.5 mol of bis-mercaptoethyl sulfide was added dropwise, stirred for 1 hour, and then 2.5 mol of isophorone diisocyanate was added dropwise. After 2 hours of reaction, 2.2 mol of pentaerythritol was added, heated to 75 ° C, and the reaction was continued for 3 hours. The excess solvent was removed by rotary evaporation to obtain a branched polyurethane polyol;

[0050] b. By mass, under a nitrogen atmosphere, 18 parts of isophorone diisocyanate and 0.1 parts of p-hydroxyanisole were dissolved in DMF, the temperature was raised to 45 ° C, 11 parts of hydroxypropyl methacrylate in a DMF solution were added dropwise, and after the addition was completed, the reaction was continued for 2h, 80 parts of the branched polyurethane polyol obtained in step a were added, the temperature was raised to 75 ° C, the reaction was allowed to proceed for 4h, and the excess solvent was evaporated in vacuo to obtain a branched modified polyurethane acrylate resin.

[0051] S2. By weight, 0.1 parts of azobisisobutyronitrile initiator were dissolved in 1 part of isopropanol to obtain an initiator dropwise solution. The acrylic monomer emulsion prepared in step S1 was heated to 85 ° C and the initiator dropwise solution was slowly added thereto. After the addition was completed, the reaction was kept warm for 2 hours, then cooled to 30 ° C, 0.5 parts of sodium dodecylbenzenesulfonate dispersant, 0.5 parts of silicone defoamer and 55 parts of conductive carbon black were added, and stirring was continued for 0.5-1 hour to obtain a conductive adhesive;

[0052] S3. Apply the conductive adhesive to both sides of the current collector, heat it to 105°C, and dry it for 2 minutes to obtain a highly conductive nano-carbon-coated current collector.

[0053] Example 4.

[0054] Compared with Example 2, this example increases the amount of bis-mercaptoethyl sulfide added in step a;

[0055] A method for preparing a highly conductive nano-carbon-coated current collector comprises the following steps:

[0056] S1. In parts by weight, 10 parts of methyl methacrylate, 5 parts of hydroxyethyl methacrylate, 3 parts of vinyl acetate, 8 parts of isobornyl methacrylate and 25 parts of branched modified polyurethane acrylate resin were mixed, 0.3 parts of nonylphenol polyoxyethylene ether emulsifier and 80 parts of water were added, and the mixture was stirred to obtain an acrylic monomer emulsion;

[0057] The preparation method of the branched modified polyurethane acrylate resin comprises the following steps:

[0058] a. In molar parts, 2.5 mol of p-phenylene diisocyanate was dissolved in DMF, 0.01 mol of dibutyltin silicate in February was added, mixed evenly, heated to 35 ° C, and after constant temperature, 1 mol of 1,3,5-cyclohexanetriol was added dropwise under nitrogen atmosphere for 1 hour, heated to 75 ° C, and the reaction was continued for 4 hours, cooled to 45 ° C, 3 mol of bis-mercaptoethyl sulfide was added dropwise, stirred for 1 hour, and then 2.5 mol of isophorone diisocyanate was added dropwise. After 2 hours of reaction, 2.2 mol of pentaerythritol was added, heated to 75 ° C, and the reaction was continued for 3 hours. The excess solvent was removed by rotary evaporation to obtain a branched polyurethane polyol;

[0059] b. By mass, under a nitrogen atmosphere, 18 parts of isophorone diisocyanate and 0.1 parts of p-hydroxyanisole were dissolved in DMF, the temperature was raised to 45 ° C, 11 parts of hydroxypropyl methacrylate in a DMF solution were added dropwise, and after the addition was completed, the reaction was continued for 2h, 80 parts of the branched polyurethane polyol obtained in step a were added, the temperature was raised to 75 ° C, the reaction was allowed to proceed for 4h, and the excess solvent was evaporated in vacuo to obtain a branched modified polyurethane acrylate resin.

[0060] S2. By weight, 0.1 parts of azobisisobutyronitrile initiator were dissolved in 1 part of isopropanol to obtain an initiator dropwise solution. The acrylic monomer emulsion prepared in step S1 was heated to 85 ° C and the initiator dropwise solution was slowly added thereto. After the addition was completed, the reaction was kept warm for 2 hours, then cooled to 30 ° C, 0.5 parts of sodium dodecylbenzenesulfonate dispersant, 0.5 parts of silicone defoamer and 55 parts of conductive carbon black were added, and stirring was continued for 0.5-1 hour to obtain a conductive adhesive;

[0061] S3. Apply the conductive adhesive to both sides of the current collector, heat it to 105°C, and dry it for 2 minutes to obtain a highly conductive nano-carbon-coated current collector.

[0062] Example 5.

[0063] Compared with Example 2, this example increases the amount of pentaerythritol added in step a;

[0064] A method for preparing a highly conductive nano-carbon-coated current collector comprises the following steps:

[0065] S1. In parts by weight, 10 parts of methyl methacrylate, 5 parts of hydroxyethyl methacrylate, 3 parts of vinyl acetate, 8 parts of isobornyl methacrylate and 25 parts of branched modified polyurethane acrylate resin were mixed, 0.3 parts of nonylphenol polyoxyethylene ether emulsifier and 80 parts of water were added, and the mixture was stirred to obtain an acrylic monomer emulsion;

[0066] The preparation method of the branched modified polyurethane acrylate resin comprises the following steps:

[0067] a. In molar parts, 2.5 mol of p-phenylene diisocyanate was dissolved in DMF, 0.01 mol of dibutyltin silicate in February was added, mixed evenly, heated to 35 ° C, and after constant temperature, 1 mol of 1,3,5-cyclohexanetriol was added dropwise under nitrogen atmosphere for 1 hour, heated to 75 ° C, and the reaction was continued for 4 hours, cooled to 45 ° C, 2.5 mol of bis-mercaptoethyl sulfide was added dropwise, stirred for 1 hour, and then 2.5 mol of isophorone diisocyanate was added dropwise. After 2 hours of reaction, 3.2 mol of pentaerythritol was added, heated to 75 ° C, and the reaction was continued for 3 hours. The excess solvent was removed by rotary evaporation to obtain a branched polyurethane polyol;

[0068] b. By mass, under a nitrogen atmosphere, 18 parts of isophorone diisocyanate and 0.1 parts of p-hydroxyanisole were dissolved in DMF, the temperature was raised to 45 ° C, 11 parts of hydroxypropyl methacrylate in a DMF solution were added dropwise, and after the addition was completed, the reaction was continued for 2h, 80 parts of the branched polyurethane polyol obtained in step a were added, the temperature was raised to 75 ° C, the reaction was allowed to proceed for 4h, and the excess solvent was evaporated in vacuo to obtain a branched modified polyurethane acrylate resin.

[0069] S2. By weight, 0.1 parts of azobisisobutyronitrile initiator were dissolved in 1 part of isopropanol to obtain an initiator dropwise solution. The acrylic monomer emulsion prepared in step S1 was heated to 85 ° C and the initiator dropwise solution was slowly added thereto. After the addition was completed, the reaction was kept warm for 2 hours, then cooled to 30 ° C, 0.5 parts of sodium dodecylbenzenesulfonate dispersant, 0.5 parts of silicone defoamer and 55 parts of conductive carbon black were added, and stirring was continued for 0.5-1 hour to obtain a conductive adhesive;

[0070] S3. Apply the conductive adhesive to both sides of the current collector, heat it to 105°C, and dry it for 2 minutes to obtain a highly conductive nano-carbon-coated current collector.

[0071] Example 6.

[0072] A method for preparing a highly conductive nano-carbon-coated current collector comprises the following steps:

[0073] S1. In parts by weight, 15 parts of methyl methacrylate, 8 parts of hydroxyethyl methacrylate, 5 parts of vinyl acetate, 12 parts of isobornyl methacrylate and 25 parts of branched modified polyurethane acrylate resin were mixed, 0.5 parts of nonylphenol polyoxyethylene ether emulsifier and 100 parts of water were added, and the mixture was stirred to obtain an acrylic monomer emulsion;

[0074] The preparation method of the branched modified polyurethane acrylate resin comprises the following steps:

[0075] a. In molar parts, 3.2 mol of p-phenylene diisocyanate was dissolved in DMF, 0.03 mol of dibutyltin disilicate was added, mixed evenly, heated to 38 ° C, and after constant temperature, 1 mol of 1,3,5-cyclohexanetriol was added dropwise under nitrogen atmosphere for 2 hours, then heated to 80 ° C, the reaction was continued for 6 hours, cooled to 55 ° C, 3 mol of bis-mercaptoethyl sulfide was added dropwise, the reaction was stirred for 1.5 hours, and then 3 mol of isophorone diisocyanate was added dropwise. After 4 hours of reaction, 3.2 mol of pentaerythritol was added, the temperature was raised to 80 ° C, the reaction was continued for 6 hours, and the excess solvent was removed by rotary evaporation to obtain a branched polyurethane polyol;

[0076] b. By mass, under nitrogen atmosphere, 21 parts of isophorone diisocyanate and 0.2 parts of p-hydroxyanisole were dissolved in DMF, heated to 50 ° C, 14 parts of hydroxypropyl methacrylate in DMF solution were added dropwise. After the addition was completed, the reaction was continued for 3h, 86 parts of the branched polyurethane polyol obtained in step a were added, the temperature was raised to 80 ° C, the reaction was allowed to proceed for 8h, and the excess solvent was evaporated in vacuo to obtain a branched modified polyurethane acrylate resin.

[0077] S2. Dissolve 0.3 parts of azobisisobutyronitrile initiator in 20 parts of isopropanol by weight to obtain an initiator dropwise solution. Heat the acrylic monomer emulsion prepared in step S1 to 95°C and slowly add the initiator dropwise solution thereto. After the addition is completed, keep the mixture warm for 4 hours, cool it to 45°C, add 1 part of sodium dodecylbenzenesulfonate dispersant, 1 part of silicone defoamer and 75 parts of conductive carbon black, and continue stirring for 1 hour to obtain a conductive adhesive.

[0078] S3. Apply the conductive adhesive to both sides of the current collector, heat it to 110°C, and dry it for 4 minutes to obtain a highly conductive nano-carbon-coated current collector.

[0079] Comparative Example 1.

[0080] Compared with Example 1, this comparative example did not prepare branched polyurethane acrylate resin, and only used an equal amount of PVDF as a binder;

[0081] A method for preparing a highly conductive nano-carbon-coated current collector comprises the following steps:

[0082] S1. In parts by weight, 41 parts of PVDF were mixed with 80 parts of water, 0.5 parts of sodium dodecylbenzenesulfonate dispersant, 0.5 parts of silicone defoamer and 55 parts of conductive carbon black were added, and stirring was continued for 0.5-1h to obtain a conductive adhesive;

[0083] S3. Apply the conductive adhesive to both sides of the current collector, heat it to 105°C, and dry it for 2 minutes to obtain a highly conductive nano-carbon-coated current collector.

[0084] Detection:

[0085] The highly conductive nano-carbon-coated current collectors prepared in Examples 1-6 and Comparative Example 1 were prepared into lithium batteries, and the following tests were performed on them;

[0086] Rate performance 5C test: At a temperature of 25℃±5℃, the battery is charged at a constant current of 0.2C to the limit voltage, then switched to constant voltage charging until the cutoff current reaches 0.01C. Charging is then stopped. The battery is then discharged at a current of 5C to the cutoff voltage, and the discharge capacity is obtained. The capacity retention rate is calculated based on the discharge capacity and the initial capacity.

[0087] Cycling performance test: At a temperature of 25℃±5℃, charge the battery at a constant current of 1C to the limit voltage, then change to constant voltage charging until the cutoff current reaches 0.01C and stop charging; discharge at a current of 1C to the termination voltage, cycle continuously for 1000 times, and obtain the discharge capacity. The capacity retention rate is calculated based on the discharge capacity and the initial capacity.

[0088] High-temperature performance test: At a temperature of 25°C ± 5°C, charge the battery at a constant current of 0.2C to the limit voltage, then switch to constant voltage charging until the cutoff current reaches 0.01C and stop charging. Then, after placing the battery at a temperature of 60°C ± 2°C for 2 hours, discharge the battery at 1C to the cutoff voltage and calculate the capacity retention rate.

[0089] Low-temperature performance test: At a temperature of 25°C ± 5°C, charge the battery at a constant current of 0.2C to the limit voltage, then switch to constant voltage charging until the cutoff current reaches 0.01C and stop charging. Then, after placing the battery at a temperature of 60°C ± 2°C for 2 hours, discharge the battery at 1C to the cutoff voltage and calculate the capacity retention rate.

[0090] The test results are shown in the table below:

[0091]

[0092]

[0093] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A highly conductive nano-carbon-coated current collector, characterized by: The highly conductive nano-carbon-coated current collector comprises a current collector and a highly conductive nano-carbon-coated layer coated on both sides of the current collector; Wherein, the current collector is any one of copper foil, aluminum foil, and copper-aluminum alloy foil; The highly conductive nano carbon coating layer is formed by coating and drying a conductive adhesive; The conductive adhesive comprises the following components in parts by weight: 10-15 parts of methyl methacrylate, 5-8 parts of hydroxyethyl methacrylate, 3-5 parts of vinyl acetate, 8-12 parts of isobornyl methacrylate, 15-25 parts of branched modified polyurethane acrylate resin, 0.1-0.3 parts of initiator, 0.3-0.5 parts of emulsifier, 55-75 parts of conductive carbon material, 80-100 parts of water, 0.5-1 parts of defoaming agent, 0.5-1 parts of dispersant, and 1-20 parts of isopropyl alcohol; Wherein, the conductive carbon material is any one of conductive carbon black, CNT, graphene, and carbon nanofiber; The preparation method of the branched modified polyurethane acrylate resin comprises the following steps: a. P-phenylene diisocyanate was dissolved in DMF, dibutyltin diisocyanate was added, mixed well, heated to 35-38 ° C, and after the temperature was constant, 1,3,5-cyclohexanetriol was added dropwise, nitrogen atmosphere was protected, and the reaction was kept warm for 1-2 hours. The temperature was raised to 75-80 ° C, the reaction was continued for 4-6 hours, and the temperature was lowered to 45-55 ° C. Bis-mercaptoethyl sulfide was added dropwise, and the reaction was stirred for 1-1.5 hours. Isophorone diisocyanate was continued to be added dropwise. After the reaction was allowed to proceed for 2-4 hours, pentaerythritol was added, the temperature was raised to 75-80 ° C, the reaction was continued for 3-6 hours, and the excess solvent was removed by rotary evaporation to obtain a branched polyurethane polyol; b. Under nitrogen atmosphere, isophorone diisocyanate and p-hydroxyanisole were dissolved in DMF, heated to 45-50 ° C, a DMF solution of hydroxypropyl methacrylate was added dropwise. After the addition was completed, the reaction was continued for 2-3h. The branched polyurethane polyol obtained in step a was added, heated to 75-80 ° C, and the reaction was allowed to proceed for 4-8h. The excess solvent was evaporated in vacuo to obtain a branched modified polyurethane acrylate resin.

2. The highly conductive nano-carbon-coated current collector according to claim 1, characterized in that: The total thickness of the highly conductive nano-carbon-coated current collector is 3-20 μm; the thickness of the current collector is 2-18 μm.

3. The highly conductive nano-carbon-coated current collector according to claim 1, characterized in that: The thickness of the highly conductive nano carbon coating layer is 0.5-1 μm.

4. The highly conductive nano-carbon-coated current collector according to claim 1, characterized in that: The initiator is azobisisobutyronitrile; the emulsifier is nonylphenol polyoxyethylene ether; the defoamer is an organosilicon defoamer; and the dispersant is sodium dodecylbenzene sulfonate.

5. The highly conductive nano-carbon-coated current collector according to claim 1, characterized in that: In step a, based on molar ratios, the molar ratios of p-phenylene diisocyanate, dibutyltin diisocyanate, 1,3,5-cyclohexanetriol, bismercaptoethyl sulfide, isophorone diisocyanate, and pentaerythritol are (2.5-3.2):(0.01-0.03):1:(2.5-3):(2.5-3):(2.2-3.2).

6. The highly conductive nano-carbon-coated current collector according to claim 1, characterized in that: In step b, the mass ratio of isophorone diisocyanate, p-hydroxyanisole, hydroxypropyl methacrylate and branched polyurethane polyol is (1.8-2.1): (0.01-0.02): (1.1-1.4): (8-8.6) by mole.

7. The method for preparing a highly conductive nano-carbon-coated current collector according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Methyl methacrylate, hydroxyethyl methacrylate, vinyl acetate, isobornyl methacrylate and a branched modified polyurethane acrylate resin were mixed, an emulsifier and water were added, and the mixture was stirred to obtain an acrylic monomer emulsion; S2. The initiator is dissolved in isopropanol to obtain an initiator dropwise solution. The acrylic monomer emulsion prepared in step S1 is heated to 85-95°C and the initiator dropwise solution is slowly added dropwise thereto. After the addition is completed, the reaction is kept warm for 2-4 hours and then cooled to 30-45°C. A dispersant, a defoaming agent and a conductive carbon material are added and stirred for 0.5-1 hour to obtain a conductive adhesive. S3. Apply the conductive adhesive to both sides of the current collector, heat to 105-120°C, dry for 2-4 minutes, and then roll up to obtain a highly conductive nano-carbon-coated current collector.

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