NANO carbon-coated copper current collector specially for lithium battery negative electrode

Abstract

A nano carbon-coated copper current collector specially for a lithium battery negative electrode. By adding a soft styrene-butadiene rubber (SBR) binder to improve the adhesion to a lithium battery negative electrode, the peel strength between a lithium battery negative electrode sheet and a nano carbon-coated copper current collector is improved, thereby solving the problems of degraded electrical performance and shortened service life of a battery caused by electrode sheet powder shedding during the manufacture of the battery. Sodium carboxymethyl cellulose and a metal organic framework material are loaded together, then epoxidized SBR is coated on the outside of a metal organic framework-sodium carboxymethyl cellulose composite, such that the compatibility of the metal organic framework-sodium carboxymethyl cellulose composite in a slurry is improved, and the adhesion to the lithium battery negative electrode is further improved, thereby prolonging the service life of the battery.

Description

A new type of special nanometer carbon-coated copper current collector for lithium battery negative electrode TECHNICAL FIELD

[0001] The present application relates to the technical field of current collectors, for example, a new type of special nanometer carbon-coated copper current collector for lithium battery negative electrode. BACKGROUND

[0002] The current process route of nanometer carbon-coated copper foil is mainly as follows: first, nanometer conductive material, binder, crosslinking agent, solvent, and wetting agent are dispersed at high speed to form slurry; then the dispersed slurry is coated onto the upper and lower surfaces of the copper current collector by a coating machine, dried by an oven, and then the nanometer carbon-coated current collector is wound. The nanometer carbon-coated copper current collector prepared by the above conventional method needs to be rolled after being coated with active material to form a battery electrode sheet. Since the binder in the conventional nanometer conductive coating on the surface of the copper current collector is mainly PAA binder, and the main component of the lithium battery PAA negative electrode binder is also PAA binder, the PAA binder is relatively hard, which leads to poor adhesion between the lithium battery PAA negative electrode and the conventional nanometer carbon-coated copper current collector. During the rolling process of the electrode sheet, the poor adhesion leads to poor peeling force between the lithium battery PAA negative electrode sheet and the nanometer carbon-coated copper current collector. During the manufacturing process of the battery, the electrode sheet powdering and other abnormalities occur, which causes the battery to have poor electrical performance and low service life.

[0003] In summary, the problem of electrode sheet powdering needs to be solved in the art to improve the electrical performance and service life of the battery. SUMMARY

[0004] The following is a summary of the subject matter of the detailed description herein. This summary is not intended to limit the scope of the claims.

[0005] To solve the above technical problems, the present application provides the following technical solution: a new type of special nanometer carbon-coated copper current collector for lithium battery negative electrode.

[0006] A new type of special nanometer carbon-coated copper current collector for lithium battery negative electrode, the nanometer carbon-coated copper current collector comprises a copper current collector and a conductive layer coated on at least one side surface of the copper current collector.

[0007] In the present application, the nanometer in the nanometer carbon-coated copper current collector refers to the particle size of the carbon-coated slurry being in the nanometer range.

[0008] The copper current collector is any one of a metal copper foil or a composite copper current collector, and the copper composite current collector contains any one or more of high molecular materials such as PET, PP, PI, and PTFE.

[0009] More preferably, the conductive layer is prepared by coating a slurry made of carbon conductive material, sodium carboxymethyl cellulose, crosslinking agent, styrene-butadiene rubber binder, wetting agent, solvent, and baking; the mass ratio of the carbon conductive material, sodium carboxymethyl cellulose, crosslinking agent, styrene-butadiene rubber binder, wetting agent, and solvent is (1.1-1.5):(0.1-0.5):(0.01-0.05):(1-2):(0.01-0.05):(10-20); the carbon conductive material is any one or more of conductive carbon black, conductive graphite, graphene, and carbon nanotube; the crosslinking agent is any one or more of sodium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide.

[0010] More preferably, the conductive layer is obtained by coating and baking a slurry, and the preparation method of the slurry comprises the following steps:

[0011] Step one: disperse the carbon conductive material and sodium carboxymethyl cellulose at a temperature of 25-45°C and a rotation speed of 2000-3000 r / min for 60-100 minutes; add the solvent and disperse at high speed for 60-100 minutes;

[0012] Step two: add the crosslinking agent and the binder and disperse at a temperature of 25-45°C and a rotation speed of 2000-3000 r / min for 60-100 minutes; finally add the wetting agent and disperse at high speed to obtain the slurry.

[0013] More preferably, any one or more of the following conditions is met:

[0014] (1) the carbon conductive material is any one or more of conductive carbon black, conductive graphite, graphene, and carbon nanotube;

[0015] (2) the crosslinking agent is any one or more of sodium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide.

[0016] More preferably, the preparation method of the nano-coated copper current collector comprises the following steps:

[0017] S1: disperse the conductive carbon black, conductive graphite, and sodium carboxymethyl cellulose at a temperature of 25-45°C and a rotation speed of 2000-3000 r / min for 60-100 minutes, and add the solvent and disperse at high speed to obtain a mixed solution;

[0018] S2: add the crosslinking agent and the styrene-butadiene rubber binder and disperse at high speed, and finally add the wetting agent and disperse at high speed to obtain the slurry;

[0019] S3: use the slurry to coat the upper and lower surfaces of the copper current collector, bake and roll to obtain the nano-coated copper current collector.

[0020] More preferably, the mass ratio of the conductive carbon black, the conductive graphite, the sodium carboxymethyl cellulose, the crosslinking agent, the butadiene-styrene rubber binder, the wetting agent, and the solvent is 1:(0.1-0.5):(0.1-0.5):(0.01-0.05):(1-2):(0.01-0.05):(10-20); wherein the butadiene-styrene rubber binder is calculated in terms of the mass of its solid components.

[0021] More preferably, the sodium carboxymethyl cellulose is a modified sodium carboxymethyl cellulose composite, and the preparation method comprises the following steps:

[0022] Step A: Take the metal-organic framework material and deionized water, ultrasonic dispersion, add sodium carboxymethyl cellulose, heat to 60-65℃, stir for 8-10h, filter, wash, and dry to obtain a metal-organic framework-sodium carboxymethyl cellulose composite;

[0023] Step B: Take the metal-organic framework-sodium carboxymethyl cellulose composite and deionized water, ultrasonic dispersion for 8-10h to obtain a dispersion liquid; take the butadiene-styrene rubber binder and toluene, stir for 5-6h to obtain a butadiene-styrene rubber solution; drop the epoxidized butadiene-styrene rubber solution into the dispersion liquid, ultrasonic dispersion for 6-7h, centrifugal, wash, and dry to obtain a modified sodium carboxymethyl cellulose composite.

[0024] More preferably, the butadiene-styrene rubber binder is an epoxidized butadiene-styrene rubber binder, and the preparation method comprises the following steps: take the butadiene-styrene rubber binder and cyclopentane, stir uniformly, then heat to 40-45℃, add formic acid and polyethylene glycol, drop hydrogen peroxide, react at 40-45℃ for 3-3.5h, wash with distilled water, and dry to obtain the epoxidized butadiene-styrene rubber binder.

[0025] More preferably, the preparation method of the metal-organic framework material comprises the following steps: take zinc nitrate hexahydrate and methanol, stir uniformly to obtain a mixed solution; take 2-methyl imidazole and methanol, stir uniformly, add the mixed solution, stir at 25-30℃ for 22-26h, heat to 120-130℃, react for 10-12h, wash, precipitate, and dry to obtain the metal-organic framework material.

[0026] More preferably, the following conditions are met: the carbon conductive material is an aminated carbon conductive material, and the preparation method of the aminated carbon conductive material comprises the following steps: take N,N'-dicyclohexyl carbodiimide and tetrahydrofuran, stir uniformly to obtain a mixed solution; take the carbon conductive material and dimethyl formamide, stir uniformly, add ethylenediamine and the mixed solution, continue to stir for 3-4h, filter, wash, and dry to obtain the aminated carbon conductive material.

[0027] Compared with the related art, the present application has the following beneficial effects:

[0028] (1) The present application improves the adhesion of the lithium battery negative electrode by adding carboxymethyl cellulose sodium CMC to disperse the conductive agent and adding soft hardness butyl rubber adhesive SBR to improve the adhesion of the lithium battery negative electrode, and improves the peeling force between the lithium battery negative electrode sheet and the nano-coated carbon copper current collector.

[0029] (2) The nano-coated carbon copper current collector prepared in the present application has a thickness of 2-15 microns. If the thickness is less than 2 microns, the mechanical strength of the nano-coated carbon copper current collector is low, and the belt is prone to breakage, which cannot meet the process requirements of the lithium battery sheet manufacturing. If the thickness is greater than 15 microns, the thickness of the nano-coated carbon copper current collector is too large, which affects the energy density of the battery and increases the cost.

[0030] (3) The areal density of the single-sided coating of the nano-coated carbon copper current collector is 0.1-2.0 g / m2. If the areal density of the single-sided coating is less than 0.1 g / m2, the interface resistance between the negative active material and the copper current collector cannot be effectively improved. If the areal density of the single-sided coating is greater than 2.0 g / m2, the cost of the conductive coating is too high.

[0031] (4) The present application loads carboxymethyl cellulose sodium and metal organic framework material together, and then coats the metal organic framework-carboxymethyl cellulose sodium composite with epoxidized butyl rubber, which improves the compatibility of the metal organic framework-carboxymethyl cellulose sodium composite in the slurry and further improves the adhesion to the lithium battery negative electrode. The present application also carries out aminoization treatment on the conductive carbon black and conductive graphite, and the amino groups on the conductive carbon black and conductive graphite can react with the epoxy groups in the epoxidized butyl rubber adhesive, so that the conductive carbon black and conductive graphite are better dispersed, the peeling force between the lithium battery negative electrode sheet and the nano-coated carbon copper current collector is improved, and the battery life is improved.

[0032] Other aspects can be apparent after reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings are used to provide further understanding of the present application, and constitute a part of the specification. They are used to explain the present application together with embodiments of the present application, and do not constitute a limitation of the present application. In the drawings:

[0034] Fig. 1 is a schematic view of the structure of the new nano-coated carbon copper current collector for lithium battery negative electrode of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0036] The model numbers and purchase manufacturers of all raw materials involved in the present application are not specially limited, and exemplary ones include: conductive carbon black: particle size: 0.2-0.8 um, which can be purchased from Tianjin Youmeng Chemical Technology Co., Ltd.; conductive graphite: particle size 1250 mesh, which can be purchased from Qingdao Risheng Graphite Co., Ltd.; sodium carboxymethyl cellulose: which can be purchased from Merck, model number: 419338; butyl rubber adhesive: SBR: which can be purchased from Sinopec, model number: YH-792E; polyacrylic acid adhesive: which can be purchased from Sanwin New Material, model number SY-302.

[0037] Embodiment 1: A preparation method of a new type of nano-coated carbon copper current collector special for lithium battery negative electrodes, comprising the following steps:

[0038] Step one: 60 kg of conductive carbon black, 20 kg of conductive graphite and 20 kg of sodium carboxymethyl cellulose are added to a double-planet high-speed dispersion device for high-speed dispersion, at a speed of 2500 r / min, for 60 minutes, at a dispersion temperature of 25°C; 1000 kg of solvent water is added for high-speed dispersion; at a speed of 2500 r / min, for 60 minutes, at a dispersion temperature of 25°C;

[0039] Step two: 1 kg of calcium hydroxide crosslinking agent and 300 kg of butyl rubber adhesive with a solid content of 25% are added for high-speed dispersion; at a speed of 2500 r / min, for 60 minutes, at a dispersion temperature of 25°C; finally, 10 kg of wetting agent polyethylene glycol is added for high-speed dispersion; at a speed of 2500 r / min, for 60 minutes, at a dispersion temperature of 25°C, to obtain a slurry;

[0040] Step three: the slurry is coated on a copper current collector with a thickness of 6 microns and a width of 800 mm by a coating machine, and the single-sided coating density of the nano-coated carbon copper current collector is 1 g / m2, then the flame-retardant nano-coated carbon layer is dried by three-section ovens, the drying temperatures of the upper three-section ovens are 60°C, 80°C and 70°C respectively, and the drying temperatures of the lower three-section ovens are 60°C, 80°C and 70°C respectively, after drying, the coated carbon copper current collector is wound by winding equipment, the unwinding tension is 300 N, the winding tension is 500 N / m, and the nano-coated carbon copper current collector is obtained.

[0041] Embodiment 2: A preparation method of a new type of nano-coated carbon copper current collector special for lithium battery negative electrodes, comprising the following steps:

[0042] Step one:

[0043] S1: Preparation of epoxidized styrene-butadiene rubber adhesive:

[0044] Take 150 g of styrene-butadiene rubber adhesive and 1500 mL of cyclopentane, stir evenly, then heat to 43℃, add 32 mL of formic acid, 5 g of polyethylene glycol, drop 30 mL of hydrogen peroxide, react at 43℃ for 3 hours, wash with distilled water, dry to get epoxidized styrene-butadiene rubber adhesive;

[0045] S2: Preparation of modified sodium carboxymethyl cellulose complex:

[0046] (1) Preparation of metal organic framework material:

[0047] Take 2 g of zinc nitrate hexahydrate and 80 mL of methanol, stir evenly to get a mixed solution; take 3.5 g of 2-methylimidazole and 80 mL of methanol, stir evenly, add the mixed solution, stir at 27℃ for 24h, heat to 125℃, react for 11h, wash, precipitate and dry to get the metal organic framework material;

[0048] (2) Preparation of metal organic framework-sodium carboxymethyl cellulose complex:

[0049] Take 0.5 g of metal organic framework material and 50 mL of deionized water, ultrasonic dispersion, add 5 g of sodium carboxymethyl cellulose, heat to 63℃, stir for 9h, filter, wash and dry to get the metal organic framework-sodium carboxymethyl cellulose complex;

[0050] (3) Preparation of modified sodium carboxymethyl cellulose complex:

[0051] Take 5 g of metal organic framework-sodium carboxymethyl cellulose complex and 200 mL of deionized water, ultrasonic dispersion for 9h to get a dispersion liquid; take 1 g of epoxidized styrene-butadiene rubber adhesive and 8 g of toluene, stir for 5.5h to get an epoxidized styrene-butadiene rubber solution; drop the epoxidized styrene-butadiene rubber solution into the dispersion liquid, ultrasonic dispersion for 6.5h, centrifugal, wash and dry to get the modified sodium carboxymethyl cellulose complex;

[0052] S3: Preparation of aminated conductive carbon black and aminated conductive graphite:

[0053] (1) Take 1.5 mL of N,N'-dicyclohexyl carbodiimide and 12 mL of tetrahydrofuran, stir evenly to get a mixed solution; take 0.1 g of conductive carbon black and 2 mL of dimethylformamide, stir evenly, add 2.5 mL of ethylenediamine and the mixed solution, continue to stir for 3.5h, filter, wash and dry to get the aminated conductive carbon black;

[0054] (2) Take 1.5 mL of N,N'-dicyclohexyl carbodiimide, 12 mL of tetrahydrofuran, stir evenly to get a mixed solution; take 0.1 g of conductive graphite, 2 mL of dimethylformamide, stir evenly, add 2.5 mL of ethylenediamine, mixed solution, continue to stir for 3.5 h, filter, wash, dry to get aminoized conductive graphite;

[0055] Step two: 60 kg of aminoized conductive carbon black, 20 kg of aminoized conductive graphite, and 20 kg of modified sodium carboxymethyl cellulose compound are added to a double-planet high-speed dispersion device for high-speed dispersion at a speed of 2500 r / min for 80 minutes at a dispersion temperature of 27℃; 1000 kg of solvent water is added for high-speed dispersion; the speed is 2500 r / min, the dispersion time is 80 minutes, and the dispersion temperature is 27℃;

[0056] Step three: 1 kg of calcium hydroxide crosslinking agent and 300 kg of epoxy butadiene rubber binder with a solid content of 25% are added for high-speed dispersion; the speed is 2500 r / min, the dispersion time is 80 minutes, and the dispersion temperature is 27℃; finally, 10 kg of wetting agent polyethylene glycol is added for high-speed dispersion; the speed is 2500 r / min, the dispersion time is 80 minutes, and the dispersion temperature is 27℃, to obtain the slurry;

[0057] Step four: the slurry is coated on a copper current collector with a thickness of 6 microns and a width of 800 mm by a coating machine, and the single-sided coating density of the nano-coated carbon copper current collector is 1 g / ㎡, then the flame-retardant nano-coated carbon layer is dried by a three-section oven, the drying temperatures of the upper and lower three-section ovens are 60℃, 80℃, and 70℃ respectively, after drying, the coated carbon copper current collector is wound by winding equipment, the unwinding tension is 300 N, the winding tension is 500 N / m, and the nano-coated carbon copper current collector is obtained.

[0058] Example 3: A preparation method of a new type of nano-coated carbon copper current collector special for lithium battery negative electrode, comprising the following steps:

[0059] Step one:

[0060] S1: Preparation of epoxy butadiene rubber binder:

[0061] Take 150 g of butadiene rubber binder and 1500 mL of cyclopentane, stir evenly, then heat to 40℃, add 32 mL of formic acid, 5 g of polyethylene glycol, and 30 mL of hydrogen peroxide, react at 40℃ for 3 hours, wash with distilled water, and dry to obtain the epoxy butadiene rubber binder;

[0062] S2: Preparation of modified sodium carboxymethyl cellulose compound:

[0063] (1) Preparation of metal organic framework material:

[0064] Take 2g of zinc nitrate hexahydrate and 80mL of methanol, stir until uniform, to obtain a mixed solution; take 3.5g of 2-methylimidazole and 80mL of methanol, stir until uniform, add to the mixed solution, stir at 25°C for 22h, increase the temperature to 120°C, react for 10h, wash, precipitate, and dry to obtain the metal organic framework material;

[0065] (2) Preparation of metal organic framework-carboxymethyl cellulose sodium complex:

[0066] Take 0.5g of the metal organic framework material and 50mL of deionized water, ultrasonic dispersion, add 5g of carboxymethyl cellulose sodium, increase the temperature to 60°C, stir for 8h, filter, wash, and dry to obtain the metal organic framework-carboxymethyl cellulose sodium complex;

[0067] (3) Preparation of modified carboxymethyl cellulose sodium complex:

[0068] Take 5g of the metal organic framework-carboxymethyl cellulose sodium complex and 200mL of deionized water, ultrasonic dispersion for 8h to obtain a dispersion liquid; take 1g of epoxidized styrene-butadiene rubber adhesive and 8g of toluene, stir for 5h to obtain an epoxidized styrene-butadiene rubber solution; add the epoxidized styrene-butadiene rubber solution to the dispersion liquid, ultrasonic dispersion for 6h, centrifuge, wash, and dry to obtain the modified carboxymethyl cellulose sodium complex;

[0069] S3: Preparation of aminated conductive carbon black and aminated conductive graphite:

[0070] (1) Take 1.5mL of N,N'-dicyclohexyl carbodiimide and 12mL of tetrahydrofuran, stir until uniform, to obtain a mixed solution; take 0.1g of conductive carbon black and 2mL of dimethylformamide, stir until uniform, add 2.5mL of ethylenediamine and the mixed solution, continue to stir for 3h, suction filter, wash, and dry to obtain the aminated conductive carbon black;

[0071] (2) Take 1.5mL of N,N'-dicyclohexyl carbodiimide and 12mL of tetrahydrofuran, stir until uniform, to obtain a mixed solution; take 0.1g of conductive graphite and 2mL of dimethylformamide, stir until uniform, add 2.5mL of ethylenediamine and the mixed solution, continue to stir for 3h, suction filter, wash, and dry to obtain the aminated conductive graphite;

[0072] Step two: add 60kg of the aminated conductive carbon black, 20kg of the aminated conductive graphite, and 20kg of the modified carboxymethyl cellulose sodium complex to a double-planet high-speed dispersion device for high-speed dispersion, at a rotation speed of 2000r / min, for 100 minutes, and at a dispersion temperature of 45°C; add 1000kg of solvent water for high-speed dispersion, at a rotation speed of 2000r / min, for 100 minutes, and at a dispersion temperature of 45°C;

[0073] Step three: add 1 kg of calcium hydroxide crosslinking agent and 300 kg of epoxy butadiene rubber adhesive with a solid content of 25% for high-speed dispersion; speed 2000 r / min, dispersion time 100 minutes, dispersion temperature 45℃; finally add 10 kg of wetting agent polyethylene glycol for high-speed dispersion; speed 2000 r / min, dispersion time 100 minutes, dispersion temperature 45℃, to obtain the slurry;

[0074] Step four: coat the slurry on a copper current collector with a thickness of 6 microns and a width of 800 mm by a coating machine, and the single-sided coating density of the nano-coated carbon copper current collector is 1 g / m2, then dry the flame-retardant nano-coated carbon layer by passing through three ovens, the drying temperatures of the upper three ovens are 60℃, 80℃ and 70℃ respectively, and the drying temperatures of the lower three ovens are 60℃, 80℃ and 70℃ respectively, after drying, the coated carbon copper current collector is wound by winding equipment, the unwinding tension is 400N, the winding tension is 600N / m, and the nano-coated carbon copper current collector is obtained.

[0075] Example 4: A preparation method of a new type of nano-coated carbon copper current collector special for lithium battery negative electrode, comprising the following steps:

[0076] Step one:

[0077] S1: Preparation of epoxy butadiene rubber adhesive:

[0078] Take 150 g of butadiene rubber adhesive and 1500 mL of cyclopentane, stir uniformly, then heat to 40℃, add 32 mL of formic acid, 5 g of polyethylene glycol, and drop 30 mL of hydrogen peroxide, react at 40℃ for 3 hours, wash with distilled water, dry, and get the epoxy butadiene rubber adhesive;

[0079] S2: Preparation of modified carboxymethyl cellulose sodium complex:

[0080] (1) Preparation of metal organic framework material:

[0081] Take 2 g of zinc nitrate hexahydrate and 80 mL of methanol, stir uniformly to get a mixed solution; take 3.5 g of 2-methylimidazole and 80 mL of methanol, stir uniformly, add the mixed solution, stir at 25℃ for 22h, heat to 120℃, react for 10h, wash, precipitate and dry to get the metal organic framework material;

[0082] (2) Preparation of metal organic framework-carboxymethyl cellulose sodium complex:

[0083] Take 0.5g metal organic framework material, 50mL deionized water, ultrasonic dispersion, add 5g sodium carboxymethyl cellulose, heat to 60℃, stirring for 8h, filtration, washing, drying, to get metal organic framework-sodium carboxymethyl cellulose composite;

[0084] (3) Preparation of modified sodium carboxymethyl cellulose composite:

[0085] Take 5g of metal organic framework-sodium carboxymethyl cellulose composite, 200mL deionized water, ultrasonic dispersion for 10h, to get dispersion liquid; take 1g of epoxidized styrene-butadiene rubber adhesive, 8g of toluene, stirring for 6h, to get epoxidized styrene-butadiene rubber solution; drop the epoxidized styrene-butadiene rubber solution into the dispersion liquid, ultrasonic dispersion for 7h, centrifugal, washing, drying, to get modified sodium carboxymethyl cellulose composite;

[0086] S3: Preparation of aminated conductive carbon black, aminated conductive graphite:

[0087] (1) Take 1.5mL of N,N'-dicyclohexyl carbodiimide, 12mL of tetrahydrofuran, stirring to get mixed solution; take 0.1g of conductive carbon black, 2mL of dimethylformamide, stirring to get mixed solution, add 2.5mL of ethylenediamine, mixed solution, continue stirring for 4h, suction filtration, washing, drying, to get aminated conductive carbon black;

[0088] (2) Take 1.5mL of N,N'-dicyclohexyl carbodiimide, 12mL of tetrahydrofuran, stirring to get mixed solution; take 0.1g of conductive graphite, 2mL of dimethylformamide, stirring to get mixed solution, add 2.5mL of ethylenediamine, mixed solution, continue stirring for 4h, suction filtration, washing, drying, to get aminated conductive graphite;

[0089] Step two: add 60kg of aminated conductive carbon black, 20kg of aminated conductive graphite, 20kg of modified sodium carboxymethyl cellulose composite to the double planetary high-speed dispersion equipment for high-speed dispersion, speed 3000r / min, dispersion time 60 minutes, dispersion temperature 25℃; add 1000kg of solvent water for high-speed dispersion; speed 3000r / min, dispersion time 60 minutes, dispersion temperature 25℃;

[0090] Step three: add 1kg of calcium hydroxide crosslinking agent and 300kg of epoxy styrene-butadiene rubber adhesive with solid content of 25% for high-speed dispersion; speed 3000r / min, dispersion time 60 minutes, dispersion temperature 25℃; finally add 10kg of wetting agent polyethylene glycol for high-speed dispersion; speed 3000r / min, dispersion time 60 minutes, dispersion temperature 25℃, to get slurry;

[0091] Step four: the slurry is coated on a copper current collector with a thickness of 6 microns and a width of 800 mm by a coating machine, the single-sided coating density of the nano-coated carbon copper current collector is 1 g / m2, and then the flame-retardant nano-coated carbon layer is dried by three ovens, the drying temperatures of the upper three ovens are 60°C, 80°C and 70°C respectively, the drying temperatures of the lower three ovens are 60°C, 80°C and 70°C respectively, after drying, the coated carbon copper current collector is wound by winding equipment, the unwinding tension is 300N, the winding tension is 500N / m, and the nano-coated carbon copper current collector is obtained.

[0092] Comparative Example 1:

[0093] Step one: 60 kg of conductive carbon black, 20 kg of conductive graphite and 20 kg of sodium carboxymethyl cellulose are added to a double-planetary high-speed dispersion device for high-speed dispersion, the speed is 2500 r / min, the dispersion time is 60 minutes and the dispersion temperature is 25°C; 1000 kg of solvent water is added for high-speed dispersion; the speed is 2500 r / min, the dispersion time is 60 minutes and the dispersion temperature is 25°C;

[0094] Step two: 1 kg of calcium hydroxide crosslinking agent and 300 kg of polyacrylic acid binder with a solid content of 25% are added for high-speed dispersion; the speed is 2500 r / min, the dispersion time is 60 minutes and the dispersion temperature is 25°C; finally, 10 kg of wetting agent polyethylene glycol is added for high-speed dispersion; the speed is 2500 r / min, the dispersion time is 60 minutes and the dispersion temperature is 25°C, to obtain the slurry;

[0095] Step three: the slurry is coated on a copper current collector with a thickness of 6 microns and a width of 800 mm by a coating machine, and then the flame-retardant nano-coated carbon layer is dried by three ovens, the drying temperatures of the upper three ovens are 60°C, 80°C and 70°C respectively, the drying temperatures of the lower three ovens are 60°C, 80°C and 70°C respectively, after drying, the coated carbon copper current collector is wound by winding equipment, the unwinding tension is 300N, the winding tension is 500N / m, and the nano-coated carbon copper current collector is obtained.

[0096] Comparative Example 2: the metal-organic framework-sodium carboxymethyl cellulose composite is not modified, and the rest is the same as Example 2:

[0097] Step one:

[0098] S1: Preparation of epoxidized styrene-butadiene rubber adhesive:

[0099] Take 150 g of styrene-butadiene rubber adhesive and 1500 mL of cyclopentane, stir uniformly, then heat to 43°C, add 32 mL of formic acid, 5 g of polyethylene glycol, and drop 30 mL of hydrogen peroxide, react at 43°C for 3 hours, wash with distilled water, and dry to obtain the epoxidized styrene-butadiene rubber adhesive;

[0100] S2: Preparation of modified sodium carboxymethyl cellulose complex:

[0101] (1) Preparation of metal-organic framework material:

[0102] Take 2g of zinc nitrate hexahydrate, 80mL of methanol, stir uniformly to obtain a mixed solution; take 3.5g of 2-methylimidazole, 80mL of methanol, stir uniformly, add to the mixed solution, stir at 27℃ for 24h, increase the temperature to 125℃, react for 11h, wash, precipitate, dry to obtain the metal-organic framework material;

[0103] (2) Preparation of metal-organic framework-carboxymethyl cellulose sodium complex:

[0104] Take 0.5g of metal-organic framework material, 50mL of deionized water, ultrasonic dispersion, add 5g of carboxymethyl cellulose sodium, increase the temperature to 63℃, stir for 9h, filter, wash, dry to obtain the metal-organic framework-carboxymethyl cellulose sodium complex;

[0105] S3: Preparation of aminated conductive carbon black and aminated conductive graphite:

[0106] (1) Take 1.5mL of N,N'-dicyclohexyl carbodiimide, 12mL of tetrahydrofuran, stir uniformly to obtain a mixed solution; take 0.1g of conductive carbon black, 2mL of dimethylformamide, stir uniformly, add 2.5mL of ethylenediamine, mixed solution, continue to stir for 3.5h, suction filtration, wash, dry to obtain the aminated conductive carbon black;

[0107] (2) Take 1.5mL of N,N'-dicyclohexyl carbodiimide, 12mL of tetrahydrofuran, stir uniformly to obtain a mixed solution; take 0.1g of conductive graphite, 2mL of dimethylformamide, stir uniformly, add 2.5mL of ethylenediamine, mixed solution, continue to stir for 3.5h, suction filtration, wash, dry to obtain the aminated conductive graphite;

[0108] Step two: add 60kg of aminated conductive carbon black, 20kg of aminated conductive graphite, and 20kg of metal-organic framework-carboxymethyl cellulose sodium complex to a double-planet high-speed dispersion device for high-speed dispersion, the rotation speed is 2500r / min, the dispersion time is 80 minutes, and the dispersion temperature is 27℃; add 1000kg of solvent water for high-speed dispersion; the rotation speed is 2500r / min, the dispersion time is 80 minutes, and the dispersion temperature is 27℃;

[0109] Step three: add 1 kg of calcium hydroxide crosslinking agent and 300 kg of epoxy modified butadiene-styrene rubber binder with a solid content of 25% for high-speed dispersion; speed 2500 r / min, dispersion time 80 min, dispersion temperature 27℃; finally add 10 kg of wetting agent polyethylene glycol for high-speed dispersion; speed 2500 r / min, dispersion time 80 min, dispersion temperature 27℃, to obtain the slurry;

[0110] Step four: coat the slurry on a copper current collector with a thickness of 6 microns and a width of 800 mm by a coating machine, and the single-sided coating density of the nano-coated carbon copper current collector is 1 g / m2, then dry the flame-retardant nano-coated carbon layer by passing through three ovens, the drying temperatures of the upper three ovens are 60℃, 80℃ and 70℃ respectively, and the drying temperatures of the lower three ovens are 60℃, 80℃ and 70℃ respectively, after drying, the coated carbon copper current collector is wound by winding equipment, the unwinding tension is 300N, the winding tension is 500N / m, and the nano-coated carbon copper current collector is obtained.

[0111] Comparative example 3: the butadiene-styrene rubber binder is not modified by epoxidation, and the rest is the same as example 2:

[0112] Step one:

[0113] S1: preparation of modified sodium carboxymethyl cellulose complex:

[0114] (1) Preparation of metal organic framework material:

[0115] Take 2 g of zinc nitrate hexahydrate and 80 mL of methanol, stir evenly to obtain a mixed solution; take 3.5 g of 2-methylimidazole and 80 mL of methanol, stir evenly, add the mixed solution, stir at 27℃ for 24 h, heat to 125℃, react for 11 h, wash, precipitate and dry to obtain the metal organic framework material;

[0116] (2) Preparation of metal organic framework-carboxymethyl cellulose sodium complex:

[0117] Take 0.5 g of metal organic framework material and 50 mL of deionized water, ultrasonic dispersion, add 5 g of carboxymethyl cellulose sodium, heat to 63℃, stir for 9 h, filter, wash and dry to obtain the metal organic framework-carboxymethyl cellulose sodium complex;

[0118] (3) Preparation of modified sodium carboxymethyl cellulose complex:

[0119] Take 5g of metal organic framework-carboxymethyl cellulose sodium complex, 200mL of deionized water, ultrasonic dispersion for 9h, to obtain a dispersion liquid; take 1g of butadiene-styrene rubber adhesive, 8g of toluene, stir for 5.5h, to obtain a butadiene-styrene rubber solution; add the butadiene-styrene rubber solution to the dispersion liquid, ultrasonic dispersion for 6.5h, centrifugal, washing, drying, to obtain a modified carboxymethyl cellulose sodium complex;

[0120] S3: Preparation of amino-conductive carbon black and amino-conductive graphite:

[0121] (1) Take 1.5mL of N,N'-dicyclohexyl carbodiimide, 12mL of tetrahydrofuran, stir uniformly, to obtain a mixed solution; take 0.1g of conductive carbon black, 2mL of dimethylformamide, stir uniformly, add 2.5mL of ethylenediamine, mixed solution, continue to stir for 3.5h, suction filtration, washing, drying, to obtain amino-conductive carbon black;

[0122] (2) Take 1.5mL of N,N'-dicyclohexyl carbodiimide, 12mL of tetrahydrofuran, stir uniformly, to obtain a mixed solution; take 0.1g of conductive graphite, 2mL of dimethylformamide, stir uniformly, add 2.5mL of ethylenediamine, mixed solution, continue to stir for 3.5h, suction filtration, washing, drying, to obtain amino-conductive graphite;

[0123] Step two: add 60kg of amino-conductive carbon black, 20kg of amino-conductive graphite, 20kg of modified carboxymethyl cellulose sodium complex to a double planetary high-speed dispersion device for high-speed dispersion, rotation speed 2500r / min, dispersion time 80 minutes, dispersion temperature 27℃; add 1000kg of solvent water for high-speed dispersion; rotation speed 2500r / min, dispersion time 80 minutes, dispersion temperature 27℃;

[0124] Step three: add 1kg of calcium hydroxide crosslinking agent and 300kg of butadiene-styrene rubber adhesive with solid content of 25% for high-speed dispersion; rotation speed 2500r / min, dispersion time 80 minutes, dispersion temperature 27℃; finally add 10kg of wetting agent polyethylene glycol for high-speed dispersion; rotation speed 2500r / min, dispersion time 80 minutes, dispersion temperature 27℃, to obtain a slurry;

[0125] Step four: coat the slurry on a copper current collector with a thickness of 6 microns and a width of 800mm by a coating machine, the single-sided coating density of the nano-coated carbon copper current collector is 1g / ㎡, then dry the flame-retardant nano-coated carbon layer by a three-section oven, the drying temperatures of the upper three-section oven are 60℃, 80℃ and 70℃ respectively, and the drying temperatures of the lower three-section oven are 60℃, 80℃ and 70℃ respectively, after drying, the coated carbon copper current collector is wound by winding equipment, the unwinding tension is 300N, the winding tension is 500N / m, to obtain a nano-coated carbon copper current collector.

[0126] Experiment:

[0127] The positive electrode slurry (composition of the positive electrode slurry: lithium iron phosphate 95%, polyvinylidene fluoride 2%, conductive carbon black 3%, N-methyl pyrrolidone as a solvent, and a total solid content of 50%) was coated on the surface of the nano-coated carbon copper current collector prepared in Example 1-Example 4 and Comparative Example 1-Comparative Example 3, dried, and then rolled to prepare a pole piece; the performance thereof was tested, and the carbon-coated aluminum foil current collector was tested for peeling strength using a peeling force tester. The nano-coated carbon copper current collector was made into a battery, which was charged at a constant current of 20C to 3.65V, then charged at a constant voltage, the cutoff current was 0.05C, and was left for 15 min, then discharged at 20C to 2.5V, the current range was 5-30A, the charge-discharge capacity retention rate at 20C was tested, and the data obtained are shown in the following table:

[0128] Conclusion: In Example 1, carboxymethyl cellulose sodium CMC is added to disperse the conductive agent, and the hardness of the butadiene-styrene rubber binder SBR is slightly soft, which improves the adhesion to the lithium battery negative electrode, improves the peeling force between the lithium battery negative pole piece and the nano-coated carbon copper current collector, and solves the problem of pole piece powdering during battery manufacturing, which causes the battery to have poor electrical performance and low service life. Compared with Comparative Example 1 and Example 1, polyacrylic acid is used as a binder, the adhesion is poor, and the battery cycle life is also reduced. In Example 2 to Example 4, carboxymethyl cellulose sodium and metal-organic framework materials are loaded together, and then the epoxy butadiene-styrene rubber is coated outside the metal-organic framework-carboxymethyl cellulose sodium composite, which improves the compatibility of the metal-organic framework-carboxymethyl cellulose sodium composite in the slurry and further improves the adhesion to the lithium battery negative electrode. The conductive carbon black and conductive graphite are subjected to amino modification, the amino groups thereon can react with the epoxy groups in the epoxy butadiene-styrene rubber binder, which makes the conductive carbon black and conductive graphite better dispersed, improves the peeling force between the lithium battery negative pole piece and the nano-coated carbon copper current collector, and further improves the battery life. In Comparative Example 2, the metal-organic framework-carboxymethyl cellulose sodium composite is not modified, and no epoxy butadiene-styrene rubber is coated outside, which reduces the compatibility of the metal-organic framework-carboxymethyl cellulose sodium composite in the slurry, affects the peeling strength and battery cycle life. In Comparative Example 3, the butadiene-styrene rubber binder is not modified by epoxy, which reduces the dispersibility of the filler, and the adhesion and battery cycle life of Comparative Example 4 are reduced compared with Example 2 to Example 4.

[0129] Finally, it should be noted that the above only describes optional embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, modifications or equivalent replacements to the technical solutions described in the foregoing embodiments can still be made by those skilled in the art. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A nano-carbon-coated copper current collector for lithium battery negative electrode, wherein: The nano-carbon-coated copper current collector comprises a copper current collector and a conductive layer coated on at least one side surface of the copper current collector.

2. The nano-carbon-coated copper current collector for lithium battery negative electrode according to claim 1, wherein: The conductive layer is coated with a slurry made of a carbon conductive material, sodium carboxymethyl cellulose, a crosslinking agent, a styrene-butadiene rubber binder, a wetting agent, and a solvent, and then baked; the mass ratio of the carbon conductive material, sodium carboxymethyl cellulose, the crosslinking agent, the styrene-butadiene rubber binder, the wetting agent, and the solvent is (1.1-1.5): (0.1-0.5): (0.01-0.05): (1-2): (0.01-0.05): (10-20); the carbon conductive material is any one or more of conductive carbon black, conductive graphite, graphene, and carbon nanotubes; the crosslinking agent is any one or more of sodium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide.

3. The nano-carbon-coated copper current collector for lithium battery negative electrode according to claim 1, wherein: The conductive layer is obtained by coating and baking the slurry, and the preparation method of the slurry includes the following steps: Step 1: Disperse the carbon conductive material and sodium carboxymethyl cellulose at a temperature of 25-45°C and a rotation speed of 2000-3000 r / min for 60-100 minutes; add a solvent and disperse at high speed for 60-100 minutes; Step 2: Add a crosslinking agent and a binder and disperse them at a temperature of 25-45°C and a rotation speed of 2000-3000 r / min for 60-100 minutes; finally, add a wetting agent and disperse at high speed to obtain a slurry.

4. The nano-carbon-coated copper current collector for lithium battery negative electrode according to claim 3, wherein: The nano-carbon-coated copper current collector for lithium battery negative electrode meets any one or more of the following conditions: (1) The carbon conductive material is any one or more of conductive carbon black, conductive graphite, graphene, and carbon nanotubes; (2) The cross-linking agent is any one or more of sodium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide.

5. The nano-carbon-coated copper current collector for lithium battery negative electrode according to claim 4, wherein: The preparation method of the nano carbon-coated copper current collector comprises the following steps: S1: Disperse conductive carbon black, conductive graphite, and sodium carboxymethyl cellulose at a temperature of 25-45°C and a rotation speed of 2000-3000 r / min for 60-100 minutes, add a solvent and disperse at high speed to obtain a mixed solution; S2: adding a cross-linking agent and a styrene-butadiene rubber binder and dispersing them at high speed, and finally adding a wetting agent and dispersing them at high speed to obtain a slurry; S3: coating the upper and lower surfaces of the copper current collector with slurry, baking, and rolling to obtain a nano-carbon-coated copper current collector.

6. The nano-carbon-coated copper current collector for lithium battery negative electrode according to claim 5, wherein: The mass ratio of the conductive carbon black, conductive graphite, sodium carboxymethyl cellulose, crosslinking agent, styrene-butadiene rubber binder, wetting agent and solvent is 1: (0.1-0.5): (0.1-0.5): (0.01-0.05): (1-2): (0.01-0.05): (10-20).

7. The nano-carbon-coated copper current collector for lithium battery negative electrode according to claim 6, wherein: The sodium carboxymethyl cellulose is a modified sodium carboxymethyl cellulose complex, and its preparation method comprises the following steps: Step A: Take a metal organic framework material and deionized water, ultrasonically disperse them, add sodium carboxymethyl cellulose, heat to 60-65°C, stir for 8-10 hours, filter, wash, and dry to obtain a metal organic framework-sodium carboxymethyl cellulose complex; Step B: taking a metal organic framework-sodium carboxymethyl cellulose complex and deionized water, ultrasonically dispersing for 8-10 hours to obtain a dispersion; taking a styrene butadiene rubber binder and toluene, stirring for 5-6 hours to obtain a styrene butadiene rubber solution; adding the epoxidized styrene butadiene rubber solution dropwise to the dispersion, ultrasonically dispersing for 6-7 hours, centrifuging, washing, and drying to obtain a modified sodium carboxymethyl cellulose complex.

8. A nano-carbon-coated copper current collector for lithium battery negative electrode according to any one of claims 6 to 7, wherein: The styrene-butadiene rubber binder is an epoxidized styrene-butadiene rubber binder, and its preparation method is as follows: taking the styrene-butadiene rubber binder and cyclopentane, stirring evenly, then heating to 40-45° C., adding formic acid and polyethylene glycol, dripping hydrogen peroxide, reacting at 40-45° C. for 3-3.5 hours, washing with distilled water, and drying to obtain the epoxidized styrene-butadiene rubber binder.

9. The nano-carbon-coated copper current collector for lithium battery negative electrode according to claim 8, wherein: The preparation method of the metal organic framework material comprises: taking zinc nitrate hexahydrate and methanol, stirring evenly to obtain a mixed solution; taking 2-methylimidazole and methanol, stirring evenly, adding the mixed solution, stirring at 25-30° C. for 22-26 hours, heating to 120-130° C., reacting for 10-12 hours, washing, precipitating, and drying to obtain the metal organic framework material.

10. The nano-carbon-coated copper current collector for lithium battery negative electrode according to claim 9, wherein: The following conditions are met: the carbon conductive material is an amino carbon conductive material, and the preparation method of the amino carbon conductive material is: take N,N'-dicyclohexylcarbodiimide and tetrahydrofuran, stir evenly to obtain a mixed solution; take the carbon conductive material and dimethylformamide, stir evenly, add ethylenediamine and the mixed solution, continue stirring for 3-4 hours, filter, wash, and dry to obtain the amino carbon conductive material.

Images