High-compaction-resistant NANO carbon-coated aluminum current collector

Abstract

A high-compaction-resistant nano carbon-coated aluminum current collector, relating to the technical field of current collectors of batteries.The nano carbon-coated aluminum current collector comprises an aluminum current collector and mesh-shaped conductive layers respectively coated on the upper and lower surfaces of the aluminum current collector, wherein the mesh-shaped conductive layers each are formed by slurry coating and baking, and a slurry comprises a conductive material, a binder, nanocellulose, a cross-linking agent, a solvent, and a wetting agent. Through the design of a slurry formulation and an aluminum current collector coating, a layer of mesh-shaped structure is formed in a nano conductive coating, such that the effect of conductive particles on pinholes of an aluminum current collector is reduced, and a nano carbon-coated aluminum current collector can withstand higher compaction density of active materials, thereby reducing the frequency of aluminum foil breakage, improving the energy density of a battery.

Description

A nano-carbon-coated aluminum current collector resistant to high pressure compaction Technical Field

[0001] The present application relates to the technical field of battery current collectors, for example, a high-pressure compaction-resistant nano-carbon-coated aluminum current collector. Background Art

[0002] At present, there are many pinhole defects on the surface of traditional aluminum current collectors or composite aluminum current collectors. Conventional nano-carbon-coated aluminum current collectors are made into battery pole pieces after being coated with active materials, and need to be rolled. Due to the presence of pinholes on the surface of the current collector, and the conventional nano-conductive materials on the surface of the aluminum current collector are mainly composed of granular conductive materials, these granular conductive materials will be embedded in the pinholes on the surface of the aluminum current collector during the rolling process of the pole piece. Especially under the design of high compaction of the positive active material, the inside of the pinhole is squeezed, resulting in tearing on the surface of the aluminum current collector. Under the action of tensile tension, the pole piece will break abnormally, resulting in the loss of raw materials and production efficiency. At the same time, it also limits the design of high compaction of the active material, resulting in the inability to further improve the related energy density. Summary of the Invention

[0003] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0004] The present application provides a high-pressure compaction-resistant nano-carbon-coated aluminum current collector to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, this application provides the following technical solutions:

[0006] A high-pressure compaction-resistant nano-carbon-coated aluminum current collector comprises an aluminum current collector and mesh-shaped conductive layers respectively coated on the upper and lower surfaces of the aluminum current collector.

[0007] In this application, high compaction refers to the fact that when preparing a positive electrode sheet, the compaction density of the positive electrode active material layer on the surface of the carbon-coated aluminum current collector reaches a certain value, and the electrode sheet can be considered as a high compaction electrode sheet. For different positive electrode active material systems, this value is different: for example, for a ternary positive electrode material, the compaction density is 3.6g / cm 3 For high compaction; for lithium iron phosphate material, the compaction density reaches 2.8g / cm 3 For high compaction; for lithium manganese iron phosphate material, the compaction density reaches 2.4g / cm 3 The high compaction resistance means that when the compaction density of the positive electrode active material layer reaches the above value, the carbon-coated aluminum current collector can still maintain stable structure and performance and ensure normal conductive function.

[0008] Furthermore, the mesh-shaped conductive layer is formed by coating and baking a slurry, and the slurry includes a conductive material, a binder, nanocellulose, a cross-linking agent, a solvent and a wetting agent.

[0009] Furthermore, the thickness of the nano carbon-coated aluminum current collector is 4-25 μm, and the coating surface density of any side of the mesh conductive layer is 0.1-2.0 g / m 2 .

[0010] In the above technical solution, the thickness range of the nano-carbon-coated aluminum current collector is limited to 4-25μm. If it is less than 4μm, the mechanical strength of the nano-carbon-coated aluminum current collector will be reduced, and it will be easy to break, which cannot meet the process requirements of lithium battery electrode manufacturing; if it is greater than 25μm, the thickness of the nano-carbon-coated aluminum current collector will be too large, resulting in excessive internal space occupation, affecting the energy density of the battery; if the single-sided coating surface density is less than 0.1g / m 2 , double-sided coating surface density <0.2g / m 2 , it cannot effectively improve the interface resistance between the positive electrode active material and the aluminum current collector; if the single-sided coating surface density is greater than 2.0g / m 2 , double-sided coating surface density> 4.0g / m 2 , will result in excessively high costs for the conductive coating.

[0011] Furthermore, the aluminum current collector includes an aluminum foil current collector and a composite aluminum current collector, wherein the specifications of the aluminum foil current collector include double-sided smooth aluminum foil and single-sided smooth aluminum foil, and the brand is one of 1100, 1060, 1235, and 1070 of H18; the material of the composite current collector is a mixture of one or more of PET (polyethylene terephthalate), PP (polypropylene), PI (polyimide), and PTFE (polytetrafluoroethylene).

[0012] Furthermore, the conductive material is a mixture of one or more of conductive carbon black, conductive graphite, graphene, and carbon nanotubes.

[0013] Furthermore, the binder is a mixture of one or more of PAA (polyacrylic acid), PMMA (polymethyl methacrylate), PVDF (polyvinylidene fluoride), and PTFE (polytetrafluoroethylene).

[0014] Furthermore, the cross-linking agent is a mixture of one or more of sodium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide.

[0015] Furthermore, the wetting agent is a mixture of one or more of alcohols, ketones, and ethers, wherein the alcohol can be isopropyl alcohol, the ketone can be acetone, and the ether can be tetrahydrofuran.

[0016] Furthermore, the solvent is deionized water.

[0017] A method for preparing a high-pressure compaction-resistant nano-carbon-coated aluminum current collector comprises the following steps:

[0018] Step S1: mixing conductive carbon black, conductive graphite, and nanocellulose, and dispersing them at high speed to obtain a mixture;

[0019] Step S2: adding a solvent and performing high-speed dispersion to obtain a mixed solution;

[0020] Step S3: adding a crosslinking agent and a binder, and performing high-speed dispersion; then adding a wetting agent, and performing high-speed dispersion to obtain a slurry;

[0021] Step S4: coating the upper and lower surfaces of the aluminum current collector with the slurry, baking and rolling to form a mesh-shaped conductive layer, thereby obtaining a nano-carbon-coated aluminum current collector.

[0022] Furthermore, the process conditions for high-speed dispersion are: rotation speed 2000-3000 r / min, dispersion time 60-100 min, and dispersion temperature 20-45°C.

[0023] Furthermore, the coating process conditions in step S4 are: a coating speed of 60-100 m / min.

[0024] Furthermore, the baking process conditions in step S4 are as follows: the drying is divided into three stages: the temperature of the first stage is 55-65°C, and the time is 1-40S; the temperature of the second stage is 75-85°C, and the time is 1-40S; the temperature of the third stage is 65-75°C, and the time is 1-40S.

[0025] Furthermore, the winding process conditions in step S4 are: unwinding tension 200-500N, and winding tension 300-1000N.

[0026] Furthermore, in step S3, the slurry is composed of conductive carbon black, conductive graphite, nanocellulose, a crosslinking agent, a binder, a wetting agent and a solvent in a mass ratio of 1: (0.1-0.5): (0.1-0.5): (0.01-0.05): (1-6): (0.01-0.20): (10-18).

[0027] Furthermore, the conductive carbon black and conductive graphite are surface modified by the following process:

[0028] Conductive carbon black and conductive graphite are respectively mixed evenly with N-aminoethyl-3-aminopropylmethyldimethoxysilane and ethanol, heated to 40-50° C., reacted for 5-6 hours, and washed and dried to obtain modified conductive carbon black and modified conductive graphite.

[0029] Furthermore, the mass ratio of the conductive carbon black to N-aminoethyl-3-aminopropylmethyldimethoxysilane and ethanol is 1:(0.2-0.4):(6-8).

[0030] Furthermore, the mass ratio of the conductive graphite to N-aminoethyl-3-aminopropylmethyldimethoxysilane and ethanol is 1:(0.2-0.4):(6-8).

[0031] Furthermore, the nanocellulose is modified, and the specific modification process is as follows:

[0032] Step (1): Under nitrogen protection, 1,1,1-tris(4-hydroxyphenyl)ethane triglycidyl ether, 2,2'-diallylbisphenol A and tetrabutylammonium bromide are uniformly mixed, the mixture is heated to 75-85° C., reacted for 22-24 hours, cooled to room temperature, filtered, washed and dried to obtain a hyperbranched polymer;

[0033] Step (2): mixing the nanocellulose, anhydrous ethanol and deionized water, performing ultrasonic treatment for 10-30 minutes, heating to 40-50° C., adding 3-mercaptopropyltriethoxysilane, reacting for 8-10 hours, centrifuging, washing and drying to obtain thiolated nanocellulose;

[0034] Step (3): uniformly mixing the hyperbranched polymer, thiolated nanocellulose and N,N-dimethylformamide, adding a photoinitiator, irradiating with ultraviolet light, filtering, washing and freeze-drying to obtain modified nanocellulose.

[0035] In the above technical solution, 1,1,1-tris(4-hydroxyphenyl)ethane triglycidyl ether and 2,2'-diallylbisphenol A are reacted to obtain a hyperbranched polymer containing epoxy groups and allyl groups; 3-mercaptopropyltriethoxysilane is used to modify the surface of nanocellulose to introduce mercapto groups to obtain thiol-modified nanocellulose; a mercapto-ene click reaction is carried out between the double bonds in the hyperbranched polymer and the mercapto groups to obtain modified nanocellulose; and the modified nanocellulose contains epoxy groups, which can also be grafted with amino groups in modified conductive carbon black and modified conductive graphite, further enhancing the interfacial bonding between the nanocellulose and the conductive carbon black and conductive graphite, thereby helping to improve the conductive properties and mechanical properties of the slurry.

[0036] Furthermore, in step (1), the mass ratio of 1,1,1-tris(4-hydroxyphenyl)ethane triglycidyl ether to 2,2'-diallylbisphenol A and tetrabutylammonium bromide is 1:(1.0-1.5):(0.01-0.03).

[0037] Furthermore, in step (2), the mass ratio of nanocellulose to anhydrous ethanol and deionized water is 1: (100-120): (20-25).

[0038] Furthermore, in step (2), the mass of 3-mercaptopropyltriethoxysilane is 0.2-0.4 times the mass of nanocellulose.

[0039] Furthermore, in step (3), the mass ratio of the hyperbranched polymer, the thiolated nanocellulose and the N,N-dimethylformamide is 1:(1.0-1.2):(8-10).

[0040] Furthermore, in step (3), the photoinitiator is 2-hydroxy-2-methylpropiophenone, and its amount is 1-3% of the mass of the hyperbranched polymer.

[0041] Furthermore, the process conditions of ultraviolet irradiation in step (3) are: irradiation with 360-380nm ultraviolet light for 6-8h, irradiation intensity of 20-25mW / cm 2 .

[0042] Compared with the related art, the beneficial effects of this application are as follows:

[0043] 1. The present application discloses a high-pressure compaction-resistant nano-carbon-coated aluminum current collector. By designing the slurry formula and the aluminum current collector coating, the nano-conductive coating forms a mesh structure, which reduces the influence of the conductive particles on the pinholes of the aluminum current collector. The nano-carbon-coated aluminum current collector can withstand a higher compaction density of the active material and reduce the frequency of aluminum band breakage.

[0044] 2. The present application discloses a high-pressure compaction-resistant nano-carbon-coated aluminum current collector, which improves the energy density of the battery by increasing the active material compaction density of the nano-carbon-coated aluminum current collector; the MD tensile strength of the nano-carbon-coated aluminum current collector prepared by the present application is greater than 150MPa, the TD tensile strength is greater than 120MPa, the MD elongation is greater than 2%, and the TD elongation is greater than 1%; the surface resistance is less than 10mΩ; if its MD tensile strength is less than 150MPa, the TD tensile strength is less than 120MPa, the MD elongation is less than 2%, and the TD elongation is less than 1%, then the mechanical strength of the nano-carbon-coated aluminum current collector is low, and it is prone to band breakage, which cannot meet the process requirements of lithium battery electrode manufacturing; if its surface resistance is greater than 10mΩ, it cannot effectively improve the interface resistance between the positive electrode active material and the aluminum current collector.

[0045] 3. A high-pressure compaction-resistant nano-carbon-coated aluminum current collector of the present application is prepared by reacting 1,1,1-tris(4-hydroxyphenyl)ethane triglycidyl ether and 2,2'-diallylbisphenol A to obtain a hyperbranched polymer containing epoxy groups and allyl groups, which has the characteristics of multiple branches and complex structure and can improve the toughness and strength of the material; 3-mercaptopropyltriethoxysilane is used to modify the surface of nanocellulose to introduce mercapto groups to obtain mercaptolated nanocellulose; a mercapto-ene click reaction is carried out between the double bonds in the hyperbranched polymer and the mercapto groups to obtain modified nanocellulose; at the same time, the modified nanocellulose contains epoxy groups, which can also be grafted with amino groups in modified conductive carbon black and modified conductive graphite, further enhancing the interfacial bonding between nanocellulose and conductive carbon black and conductive graphite, and helping to improve the conductive properties and mechanical properties of the slurry.

[0046] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings:

[0048] FIG1 is a schematic structural diagram of a high-pressure compaction-resistant nano-carbon-coated aluminum current collector in an embodiment of the present application. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0050] It should be noted that there are no special restrictions on the purchase manufacturers of all raw materials involved in this application, and they include, by way of example: conductive carbon black: Cabot VXC72R, particle size 30 nm, which can be purchased from Guangzhou Jingyi New Materials Co., Ltd.; conductive graphite: brand TIMREX KS 6, manufacturer IMERYS; nanocellulose: cellulose nanocrystals, particle size 10 nm, which can be purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; aluminum current collector: double-sided smooth aluminum foil, brand H18-1100, thickness 13 μm, width 800 mm, which can be purchased from Shenzhen Honglei Metal Materials Co., Ltd.; polyacrylic acid binder: solid content 25%, which can be purchased from Wuhan Proloff Biotechnology Co., Ltd.

[0051] Example 1: A method for preparing a high-pressure compaction-resistant nano-carbon-coated aluminum current collector, comprising the following steps:

[0052] Step S1: 60 kg of conductive carbon black, 20 kg of conductive graphite, and 20 kg of nanocellulose are added to a dual planetary high-speed dispersing device, and dispersed at a speed of 2500 r / min, a dispersion time of 60 min, and a dispersion temperature of 25° C. to obtain a mixture;

[0053] Step S2: using deionized water as a solvent, adding 1000 kg of deionized water, and performing high-speed dispersion at a speed of 2500 r / min, a dispersion time of 60 min, and a dispersion temperature of 25° C. to obtain a mixed solution;

[0054] Step S3: using calcium hydroxide as a cross-linking agent, polyacrylic acid with a solid content of 25% as a binder, and isopropyl alcohol as a wetting agent; adding 1 kg of calcium hydroxide and 300 kg of polyacrylic acid with a solid content of 25%, and performing high-speed dispersion at a speed of 2500 r / min, a dispersion time of 60 minutes, and a dispersion temperature of 25° C.; then adding 10 kg of isopropyl alcohol, and performing high-speed dispersion at a speed of 2500 r / min, a dispersion time of 60 minutes, and a dispersion temperature of 25° C. to obtain a slurry;

[0055] Step S4: The slurry is coated on the upper and lower surfaces of the aluminum current collector through a coating machine (coating speed is 80m / min), and then dried in an oven. The temperature of the first stage is 60°C and the time is 3s; the temperature of the second stage oven is 80°C and the time is 3s; the temperature of the third stage is 70°C and the time is 3s; after winding (unwinding tension is 300N, winding tension is 500N), a nano-carbon-coated aluminum current collector is obtained.

[0056] Example 2: A method for preparing a high-pressure compaction-resistant nano-carbon-coated aluminum current collector, comprising the following steps:

[0057] Step S1: 50 kg of conductive carbon black, 25 kg of conductive graphite, and 25 kg of nanocellulose were added to a dual planetary high-speed dispersing device and dispersed at a speed of 2000 r / min, a dispersing time of 100 min, and a dispersing temperature of 20° C. to obtain a mixture;

[0058] Step S2: using deionized water as a solvent, adding 750 kg of deionized water, and performing high-speed dispersion at a speed of 2000 r / min, a dispersion time of 100 min, and a dispersion temperature of 20° C. to obtain a mixed solution;

[0059] Step S3: using calcium hydroxide as a cross-linking agent, polyacrylic acid with a solid content of 25% as a binder, and isopropyl alcohol as a wetting agent; adding 2.5 kg of calcium hydroxide and 100 kg of polyacrylic acid with a solid content of 25%, and performing high-speed dispersion at a speed of 2000 r / min, a dispersion time of 100 minutes, and a dispersion temperature of 20° C.; then adding 2.5 kg of isopropyl alcohol, and performing high-speed dispersion at a speed of 2000 r / min, a dispersion time of 100 minutes, and a dispersion temperature of 45° C. to obtain a slurry;

[0060] Step S4: The slurry is coated on the upper and lower surfaces of the aluminum current collector by a coating machine (coating speed is 70m / min), and then dried in an oven. The first stage temperature is 55°C and the time is 40s; the second stage temperature is 75°C and the time is 40s; the third stage temperature is 65°C and the time is 40s; after winding (unwinding tension is 200N and winding tension is 300N), a nano-carbon-coated aluminum current collector is obtained;

[0061] Conductive carbon black and conductive graphite are surface modified by the following process:

[0062] 50 kg of conductive carbon black was mixed evenly with 10 kg of N-aminoethyl-3-aminopropylmethyldimethoxysilane and 300 kg of ethanol, and the mixture was heated to 40°C and reacted for 5 hours. After washing and drying, the modified conductive carbon black was obtained.

[0063] 25 kg of conductive graphite, 5 kg of N-aminoethyl-3-aminopropylmethyldimethoxysilane and 150 kg of ethanol were mixed evenly, heated to 40 ° C, reacted for 5 hours, washed and dried to obtain modified conductive graphite;

[0064] Nanocellulose is modified by the following process:

[0065] Step (1): Under nitrogen protection, 25 kg of 1,1,1-tris(4-hydroxyphenyl)ethane triglycidyl ether, 25 kg of 2,2'-diallyl bisphenol A, and 0.25 kg of tetrabutylammonium bromide were mixed uniformly, heated to 75° C., reacted for 22 hours, cooled to room temperature, filtered, washed, and dried to obtain a hyperbranched polymer;

[0066] Step (2): 25 kg of nanocellulose, 2500 kg of anhydrous ethanol, and 500 kg of deionized water were mixed uniformly, ultrasonically treated for 30 minutes, heated to 50° C., 5 kg of 3-mercaptopropyltriethoxysilane was added, reacted for 8 hours, and centrifuged, washed, and dried to obtain thiolated nanocellulose;

[0067] Step (3): 25 kg of hyperbranched polymer, 25 kg of thiolated nanocellulose and 200 kg of N, N-dimethylformamide were mixed evenly, 0.25 kg of photoinitiator was added, and the mixture was irradiated with 360 nm ultraviolet light for 6 h at an irradiation intensity of 20 mW / cm 2 , and after filtration, washing, and freeze-drying, modified nanocellulose was obtained.

[0068] Example 3: A method for preparing a high-pressure compaction-resistant nano-carbon-coated aluminum current collector, comprising the following steps:

[0069] Step S1: 60 kg of conductive carbon black, 6 kg of conductive graphite, and 6 kg of nanocellulose were mixed and dispersed at high speed at a speed of 3000 r / min, a dispersion time of 60 min, and a dispersion temperature of 45° C. to obtain a mixture;

[0070] Step S2: using deionized water as a solvent, adding 600 kg of deionized water, and performing high-speed dispersion at a speed of 3000 r / min, a dispersion time of 60 min, and a dispersion temperature of 45° C. to obtain a mixed solution;

[0071] Step S3: using calcium hydroxide as a cross-linking agent, polyacrylic acid with a solid content of 25% as a binder, and isopropyl alcohol as a wetting agent; adding 0.6 kg of calcium hydroxide and 60 kg of polyacrylic acid with a solid content of 25%, and performing high-speed dispersion at a speed of 3000 r / min, a dispersion time of 60 minutes, and a dispersion temperature of 45° C.; then adding 0.6 kg of isopropyl alcohol, and performing high-speed dispersion at a speed of 3000 r / min, a dispersion time of 60 minutes, and a dispersion temperature of 45° C. to obtain a slurry;

[0072] Step S4: The slurry is coated on the upper and lower surfaces of the aluminum current collector by a coating machine (coating speed is 100m / min), and then dried in an oven. The first stage temperature is 65°C and the time is 1s; the second stage temperature is 85°C and the time is 20s; the third stage temperature is 75°C and the time is 1s; after winding (unwinding tension is 500N and winding tension is 1000N), a nano-carbon-coated aluminum current collector is obtained;

[0073] Conductive carbon black and conductive graphite are surface modified by the following process:

[0074] 60 kg of conductive carbon black, 12 kg of N-aminoethyl-3-aminopropylmethyldimethoxysilane and 360 kg of ethanol were mixed evenly, heated to 50°C, reacted for 6 hours, washed and dried to obtain modified conductive carbon black;

[0075] 6 kg of conductive graphite was mixed evenly with 1.2 kg of N-aminoethyl-3-aminopropylmethyldimethoxysilane and 36 kg of ethanol, and the mixture was heated to 50°C and reacted for 6 hours. After washing and drying, modified conductive graphite was obtained.

[0076] Nanocellulose is modified by the following process:

[0077] Step (1): Under nitrogen protection, 5 kg of 1,1,1-tris(4-hydroxyphenyl)ethane triglycidyl ether, 7.5 kg of 2,2'-diallyl bisphenol A, and 0.15 kg of tetrabutylammonium bromide were mixed uniformly, heated to 85° C., reacted for 24 hours, cooled to room temperature, filtered, washed, and dried to obtain a hyperbranched polymer;

[0078] Step (2): 6 kg of nanocellulose, 720 kg of anhydrous ethanol, and 150 kg of deionized water were mixed uniformly, ultrasonically treated for 10 minutes, heated to 50° C., 2.4 kg of 3-mercaptopropyltriethoxysilane was added, reacted for 10 hours, and centrifuged, washed, and dried to obtain thiolated nanocellulose;

[0079] Step (3): 5 kg of hyperbranched polymer, 6 kg of thiolated nanocellulose and 50 kg of N, N-dimethylformamide were mixed evenly, 0.15 kg of photoinitiator was added, and the mixture was irradiated with 380 nm ultraviolet light for 8 h at an irradiation intensity of 25 mW / cm 2 , and after filtration, washing, and freeze-drying, modified nanocellulose was obtained.

[0080] Comparative Example 1: A method for preparing a nano-carbon-coated aluminum current collector, comprising the following processes:

[0081] Compared with Example 1, Comparative Example 1 does not add nanocellulose; other steps are the same as Example 1.

[0082] Comparative Example 2: A method for preparing a nano-carbon-coated aluminum current collector, comprising the following processes:

[0083] Nanocellulose is modified by the following process:

[0084] Step (1): Under nitrogen protection, 5 kg of 1,1,1-tris(4-hydroxyphenyl)ethane triglycidyl ether, 7.5 kg of 2,2'-diallyl bisphenol A, and 0.15 kg of tetrabutylammonium bromide were mixed uniformly, heated to 85° C., reacted for 24 hours, cooled to room temperature, filtered, washed, and dried to obtain a hyperbranched polymer;

[0085] Step (2): 6 kg of nanocellulose, 720 kg of anhydrous ethanol, and 150 kg of deionized water were mixed uniformly, ultrasonically treated for 10 minutes, heated to 50° C., 2.4 kg of 3-mercaptopropyltriethoxysilane was added, reacted for 10 hours, and centrifuged, washed, and dried to obtain thiolated nanocellulose;

[0086] Step (3): 5 kg of hyperbranched polymer, 1.5 kg of thiolated nanocellulose and 50 kg of N, N-dimethylformamide were mixed evenly, 0.15 kg of photoinitiator was added, and the mixture was irradiated with 380 nm ultraviolet light for 8 h at an irradiation intensity of 25 mW / cm 2 , after filtering, washing and freeze-drying, the modified nanocellulose is obtained;

[0087] Compared with Example 3, the mass ratio of the hyperbranched polymer to the thiolated nanocellulose in step (3) of Comparative Example 2 is 1:0.3; the other steps are the same as those in Example 3.

[0088] Comparative Example 3: A method for preparing a nano-carbon-coated aluminum current collector, comprising the following processes:

[0089] Nanocellulose is modified by the following process:

[0090] 6 kg of nanocellulose, 720 kg of anhydrous ethanol, and 150 kg of deionized water were mixed evenly, ultrasonically treated for 10 minutes, heated to 50°C, and 2.4 kg of 3-mercaptopropyltriethoxysilane was added. The mixture was reacted for 10 hours, and the mixture was centrifuged, washed, and dried to obtain thiolated nanocellulose.

[0091] Compared with Example 3, no hyperbranched polymer was added in Comparative Example 3, and other steps were the same as those in Example 3.

[0092] Comparative Example 4: A method for preparing a nano-carbon-coated aluminum current collector, comprising the following processes:

[0093] Compared with Example 1, the mass ratio of conductive carbon black, conductive graphite and nanocellulose in Comparative Example 4 is 1:1:2; other steps are the same as those in Example 1.

[0094] Comparative Example 5: A method for preparing a nano-carbon-coated aluminum current collector, comprising the following processes:

[0095] Compared with Example 1, the mass ratio of conductive carbon black, conductive graphite and nanocellulose in Comparative Example 5 is 1:0.05:0.05; other steps are the same as in Example 1.

[0096] Experiment: A positive electrode slurry was coated on the surface of the nano-carbon-coated aluminum current collector prepared in Examples 1-3 and Comparative Examples 1-3 (the composition of the positive electrode slurry was: 95% lithium iron phosphate, 2% polyvinylidene fluoride, 3% conductive carbon black, N-methylpyrrolidone as solvent, and the total solid content was 50%). After drying, the dried samples were roll-pressed to obtain electrode sheets. The performance of each electrode was tested and the test results were recorded:

[0097] Experiment 1: Belt breakage test: Ensure the compaction density (ratio of lithium iron phosphate mass to volume) is 2.6g / cm 3Under the conditions of , the pole piece is rolled and the number of belt breaks is recorded.

[0098] Experiment 2: Extreme compaction test: The electrode is rolled using different rolling pressures and then bent. When the active material layer does not break brittlely, the maximum compaction density of the sample is calculated.

[0099] Test results:

[0100] According to the data in the above table, we can clearly draw the following conclusions:

[0101] 1. Compared with Examples 1-3, the number of band breaks of the product obtained in Comparative Example 1 increased and the ultimate compaction decreased, indicating that the addition of nanocellulose in the present application can synergistically construct a conductive network with conductive carbon black and conductive graphite, thereby enabling the nano-carbon-coated aluminum current collector to withstand a higher compaction density of the active substance, thereby reducing the frequency of band breaks of aluminum; the number of band breaks of the products obtained in Comparative Examples 4 and 5 increased and the ultimate compaction decreased, indicating that the performance of the nano-carbon-coated aluminum current collector prepared in the present application is affected by the composition ratio thereof. By selecting a composition ratio within the said range, a nano-carbon-coated aluminum current collector that can withstand a higher compaction density of the active substance can be prepared and the frequency of band breaks of aluminum can be reduced.

[0102] 2. Compared with Examples 1-3, the ultimate compaction of the product obtained in Comparative Example 2 decreases, which indicates that the performance of the modified nanocellulose prepared in the present application is affected by the ratio of each reagent in its preparation process. By selecting a mass ratio within the said range, the prepared nanocellulose has excellent toughness and mechanical properties, thereby enhancing the compaction effect of the nano-carbon-coated aluminum current collector.

[0103] 3. Compared with Examples 1-3, the ultimate compaction of the product obtained in Comparative Example 3 is reduced, which shows that the addition of hyperbranched polymer in this application can improve the toughness and mechanical properties of the modified nanocellulose.

[0104] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprise," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0105] Finally, it should be noted that the above descriptions are merely optional embodiments of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A high-pressure compaction-resistant nano-carbon-coated aluminum current collector, comprising an aluminum current collector and a mesh-shaped conductive layer coated on the upper and lower surfaces of the aluminum current collector, respectively.

2. The high-pressure compaction-resistant nano-carbon-coated aluminum current collector according to claim 1, wherein: The mesh-shaped conductive layer is formed by coating and baking a slurry, wherein the slurry comprises a conductive material, a binder, nanocellulose, a cross-linking agent, a solvent and a wetting agent.

3. The high-pressure-resistant nano-carbon-coated aluminum current collector according to claim 2, wherein: The high-pressure compaction-resistant nano-carbon-coated aluminum current collector meets any one or more of the following conditions: (1) The conductive material is a mixture of one or more of conductive carbon black, conductive graphite, graphene, and carbon nanotubes; (2) The binder is a mixture of one or more of PAA, PMMA, PVDF, and PTFE.

4. The high-pressure-resistant nano-carbon-coated aluminum current collector according to claim 3, wherein: The thickness of the nano carbon-coated aluminum current collector is 4-25 μm, and the coating surface density of any side of the mesh conductive layer is 0.1-2.0 g / m 2 .

5. A method for preparing a high-pressure compaction-resistant nano-carbon-coated aluminum current collector, comprising the following steps: Step S1: mixing conductive carbon black, conductive graphite, and nanocellulose, and dispersing them at high speed to obtain a mixture; Step S2: adding a solvent and performing high-speed dispersion to obtain a mixed solution; Step S3: adding a crosslinking agent and a binder, and performing high-speed dispersion; then adding a wetting agent, and performing high-speed dispersion to obtain a slurry; Step S4: coating the upper and lower surfaces of the aluminum current collector with the slurry, baking and rolling to form a mesh-shaped conductive layer, thereby obtaining a nano-carbon-coated aluminum current collector.

6. The method for preparing a high-pressure compaction-resistant nano-carbon-coated aluminum current collector according to claim 5, wherein: In step S3, the slurry is composed of conductive carbon black, conductive graphite, nanocellulose, a crosslinking agent, a binder, a wetting agent and a solvent in a mass ratio of 1: (0.1-0.5): (0.1-0.5): (0.01-0.05): (1-6): (0.01-0.20): (10-18).

7. The method for preparing a high-pressure compaction-resistant nano-carbon-coated aluminum current collector according to claim 6, wherein: The conductive carbon black and conductive graphite are surface modified by the following process: Conductive carbon black and conductive graphite are respectively mixed evenly with N-aminoethyl-3-aminopropylmethyldimethoxysilane and ethanol, heated to 40-50° C., reacted for 5-6 hours, and washed and dried to obtain modified conductive carbon black and modified conductive graphite.

8. The method for preparing a high-pressure compaction-resistant nano-carbon-coated aluminum current collector according to claim 6, wherein: The nanocellulose is modified, and the specific modification process is as follows: Step (1): Under nitrogen protection, 1,1,1-tris(4-hydroxyphenyl)ethane triglycidyl ether, 2,2'-diallylbisphenol A and tetrabutylammonium bromide are uniformly mixed, the mixture is heated to 75-85° C., reacted for 22-24 hours, cooled to room temperature, filtered, washed and dried to obtain a hyperbranched polymer; Step (2): mixing the nanocellulose, anhydrous ethanol and deionized water, performing ultrasonic treatment for 10-30 minutes, heating to 40-50° C., adding 3-mercaptopropyltriethoxysilane, reacting for 8-10 hours, centrifuging, washing and drying to obtain thiolated nanocellulose; Step (3): uniformly mixing the hyperbranched polymer, thiolated nanocellulose and N,N-dimethylformamide, adding a photoinitiator, irradiating with ultraviolet light, filtering, washing and freeze-drying to obtain modified nanocellulose.

9. A lithium ion battery, wherein: The lithium-ion battery contains a high-pressure-resistant nano-carbon-coated aluminum current collector as described in any one of claims 1 to 4.

Images