Composite coating for protecting liquid cooling plate of new energy power battery and preparation method of composite coating

Abstract

The invention relates to a composite coating for protecting a liquid cooling plate of a new energy power battery and a preparation method of the composite coating. The invention relates to a modified graphene / Cu-ZIF-8 double-carrier composite photocatalyst, which is prepared from the following raw materials in parts by weight: 70 to 90 parts of modified MXene / graphene double-carrier, 5 to 12 parts of core-shell structure Cu-ZIF-8 double-carrier powder, 15 to 25 parts of alkali-soluble acrylic copolymer resin, 0.5 to 1.5 parts of KH-570, 0.2 to 0.8 part of fluorocarbon surfactant L30, 8 to 12 parts of zinc phosphate, 8 to 12 parts of mica powder, 12 to 18 parts of polyamide wax, 2 to 4 parts of K-7318 and 12 to 18 parts of kieselguhr. Wherein the Cu (at) ZIF-8 (at) double-carrier powder with the core-shell structure is of a core-shell structure formed by in-situ growth of Cu (at) ZIF-8 on an MXene / graphene interface. According to the invention, a comprehensive protective layer with super-hydrophobicity, corrosion resistance, antibacterial property and high adhesive force is provided for the liquid cooling plate, and the performance is excellent.

Description

Technical Field

[0001] This invention relates to the field of protection technology for key components of the thermal management system of new energy power batteries, specifically to a composite coating for the protection of liquid cooling plates of new energy power batteries and its preparation method. Background Technology

[0002] With the rapid development of new energy electric vehicles, the thermal management safety of power batteries is of paramount importance. As a core component of the battery thermal management system, the liquid cooling plate is in direct contact with the coolant for extended periods, facing severe challenges such as electrochemical corrosion, ion penetration, and microbial growth (especially in ethylene glycol-water coolants). These factors can lead to corrosion perforation of the liquid cooling plate, coolant leakage, thermal management failure, and even safety accidents such as short circuits in the battery system.

[0003] Traditional protective coatings for liquid cooling plates (such as conventional epoxy coatings or passivation films) often have limited functionality and struggle to simultaneously meet the requirements of long-term corrosion protection, microbial inhibition, and resistance to long-term immersion in coolant and thermal cycling. While novel nanomaterials such as graphene or MXene can improve corrosion resistance, their dispersibility in coatings, their adhesion to the substrate, and their functional synergy remain technical challenges. In particular, microbial contamination in the coolant environment can form biofilms, reducing heat exchange efficiency and exacerbating localized corrosion, and current technologies lack effective active antibacterial mechanisms.

[0004] Therefore, developing a multifunctional composite coating that can firmly adhere to the liquid cooling plate substrate (usually aluminum alloy or stainless steel) and synergistically provide physical barrier, chemical corrosion protection, active antibacterial properties, and surface hydrophobicity (to prevent the adhesion of harmful substances in the coolant) is of great significance for improving the reliability, safety, and service life of power battery systems. Summary of the Invention

[0005] The purpose of this invention is to provide a composite coating for the protection of liquid-cooled plates in new energy power batteries and its preparation method. This coating, by constructing a "dual two-dimensional carrier-core-shell synergistic" system, solves the problem of traditional functional coatings that struggle to simultaneously achieve antibacterial, hydrophobic, and corrosion-resistant properties due to poor material interfacial compatibility and uneven dispersion of functional phases. It utilizes MXene (Ti3C2T) x The ZIF-8 nuclei are anchored by -F / -OH functional groups on the surface, while graphene sheets provide the extended plane. The two are cross-linked through a silane coupling agent to form a three-dimensional conductive network, suppressing stacking. Cu@ZIF-8 is grown in situ at the MXene / graphene interface, forming a "core-shell dual-barrier" structure (Cu@ZIF-8 as the core, and the two two-dimensional materials as the shell), extending the diffusion path of corrosive media by more than 3.2 times. The dual-carrier enhances Cu... 2+ / Zn 2+ Sustained-release stability, inhibition of ion burst release, and synergistic antibacterial activity of MXene (F -Destroying cell membranes) and the physical barrier of graphene achieve an antibacterial rate of ≥99% and a salt spray corrosion resistance of ≥1000h. This coating significantly improves the comprehensive protection performance of the coating, especially antibacterial properties, surface hydrophobicity (water contact angle > 150°), corrosion resistance and adhesion (≥13MPa, not more than grade 1), and can be widely used in fields with demanding protection performance such as liquid cooling plates of electric vehicle power battery packs, liquid cooling systems of battery clusters in energy storage power stations, and liquid cooling systems supporting high-power charging facilities.

[0006] To achieve the above object, the present invention provides the following technical solutions: A composite coating for protecting a liquid cooling plate of a new energy power battery, comprising the following raw materials in parts by weight: Modified MXene / graphene dual carrier: 70 - 90 parts, Core-shell structured Cu@ZIF-8@dual carrier powder: 5 - 12 parts, Alkali-soluble acrylic copolymer resin: 15 - 25 parts, Silane coupling agent KH-570: 0.5 - 1.5 parts, Fluorocarbon surfactant L30: 0.2 - 0.8 parts, Zinc phosphate: 8 - 12 parts, Mica powder: 8 - 12 parts, Polyamide wax: 12 - 18 parts, Curing accelerator K-7318: 2 - 4 parts, Diatomaceous earth: 12 - 18 parts; Among them, the core-shell structured Cu@ZIF-8@dual carrier powder is a core-shell structure formed by the in-situ growth of Cu@ZIF-8 on the MXene / graphene interface.

[0007] Cu@ZIF-8 is prepared by in-situ loading of copper ions (Cu 2+ ) into the ZIF-8 framework structure formed by the coordination of zinc ions (Zn 2+ ) with 2-methylimidazole.

[0008] Furthermore, the preparation process of the modified MXene / graphene dual carrier is: mixing MXene and reduced graphene oxide in a mass ratio of 0.8~1:1, and then adding silane coupling agent KH-570, reacting at 55~60°C for 2~3h to form a crosslinked modified MXene / graphene dual carrier, and the added mass of the silane coupling agent KH-570 is 1 / 4~1 / 3 of the total mass of MXene and reduced graphene oxide.

[0009] Furthermore, the core-shell structured Cu@ZIF-8@dual carrier powder is prepared from the modified MXene / graphene dual carrier as the raw material, and the specific preparation process is: The modified MXene / graphene dual carrier was prepared into a dual carrier methanol dispersion. The dual carrier methanol dispersion was taken and Zn(NO3)2·6H2O and Cu(NO3)2·3H2O were added. The mixture was magnetically stirred at 40°C for 30 min. A methanol solution containing 2-methylimidazole was added dropwise, and the mixture was stirred at 60°C for 4 hours to achieve heterogeneous nucleation and in-situ crystallization of ZIF-8 on the support surface. The total mass ratio of zinc nitrate hexahydrate and copper nitrate trihydrate to the total methanol was (0.3~0.6) g:40 mL, the mass ratio of 2-methylimidazole to the total methanol was (0.3~0.7) g:40 mL, and the mass ratio of the modified MXene / graphene dual carrier to the total methanol was (0.4~0.6) g:40 mL. After in-situ crystallization, the powder was centrifuged at 8000~12000 rpm, washed with methanol 3~5 times, and vacuum dried at 50-70℃ for 6-10 hours to obtain the core-shell structured Cu@ZIF-8@ dual-carrier powder, which is a light blue core-shell powder.

[0010] Furthermore, the composite coating, after testing, has an adhesion grade of ≤1 in the cross-cut adhesion test, a tensile strength of ≥13.5MPa, an antibacterial rate of not less than 99.0%, a water contact angle of >150°, and a salt spray corrosion resistance of not less than 800h; preferably, the antibacterial rate is not less than 99.3%, and the salt spray corrosion resistance is not less than 1000h.

[0011] Furthermore, the mass ratio of the modified MXene / graphene dual carrier to the core-shell structure Cu@ZIF-8@ dual carrier powder is 100:(10~15).

[0012] Furthermore, the mass ratio of zinc nitrate hexahydrate to copper nitrate trihydrate is (10~16):2.

[0013] The preparation process of the above-mentioned composite coating is as follows: a. The diatomaceous earth is ball-milled to 20-25 μm to obtain pretreated diatomaceous earth; b. Mix the modified MXene / graphene dual carrier, alkali-soluble acrylic copolymer resin and deionized water, and add zinc phosphate and pretreated diatomaceous earth; c. Stir at 85±5℃ for 50~60 min, then centrifuge at 3500~3600 rpm to remove impurities; d. Add mica powder and curing accelerator to the filtrate after centrifugation and mix well. Then add polyamide wax, KH-570 and L30. Stir well at 85±5℃ and then perform high-temperature curing treatment to obtain modified dispersion. e. Add the core-shell structured Cu@ZIF-8@ dual-carrier powder to the modified dispersion, and then ultrasonically treat it at 50~65℃ to obtain the composite coating for the protection of the liquid cooling plate of the new energy power battery.

[0014] Furthermore, during the application of the composite coating, ultrasonic-assisted spraying is used to allow the graphene sheets to be laid flat on the substrate surface.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention exhibits synergistic and highly efficient antibacterial properties: the synergistic effect of the dual carriers constructs a highly efficient functional platform: the -F / -OH functional groups on the MXene surface precisely anchor the ZIF-8 crystal nuclei, significantly improving the loading rate (>90%) and preventing detachment; the graphene sheets provide an extended plane, cross-linking with MXene through a silane coupling agent to form a three-dimensional conductive network, completely suppressing the problem of two-dimensional material stacking. This unique structure enables Cu... 2+ / Zn 2+ Achieving synergistic sustained release—MXene conductive network promotes uniform ion diffusion, graphene physical barrier extends release cycle, dual-ion antibacterial efficiency exceeds 99.99% (>7% improvement compared to physical mixing system), antibacterial spectrum and long-lasting effect far surpass traditional technology.

[0016] This invention exhibits superior corrosion resistance. Its "core-shell dual-barrier" structure (Cu@ZIF-8 as the core and dual two-dimensional materials as the shell) forms a triple protection mechanism: the MXene / graphene cross-linked network constructs a dense "dual two-dimensional maze" in the coating, extending the diffusion path of corrosive media by 3.2 times, with measured salt spray corrosion resistance >800 hours, preferably >1000 hours; the high conductivity of MXene accelerates electron transfer, synergistically forming a stable passivation film with zinc phosphate, while ions released from Cu@ZIF-8 deposit protective oxides at defects; a silane coupling agent bridges the dual carriers and the alkali-soluble acrylic copolymer resin, combined with the core-shell structure for efficient micropore filling (BET>1100m). 2 / g), which reduces the porosity of the coating by more than 60% and completely blocks the permeation channels.

[0017] The coating prepared by this invention exhibits high adhesion: zinc phosphate reacts chemically with the surface of the metal substrate to form a strong chemical bond. The silane coupling agent KH-570 improves the compatibility and interfacial bonding between inorganic fillers (graphene, mica, diatomaceous earth) and organic resins (alkali-soluble acrylic copolymer resin). The dense coating structure, well-bonded to the substrate, together ensures excellent adhesion (0-1 grade), achieving better interfacial performance at a lower cost, resulting in superior overall performance.

[0018] The coating of this invention constructs a core-shell structure Cu@ZIF-8@ dual-carrier powder, which aims to provide a comprehensive protective layer for liquid cooling plates with superhydrophobicity, corrosion resistance, antibacterial properties and high adhesion. The dual carrier adopts a two-dimensional carrier composed of MXene / graphene, which has excellent performance. Detailed Implementation

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

[0020] It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the following description is only used to explain the present invention and is not intended to limit the present invention.

[0022] All reagents used in the following examples and comparative examples are commercially available products.

[0023] Example 1: Preparation of modified MXene / graphene dual carrier Add 1.0 g Ti3AlC2 to 20 mL 40% wt HF and stir magnetically at 35 °C for 24 h; Centrifuge and wash until pH > 6, add 0.5M TMAOH solution to the precipitate, sonicate at 20KHz for 1h (ultrasonic power of 300W), and dry to obtain exfoliated MXene.

[0024] Mix 0.8g of exfoliated MXene with 1.0g of reduced graphene oxide (rGO), and add 0.5g of KH-570; The modified MXene / graphene dual carrier was obtained by reacting at 60℃ for 2 hours, and the zeta potential was measured to be +38mV.

[0025] Example 2: Preparation of core-shell structured Cu@ZIF-8@dual-carrier powder The modified MXene / graphene dual carrier from Example 1 was dispersed in ethanol or methanol (methanol was used in this example) to prepare a dual carrier dispersion. 0.297g Zn(NO3)2·6H2O and 0.042g Cu(NO3)2·3H2O were added, and the mixture was magnetically stirred at 40°C for 30min.

[0026] A methanol solution containing 0.65 g of 2-methylimidazole (collectively referred to as 2-methylimidazole solution) was added dropwise, and the mixture was stirred at 60 °C for 4 h (not at room temperature) to complete the in-situ crystallization of ZIF-8; the total volume of all methanol was 40 mL; and the mass of the modified MXene / graphene dual carrier was 0.5 g.

[0027] After in-situ crystallization, the powder was centrifuged at 10,000 rpm, washed three times with methanol, and vacuum dried at 60°C for 8 hours to obtain a light blue core-shell powder (coating rate 92%, BET 1120 m). 2 / g), which is the core-shell structured Cu@ZIF-8@ dual-carrier powder.

[0028] Example 3: Preparation of composite coatings Take a certain amount of diatomaceous earth and crush it by ball milling (ball-to-material ratio 5:1, 30 min). Pass it through a 600-mesh sieve and collect the undersize portion. Seal it for later use. Take 80 parts of modified MXene / graphene dual carrier (Example 1), 20 parts of alkali-soluble acrylic copolymer resin, and 30 parts of deionized water and mix them. Then add 10 parts of zinc phosphate and 15 parts of ball-milled diatomaceous earth. Stir the mixture evenly at room temperature using an anchor-type stirring paddle at 1000 rpm. Initial reaction: Heat to 85℃ at a rate of 2℃ / min and stir for 50min at a stirring speed of 1000rpm. Use a viscometer to control the viscosity of the system to ≤500cP and monitor in real time. Centrifugal purification: Transfer the mixture into a high-temperature resistant centrifuge tube and centrifuge at 25℃, 3500r / min for 10min. After centrifugation, collect the supernatant and discard the bottom precipitate >5μm to remove impurities. Functional addition: Transfer the filtrate (supernatant) after centrifugation to a mixer, and add in sequence: 10 parts mica powder (pre-dried, 105℃, 2h) and 3 parts curing accelerator K-7318. Use a serrated dispersion disc to stir at 1200rpm for 60min until well mixed. Modification and strengthening: Using a constant pressure dropping funnel to control the flow rate, slowly add 15 parts of polyamide wax 6900-20X to the system, then add 1.0 part of silane coupling agent KH-570 and 0.5 parts of fluorocarbon surfactant L30, heat to 85±5℃ at 1℃ / min, stir at 800rpm for 90min, and stir until uniform. High-temperature curing treatment: Keep warm at 85±5℃ for 60 minutes, cool down to 40℃ and discharge to obtain modified dispersion; Five portions of core-shell structure Cu@ZIF-8@ dual-carrier powder (Example 2) were then added to the modified dispersion and ultrasonically treated at 60°C for 2 hours (ultrasonic power of 500W) to obtain the composite coating for the protection of the liquid cooling plate of the new energy power battery, which is the core-shell structure Cu@ZIF-8 composite coating reinforced by MXene / graphene dual two-dimensional carriers.

[0029] Example 4: Preparation of composite coatings The steps and raw materials of the composite coating in this embodiment are the same as those in Example 3, except that the amount of Cu@ZIF-8@ dual carrier powder with core-shell structure added is 10 parts.

[0030] Example 5: Preparation of composite coatings The steps and raw materials of the composite coating in this embodiment are the same as those in Example 3, except that the amount of Cu@ZIF-8@ dual carrier powder with core-shell structure added is 12 parts.

[0031] Comparative Example 1: 90 parts of ordinary aqueous reduced graphene oxide were used to replace the dual carrier, and 10 parts of physically mixed Cu@ZIF-8 powder (non-core-shell structure) were added. The remaining components and steps were the same as in Example 4.

[0032] Comparative Example 2: The dual carrier of Example 1 was used, but 10 parts of physically mixed Cu@ZIF-8 powder were added, and the rest was the same as in Example 4.

[0033] Comparative Example 3: Cu@ZIF-8 was supported only with MXene (graphene-free), with the same addition amount as in Example 4, and the other components were the same.

[0034] Comparative Example 4: A certain brand of epoxy anti-corrosion paint (50% solid content) was selected and applied according to the manufacturer's instructions. Ten parts of physically mixed ZIF-8 powder and CuO nanopowder (calculated based on a Zn:Cu molar ratio of 4:1) were used to replace Cu@ZIF-8 powder. The physically mixed powders underwent only simple mechanical mixing. Ten parts of the mechanically mixed powder were added to the epoxy anti-corrosion paint and ultrasonically treated at 60℃ for 2 hours (ultrasonic power 500W).

[0035] To test the relevant performance of the composite coating of this application, the composite coating was sprayed onto the surface of a 1×1cm copper sheet using ultrasonic-assisted spraying. During the spraying process, ultrasonic vibration energy was applied to the workpiece to cause the graphene microflakes located in the viscous coating to gradually extend and spread out on the workpiece surface. The coating thickness was 0.2μm. The test was conducted to simulate the service process. Specifically, the following tests were performed on Examples 3-5 and Comparative Examples 1-4, and the test results are shown in Table 1: Corrosion Resistance Test: Neutral Salt Spray Test (NSS, GB / T10125-2021): A prepared sodium chloride solution with a mass fraction of (5±1)% is injected into the salt spray test chamber, and the temperature inside the test chamber is maintained at (35±2)℃. Salt spray is generated through a spraying device. The salt spray needs to be sprayed continuously, and the deposition rate is (1~2) mL / (80cm). 2 Within the specified timeframe (h), the test sample must be placed at the prescribed angle to ensure that the salt spray settles evenly on the sample surface. The test duration should be determined based on the sample characteristics and test requirements. During the test, observe the corrosion of the sample. After the test, clean and inspect the sample to evaluate its corrosion resistance. Record the time (h) at which red rust appears on the coating.

[0036] Antibacterial test: According to GB / T31402-2023, determination of antibacterial activity of plastic and other non-porous materials [S]. The antibacterial properties of each coating were tested.

[0037] Surface hydrophobicity: The static water contact angle (°) of the coating surface was measured using an OCA200 fully automatic single-fiber contact angle meter. The average value was taken from 5 different test points.

[0038] Adhesion test: GB / T5210-2006, Paints and varnishes, pull-off adhesion test [S]. Record the pull-off strength (MPa) and failure type (A: cohesive failure, B: adhesion failure).

[0039] According to the ISO 2409-2007 cross-cut adhesion test, the adhesion of coatings was determined using an F107 cross-cut tester. A grade of 0 is defined as follows: completely smooth edges with no peeling at the edges of the cuts; grade 1 is defined as small areas of peeling at the intersections of the cuts, with actual damage not exceeding 5% of the cut area; grade 2 is defined as peeling at the edges or intersections of the cuts, covering 5-15% of the area; grade 3 is defined as peeling at the edges or intersections of the cuts, covering 15-20% of the area; grade 4 is defined as peeling at the edges or intersections of the cuts, covering 20-25% of the area; and grade 5 is defined as large areas of peeling at the edges of the cuts, covering 25-35% of the area.

[0040] Table 1

[0041] This invention's composite coating exhibits groundbreaking comprehensive protective performance. A technological leap is achieved through a triple synergistic mechanism: First, the core-shell structure Cu@ZIF-8@dual carrier achieves long-term sustained release of copper-zinc dual ions (antibacterial rate ≥99.3%), with its efficiency against Escherichia coli and Staphylococcus aureus significantly exceeding that of physical mixing systems (antibacterial rate ≤92.8% in Comparative Examples 1-4). In particular, Example 4 shows antibacterial rates of 99.9% and 99.7% against the two pathogens, respectively, verifying the synergistic effect of MOF sustained release and MXene / graphene antibacterial synergy. Second, the superhydrophobic interface formed by the directional migration of silane coupling agent and fluorocarbon surfactant in the dual carrier system (contact angle 155°±2° in Example 4) effectively blocks media penetration, while Comparative Example 4, lacking the dual carrier structure (... The contact angle of the composite epoxy numerical solution was only 105°±4°. The single-load system without graphene (Comparative Example 3, contact angle 92°±3°) confirmed the synergistic hydrophobic mechanism of MXene-F groups and graphene micro-nano roughness. The silane coupling agent KH-570 and fluorocarbon surfactant L30 migrated to the surface during the coating curing process, resulting in a water contact angle >150° in the current system. Furthermore, the "brick-and-mortar" labyrinth structure formed by MXene / graphene in the multi-level anti-corrosion barrier, the nanopore filling of Cu@ZIF-8, and the chemical bonding of zinc phosphate enabled the salt spray corrosion resistance of Examples 3-4 to exceed 1000 hours, which is 138% higher than the best comparative example (comparative example 4, salt spray corrosion resistance of 420 hours).

[0042] Key data comparisons show that Example 4 (core-shell structure Cu@ZIF-8@dual carrier powder addition of 10%) is the optimal performance solution: its antibacterial activity reaches peak (99.9% E. coli inhibition rate), its hydrophobicity is the strongest (155°±2 contact angle), its corrosion resistance is on par with Example 3 and significantly better than Example 5 (850 hours of salt spray), which suffered from decreased density due to excessive addition, while maintaining the highest adhesion level (14.8 MPa tensile strength, grade 0 cross-cut). This solution perfectly balances functionality and stability, achieving a comprehensive leap over commercial anti-corrosion paint (Comparative Example 4) in corrosion resistance (>1000h vs 420h), antibacterial rate (99.9% vs 88.3%), and adhesion (14.8 MPa vs 11.0 MPa), providing a revolutionary protective solution for harsh environments such as liquid cooling plates for electric vehicle power battery packs and liquid cooling systems for battery clusters in energy storage power stations.

[0043] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A composite coating for the protection of liquid-cooled plates of new energy power batteries, characterized in that, The raw materials include the following parts by weight: Modified MXene / graphene dual carriers: 70 - 90 parts, Core - shell structured Cu@ZIF - 8@dual - carrier powder: 5 - 12 parts, Alkali - soluble acrylic copolymer resin: 15 - 25 parts, Silane coupling agent KH - 570: 0.5 - 1.5 parts, Fluorocarbon surfactant L30: 0.2 - 0.8 parts, Zinc phosphate: 8 - 12 parts, Mica powder: 8 - 12 parts, Polyamide wax: 12 - 18 parts, Curing accelerator K - 7318: 2 - 4 parts, Diatomite: 12 - 18 parts; Among them, the core - shell structured Cu@ZIF - 8@dual - carrier powder is a core - shell structure formed by the in - situ growth of Cu@ZIF - 8 on the MXene / graphene interface.

2. The composite coating for protecting liquid-cooled plates of new energy power batteries according to claim 1, characterized in that: The preparation process of the modified MXene / graphene dual carriers is as follows: Mix MXene and reduced graphene oxide according to a mass ratio of 0.8~1:1, and then add silane coupling agent KH - 570. React at 55~60 °C for 2~3 h to form the modified MXene / graphene dual carriers. The added mass of the silane coupling agent KH - 570 is 1 / 4~1 / 3 of the total mass of MXene and reduced graphene oxide.

3. The composite coating for protecting liquid-cooled plates of new energy power batteries according to claim 2, characterized in that: The core - shell structured Cu@ZIF - 8@dual - carrier powder is prepared from the modified MXene / graphene dual carriers. The specific preparation process is as follows: Prepare a dual - carrier methanol dispersion of the modified MXene / graphene dual carriers. Take the dual - carrier methanol dispersion, add Zn(NO3)2·6H2O and Cu(NO3)2·3H2O, and stir magnetically at 40 °C for 30 min; Dropwise add a methanol solution containing 2 - methylimidazole, stir at 60 °C for 4 h, and complete the in - situ crystallization of ZIF - 8 by heterogeneous nucleation on the surface of the carrier; Among them, the ratio of the total mass of zinc nitrate hexahydrate and copper nitrate trihydrate to the total volume of methanol is (0.3~0.6) g:40 mL, the ratio of the mass of 2 - methylimidazole to the total volume of methanol is (0.3~0.7) g:40 mL; the ratio of the mass of the modified MXene / graphene dual carriers to the total volume of methanol is (0.4~0.6) g:40 mL; After in - situ crystallization, centrifuge at a speed of 8000~12000 rpm, wash with methanol 3~5 times, and dry in vacuum. The drying temperature is 50 - 70 °C, and the drying time is 6 - 10 h to obtain the core - shell structured Cu@ZIF - 8@dual - carrier powder.

4. The composite coating for protecting liquid-cooled plates of new energy power batteries according to claim 3, characterized in that: The core-shell structured Cu@ZIF-8@dual-carrier powder exhibits a Cu@ZIF-8 coating rate >90% and a BET >1100 m. 2 / g.

5. The composite coating for protecting liquid-cooled plates of new energy power batteries according to claim 1, characterized in that: The composite coating is tested. The cross - hatch adhesion grade ≤ 1 level, the pull - off strength ≥ 13.5 MPa, the antibacterial rate is not less than 99.0%, the water contact angle > 150°, and the salt - spray corrosion resistance is not less than 800 h.

6. The composite coating for protecting liquid-cooled plates of new energy power batteries according to claim 1, characterized in that: The mass ratio of the modified MXene / graphene dual carriers to the core - shell structured Cu@ZIF - 8@dual - carrier powder is 100:(10~15).

7. The composite coating for protecting liquid-cooled plates of new energy power batteries according to any one of claims 1-6, characterized in that: The composite coating is used in the liquid - cooled plates of electric vehicle power battery packs, the liquid - cooled systems of battery clusters in energy storage power stations, and the liquid - cooled systems supporting high - power charging facilities.

8. A method for preparing a composite coating for the protection of liquid-cooled plates of new energy power batteries as described in claim 1, characterized in that: The process of the preparation method is as follows: a. Ball - mill diatomite to 20~25 μm to obtain pretreated diatomite; b. Mix the modified MXene / graphene dual carrier, alkali-soluble acrylic copolymer resin and deionized water, and add zinc phosphate and pretreated diatomaceous earth; c. Stir at 85±5℃ for 50~60 min, then centrifuge at 3500~3600 rpm to remove impurities; d. Add mica powder and curing accelerator to the filtrate after centrifugation and mix well. Then add polyamide wax, KH-570 and L30. Stir well at 85±5℃ and then perform high-temperature curing treatment to obtain modified dispersion. e. Add the core-shell structured Cu@ZIF-8@ dual-carrier powder to the modified dispersion, and then ultrasonically treat it at 50~65℃ to obtain the composite coating for the protection of the liquid cooling plate of the new energy power battery.

9. The preparation method according to claim 8, characterized in that: During the application of composite coatings, ultrasonic-assisted spraying is used to spread graphene sheets evenly on the substrate surface.

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