Preparation method and application of cable for liquid-cooled high-power charging pile

Abstract

The present invention discloses a preparation method and application of a cable for a liquid-cooled high-power charging pile, which belongs to the technical field of liquid-cooled cables and is used to solve the technical problem in the prior art that the flame retardant and fire-resistant properties of liquid-cooled cables need to be further improved; the present invention comprises the following steps: using a plurality of modified heat-conducting pipes to be spirally arranged on the surface of an insulating layer to obtain a heat exchange layer, and adopting a collaborative design of composite fiber cloth and modified heat-conducting pipes to make the liquid-cooled cable have excellent fire resistance and flame retardant properties, wherein the glass fiber and silicon-aluminum structure in the composite fiber cloth decompose at high temperature to form a protective layer, which effectively blocks heat transfer and flame spread, and ensures the structural integrity of the heat-conducting pipe. At the same time, the coolant circulation system quickly takes away the heat of the flame, further protecting the wire core layer and the insulation layer, and avoiding the occurrence of secondary combustion caused by leakage of organic coolant.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid-cooled cables, and in particular to a preparation method and application of a cable for a liquid-cooled high-power charging pile. Background Art

[0002] Liquid-cooled high-power charging pile cables have continuously improved their heat dissipation efficiency and safety performance under the optimization of heat pipe and heat lock layer technology to meet the needs of high-power charging. In the early days, copper and aluminum heat pipes and foam and silicone insulation layers were used for thermal management, but the heat dissipation effect was limited. With the increase in charging power, composite heat pipes and microchannel liquid cooling technology were gradually introduced to improve heat exchange efficiency. At present, nano-thermal conductive materials and multi-channel composite materials are used to enable cables to still dissipate heat efficiently in high-voltage charging environments above 800V. At the same time, the heat lock layer has developed from basic foam insulation to halogen-free and low-smoke composite materials to improve high temperature resistance and safety. At present, ceramic fiber and carbon fiber composite materials combined with intelligent temperature control systems can control temperature more accurately and prevent overheating risks. Overall, the continuous optimization of heat pipes and heat lock layers makes liquid-cooled cables safer and more efficient, providing guarantees for the development of ultra-high power charging technology.

[0003] The prior art CN118782313A discloses a wear-resistant liquid-cooled cable with an ultra-large current load for new energy use, comprising a plurality of conductors, wherein an insulating layer, a shielding layer and an outer sheath layer are sequentially arranged on the outside of the plurality of conductors, and a heat exchange layer composed of a plurality of heat exchange tubes is arranged between the shielding layer and the outer sheath layer, wherein the plurality of heat exchange tubes are all arranged in a spiral shape. The heat exchange performance inside the cable is improved by preparing the insulating layer using a heat-conductive filler, and the thermal insulation and wear resistance of the cable outer sheath layer is improved by preparing the cable outer sheath layer by synthesizing a composite polyolefin, thereby obtaining a liquid-cooled cable with high heat exchange efficiency inside, wear resistance outside and suitable for high temperature.

[0004] However, the above patent improves the heat exchange efficiency of the liquid-cooled cable by improving the thermal conductivity of the insulation layer and the thermal insulation of the outer sheath layer. However, the outer sheath layer is in direct contact with the heat pipe. During the combustion process, the heat and flame generated will be quickly transferred to the heat exchange layer, causing the liquid-cooled cable to burn rapidly. Because the structure does not protect the heat exchange layer, the organic coolant that overflows when the cooling pipe ruptures may cause secondary combustion. Therefore, the fire resistance and flame retardant properties of the cable need to be further improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and application of a cable for a liquid-cooled high-power charging pile, which is used to solve the technical problem in the prior art that the flame retardancy and fire resistance of liquid-cooled cables need to be further improved.

[0006] The purpose of the present invention can be achieved by the following technical solution: A method for preparing a cable for a liquid-cooled high-power charging pile, comprising the following steps:

[0007] S1. Split the positive and negative cores of the dual-core power line into two, and use two positive and two negative spirals to wrap them on the surface of a single modified heat pipe to obtain a core layer;

[0008] Principle: By splitting the power line, the contact area between the power line and the heat exchange layer is increased, the heat dissipation efficiency is enhanced, and the load is reduced, thereby reducing the heat generated by the core layer.

[0009] S2. Use polyvinyl chloride wrapping tape to wrap the surface of the wire core layer to obtain an insulation layer;

[0010] S3, using a plurality of modified heat conducting pipes to be spirally arranged on the surface of the insulation layer to obtain a heat exchange layer;

[0011] S4. Wrap the surface of the heat exchange layer with composite fiber cloth and fix it to obtain a heat locking layer;

[0012] S5. Use composite polypropylene material to melt extrude and coat the surface of the heat-locking layer, and obtain a sheath layer after solidification, thereby obtaining a liquid-cooled cable.

[0013] Furthermore, in step S1, the modified heat-conducting pipe is obtained by melt-extruding a composite polyvinyl chloride material, coating it on a mold, and curing and demolding it; the composite polyvinyl chloride material includes the following raw materials in parts by weight: 30-50 parts of polypropylene, 30-50 parts of thermal conductive filler, 5-10 parts of plasticizer, 2-5 parts of heat stabilizer, 0.5-2 parts of lubricant, 3-10 parts of impact-resistant agent and 0.5-2 parts of dispersant; in step S5, the composite polypropylene material includes the following raw materials in parts by weight: 70-75 parts of polypropylene, 5-10 parts of plasticizer, 0.2-1 part of antioxidant, 0.2-2 parts of light stabilizer, 5-10 parts of impact-resistant agent, 5-10 parts of filler and 0.5-2 parts of lubricant.

[0014] Furthermore, in step S1, the preparation method of the modified heat pipe includes: adding the composite polyvinyl chloride material into a twin-screw extruder, wherein the temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170°C, 185°C, 185°C, 190°C, 190°C, 200°C, 200°C, and 210°C, respectively, the main engine speed of the twin-screw extruder is 80-120 rpm, and the pressure is 100-150 bar, melt-extruding and coating the material on a mold, curing and demolding, to obtain the modified heat pipe;

[0015] Furthermore, the plasticizer in the composite polyvinyl chloride material is one or more of dioctyl phthalate, dibutyl phthalate and dioctyl adipate; the heat stabilizer is one or more of tribasic lead sulfate, calcium stearate and dibutyltin dilaurate; the lubricant is one or more of calcium stearate, oxidized polyethylene wax and montan wax; the impact agent is one or more of epoxy soybean oil, dioctyl terephthalate and diisooctyl phthalate; and the dispersant is one or more of polyvinyl alcohol, sodium polyacrylate and polyvinyl ether.

[0016] Furthermore, in step S5, the melt extrusion operation includes: adding the composite polypropylene material into a twin-screw extruder, wherein the temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 200° C., 215° C., 215° C., 220° C., 220° C., 230° C., 230° C., and 240° C., and the main engine speed of the twin-screw extruder is 80-120 rpm and the pressure is 100-150 bar;

[0017] Furthermore, the plasticizer in the composite polypropylene material is one or more of dioctyl phthalate, dibutyl phthalate and dioctyl adipate; the antioxidant is one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tris(2,4-di-tert-butylphenyl) phosphate and hexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate; the light stabilizer is one or two of 2-hydroxy-4-octyloxybenzophenone and bis(2,2,6,6-tetramethylpiperidinyl)sebacate; the impact agent is one or more of epoxy soybean oil, dioctyl terephthalate and diisooctyl phthalate; the filler is one or more of calcium carbonate, talc and barium sulfate; and the lubricant is one or more of calcium stearate, oxidized polyethylene wax and montan wax.

[0018] Furthermore, the preparation method of the thermal conductive filler comprises the following steps:

[0019] A1. Transfer the graphite to a vacuum furnace at 2000°C and keep it at that temperature for 4-5 minutes. Then, introduce toluene gas into the reactor and keep it at that temperature for 20-30 minutes. Then, naturally cool it to room temperature to obtain pyrolytic graphite.

[0020] A2. Transfer the pyrolytic graphite to a heated vacuum furnace at 2800-3100°C, introduce nitrogen, maintain the internal pressure of the heated vacuum furnace at 6-8 MPa, hold the temperature for 40-60 minutes, and then cool it to room temperature at a cooling rate of 3-4 min°C / min to obtain annealed graphite;

[0021] A3, using plasma to modify annealed graphite to obtain activated annealed graphite;

[0022] A4. Add activated annealed graphite, ethanol, saturated sodium hydroxide solution and deionized water into a reactor and introduce nitrogen protection. After the temperature of the reactor is reduced to 5-10°C, add 3-(2,3-epoxypropoxy)propyltrimethoxysilane into the reactor, keep the temperature and react for 20-30 minutes, and then post-treat to obtain a thermally conductive filler.

[0023] The reaction principle for preparing thermally conductive fillers is as follows: through toluene pyrolysis and annealing treatment, the hexagonal lattice of graphite is made more complete and defects and vacancies are reduced. After plasma modification, active functional groups are generated in the graphite structure, and under alkaline conditions, the siloxane chain segments of the silane coupling agent are hydrolyzed, thereby cross-linking on the surface of the graphite structure, thereby preparing a thermally conductive filler.

[0024] Furthermore, in step A3, the plasma modification operation is as follows: the annealed graphite is evenly coated on a quartz wafer and then transferred to a plasma treatment device, the vacuum pump is turned on to extract the chamber gas until the vacuum degree is less than 10 mTorr, the gas control system is turned on, and a mixed gas with a volume ratio of argon and oxygen of 4:1 is introduced, the instrument power is set to 50-80 W, the mixed gas flow rate is 100-150 sccm, and the pressure is 100-150 mTorr, the radio frequency power supply is turned on, and after treating at room temperature for 3-5 minutes, the radio frequency power supply is turned off and argon is purged for 1-2 minutes to obtain activated annealed graphite;

[0025] Furthermore, in step A4, the ratio of activated annealed graphite, ethanol, saturated sodium hydroxide solution, deionized water and 3-(2,3-epoxypropoxy)propyltrimethoxysilane is 8-10g:2-3g:2-3mL:40-60mL:3-5g, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is filtered to collect the filter cake, the filter cake is washed with ethanol 3-5 times, and the filter cake is transferred to a vacuum drying oven and vacuum dried to constant weight to obtain a thermally conductive filler.

[0026] Furthermore, the preparation method of the composite fiber cloth comprises the following steps:

[0027] B1. Aluminum chloride hexahydrate, methyl orthosilicate, and deionized water are added to a reactor, stirred at room temperature for 10-15 minutes, and then a hydrolysis aid and modified glass fiber are added to the reactor, and stirring is continued for 30-40 minutes to obtain a glass fiber gel;

[0028] B2. Transfer the glass fiber gel to a mold, take an aluminum foil of the same shape and size as the mold, and coat one side of the aluminum foil with 8-10 wt% sodium hydroxide aqueous solution. Then, attach the coated side of the aluminum foil to the surface of the glass fiber gel. Treat the mold at a constant temperature of 30-50°C for 40-60 minutes, and then post-treat to obtain a composite fiber cloth.

[0029] The reaction principle for preparing the composite fiber cloth is as follows: under alkaline conditions, methyl orthosilicate, aluminum isopropoxide and aluminum chloride hexahydrate are hydrolyzed to produce a colloidal structure, and the modified glass fiber is cross-linked with the colloidal structure through its surface-modified siloxane structure to obtain a glass fiber gel, and hydrolysis cross-linking is formed through the active structure on the gel surface and the activated aluminum foil surface to finally prepare the composite fiber cloth.

[0030] Furthermore, in step B1, the amount ratio of aluminum chloride hexahydrate, methyl orthosilicate, deionized water, auxiliary agent and modified glass fiber is 4-5g:6-8g:40-50mL:12-16mL:8-10g, the hydrolysis aid is aluminum isopropoxide, ethanol and sodium hydroxide powder in the amount ratio of 2-3g:10-12mL:1-2g, and the stirring rate of the reactor is 60-80rpm;

[0031] Furthermore, in step B2, post-processing includes: transferring the mold to a vacuum drying oven at a temperature of 80-100° C., vacuum drying until no liquid is extracted, and demolding to obtain the composite fiber cloth.

[0032] Furthermore, the preparation method of the modified glass fiber comprises the following steps:

[0033] C1. Add glass fiber and 3-5 wt% sodium hydroxide aqueous solution into a reactor and stir. Raise the temperature of the reactor to 60-80°C, keep the temperature for 1-2 hours, and perform post-processing to obtain etched fiber.

[0034] C2. Add the etched fiber, triethylamine and N,N-dimethylformamide into the reactor, introduce nitrogen protection, add the modification liquid into the reactor, react for 40-60 minutes, and post-treat to obtain the modified glass fiber.

[0035] The reaction principle for preparing modified glass fiber is: under low alkaline conditions, active sites such as hydroxyl groups are formed on the surface of the glass fiber, and further modification with a silane coupling agent forms a siloxane structure on the surface of the fiber structure, ultimately preparing modified glass fiber.

[0036] Furthermore, in step C1, the stirring rate of the reactor is 60-80 rpm, the amount ratio of the glass fiber and the 3-5 wt% sodium hydroxide aqueous solution is 1-2 g: 10-15 mL, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is filtered to collect the filter cake, the filter cake is washed with ethanol 3-5 times, and the filter cake is transferred to a vacuum drying oven and vacuum dried to constant weight to obtain the etched fiber;

[0037] Furthermore, in step C2, the etching microspheres, triethylamine, N,N-dimethylformamide and modification liquid are used in a ratio of 4-5g:0.5-0.8g:15-18mL:8-10mL, and the modification liquid is obtained by mixing 3-isocyanatepropyltrimethoxysilane and N,N-dimethylformamide in a ratio of 1-2g:5mL. The post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is filtered to collect the filter cake, the filter cake is washed with ethanol 3-5 times, and the filter cake is transferred to a vacuum drying oven and vacuum dried to constant weight to obtain modified glass fiber.

[0038] The invention discloses an application of a cable for a liquid-cooled high-power charging pile. The liquid-cooled cable prepared by the preparation method of the cable for a liquid-cooled high-power charging pile is applied to electric vehicle fast charging piles and electric commercial vehicle charging.

[0039] The present invention has the following beneficial effects:

[0040] 1. The liquid-cooled cable prepared in the present invention uses the modified heat-conducting pipe with high internal thermal conductivity and the heat-locking composite fiber cloth to carry away the heat generated by the core layer through the internal coolant circulation, thereby reducing the impact of internal heat on the cable life. During the combustion process, the protective layer structure generated by the decomposition of the glass fiber and silicon-aluminum structure of the composite fiber cloth at high temperature isolates the heat transfer and the spread of the flame, ensuring the structural integrity of the heat-conducting pipe. The heat of the flame is carried away by the coolant circulation, protecting the core layer and the insulation layer while avoiding the occurrence of secondary combustion caused by coolant leakage. The coordinated cooperation of the modified heat-conducting pipe and the composite fiber cloth significantly improves the fire resistance and flame retardant properties of the liquid-cooled cable, and the multiple reflection effect brought by the multi-layer structure of annealed graphite and the coordinated cooperation of the aluminum foil attached to the surface of the composite fiber cloth significantly increase the shielding performance of the cable, so that electromagnetic waves in a wider frequency range can be effectively shielded, thereby significantly improving the thermal conductivity and anti-electromagnetic interference performance of the thermal conductive filler.

[0041] 2. The present invention etches the surface of the glass fiber to significantly improve the activity of the glass fiber. On this basis, a silane coupling agent is used to modify the surface of the glass fiber, so that it participates in the hydrolysis process of aluminum chloride hexahydrate, methyl orthosilicate and aluminum isopropylate, so that the glass fiber is evenly dispersed inside the hydrolysis gel. While using the glass fiber to improve the thermal insulation performance of the composite fiber cloth, its surface is modified to reduce the damage of the fiber structure to the heat pipe. The surface of the aluminum foil is further activated with a sodium hydroxide aqueous solution. Under alkaline catalysis, the hydroxyl structure on the surface of the activated aluminum foil and the active structure on the surface of the glass fiber gel are hydrolyzed to form a stable cross-linked structure to obtain a composite fiber cloth. The composite fiber cloth locks heat inside during the operation of the cable, so that the heat generated by the core layer is evenly distributed and slowly transferred to the outer sheath, thereby reducing the negative impact of internal heat on the service life of the cable.

[0042] 3. In the present invention, toluene gas is first used to perform high-temperature pyrolysis on the graphite surface to generate active carbon atoms. The active carbon atoms fill the defects of the graphite and improve the crystallinity. Compared with direct annealing, toluene cracking provides a self-repairing mechanism, making the hexagonal lattice of the graphite more complete and reducing defects and vacancies. On this basis, annealing is performed to rearrange the carbon atoms inside the graphite. This rearrangement can significantly reduce the defects inside the material and make its structure more inclined to a highly ordered graphite sheet structure, thereby reducing phonon scattering and reducing interfacial thermal resistance, significantly improving the thermal conductivity of the thermally conductive filler. The surface-modified siloxane structure improves its dispersion performance in the composite polyvinyl chloride, and the epoxy groups distributed on the surface react with the free radicals generated during the melt extrusion of the polyvinyl chloride, so that the thermally conductive filler is stably dispersed inside the modified heat-conducting pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 It is a schematic structural diagram of the present invention as a whole;

[0045] In the figure: 1. Wire core layer; 2. Insulation layer; 3. Heat exchange layer; 4. Heat locking layer; 5. Sheath layer. DETAILED DESCRIPTION

[0046] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] Example 1

[0048] This embodiment provides a method for preparing modified glass fiber for preparing cables for liquid-cooled high-power charging piles, comprising the following steps:

[0049] Step ①: Preparation of etched fiber

[0050] Weigh: 100.0g of glass fiber and 1000.0mL of 3wt% sodium hydroxide aqueous solution are added to the reactor and stirred at a stirring rate of 60rpm. The temperature of the reactor is raised to 60°C and kept warm for 1h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is filtered to collect the filter cake, and the filter cake is washed with ethanol 3 times. The filter cake is transferred to a vacuum drying oven and vacuum dried to constant weight to obtain the etched fiber.

[0051] Step 2: Preparation of modified glass fiber

[0052] Weigh 100.0 g of 3-isocyanatepropyltrimethoxysilane and 500.0 mL of N,N-dimethylformamide and mix to obtain a modified solution;

[0053] Weigh: 400.0g of etched fiber, 50.0g of triethylamine and 1500.0mL of N,N-dimethylformamide and add them to the reactor, introduce nitrogen protection, add 800.0mL of modification liquid to the reactor, react for 40 minutes, after the reaction is completed, wait for the temperature of the reactor to drop to room temperature, filter the reaction liquid to collect the filter cake, wash the filter cake with ethanol 3 times, transfer the filter cake to a vacuum drying oven and vacuum dry it to constant weight to obtain modified glass fiber.

[0054] Example 2

[0055] This embodiment provides a method for preparing modified glass fiber for preparing cables for liquid-cooled high-power charging piles, comprising the following steps:

[0056] Step ①: Preparation of etched fiber

[0057] Weigh: 200.0g of glass fiber and 1500.0mL of 5wt% sodium hydroxide aqueous solution are added to the reactor and stirred at a stirring rate of 80rpm. The temperature of the reactor is raised to 80℃ and kept warm for 2h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is filtered to collect the filter cake, and the filter cake is washed with ethanol 5 times. The filter cake is transferred to a vacuum drying oven and vacuum dried to constant weight to obtain the etched fiber.

[0058] Step 2: Preparation of modified glass fiber

[0059] Weigh 200.0 g of 3-isocyanatepropyltrimethoxysilane and 500.0 mL of N,N-dimethylformamide and mix to obtain a modified solution;

[0060] Weigh: 500.0g of etched fiber, 80.0g of triethylamine and 1800.0mL of N,N-dimethylformamide and add them to the reactor, introduce nitrogen protection, add 1000.0mL of modification liquid to the reactor, react for 60 minutes, after the reaction is completed, wait for the temperature of the reactor to drop to room temperature, filter the reaction liquid to collect the filter cake, wash the filter cake with ethanol twice, transfer the filter cake to a vacuum drying oven and vacuum dry it to constant weight to obtain modified glass fiber.

[0061] Example 3

[0062] This embodiment provides a method for preparing modified glass fiber for preparing cables for liquid-cooled high-power charging piles, comprising the following steps:

[0063] Step ①: Preparation of etched fiber

[0064] Weigh: 150.0g of glass fiber and 1200.0mL of 4wt% sodium hydroxide aqueous solution are added to the reactor and stirred at a stirring rate of 70rpm. The temperature of the reactor is raised to 70°C and kept warm for 2h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, the reaction liquid is filtered to collect the filter cake, and the filter cake is washed with ethanol 4 times. The filter cake is transferred to a vacuum drying oven and vacuum dried to constant weight to obtain the etched fiber.

[0065] Step 2: Preparation of modified glass fiber

[0066] Weigh 150.0 g of 3-isocyanatepropyltrimethoxysilane and 500.0 mL of N,N-dimethylformamide and mix to obtain a modified solution;

[0067] Weigh: 450.0g of etched fiber, 70.0g of triethylamine and 1600.0mL of N,N-dimethylformamide and add them to the reactor, introduce nitrogen protection, add 900.0mL of modification liquid to the reactor, react for 50 minutes, after the reaction is completed, wait for the temperature of the reactor to drop to room temperature, filter the reaction liquid to collect the filter cake, wash the filter cake with ethanol 4 times, transfer the filter cake to a vacuum drying oven and vacuum dry it to constant weight to obtain modified glass fiber.

[0068] Example 4

[0069] This embodiment provides a method for preparing a composite fiber cloth for preparing a cable for a liquid-cooled high-power charging pile, comprising the following steps:

[0070] Step I: Preparation of glass fiber gel

[0071] Weigh 200.0 g of aluminum isopropoxide, 1000.0 mL of ethanol, and 100.0 g of sodium hydroxide powder to prepare a hydrolysis aid.

[0072] 400.0 g of aluminum chloride hexahydrate, 600.0 g of methyl orthosilicate, and 4000.0 mL of deionized water were weighed and added to a reactor at a stirring rate of 60 rpm. After stirring at room temperature for 10 min, 1200.0 mL of a hydrolysis aid and 800.0 g of the modified glass fiber prepared in Example 1 were added to the reactor, and stirring was continued for 30 min to obtain a glass fiber gel.

[0073] Step II: Preparation of composite fiber cloth

[0074] Weigh: Transfer the glass fiber gel into a mold, take an aluminum foil of the same shape and size as the mold, and coat one side of it with 8wt% sodium hydroxide aqueous solution, then attach the coated side of the aluminum foil to the surface of the glass fiber gel. After treating the mold at a constant temperature of 30°C for 40 minutes, transfer the mold to a vacuum drying oven at a temperature of 80°C, vacuum dry until no liquid is extracted, and demold to obtain a composite fiber cloth.

[0075] Example 5

[0076] This embodiment provides a method for preparing a composite fiber cloth for preparing a cable for a liquid-cooled high-power charging pile, comprising the following steps:

[0077] Step I: Preparation of glass fiber gel

[0078] Weigh 300.0 g of aluminum isopropoxide, 1200.0 mL of ethanol, and 200.0 g of sodium hydroxide powder to prepare a hydrolysis aid;

[0079] 500.0 g of aluminum chloride hexahydrate, 800.0 g of methyl orthosilicate, and 5000.0 mL of deionized water were weighed and added to a reactor at a stirring rate of 80 rpm. After stirring at room temperature for 15 min, 1600.0 mL of a hydrolysis aid and 1000.0 g of the modified glass fiber prepared in Example 2 were added to the reactor, and stirring was continued for 40 min to obtain a glass fiber gel.

[0080] Step II: Preparation of composite fiber cloth

[0081] Weigh: Transfer the glass fiber gel into a mold, take an aluminum foil of the same shape and size as the mold, and coat one side of it with a 10 wt% sodium hydroxide aqueous solution, then attach the coated side of the aluminum foil to the surface of the glass fiber gel. After treating the mold at a constant temperature of 50°C for 60 minutes, transfer the mold to a vacuum drying oven at a temperature of 100°C, vacuum dry until no liquid is extracted, and demold to obtain a composite fiber cloth.

[0082] Example 6

[0083] This embodiment provides a method for preparing a composite fiber cloth for preparing a cable for a liquid-cooled high-power charging pile, comprising the following steps:

[0084] Step I: Preparation of glass fiber gel

[0085] Weigh 250.0 g of aluminum isopropoxide, 1100.0 mL of ethanol, and 150.0 g of sodium hydroxide powder to prepare a hydrolysis aid.

[0086] 450.0 g of aluminum chloride hexahydrate, 700.0 g of methyl orthosilicate, and 4500.0 mL of deionized water were weighed and added to a reactor at a stirring rate of 70 rpm. After stirring at room temperature for 12 min, 1500.0 mL of a hydrolysis aid and 900.0 g of the modified glass fiber prepared in Example 3 were added to the reactor, and stirring was continued for 35 min to obtain a glass fiber gel.

[0087] Step II: Preparation of composite fiber cloth

[0088] Weigh: Transfer the glass fiber gel into a mold, take an aluminum foil of the same shape and size as the mold, and coat one side of it with 9wt% sodium hydroxide aqueous solution, then attach the coated side of the aluminum foil to the surface of the glass fiber gel. After treating the mold at a constant temperature of 40°C for 50 minutes, transfer the mold to a vacuum drying oven at a temperature of 90°C, vacuum dry until no liquid is extracted, and demold to obtain a composite fiber cloth.

[0089] Example 7

[0090] This embodiment provides a method for preparing a thermally conductive filler for preparing a cable for a liquid-cooled high-power charging pile, comprising the following steps:

[0091] Step (1): preparing pyrolytic graphite

[0092] The graphite was transferred to a heated vacuum furnace at a temperature of 2000°C and kept at that temperature for 4 minutes. Toluene gas was then introduced into the reactor and kept at that temperature for 20 minutes. The reactor was then naturally cooled to room temperature to obtain pyrolytic graphite.

[0093] Step (2): preparing annealed graphite

[0094] The pyrolytic graphite was transferred to a heating vacuum furnace at 2800°C, and nitrogen was introduced to maintain the internal pressure of the heating vacuum furnace at 6 MPa. After the heat treatment for 40 minutes, the temperature was cooled to room temperature at a cooling rate of 3 min°C / min to obtain annealed graphite.

[0095] Step (3): preparing activated annealed graphite

[0096] The annealed graphite was evenly coated on a quartz wafer and then transferred to a plasma treatment device. The vacuum pump was turned on to extract the chamber gas so that the vacuum degree was less than 10 mTorr. Then, the gas control system was turned on and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. The instrument power was set to 50 W, the mixed gas flow rate was 100 sccm, and the pressure was 100 mTorr. Then, the RF power supply was turned on. After treating at room temperature for 3 minutes, the RF power supply was turned off and argon was introduced for 1 minute to obtain activated annealed graphite.

[0097] Step (4) Preparation of thermally conductive filler

[0098] Weigh: 800.0g activated annealed graphite, 200.0g ethanol, 200.0mL saturated sodium hydroxide solution and 4000.0mL deionized water, add them into the reactor and introduce nitrogen protection. After the temperature of the reactor is reduced to 5°C, 300.0g 3-(2,3-epoxypropoxy)propyltrimethoxysilane is added to the reactor and kept warm for 20 minutes. After the reaction is completed, the temperature of the reactor is reduced to room temperature, the reaction liquid is filtered to collect the filter cake, the filter cake is washed with ethanol 3 times, and then the filter cake is transferred to a vacuum drying oven and vacuum dried to constant weight to obtain a thermal conductive filler.

[0099] Example 8

[0100] This embodiment provides a method for preparing a thermally conductive filler for preparing a cable for a liquid-cooled high-power charging pile, comprising the following steps:

[0101] Step (1): preparing pyrolytic graphite

[0102] The graphite was transferred to a heated vacuum furnace at a temperature of 2000° C. and kept warm for 5 minutes. Toluene gas was then introduced into the reactor and kept warm for 30 minutes. The reactor was then naturally cooled to room temperature to obtain pyrolytic graphite.

[0103] Step (2): preparing annealed graphite

[0104] The pyrolytic graphite was transferred to a heating vacuum furnace at 3100°C, and nitrogen was introduced to maintain the internal pressure of the heating vacuum furnace at 8 MPa. After heat treatment for 60 minutes, the temperature was cooled to room temperature at a cooling rate of 4 min°C / min to obtain annealed graphite.

[0105] Step (3): preparing activated annealed graphite

[0106] The annealed graphite was evenly coated on a quartz wafer and then transferred to a plasma treatment device. The vacuum pump was turned on to extract the chamber gas until the vacuum degree was less than 10 mTorr. Then, the gas control system was turned on and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. The instrument power was set to 80 W, the mixed gas flow rate was 150 sccm, and the pressure was 150 mTorr. Then, the RF power supply was turned on. After treating at room temperature for 5 minutes, the RF power supply was turned off and argon was introduced for 2 minutes to obtain activated annealed graphite.

[0107] Step (4) Preparation of thermally conductive filler

[0108] Weigh: 1000.0g activated annealed graphite, 300.0g ethanol, 300.0mL saturated sodium hydroxide solution and 6000.0mL deionized water, add them into the reactor and introduce nitrogen protection. After the temperature of the reactor is reduced to 10°C, 500.0g 3-(2,3-epoxypropoxy)propyltrimethoxysilane is added to the reactor and kept warm for 30 minutes. After the reaction is completed, the temperature of the reactor is reduced to room temperature, the reaction liquid is filtered to collect the filter cake, the filter cake is washed with ethanol 5 times, and then the filter cake is transferred to a vacuum drying oven and vacuum dried to constant weight to obtain a thermal conductive filler.

[0109] Example 9

[0110] This embodiment provides a method for preparing a thermally conductive filler for preparing a cable for a liquid-cooled high-power charging pile, comprising the following steps:

[0111] Step (1): preparing pyrolytic graphite

[0112] The graphite was transferred to a heated vacuum furnace at a temperature of 2000° C. and kept warm for 5 minutes. Toluene gas was then introduced into the reactor and kept warm for 30 minutes. The reactor was then naturally cooled to room temperature to obtain pyrolytic graphite.

[0113] Step (2): preparing annealed graphite

[0114] The pyrolytic graphite was transferred to a heating vacuum furnace at 3000°C, and nitrogen was introduced to maintain the internal pressure of the heating vacuum furnace at 7 MPa. After heat treatment for 50 minutes, the temperature was cooled to room temperature at a cooling rate of 4 min°C / min to obtain annealed graphite.

[0115] Step (3): preparing activated annealed graphite

[0116] The annealed graphite was evenly coated on a quartz wafer and then transferred to a plasma treatment device. The vacuum pump was turned on to extract the chamber gas until the vacuum degree was less than 10 mTorr. Then, the gas control system was turned on and a mixed gas of argon and oxygen with a volume ratio of 4:1 was introduced. The instrument power was set to 70 W, the mixed gas flow rate was 120 sccm, and the pressure was 120 mTorr. Then, the RF power supply was turned on. After treating at room temperature for 4 minutes, the RF power supply was turned off and argon was purged for 2 minutes to obtain activated annealed graphite.

[0117] Step (4) Preparation of thermally conductive filler

[0118] Weigh: 900.0g activated annealed graphite, 250.0g ethanol, 250.0mL saturated sodium hydroxide solution and 5000.0mL deionized water, add them into the reactor and introduce nitrogen protection. After the temperature of the reactor is reduced to 8°C, 400.0g 3-(2,3-epoxypropoxy)propyltrimethoxysilane is added to the reactor and kept warm for 25 minutes. After the reaction is completed, the temperature of the reactor is reduced to room temperature, the reaction liquid is filtered to collect the filter cake, the filter cake is washed with ethanol 4 times, and then the filter cake is transferred to a vacuum drying oven and vacuum dried to constant weight to obtain a thermal conductive filler.

[0119] Example 10

[0120] This embodiment provides a method for preparing a cable for a liquid-cooled high-power charging pile, comprising the following steps:

[0121] Step 1: Preparation of modified heat pipe

[0122] 3000.0 g of polyvinyl chloride, 3000.0 g of the thermal conductive filler prepared in Example 7, 500.0 g of dioctyl phthalate, 200.0 g of calcium stearate, 50.0 g of oxidized polyethylene wax, 30.0 g of epoxy soybean oil, and 50.0 g of polyvinyl alcohol were weighed and added to a twin-screw extruder. The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port were 170° C., 185° C., 185° C., 190° C., 190° C., 200° C., 200° C., and 210° C., respectively. The main engine speed of the twin-screw extruder was 80 rpm, and the pressure was 100 bar. The melt-extruded coating was applied to a mold, and the mold was cured and demolded to obtain a modified heat pipe.

[0123] Step 2: Prepare the core layer

[0124] The positive and negative cores in the dual-core power line are split into two respectively, and two positive and two negative cores are spirally wound on the surface of a single modified heat conducting pipe to obtain a line core layer 1.

[0125] Step 3: Prepare the insulation layer

[0126] The insulating layer 2 is formed by wrapping the surface of the wire core layer with a polyvinyl chloride wrapping tape.

[0127] Step 4: Prepare the heat exchange layer

[0128] A plurality of modified heat-conducting pipes are spirally arranged on the surface of the insulation layer to obtain a heat exchange layer 3.

[0129] Step 5: Prepare the heat-locking layer

[0130] The composite fiber cloth prepared in Example 4 is wrapped around the surface 3 of the heat exchange layer and fixed to obtain the heat locking layer 4 .

[0131] Step 6: Prepare liquid cooling cable

[0132] Weigh: 7000.0g of polypropylene, 500.0g of dioctyl phthalate, 20.0g of tris(2,4-di-tert-butylphenyl) phosphate, 20.0g of 2-hydroxy-4-octyloxybenzophenone, 500.0g of epoxy soybean oil, 500.0g of calcium carbonate and 50.0g of oxidized polyethylene wax and add them to a twin-screw extruder. The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 200°C, 215°C, 215°C, 220°C, 220°C, 230°C, 230°C, and 240°C, respectively. The main engine speed of the twin-screw extruder is 80rpm, the pressure is 100bar, and the melt extrusion is coated on the surface of the heat-locking layer 4. After curing, the sheath layer 5 is obtained, thereby obtaining a liquid-cooled cable.

[0133] Example 11

[0134] This embodiment provides a method for preparing a cable for a liquid-cooled high-power charging pile, comprising the following steps:

[0135] Step 1: Preparation of modified heat pipe

[0136] Weigh 5000.0 g of polyvinyl chloride, 5000.0 g of the thermal conductive filler prepared in Example 8, 1000.0 g of dioctyl phthalate, 500.0 g of calcium stearate, 200.0 g of oxidized polyethylene wax, 1000.0 g of epoxy soybean oil, and 200.0 g of polyvinyl alcohol and add them to a twin-screw extruder. The temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 170° C., 185° C., 185° C., 190° C., 190° C., 200° C., 200° C., and 210° C., respectively. The main engine speed of the twin-screw extruder is 120 rpm, the pressure is 150 bar, and the melt-extrusion coating is applied to a mold, and the mold is cured and demolded to obtain a modified heat pipe.

[0137] Step 2: Prepare the core layer

[0138] The positive and negative cores in the dual-core power line are split into two respectively, and two positive and two negative spirals are wound on the surface of a single modified heat conducting pipe to obtain a line core layer 1.

[0139] Step 3: Prepare the insulation layer

[0140] The insulating layer 2 is formed by wrapping the surface of the wire core layer with a polyvinyl chloride wrapping tape.

[0141] Step 4: Prepare the heat exchange layer

[0142] A plurality of modified heat-conducting pipes are spirally arranged on the surface of the insulation layer to obtain a heat exchange layer 3.

[0143] Step 5: Prepare the heat-locking layer

[0144] The composite fiber cloth prepared in Example 5 is wrapped on the surface 3 of the heat exchange layer and fixed to obtain the heat locking layer 4 .

[0145] Step 6: Prepare liquid cooling cable

[0146] Weigh: 7500.0g polypropylene, 1000.0g dioctyl phthalate, 100.0g tris(2,4-di-tert-butylphenyl) phosphate, 200.0g 2-hydroxy-4-octyloxybenzophenone, 1000.0g epoxy soybean oil, 1000.0g calcium carbonate and 200.0g oxidized polyethylene wax and add them to a twin-screw extruder. The temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 200°C, 215°C, 215°C, 220°C, 220°C, 230°C, 230°C, and 240°C, respectively. The main engine speed of the twin-screw extruder is 120rpm, the pressure is 150 bar, and the melt extrusion is coated on the surface of the heat-locking layer 4. After curing, the sheath layer 5 is obtained, thereby obtaining a liquid-cooled cable.

[0147] Example 12

[0148] This embodiment provides a method for preparing a cable for a liquid-cooled high-power charging pile, comprising the following steps:

[0149] Step 1: Preparation of modified heat pipe

[0150] 4000.0 g of polyvinyl chloride, 4000.0 g of the thermal conductive filler prepared in Example 9, 800.0 g of dioctyl phthalate, 300.0 g of calcium stearate, 100.0 g of oxidized polyethylene wax, 500.0 g of epoxy soybean oil, and 100.0 g of polyvinyl alcohol were weighed and added to a twin-screw extruder. The temperatures of the eight temperature zones of the twin-screw extruder from the feed inlet to the discharge outlet were 170° C., 185° C., 185° C., 190° C., 190° C., 200° C., 200° C., and 210° C., respectively. The main engine speed of the twin-screw extruder was 100 rpm, and the pressure was 120 bar. The melt-extruded material was coated on a mold, cured, and demolded to obtain a modified heat pipe.

[0151] Step 2: Prepare the core layer

[0152] The positive and negative cores in the dual-core power line are split into two respectively, and two positive and two negative spirals are wound on the surface of a single modified heat conducting pipe to obtain a line core layer 1.

[0153] Step 3: Prepare the insulation layer

[0154] The insulating layer 2 is formed by wrapping the surface of the wire core layer with a polyvinyl chloride wrapping tape.

[0155] Step 4: Prepare the heat exchange layer

[0156] A plurality of modified heat-conducting pipes are spirally arranged on the surface of the insulation layer to obtain a heat exchange layer 3.

[0157] Step 5: Prepare the heat-locking layer

[0158] The composite fiber cloth prepared in Example 6 is wrapped on the surface 3 of the heat exchange layer and fixed to obtain the heat locking layer 4 .

[0159] Step 6: Prepare liquid cooling cable

[0160] Weigh: 7200.0g of polypropylene, 800.0g of dioctyl phthalate, 50.0g of tris(2,4-di-tert-butylphenyl) phosphate, 100.0g of 2-hydroxy-4-octyloxybenzophenone, 800.0g of epoxy soybean oil, 800.0g of calcium carbonate and 100.0g of oxidized polyethylene wax and add them to a twin-screw extruder. The temperatures of the eight temperature sections of the twin-screw extruder from the feed port to the discharge port are 200°C, 215°C, 215°C, 220°C, 220°C, 230°C, 230°C, and 240°C, respectively. The main engine speed of the twin-screw extruder is 100rpm, the pressure is 120 bar, and the melt extrusion is coated on the surface of the heat-locking layer 4. After curing, the sheath layer 5 is obtained, thereby obtaining a liquid-cooled cable.

[0161] Comparative Example 1

[0162] The difference between this comparison and comparative example 12 is that, in the preparation process of the thermally conductive filler used in step 1, step ⑵ is omitted, and in step ⑶, an equal amount of pyrolytic graphite is used instead of annealed graphite.

[0163] Comparative Example 2

[0164] The difference between this comparison and comparative example 12 is that, during the preparation process of the thermally conductive filler used in step 1, step 4 is omitted, and an equal amount of activated annealed graphite is used to replace the thermally conductive filler.

[0165] Comparative Example 2

[0166] The difference between this comparison and Comparative Example 12 is that, during the preparation of the composite fiber cloth used in step 5, step I is omitted, and the glass fiber gel is prepared by doping an equal amount of modified glass fiber into bisphenol A epoxy resin.

[0167] Performance testing:

[0168] The flame retardancy grade of liquid-cooled cables is determined with reference to the standard GB / T 19666-2019 "General Rules for Flame-Retardant and Fire-Resistant Wires, Cables or Optical Cables";

[0169] The thermal conductivity of the modified heat pipes prepared in Examples 10-12 and Comparative Examples 1-3 was tested with reference to the standard GB / T 10297-2015 “Determination of thermal conductivity of non-metallic solid materials - Hot wire method”;

[0170] The thermal conductivity of the composite fiber cloths prepared in Examples 4-6 and Comparative Examples 1-3 was tested with reference to the standard GB / T 10297-2015 “Determination of thermal conductivity of non-metallic solid materials - Hot wire method”;

[0171] The fire resistance of the liquid-cooled cables prepared in Examples 10-12 and Comparative Examples 1-3 was tested with reference to the standard XF 306.2-2007 "Classification and requirements of flame-retardant and fire-resistant cables with plastic insulation Part 2: Fire-resistant cables".

[0172] The liquid-cooled cables of the lightweight cables prepared in Examples 10-12 and Comparative Examples 1-3 were tested with reference to the standard GB / T 32511-2016 “General Technical Requirements for Electromagnetic Shielding Plastics”. Specific data are shown in Table 1.

[0173] Table 1 - Performance test data of each sample

[0174] Project Group Example 10 Example 11 Example 12 Comparative Example 1 Comparative Example 2 Comparative Example 3 Flame retardant grade / level ⅠA ⅠA ⅠA ⅠA ⅠA ⅠB <![CDATA[Thermal conductivity of modified heat pipe / W·(m·K) -1 > 4.1254 4.1742 4.2152 1.5625 3.6451 - <![CDATA[Thermal conductivity of composite fiber cloth / W·(m·K) -1 > 0.1154 0.1143 0.1139 - - 0.4832 Fire resistance grade / level ⅠA ⅠA ⅠA ⅠA ⅠA ⅠB Anti-electromagnetic interference performance / level SE-1 SE-1 SE-1 SE-2 SE-1 SE-2

[0175] Data Analysis:

[0176] Comparing and analyzing the data in Table 1, it is found that the flame retardant grade of the liquid cooling cable prepared by the present invention is IA, the fire resistance grade is IA, and the anti-electromagnetic interference performance is SE-1. The thermal conductivity of the modified heat pipe is W·(m·K) -1 , the thermal conductivity of composite fiber cloth is W·(m·K) -1 "-" means that the sample was not tested, and all the data are better than the comparative example;

[0177] Description: In the present invention, toluene gas is first used to perform high-temperature pyrolysis on the graphite surface to generate active carbon atoms. The active carbon atoms fill the defects of the graphite and improve the crystallinity. Compared with direct annealing, toluene cracking provides a self-repairing mechanism, making the hexagonal lattice of the graphite more complete and reducing defects and vacancies. On this basis, annealing is performed to rearrange the carbon atoms inside it. This rearrangement can significantly reduce the defects inside the material and make its structure more inclined to a highly ordered graphite sheet structure, thereby reducing phonon scattering and reducing interfacial thermal resistance, thereby significantly improving the thermal conductivity of the thermally conductive filler. The surface-modified siloxane structure improves its dispersion performance in the composite polyvinyl chloride, and the epoxy groups distributed on the surface react with the free radicals generated during the melt extrusion of polyvinyl chloride, so that the thermally conductive filler is stably dispersed inside the modified heat-conducting pipe.

[0178] Description: The present invention etches the surface of the glass fiber, thereby significantly improving the activity of the glass fiber. On this basis, a silane coupling agent is used to modify the surface of the glass fiber, so that it participates in the hydrolysis process of aluminum chloride hexahydrate, methyl orthosilicate and aluminum isopropylate, so that the glass fiber is evenly dispersed inside the hydrolysis gel. While using the glass fiber to improve the heat resistance of the composite fiber cloth, its surface is modified to reduce the damage of the fiber structure to the heat pipe. The surface of the aluminum foil is further activated by an aqueous sodium hydroxide solution. Under alkaline catalysis, the hydroxyl structure on the surface of the activated aluminum foil and the active structure on the surface of the glass fiber gel are hydrolyzed to form a stable cross-linked structure to obtain a composite fiber cloth. The composite fiber cloth locks heat inside during the operation of the cable, so that the heat generated by the core layer is evenly distributed and slowly transferred to the outer sheath, thereby reducing the negative impact of internal heat on the service life of the cable.

[0179] It is explained that the liquid-cooled cable prepared in the present invention uses the modified heat-conducting pipe with high internal thermal conductivity and the heat-locking composite fiber cloth to carry away the heat generated by the core layer through the internal coolant circulation, thereby reducing the impact of internal heat on the cable life. During the combustion process, the protective layer structure generated by the decomposition of the glass fiber and silicon-aluminum structure of the composite fiber cloth at high temperature isolates the heat transfer and the spread of the flame, ensuring the structural integrity of the heat-conducting pipe, thereby carrying away the heat of the flame through the coolant circulation, protecting the core layer and the insulation layer, and avoiding the occurrence of secondary combustion caused by coolant leakage. The coordinated cooperation of the modified heat-conducting pipe and the composite fiber cloth significantly improves the fire resistance and flame retardant properties of the liquid-cooled cable, and the multiple reflection effect brought by the multi-layer structure of annealed graphite and the coordinated cooperation of the aluminum foil attached to the surface of the composite fiber cloth significantly increase the shielding performance of the cable, so that electromagnetic waves in a wider frequency range can be effectively shielded, thereby significantly improving the thermal conductivity and anti-electromagnetic interference performance of the thermal conductive filler.

[0180] The above contents are merely examples and explanations of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they shall fall within the scope of protection of the present invention.

[0181] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0182] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention.

[0183] Although all details are described, it is not intended to limit the invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification in order to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a cable for a liquid-cooled high-power charging pile, characterized in that: The following steps are involved: S1. Split the positive and negative cores of the dual-core power line into two, and use two positive and two negative spirals to wrap them on the surface of a single modified heat pipe to obtain a core layer (1); S2, wrapping the surface of the wire core layer with a polyvinyl chloride wrapping tape to obtain an insulation layer (2); S3, using a plurality of modified heat conducting pipes to be spirally arranged on the surface of the insulation layer to obtain a heat exchange layer (3); S4, wrapping the surface of the heat exchange layer (3) with composite fiber cloth and fixing it to obtain a heat locking layer (4); S5, using a composite polypropylene material to melt-extrude and coat the surface of the heat-locking layer (4), and obtaining a sheath layer (5) after solidification, thereby obtaining a liquid-cooled cable; In step S1, the modified heat-conducting pipe is obtained by melt-extruding a composite polyvinyl chloride material, coating it on a mold, and curing and demolding it; the composite polyvinyl chloride material includes the following raw materials in parts by weight: 30-50 parts of polyvinyl chloride, 30-50 parts of thermally conductive filler, 5-10 parts of plasticizer, 2-5 parts of heat stabilizer, 0.5-2 parts of lubricant, 3-10 parts of anti-impact agent, and 0.5-2 parts of dispersant; in step S5, the composite polypropylene material includes the following raw materials in parts by weight: 70-75 parts of polypropylene, 5-10 parts of plasticizer, 0.2-1 part of antioxidant, 0.2-2 parts of light stabilizer, 5-10 parts of anti-impact agent, 5-10 parts of filler, and 0.5-2 parts of lubricant; The preparation method of the thermally conductive filler comprises the following steps: A1. Transfer the graphite to a vacuum furnace at 2000°C and keep it at that temperature for 4-5 minutes. Then, introduce toluene gas into the reactor and keep it at that temperature for 20-30 minutes. Then, naturally cool it to room temperature to obtain pyrolytic graphite. A2. Transfer the pyrolytic graphite to a heated vacuum furnace at 2800-3100°C, introduce nitrogen, maintain the internal pressure of the heated vacuum furnace at 6-8 MPa, hold the temperature for 40-60 minutes, and then cool it to room temperature at a cooling rate of 3-4 min°C / min to obtain annealed graphite; A3, using plasma to modify annealed graphite to obtain activated annealed graphite; A4. Add activated annealed graphite, ethanol, saturated sodium hydroxide solution, and deionized water to a reactor. After nitrogen protection, reduce the temperature of the reactor to 5-10°C, add 3-(2,3-epoxypropoxy)propyltrimethoxysilane to the reactor, keep the temperature for 20-30 minutes, and perform post-processing to obtain a thermally conductive filler. The preparation method of the composite fiber cloth comprises the following steps: B1. Aluminum chloride hexahydrate, methyl orthosilicate, and deionized water are added to a reactor, stirred at room temperature for 10-15 minutes, and then a hydrolysis aid and modified glass fiber are added to the reactor, and stirring is continued for 30-40 minutes to obtain a glass fiber gel; B2. Transfer the glass fiber gel to a mold. Take an aluminum foil of the same shape and size as the mold, coat one side of the aluminum foil with 8-10 wt% sodium hydroxide aqueous solution, and then attach the coated side of the aluminum foil to the surface of the glass fiber gel. Treat the mold at a constant temperature of 30-50°C for 40-60 minutes, and then post-treat to obtain a composite fiber cloth. The preparation method of the modified glass fiber comprises the following steps: C1. Add glass fiber and 3-5 wt% sodium hydroxide aqueous solution into a reactor and stir. Raise the temperature of the reactor to 60-80°C, keep the temperature for 1-2 hours, and perform post-processing to obtain etched fiber. C2. Add the etched fiber, triethylamine and N,N-dimethylformamide into the reactor, introduce nitrogen protection, add the modification liquid into the reactor, react for 40-60 minutes, and post-treat to obtain the modified glass fiber.

2. The method for preparing a cable for a liquid-cooled high-power charging pile according to claim 1, characterized in that: In step A4, the ratio of activated annealed graphite, ethanol, saturated sodium hydroxide solution, deionized water and 3-(2,3-epoxypropoxy)propyltrimethoxysilane is 8-10 g:2-3 g:2-3 mL:40-60 mL:3-5 g.

3. The method for preparing a cable for a liquid-cooled high-power charging pile according to claim 1, characterized in that: In step B1, the amount ratio of aluminum chloride hexahydrate, methyl orthosilicate, deionized water, auxiliary agent and modified glass fiber is 4-5g:6-8g:40-50mL:12-16mL:8-10g, and the hydrolysis auxiliary agent is aluminum isopropoxide, ethanol and sodium hydroxide powder in the amount ratio of 2-3g:10-12mL:1-2g.

4. The method for preparing a cable for a liquid-cooled high-power charging pile according to claim 1, characterized in that: In step C1, the ratio of glass fiber and 3-5wt% sodium hydroxide aqueous solution is 1-2g:10-15mL; in step C2, the ratio of etching microspheres, triethylamine, N,N-dimethylformamide and modification liquid is 4-5g:0.5-0.8g:15-18mL:8-10mL, and the modification liquid is 3-isocyanatepropyltrimethoxysilane and N,N-dimethylformamide mixed in a ratio of 1-2g:5mL.

5. Application of a cable for a liquid-cooled high-power charging pile, characterized in that: The liquid-cooled cable prepared by the method for preparing a cable for a liquid-cooled high-power charging pile according to any one of claims 1 to 4 is applied to electric vehicle fast charging piles and electric commercial vehicle charging.

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