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

Abstract

The invention discloses a preparation method and application of a cable for a liquid-cooled high-power charging pile, belongs to the technical field of liquid-cooled cables, and aims to solve the technical problem that the flame retardance and fire resistance of a liquid-cooled cable in the prior art need to be further improved. The method comprises the following steps that a plurality of modified heat conduction pipes are spirally arranged on the surface of an insulating layer to obtain a heat exchange layer, the liquid-cooled cable has excellent fire resistance and flame retardance through the collaborative design of composite fiber cloth and the modified heat conduction pipes, glass fibers and a silicon-aluminum structure in the composite fiber cloth are decomposed at the high temperature, and the heat exchange layer is formed; the insulating layer is arranged on the insulating layer, a protective layer is formed, heat transfer and flame spreading are effectively blocked, the structural integrity of the heat conduction pipe is ensured, meanwhile, a cooling liquid circulating system rapidly takes away flame heat, the wire core layer and the insulating layer are further protected, and the secondary combustion phenomenon caused by leakage of organic cooling liquid is avoided.

Description

Technical Field

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

[0002] Under the optimization of heat conduction tubes and heat insulation layers, the heat dissipation efficiency and safety performance of liquid-cooled cables for high-power charging piles are continuously improved to meet the high-power charging requirements. In the early stage, copper and aluminum heat conduction tubes and foam and silica gel heat insulation layers were used for heat management, but the heat dissipation effect was limited. With the increase of charging power, composite heat conduction tubes and micro-channel liquid-cooling technologies were gradually introduced to improve the heat exchange efficiency. Currently, nano-thermal conductive materials and multi-channel composite materials are used to enable the cable to still dissipate heat efficiently in a high-voltage charging environment above 800V. At the same time, the heat insulation layer has developed from basic foam insulation to halogen-free and low-smoke composite materials, improving high-temperature resistance and safety. Currently, ceramic fiber and carbon fiber composite materials combined with an intelligent temperature control system can more accurately control the temperature and prevent overheating risks. Generally speaking, the continuous optimization of heat conduction tubes and heat insulation layers makes liquid-cooled cables safer and more efficient, providing a guarantee for the development of ultra-high-power charging technology.

[0003] The prior art CN118782313A discloses a wear-resistant liquid-cooled cable for ultra-large current loads in new energy, including a plurality of conductors. An insulating layer, a shielding layer, and an outer sheath layer are sequentially arranged outside the plurality of conductors. A heat exchange layer composed of a plurality of heat exchange tubes is arranged between the shielding layer and the outer sheath layer. The plurality of heat exchange tubes are all arranged in a spiral shape. The heat exchange performance inside the cable is improved by using a heat-conductive filler to prepare the insulating layer, and the adiabatic and wear-resistant performance of the cable outer sheath layer is improved by synthesizing a composite polyolefin to obtain a liquid-cooled cable with high heat exchange efficiency inside, wear-resistant outside, and suitable for high temperatures.

[0004] However, the above patent improves the heat exchange efficiency of the liquid-cooled cable by enhancing the heat conduction performance of the insulating layer and the heat insulation performance of the outer sheath layer. However, the outer sheath layer is directly in contact with the heat conduction tube. During the combustion process, the generated heat and flame will quickly transfer to the heat exchange layer, causing the liquid-cooled cable to burn rapidly. Since this structure does not protect the heat exchange layer, when the cooling tube ruptures, the spilled organic coolant may undergo secondary combustion. Therefore, the fire resistance and flame retardancy of this 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 liquid-cooled cable for high-power charging piles, aiming to solve the technical problem that the flame retardancy and fire resistance of liquid-cooled cables in the prior art need to be further improved.

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

[0007] S1. Split the positive and negative cores in the double-core power line into two respectively, and wind two positives and two negatives spirally on the surface of a single modified heat-conducting tube 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 generation of the core layer.

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

[0010] S3. Use a number of modified heat-conducting tubes to be arranged spirally on the surface of the insulating layer to obtain a heat exchange layer;

[0011] S4. Use a composite fiber cloth to wrap on the surface of the heat exchange layer, and fix it to obtain a heat-locking layer;

[0012] S5. Use a composite polypropylene material to be melt-extruded and coated on the surface of the heat-locking layer, and after curing, obtain a sheath layer, thereby obtaining a liquid-cooled cable.

[0013] Further, in step S1, the modified heat-conducting tube is obtained by melt-extruding and coating a composite polyvinyl chloride material on a mold and curing and demolding; the composite polyvinyl chloride material comprises the following raw materials in parts by weight: 30-50 parts of polypropylene, 30-50 parts of heat-conducting filler, 5-10 parts of plasticizer, 2-5 parts of heat stabilizer, 0.5-2 parts of lubricant, 3-10 parts of impact modifier and 0.5-2 parts of dispersant; in step S5, the composite polypropylene material comprises 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 modifier, 5-10 parts of filler and 0.5-2 parts of lubricant.

[0014] Further, in step S1, the preparation method of the modified heat-conducting tube comprises: adding the composite polyvinyl chloride material into a twin-screw extruder. In the twin-screw extruder, the temperatures of the eight temperature zones from the feed port to the discharge port are 170°C, 185°C, 185°C, 190°C, 190°C, 200°C, 200°C, 210°C in sequence. The main machine speed of the twin-screw extruder is 80-120 rpm, the pressure is 100-150 bar, melt-extrude and coat on the mold, cure and demold to obtain the modified heat-conducting tube;

[0015] Further, 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 modifier is one or more of epoxidized soybean oil, dioctyl terephthalate, and diisooctyl phthalate; the dispersant is one or more of polyvinyl alcohol, sodium polyacrylate, and polyethylene ether.

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

[0017] Further, 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 cetyl 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 modifier is one or more of epoxidized soybean oil, dioctyl terephthalate, and diisooctyl phthalate; the filler is one or more of calcium carbonate, talcum powder, and barium sulfate; the lubricant is one or more of calcium stearate, oxidized polyethylene wax, and montan wax.

[0018] Further, the preparation method of the heat-conducting filler includes the following steps:

[0019] A1. Transfer the graphite to a heating vacuum furnace at a temperature of 2000 °C. After keeping it warm for 4 - 5 min, introduce toluene gas into the reaction kettle. After keeping it warm for 20 - 30 min, naturally cool it to room temperature to obtain pyrolytic graphite;

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

[0021] A3. Modify the annealed graphite with plasma to obtain activated annealed graphite;

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

[0023] The reaction principle for preparing the thermal conductive filler is as follows: Through pyrolysis of toluene and annealing treatment, the hexagonal lattice of graphene becomes more complete, reducing defects and vacancies. After plasma modification, active functional groups are generated in the graphene structure, and under alkaline conditions, the siloxane segments of the silane coupling agent undergo hydrolysis, thus crosslinking on the surface of the graphene structure, thereby preparing the thermal conductive filler.

[0024] Further, in step A3, the operation of plasma modification is as follows: Uniformly coat the annealed graphite on a quartz wafer, then transfer it to a plasma treatment device. After opening the vacuum pump to extract the chamber gas and making its vacuum degree less than 10 mTorr, open the gas control system, introduce a mixed gas with a volume ratio of argon to oxygen of 4:1, set the instrument power to 50 - 80 W, the flow rate of the mixed gas to 100 - 150 sccm, and the pressure to 100 - 150 mTorr. Then turn on the radio frequency power supply, treat it at room temperature for 3 - 5 min, turn off the radio frequency power supply and introduce argon for purging for 1 - 2 min to obtain the activated annealed graphite;

[0025] Further, in step A4, the dosage ratio of the 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. The post-treatment includes: After the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature, filter the reaction solution by suction to collect the filter cake, wash the filter cake with ethanol 3 - 5 times, then transfer the filter cake to a vacuum drying oven and vacuum dry it to constant weight to obtain the thermal conductive filler.

[0026] Further, the preparation method of the composite fiber cloth includes the following steps:

[0027] B1. Add aluminum chloride hexahydrate, methyl orthosilicate, and deionized water into a reaction kettle, stir at room temperature for 10 - 15 min, then add a hydrolysis assistant and modified glass fiber into the reaction kettle, and continue to stir for 30 - 40 min to obtain a glass fiber gel;

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

[0029] The reaction principle for preparing the composite fiber cloth is as follows: Under alkaline conditions, tetraethyl orthosilicate, aluminum isopropoxide, and aluminum chloride hexahydrate hydrolyze to produce a colloidal structure. The modified glass fiber cross-links with the colloid through the siloxane structure modified on its surface to obtain a glass fiber gel, and hydrolysis cross-linking occurs between the active structure on the gel surface and the activated aluminum foil surface, finally preparing the composite fiber cloth.

[0030] Further, in step B1, the dosage ratio of aluminum chloride hexahydrate, tetraethyl orthosilicate, deionized water, auxiliary agent, and modified glass fiber is 4 - 5 g : 6 - 8 g : 40 - 50 mL : 12 - 16 mL : 8 - 10 g. The hydrolysis auxiliary agent is aluminum isopropoxide, ethanol, and sodium hydroxide powder in a dosage ratio of 2 - 3 g : 10 - 12 mL : 1 - 2 g, and the stirring rate of the reaction kettle is 60 - 80 rpm;

[0031] Further, in step B2, the post-treatment 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] Further, the preparation method of the modified glass fiber includes the following steps:

[0033] C1. Add glass fiber and 3 - 5 wt% sodium hydroxide aqueous solution to the reaction kettle and stir. Raise the temperature of the reaction kettle to 60 - 80 °C, keep the temperature for reaction for 1 - 2 h, and perform post-treatment to obtain etched fiber;

[0034] C2. Add the etched fiber, triethylamine, and N,N-dimethylformamide to the reaction kettle, introduce nitrogen for protection, add the modification liquid to the reaction kettle, react for 40 - 60 min, and perform post-treatment to obtain the modified glass fiber.

[0035] The reaction principle for preparing the modified glass fiber is as follows: Under low-alkaline conditions, active sites such as hydroxyl groups are formed on the surface of the glass fiber. Further, through the modification of the silane coupling agent, a siloxane structure is formed on the surface of the fiber structure, and finally the modified glass fiber is prepared.

[0036] Further, in step C1, the stirring rate of the reaction kettle is 60 - 80 rpm, and the dosage ratio of glass fiber and 3 - 5 wt% sodium hydroxide aqueous solution is 1 - 2 g : 10 - 15 mL. The post-treatment includes: after the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature, filter the reaction solution by suction to collect the filter cake, wash the filter cake with ethanol 3 - 5 times, and then transfer the filter cake to a vacuum drying oven for vacuum drying 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 for 3-5 times, and the filter cake is transferred to a vacuum drying oven for vacuum drying to constant weight to obtain modified glass fiber.

[0038] A liquid-cooled high-power charging pile cable is used for application. The liquid-cooled cable prepared by the preparation method of the liquid-cooled high-power charging pile cable 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 internal modified heat-conducting pipe with high thermal conductivity and the heat-locking composite fiber cloth to take 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 diffusion of the flame, ensuring the structural integrity of the heat-conducting pipe. The flame heat is taken away by the coolant circulation, while protecting the core layer and the insulating layer, avoiding the secondary combustion caused by the leakage of the coolant. The fire resistance and flame retardant properties of the liquid-cooled cable are significantly improved through the coordinated cooperation of the modified heat-conducting pipe and the composite fiber cloth. The shielding performance of the cable is significantly increased through the coordinated cooperation of the multiple reflection effect brought by the multi-layer structure of annealed graphene and the aluminum foil attached to the surface of the composite fiber cloth, 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 isopropoxide, 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 the 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 the internal heat on the service life of the cable.

[0042] 3. In the present invention, first, toluene gas is used for high-temperature pyrolysis on the surface of graphene to generate active carbon atoms. The active carbon atoms fill the defects of graphene, improving the crystallinity. Compared with direct annealing, toluene cracking provides a self-healing mechanism, making the hexagonal lattice of graphene more complete, reducing defects and vacancies. On this basis, annealing is carried out to rearrange the carbon atoms inside, and this rearrangement can significantly reduce the defects inside the material, making its structure more tend to a highly ordered graphite sheet structure, thereby reducing phonon scattering and reducing the interfacial thermal resistance, significantly improving the thermal conductivity of the thermal conductive filler, and improving its dispersion performance in the composite polyvinyl chloride through the surface-modified siloxane structure. The epoxy groups distributed on the surface react with the free radicals generated during the melt extrusion process of polyvinyl chloride, so that the thermal conductive filler is stably dispersed inside the modified heat-conducting tube. Brief Description of the Drawings

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

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

[0045] In the figure: 1. Core layer; 2. Insulating layer; 3. Heat exchange layer; 4. Heat locking layer; 5. Sheath layer. Detailed Embodiments

[0046] The following will clearly and completely describe the technical solutions of the present invention in combination with the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0047] Embodiment 1

[0048] This embodiment provides a preparation method of modified glass fiber for the preparation of a liquid-cooled high-power charging pile cable, including the following steps:

[0049] Step ①. Prepare etched fiber

[0050] Weigh: 100.0 g of glass fiber and 1000.0 mL of 3 wt% sodium hydroxide aqueous solution are added to a reaction kettle and stirred. The stirring rate of the reaction kettle is 60 rpm. The temperature of the reaction kettle is raised to 60 °C and kept warm for 1 h. After the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature. Filter the reaction solution by suction to collect the filter cake. After washing 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 etched fiber.

[0051] Step ②, Prepare modified glass fiber

[0052] Weigh: 100.0 g of 3-isocyanatopropyltrimethoxysilane and 500.0 mL of N,N-dimethylformamide are mixed to obtain a modified solution;

[0053] Weigh: 400.0 g of etched fiber, 50.0 g of triethylamine and 1500.0 mL of N,N-dimethylformamide are added to a reaction kettle, protected by nitrogen. Add 800.0 mL of the modified solution to the reaction kettle and react for 40 min. After the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature. Filter the reaction solution by suction to collect the filter cake. After washing 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 example provides a preparation method of modified glass fiber for a liquid-cooled high-power charging pile cable, including the following steps:

[0056] Step ①, Prepare etched fiber

[0057] Weigh: 200.0 g of glass fiber and 1500.0 mL of 5 wt% sodium hydroxide aqueous solution are added to a reaction kettle and stirred. The stirring rate is 80 rpm. The temperature of the reaction kettle is raised to 80 °C and kept warm for 2 h. After the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature. Filter the reaction solution by suction to collect the filter cake. After washing the filter cake with ethanol 5 times, transfer the filter cake to a vacuum drying oven and vacuum dry it to constant weight to obtain etched fiber.

[0058] Step ②, Prepare modified glass fiber

[0059] Weigh: 200.0 g of 3-isocyanatopropyltrimethoxysilane and 500.0 mL of N,N-dimethylformamide are mixed to obtain a modified solution;

[0060] Weigh: 500.0 g of etched fiber, 80.0 g of triethylamine and 1800.0 mL of N,N-dimethylformamide are added to a reaction kettle, nitrogen is introduced for protection, 1000.0 mL of modification liquid is added to the reaction kettle, and the reaction is carried out for 60 min. After the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature, filter the reaction solution by suction to collect the filter cake. After washing 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 example provides a preparation method of modified glass fiber for preparing cables of liquid-cooled high-power charging piles, including the following steps:

[0063] Step ①, prepare etched fiber

[0064] Weigh: 150.0 g of glass fiber and 1200.0 mL of 4 wt% sodium hydroxide aqueous solution are added to a reaction kettle and stirred. The stirring rate is 70 rpm, the temperature of the reaction kettle is raised to 70 °C, and the reaction is carried out for 2 h while maintaining the temperature. After the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature, filter the reaction solution by suction to collect the filter cake. After washing the filter cake with ethanol four times, transfer the filter cake to a vacuum drying oven and vacuum dry it to constant weight to obtain etched fiber.

[0065] Step ②, prepare modified glass fiber

[0066] Weigh: 150.0 g of 3-isocyanatopropyltrimethoxysilane and 500.0 mL of N,N-dimethylformamide are mixed to obtain a modification liquid;

[0067] Weigh: 450.0 g of etched fiber, 70.0 g of triethylamine and 1600.0 mL of N,N-dimethylformamide are added to a reaction kettle, nitrogen is introduced for protection, 900.0 mL of modification liquid is added to the reaction kettle, and the reaction is carried out for 50 min. After the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature, filter the reaction solution by suction to collect the filter cake. After washing the filter cake with ethanol four 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 example provides a preparation method of composite fiber cloth for preparing cables of liquid-cooled high-power charging piles, including the following steps:

[0070] Step Ⅰ, prepare glass fiber gel

[0071] Weigh: 200.0 g of aluminum isopropoxide, 1000.0 mL of ethanol and 100.0 g of sodium hydroxide powder are configured to obtain a hydrolysis aid;

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

[0073] Step II. Prepare a composite fiber cloth

[0074] Weigh: The glass fiber gel is transferred to a mold. Aluminum foil of the same shape and size as the mold is taken, and after coating one side of it with an 8 wt% aqueous sodium hydroxide solution, the coated side of the aluminum foil is attached to the surface of the glass fiber gel. After thermostatically treating the mold at 30 °C for 40 min, the mold is transferred to a vacuum drying oven at 80 °C and vacuum dried until no liquid is extracted, and then demolded to obtain a composite fiber cloth.

[0075] Example 5

[0076] This example provides a method for preparing a composite fiber cloth for use in the preparation of a cable for a liquid-cooled high-power charging pile, including the following steps:

[0077] Step I. Prepare a glass fiber gel

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

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

[0080] Step II. Prepare a composite fiber cloth

[0081] Weigh: The glass fiber gel is transferred to a mold. Aluminum foil of the same shape and size as the mold is taken, and after coating one side of it with a 10 wt% aqueous sodium hydroxide solution, the coated side of the aluminum foil is attached to the surface of the glass fiber gel. After thermostatically treating the mold at 50 °C for 60 min, the mold is transferred to a vacuum drying oven at 100 °C and vacuum dried until no liquid is extracted, and then demolded to obtain a composite fiber cloth.

[0082] Example 6

[0083] This example provides a method for preparing a composite fiber cloth for use in the preparation of a cable for a liquid-cooled high-power charging pile, including 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] Weigh: 450.0 g of aluminum chloride hexahydrate, 700.0 g of tetramethoxysilane and 4500.0 mL of deionized water and add them to the reaction kettle. The stirring rate of the reaction kettle is 70 rpm. After stirring at room temperature for 12 min, add 1500.0 mL of hydrolysis aid and 900.0 g of modified glass fiber prepared in Example 3 to the reaction kettle, and continue stirring for 35 min to obtain glass fiber gel.

[0087] Step Ⅱ: Preparation of composite fiber cloth

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

[0089] Example 7

[0090] This example provides a preparation method of a heat-conducting filler for a liquid-cooled high-power charging pile cable, including the following steps:

[0091] Step ⑴: Preparation of pyrolytic graphite

[0092] Transfer the graphite to a heating vacuum furnace at 2000 °C. After holding for 4 min, introduce toluene gas into the reaction kettle. After holding for 20 min, naturally cool to room temperature to obtain pyrolytic graphite.

[0093] Step ⑵: Preparation of annealed graphite

[0094] Transfer the pyrolytic graphite to a heating vacuum furnace at 2800 °C, and introduce nitrogen gas to maintain the internal pressure of the heating vacuum furnace at 6 MPa. After heat treatment for 40 min, cool to room temperature at a cooling rate of 3 °C / min to obtain annealed graphite.

[0095] Step ⑶: Preparation of activated annealed graphite

[0096] After uniformly coating the annealed graphite on the quartz wafer, transfer it to a plasma processing equipment. Turn on the vacuum pump to extract the chamber gas. After the vacuum degree is less than 10 mTorr, turn on the gas control system and introduce a mixed gas with an argon-to-oxygen volume ratio of 4:1. Set the instrument power to 50 W, the mixed gas flow rate to 100 sccm, and the pressure to 100 mTorr. Then turn on the RF power supply. After processing at room temperature for 3 min, turn off the RF power supply and introduce argon for purging for 1 min to obtain activated annealed graphite.

[0097] Step (4), preparing the thermal conductive filler

[0098] Weigh: 800.0 g of activated annealed graphite, 200.0 g of ethanol, 200.0 mL of saturated sodium hydroxide solution, and 4000.0 mL of deionized water, add them to a reaction kettle and introduce nitrogen for protection. After the temperature of the reaction kettle is reduced to 5 °C, add 300.0 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane to the reaction kettle, keep the temperature for reaction for 20 min. After the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature, filter the reaction solution by suction to collect the filter cake. After washing the filter cake with ethanol 3 times, transfer the filter cake to a vacuum drying oven and dry it to constant weight under vacuum to obtain the thermal conductive filler.

[0099] Example 8

[0100] This example provides a preparation method of a thermal conductive filler for a cable used in a liquid-cooled high-power charging pile, including the following steps:

[0101] Step (1), preparing pyrolytic graphite

[0102] Transfer the graphite to a heating vacuum furnace at a temperature of 2000 °C. After keeping the temperature for 5 min, introduce toluene gas into the reaction kettle. After keeping the temperature for 30 min, cool it naturally to room temperature to obtain pyrolytic graphite.

[0103] Step (2), preparing annealed graphite

[0104] Transfer the pyrolytic graphite to a heating vacuum furnace at 3100 °C, and introduce nitrogen to maintain the internal pressure of the heating vacuum furnace at 8 MPa. After heat preservation treatment for 60 min, cool it at a cooling rate of 4 °C / min to room temperature to obtain annealed graphite.

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

[0106] After uniformly coating the annealed graphite on a quartz wafer, transfer it to a plasma processing equipment. Turn on the vacuum pump to extract the chamber gas. After the vacuum degree is less than 10 mTorr, turn on the gas control system and introduce a mixed gas with a volume ratio of argon to oxygen of 4:1. Set the instrument power to 80 W, the flow rate of the mixed gas to 150 sccm, and the pressure to 150 mTorr. Then turn on the RF power supply and process at room temperature for 5 min. After that, turn off the RF power supply and introduce argon for purging for 2 min to obtain activated annealed graphite.

[0107] Step (4), preparing the thermal conductive filler

[0108] Weigh: 1000.0 g of activated annealed graphite, 300.0 g of ethanol, 300.0 mL of saturated sodium hydroxide solution, and 6000.0 mL of deionized water, add them to a reaction kettle and introduce nitrogen for protection. After the temperature of the reaction kettle is reduced to 10 °C, add 500.0 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane to the reaction kettle, keep the temperature for reaction for 30 min. After the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature, filter the reaction solution to collect the filter cake, wash the filter cake 5 times with ethanol, and then transfer the filter cake to a vacuum drying oven for vacuum drying to constant weight to obtain the thermal conductive filler.

[0109] Example 9

[0110] This example provides a preparation method of a thermal conductive filler for a liquid-cooled high-power charging pile cable, including the following steps:

[0111] Step (1), preparing pyrolytic graphite

[0112] Transfer the graphite to a heating vacuum furnace at a temperature of 2000 °C, keep the temperature for 5 min, then introduce toluene gas into the reaction kettle, keep the temperature for 30 min, and then naturally cool to room temperature to obtain pyrolytic graphite.

[0113] Step (2), preparing annealed graphite

[0114] Transfer the pyrolytic graphite to a heating vacuum furnace at 3000 °C and introduce nitrogen to maintain the internal pressure of the heating vacuum furnace at 7 MPa. After heat preservation treatment for 50 min, cool down to room temperature at a cooling rate of 4 °C / min to obtain annealed graphite.

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

[0116] After uniformly coating the annealed graphite on the quartz wafer, transfer it to a plasma processing equipment. Open the vacuum pump to extract the chamber gas. After the vacuum degree is less than 10 mTorr, open the gas control system and introduce a mixed gas with an argon-to-oxygen volume ratio of 4:1. Set the instrument power to 70 W, the flow rate of the mixed gas to 120 sccm, and the pressure to 120 mTorr. Then turn on the RF power supply and process at room temperature for 4 min. After that, turn off the RF power supply and introduce argon for purging for 2 min to obtain activated annealed graphite.

[0117] Step (4), preparing the thermal conductive filler

[0118] Weigh: 900.0 g of activated annealed graphite, 250.0 g of ethanol, 250.0 mL of saturated sodium hydroxide solution, and 5000.0 mL of deionized water, add them to a reaction kettle and introduce nitrogen for protection. After the temperature of the reaction kettle is reduced to 8 °C, add 400.0 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane to the reaction kettle, keep the temperature for reaction for 25 min. After the reaction is completed, wait for the temperature of the reaction kettle to drop to room temperature, filter the reaction solution by suction to collect the filter cake, wash the filter cake 4 times with ethanol, and then transfer the filter cake to a vacuum drying oven for vacuum drying to constant weight to obtain the thermal conductive filler.

[0119] Example 10

[0120] This example provides a preparation method for a cable used in a liquid-cooled high-power charging pile, including the following steps:

[0121] Step one, preparing the modified thermal conductive tube

[0122] Weigh: 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, 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 170 °C, 185 °C, 185 °C, 190 °C, 190 °C, 200 °C, 200 °C, and 210 °C in sequence. The main machine speed of the twin-screw extruder is 80 rpm, the pressure is 100 bar, melt and extrude to coat on the mold, and then cure and demold to obtain the modified thermal conductive tube.

[0123] Step two, preparing the core layer

[0124] Separate the positive and negative cores in the two-core power line into two respectively, and wind them in a two-positive and two-negative spiral around the surface of a single modified thermal conductive tube to obtain the core layer 1.

[0125] Step three, preparing the insulation layer

[0126] Use a polyvinyl chloride wrapping tape to wrap around the surface of the core layer to obtain the insulation layer 2.

[0127] Step 4: Prepare the heat exchange layer

[0128] Use several modified heat-conducting tubes and arrange them in a spiral shape on the surface of the insulating layer to obtain the heat exchange layer 3.

[0129] Step 5: Prepare the heat insulation layer

[0130] Use the composite fiber cloth prepared in Example 4 to wrap the surface of the heat exchange layer 3, and after fixing, obtain the heat insulation layer 4.

[0131] Step 6: Prepare the liquid-cooled cable

[0132] Weigh: 7000.0 g of polypropylene, 500.0 g of dioctyl phthalate, 20.0 g of tris(2,4-di-tert-butylphenyl) phosphate, 20.0 g of 2-hydroxy-4-octyloxybenzophenone, 500.0 g of epoxidized soybean oil, 500.0 g of calcium carbonate, and 50.0 g 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 in sequence. The main machine speed of the twin-screw extruder is 80 rpm, the pressure is 100 bar, and it is melt-extruded and coated on the surface of the heat insulation layer 4. After curing, obtain the sheath layer 5, thus obtaining the liquid-cooled cable.

[0133] Example 11

[0134] This example provides a preparation method for a cable used in a liquid-cooled high-power charging pile, including the following steps:

[0135] Step 1: Prepare the modified heat-conducting tube

[0136] Weigh: 5000.0 g of polyvinyl chloride, 5000.0 g of the heat-conducting 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 epoxidized soybean oil, and 200.0 g of polyvinyl alcohol, 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 170 °C, 185 °C, 185 °C, 190 °C, 190 °C, 200 °C, 200 °C, and 210 °C in sequence. The main machine speed of the twin-screw extruder is 120 rpm, the pressure is 150 bar, and it is melt-extruded and coated on the mold. After curing and demolding, obtain the modified heat-conducting tube.

[0137] Step 2: Prepare the core layer

[0138] Separate the positive and negative cores in the two-core power line into two respectively, and use two positives and two negatives to wind spirally on the surface of a single modified heat-conducting tube to obtain the core layer 1.

[0139] Step 3: Prepare the insulating layer

[0140] Wrap the surface of the core layer with polyvinyl chloride tape to obtain the insulating layer 2.

[0141] Step 4: Prepare the heat exchange layer

[0142] Arrange a number of modified heat-conducting tubes spirally on the surface of the insulating layer to obtain the heat exchange layer 3.

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

[0144] Wrap the surface of the heat exchange layer 3 with the composite fiber cloth prepared in Example 5, and obtain the heat-insulating layer 4 after fixing.

[0145] Step 6: Prepare the liquid-cooled cable

[0146] Weigh: 7500.0 g of polypropylene, 1000.0 g of dioctyl phthalate, 100.0 g of tris(2,4-di-tert-butylphenyl) phosphate, 200.0 g of 2-hydroxy-4-octyloxybenzophenone, 1000.0 g of epoxidized soybean oil, 1000.0 g of calcium carbonate, and 200.0 g 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 inlet to the discharge outlet are 200 °C, 215 °C, 215 °C, 220 °C, 220 °C, 230 °C, 230 °C, and 240 °C in sequence. The main machine speed of the twin-screw extruder is 120 rpm, the pressure is 150 bar, and it is melt-extruded and coated on the surface of the heat-insulating layer 4, and the sheath layer 5 is obtained after curing, thus obtaining the liquid-cooled cable.

[0147] Example 12

[0148] This example provides a preparation method for a cable used in a liquid-cooled high-power charging pile, including the following steps:

[0149] Step 1: Prepare the modified heat-conducting tube

[0150] Weigh: 4000.0 g of polyvinyl chloride, 4000.0 g of the heat-conducting 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 epoxidized soybean oil, and 100.0 g of polyvinyl alcohol and add them 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 are 170 °C, 185 °C, 185 °C, 190 °C, 190 °C, 200 °C, 200 °C, and 210 °C in sequence. The main machine speed of the twin-screw extruder is 100 rpm, the pressure is 120 bar, and it is melt-extruded and coated on the mold, and the mold is demolded after curing to obtain the modified heat-conducting tube.

[0151] Step 2: Prepare the core layer

[0152] Separate the positive and negative cores in the twin-core power line into two wires respectively, and wind two positives and two negatives spirally around the surface of a single modified heat-conducting tube to obtain the core layer 1.

[0153] Step Three: Prepare the insulating layer

[0154] Wrap the surface of the core layer with polyvinyl chloride wrapping tape to obtain the insulating layer 2.

[0155] Step Four: Prepare the heat exchange layer

[0156] Arrange several modified heat-conducting tubes spirally on the surface of the insulating layer to obtain the heat exchange layer 3.

[0157] Step Five: Prepare the heat insulation layer

[0158] Wrap the surface of the heat exchange layer 3 with the composite fiber cloth prepared in Example 6, and fix it to obtain the heat insulation layer 4.

[0159] Step Six: Prepare the liquid-cooled cable

[0160] Weigh: 7200.0 g of polypropylene, 800.0 g of dioctyl phthalate, 50.0 g of tris(2,4-di-tert-butylphenyl) phosphate, 100.0 g of 2-hydroxy-4-octyloxybenzophenone, 800.0 g of epoxidized soybean oil, 800.0 g of calcium carbonate and 100.0 g 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, 240 °C in sequence. The main machine speed of the twin-screw extruder is 100 rpm, the pressure is 120 bar, melt extrude and coat it on the surface of the heat insulation layer 4, and after curing, obtain the sheath layer 5, thus obtaining the liquid-cooled cable.

[0161] Comparative Example 1

[0162] The difference between this comparison and Comparative Example 12 is that in the preparation of the heat-conducting filler used in Step One, cancel Step ⑵, and in Step ⑶, use pyrolytic graphite to equally replace annealed graphite.

[0163] Comparative Example 2

[0164] The difference between this comparison and Comparative Example 12 is that in the preparation of the heat-conducting filler used in Step One, cancel Step ⑷, and use activated annealed graphite to equally replace the heat-conducting filler.

[0165] Comparative Example 2

[0166] The difference between this comparative example and Comparative Example 12 is that in the process of preparing the composite fiber cloth used in Step 5, Step I is cancelled, and a glass fiber gel is prepared by doping an equal amount of modified glass fiber in bisphenol A epoxy resin.

[0167] Performance test:

[0168] Refer to the standard GB / T 19666-2019 "General Rules for Flame Retardant and Fire Resistant Electric Wires, Cables or Optical Cables" to determine the flame retardant grade of the liquid-cooled cable;

[0169] Refer to the standard GB / T 10297-2015 "Determination of Thermal Conductivity of Non-Metallic Solid Materials - Hot Wire Method" to test the thermal conductivity of the modified heat conduction tubes prepared in Examples 10-12 and Comparative Examples 1-3;

[0170] Refer to the standard GB / T 10297-2015 "Determination of Thermal Conductivity of Non-Metallic Solid Materials - Hot Wire Method" to test the thermal conductivity of the composite fiber cloths prepared in Examples 4-6 and Comparative Examples 1-3;

[0171] Refer to the standard XF 306.2-2007 "Classification and Requirements for Flame Retardant and Fire Resistant Cables - Part 2: Fire Resistant Cables" to test the fire resistance of the liquid-cooled cables prepared in Examples 10-12 and Comparative Examples 1-3;

[0172] Refer to the standard GB / T 32511-2016 "General Technical Requirements for Electromagnetic Shielding Plastics" to test the liquid-cooled cables of the lightweight cables prepared in Examples 10-12 and Comparative Examples 1-3. The specific data are shown in Table 1.

[0173] Table 1 - Performance Test Data Sheet of Each Specimen

[0174] Project Group Example 10 Example 11 Example 12 Comparative Example 1 Comparative Example 2 Comparative Example 3 Flame Retardant Rating / 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 Rating / level ⅠA ⅠA ⅠA ⅠA ⅠA ⅠB Anti-Electromagnetic Interference Efficiency / level SE-1 SE-1 SE-1 SE-2 SE-1 SE-2

[0175] Data analysis:

[0176] Comparative analysis of the data in Table 1 reveals that the liquid-cooled cable prepared by the present invention has a flame retardant grade of IA, a fire resistance grade of IA, an anti-electromagnetic interference efficiency of SE-1, a thermal conductivity of the modified heat conduction tube of W·(m·K) -1 , and a thermal conductivity of the composite fiber cloth of W·(m·K) -1 , "-" indicates that this test is not performed on this sample, and all data are superior to those of the comparative examples;

[0177] It is noted that in the present invention, first, toluene gas is used for high-temperature pyrolysis on the surface of graphene to generate active carbon atoms. The active carbon atoms fill the defects of graphene, improving the crystallinity. Compared with direct annealing, toluene cracking provides a self-healing mechanism, making the hexagonal lattice of graphene more complete, reducing defects and vacancies. On this basis, annealing is carried out to rearrange the carbon atoms inside, and this rearrangement can significantly reduce the internal defects of the material, making its structure more tend to a highly ordered graphite sheet structure, thereby reducing phonon scattering and interfacial thermal resistance, and thus significantly improving the thermal conductivity of the thermal conductive filler. And the dispersion performance in the composite polyvinyl chloride is improved through the surface-modified siloxane structure. The epoxy groups distributed on the surface react with the free radicals generated during the melt extrusion process of polyvinyl chloride, so that the thermal conductive filler is stably dispersed inside the modified thermal conductive tube;

[0178] It is noted that in the present invention, the surface of glass fiber is etched, thus significantly improving the activity of the glass fiber. On this basis, the surface of the glass fiber is modified with a silane coupling agent, so that it participates in the hydrolysis process of aluminum chloride hexahydrate, methyl orthosilicate and aluminum isopropoxide, so that the glass fiber is evenly dispersed inside the hydrolysis gel. While using the glass fiber to improve the heat insulation performance of the composite fiber cloth, its surface is modified to reduce the damage of the fiber structure to the thermal conductive tube. Further, the surface of the aluminum foil is activated with an aqueous sodium hydroxide solution. Under the catalysis of alkalinity, the hydroxyl structure on the surface of the activated aluminum foil and the active structure on the surface of the glass fiber gel form a stable cross-linked structure through hydrolysis to obtain the composite fiber cloth. The composite fiber cloth locks the heat inside during the operation of the cable, making the heat generated by the core layer evenly distributed and slowly transferred to the outer sheath, thereby reducing the negative impact of the internal heat on the service life of the cable;

[0179] It is noted that the liquid-cooled cable prepared in the present invention, through the modified thermal conductive tube with high thermal conductivity inside and the heat-insulating composite fiber cloth, takes away the heat generated by the core layer through the internal coolant circulation, thereby reducing the impact of the internal heat on the cable life. During the combustion process, the protective layer structure generated by the decomposition of the glass fiber and the 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 thermal conductive tube, and thus taking away the flame heat through the coolant circulation, protecting the core layer and the insulating layer, and avoiding the occurrence of the secondary combustion phenomenon caused by the coolant leakage. Through the synergistic cooperation of the modified thermal conductive tube and the composite fiber cloth, the fire resistance and flame retardancy of the liquid-cooled cable are significantly improved. And through the multiple reflection effect brought by the multi-layer structure of the annealed graphene and the coordination of the aluminum foil attached to the surface of the composite fiber cloth, the shielding performance of the cable is significantly increased, enabling electromagnetic waves in a wider frequency range to be effectively shielded, thus significantly improving the thermal conductivity and electromagnetic interference resistance of the thermal conductive filler.

[0180] The above content is only an example and illustration of the structure of the present invention. Those skilled in the art of this technology can make various modifications, supplements, or use similar methods to replace the specific embodiments described, as long as they do not deviate from the structure of the invention or exceed the scope defined by this claim book, they should all fall within the protection scope of the present invention.

[0181] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a 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 explain the present invention. The preferred embodiments do not elaborate on all the details, nor do they limit the present invention to only the specific implementation manners. Obviously, according to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art of this technology can well understand and utilize the present invention. The present invention is only limited by the claim book and its 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, splitting the positive and negative cores of the dual-core power line into two respectively, and winding two positive and two negative spirals on the surface of a single modified heat conducting pipe to obtain a line core layer (1); S2, wrapping the surface of the wire core layer with a polyvinyl chloride wrapping tape to obtain an insulating layer (2); S3, using a plurality of modified heat-conducting pipes to be spirally arranged on the surface of the insulating layer to obtain a heat exchange layer (3); S4, wrapping the surface of the heat exchange layer (3) with a composite fiber cloth and fixing it to obtain a heat locking layer (4); S5. Use a composite polypropylene material to melt extrude and coat the surface of the heat-locking layer (4), and obtain a sheath layer (5) after solidification, thereby obtaining a liquid-cooled cable.

2. The method for preparing a cable for a liquid-cooled high-power charging pile according to claim 1, characterized in that: In step S1, the modified heat-conducting pipe is obtained by melt-extruding the composite polyvinyl chloride material, coating it on a mold, and curing and demoulding it; The composite polyvinyl chloride material comprises the following raw material components in parts by weight: 30-50 parts of polyvinyl chloride, 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 anti-impact agent and 0.5-2 parts of dispersant; in step S5, the composite polypropylene material comprises the following raw material components in parts by weight: 70-75 parts of polypropylene, 5-10 parts of plasticizer, 0.2-1 parts 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.

3. The method for preparing a cable for a liquid-cooled high-power charging pile according to claim 2, characterized in that: The preparation method of the thermal conductive filler comprises the following steps: A1. Transfer the graphite to a heating vacuum furnace at 2000°C, keep it warm for 4-5 minutes, introduce toluene gas into the reaction kettle, keep it warm for 20-30 minutes, and then cool it naturally to room temperature to obtain pyrolytic graphite; A2, transferring the pyrolytic graphite to a heating vacuum furnace at 2800-3100°C, introducing nitrogen, maintaining the internal pressure of the heating vacuum furnace at 6-8MPa, and heat-treating for 40-60min, then cooling to room temperature at a cooling rate of 3-4min°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 into a reactor. After nitrogen protection is introduced, the temperature of the reactor is lowered to 5-10°C, and 3-(2,3-epoxypropoxy)propyltrimethoxysilane is added to the reactor. The reaction is kept warm for 20-30 minutes, and a thermal conductive filler is obtained by post-treatment.

4. The method for preparing a cable for a liquid-cooled high-power charging pile according to claim 3, 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.

5. The method for preparing a cable for a liquid-cooled high-power charging pile according to claim 1, characterized in that: In step S4, the method for preparing 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 the mold, take an aluminum foil of the same shape and size as the mold, and coat one side of the aluminum foil with 8-10wt% 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 40-60min, and obtain a composite fiber cloth after post-treatment.

6. The method for preparing a cable for a liquid-cooled high-power charging pile according to claim 5, characterized in that: In step B1, the dosage 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 a dosage ratio of 2-3g:10-12mL:1-2g.

7. The method for preparing a cable for a liquid-cooled high-power charging pile according to claim 5, characterized in that: The preparation method of the modified glass fiber comprises the following steps: C1. Add glass fiber and 3-5wt% sodium hydroxide aqueous solution into a reactor and stir. Raise the temperature of the reactor to 60-80°C, keep the reaction temperature for 1-2h, and perform post-processing to obtain etched fiber. C2. Add the etched fiber, triethylamine and N,N-dimethylformamide into a reactor, introduce nitrogen protection, add the modified liquid into the reactor, react for 40-60 minutes, and post-treat to obtain the modified glass fiber.

8. The method for preparing a cable for a liquid-cooled high-power charging pile according to claim 7, characterized in that: In step C1, the amount ratio of glass fiber and 3-5wt% sodium hydroxide aqueous solution is 1-2g:10-15mL; in step C2, the amount 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 at a ratio of 1-2g:5mL.

9. 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 as described in any one of claims 1 to 8 is applied to charging electric vehicle fast charging piles and electric commercial vehicles.

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