High-thermal-conductivity flame-retardant nano-composite insulated cable for high-voltage direct-current energy storage system

Abstract

The invention discloses a high-thermal-conductivity flame-retardant nano-composite insulated cable for a high-voltage direct-current energy storage system, belongs to the technical field of insulating material and cable manufacturing, and aims to solve the technical problem that flame retardance, thermal conductivity, insulation and mechanical properties of the high-thermal-conductivity flame-retardant nano-composite insulated cable for the high-voltage direct-current energy storage system need to be further improved. The cable specifically comprises a conductor, a conductor shielding layer, an insulating layer, an insulation shielding layer, a metal shielding layer and a sheath layer, and the insulating layer comprises the following components in parts by weight: 96-100 parts of polysiloxane, 22-28 parts of composite aerogel, 18-22 parts of modified nano magnesium oxide, 0.8-1.4 parts of 2, 5-dimethyl-2, 5-bis (tert-butylperoxy) hexane and 2-3 parts of an auxiliary additive. The flame-retardant, heat-conducting, insulating and mechanical properties of the insulating layer are further improved through prepared polysiloxane, composite aerogel and modified nano magnesium oxide.

Description

Technical Field

[0001] This invention relates to the field of insulating materials and cable manufacturing technology, specifically to a high thermal conductivity and flame retardant nanocomposite insulated cable for use in high voltage DC energy storage systems. Background Technology

[0002] With the rapid development of renewable energy and the construction of smart grids, high-voltage direct current energy storage systems have been widely used in new energy power plants, supercharging piles and data centers due to their advantages of high efficiency, flexibility and large capacity. As the core component of energy transmission in the system, the technical performance of cables directly determines the safe and stable operation and service life of the system.

[0003] Currently, cables for high-voltage direct current (HVDC) energy storage systems face complex operating challenges, requiring long-term exposure to high voltage, high current, and frequent charging and discharging. Traditional cables are gradually revealing numerous technical defects. In terms of electrical insulation, conventional insulation materials are prone to accumulating space charge under high-voltage direct current electric fields, leading to local electric field distortion, electrical tree aging, and premature breakdown, becoming a core bottleneck restricting cable lifespan. Thermal management is also a prominent issue. Cables are densely laid within the energy storage battery compartment, carrying fluctuating high currents. Traditional insulation materials have poor thermal conductivity, making it difficult to dissipate the heat generated by the conductors. The accumulated heat accelerates the aging of the insulation materials and may even trigger a thermal runaway chain reaction. In terms of fire safety, energy storage compartments are mostly enclosed or semi-enclosed spaces. When cables burn, they easily release dense smoke and toxic gases. Once a fire occurs due to overload or fault, it will cause catastrophic consequences, placing extremely high demands on the flame-retardant performance of cables. In addition, the design life of energy storage power stations typically exceeds 15 years, requiring cable insulation to maintain stable performance over a long period under the combined effects of electro-thermal-mechanical stresses.

[0004] Therefore, developing a nanocomposite insulated cable that combines high thermal conductivity, high flame retardancy, excellent electrical insulation properties, and mechanical stability to solve the safety and reliability problems of traditional cables under complex working conditions has become an urgent need for the development of high voltage DC energy storage systems. Summary of the Invention

[0005] The purpose of this invention is to provide a high thermal conductivity and flame retardant nanocomposite insulated cable for high voltage direct current energy storage systems, in order to solve the technical problem that the flame retardant performance, thermal conductivity, insulation performance and mechanical properties of high thermal conductivity and flame retardant nanocomposite insulated cables for high voltage direct current energy storage systems in the prior art need to be further improved.

[0006] The objective of this invention can be achieved through the following technical solution: a high thermal conductivity and flame retardant nanocomposite insulated cable for high voltage DC energy storage systems, comprising a conductor, a conductor shielding layer, an insulation layer, an insulation shielding layer, a metal shielding layer, and a sheath layer; The high thermal conductivity and flame retardant nanocomposite insulation layer comprises the following components by weight: 96-100 parts polysiloxane, 22-28 parts composite aerogel, 18-22 parts modified nano magnesium oxide, 0.8-1.4 parts bis(2,5-dimethyl)sulfide and 2-3 parts auxiliary additives. The auxiliary additives comprise the following components by weight: 0.5-0.8 parts zinc stearate and 0.3-0.5 parts 1010.

[0007] Furthermore, the preparation method of the polysiloxane is as follows: octaphenylcyclotetrasiloxane, heptamethylphenylcyclotetrasiloxane, and tetraethylammonium hydroxide hydrate are added to a reaction vessel containing N-methylpyrrolidone. The mixture is first stirred at 90-100℃ for 1-2 hours, then heated to 120-130℃ and stirred for 40-60 minutes. After cooling to room temperature, anhydrous ethanol is added, and the mixture is stirred for 20-30 minutes. The mixture is then filtered, and the filter cake is washed 2-3 times with anhydrous ethanol. It is then transferred to a vacuum drying oven and dried at 80℃ for 4-6 hours to obtain the polysiloxane.

[0008]

[0009] In the formula:

[0010] Furthermore, the ratio of the amount of octaphenylcyclotetrasiloxane, heptamethylphenylcyclotetrasiloxane, tetraethylammonium hydroxide hydrate and N-methylpyrrolidone is 1g:9g:0.2g:10-12mL.

[0011] Furthermore, the preparation method of the composite aerogel is as follows: sodium alginate is added to deionized water, stirred at 50-60℃ for 20-30 min, titanium dioxide whiskers are added, and stirring is continued for 20-30 min. Then, boric acid solution is added dropwise. After the addition is complete, the reaction is carried out for 2-3 h, and then frozen at -20℃ for 12 h. The crystals are then taken out and placed in a freeze vacuum dryer and dried at -50℃ for 48 h. Finally, the crystals are transferred to a ball mill and ground at a speed of 200-300 r / min for 1-2 h. The mixture is then passed through a 200-mesh sieve to obtain the composite aerogel.

[0012] Furthermore, the ratio of sodium alginate, deionized water, titanium dioxide whiskers, and boric acid solution is 1g:48-56mL:2-2.2g:2mL, and the mass fraction of the boric acid solution is 0.3%.

[0013] Furthermore, the preparation method of the modified nano magnesium oxide is as follows: nano magnesium oxide is added to a reaction vessel containing anhydrous ethanol, stirred at 40-50℃ for 10-20 min, KH560 aqueous solution is added, and stirring is continued for 20-30 min. After the reaction is completed, the mixture is filtered, and the product is transferred to a vacuum drying oven and dried at 80℃ to constant weight to obtain modified nano magnesium oxide.

[0014] Furthermore, the ratio of the amount of nano-magnesium oxide, anhydrous ethanol and KH560 aqueous solution is 1g:26-30mL:3-4mL, and the mass fraction of the KH560 aqueous solution is 8%.

[0015] Furthermore, the preparation method of the high thermal conductivity and flame retardant nanocomposite insulated cable is as follows: several conductors are arranged in parallel, a shielding layer is wrapped around the outside of the conductors to form a shielding layer, an insulating layer is wrapped around the outside of the shielding layer to form an insulating layer outside the shielding layer, an insulating shielding layer is wrapped around the outside of the insulating layer to form an insulating shielding layer outside the insulating layer, a metal shielding layer is wrapped around the outside of the insulating shielding layer to form a metal shielding layer, thereby obtaining a high thermal conductivity and flame retardant nanocomposite insulated cable.

[0016] Furthermore, the coating process of the insulating layer is as follows: polysiloxane, composite aerogel, modified nano magnesium oxide and auxiliary additives are added to a mixer and mixed at 80-90°C for 10-15 minutes. Then, a bis(2,5) vulcanizing agent is added and the mixture is continued to be mixed for about 8-10 minutes. The mixture is then extruded and coated on the outside of the shielding layer. The mixture is then placed in a flat vulcanizing machine and vulcanized at 160°C for 1-2 hours. After cooling to room temperature, the mixture is removed to form the insulating coating layer.

[0017] Furthermore, the high thermal conductivity and flame retardant nanocomposite insulated cable comprises, from the inside out, a conductor, a conductor shielding layer, an insulation layer, an insulation shielding layer, a metal shielding layer, and a sheath layer; the conductor is copper wire, the conductor shielding layer is obtained by covering the copper wire with aluminum foil, the insulation layer is prepared by the above steps and covered on the outside of the conductor shielding layer, the insulation shielding layer is obtained by covering the outside of the insulation layer with insulating tape, the metal shielding layer is obtained by covering the outside of the insulation shielding layer with braided copper wire, and the sheath layer is obtained by covering the outside of the metal shielding layer with cross-linked polyethylene.

[0018] The present invention has the following beneficial effects: 1. This invention relates to a self-made polysiloxane containing phenyl groups. The aromatic ring structure of phenyl groups has high thermal stability, which can delay thermal decomposition during combustion and provide a basic guarantee for flame retardancy. The composite aerogel is composed of sodium alginate and titanium dioxide whiskers. The carbon, hydrogen, and oxygen elements of sodium alginate construct a three-dimensional network porous structure, which can physically block the contact between flame and oxygen, and block heat transfer. The titanium and oxygen elements of titanium dioxide whiskers further inhibit combustion by reflecting heat. After modification with KH560, the surface of modified nano-magnesium oxide retains the inorganic flame retardant properties of magnesium and oxygen elements. Its decomposition process can absorb a large amount of heat and inhibit the combustion chain reaction. At the same time, the organic functional groups grafted on the surface improve its compatibility with polysiloxane and form a continuous flame retardant barrier uniformly dispersed in the system. Under the synergistic effect of the three, the thermal stability of polysiloxane, the physical barrier function of composite aerogel, and the chemical flame retardant mechanism of modified nano-magnesium oxide complement each other to construct a comprehensive flame retardant system and effectively improve the oxygen index of the material.

[0019] 2. The polysiloxane of this invention is formed by ring-opening polymerization of cyclic siloxane monomers. The large number of silicon-oxygen bonds in the molecular chain have excellent insulation properties. The regular molecular structure enables the matrix to form a dense insulating network, reducing charge migration channels. The porous structure of the composite aerogel can uniformly disperse the electric field, avoiding the problem of weak insulation caused by electric field concentration. The hydroxyl groups of its sodium alginate coating layer form a weak interaction with the polysiloxane molecular chain, further optimizing the interfacial insulation performance. The Si-O-Mg covalent bonds on the surface of modified nano-magnesium oxide enable silicon, oxygen, and magnesium elements to form a stable interfacial structure, eliminating the insulation defects caused by the easy agglomeration of unmodified fillers. At the same time, both nano-magnesium oxide and titanium dioxide whiskers in the composite aerogel are high thermal conductivity fillers. The magnesium and oxygen elements of the former and the titanium and oxygen elements of the latter construct a continuous thermally conductive network, while the polysiloxane molecular chain provides a bridge for heat transfer. The three work together to enable rapid heat conduction without affecting the insulation integrity, ultimately achieving a simultaneous improvement in breakdown voltage and thermal conductivity.

[0020] 3. The polysiloxane molecular chains of this invention have good flexibility. The flexible structure of its silicon-oxygen bonds provides the basic toughness of the material, and the three-dimensional network structure formed after the cross-linking reaction enhances the integrity of the matrix. The porous structure of the composite aerogel combines flexibility and rigidity. The flexible coating layer constructed by the carbon, hydrogen, and oxygen elements of sodium alginate can absorb stress, while the rigid structure of titanium dioxide whiskers plays a reinforcing role. The combination of the two not only alleviates the damage to the matrix toughness caused by rigid fillers, but also improves the impact resistance of the material by dispersing stress. The organic functional groups grafted on the surface of modified nano-magnesium oxide form physical entanglement with the polysiloxane molecular chains. The inorganic particles composed of magnesium and oxygen elements are tightly bonded to the interface of the organic matrix, avoiding stress concentration caused by filler agglomeration. During tensile and impact processes, the porous structure of the composite aerogel disperses stress, the modified nano-magnesium oxide anchors the matrix molecular chains, and the polysiloxane matrix provides flexible support. Under the synergistic effect of the three, the elongation at break and the unnotched impact strength of the cantilever beam are significantly improved. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In this application, the titanium dioxide whiskers are selected from Wuhan Yuancheng Chemical Co., Ltd., CAS No. 13463-67-7, with a particle size of 200nm; In this application, the nano-magnesium oxide is selected from Shenzhen Jingcai Chemical Co., Ltd., CAS No. 1309-48-4, model JC-MG05. Example 1

[0023] This embodiment provides a high thermal conductivity and flame retardant nanocomposite insulated cable for high voltage DC energy storage systems, comprising the following steps: S1, Preparation of polysiloxane Weigh out 10g of octaphenylcyclotetrasiloxane, 90g of heptamethylphenylcyclotetrasiloxane, and 2g of tetraethylammonium hydroxide hydrate and add them to a reaction vessel containing 100mL of N-methylpyrrolidone. First, stir at 90℃ for 1h, then raise the temperature to 120℃ and stir for 40min. After cooling to room temperature, add 100mL of anhydrous ethanol and stir for 20min. Filter the mixture, wash the filter cake twice with anhydrous ethanol, transfer it to a vacuum drying oven, and dry it at 80℃ for 4h to obtain polysiloxane.

[0024] During the reaction, tetraethylammonium hydroxide hydrate dissociates into OH⁻ in the reaction system. OH⁻ acts as a nucleophile, attacking the silicon atoms on the silicon-oxygen bonds in the cyclic siloxane molecule, causing heterolytic cleavage of the silicon-oxygen bonds. The cyclic monomers open to form linear oligomers with active end groups. During the heating process, the ring-opening of the cyclic monomers is initiated at low temperature, while the molecular chain growth is promoted at high temperature to form polysiloxane copolymers. The target polysiloxane product is finally obtained by precipitation, washing and purification with anhydrous ethanol and vacuum drying.

[0025] S2, Preparation of composite aerogel Weigh 10g of sodium alginate and add it to 480mL of deionized water. Stir at 50℃ for 20min, then add 20g of titanium dioxide whiskers and continue stirring for 20min. Next, add 20mL of 0.3% d boric acid solution dropwise. After the addition is complete, react for 2h and freeze at -20℃ for 12h. Take out the crystals and place them in a freeze dryer and dry at -50℃ for 48h. Then transfer them to a ball mill and grind them at 200r / min for 1h. Pass them through a 200-mesh sieve to obtain composite aerogel.

[0026] During the reaction, sodium alginate swells and dissolves in deionized water to form a dispersed molecular chain. Titanium dioxide whiskers are uniformly dispersed in the dispersion through interfacial hydrogen bonding. The added boric acid undergoes a diol-type coordination crosslinking reaction with the hydroxyl groups on the sodium alginate molecular chain, constructing a three-dimensional network gel precursor that encapsulates the titanium dioxide whiskers. After low-temperature freeze-setting, vacuum freeze-drying to preserve pores, and ball milling and sieving, a sodium alginate-coated titanium dioxide whisker composite aerogel with a uniform porous structure is obtained.

[0027] S3, Preparation of modified nano-magnesium oxide Weigh 10g of nano-magnesium oxide and add it to a reaction vessel containing 260mL of anhydrous ethanol. Stir at 40℃ for 10min, then add 30mL of 8% KH560 aqueous solution and continue stirring for 20min. After the reaction is complete, filter the product and transfer it to a vacuum drying oven. Dry the product at 80℃ to constant weight to obtain modified nano-magnesium oxide.

[0028] During the reaction, in an anhydrous ethanol dispersion system, the hydroxyl groups on the surface of nano-magnesium oxide first come into full contact with the dispersion medium and remain active. Subsequently, an aqueous solution of silane coupling agent KH560 is added. KH560 generates silanol groups through hydrolysis. These silanol groups undergo a dehydration condensation reaction with the hydroxyl groups on the surface of nano-magnesium oxide to form stable Si-O-Mg covalent bonds. At the same time, the epoxy groups at the other end of the KH560 molecule are exposed on the surface of the modified nano-magnesium oxide. Finally, the solvent and unreacted small molecules in the system are removed by filtration and vacuum drying to obtain modified nano-magnesium oxide with surface grafted organic functional groups.

[0029] S4. Preparation of high thermal conductivity and flame retardant nanocomposite insulated cables Weigh out 0.5 parts of zinc stearate and 0.3 parts of 1010, mix them evenly, and obtain the auxiliary additive; Several copper wires are arranged in parallel, and aluminum foil is wrapped around the outside of the copper wires to obtain a conductor shielding layer. Then, 96 parts by weight of polysiloxane, 22 parts of composite aerogel, 18 parts of modified nano magnesium oxide, and 2 parts of auxiliary additives are added to a mixer and mixed at 80°C for 10 minutes. Then, a bis(2,5)-sulfurizing agent is added, and mixing is continued for about 8 minutes. The mixture is then extruded and wrapped around the outside of the shielding layer. The mixture is then placed in a flat vulcanizing machine and vulcanized at 160°C for 1 hour. After cooling to room temperature, the mixture is removed and an insulation layer is formed on the outside of the conductor shielding layer. Insulating tape is then wrapped around the outside of the insulation layer to form an insulating shielding layer. Braided copper wire is then wrapped around the outside of the insulating shielding layer to form a metal shielding layer. Finally, melt-crosslinked polyethylene is extruded and wrapped around the outside of the metal shielding layer to form a sheath layer, resulting in a high thermal conductivity and flame retardant nanocomposite insulated cable.

[0030] In the internal mixer, the polysiloxane alkyl body is first thoroughly mixed and dispersed with the composite aerogel, modified nano-magnesium oxide, and auxiliary additives. The organic functional groups grafted on the surface of the modified nano-magnesium oxide generate physical entanglement or weak interaction with the polysiloxane molecular chains. The composite aerogel fills the gaps between the polysiloxane molecular chains in the form of nanofillers. Then, after the addition of the bis(2,5) sulfiding agent, the sulfiding agent decomposes to generate free radicals, which trigger free radical cross-linking reactions between the polysiloxane molecular chains to form a three-dimensional network cross-linked structure. At the same time, the filler particles are firmly anchored in the cross-linked network. Subsequently, the cross-linking reaction is further promoted to complete in the flat vulcanizing machine. Finally, through cooling and shaping, a polysiloxane composite insulating layer with excellent insulation and mechanical properties is formed on the outside of the conductor shielding layer. Example 2

[0031] This embodiment provides a high thermal conductivity and flame retardant nanocomposite insulated cable for high voltage DC energy storage systems, comprising the following steps: S1, Preparation of polysiloxane Weigh out 10g of octaphenylcyclotetrasiloxane, 90g of heptamethylphenylcyclotetrasiloxane, and 2g of tetraethylammonium hydroxide hydrate and add them to a reaction vessel containing 110mL of N-methylpyrrolidone. First, stir at 95℃ for 1.5h, then raise the temperature to 125℃ and stir for 50min. After cooling to room temperature, add 110mL of anhydrous ethanol and stir for 25min. Filter the mixture, wash the filter cake twice with anhydrous ethanol, transfer it to a vacuum drying oven, and dry it at 80℃ for 5h to obtain polysiloxane.

[0032] S2, Preparation of composite aerogel Weigh 10g of sodium alginate and add it to 520mL of deionized water. Stir at 55℃ for 25min, then add 21g of titanium dioxide whiskers and continue stirring for 25min. Next, add 20mL of 0.3% d boric acid solution dropwise. After the addition is complete, react for 2.5h and freeze at -20℃ for 12h. Take out the crystals and place them in a freeze dryer. Dry them at -50℃ for 48h, then transfer them to a ball mill and grind them at 250r / min for 1.5h. Pass them through a 200-mesh sieve to obtain composite aerogel.

[0033] S3, Preparation of modified nano-magnesium oxide Weigh 10g of nano-magnesium oxide and add it to a reaction vessel containing 280mL of anhydrous ethanol. Stir at 45℃ for 15min, then add 35mL of 8% KH560 aqueous solution and continue stirring for 25min. After the reaction is complete, filter the product and transfer it to a vacuum drying oven. Dry the product at 80℃ to constant weight to obtain modified nano-magnesium oxide.

[0034] S4. Preparation of high thermal conductivity and flame retardant nanocomposite insulated cables Weigh out 0.6 parts of zinc stearate and 0.4 parts of 1010, mix them evenly, and obtain the auxiliary additive; Several copper wires are arranged in parallel, and aluminum foil is wrapped around the outside of the copper wires to obtain a conductor shielding layer. Then, 98 parts by weight of polysiloxane, 25 parts of composite aerogel, 20 parts of modified nano magnesium oxide, and 2 parts of auxiliary additives are added to a mixer and mixed at 85°C for 12 minutes. Then, a bis(2,5)-sulfurizing agent is added, and mixing is continued for about 9 minutes. The mixture is then extruded and wrapped around the outside of the shielding layer. The mixture is then placed in a flat vulcanizing machine and vulcanized at 160°C for 1.5 hours. After cooling to room temperature, the mixture is removed and an insulation layer is formed on the outside of the conductor shielding layer. Insulating tape is then wrapped around the outside of the insulation layer to form an insulating shielding layer. Braided copper wire is then wrapped around the outside of the insulating shielding layer to form a metal shielding layer. Finally, melt-crosslinked polyethylene is extruded and wrapped around the outside of the metal shielding layer to form a sheath layer, resulting in a high thermal conductivity and flame retardant nanocomposite insulated cable. Example 3

[0035] This embodiment provides a high thermal conductivity and flame retardant nanocomposite insulated cable for high voltage DC energy storage systems, comprising the following steps: S1, Preparation of polysiloxane Weigh out 10g of octaphenylcyclotetrasiloxane, 90g of heptamethylphenylcyclotetrasiloxane, and 2g of tetraethylammonium hydroxide hydrate and add them to a reactor containing 120mL of N-methylpyrrolidone. First, stir at 100℃ for 2h, then raise the temperature to 130℃ and stir for 60min. After cooling to room temperature, add 120mL of anhydrous ethanol and stir for 30min. Filter the mixture, wash the filter cake three times with anhydrous ethanol, transfer it to a vacuum drying oven, and dry it at 80℃ for 6h to obtain polysiloxane.

[0036] S2, Preparation of composite aerogel Weigh 10g of sodium alginate and add it to 560mL of deionized water. Stir at 60℃ for 30min, then add 22g of titanium dioxide whiskers and continue stirring for 30min. Next, add 20mL of 0.3% d boric acid solution dropwise. After the addition is complete, react for 3h and freeze at -20℃ for 12h. Take out the crystals and place them in a freeze dryer and dry at -50℃ for 48h. Then transfer them to a ball mill and grind at 300r / min for 2h. Pass through a 200-mesh sieve to obtain composite aerogel.

[0037] S3, Preparation of modified nano-magnesium oxide Weigh 10g of nano-magnesium oxide and add it to a reaction vessel containing 300mL of anhydrous ethanol. Stir at 50℃ for 20min, then add 40mL of 8% KH560 aqueous solution and continue stirring for 30min. After the reaction is complete, filter the product and transfer it to a vacuum drying oven. Dry the product at 80℃ to constant weight to obtain modified nano-magnesium oxide.

[0038] S4. Preparation of high thermal conductivity and flame retardant nanocomposite insulated cables Weigh out 0.8 parts of zinc stearate and 0.5 parts of 1010, mix them evenly, and obtain the auxiliary additive; Several copper wires are arranged in parallel, and aluminum foil is wrapped around the outside of the copper wires to obtain a conductor shielding layer. Then, 100 parts by weight of polysiloxane, 28 parts of composite aerogel, 22 parts of modified nano magnesium oxide, and 3 parts of auxiliary additives are added to a mixer and mixed at 90°C for 15 minutes. Then, a bis(2,5)-sulfurizing agent is added, and mixing is continued for about 10 minutes. The mixture is then extruded and wrapped around the outside of the shielding layer. The mixture is then placed in a flat vulcanizing machine and vulcanized at 160°C for 2 hours. After cooling to room temperature, the mixture is removed and an insulation layer is formed on the outside of the conductor shielding layer. Insulating tape is then wrapped around the outside of the insulation layer to form an insulating shielding layer. Braided copper wire is then wrapped around the outside of the insulating shielding layer to form a metal shielding layer. Finally, melt-crosslinked polyethylene is extruded and wrapped around the outside of the metal shielding layer to form a sheath layer, resulting in a high thermal conductivity and flame retardant nanocomposite insulated cable.

[0039] Comparative Example 1 The difference between this comparative example and Example 3 is that step S1 is omitted, and commercially available end-hydroxyl polydimethylsiloxane is used instead of polysiloxane in step S4.

[0040] Comparative Example 2 The difference between this comparative example and Example 3 is that step S2 is omitted, and the composite aerogel in step S4 is replaced with titanium dioxide whiskers from step S2.

[0041] Comparative Example 3 The difference between this comparative example and Example 3 is that step S1 is omitted, and the modified nano-magnesium oxide in step S4 is replaced by nano-magnesium oxide in step S3.

[0042] Performance testing: The oxygen index of the high thermal conductivity and flame retardant nanocomposite insulated cables prepared in Examples 1-3 and Comparative Examples 1-3 was determined in accordance with the standard GB / T 10707-2008 "Determination of the flammability of rubber". The breakdown voltage of the high thermal conductivity and flame retardant nanocomposite insulated cables prepared in Examples 1-3 and Comparative Examples 1-3 was determined according to the standard GB / T 1695-2005 "Determination of power frequency breakdown voltage strength and withstand voltage of vulcanized rubber". The elongation at break of the high thermal conductivity and flame retardant nanocomposite insulated cables prepared in Examples 1-3 and Comparative Examples 1-3 was determined in accordance with the standard JB / T 13107-2017 "Silicone rubber insulated and sheathed flat cables with rated voltage of 0.6 / 1kV and below". The thermal conductivity of the high thermal conductivity and flame retardant nanocomposite insulated cables prepared in Examples 1-3 and Comparative Examples 1-3 was determined according to the standard GB / T 29313-2012 "Test Method for Thermal Conductivity of Electrical Insulation Materials". The unnotched cantilever beam impact strength of the high thermal conductivity and flame retardant nanocomposite insulated cables prepared in Examples 1-3 and Comparative Examples 1-3 was determined according to standard GB / T 1843-2008 "Determination of Impact Strength of Plastic Cantilever Beams". The specific test results are shown in Table 1 below: Table 1 - Performance Test Data of Samples

[0043] Data Analysis: Comparative analysis of the data in Table 1 above shows that the high thermal conductivity and flame retardant nanocomposite insulated cable prepared by this invention has an oxygen index of 33.0%, a breakdown voltage of 31.5 kV, an elongation at break of 247%, and a thermal conductivity of 2.57 W / (m²). 2 The unnotched impact strength of the cantilever beam is 98.3 kJ / m². 2 ; In Comparative Example 1, the self-made polysiloxane contains phenyl groups, resulting in superior thermal stability, while commercially available polysiloxanes lack this structure. This weakens the fundamental protection of the flame-retardant system, reducing the oxygen index to 29.3%. Furthermore, the commercially available polysiloxanes have insufficient molecular chain regularity, leading to reduced density of the insulating network formed after cross-linking, and a lower breakdown voltage of 27.2 kV. Their compatibility with fillers is slightly inferior to that of the self-made polysiloxane, affecting the continuity of the thermally conductive network and reducing thermal conductivity to 2.36 W / (m²). 2 (K), the matrix toughness support is slightly weaker, the elongation at break decreases to 226%, and the unnotched impact strength of the cantilever beam decreases to 91.5 kJ / m. 2 ; In Comparative Example 2, the three-dimensional network porous structure of the composite aerogel achieves physical barrier flame retardancy, while pure titanium dioxide whiskers lack this structure and can only slightly reflect heat, resulting in the loss of the flame retardant synergistic effect and a decrease in the oxygen index to 27.0%. The porous structure of the composite aerogel can disperse the electric field and optimize interfacial insulation, while the poor dispersion of pure titanium dioxide whiskers leads to a decrease in breakdown voltage to 28.7kV. The composite aerogel can synergistically construct a thermally conductive network with modified nano-magnesium oxide, while pure titanium dioxide whiskers are prone to agglomeration, destroying the thermal conductivity pathway and reducing the thermal conductivity to 2.22W / (m²). 2 (·K), while the flexible coating layer of the composite aerogel can absorb stress, the pure rigid titanium dioxide whiskers exacerbate stress concentration, reducing the elongation at break to 199%, and the unnotched impact strength of the cantilever beam to 78.8 kJ / m. 2 ; In Comparative Example 3, the unmodified nano-magnesium oxide surface lacks organic functional groups, exhibiting poor compatibility with polysiloxane matrices and easily agglomerating to form defects. This leads to the breakage of the flame-retardant barrier, a decrease in the oxygen index to 25.7%, and the agglomerates becoming electric field concentration points, severely compromising insulation integrity. The breakdown voltage decreases to 25.4 kV. Agglomeration also disrupts the thermal conductivity pathway, hindering heat transfer and reducing thermal conductivity to 2.08 W / (m²). 2 Large, aggregated particles (·K) act as stress concentration sources, leading to a significant decrease in the material's toughness and impact resistance. The elongation at break drops to 214%, and the unnotched impact strength of the cantilever beam decreases to 85.6 kJ / m². 2 .

[0044] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments 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 invention is limited only by the claims and their full scope and equivalents.

Claims

1. A high thermal conductivity, flame-retardant nanocomposite insulated cable for high-voltage direct current energy storage systems, characterized in that, It includes the conductor, conductor shielding layer, insulation layer, insulation shielding layer, metallic shielding layer, and sheath layer; The insulating layer comprises the following components by weight: 96-100 parts polysiloxane, 22-28 parts composite aerogel, 18-22 parts modified nano magnesium oxide, 0.8-1.4 parts bis(2,5) sulfide and 2-3 parts auxiliary additives.

2. The high thermal conductivity and flame retardant nanocomposite insulated cable for high voltage DC energy storage systems according to claim 1, characterized in that, The preparation method of the polysiloxane is as follows: octaphenylcyclotetrasiloxane, heptamethylphenylcyclotetrasiloxane and tetraethylammonium hydroxide hydrate are added to a reaction vessel containing N-methylpyrrolidone, stirred at 90-100℃ for 1-2 hours, then heated to 120-130℃ and stirred for 40-60 minutes, followed by post-treatment to obtain the polysiloxane.

3. The high thermal conductivity and flame-retardant nanocomposite insulated cable for high-voltage direct current energy storage systems according to claim 2, characterized in that, The ratio of the amounts of octaphenylcyclotetrasiloxane, heptamethylphenylcyclotetrasiloxane, tetraethylammonium hydroxide hydrate, and N-methylpyrrolidone is 1g:9g:0.2g:10-12mL.

4. The high thermal conductivity and flame retardant nanocomposite insulated cable for high voltage DC energy storage systems according to claim 1, characterized in that, The preparation method of the composite aerogel is as follows: sodium alginate is added to deionized water and stirred at 50-60℃ for 20-30 min. Then, titanium dioxide whiskers are added and stirred for another 20-30 min. Next, boric acid solution is added dropwise. After the addition is complete, the reaction is carried out for 2-3 h. The mixture is then frozen at -20℃ for 12 h. The crystals are then removed and placed in a freeze dryer and dried at -50℃ for 48 h. Finally, the mixture is transferred to a ball mill and ground at 200-300 r / min for 1-2 h. The mixture is then passed through a 200-mesh sieve to obtain the composite aerogel.

5. The high thermal conductivity and flame-retardant nanocomposite insulated cable for high-voltage direct current energy storage systems according to claim 4, characterized in that, The ratio of sodium alginate, deionized water, titanium dioxide whiskers and boric acid solution is 1g:48-56mL:2-2.2g:2mL, and the mass fraction of boric acid solution is 0.3%.

6. The high thermal conductivity and flame retardant nanocomposite insulated cable for high voltage DC energy storage systems according to claim 1, characterized in that, The modified nano-magnesium oxide is prepared by adding nano-magnesium oxide into a reaction vessel containing anhydrous ethanol, stirring at 40-50℃ for 10-20 min, adding KH560 aqueous solution, stirring for another 20-30 min, and then performing post-treatment to obtain modified nano-magnesium oxide.

7. The high thermal conductivity and flame retardant nanocomposite insulated cable for high voltage DC energy storage systems according to claim 6, characterized in that, The ratio of the amount of nano-magnesium oxide, anhydrous ethanol and KH560 aqueous solution is 1g:26-30mL:3-4mL, and the mass fraction of the KH560 aqueous solution is 8%.

8. The high thermal conductivity and flame-retardant nanocomposite insulated cable for high-voltage direct current energy storage systems according to any one of claims 1-7, characterized in that, The preparation method of the high thermal conductivity and flame retardant nanocomposite insulated cable is as follows: several conductors are arranged in parallel, a shielding layer is wrapped around the outside of the conductors to form a shielding layer, an insulating layer is wrapped around the outside of the shielding layer to form an insulating layer outside the shielding layer, an insulating shielding layer is wrapped around the outside of the insulating layer to form an insulating shielding layer outside the insulating layer, a metal shielding layer is wrapped around the outside of the insulating shielding layer to form a metal shielding layer, thus obtaining a high thermal conductivity and flame retardant nanocomposite insulated cable.

9. The high thermal conductivity and flame-retardant nanocomposite insulated cable for high-voltage direct current energy storage systems according to claim 8, characterized in that, The coating process of the insulating layer is as follows: Polysiloxane, composite aerogel, modified nano magnesium oxide and auxiliary additives are added to a mixer and mixed at 80-90℃ for 10-15 minutes. Then, a bis(2,5) vulcanizing agent is added and the mixture is continued to be mixed for about 8-10 minutes. The mixture is then extruded and coated on the outside of the shielding layer. The mixture is then placed in a flat vulcanizing machine and vulcanized at 160℃ for 1-2 hours. After cooling to room temperature, the mixture is removed to form the insulating coating layer.

10. The high thermal conductivity and flame-retardant nanocomposite insulated cable for high-voltage direct current energy storage systems according to claim 8, characterized in that, The high thermal conductivity and flame retardant nanocomposite insulated cable comprises, from the inside out, a conductor, a conductor shielding layer, an insulation layer, an insulation shielding layer, a metal shielding layer, and a sheath layer; the conductor is copper wire, the conductor shielding layer is obtained by covering the copper wire with aluminum foil, the insulation layer is prepared by the above steps and covered on the outside of the conductor shielding layer, the insulation shielding layer is obtained by covering the outside of the insulation layer with insulating tape, the metal shielding layer is obtained by covering the outside of the insulation shielding layer with braided copper wire, and the sheath layer is obtained by covering the outside of the metal shielding layer with cross-linked polyethylene.

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