Absorption and separation integrated nanofiber-based hydrated salt gel thermal protection material for lithium ion battery as well as preparation method and application of adsorption and separation integrated nanofiber-based hydrated salt gel thermal protection material

Abstract

The invention discloses a lithium ion battery oriented adsorption and separation integrated nanofiber-based hydrated salt gel thermal protection material as well as a preparation method and application thereof, relates to the technical field of lithium battery protection materials, and aims to solve the problem that an existing hydrated salt phase change material only absorbs heat or insulates heat and cannot realize multi-dimensional battery thermal protection. The gel is composed of a phase-change substrate material, a gel packaging material and a SiO2 nanofiber heat insulation layer, the phase-change substrate material adopts a hydrated salt, the gel packaging material comprises sodium carboxymethyl cellulose and a polymeric cross-linking material, the sodium carboxymethyl cellulose and the polymeric cross-linking material form an interpenetrating three-dimensional structure, the phase-change substrate material is packaged in pores of the packaging material, and the SiO2 nanofiber heat insulation layer is formed by the phase-change substrate material and the gel packaging material. Hydrated salt gel is formed, and the SiO2 nanofiber heat insulation layer is flatly laid and distributed in the hydrated salt gel; the hydrated salt gel is prepared from the following components in parts by mass: 5 to 10 parts of monomer, 0.5 to 4 parts of sodium carboxymethyl cellulose, 25 to 50 parts of hydrated salt, 0.12 to 0.35 part of cross-linking agent, 0.08 to 0.2 part of initiator and 40 to 60 parts of water; the invention relates to a suction-separation integrated thermal protection diaphragm for preparing a lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium battery protective materials technology, and more specifically, to a heat protection material for lithium-ion batteries that integrates absorption and separation of nanofibers and hydrated salt gels, its preparation method, and its application. Background Technology

[0002] Lithium-ion battery energy storage, with its advantages of high energy density, strong environmental adaptability, rapid grid response, and high integration, is leading the global energy transition towards green and low-carbon energy and playing a key role in addressing climate change. However, fires and explosions at energy storage power stations caused by lithium-ion batteries in recent years have become a major challenge limiting the large-scale development of battery energy storage technology. To address battery safety issues, numerous scholars have proposed the following solutions: first, intrinsic safety technologies based on internal battery materials; second, active safety early warning technologies based on runaway prevention; and third, passive protection technologies based on runaway thermal limitation. Thermal insulation is currently considered an economical and effective countermeasure to suppress the spread of battery thermal runaway.

[0003] Air cooling systems suffer from low temperature control efficiency due to their low thermal conductivity; liquid cooling solutions, while improving heat exchange efficiency, present leakage risks and structural complexity issues; heat pipe technology is constrained by high manufacturing costs and integration difficulties. Against this backdrop, thermal management technologies based on the phase change endothermic principle exhibit significant advantages due to their ability to achieve efficient thermal buffering without additional power consumption. Traditional organic phase change materials are flammable and have limited temperature control capabilities, while inorganic hydrated salts, as non-flammable phase change materials, possess two levels of endothermic characteristics, including phase change endothermics and thermochemical decomposition endothermics, resulting in high energy density. However, the common problems of overcooling and phase separation in hydrated salts lead to a decrease in their endothermic capacity, and their thermal response rate is difficult to match the rapid heat release characteristics of battery thermal runaway. Specifically, overcooling causes the material temperature to fall below the phase change point, preventing crystallization; phase separation causes the separation of crystal water and inorganic salts during thermal cycling, severely limiting the practical application of hydrated salts in battery thermal safety management. Currently, encapsulation methods (such as microcapsule encapsulation, porous material adsorption, and polymeric gel encapsulation) are effective ways to simultaneously solve the problems of phase separation and supercooling in hydrated salts. However, traditional hydrated salt phase change material encapsulation methods suffer from serious leakage and phase separation problems, and their thermal protection performance is limited to heat absorption or insulation, failing to achieve multi-dimensional battery thermal protection and resulting in poor battery thermal protection effects. Summary of the Invention

[0004] The technical problem to be solved by this invention is:

[0005] Existing hydrated salt phase change materials often only provide heat absorption or insulation protection, and cannot achieve multi-dimensional battery thermal protection.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] This invention provides a nanofiber-based hydrated salt gel, which is composed of a phase change substrate material, a gel encapsulation material, and a SiO2 nanofiber thermal insulation layer. The phase change substrate material is a hydrated salt, and the gel encapsulation material contains sodium carboxymethyl cellulose and a polymer crosslinker. The sodium carboxymethyl cellulose and the polymer crosslinker form an interpenetrating three-dimensional structure. The phase change substrate material is encapsulated in the pores of the encapsulation material to form the hydrated salt gel, and the SiO2 nanofiber thermal insulation layer is spread out in the hydrated salt gel.

[0008] The components of the hydrated salt gel, by mass fraction, include: 5-10 parts monomer, 0.5-4 parts sodium carboxymethyl cellulose, 25-50 parts hydrated salt, 0.12-0.35 parts crosslinking agent, 0.08-0.2 parts initiator, and 40-60 parts water.

[0009] Furthermore, the thickness of the SiO2 nanofiber insulation layer is 1–4 mm.

[0010] Furthermore, the thickness of the SiO2 nanofiber insulation layer is 2 mm.

[0011] Further, the monomer is one or more of acrylamide, acrylic acid, 2-hydroxyethyl methacrylate, N-isopropylacrylamide, methacrylate, or alginate.

[0012] Furthermore, the hydrated salt is one or more of sodium carbonate decahydrate, sodium sulfate decahydrate, disodium hydrogen phosphate dodecahydrate, calcium chloride hexahydrate, manganese nitrate hexahydrate, zinc nitrate hexahydrate, or ferric chloride hexahydrate.

[0013] Further, the crosslinking agent is one or more of N,N′-methylenebisacrylamide, polyethylene glycol diacrylate, hydroxymethylacrylamide, or bisphenol A diacrylate.

[0014] Furthermore, the initiator is one or more of ammonium persulfate, potassium persulfate, benzoyl peroxide, or sodium bisulfite.

[0015] This invention also provides a method for preparing nanofiber-based hydrated salt gel, comprising the following steps:

[0016] S1. Add 0.5 to 4 parts of sodium carboxymethyl cellulose to 40 to 60 parts of water by mass, mix well, and obtain a sodium carboxymethyl cellulose solution.

[0017] S2. Add 5-10 parts of monomer, 0.12-0.35 parts of crosslinking agent and 25-50 parts of hydrated salt to the sodium carboxymethyl cellulose solution, stir and mix to obtain a mixture;

[0018] S3. Add 0.08 to 0.2 parts of initiator to the mixture, stir evenly to obtain a sol;

[0019] S4. Spread 1-4 mm thick SiO2 nanofibers evenly into the sol, quickly pour into a mold, seal and shape, and let stand to obtain the nanofiber-based hydrated salt gel.

[0020] The present invention also provides an application of nanofiber-based hydrated salt gel, which is used to prepare an integrated heat-protective membrane for lithium-ion batteries.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] This invention overcomes the limitations of traditional phase change materials with their single function. It prepares an integrated absorbent and insulating nanofiber-based hydrated salt gel thermal protection material for lithium-ion batteries through chemical and physical cross-linking methods. Hydrated salt, with its dual heat absorption and flame retardant properties, serves as the heat-absorbing matrix. Combined with gel encapsulation technology, the hydrated salt is encapsulated. The gel not only uniformly disperses the hydrated salt, thus inhibiting phase separation, but its three-dimensional network also provides crystallization nucleation sites to reduce supercooling, contributing to improved energy storage performance. Simultaneously, it imparts excellent mechanical flexibility to the material. This invention also introduces SiO2 nanofibers to construct a multi-level porous thermal barrier, whose unique porous framework also provides crystallization nucleation sites for the hydrated salt. This achieves a dual heat absorption and heat insulation function for the nanofiber-based hydrated salt gel material, opening up new avenues for battery thermal safety management research. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the nanofiber-based hydrated salt gel structure in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the two-stage energy storage and heat absorption characteristics of hydrated salt in an embodiment of the present invention;

[0025] Figure 3 The figures shown are experimental results of thermal runaway of batteries in the embodiments of the present invention; wherein, (a) is an experimental result of thermal runaway of SiO2 nanofiber battery, (b) is an experimental result of thermal runaway of hydrated salt gel battery, and (c) is an experimental result of thermal runaway of nanofiber-based hydrated salt gel battery.

[0026] Figure 4 This is a comparison chart of the thermal cycling stability of gel-encapsulated hydrated salt and pure hydrated salt in the embodiments of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, exemplary embodiments or examples of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described embodiments or examples are merely some, not all, of the embodiments or examples of the present invention. All other embodiments or examples obtained by those skilled in the art based on the embodiments or examples of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0029] In a typical embodiment of the present invention, a nanofiber-based hydrated salt gel is provided, such as... Figure 1 As shown, the gel is composed of a phase change substrate material, a gel encapsulation material, and a SiO2 nanofiber thermal insulation layer. The phase change substrate material is a hydrated salt, and the gel encapsulation material contains sodium carboxymethyl cellulose and a polymer crosslinker. The sodium carboxymethyl cellulose and the polymer crosslinker form an interpenetrating three-dimensional structure. The phase change substrate material is encapsulated in the pores of the encapsulation material to form a hydrated salt gel, and the SiO2 nanofiber thermal insulation layer is spread out in the hydrated salt gel.

[0030] The components of the hydrated salt gel, by mass fraction, include: 5-10 parts monomer, 0.5-4 parts sodium carboxymethyl cellulose, 25-50 parts hydrated salt, 0.12-0.35 parts crosslinking agent, 0.08-0.2 parts initiator, and 40-60 parts water.

[0031] Preferably, the mass percentage of each component in the hydrated salt gel is: monomer 5%-10%, sodium carboxymethyl cellulose 0.5%-4%, hydrated salt 25%-50%, crosslinking agent 0.12%-0.35%, initiator 0.08%-0.2%, and the balance being water.

[0032] like Figure 2 As shown, the hydrated salt crystallization-melting phase transition process (first-stage endothermic) and the thermochemical decomposition endothermic reaction (second-stage endothermic) of this invention form a thermal buffer gradient. At temperatures above 100°C, the thermochemical decomposition endothermic reaction reaches as high as 1500 J / g, which meets the requirement of greater than 1100 J / g for thermal runaway in NCM batteries. This effectively prevents the spread of battery thermal runaway within the module and avoids the domino effect. Using a gel as an encapsulation carrier reduces the supercooling of the hydrated salt and inhibits phase separation. Both the gel and the hydrated salt have endothermic properties, and the nanofibers provide thermal insulation and porous framework support. Therefore, the nanofiber-based hydrated salt gel achieves multiple benefits in battery thermal protection.

[0033] As a preferred option, SiO2 nanofibers utilize existing SiO2 thermal insulation fibers with a hollow structure, patent number CN 202310413322.8. These fibers not only possess an ultra-low thermal conductivity of <40 mW / m·K, but their unique porous framework also provides nucleation sites for hydrated salts, thereby reducing supercooling.

[0034] As a preferred embodiment, the thickness of the SiO2 nanofiber thermal insulation layer of the present invention is 1-4 mm, and preferably, the thickness of the SiO2 nanofiber thermal insulation layer is 2 mm. A 1-4 mm thick SiO2 nanofiber thermal insulation layer enables the nanofiber-based hydrated salt gel to possess good thermal insulation properties and maintains good mechanical properties at high temperatures, thus playing a significant role in achieving the integrated heat absorption and insulation function of the nanofiber-based hydrated salt gel.

[0035] This invention uses hydrated salts as the heat-absorbing matrix material. The hydrated salts are those well known to those skilled in the art, including one or more of the following: sodium carbonate decahydrate, sodium sulfate decahydrate, disodium hydrogen phosphate dodecahydrate, calcium chloride hexahydrate, manganese nitrate hexahydrate, zinc nitrate hexahydrate, or ferric chloride hexahydrate.

[0036] A three-dimensional confined network was constructed using gel encapsulation technology, and hydrated salts were uniformly immobilized through nanocapillary action to solve the problems of supercooling and phase separation of hydrated salts.

[0037] This invention uses sodium carboxymethyl cellulose (CMC-Na) as a natural polymer backbone. An initial physical cross-linking network is formed through hydrogen bonds between hydroxyl and carboxyl groups. The monomers undergo free radical polymerization under the action of an initiator to form long chains of polymer cross-linked products, and a three-dimensional chemical cross-linking network is formed through covalent cross-linking with a cross-linking agent. An interpenetrating network structure is formed between sodium carboxymethyl cellulose and the polymer cross-linked products through hydrogen bonds, which retains the flexibility of the material while improving its mechanical strength.

[0038] The monomers, crosslinking agents, and initiators of the gel are well known to those skilled in the art. In a typical embodiment of the present invention, preferably, the monomer is one or more selected from acrylamide, acrylic acid, 2-hydroxyethyl methacrylate, N-isopropylacrylamide, methacrylate, or alginate. The crosslinking agent is one or more selected from N,N′-methylenebisacrylamide, polyethylene glycol diacrylate, hydroxymethylacrylamide, or bisphenol A diacrylate. The initiator is one or more selected from ammonium persulfate, potassium persulfate, benzoyl peroxide, or sodium bisulfite.

[0039] The surface active sites of the gel network can effectively reduce the nucleation energy barrier, while the hierarchical porous structure of the nanofibers provides heterogeneous nucleation sites for the crystallization of hydrated salts, synergistically increasing the phase transformation nucleation rate of hydrated salts.

[0040] In a typical embodiment of the present invention, a method for preparing a nanofiber-based hydrated salt gel is provided, comprising the following steps:

[0041] S1. Add 0.5 to 4 parts of sodium carboxymethyl cellulose to 40 to 60 parts of water by mass, mix well, and obtain a sodium carboxymethyl cellulose solution.

[0042] S2. Add 5-10 parts of monomer, 0.12-0.35 parts of crosslinking agent and 25-50 parts of hydrated salt to sodium carboxymethyl cellulose solution and stir to obtain a mixture.

[0043] S3. Add 0.08 to 0.2 parts of initiator to the mixture, stir evenly to obtain a sol;

[0044] S4. Spread 1-4 mm thick SiO2 nanofibers evenly into the sol, quickly pour into a mold, seal and shape, and let stand to obtain the nanofiber-based hydrated salt gel.

[0045] In a typical embodiment of the present invention, an application of a nanofiber-based hydrated salt gel is provided, wherein the nanofiber-based hydrated salt gel is used to prepare an integrated heat-protective membrane for lithium-ion batteries.

[0046] The beneficial effects of the present invention will be described below with reference to specific embodiments and comparative examples.

[0047] Example 1

[0048] This embodiment provides a method for preparing nanofiber-based hydrated salt gel, comprising the following steps:

[0049] S1. Add 2.5g of sodium carboxymethyl cellulose to 36.5g of water according to the mass fraction, and mix evenly at 70℃ to obtain a sodium carboxymethyl cellulose solution;

[0050] S2. Add 6g of acrylamide, 0.25g of N,N′-methylenebisacrylamide, and 46.5g of sodium carbonate decahydrate to the sodium carboxymethyl cellulose solution, and stir at 70℃ for 1h to obtain a mixture.

[0051] S3. Add 10 ml of 0.01 g / ml ammonium persulfate solution to the mixture, stir well to obtain a sol;

[0052] S4. Spread 2mm thick SiO2 nanofibers evenly into the sol, quickly pour into a mold, seal, place in a 70℃ constant temperature water bath, and polymerize by thermal initiation. Allow to cool statically to obtain nanofiber-based hydrated salt gel.

[0053] The preparation method of SiO2 nanofibers in this embodiment includes the following steps:

[0054] (1) Preparation of electrospinning precursor solution

[0055] Preparation of PVA spinning aid solution: First, weigh PVA powder and add it to a sealed reagent bottle containing a certain amount of deionized water. Let it swell at room temperature for 1 hour, then stir at high speed for 4 hours in a magnetic stirrer heated in an 80°C water bath to obtain a PVA solution with a concentration of 20wt%.

[0056] Preparation of SiO2 sol: TEOS was added dropwise to a phosphoric acid solution, wherein TEOS, H3PO4 and H2O were mixed in a molar ratio of 1:0.009:8. Under acidic conditions, TEOS underwent a hydrolysis-condensation reaction to form SiO2 sol. The solution was stirred at room temperature for 8 hours to obtain a colorless and transparent SiO2 sol.

[0057] Preparation of electrospinning precursor solution: SiO2 sol and PVA spinning aid solution were mixed and stirred for 8 hours at a mass ratio of 0.9:1. Simultaneously, surfactant CTAB was added to the solution, wherein the mass ratio of CTAB to TEOS required to prepare the SiO2 sol mixed with PVA spinning aid solution in this step was 0.02:1. Then, a certain mass of paraffin oil was added, wherein the mass ratio of CTAB to paraffin oil was 6:1. The mixed solution was then stirred at high speed for 8 hours to obtain a white microemulsion electrospinning precursor solution.

[0058] (2) Electrospinning

[0059] The prepared precursor solution was injected into the syringe of the electrospinning machine for electrospinning. As electrospinning proceeded, the SiO2-PVA-paraffin oil composite fibers were stacked alternately on the receiver to form a composite fiber membrane. After spinning, the composite fiber membrane on the receiver was removed and placed in an electric thermostatic drying oven at 80°C for 2 hours to remove moisture from the fibers.

[0060] (3) High-temperature calcination

[0061] The dried composite fiber membrane was placed in a muffle furnace and heated to 700°C at a rate of 5°C / min, and then held at that temperature for 3 hours to obtain hollow tubular SiO2 nanofibers that were stacked in an alternating manner.

[0062] Example 2

[0063] This embodiment provides a method for preparing nanofiber-based hydrated salt gel, which differs from Example 1 in that:

[0064] S1. Add 0.5g of sodium carboxymethyl cellulose to 31.5g of water by mass, and mix evenly at 70℃ to obtain a sodium carboxymethyl cellulose solution.

[0065] S2. Add 10g acrylamide, 0.35g N,N′methylenebisacrylamide, and 50g sodium carbonate decahydrate to the sodium carboxymethyl cellulose solution, and stir at 70℃ for 1h to obtain a mixture.

[0066] S3. Add 10 ml of 0.02 g / ml ammonium persulfate solution to the mixture, stir well to obtain a sol;

[0067] S4. Spread 2mm thick SiO2 nanofibers evenly into the sol, quickly pour into a mold, seal, place in a 70℃ constant temperature water bath, and polymerize by thermal initiation. Allow to cool statically to obtain nanofiber-based hydrated salt gel.

[0068] Example 3

[0069] This embodiment provides a method for preparing nanofiber-based hydrated salt gel, which differs from Example 1 in that:

[0070] S1. Add 4g of sodium carboxymethyl cellulose to 50g of water according to the mass fraction, and mix evenly at 70℃ to obtain a sodium carboxymethyl cellulose solution.

[0071] S2. Add 5g acrylamide, 0.12g N,N′methylenebisacrylamide, and 25g sodium carbonate decahydrate to the sodium carboxymethyl cellulose solution, and stir at 70℃ for 1h to obtain a mixture.

[0072] S3. Add 10 ml of 0.008 g / ml ammonium persulfate solution to the mixture, stir well to obtain a sol;

[0073] S4. Spread 2mm thick SiO2 nanofibers evenly into the sol, quickly pour into a mold, seal, place in a 70℃ constant temperature water bath, and polymerize by thermal initiation. Allow to cool statically to obtain nanofiber-based hydrated salt gel.

[0074] Example 4

[0075] This embodiment provides a method for preparing nanofiber-based hydrated salt gel, which differs from Example 1 in that:

[0076] S1. Add 5g of sodium carboxymethyl cellulose to 57g of water according to the mass fraction, and mix evenly at 70℃ to obtain a sodium carboxymethyl cellulose solution.

[0077] S2. Add 4.5g acrylamide, 0.35g N,N′methylenebisacrylamide, and 25g sodium carbonate decahydrate to the sodium carboxymethyl cellulose solution, and stir at 70℃ for 1h to obtain a mixture.

[0078] S3. Add 10 ml of 0.01 g / ml ammonium persulfate solution to the mixture, stir well to obtain a sol;

[0079] S4. Spread 2mm thick SiO2 nanofibers evenly into the sol, quickly pour into a mold, seal, place in a 70℃ constant temperature water bath, and polymerize by thermal initiation. Allow to cool statically to obtain nanofiber-based hydrated salt gel.

[0080] Comparative Example 1

[0081] This comparative example provides a method for preparing nanofiber-based hydrated salt gels, which differs from Example 1 in that:

[0082] S1. Add 6g of acrylamide, 0.25g of N,N′-methylenebisacrylamide, and 46.5g of sodium carbonate decahydrate to 37.2g of water according to the mass fractions, and stir at 70℃ for 1h to obtain a mixture;

[0083] S2. Add 10 ml of 0.01 g / ml ammonium persulfate solution to the mixture, stir well to obtain a sol;

[0084] S3. Spread 2mm thick SiO2 nanofibers evenly into the sol, quickly pour into a mold, seal, place in a 70℃ constant temperature water bath, and polymerize by thermal initiation. Allow to cool statically to obtain nanofiber-based hydrated salt gel.

[0085] Comparative Example 2

[0086] This comparative example provides a method for preparing hydrated salt gel, comprising the following steps:

[0087] S1. Add 2.5g of sodium carboxymethyl cellulose to 36.5g of water according to the mass fraction, and mix evenly at 70℃ to obtain a sodium carboxymethyl cellulose solution;

[0088] S2. Add 6g of acrylamide, 0.25g of N,N′-methylenebisacrylamide, and 46.5g of sodium carbonate decahydrate to the sodium carboxymethyl cellulose solution, and stir at 70℃ for 1h to obtain a mixture.

[0089] S3. Add 10 ml of 0.01 g / ml ammonium persulfate solution to the mixture, stir well to obtain a sol;

[0090] S4. Quickly pour the sol into the mold, seal it, and place it in a 70°C constant temperature water bath. Polymerize by thermal initiation, and let it cool to obtain hydrated salt gel.

[0091] Example 5

[0092] The heated nanofiber-based hydrated salt gels of Examples 1 to 4, Comparative Example 1, and pure hydrated sodium carbonate decahydrate were placed in a constant temperature chamber for cooling experiments. The results are shown in Table 1. It can be seen that the supercooling degree of sodium carbonate decahydrate is 7.1℃, while the supercooling degree of the nanofiber-based hydrated salt gel and the hydrated salt gel of Example 1 is significantly reduced to 0℃, which is much smaller than the supercooling degree of pure hydrated sodium carbonate decahydrate.

[0093] Table 1

[0094] Supercooling (°C) Example 1 0 Example 2 0.2 Example 3 0.1 Example 4 0.9 Comparative Example 1 1.2 Pure water salt 7.1

[0095] Example 6

[0096] The nanofiber-based hydrated salt gels of Examples 1, 4, and Comparative Example 1, as well as pure hydrated salt sodium carbonate decahydrate, were placed in a constant temperature chamber for leakage experiments. The results are as follows: Figure 4 As shown, after being kept at different temperatures for 40 minutes, it can be seen that pure hydrated salts lose water at the phase transition temperature (37°C) and become almost pure liquid above the phase transition temperature (55°C), while the nanofiber-based hydrated salt gel of Example 1 basically maintains a stable morphology.

[0097] Example 7

[0098] The SiO2 nanofibers of Example 1, the nanofiber-based hydrated salt gel of Example 1, and the hydrated salt gel of Comparative Example 2 were placed in the gap between the triggered thermal runaway battery and the affected battery for thermal runaway experiments. Constant current overcharging was performed until the triggered battery experienced thermal runaway. The front and rear temperatures of the triggered battery and the experimental battery were monitored throughout the process using a type K thermocouple. The results are as follows: Figure 3 As shown, the highest temperature of the affected battery with inserted nanofibers is 144℃, the highest temperature of the affected battery with inserted hydrated salt gel is 75.6℃, and the highest temperature of the affected battery with inserted nanofiber-based hydrated salt gel is 65℃. It can be seen that the nanofiber-based hydrated salt gel has both heat absorption and heat insulation effects, and can successfully block the propagation of thermal runaway in the battery.

[0099] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A nanofiber-based hydrated salt gel, characterized in that, The nanofiber-based hydrated salt gel is composed of a phase change substrate material, a gel encapsulation material, and a SiO2 nanofiber thermal insulation layer. The phase change substrate material is a hydrated salt, and the gel encapsulation material contains sodium carboxymethyl cellulose and a polymer crosslinker. The sodium carboxymethyl cellulose and the polymer crosslinker form an interpenetrating three-dimensional structure. The phase change substrate material is encapsulated in the pores of the encapsulation material to form a hydrated salt gel. The SiO2 nanofiber thermal insulation layer is spread out in the hydrated salt gel. The components of the hydrated salt gel, by mass fraction, include: 5-10 parts monomer, 0.5-4 parts sodium carboxymethyl cellulose, 25-50 parts hydrated salt, 0.12-0.35 parts crosslinking agent, 0.08-0.2 parts initiator, and 40-60 parts water.

2. The nanofiber-based hydrated salt gel according to claim 1, characterized in that, The thickness of the SiO2 nanofiber insulation layer is 1–4 mm.

3. The nanofiber-based hydrated salt gel according to claim 2, characterized in that, The thickness of the SiO2 nanofiber insulation layer is 2 mm.

4. The nanofiber-based hydrated salt gel according to claim 2, characterized in that, The monomer is one or more of acrylamide, acrylic acid, 2-hydroxyethyl methacrylate, N-isopropylacrylamide, methacrylate, or alginate.

5. The nanofiber-based hydrated salt gel according to claim 4, characterized in that, The hydrated salt is one or more of sodium carbonate decahydrate, sodium sulfate decahydrate, disodium hydrogen phosphate dodecahydrate, calcium chloride hexahydrate, manganese nitrate hexahydrate, zinc nitrate hexahydrate, or ferric chloride hexahydrate.

6. The nanofiber-based hydrated salt gel according to claim 5, characterized in that, The crosslinking agent is one or more of N,N′methylenebisacrylamide, polyethylene glycol diacrylate, hydroxymethylacrylamide, or bisphenol A diacrylate.

7. The nanofiber-based hydrated salt gel according to claim 6, characterized in that, The initiator is one or more of ammonium persulfate, potassium persulfate, benzoyl peroxide, or sodium bisulfite.

8. A method for preparing a nanofiber-based hydrated salt gel, characterized in that, Includes the following steps: S1. Add 0.5 to 4 parts of sodium carboxymethyl cellulose to 40 to 60 parts of water by mass, mix well, and obtain a sodium carboxymethyl cellulose solution. S2. Add 5-10 parts of monomer, 0.12-0.35 parts of crosslinking agent and 25-50 parts of hydrated salt to the sodium carboxymethyl cellulose solution, stir and mix to obtain a mixture; S3. Add 0.08 to 0.2 parts of initiator to the mixture, stir evenly to obtain a sol; S4. Spread 1-4 mm thick SiO2 nanofibers evenly into the sol, quickly pour into a mold, seal and shape, and let stand to obtain the nanofiber-based hydrated salt gel.

9. The application of the nanofiber-based hydrated salt gel according to any one of claims 1 to 7, characterized in that, The nanofiber-based hydrated salt gel is used to prepare an integrated heat-protective membrane for lithium-ion batteries.

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