Hydrated salt thermal chemical heat storage gel with thermal switch characteristic and high heat storage density as well as preparation method and application of hydrated salt thermal chemical heat storage gel

Abstract

The invention provides hydrated salt thermal chemical heat storage gel with thermal switch characteristics and high heat storage density as well as a preparation method and application thereof, and belongs to the technical field of heat storage materials. The hydrated salt thermochemical heat storage gel with the thermal switch characteristic and high heat storage density is prepared from the following raw materials in percentage by mass: 60 to 90 percent of hydrated salt, 5 to 30 percent of monomer, 0.1 to 10 percent of cross-linking agent and 0.1 to 10 percent of initiator. The hydrated salt has the characteristics of phase change and thermochemical decomposition and is high in heat storage density, so that the heat storage density of the hydrated salt thermochemical heat storage gel is improved; according to the invention, monomers are adopted, can form a network structure, are used as a framework of the hydrated salt thermochemical heat storage gel, and are carbonized at high temperature to form a porous structure, so that the heat conductivity is reduced, the heat conductivity switching characteristic is realized, and the risk of thermal runaway propagation of a battery module is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat storage materials, and in particular relates to a hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density, as well as a preparation method and application thereof. Background Art

[0002] Thermal runaway refers to a dramatic rise in battery temperature caused by mechanical shock, overheating, or overcharging, which can easily lead to accidents such as fire and explosion. Thermal runaway within a battery pack can easily heat adjacent cells to temperatures exceeding 150°C, triggering the spread of thermal runaway and escalating the risk of fire and explosion.

[0003] Currently, most commercial battery thermal runaway protection materials are aerogel insulation, which utilizes the insulation effect of low-thermal-conductivity materials to reduce the temperature of adjacent batteries and delay thermal runaway. However, relying solely on aerogel insulation within densely packed battery packs can trap heat in the middle, preventing it from dissipating, further increasing the temperature and exacerbating the severity of thermal runaway. The high-temperature heat source will continue to heat adjacent batteries until the heat penetrates, triggering thermal runaway in the adjacent batteries. Therefore, for high-energy-density batteries, thermal insulation can usually only delay the spread of thermal runaway, but cannot prevent it from spreading.

[0004] The use of heat storage materials for thermal runaway protection is a technical means of achieving thermal runaway protection by absorbing the heat generated by thermal runaway batteries, reducing the battery temperature, and thus reducing the temperature of adjacent batteries to below 150°C. Since the high-temperature heat source of the battery is eliminated, its thermal runaway protection effect is more thorough. However, existing thermochemical heat storage materials are mostly rigid and hard materials that cannot effectively resist the expansion of the battery. Their heat storage density is less than 1000kJ / kg, and it is difficult to deal with the problem of battery thermal runaway propagation. Therefore, how to increase the heat storage density of heat storage materials while effectively reducing the risk of thermal runaway propagation in battery modules has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The present invention aims to provide a hydrated salt thermochemical thermal storage gel with thermal switching properties and high heat storage density, as well as its preparation method and application. The hydrated salt thermochemical thermal storage gel provided by the present invention has a high heat storage density and, upon carbonization at high temperatures, a thermal conductivity of >0.4 W / (m·K) that drops sharply to 0.03-0.1 W / (m·K), exhibiting a thermal conductivity switching property that effectively reduces the risk of thermal runaway propagation in battery modules.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The invention provides a hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density. The gel is prepared from raw materials comprising the following weight contents: 60-90% of hydrated salt, 5-30% of monomer, 0.1-10% of cross-linking agent and 0.1-10% of initiator.

[0008] Preferably, the invention is prepared from raw materials comprising the following contents by weight: 65-85% of hydrated salt, 10-25% of monomer, 0.5-8% of cross-linking agent and 0.5-8% of initiator.

[0009] Preferably, the hydrated salt is at least one of disodium hydrogen phosphate dodecahydrate, magnesium sulfate heptahydrate, potassium aluminum sulfate dodecahydrate, oxalic acid dihydrate, sodium acetate trihydrate, magnesium chloride hexahydrate, strontium chloride hexahydrate, barium hydroxide octahydrate, ammonium aluminum sulfate dodecahydrate, magnesium nitrate hexahydrate and sodium sulfate decahydrate.

[0010] Preferably, the monomer is at least one of sodium alginate, calcium alginate, sodium acrylate, acrylic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid and acrylamide.

[0011] Preferably, the initiator is at least one of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, ammonium persulfate and α-ketoglutaric acid.

[0012] Preferably, the cross-linking agent is one or more of N,N-methylenebisacrylamide, 1,4-butylene glycol diacrylate, zinc sulfate and boric acid.

[0013] The present invention also provides a method for preparing the hydrated salt thermochemical heat storage gel having thermal switching characteristics and high heat storage density as described in the above technical solution, comprising the following steps:

[0014] The hydrated salt is melted, and then a monomer, an initiator and a cross-linking agent are added to carry out a polymerization reaction to obtain a hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density.

[0015] Preferably, the melting temperature is 60-95°C.

[0016] Preferably, the polymerization reaction is carried out under illumination or heating and stirring conditions; the wavelength of the illumination is 365 nm, the power of the illumination is 1 to 200 W, and the illumination time is 0.5 to 15 min; the temperature of the heating and stirring is 70 to 95° C., the heating and stirring rate is 300 to 600 r / min, and the heating and stirring time is 0.1 to 1 h.

[0017] The present invention also provides the use of the hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density described in the above technical solution, or the hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density prepared by the preparation method of the above technical solution in cylindrical batteries, soft-pack batteries, lithium-ion batteries, sodium-ion batteries or solid-state batteries.

[0018] The present invention provides a hydrated salt thermochemical heat storage gel with thermal switching properties and high heat storage density. The gel is prepared from raw materials comprising the following mass contents: 60-90% hydrated salt, 5-30% monomer, 0.1-10% crosslinker, and 0.1-10% initiator. The present invention uses hydrated salts, which have phase change and thermochemical decomposition properties and inherently have a high heat storage density, thereby increasing the heat storage density of the hydrated salt thermochemical heat storage gel. The present invention also uses monomers, which form a network structure as the skeleton of the hydrated salt thermochemical heat storage gel. At high temperatures, the hydrated salt thermochemical heat storage gel carbonizes to form a porous structure, thereby reducing thermal conductivity and achieving thermal conductivity switching properties, thereby effectively reducing the risk of thermal runaway propagation in battery modules. Experimental results show that the sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel provided by the present invention is as high as 1828kJ / kg, and the density is greater than 1.0g / cm 3 , the volume heat storage density is as high as 2833MJ / m 3 ; After the thermal runaway test, the thermal conductivity will drop from >0.4W / m·K to 0.03~0.1W / m·K. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The single-axis differential scanning calorimetry diagram of the hydrated salt thermochemical heat storage gel prepared in Example 1;

[0020] Figure 2 This is a comparison chart of the maximum surface temperature of each battery after thermal runaway of a battery pack protected by the hydrated salt thermochemical heat storage gel prepared in Example 1 and the commercial aerogel of Comparative Example 1;

[0021] Figure 3 This is a picture of a battery module protected by the hydrated salt thermochemical heat storage gel prepared in Example 1 after thermal runaway;

[0022] Figure 4 This is a picture of a battery module protected by commercial aerogel in Comparative Example 1 after thermal runaway;

[0023] Figure 5 The thermal conductivity test results of the hydrated salt thermochemical heat storage gel prepared in Example 1 before and after the thermal runaway test. DETAILED DESCRIPTION

[0024] The invention provides a hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density. The gel is prepared from raw materials comprising the following weight contents: 60-90% of hydrated salt, 5-30% of monomer, 0.1-10% of cross-linking agent and 0.1-10% of initiator.

[0025] The present invention has no particular limitation on the sources of the raw materials, and commercially available products known to those skilled in the art may be used.

[0026] The raw materials used to prepare the hydrated salt thermochemical heat storage gel of the present invention, which has thermal switching properties and a high heat storage density, comprise 60-90% hydrated salt by weight. In the present invention, the hydrated salt exhibits phase transition and thermochemical decomposition properties and inherently has a high heat storage density, thereby increasing the heat storage density of the hydrated salt thermochemical heat storage gel.

[0027] As an embodiment, the mass content of the hydrated salt may be 65-85%, or may be 70%, 73%, 75% or 80%.

[0028] In the present invention, the hydrated salt is preferably at least one of disodium hydrogen phosphate dodecahydrate, magnesium sulfate heptahydrate, potassium aluminum sulfate dodecahydrate, oxalic acid dihydrate, sodium acetate trihydrate, magnesium chloride hexahydrate, strontium chloride hexahydrate, barium hydroxide octahydrate, ammonium aluminum sulfate dodecahydrate, magnesium nitrate hexahydrate, and sodium sulfate decahydrate, and more preferably two of disodium hydrogen phosphate dodecahydrate, magnesium sulfate heptahydrate, potassium aluminum sulfate dodecahydrate, oxalic acid dihydrate, sodium acetate trihydrate, magnesium chloride hexahydrate, strontium chloride hexahydrate, barium hydroxide octahydrate, ammonium aluminum sulfate dodecahydrate, magnesium nitrate hexahydrate, and sodium sulfate decahydrate. Using two of the hydrated salts in the present invention can further increase the heat storage density compared to using only one.

[0029] In the present invention, when the hydrated salt is barium hydroxide octahydrate and magnesium nitrate hexahydrate, the mass ratio of the barium hydroxide octahydrate to the magnesium nitrate hexahydrate is preferably 4:1.

[0030] In the present invention, when the hydrated salt is sodium sulfate decahydrate and ammonium aluminum sulfate dodecahydrate, the mass ratio of the sodium sulfate decahydrate to the ammonium aluminum sulfate dodecahydrate is preferably 1:4.

[0031] In the present invention, when the hydrated salt is oxalic acid dihydrate and sodium acetate trihydrate, the mass ratio of the oxalic acid dihydrate to the sodium acetate trihydrate is preferably 1:1.

[0032] In the present invention, when the hydrated salt is magnesium nitrate hexahydrate and sodium sulfate decahydrate, the mass ratio of the magnesium nitrate hexahydrate to the sodium sulfate decahydrate is preferably 1:1.

[0033] In the present invention, when the hydrated salt is barium hydroxide octahydrate and magnesium chloride hexahydrate, the mass ratio of the barium hydroxide octahydrate and the magnesium chloride hexahydrate is preferably 1:1.

[0034] The raw materials used to prepare the hydrated salt thermochemical heat storage gel with thermal switching properties and high heat storage density described herein comprise 5-30% monomers by weight. In the present invention, the monomers form a network structure that serves as the backbone of the hydrated salt thermochemical heat storage gel. At high temperatures, they carbonize to form a porous structure, thereby reducing thermal conductivity and achieving thermal conductivity switching properties, thereby effectively reducing the risk of thermal runaway propagation in the battery module.

[0035] As an embodiment, the mass content of the monomer can be 10-28%, or can be 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26% or 27%.

[0036] In the present invention, the monomer is preferably at least one of sodium alginate, calcium alginate, sodium acrylate, acrylic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, and acrylamide, and more preferably two of the group consisting of sodium alginate, calcium alginate, sodium acrylate, acrylic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, and acrylamide. In the present invention, using two of the above monomers can further improve the thermal conductivity switching characteristics.

[0037] In the present invention, when the monomers are sodium acrylate and sodium alginate, the mass ratio of sodium acrylate to sodium alginate is preferably 1:10 to 10:1, more preferably 3:1.

[0038] In the present invention, when the monomers are sodium alginate and acrylamide, the mass ratio of sodium alginate to acrylamide is preferably 1:1.

[0039] In the present invention, when the monomers are acrylic acid and 2-acrylamido-2-methyl-1-propanesulfonic acid, the mass ratio of acrylic acid to 2-acrylamido-2-methyl-1-propanesulfonic acid is preferably 1:1.

[0040] In the present invention, when the monomers are acrylic acid and sodium acrylate, the mass ratio of acrylic acid to sodium acrylate is preferably 1:1.

[0041] The raw materials used to prepare the hydrated salt thermochemical heat storage gel with thermal switching properties and high heat storage density described herein include, by weight, 0.1-10% of a crosslinker; the crosslinker is preferably one or more of N,N-methylenebisacrylamide, 1,4-butylene glycol diacrylate, zinc sulfate, and boric acid. In the present invention, the crosslinker can form chemical bonds between linear molecules, connecting them to form a network structure.

[0042] As an embodiment, the mass content of the cross-linking agent may be 0.5-8%, or may be 1%, 2%, 3%, 4%, 5%, 6% or 7%.

[0043] The raw materials for preparing the hydrated salt thermochemical heat storage gel with thermal switch characteristics and high heat storage density of the present invention include 0.1-10% of initiator by weight. In the present invention, the initiator can initiate monomer polymerization reaction.

[0044] As an embodiment, the mass content of the initiator can be 0.5-8%, or can be 1%, 2%, 3%, 4%, 5%, 6% or 7%.

[0045] In the present invention, the initiator is preferably at least one of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, ammonium persulfate, and α-ketoglutaric acid, and more preferably two of these. In the present invention, using two of the above initiators can further increase the degree of polymerization, thereby improving the performance of the hydrated salt thermochemical heat storage gel.

[0046] In the present invention, when the initiators are α-ketoglutaric acid and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, the mass ratio of the α-ketoglutaric acid to the 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone is preferably 1:1.

[0047] The hydrated salt thermochemical heat storage gel proposed in this invention is solid at room temperature and elastic at 30-70°C, which can effectively resist the expansion caused by high temperature of the battery and avoid the loss of active ingredients; the density is greater than 1.0g / cm 3 The sum of phase change energy storage and thermochemical energy storage density is as high as 1828kJ / kg, and the volume heat storage density is as high as 2833MJ / m 3 , with strong heat absorption capacity, it can effectively absorb the heat released by battery thermal runaway, quickly reduce the temperature of the battery, and reduce the risk of thermal runaway propagation; under normal operating conditions, the hydrated salt thermochemical heat storage gel can maintain a high thermal conductivity (>0.4W / m·K) and maintain the uniformity of the battery module temperature. After the battery thermal runaway occurs, the hydrated salt thermochemical heat storage gel is carbonized and the thermal conductivity drops sharply to 0.03~0.1W / m·K, showing a thermal conductivity switching characteristic, which can greatly reduce the heat conduction between thermal runaway and normal batteries; at high temperatures, it will release a large amount of asphyxiating gas, dilute the oxygen concentration in the surrounding environment, and suppress the flame of the thermal runaway battery, which is expected to play an important role in the battery field.

[0048] The hydrated salt thermochemical heat storage gel provided by the present invention has abundant raw material sources and low cost, and has broad application prospects and market potential in energy storage and battery thermal protection.

[0049] The hydrated salt thermochemical heat storage gel provided by the present invention has a stable morphology, a thermal conductivity switching characteristic, and a volume heat storage density higher than that of water. The hydrated salt used in the present invention has excellent phase change-decomposition heat absorption capacity, and simultaneously decomposes to release a large amount of gas, enabling it to quickly cool objects and dilute the oxygen concentration in the environment in which the objects are located, thus having an intelligent thermal conductivity switching characteristic.

[0050] The present invention also provides a method for preparing the hydrated salt thermochemical heat storage gel having thermal switching characteristics and high heat storage density as described in the above technical solution, comprising the following steps:

[0051] The hydrated salt is melted, and then a monomer, an initiator and a cross-linking agent are added to carry out a polymerization reaction to obtain a hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density.

[0052] In the present invention, the melting temperature is preferably 60-95° C. As an embodiment, the melting temperature can be 65° C., 70° C., 75° C., 80° C., 85° C. or 90° C. The present invention has no particular limitation on the melting time, as long as the hydrated salt is completely melted.

[0053] The present invention has no particular limitation on the operation of adding the monomer, initiator and cross-linking agent, and the mixture is stirred until the solution becomes clear.

[0054] In the present invention, the polymerization reaction is preferably carried out under illumination or heating and stirring conditions; the wavelength of the illumination is preferably 365 nm; the power of the illumination is preferably 1 to 200 W; the time of the illumination is preferably 0.5 to 15 min; the temperature of the heating and stirring is preferably 70 to 95° C.; the rate of the heating and stirring is preferably 300 to 600 r / min; and the time of the heating and stirring is preferably 0.1 to 1 h.

[0055] As an embodiment, the illumination time can be 1 to 10 minutes, or 3 to 5 minutes; the illumination power can be 120 to 150W; the heating and stirring temperature can be 75 to 90°C, or 80 to 85°C; the heating and stirring rate can be 400 to 500 r / min; the heating and stirring time can be 0.2 to 0.8 hours, or 0.4 to 0.6 hours.

[0056] The preparation method provided by the invention has simple process.

[0057] The present invention also provides the use of the hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density described in the above technical solution, or the hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density prepared by the preparation method of the above technical solution in cylindrical batteries, soft-pack batteries, lithium-ion batteries, sodium-ion batteries or solid-state batteries.

[0058] The present invention has no particular limitation on the specific manner of application, and the application may be performed in a manner well known to those skilled in the art.

[0059] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0060] Example 1

[0061] A hydrated salt thermochemical heat storage gel is prepared from the following raw materials by weight: 80% hydrated salt, 15% monomer, 4% cross-linking agent and 1% initiator;

[0062] The hydrated salt is barium hydroxide octahydrate and magnesium nitrate hexahydrate, and the mass ratio of the barium hydroxide octahydrate to the magnesium nitrate hexahydrate is 4:1;

[0063] The monomers are sodium acrylate and sodium alginate, and the mass ratio of sodium acrylate to sodium alginate is 3:1;

[0064] The cross-linking agent is zinc sulfate;

[0065] The initiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone;

[0066] The preparation method of the hydrated salt thermochemical heat storage gel comprises the following steps:

[0067] The hydrated salt is melted at 90°C, and then a monomer is added, followed by an initiator and a cross-linking agent, and stirred until clarified. After that, a polymerization reaction is carried out to obtain a hydrated salt thermochemical heat storage gel; wherein, the polymerization reaction is carried out under light conditions; the wavelength of the light is 365nm, the power of the light is 200W, and the light time is 5 minutes.

[0068] The single-axis differential scanning calorimetry (DSC) of the hydrated salt thermochemical heat storage gel prepared in Example 1 is as follows: Figure 1 shown.

[0069] from Figure 1 It can be seen that the hydrated salt thermochemical heat storage gel undergoes a phase transition at around 51°C.

[0070] Combined with DSC software analysis, it can be seen that the sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical thermal storage gel with thermal switching characteristics and high heat storage density is 1828kJ / kg, and the density is 1.55g / cm 3 , the volume heat storage density is 2833MJ / m 3 , than the evaporation enthalpy per unit volume of water (2200MJ / m 3 ) is high and has super heat absorption capacity.

[0071] Comparative Example 1

[0072] Commercial aerogel Guangdong Alison High-tech Technology Co., Ltd., thermal conductivity is 0.025W / (m·K)

[0073] Six 51Ah ternary lithium-ion batteries (corresponding to No. 1 to No. 6 lithium-ion batteries) from the Ningde era were placed side by side. A 2mm thick piece of hydrated salt thermochemical heat storage gel prepared in Example 1 or the commercial aerogel of Comparative Example 1 was placed between the batteries. A needle punch was used to pierce the center of the side of No. 3 battery to induce thermal runaway. The surface temperature and voltage of the large surface of the battery were recorded in real time by thermocouples and voltage lines, and the thermal runaway of the battery was observed. The results are as follows: Figures 2 to 5 shown.

[0074] Figure 2 This is a comparison chart of the maximum surface temperature of each battery after thermal runaway of a battery pack protected by the hydrated salt thermochemical heat storage gel prepared in Example 1 and the commercial aerogel of Comparative Example 1;

[0075] Figure 3 This is a picture of a battery module protected by the hydrated salt thermochemical heat storage gel prepared in Example 1 after thermal runaway; Figure 4 This is a picture of a battery module protected by commercial aerogel in Comparative Example 1 after thermal runaway; Figure 5 The thermal conductivity test results of the hydrated salt thermochemical heat storage gel prepared in Example 1 before and after the thermal runaway test.

[0076] from Figures 2-4 It can be seen that commercial aerogel cannot effectively suppress the propagation of thermal runaway of the battery module, but hydrated salt thermochemical heat storage gel can effectively suppress it; the overall temperature of the battery module protected by hydrated salt thermochemical heat storage gel is much lower than that of the aerogel module, indicating that hydrated salt thermochemical heat storage gel can effectively reduce the temperature of the battery module.

[0077] from Figure 5It can be seen that after the thermal runaway test, the thermal conductivity of the hydrated salt thermochemical heat storage gel will decrease from 0.52W / (m·K) to 0.056W / (m·K), that is, after the thermal runaway experiment, the thermal conductivity of the hydrated salt thermochemical heat storage gel will drop significantly to 10.8% of the initial value, which will greatly reduce the heat conduction between the thermal runaway battery and the normal battery, and reduce the risk of thermal runaway propagation.

[0078] Example 2

[0079] A hydrated salt thermochemical heat storage gel is prepared from the following raw materials by weight: 80% hydrated salt, 17% monomer, 1% initiator and 2% cross-linking agent;

[0080] The hydrated salts are sodium sulfate decahydrate and ammonium aluminum sulfate dodecahydrate, and the mass ratio of sodium sulfate decahydrate to ammonium aluminum sulfate dodecahydrate is 1:4;

[0081] The monomer is acrylamide;

[0082] The initiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone;

[0083] The cross-linking agent is N,N-methylenebisacrylamide;

[0084] The preparation method of the hydrated salt thermochemical heat storage gel comprises the following steps:

[0085] The hydrated salt is melted at 90°C, and then a monomer is added, followed by an initiator and a cross-linking agent, and stirred until clarified. After that, a polymerization reaction is carried out to obtain a hydrated salt thermochemical heat storage gel; wherein, the polymerization reaction is carried out under light conditions; the wavelength of the light is 365nm, the power of the light is 120W, and the light time is 1 minute.

[0086] Combined with DSC software analysis, it can be seen that the sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel in Example 2 is 1458 kJ / kg, and the density is 1.5 g / cm 3 , with super heat absorption capacity and volume heat storage density of 2187MJ / m 3 ;The thermal conductivity is 0.52W / m·K at room temperature, and drops to 0.038W / m·K after heating at 800℃.

[0087] Example 3

[0088] On the basis of Example 1, the hydrated salt was replaced with barium hydroxide octahydrate and magnesium chloride hexahydrate, the mass ratio of barium hydroxide octahydrate to magnesium chloride hexahydrate was 1:1, and other conditions remained unchanged.

[0089] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 3 is 1123 kJ / kg, and the density is 1.6 g / cm 3 , the volume heat storage density is 1796.8MJ / m 3 ;The thermal conductivity is 0.6W / m·K at room temperature, and drops to 0.054W / m·K after heating at 800℃.

[0090] Example 4

[0091] On the basis of Example 1, the hydrated salt was replaced with barium hydroxide octahydrate, and other conditions remained unchanged to obtain a hydrated salt thermochemical heat storage gel.

[0092] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 4 is 1031 kJ / kg, and the density is 1.8 g / cm 3 , has super heat absorption capacity, and the volume heat storage density is 1885MJ / m 3 ;The thermal conductivity is 0.63W / m·K at room temperature, and drops to 0.054W / m·K after heating at 800℃.

[0093] Example 5

[0094] On the basis of Example 1, the hydrated salt was replaced with oxalic acid dihydrate and sodium acetate trihydrate, the mass ratio of oxalic acid dihydrate to sodium acetate trihydrate was 1:1, and other conditions remained unchanged.

[0095] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 5 is 936 kJ / kg, and the density is 1.4 g / cm 3 , the volume heat storage density is 1310MJ / m 3 The thermal conductivity is 0.82W / m·K at room temperature, and drops to 0.037W / m·K after heating at 800℃.

[0096] Example 6

[0097] Based on Example 5, oxalic acid dihydrate was omitted, the hydrated salt content remained unchanged, and other conditions remained unchanged.

[0098] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 6 is 734 kJ / kg, and the density is 1.4 g / cm 3 , the volume heat storage density is 1027MJ / m 3 , the thermal conductivity is 0.82W / m·K at room temperature, and the thermal conductivity drops to 0.1W / m·K after heating at 800℃;

[0099] Example 7

[0100] On the basis of Example 5, sodium acetate trihydrate was omitted, the hydrated salt content remained unchanged, and other conditions remained unchanged.

[0101] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 7 is 1245 kJ / kg, and the density is 1.45 g / cm 3 , the volume heat storage density is 1805MJ / m 3 The thermal conductivity is 0.67W / m·K at room temperature, and drops to 0.06W / m·K after heating at 800℃.

[0102] Example 8

[0103] On the basis of Example 1, the hydrated salt was replaced by magnesium nitrate hexahydrate and sodium sulfate decahydrate, the mass ratio of magnesium nitrate hexahydrate to sodium sulfate decahydrate was 1:1, and other conditions remained unchanged.

[0104] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 8 is 1170 kJ / kg, and the density is 1.45 g / cm 3 , the volume heat storage density is 1697 MJ / m 3 ; The thermal conductivity is 0.60 W / m·K at room temperature, and drops to 0.042 W / m·K after heating at 800 ℃.

[0105] Example 9

[0106] Based on Example 8, magnesium nitrate hexahydrate was omitted, the hydrated salt content remained unchanged, and other conditions remained unchanged.

[0107] The sum of the phase change energy storage and thermochemical energy storage densities of the hydrated salt thermochemical heat storage gel prepared in Example 9 is 1010 kJ / kg, and the density is 1.42 g / cm 3 , the volumetric heat storage density is 1434 MJ / m 3 ;The thermal conductivity is 0.55 W / m·K at room temperature, and drops to 0.05 W / m·K after heating at 800 ℃.

[0108] Example 10

[0109] Based on Example 8, sodium sulfate decahydrate was omitted, the hydrated salt content remained unchanged, and other conditions remained unchanged.

[0110] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 10 is 1295 kJ / kg, and the density is 1.47 g / cm 3 , the volumetric heat storage density is 1904 MJ / m 3 ; The thermal conductivity is 0.62 W / m·K at room temperature, and drops to 0.04 W / m·K after heating at 800 ℃.

[0111] It can be seen from Examples 8 to 10 that magnesium nitrate hexahydrate and sodium sulfate decahydrate can synergistically improve the volumetric heat storage density of the hydrated salt thermochemical heat storage gel.

[0112] Example 11

[0113] Based on Example 1, the monomer was replaced with sodium acrylate, and other conditions remained unchanged.

[0114] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 11 is 1320 kJ / kg, and the density is 1.50 g / cm 3 , the volume heat storage density is 1980 MJ / m 3 ; The thermal conductivity is 0.54 W / m·K at room temperature, and drops to 0.043 W / m·K after heating at 800 ℃.

[0115] Example 12

[0116] Based on Example 1, the monomer was replaced with acrylic acid, and other conditions remained unchanged.

[0117] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 12 is 1320 kJ / kg, and the density is 1.50 g / cm 3 , the volumetric heat storage density is 1980 MJ / m 3 ; The thermal conductivity is 0.53 W / m·K at room temperature, and drops to 0.042 W / m·K after heating at 800 ℃.

[0118] Example 13

[0119] On the basis of Example 1, the monomer was replaced with 2-acrylamido-2-methyl-1-propanesulfonic acid, and other conditions remained unchanged.

[0120] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 13 is 1335 kJ / kg, and the density is 1.51 g / cm 3 , the volumetric heat storage density is 2013 MJ / m 3 ; The thermal conductivity is 0.56 W / m·K at room temperature, and drops to 0.044 W / m·K after heating at 800 ℃.

[0121] Example 14

[0122] On the basis of Example 1, the monomer was replaced by acrylamide, and other conditions remained unchanged.

[0123] The sum of the phase change energy storage and thermochemical energy storage densities of the hydrated salt thermochemical heat storage gel prepared in Example 14 is 1310 kJ / kg, and the density is 1.49 g / cm 3 , the volume heat storage density is 1952 MJ / m 3 ; The thermal conductivity is 0.55 W / m·K at room temperature, and drops to 0.042 W / m·K after heating at 800 ℃.

[0124] Example 15

[0125] On the basis of Example 1, the monomers were replaced with sodium alginate and acrylamide, the mass ratio of sodium alginate to acrylamide was 1:1, and other conditions remained unchanged.

[0126] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 15 is 1305 kJ / kg, and the density is 1.48 g / cm 3 , the volume heat storage density is 1929 MJ / m 3 ; The thermal conductivity is 0.54 W / m·K at room temperature, and drops to 0.043 W / m·K after heating at 800 ℃.

[0127] Example 16

[0128] On the basis of Example 1, the monomers were replaced with acrylic acid and 2-acrylamido-2-methyl-1-propanesulfonic acid, the mass ratio of acrylic acid to 2-acrylamido-2-methyl-1-propanesulfonic acid was 1:1, and other conditions remained unchanged.

[0129] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 16 is 1340 kJ / kg, and the density is 1.52 g / cm 3 , the volume heat storage density is 2037 MJ / m 3 ; The thermal conductivity is 0.57 W / m·K at room temperature, and drops to 0.045 W / m·K after heating at 800 ℃.

[0130] Example 17

[0131] On the basis of Example 1, the monomers were replaced with acrylic acid and sodium acrylate, the mass ratio of acrylic acid to sodium acrylate was 1:1, and other conditions remained unchanged.

[0132] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 17 is 1325 kJ / kg, and the density is 1.51 g / cm 3 , the volumetric heat storage density is 1998 MJ / m 3; The thermal conductivity is 0.55 W / m·K at room temperature, and drops to 0.042 W / m·K after heating at 800 ℃.

[0133] Example 18

[0134] On the basis of Example 1, the initiator was replaced by α-ketoglutaric acid, and other conditions remained unchanged.

[0135] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 18 is 1350 kJ / kg, and the density is 1.50 g / cm 3 , the volume heat storage density is 2025 MJ / m 3 ; The thermal conductivity is 0.54 W / m·K at room temperature, and drops to 0.042 W / m·K after heating at 800 ℃.

[0136] Example 19

[0137] Based on Example 1, the initiator was replaced with α-ketoglutaric acid and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, the mass ratio of α-ketoglutaric acid to 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone was 1:1, and other conditions remained unchanged.

[0138] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 19 is 1385 kJ / kg, and the density is 1.52 g / cm 3 , the volume heat storage density is 2104 MJ / m 3 ; The thermal conductivity is 0.56 W / m·K at room temperature, and drops to 0.043 W / m·K after heating at 800 ℃.

[0139] It can be seen from Examples 1 and 18 to 19 that α-ketoglutaric acid and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone as initiators can synergistically improve the volumetric heat storage density of the hydrated salt thermochemical heat storage gel compared to one of them.

[0140] Example 20

[0141] A hydrated salt thermochemical heat storage gel is prepared from the following raw materials by weight: 60% hydrated salt, 28% monomer, 10% initiator and 2% cross-linking agent, with other conditions being the same as those in Example 1.

[0142] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 20 is 1395 kJ / kg, and the density is 1.55 g / cm 3 , the volume heat storage density is 2150 MJ / m 3;The thermal conductivity is 0.51 W / m·K at room temperature, and drops to 0.089 W / m·K after heating at 800 ℃.

[0143] Example 21

[0144] A hydrated salt thermochemical heat storage gel is prepared from the following raw materials by weight: 73% hydrated salt, 20% monomer, 5% initiator and 2% cross-linking agent, with other conditions being the same as those in Example 1.

[0145] The sum of the phase change energy storage and thermochemical energy storage density of the hydrated salt thermochemical heat storage gel prepared in Example 21 is 1512 kJ / kg, and the density is 1.55 g / cm 3 , the volumetric heat storage density is 2343 MJ / m 3 ; The thermal conductivity is 0.51 W / m·K at room temperature, and drops to 0.078 W / m·K after heating at 800 ℃.

[0146] It can be seen from the above embodiments and comparative examples that the hydrated salt thermochemical heat storage gel provided by the present invention has a high heat storage density, is carbonized at high temperature, and has a significantly reduced thermal conductivity, exhibiting a thermal conductivity switching characteristic, which can effectively reduce the risk of thermal runaway propagation in the battery module.

[0147] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density is prepared from raw materials including the following mass contents: 60-90% hydrated salt, 5-30% monomer, 0.1-10% cross-linking agent and 0.1-10% initiator.

2. The hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density according to claim 1, characterized in that: The invention is prepared from raw materials containing the following contents by weight: 65-85% of hydrated salt, 10-25% of monomer, 0.5-8% of cross-linking agent and 0.5-8% of initiator.

3. The hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density according to claim 1 or 2, characterized in that: The hydrated salt is at least one of disodium hydrogen phosphate dodecahydrate, magnesium sulfate heptahydrate, potassium aluminum sulfate dodecahydrate, oxalic acid dihydrate, sodium acetate trihydrate, magnesium chloride hexahydrate, strontium chloride hexahydrate, barium hydroxide octahydrate, ammonium aluminum sulfate dodecahydrate, magnesium nitrate hexahydrate and sodium sulfate decahydrate.

4. The hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density according to claim 1 or 2, characterized in that: The monomer is at least one of sodium alginate, calcium alginate, sodium acrylate, acrylic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid and acrylamide.

5. The hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density according to claim 1 or 2, characterized in that: The initiator is at least one of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, ammonium persulfate and α-ketoglutaric acid.

6. The hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density according to claim 1 or 2, characterized in that: The cross-linking agent is one or more of N,N-methylenebisacrylamide, 1,4-butylene glycol diacrylate, zinc sulfate and boric acid.

7. A method for preparing the hydrated salt thermochemical heat storage gel having thermal switching properties and high heat storage density according to any one of claims 1 to 6, comprising the following steps: The hydrated salt is melted, and then a monomer, an initiator and a cross-linking agent are added to carry out a polymerization reaction to obtain a hydrated salt thermochemical heat storage gel with thermal switching characteristics and high heat storage density.

8. The preparation method according to claim 7, characterized in that The melting temperature is 60-95°C.

9. The preparation method according to claim 7, characterized in that The polymerization reaction is carried out under illumination or heating and stirring conditions; the wavelength of the illumination is 365nm, the power of the illumination is 1-200W, and the illumination time is 0.5-15min; the temperature of the heating and stirring is 70-95°C, the heating and stirring rate is 300-600r / min, and the heating and stirring time is 0.1-1h.

10. Use of the hydrated salt thermochemical heat storage gel having thermal switching properties and high heat storage density according to claims 1 to 6, or the hydrated salt thermochemical heat storage gel having thermal switching properties and high heat storage density prepared by the preparation method according to any one of claims 7 to 9 in cylindrical batteries, soft-pack batteries, lithium-ion batteries, sodium-ion batteries or solid-state batteries.

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