Phase change composite material for thermal runaway and preparation method thereof

Abstract

The invention discloses a phase change composite material for thermal runaway. The phase change composite material comprises the following components: fibers, fumed silica, deionized water, absolute ethyl alcohol, hydrated salt and a polymer skeleton. The phase change material disclosed by the invention has flame retardant property, can absorb a large amount of heat and release non-combustible gas in a solid-liquid-gas multi-stage phase change manner, and the residual base material can achieve a heat insulation effect, so that the phase change material has various flame-retardant and heat-insulation effects. And heat spreading during thermal runaway of the battery cells can be effectively blocked when the battery cells are arranged between the battery cells.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of phase change composites, in particular to a phase change composite for thermal runaway and a preparation method thereof. BACKGROUND

[0002] With the development of new energy industry, lithium ion batteries are increasingly widely used. As the passive safety technology requirements of lithium batteries are improved, more and more manufacturers use aerogel materials with excellent thermal insulation performance. In the prior art, thermal insulation materials such as silica gel foam, aerogel materials and nano-porous materials are usually arranged between the battery cells to block the heat spread of the thermal runaway battery cells to the adjacent battery cells. However, this method does not completely solve the thermal runaway of the battery cells, but only delays the spread of the thermal runaway. Although the heat generated by the thermal runaway of the battery cells is blocked and delayed, it will not disappear, and there is still a risk of delayed thermal runaway, which does not meet the safety requirements of the entire battery pack not catching fire or exploding. The risk of delayed thermal runaway may cause secondary accidents during rescue or after rescue, resulting in further safety threats.

[0003] Therefore, there is still a need for a phase change composite for thermal runaway and a preparation method thereof to solve the above problems. SUMMARY

[0004] The present application provides a phase change composite for thermal runaway and a preparation method thereof to solve the above problems.

[0005] The object of the present application is achieved by the following technical solutions: A phase change composite for thermal runaway, comprising the following components: fibers, fumed silica, deionized water, anhydrous ethanol, hydrated salt and a polymer skeleton.

[0006] Preferably, the components include, by weight fraction: 5-10 parts of fibers, 0.1-2 parts of fumed silica, 5-30 parts of deionized water, 5-30 parts of anhydrous ethanol, 70-90 parts of hydrated salt, 1-5 parts of a polymer skeleton, and 0.1-5 parts of a thermal conductive filler.

[0007] Preferably, the fibers are one or more of ceramic fibers, glass fibers and high-silica fibers.

[0008] Preferably, the ceramic fibers are composed of aluminum silicate, magnesium silicate, aluminum oxide, zirconium oxide or silicon carbide.

[0009] Preferably, the hydrated salt is one or more of barium hydroxide octahydrate, aluminum chloride hexahydrate, sodium acetate trihydrate, trisodium phosphate dodecahydrate, magnesium sulfate heptahydrate and aluminum nitrate nonahydrate.

[0010] Preferably, the heat-conductive filler is one or more of hexagonal boron nitride or nano-alumina, with a median particle size of 1-10 microns.

[0011] The second aspect discloses a preparation method of a thermal runaway composite phase change composite material, comprising: Deionized water is added to the hydrated salt, and the mixture is heated to a molten mixture I; The polymer skeleton is added to the molten mixture I, and a mixture II is formed by high-speed dispersion; The heat-conductive filler is added to the mixture II, and the mixture III is formed by continuous dispersion; The solution of the mixture III is injected into a heated impregnation tank, and the fibers are immersed below the solution surface, vacuum is drawn, vacuum impregnation is carried out, and a mixture IV is formed; The impregnated mixture IV is pressed by a hot roller, then placed in a cooling tank, and an isolation net is laid between each layer, the temperature is cooled to 0-30℃ to complete crystallization, and a laminated material is formed; The fumed silica solution is poured into the cooled laminated material after being dissolved in ethanol; Excess ethanol is removed by reduced pressure evaporation, and a low temperature is maintained during the reduced pressure evaporation.

[0012] Preferably, after the reduced pressure evaporation, the method further comprises: In dry air, the isolation net is removed, and the sheets are removed layer by layer; The sheets are placed in a pressure machine for thickness correction to obtain finished products.

[0013] Preferably, after obtaining the finished products, the method further comprises the step of: The bottom and top of the finished products are respectively coated with film, and the film is sealed by a heat sealer.

[0014] Compared with the prior art, the beneficial effects of the present application at least include: The phase change material of the present application has flame retardant properties, can absorb a large amount of heat through solid-liquid-gas multi-stage phase change, release non-combustible gas, and the residual substrate can play a heat insulation effect, having various flame-retardant and heat-insulating effects. The setting between the battery cells can effectively block the heat spread when the battery cells are in thermal runaway. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a physical diagram of the phase change composite material embodiment 1 of the present application embodiment; Figure 2 is a physical diagram of the phase change composite material embodiment 1 of the present application embodiment in a muffle furnace; Figure 3 is a physical diagram of the phase change composite material embodiment 1 of the present application embodiment after testing in a muffle furnace; Figure 4is a real object back view graph of the phase change composite embodiment 1 fire test test of the embodiment of the present application; Figure 5 is a real object front view graph of the phase change composite embodiment 1 fire test test after the embodiment of the present application; Figure 6 is a real object back view graph of the phase change composite embodiment 1 fire test test after the embodiment of the present application; Figure 7 is a heat absorption and phase change temperature test graph of the phase change composite embodiment 1 of the embodiment of the present application. DETAILED DESCRIPTION

[0016] Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments, however, can be implemented in many different forms and should not be construed as limited to the implementations set forth herein; rather, these implementations are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept of example embodiments to those skilled in the art. Like reference numerals refer to like elements throughout the several views of the drawings, and description thereof will be omitted.

[0017] The expressions of position and direction described in the present application are described with the drawings as examples, but changes can be made as needed, and the changes made are included in the scope of protection of the present application.

[0018] The present application provides a phase change composite material for thermal runaway, comprising the following components: Fiber, fumed silica, deionized water, anhydrous ethanol, hydrated salt and polymer skeleton. The main body of the material is composed of hydrated salt and fiber material, which is different from the traditional phase change concept. Instead of using only the reversible phase change heat absorption of the material, the product is designed to use the dual action of the heat absorption of the decomposition phase change of the hydrated salt and the heat absorption of the vaporization of the free water released, to maximize the heat absorption effect, and the substrate after phase change can act as a heat barrier without blocking the spread of heat, without pursuing complete reversible phase change. The test shows that it can maximize the reduction of heat transfer between the battery cells, and has the physical property of flexibility. The polymer skeleton is water-soluble polyvinyl alcohol.

[0019] Preferably, by weight fraction, it comprises: Fiber 5-10 parts, fumed silica 0.1-2 parts, deionized water 5-30 parts, anhydrous ethanol 5-30 parts, hydrated salt 70-90 parts, polymer skeleton 1-5 parts, and thermal conductive filler 0.1-5 parts. The test shows that the phase change composite material made with such a ratio has good heat insulation and heat absorption performance, and the remaining substrate after phase change can effectively block the burning of high temperature such as flame, effectively avoiding the burning of flame. The thermal conductive filler is selected from Preferably, the fiber is one or more of ceramic fiber, glass fiber, high silica fiber. In the form of chopped fiber mat. The selection of ceramic fiber, glass fiber, high silica fiber can significantly improve the overall thermal conductivity of the composite material, and accelerate the heat charging and discharging rate.

[0020] Preferably, the ceramic fiber is composed of aluminum silicate, or magnesium silicate, or alumina, or zirconia, or silicon carbide.

[0021] Preferably, the hydrated salt is one or more of barium hydroxide octahydrate, aluminum chloride hexahydrate, sodium acetate trihydrate, trisodium phosphate dodecahydrate, magnesium sulfate heptahydrate, aluminum nitrate nonahydrate.

[0022] Preferably, the thermal conductive filler is one or more of hexagonal boron nitride or nano-alumina, and the median particle size is 1-10 microns.

[0023] The second aspect of the present application discloses a preparation method of a thermal runaway composite phase change composite material, comprising: The deionized water is added to the hydrated salt, and the mixture is heated to a molten state of the mixture one. The water is added to the hydrated salt, and is melted into a molten fluid state at high temperature.

[0024] The polymer skeleton is added to the molten state of the mixture one, and is dispersed by high speed to form a mixture two.

[0025] The thermal conductive filler is added to the mixture two, and is continuously dispersed to form a mixture three. The thermal conductive filler is added to the molten state of the mixture two, and is mixed into the mixture three by rotating the high-speed dispersion equipment.

[0026] The solution of the mixture three is injected into a heated impregnation tank, and the fiber is immersed below the solution surface. Vacuum impregnation is carried out to form a mixture four. The fiber is injected into the solution and placed in a vacuum extraction device to form a mixture four.

[0027] The impregnated mixture four is pressed by a hot roller, and then is placed in a cooling tank. An isolation net is laid between each layer, and the temperature is cooled to 0-30℃ to complete crystallization and form a laminated material.

[0028] The fumed silica solution is filled into the cooled laminated material after being dissolved in ethanol. The excess ethanol is removed by reduced pressure evaporation, and the low temperature is maintained during the reduced pressure evaporation.

[0029] Preferably, after obtaining the finished product, the method further comprises the steps of: The bottom and top of the finished product are respectively covered with film, and the film is sealed by a heat sealing machine. When the finished product is installed between the battery cells, the edges of the finished product around the package can also be sealed by selecting a PET heat sealing film. When the packaged finished product is placed between the battery cells and one of the battery cells experiences thermal runaway, heat is generated rapidly, at which time the finished product in the heat sealing film undergoes a phase change, and the mixed hydrated salt changes from a solid to a liquid, absorbing part of the heat, and then from a liquid to a gas absorbing part of the heat, and after the heat sealing film expands in volume, the gas and the ejected flammable gas generated by the battery cell are mixed, and the heat sealing film also has an explosion-proof effect. The remaining decomposed finished product still maintains the basic shape and physical state, effectively blocking the flame on one side from impacting the battery cell in the safe state on the other side.

[0030] The phase change composite material of the present application can not only effectively block the transfer and spread of heat energy during the generation and transfer stages of the heat source, but also greatly reduce the probability of explosion of heat and flammable gas.

[0031] Example 1 Take 2 parts of deionized water and add to 80 parts of hydrated salt, and heat the mixture to a molten state, add 1 part of a high molecular skeleton to the molten material, and disperse uniformly using a high-speed disperser at a speed of 400-2000 r / min, add 0.3 parts of a heat-conducting filler, and continue to disperse uniformly, inject a sufficient amount of mixed solution into a heated impregnation tank, immerse 2 mm thick fibers below the liquid surface of the solution, vacuumize to -90 KPa, and perform vacuum impregnation for 15 min, press the impregnated fibers through a 1.8 mm gap hot roller, and then place them in a cooling tank, lay a 0.5 mm thick separation net between each layer, cool the temperature to 20°C to complete crystallization, dissolve 0.3 parts of fumed silica in 10 parts of ethanol, and pour the cooled layered material, -80 KPa reduced pressure evaporation for 3 h to remove excess ethanol, and maintain a low temperature state during the process, remove the separation net, and take out the sheet material layer by layer, maintain a dry environment during the process, place the sheet material in a pressure machine, use a 2 mm mold for thickness correction, and the finished product material can be obtained.

[0032] Example 2 Remove 2 parts of deionized water into 80 parts of hydrated salt, and heat the mixture to a molten state, add 1 part of the high molecular backbone to the molten material, use a high-speed disperser to disperse evenly, speed 400-2000r / min, add 0.3 parts of thermal conductive filler, and continue to disperse evenly, inject a sufficient amount of mixed solution into a heated impregnation tank, submerge 3mm thick fibers below the solution surface, vacuumize to -90KPa, and vacuum impregnate for 20min, press the impregnated fibers through a 2.7mm gap hot roller, and then place them in a cooling tank, lay a 0.5mm thick isolation net between each layer, cool the temperature to 10℃ to complete crystallization, dissolve 0.3 parts of fumed silica in 10 parts of ethanol, and fill the cooled stacked material, evaporate excess ethanol under reduced pressure of -80KPa for 3h, and maintain a low temperature state during the process, remove the isolation net, and take out the sheet material layer by layer, maintain a dry environment during the process, place the sheet material in a pressure machine, use a 3mm mold for thickness correction, and the finished product material is obtained.

[0033] Referring to Figure 1 , specifications: 100*100*2.0mm and 100*100*3mm.

[0034] 1. Thermal conductivity test According to GB / T10295-2008 Determination of Steady-state Thermal Resistance and Related Properties of Thermal Insulation Materials Hot-wire Method.

[0035] Referring to Figure 1 The results of testing Example 1 are that the thermal conductivity of the ceramic paper at room temperature is 0.038W / mk.

[0036] 2. Maximum temperature heat resistance test Referring to Figures 2-3 Put Example 1 into a 1000 degree Celsius muffle furnace and bake for 60min, and the result is that the appearance of Example 1 is complete without melting after testing.

[0037] 3. Fire test Referring to Figures 4-6 Burn Example 1 with a butane flame torch at 1200 degrees Celsius for 10min, with an interval of 30min, and cycle 6 times, and the result is that Example 1 has no flame penetration.

[0038] 4. Pressure test Pre-tighten Example 1 and Example 2 to 0.01MPa on a servo universal testing machine, load at a speed of 2mm / min, and load to 2MPa, and the result is that the appearance of Example 1 is complete without leakage.

[0039] 5. Heat absorption and phase change temperature test The differential scanning calorimeter is used to increase the temperature of the example 1 from room temperature to 200 degrees Celsius at a rate of 2 degrees Celsius per minute. As the temperature increases over time, the solid-liquid phase transition occurs at 142 degrees Celsius, and the liquid-gas phase transition occurs at 170.37 degrees Celsius. A large amount of heat is absorbed during the phase transition, and the area of the upward-opening V-shaped opening enclosed by the time axis and the green curve is the amount of heat absorbed. It can be seen that the phase change composite material has high heat absorption capacity and can effectively prevent the spread of heat.

[0040] The example 2 is tested in the above manner, and the test results show that: 1. Thermal conductivity test: The thermal conductivity of the ceramic paper of example 2 at room temperature is 0.038 W / mk. 2. Maximum temperature heat resistance test: The appearance structure of example 2 is complete, and there is no melting 3. Fire test: The result of example 2 has no flame penetration 4. Pressure test: The appearance structure of example 2 is complete and there is no leakage 5. Heat absorption and phase change temperature test: The results are the same as those of example 1.

[0041] Through the test, the phase change composite material connected between adjacent battery cells has good compression performance, and when the temperature of the battery cell is too high, the phase change composite material undergoes solid-liquid and liquid-gas transitions in turn to absorb a large amount of heat. In addition, when the battery cell sprays a flame, the gas phase in the phase change composite material will overflow and diffuse into the sprayed high-temperature flame, dilute the high-temperature flame, and reduce the risk of explosion.

[0042] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those skilled in the art can make changes, modifications, replacements and variations to the above embodiments without departing from the principles and purposes of the present application within the scope of the present application. All these changes should be within the protection scope of the claims of the present application.

Claims

1. A phase change composite material for thermal runaway, characterized by, The composition comprises the following components: fibers, fumed silica, deionized water, anhydrous ethanol, hydrated salt, and a high molecular skeleton.

2. The phase change composite for thermal runaway according to claim 1, characterized by, The composition comprises the following components by weight: fibers 5-10 parts, fumed silica 0.1-2 parts, deionized water 5-30 parts, anhydrous ethanol 5-30 parts, hydrated salt 70-90 parts, high molecular skeleton 1-5 parts, and heat-conducting filler 0.1-5 parts.

3. The phase change composite for thermal runaway according to claim 2, characterized by, The fibers are one or more of ceramic fibers, glass fibers, and high-silica fibers.

4. The phase change composite for thermal runaway according to claim 3, characterized by, The ceramic fibers are composed of aluminum silicate, magnesium silicate, aluminum oxide, zirconium oxide, or silicon carbide.

5. The phase change composite for thermal runaway according to claim 2, wherein The hydrated salt is one or more of barium hydroxide octahydrate, aluminum chloride hexahydrate, sodium acetate trihydrate, trisodium phosphate dodecahydrate, magnesium sulfate heptahydrate, and aluminum nitrate nonahydrate.

6. The phase change composite for thermal runaway according to claim 2, wherein The heat-conducting filler is one or more of hexagonal boron nitride or nano-aluminum oxide, with a median particle size of 1-10 microns.

7. A method of preparing a composite phase change composite for thermal runaway, characterized by, The method comprises the following steps: adding deionized water to the hydrated salt and heating the mixture to a molten state to form mixture one; adding the high molecular skeleton to the molten mixture one and dispersing at high speed to form mixture two; adding the heat-conducting filler to mixture two and continuing to disperse to form mixture three; injecting the solution of mixture three into a heated impregnation tank and submerging the fibers below the solution surface, vacuumizing, and vacuum impregnating to form mixture four; passing the impregnated mixture four through a hot roller, then placing it in a cooling tank, laying a separation net between each layer, cooling the temperature to 0-30°C to complete crystallization, and forming a laminated material; injecting the fumed silica solution into the cooled laminated material after dissolving it in ethanol; removing excess ethanol by reduced pressure evaporation while maintaining a low temperature during reduced pressure evaporation.

8. The preparation method according to claim 7, characterized in that, After reduced pressure evaporation, the method further comprises the following steps: removing the separation net and removing the sheets layer by layer in dry air; placing the sheets into a pressure machine for thickness correction to obtain the finished product.

9. The production method according to claim 8, characterized by, After obtaining the finished product, the method further comprises the following steps: coating the bottom and top of the finished product with film, respectively, and sealing the edges of the film with a heat sealer.

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