A wide-temperature-range hydrogel for battery thermal management and a preparation method and application thereof

Abstract

The application relates to the technical field of battery thermal management, and discloses a wide-temperature-range hydrogel for battery thermal management and a preparation method and application thereof, the preparation method comprising the following steps: adding polyvinyl alcohol and gelatin into water, heating and stirring to dissolve; then adding sodium alginate and polyhydric alcohol, and continuing to stir; further adding polyacrylic acid, and continuing to stir; then adding a crosslinking agent, degassing after uniformly stirring, and pouring into a mold to form a hydrogel after heat preservation and standing; immersing the obtained hydrogel into an H2SO4 aqueous solution, vibrating until completely swollen, heating to a constant weight in an oven, and washing with deionized water until neutral. The application introduces strong hydration groups into the hydrogel to establish a strong connection structure between water molecules and the polymer network, firmly fixes the water molecules in the polymer network of the hydrogel, prevents the water molecules from escaping or freezing, and effectively maintains the flexibility of the hydrogel in a wider temperature range through hydrogen bond formation of a sacrificial network structure, so that the thermal management capability in a battery pack is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery thermal management, in particular to a wide-temperature-range hydrogel for battery thermal management and a preparation method and application thereof. BACKGROUND

[0002] Due to poor waterproof performance of power electronic devices such as battery packs, the thermal management thereof cannot be directly immersed in liquid water for cooling. At present, the heat is mainly dissipated by air cooling, cold plate liquid cooling / water cooling, and immersion liquid cooling. The heat transfer coefficient of air cooling is poor, and the cost of liquid cooling such as fluorinated liquid is high, which is difficult to meet the safety and low cost requirements in large-scale energy storage. The thermal conductivity of air at 25℃ is only 0.026 W m -1 K -1 , and the thermal conductivity of water is 0.61 W m -1 K -1 , which is more than 23 times that of air. In addition, the density (1000 kg m 3 ) and specific heat capacity (4.2 kJ kg -1 K -1 ) of water are higher, and the unit volume heat capacity is 4200 kJ m -3 . In summary, water cooling is still the most cost-effective way of battery pack thermal management in large-scale energy storage.

[0003] The hydrophilic polymer skeleton in the hydrogel can effectively solve the problem of encapsulation of cooling water, and has attracted wide interest in the thermal management of electronic devices in recent years. For example, a kind of ionic thermoelectric hydrogel and a preparation method and application thereof in photovoltaic cell thermal management are disclosed in patent CN111864298A. The hydrogel is composed of a large amount of water and a small amount of hydrophilic cross-linked polymer network structure, and has certain tensile property and flexibility. This flexibility depends on the movement of water molecules during stretching. However, when the temperature is too high to make the water evaporate or the temperature is too low to make the water molecules freeze, the network structure will lose the ability of elastic deformation, so that the hydrogel becomes hard and brittle, loses the close fit and contact with the matrix, and the air gap formed will significantly reduce the heat conduction in the energy storage battery pack and the heat dissipation to the outside. Therefore, locking water molecules in the hydrogel and improving the flowability of water in a wider temperature range will significantly improve the heat dissipation performance of the hydrogel in thermal management.

[0004] At present, the main way to improve the flowability of water molecules in the hydrogel is to partially replace water with other liquids, such as ionic liquids, inorganic salt aqueous solutions, and non-volatile organic compounds, to increase the phase transition temperature. However, in these systems, water molecules can still move freely, and there is a risk of freezing or evaporation, so the hydrogel may still become hard and brittle at extreme temperatures, lose close fit with the battery pack, and affect the thermal management effect. SUMMARY

[0005] The present application is to overcome the above-mentioned problems existing in the prior art of hydrogel used in battery thermal management, and provides a wide temperature range hydrogel for battery thermal management, a preparation method and application thereof, by introducing strong hydration groups into the hydrogel to establish a strong connection structure between water molecules and the polymer network, firmly fixing the water molecules in the polymer network of the hydrogel, preventing escape or freezing, and effectively maintaining the flexibility of the hydrogel in a wider temperature range through hydrogen bond formation, and improving the thermal management capability in the battery pack.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] In the first aspect, the present application provides a preparation method of a wide temperature range hydrogel for battery thermal management, comprising the following steps:

[0008] (1) Polyvinyl alcohol and gelatin are added to water and heated and stirred to dissolve, to obtain a polymer network matrix;

[0009] (2) Sodium alginate and polyol are added to the polymer network matrix, and continue to stir to form a strong hydration component;

[0010] (3) Polyacrylic acid is added to the strong hydration component, and continue to stir to form a hydrogen bond sacrificial network structure;

[0011] (4) Crosslinking agent is added to the hydrogen bond sacrificial network structure, and after uniform stirring, it is poured into a mold for degassing, and after heat preservation and standing, a hydrogel is formed;

[0012] (5) The obtained hydrogel is immersed in an H2SO4 aqueous solution, vibrated until completely swollen, heated to constant weight in an oven, and washed with deionized water until neutral, to obtain the wide temperature range hydrogel.

[0013] The present application uses polyvinyl alcohol and crosslinking agent as the network skeleton to support the overall structure of the hydrogel; the triple helix structure of gelatin forms a dynamic sacrificial network to dissipate stress at low temperature; sodium alginate and polyol form multiple hydrogen bonds with water to reduce water activity and inhibit ice nucleus formation; the carboxyl group in polyacrylic acid provides a negative charge to form a hydrogen bond network structure at low temperature, and the hydrogen bond network structure is dissociated to release water to buffer stress at high temperature; the aqueous sulfuric acid solution improves the water fixation capacity of the network structure, prevents evaporation or freezing, and expands the temperature adaptability in the battery thermal management scenario.

[0014] As a preferred, the mass ratio of the added polyvinyl alcohol, gelatin, sodium alginate, polyol, polyacrylic acid, crosslinking agent is 10-25:1-5:1-8:0.5-5:2-10:0.5-3.

[0015] Preferably, the mass concentration of polyvinyl alcohol in the polymer network matrix obtained in step (1) is 10-25%; the temperature during heating and stirring is 60-80℃, and the stirring time is 2-6h.

[0016] Preferably, the polyhydric alcohol in step (2) is one or more of ethylene glycol, glycerol, polyglycerol, polyethylene glycol, dipropylene glycol, pentaerythritol, sorbitol, and xylitol; the stirring temperature in step (2) is 60-80℃, and the stirring time is 0.5-3h.

[0017] Preferably, the stirring temperature in step (3) is 50-80℃, and the stirring time is 0.5-2h.

[0018] Preferably, the crosslinking agent in step (4) is one or more of genipin, vanillin, glutaraldehyde, paraformaldehyde, adiponitrile, carbodiimide, azidodiphenyl phosphine, ethylene glycol diglycidyl ether, and soluble salts of Fe 3+ , Ca 2+ , Al 3+ , Zn 2+ , and Cu 2+ .

[0019] Preferably, the temperature during heat preservation and standing in step (4) is 40-70℃, and the time is 2-8h.

[0020] Preferably, the mass concentration of the H2SO4 aqueous solution in step (5) is 5-40%, the vibration time is 24-72h, the vibration speed is 100-200rpm; the oven heating temperature is 50-70℃, and the heat preservation time is 12-60h.

[0021] In a second aspect, the present application provides a wide-temperature-range hydrogel prepared by the above preparation method.

[0022] In a third aspect, the present application provides an application of the above wide-temperature-range hydrogel in battery thermal management materials.

[0023] Therefore, the present application has the following beneficial effects:

[0024] (1) The phase transition temperature of the hydrogel is widened, making it more suitable for use as a battery thermal management material in a wide-temperature-range environment;

[0025] (2) Water molecules are fixed inside the network structure through the strong connection between the organic network and water, preventing escape or freezing, and improving the thermal management performance in a battery pack. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a phase transition temperature range diagram of the wide-temperature-range hydrogel prepared in the embodiments of the present application.

[0027] Figure 2 Figure 4 is a plot of thermal conductivity and heat capacity per volume of hydrogels prepared in the examples and comparative examples of the present application.

[0028] Figure 3 Figure 5 is a plot of maximum temperature in lithium battery of hydrogels prepared in the examples and comparative examples of the present application.

[0029] Figure 4 Figure 6 is a plot of maximum temperature difference in lithium battery of hydrogels prepared in the examples and comparative examples of the present application. DETAILED DESCRIPTION

[0030] The present application will be further described in conjunction with the accompanying drawings and specific embodiments.

[0031] In the present application, all the equipment and raw materials can be purchased from the market or commonly used in the industry, and the methods in the following examples are conventional methods in the field unless otherwise specified.

[0032] General examples:

[0033] A method for preparing a wide-temperature-range hydrogel for battery thermal management, comprising the following steps:

[0034] (1) polyvinyl alcohol and gelatin are added to water and heated and stirred to dissolve, to obtain a polymer network matrix;

[0035] (2) sodium alginate and polyhydric alcohol are added to the polymer network matrix, and continue to stir to form a strong hydration component;

[0036] (3) polyacrylic acid is added to the strong hydration component, and continue to stir to form a hydrogen bond sacrificial network structure;

[0037] (4) a crosslinking agent is added to the hydrogen bond sacrificial network structure, and after uniform stirring, it is poured into a mold for degassing, and after heat preservation and standing, a hydrogel is formed;

[0038] (5) the obtained hydrogel is immersed in an H2SO4 aqueous solution, vibrated until completely swollen, heated to constant weight in an oven, and washed with deionized water until neutral, to obtain the wide-temperature-range hydrogel.

[0039] As a specific embodiment, the mass ratio of the added polyvinyl alcohol, gelatin, sodium alginate, polyhydric alcohol, polyacrylic acid, and crosslinking agent is 10-25:1-5:1-8:0.5-5:2-10:0.5-3.

[0040] As a specific embodiment, in the polymer network matrix obtained in step (1), the mass concentration of polyvinyl alcohol is 10-25%; the temperature during heating and stirring is 60-80°C, and the stirring time is 2-6h.

[0041] As a specific embodiment, the polyhydric alcohol in step (2) is one or more of ethylene glycol, glycerol, polyglycerol, polyethylene glycol, dipropylene glycol, pentaerythritol, sorbitol, and xylitol; the stirring temperature in step (2) is 60-80°C, and the stirring time is 0.5-3h.

[0042] As a specific embodiment, the stirring temperature in step (3) is 50-80°C, and the stirring time is 0.5-2h.

[0043] As a specific embodiment, the crosslinking agent in step (4) is one or more of genipin, vanillin, glutaraldehyde, paraformaldehyde, adiponitrile, carbodiimide, azidodiphenyl phosphine, ethylene glycol diglycidyl ether, and soluble salts of Fe 3+ , Ca 2+ , Al 3+ , Zn 2+ , Cu 2+ .

[0044] As a specific embodiment, the temperature during the incubation and standing in step (4) is 40-70°C, and the time is 2-8h.

[0045] As a specific embodiment, the mass concentration of the aqueous H2SO4 solution in step (5) is 5-40%, the vibration time is 24-72h, the vibration speed is 100-200rpm; the oven heating temperature is 50-70°C, and the incubation time is 12-60h.

[0046] Example 1:

[0047] A method for preparing a wide-temperature-range hydrogel for battery thermal management, comprising the following steps:

[0048] Step 1: 15g of polyvinyl alcohol (PVA-1799) and 2g of gelatin were placed in 80mL of hot water, and then heated and stirred at 60°C for 5 hours;

[0049] Step 2: 4g of sodium alginate and 2g of glycerol were added to the mixture in step 1, and stirring was continued at 60°C for 2 hours;

[0050] Step 3: 5g of polyacrylic acid (Aladdin, Mw=2000) was added to the mixture in step 2, and stirring was continued at 60°C for 1 hour;

[0051] Step 4: 1g of genipin was added to the mixture in step 3, and after uniform stirring, the mixture was degassed and poured into a mold, and then incubated in an oven at 60°C for 2 hours to form a hydrogel;

[0052] Step 5: The hydrogel in step 4 was immersed in 20% mass fraction of H2SO4 aqueous solution, vibrated in a vibration table for 48 hours at a vibration speed of 120 rpm, and then kept in an oven at 60℃ for 24 hours after complete swelling. After the mass remained unchanged, the hydrogel was taken out, washed with deionized water until neutral, and the wide temperature range hydrogel was obtained.

[0053] As shown in Figure 1 , the differential scanning calorimetry test results show that the hydrogel prepared in Example 1 exhibits a single glass transition behavior at -97℃, and the lower phase transition temperature is due to the introduction of glycerol and sulfuric acid components in the system to inhibit nucleation at low temperature; an exothermic peak appears at 126℃, indicating that the evaporation of water molecules in the hydrogel is eliminated by the strong hydrogen bonding between the network structure and water molecules, ensuring that no phase transition occurs in the wide temperature range of -97℃ to 126℃.

[0054] As shown in Figure 2 , the thermal conductivity test shows that the thermal conductivity of the hydrogel prepared in Example 1 is 0.42 W m -1 K -1 , which is more than 16 times that of air, and the heat capacity per unit volume reaches 3617 kJ m -3 K -1 , which has good heat conduction characteristics.

[0055] As shown in Figure 3 and Figure 4 , the hydrogel prepared in the example is used for battery thermal management, and when the test environment temperature is 50℃, the maximum temperature difference of 18650 type lithium ion battery pack during 100 times of high rate continuous charging and discharging is less than 4.9℃, and the highest temperature is not more than 55℃, which reflects good temperature uniformity, and its thermal management ability is significantly better than that of the traditional air cooling method, which has a maximum temperature difference of 10.5℃ and a maximum temperature of more than 63℃ under the same test conditions, which is easy to cause thermal runaway chain reaction.

[0056] Example 2:

[0057] A preparation method of a wide temperature range hydrogel for battery thermal management, the steps are as follows:

[0058] Step 1: 15g of polyvinyl alcohol (PVA-1799) and 2g of gelatin were placed in 80mL of hot water, and then heated and stirred at 60℃ for 5 hours;

[0059] Step 2: 4g of sodium alginate and 3g of ethylene glycol were added to the mixture in step 1, and the stirring was continued at 60℃ for 2 hours;

[0060] Step 3: 5g of polyacrylic acid (Arla, Mw=2000) was added to the mixture in step 2, and the stirring was continued at 60℃ for 1 hour;

[0061] Step 4: 1 g of genipin was added into the mixture in step 3, and after stirring evenly, it was poured into a mold, degassed, and then incubated in an oven at 60℃ for 2 hours to form a hydrogel;

[0062] Step 5: The hydrogel in step 4 was immersed in a 20% mass fraction H2SO4 aqueous solution, vibrated in a vibration table at 120 rpm for 48 hours, and then incubated in an oven at 60℃ for 24 hours after complete swelling. After the mass remained unchanged, it was taken out, washed with deionized water until neutral, and the wide-temperature-range hydrogel was obtained.

[0063] As shown in Figure 1 , the differential scanning calorimetry test results show that the hydrogel prepared in Example 2 exhibits a single glass transition behavior at -93℃, and the lower phase transition temperature is due to the introduction of ethylene glycol and sulfuric acid components in the system to inhibit nucleation at low temperature; an exothermic peak appears at 122℃, indicating that the evaporation of water molecules in the hydrogel is eliminated by the strong hydrogen bonding between the network structure and water molecules, ensuring that no phase transition occurs within the wide temperature range of -93℃ to 122℃.

[0064] As shown in Figure 2 , the thermal conductivity performance test shows that the thermal conductivity of the hydrogel prepared in Example 2 is 0.40 W m -1 K -1 , which has good thermal conductivity characteristics.

[0065] As shown in Figure 3 and Figure 4 , the hydrogel prepared in Example 2 is used for battery thermal management, and when the test environment temperature is 50℃, it can make the maximum temperature difference of 18650 type lithium ion battery pack during high-rate continuous charging and discharging for 100 times less than 5.0℃, and the highest temperature does not exceed 55℃, which reflects good temperature uniformity.

[0066] Example 3:

[0067] A method for preparing a wide-temperature-range hydrogel for battery thermal management, the steps are as follows:

[0068] Step 1: 15 g of polyvinyl alcohol (PVA-1799) and 2 g of gelatin were placed in 80 mL of hot water, and then heated and stirred at 60℃ for 5 hours;

[0069] Step 2: 4 g of sodium alginate and 2 g of glycerol were added to the mixture in step 1, and stirring was continued at 60℃ for 2 hours;

[0070] Step 3: 5 g of polyacrylic acid (Arla, Mw=2000) was added to the mixture in step 2, and stirring was continued at 60℃ for 1 hour;

[0071] Step 4: Add 3g of glutaraldehyde aqueous solution (50% by mass) to the mixture in step 3, stir well, pour into a mold to degas, and then keep warm in a 60℃ oven for 2 hours to form a hydrogel;

[0072] Step 5: Immerse the hydrogel from Step 4 in a 20% (w / w) H2SO4 aqueous solution and vibrate it on a vibration table for 48 hours at a speed of 120 rpm until it is fully swollen. Then, keep it in a 60°C oven for 24 hours until the mass remains unchanged. Remove it and wash it with deionized water until it is neutral to obtain the wide temperature range hydrogel.

[0073] like Figure 1 As shown in the figure, the differential scanning calorimetry test results show that the hydrogel prepared in Example 3 exhibits a single glass transition behavior at -92℃; an exothermic peak appears at 120℃, indicating that the strong hydrogen bonding between the network structure and water molecules eliminates the evaporation of water molecules in the hydrogel, ensuring that no phase transition occurs in the wide temperature range of -92℃ to 120℃.

[0074] like Figure 2 As shown in the figure, the thermal conductivity test results indicate that the hydrogel prepared in Example 3 has a thermal conductivity of 0.39 W / m. -1 K -1 It has good thermal conductivity.

[0075] When the hydrogel prepared in Example 3 was used for battery pack thermal management, the maximum temperature difference of the 18650 lithium-ion battery pack was less than 5.0°C and the highest temperature did not exceed 56°C when the ambient temperature was 50°C during 100 consecutive charge-discharge cycles at high rates, demonstrating good temperature uniformity.

[0076] Example 4:

[0077] A method for preparing a wide-temperature-range hydrogel for battery thermal management, comprising the following steps:

[0078] Step 1: Place 15g of polyvinyl alcohol (PVA-1799) and 2g of gelatin in 80mL of hot water, then heat and stir continuously at 60℃ for 5 hours;

[0079] Step 2: Add 4g sodium alginate and 2g glycerol to the mixture from Step 1, and continue stirring at 60°C for 2 hours;

[0080] Step 3: Add 5g of polyacrylic acid (Aladdin, Mw=2000) to the mixture in Step 2, and continue stirring at 60°C for 1 hour;

[0081] Step 4: Add 1g of zinc acetate to the mixture in step 3, stir well, pour into a mold to degas, and then keep warm in a 60℃ oven for 2 hours to form a hydrogel;

[0082] Step 5: The hydrogel in step 4 was immersed in 20% mass fraction of H2SO4 aqueous solution, vibrated in a vibration table for 48 hours at a vibration speed of 120 rpm, and then kept in an oven at 60℃ for 24 hours after complete swelling. After the mass remained unchanged, the hydrogel was washed with deionized water until neutral to obtain the wide temperature range hydrogel.

[0083] As shown in FIG. 4, the differential scanning calorimetry test results show that the hydrogel prepared in Example 4 exhibits a single glass transition behavior at -89℃; an exothermic peak appears at 118℃, indicating that the evaporation of water molecules in the hydrogel is eliminated by the strong hydrogen bonding between the network structure and water molecules, ensuring that no phase transition occurs in the wide temperature range of -89℃ to 118℃. Figure 1 As shown in FIG. 5, the thermal conductivity test shows that the thermal conductivity of the hydrogel prepared in Example 4 is 0.39 W m -1 K -1 , which has good thermal conductivity characteristics.

[0084] Figure 2 The hydrogel prepared in Example 4 was used for battery thermal management, and when the test environment temperature was 50℃, the maximum temperature difference of a 18650 type lithium ion battery was less than 5.0℃ during 100 times of high-rate continuous charge and discharge, and the highest temperature was not more than 56℃, which embodied good temperature uniformity.

[0085] Example 5:

[0086] A preparation method of a wide temperature range hydrogel for battery thermal management, comprising the following steps:

[0087] Step 1: 15 g of polyvinyl alcohol (PVA-1799) and 2 g of gelatin were placed in 80 mL of hot water, and then heated and stirred at 60℃ for 5 hours;

[0088] Step 2: 4 g of sodium alginate and 2 g of glycerol were added to the mixture in step 1, and the stirring was continued at 60℃ for 2 hours;

[0089] Step 3: 5 g of polyacrylic acid (Arla, Mw=2000) was added to the mixture in step 2, and the stirring was continued at 60℃ for 1 hour;

[0090] Step 4: 1 g of genipin was added to the mixture in step 3, and after uniform stirring, the mixture was degassed and then kept in an oven at 60℃ for 2 hours to form a hydrogel;

[0091] Step 4: 1 g of genipin was added to the mixture in step 3, and after uniform stirring, the mixture was degassed and then kept in an oven at 60℃ for 2 hours to form a hydrogel;

[0092] ​Step 5: Immerse the hydrogel from Step 4 in a 40% (w / w) H2SO4 aqueous solution and vibrate it on a vibration table for 48 hours at a speed of 120 rpm until it is fully swollen. Then, keep it in a 60°C oven for 24 hours until the mass remains unchanged. Remove it and wash it with deionized water until it is neutral to obtain the wide temperature range hydrogel.

[0093] like Figure 1 As shown in the figure, the differential scanning calorimetry test results show that the hydrogel prepared in Example 5 exhibits a single glass transition behavior at -95℃; an exothermic peak appears at 123℃, indicating that the strong hydrogen bonding between the network structure and water molecules eliminates the evaporation of water molecules in the hydrogel, ensuring that no phase transition occurs in the wide temperature range of -95℃ to 123℃.

[0094] like Figure 2 As shown in the figure, the thermal conductivity test results indicate that the hydrogel prepared in Example 5 has a thermal conductivity of 0.42 W / m. -1 K -1 It has good thermal conductivity.

[0095] The hydrogel prepared in Example 5 was used for battery pack thermal management. When the ambient temperature was 50°C, the maximum temperature difference of the 18650 lithium-ion battery pack was less than 4.8°C and the maximum temperature did not exceed 55°C during 100 consecutive charge-discharge cycles at high rates, demonstrating good temperature uniformity.

[0096] Comparative Example 1 (without sodium alginate):

[0097] A method for preparing a hydrogel for battery thermal management, comprising the following steps:

[0098] Step 1: Place 15g of polyvinyl alcohol (PVA-1799) and 2g of gelatin in 80mL of hot water, then heat and stir continuously at 60℃ for 5 hours;

[0099] Step 2: Add 2g of glycerin to the mixture from Step 1 and continue stirring at 60°C for 2 hours;

[0100] Step 3: Add 5g of polyacrylic acid (Aladdin, Mw=2000) to the mixture in Step 2, and continue stirring at 60°C for 1 hour;

[0101] Step 4: Add 1g of genipin to the mixture in step 3, stir well, pour into a mold to degas, and then keep warm in a 60℃ oven for 2 hours to form a hydrogel;

[0102] Step 5: The hydrogel in step 4 is immersed in a 20% mass fraction H2SO4 aqueous solution, vibrated in a vibration table for 48 hours at a vibration speed of 120 rpm, and after complete swelling, is kept in an oven at 60°C for 24 hours. After the mass remains unchanged, it is taken out and washed with deionized water until neutral.

[0103] The differential scanning calorimetry test results show that the hydrogel prepared in Comparative Example 1 exhibits phase change behavior below -23°C and mass loss at an environmental temperature above 100°C, and cannot long-term maintain the locking of water molecules in a wide temperature range. The thermal conductivity performance test shows that the thermal conductivity of the hydrogel prepared in Comparative Example 1 is 0.39 W m -1 K -1 .

[0104] The hydrogel prepared in Comparative Example 1 is used for battery thermal management. When the test environmental temperature is 50°C, water evaporates slowly and cannot long-term maintain the battery temperature in a lower range, so that the maximum temperature difference of the 18650 type lithium ion battery is greater than 7.3°C during high-rate continuous charging and discharging, and the maximum temperature exceeds 61°C. Its thermal management ability is significantly lower than that of Example 1, and is easy to cause thermal runaway chain reaction.

[0105] Comparing Example 1 and Comparative Example 1 shows that the introduction of sodium alginate is a prerequisite for forming a strong hydration structure and maintaining wide temperature range thermal management performance.

[0106] Comparative Example 2 (without adding polyacrylic acid):

[0107] A method for preparing a hydrogel for battery thermal management, the steps are as follows:

[0108] Step 1: 15 g of polyvinyl alcohol (PVA-1799) and 2 g of gelatin are placed in 80 mL of hot water, and then heated and stirred at 60°C for 5 hours;

[0109] Step 2: 4 g of sodium alginate and 2 g of glycerol are added to the mixture in step 1, and stirring is continued at 60°C for 2 hours;

[0110] Step 3: 1 g of genipin is added to the mixture in step 3, and after stirring evenly, it is poured into a mold for degassing, and then kept in an oven at 60°C for 2 hours to form a hydrogel;

[0111] Step 4: The hydrogel in step 4 is immersed in a 20% mass fraction H2SO4 aqueous solution, vibrated in a vibration table for 48 hours at a vibration speed of 120 rpm, and after complete swelling, is kept in an oven at 60°C for 24 hours. After the mass remains unchanged, it is taken out and washed with deionized water until neutral.

[0112] The hydrogel prepared in Comparative Example 2 loses flexibility below -30°C, cannot long-term maintain close adhesion with the battery pack in a wide temperature range, affects the heat management effect, and results in poor heat management effect.

[0113] When the hydrogel prepared in Comparative Example 2 is used for battery pack heat management, the maximum temperature difference of the battery pack is greater than 6.7°C at a test environment temperature of 50°C, and the maximum temperature exceeds 58°C, which is significantly lower than the heat management capability of Example 1.

[0114] Comparing Example 1 and Comparative Example 2 shows that the introduction of polyacrylic acid is a prerequisite for forming a sacrificial network structure, maintaining flexibility in a wide temperature range, and improving adhesion capability in the heat management process under extreme conditions.

[0115] Comparative Example 3 (without adding sulfuric acid):

[0116] A method for preparing a hydrogel for battery heat management, the steps are as follows:

[0117] Step 1: Put 15 g of polyvinyl alcohol (PVA-1799) and 2 g of gelatin into 80 mL of hot water, then continuously heat and stir at 60°C for 5 hours;

[0118] Step 2: Add 4 g of sodium alginate and 2 g of glycerol to the mixture in Step 1, and continue to stir at 60°C for 2 hours;

[0119] Step 3: Add 5 g of polyacrylic acid (Araldine, Mw=2000) to the mixture in Step 2, and continue to stir at 60°C for 1 hour;

[0120] Step 4: Add 1 g of genipin to the mixture in Step 3, stir uniformly, then pour into a mold to degas, and then incubate in a 60°C oven for 2 hours to form a hydrogel;

[0121] Step 5: Soak the hydrogel in Step 4 in a 60°C oven for 24 hours, then wash with deionized water until neutral.

[0122] The hydrogel prepared in Comparative Example 3 has a high water loss rate at the step 5 stage, and cannot be used as a heat management material. It loses flexibility below -30°C, cannot long-term maintain close adhesion with the battery pack in a wide temperature range, affects the heat management effect, and results in poor heat management effect.

[0123] When the hydrogel prepared in Comparative Example 3 is used for battery pack heat management, the maximum temperature difference of the battery pack is greater than 6.7°C at a test environment temperature of 50°C, and the maximum temperature exceeds 58°C, which is significantly lower than the heat management capability of Example 1.

[0124] Comparing Example 1 and Comparative Example 3 shows that the introduction of the sulfuric acid component is a key to forming a strong hydration structure, improving water locking capability, and maintaining heat management performance in a wide temperature range.

[0125] The above-described embodiments are only preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and all should be considered within the scope of protection of the present application.

Claims

1. A method for preparing a wide temperature range hydrogel for battery thermal management, characterized by the steps of The preparation method comprises the following steps: (1) dissolving polyvinyl alcohol and gelatin in water by heating and stirring to obtain a polymer network matrix; (2) adding sodium alginate and a polyhydric alcohol into the polymer network matrix and continuously stirring to form a strong hydration component; the polyhydric alcohol is one or more of ethylene glycol, glycerol, polyglycerol, polyethylene glycol, dipropylene glycol, pentaerythritol, sorbitol and xylitol; (3) adding polyacrylic acid into the strong hydration component and continuously stirring to form a hydrogen-bond-sacrificable network structure; (4) A crosslinking agent is added to the hydrogen-bonded sacrificial network structure, stirred evenly, poured into a mold for degassing, and kept at a constant temperature to form a hydrogel; the mass ratio of added polyvinyl alcohol, gelatin, sodium alginate, polyol, polyacrylic acid, and crosslinking agent is 10~25:1~5:1~8:0.5~5:2~10:0.5~3; the crosslinking agents are genipin, vanillin, glutaraldehyde, paraformaldehyde, hexamethylene dicyanate, carbodiimide, ethylene glycol diglycidyl ether, and Fe. 3+ Ca 2+ Al 3+ Zn 2+ Cu 2+ One or more of the soluble salts; (5) immersing the obtained hydrogel into a 5-40% H2SO4 aqueous solution, vibrating at a speed of 100-200 rpm for 24-72 hours until the hydrogel is completely swelled, heating the hydrogel to a constant weight in an oven at 50-70 DEG C, and washing the hydrogel with deionized water until the hydrogel is neutral to obtain a wide-temperature-range hydrogel.

2. The method of claim 1, wherein the method further comprises, In the polymer network matrix obtained in step (1), the mass concentration of polyvinyl alcohol is 10-25%; the temperature for heating and stirring is 60-80 DEG C, and the stirring time is 2-6 hours.

3. The method of claim 1, wherein the method further comprises, In step (2), the stirring temperature is 60-80 DEG C, and the stirring time is 0.5-3 hours.

4. The method of claim 1, wherein the method further comprises, In step (3), the stirring temperature is 50-80 DEG C, and the stirring time is 0.5-2 hours.

5. The method of claim 1, wherein the method further comprises, In step (4), the temperature for heat preservation and standing is 40-70 DEG C, and the time is 2-8 hours.

6. The method of claim 1, wherein the hydrogel is prepared by the steps of: In step (5), the heat preservation time in the oven is 12-60 hours.

7. A wide temperature range hydrogel for battery thermal management, characterized in that, The wide-temperature-range hydrogel is prepared by the preparation method as claimed in any one of claims 1-6.

8. Use of a wide temperature range hydrogel for battery thermal management according to claim 7, characterized in that, The wide-temperature-range hydrogel is used as a battery thermal management material.

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