Hydrated salt composite phase change film, preparation method thereof and application of hydrated salt composite phase change film in thermal management of electronic device

Abstract

The invention discloses a hydrated salt composite phase change film, a preparation method thereof and application of the hydrated salt composite phase change film in thermal management of electronic devices. A hydrated salt composite phase change material (CPCM) is prepared from sodium acetate trihydrate (SAT) / porous expanded graphite (EG) through a vacuum impregnation method. Then, casting a wet film containing polyvinylidene fluoride (PVDF) and N-N dimethylformamide (DMF) in a certain proportion through a scraper and a roller press; the hydrated salt composite phase change film is obtained by immersing a wet film into a deionized water bath and dissolving the wet film with a solvent, the hydrated salt composite phase change film evacuates heat of an electronic device through hydrated salt phase change heat absorption and expanded graphite heat conduction, and the hydrated salt composite phase change film has temperature response flexibility in the phase change process, interface thermal resistance is reduced, and heat dissipation efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of phase change energy storage materials, in particular to a hydrated salt composite phase change film, a preparation method thereof and application thereof in electronic device thermal management. BACKGROUND

[0002] The update of electronic devices promotes the development of high integration, high energy density and high instantaneous charge / discharge capacity. The problem of transient high-intensity heat dissipation makes the thermal management of electronic devices crucial. Generally, air cooling and liquid cooling prevent further increase of working temperature at the cost of weight and high price. However, it is difficult to meet the requirements of high system integration and high energy density. Phase change material is a practical passive thermal management material, which adjusts its phase change behavior by environmental temperature change, so as to realize transient heat absorption in isothermal phase change process. The thermal management based on phase change material has the advantages of simple structure, no need of additional energy equipment and good cooling effect. However, the currently used phase change material is mainly organic phase change material, which has poor flame retardancy and low heat release rate. In addition, the preparation method of the phase change material for thermal management at present is complex, and the cost of ingredients used is high. Therefore, it is necessary to develop a phase change thermal management material with suitable phase change temperature, excellent heat absorption capacity, simple preparation method, low cost and stable working performance.

[0003] The scene used for the thermal management of electronic devices: for example, lithium ion battery is the main power source of electric vehicles. When the battery temperature is overheated due to high-speed charging / discharging, harsh environmental temperature and accidental increase of discharge current and voltage, safety problems such as battery structure damage and explosion may occur. In addition, electronic chips with high density integration characteristics are prone to instant temperature rise under the conditions of full load use, excessive overclocking and radiator failure, resulting in low running speed, chip damage and even threat to personal safety. Therefore, the timely dissipation of transient high-intensity heat flux is of great significance to realize stable, effective and safe output of electronic devices.

[0004] Some examples of thermal management of electronic devices using phase change materials (the preparation synthesis methods are relatively complex): Ye et al. designed a composite phase change material with a double phase change temperature zone by constructing a phase change polymer framework in situ in a polyethylene glycol (PEG) / expanded graphite (EG) mixture, which reduced the temperature of a battery model by 4.8℃ at a 1C discharge rate. Waseem Aftab et al. prepared a composite solid-liquid phase change material (PEG) with a particle-based conductive matrix, followed by surface reaction to form a solid-solid phase change shell, which significantly improved the capacity of thermal energy storage up to 52% and reduced the battery temperature by 15℃. Shabas-Ahamed et al. synthesized a matrix material (OP) by covalently functionalizing octadecyl with polyethylene-methyl acrylate-glycidyl methacrylate polymer through nucleophilic ring-opening reaction of epoxy. In addition, high thermal conductivity fillers are introduced into the OP matrix to improve the overall thermal conductivity.

[0005] At the same time, the prior art often manages the heat of electronic devices by forced air cooling, liquid cooling, and direct cooling. Forced air cooling uses air as the heat transfer medium and directly allows air to carry away heat through an exhaust fan. This cooling method requires an external power supply and consumes energy, and has low heat dissipation efficiency. Liquid cooling technology removes heat from the device by convective heat transfer of the liquid. However, liquid cooling has high requirements for system air tightness and is costly and complex to maintain. Direct cooling removes heat from the device system by rapid evaporation of the refrigerant in the evaporator. However, direct cooling has the problem of low cooling efficiency. SUMMARY

[0006] The purpose of the present application is to overcome the technical defects in the prior art and provide a preparation method of a hydrated salt composite phase change film.

[0007] Another purpose of the present application is to provide a hydrated salt composite phase change film obtained by the above preparation method.

[0008] Another purpose of the present application is to provide the application of the hydrated salt composite phase change film in the thermal management of electronic devices.

[0009] Another purpose of the present application is to provide an electronic device.

[0010] The technical scheme adopted to achieve the purpose of the present application is as follows:

[0011] A preparation method of a hydrated salt composite phase change film, comprising the following steps:

[0012] Step 1, preparation of hydrated salt composite phase change material: after the inorganic hydrated salt is stirred and melted, a nucleating agent, a thickening agent are added in sequence to obtain a hydrated salt mixture, then a packaging matrix is added, after the packaging matrix fully absorbs the hydrated salt mixture, vacuum impregnation is carried out under heating, and the obtained hydrated salt composite phase change material is taken out and placed in an oven for liquid leakage test until the trace of liquid leakage disappears completely, and is recorded as CPCM;

[0013] Step 2, polyvinylidene fluoride (PVDF) is added into N-N dimethylformamide (DMF) and heated and stirred to mix uniformly to obtain a mixed solution;

[0014] Step 3, the hydrated salt composite phase change material obtained in step 1 is ground into powder and added into the mixed solution obtained in step 2, and heated and stirred to obtain a phase change mixed slurry, the phase change mixed slurry is scraped and coated, and a hydrated salt composite phase change film is obtained by a deionized water bath method, and is recorded as HSPCF.

[0015] In the above technical solution, in step 1, the stirring and melting is carried out by water bath heating and stirring, and the temperature of the water bath heating is 40-90℃.

[0016] In the above technical solution, in step 1, the inorganic hydrated salt is sodium acetate trihydrate (SAT) or sodium sulfate decahydrate, and the nucleating agent is borax, aluminum oxide or disodium hydrogen phosphate dodecahydrate;

[0017] When the nucleating agent is borax or aluminum oxide, the mass ratio of the nucleating agent to the inorganic hydrated salt is (1-3):100;

[0018] When the nucleating agent is disodium hydrogen phosphate dodecahydrate and the inorganic hydrated salt is sodium sulfate decahydrate, the mass ratio of the nucleating agent to the inorganic hydrated salt is (1-5):100.

[0019] In the above technical solution, in step 1, the thickening agent is cooked lotus root starch (CLRS), carboxymethyl cellulose (CMC) or sodium polyacrylate (PSSA);

[0020] When the thickening agent is cooked lotus root starch, the mass ratio of the thickening agent to the inorganic hydrated salt is (1-6):100; when the thickening agent is carboxymethyl cellulose, the mass ratio of the thickening agent to the inorganic hydrated salt is (1-3):100; when the thickening agent is sodium polyacrylate, the mass ratio of the sodium polyacrylate to the inorganic hydrated salt is 0.5:100.

[0021] In the technical scheme, in the step 1, the packaging matrix is expanded graphite (EG), the expanded graphite is obtained by expanding expandable graphite in a microwave oven at a power of 750-1500 W for 30-120 s, and the mass ratio of the expanded graphite to the inorganic hydrated salt is (1-5):100, preferably (2-3):100, and more preferably 2.5:100.

[0022] In the technical scheme, in the step 1, the vacuum impregnation pressure is-0.06 to-0.08 MPa, the vacuum impregnation temperature is 40-90 ℃, and the vacuum impregnation time is 7-15 min.

[0023] In the technical scheme, in the step 1, the liquid leakage temperature is 40-80 ℃, and the liquid leakage time is 3-12 h.

[0024] In the technical scheme, in the step 2, after the hydrated salt composite phase change material is ground into powder, it is sieved by a 60-80 mesh sieve and added into the mixed solution.

[0025] In the technical scheme, in the step 2, the mass ratio of the polyvinylidene fluoride to the N-N dimethylformamide is (8-13):100, the heating and stirring temperature is 40-60 ℃, and the stirring time is 2-24 h.

[0026] In the technical scheme, in the step 3, the mass ratio of the hydrated salt composite phase change material to the polyvinylidene fluoride is 8:(1-5), preferably, the mass ratio of the hydrated salt composite phase change material to the polyvinylidene fluoride is 8:(3-4), and more preferably 8:3, the heating and stirring temperature is 40-60 ℃, the stirring rate is 5-15 rpm, and the stirring time is 1-3 h.

[0027] In the technical scheme, in the step 3, the drying temperature is not higher than 60 ℃.

[0028] Another aspect of the present application also includes the hydrated salt composite phase change film obtained by the preparation method.

[0029] Another aspect of the present application also includes the application of the hydrated salt composite phase change film in electronic device thermal management.

[0030] Another aspect of the present application also includes an electronic device comprising a hotspot device, a heat dissipation component, and the hydrated salt composite phase change film between the hotspot device and the heat dissipation component, preferably, the hotspot device is a battery or a CPU.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] 1.The hydrated salt composite phase change film of the present application dissipates the heat of electronic devices through the hydrated salt phase change endothermic and the thermal conduction of expanded graphite, has temperature response flexibility in the phase change process, reduces the interface thermal resistance, and improves the heat dissipation efficiency.

[0033] 2.The expanded graphite is used in the preparation process of the present application, which can not only absorb the hydrated salt mixture as a packaging material, but also can enhance the thermal conductivity of the hydrated salt composite phase change film as a thermal conductive filler, and the pretreatment process is simple, cheap and easy to obtain.

[0034] 3.The hydrated salt composite phase change film of the present application has good thermal flexibility, which can be cut to adapt to electronic devices of different sizes before use, and the thermal flexibility can help it to closely contact with the heat source device to avoid air resistance caused by excess gap, thereby improving the heat dissipation efficiency of the electronic device.

[0035] 4.The electronic device heat management technology using hydrated salt composite phase change material as medium of the present application has simple preparation process, low cost, and does not need additional cooling equipment. It has excellent flame retardance and excellent heat storage capacity, has high heat dissipation capacity, and can also avoid safety accidents to a greater extent. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is the preparation process and application principle diagram of the hydrated salt composite phase change film.

[0037] Figure 2 It is the scanning electron microscope graph of the hydrated salt composite phase change material of Example 1 of the present application.

[0038] Figure 3 It is the X-ray diffraction spectrum of the hydrated salt composite phase change material of Example 1 of the present application.

[0039] Figure 4 It is the DSC curve graph of the five kinds of hydrated salt composite phase change materials prepared in Example 1 of the present application.

[0040] Figure 5 It is the heat enthalpy and thermal conductivity column chart of the five kinds of hydrated salt composite phase change materials prepared in Example 11 of the present application.

[0041] Figure 6 It is the scanning electron microscope graph of the hydrated salt composite phase change film of Example 1.

[0042] Figure 7 It is the DSC curve graph of the hydrated salt composite phase change film of Examples 1-3.

[0043] Figure 8 It is the thermal conductivity performance graph of the hydrated salt composite phase change film of Examples 1-3.

[0044] Figure 9This is a thermal cycling performance diagram of the hydrated salt composite phase change film of Example 1.

[0045] Figure 10 This is the dynamic mechanical analysis curve of the hydrated salt composite phase change film of Example 1.

[0046] Figure 11 These are experimental diagrams of the battery thermal runaway simulation process, wherein (a) is a schematic diagram of a battery equipped with and without the hydrated salt composite phase change film of Example 1, (b) is a schematic diagram of the battery module of the present invention (containing a thermocouple), and (c) is a diagram of the battery module thermal runaway simulation test experiment.

[0047] Figure 12 : This is an infrared thermal imaging image of the battery module in the thermal runaway simulation experiment, where Bare is a battery module without any heat dissipation material, and PFC is a battery module equipped with the hydrated salt composite phase change film of Example 1.

[0048] Figure 13 The hot spot temperature change curve of the thermal runaway battery module before and after the integration of the hydrated salt composite phase change film.

[0049] Figure 14 This is an assembly diagram of the hydrated salt composite phase change film, Al2O3 silicone grease sheet and aluminum nitride silicone grease sheet of Example 1 with the CPU when used as heat dissipation materials.

[0050] Figure 15 This is a comparison chart of the heat dissipation capacity of the CPU when the hydrated salt composite phase change film, Al2O3 silicone grease sheet and aluminum nitride silicone grease sheet of Example 1 are used as heat dissipation materials. DETAILED DESCRIPTION

[0051] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0052] Example 1

[0053] like Figures 1-15 As shown, a method for preparing a hydrated salt composite phase change film comprises the following steps:

[0054] Step 1, preparation of hydrated salt composite phase change material: after the sodium acetate trihydrate SAT was melted at 65℃ by water bath heating and stirring with a magnetic stirrer, the sodium phosphate dibasic dodecahydrate STD and carboxymethyl cellulose CMC were added in sequence to form a hydrated salt mixture, then the expanded graphite EG was added as an encapsulation matrix, and the hydrated salt composite phase change material was obtained by vacuum impregnation after the encapsulation matrix fully absorbed the hydrated salt mixture, liquid leakage test at 60℃ for 4h until the liquid leakage trace completely disappeared, and the hydrated salt composite phase change material was recorded as SAT / 2.5EG CPCM, wherein the mass ratio of the sodium acetate trihydrate to the expanded graphite was 100:2.5.

[0055] Step 2, polyvinylidene fluoride (PVDF) was added to N-N dimethylformamide (DMF) and heated and stirred at 45℃ for 3h until a clear and transparent mixed solution was obtained.

[0056] Step 3, the hydrated salt composite phase change material obtained in step 1 was ground into powder and sieved with a 60-80 mesh sieve, then added to the mixed solution obtained in step 2, heated and stirred at 45℃ at a speed of 15rpm for 2h to obtain a phase change mixed slurry, the phase change mixed slurry was scraped and coated into a mold, deionized water was used to wash off the mold, and the mold was dried to semi-dryness to obtain a hydrated salt composite phase change film, recorded as HSPCF-3, wherein the mass ratio of the polyvinylidene fluoride to the hydrated salt composite phase change material was 3:8.

[0057] As shown in the preparation process of the hydrated salt composite phase change film of the present application. Figure 1 Firstly, the hydrated salt composite phase change material (CPCM) was prepared by vacuum impregnation using sodium acetate trihydrate (SAT) and porous expanded graphite (EG). Then, a wet film containing a certain proportion of polyvinylidene fluoride (PVDF) and N-N dimethylformamide (DMF) was cast by a scraper and a roller press. The hydrated salt composite phase change film was obtained by immersing the wet film in a deionized water bath and dissolving with a solvent.

[0058] When the temperature of the hotspot device (in this embodiment, specifically the CPU (chip) and 18650 battery) reaches the phase change temperature of the hydrated salt, the hydrated salt in the hydrated salt composite phase change film undergoes solid-liquid phase change and absorbs the heat generated by the hotspot device, and the heat absorbed is related to the latent heat of phase change of the hydrated salt. Figure 1The hydrated salt used at this time is sodium acetate trihydrate, and the phase transition temperature is 58°C. When the temperature reaches this value, the hydrated salt composite phase change film continuously absorbs heat to undergo solid-liquid phase transition, thereby achieving the effect of dissipating the heat of the hotspot device and reducing the temperature. At the same time, below the phase transition temperature, the hydrated salt composite phase change film has rigidity and cannot be closely attached to the hotspot device. The gap is filled with air, and the thermal resistance is very high. Heat conduction only depends on the contact point with the hydrated salt composite phase change film, and the heat transfer efficiency is low. After the hydrated salt composite phase change film undergoes phase transition to obtain flexibility, the gap between the hotspot device and the heat dissipation assembly is replaced by the hydrated salt composite phase change film. The contact area between the hydrated salt composite phase change film and the hotspot device increases, and the heat transfer is more efficient.

[0059] It can be seen from Figure 2 that the hydrated salt is adsorbed into the pores and interlayers of the expanded graphite EG due to capillary force and surface tension. Most of the pore surfaces are also occupied by sodium acetate trihydrate SAT, and the hydrated salt particles are spherical or massive.

[0060] It can be seen from Figure 3 that the XRD pattern shows the characteristic peaks of sodium acetate trihydrate SAT (2θ = 11.43°, 19.07°, 29.72°, 37.69°, 51.4°), the characteristic peaks of expanded graphite EG (2θ = 25.56°), and the characteristic peaks of carboxymethyl cellulose and disodium hydrogen phosphate dodecahydrate can also be observed.

[0061] As Figures 4-5 shown, the mass ratio of sodium acetate trihydrate to expanded graphite used in this embodiment is 100:2.5. This is because different mass ratios of sodium acetate trihydrate to expanded graphite are used to prepare hydrated salt composite phase change materials. When the mass ratio of the two is 100:2.5, the heat enthalpy and thermal conductivity of the hydrated salt composite phase change material are optimal, as follows:

[0062] When the mass ratio of sodium acetate trihydrate to expanded graphite is 100:1, the obtained hydrated salt composite phase change material is denoted as SAT / 1EG CPCM. The heat enthalpy and thermal conductivity of SAT / 1EG CPCM are 168.3 J / g and 1.34 W·m -1 ·K -1 , respectively.

[0063] When the mass ratio of sodium acetate trihydrate to expanded graphite is 100:1.5, the obtained hydrated salt composite phase change material is denoted as SAT / 1.5EG CPCM. The heat enthalpy and thermal conductivity of SAT / 1.5EG CPCM are 188.1 J / g and 1.42 W·m -1 ·K -1 , respectively.

[0064] When the mass ratio of sodium acetate trihydrate to expanded graphite is 100:2, the obtained hydrated salt composite phase change material is denoted as SAT / 2EG CPCM, and the enthalpy and thermal conductivity of SAT / 2EG CPCM are 194.0 J / g and 1.46 W·m -1 ·K -1 .

[0065] When the mass ratio of sodium acetate trihydrate to expanded graphite is 100:3, the obtained hydrated salt composite phase change material is denoted as SAT / 3EG CPCM, and the enthalpy and thermal conductivity of SAT / 3EG CPCM are 198.5 J / g and 1.92 W·m -1 ·K -1 .

[0066] It can be seen from Figure 4 that the above hydrated salt composite phase change materials undergo phase transition at about 58℃, and with the increase of the content of expanded graphite, the phase transition enthalpy of the hydrated salt composite phase change material first increases and then decreases.

[0067] It can be seen from Figure 5 that when the mass ratio of sodium acetate trihydrate to expanded graphite is 100:2.5, the enthalpy and thermal conductivity of the hydrated salt composite phase change material are optimal, which are 210.7 J / g and 1.74 W·m -1 ·K -1 .

[0068] Example 2

[0069] The preparation method of the hydrated salt composite phase change film of this example is different from that of Example 1 only in that the mass ratio of polyvinylidene fluoride to hydrated salt composite phase change material is 4:8, and finally the hydrated salt composite phase change film is obtained, denoted as HSPCF-2.

[0070] Example 3

[0071] The preparation method of the hydrated salt composite phase change film of this example is different from that of Example 1 only in that the mass ratio of polyvinylidene fluoride to hydrated salt composite phase change material is 5:8, and finally the hydrated salt composite phase change film is obtained, denoted as HSPCF-1.

[0072] As shown in Table 1, the enthalpy and thermal conductivity of the hydrated salt composite phase change films of Examples 1-3 are as follows:

[0073] Table 1. Enthalpy and thermal conductivity of hydrated salt composite phase change film

[0074]

[0075] It can be seen from Figure 6It can be seen that the black part is the PVDF binder, and the white part is the hydrated salt composite phase change material.

[0076] It can be seen that when the mass ratio of the polyvinylidene fluoride to the hydrated salt composite phase change material is 3:8, the latent heat of phase change of the hydrated salt composite phase change film can reach 176.7 J / g. Figure 7 When the mass ratio of the polyvinylidene fluoride to the hydrated salt composite phase change material is 4:8, the latent heat of phase change of the hydrated salt composite phase change film can reach 148.9 J / g; and when the mass ratio of the polyvinylidene fluoride to the hydrated salt composite phase change material is 5:8, the latent heat of phase change of the hydrated salt composite phase change film can reach 132.8 J / g.

[0077] It can be seen that when the mass ratio of the polyvinylidene fluoride to the hydrated salt composite phase change material is 3:8, the thermal conductivity of the hydrated salt composite phase change film at 25℃ is 1.64 W·m -1 ·K -1 , indicating that it has good heat conduction capacity. Figure 8 When the mass ratio of the polyvinylidene fluoride to the hydrated salt composite phase change material is 4:8, the thermal conductivity of the hydrated salt composite phase change film at 25℃ is 1.56 W·m -1 ·K -1 ; and when the mass ratio of the polyvinylidene fluoride to the hydrated salt composite phase change material is 5:8, the thermal conductivity of the hydrated salt composite phase change film at 25℃ is 1.45 W·m -1 ·K -1 . Thus, when the mass ratio of the polyvinylidene fluoride to the hydrated salt composite phase change material is 3:8, the composite phase change material has more excellent heat conduction capacity.

[0078] Taking the hydrated salt composite phase change film prepared in Example 1 as an example, it can be seen from the following figure that after 500 times of thermal cycle test, the hydrated salt composite phase change film still has a latent heat of phase change of 150.0 J / g, indicating that it has good thermal stability. Figure 9

[0079] Taking the hydrated salt composite phase change film prepared in Example 1 as an example, it can be seen from the following figure that after 500 times of thermal cycle test, the hydrated salt composite phase change film still has a latent heat of phase change of 150.0 J / g, indicating that it has good thermal stability. Figure 10 It can be seen that the hydrated salt composite phase change film of the present application has temperature response flexibility as the temperature rises, and specifically, Figure 10 is a dynamic mechanical curve, which is used to analyze the thermal mechanical properties of the hydrated salt composite phase change film. In the figure, Storage modulus is the storage modulus E', Loss modulus is the loss modulus E ” , and Loss factor is the loss factor tanδ. It can be seen from the figure that the storage modulus E' decreases as the temperature rises, and no sudden transition is observed within the test temperature range, indicating that the stiffness continuously weakens. After 52℃, the loss modulus E​” The stiffness decreases with increasing temperature, indicating that the hydrated salt begins to absorb significant heat and undergoes a phase transition. A relaxation peak is observed in the loss factor curve at approximately 65°C, indicating that the hydrated salt has completed its phase transition. In summary, the flexibility of the hydrated salt composite phase change film increases with increasing temperature, exhibiting maximum flexibility and minimum stiffness at high temperatures.

[0080] Application Example 1

[0081] Thermal failure experiments were conducted on 18650 battery modules to analyze the thermal management capabilities of hydrated salt composite phase change films.

[0082] like Figure 11 As shown in (a) and (b) in the figure, the hydrated salt composite phase change film of Example 1 is used as a heat dissipation material to wrap 19 18650 batteries respectively, and the battery at the center position (a total of one battery) is used as the central battery and is recorded as HSPCF-C. An inner circle of batteries (a total of 6 batteries) are placed around the central battery and are recorded as HSPCF-IR. An outer circle of batteries (a total of 12 batteries) are placed around the inner circle battery and are recorded as HSPCF-OR. The 19 batteries are connected in series in sequence to obtain a battery module. At the same time, the battery module obtained according to the above method and not equipped with the hydrated salt composite phase change film is used as a control group, and the central battery is recorded as Bare-C, the inner circle battery is recorded as Bare-IR, and the outer circle battery is recorded as Bare-OR. The thermal runaway state of the battery module equipped with the hydrated salt phase change film prepared by the present invention and the control group is simulated by a large current discharge of 6C (15A). As shown Figure 11 As shown in (b), a thermocouple is inserted into each of the left and right sides of the five batteries on the center line, and the six thermocouples are arranged in a row, as shown in FIG. Figure 11 As shown in (c), a thermocouple and a multi-channel temperature recorder are used to detect and record the temperature changes of the battery module and the control group, and an in-situ infrared thermal imager is used to record the infrared images of the battery module and the control group.

[0083] Figure 12 Infrared thermal imaging images of a battery module equipped with a hydrated salt composite phase change film and a control group during the discharge process (1 to 600 seconds). As can be seen from the image, after the same discharge time, the surface temperature of the battery module equipped with the hydrated salt composite phase change film is significantly lower than that of the control group, demonstrating the temperature control capability of the hydrated salt composite phase change film.

[0084] like Figure 13As shown, after high rate and large current discharge, the maximum surface temperature of HSPCF-C is reduced by 10.6℃ compared with Bare-C, the maximum surface temperature of HSPCF-IR is reduced by 11.6℃ compared with Bare-IR, and the maximum surface temperature of HSPCF-OR is reduced by 11℃ compared with Bare-OR, which indicates that the hydrated salt phase change film can effectively inhibit the thermal runaway of the battery module and ensure the safety of the battery.

[0085] Application Example 2

[0086] The hotspot device cooling effect of the hydrated salt composite phase change film was verified by switching the CPU to maximum power output to increase the surface temperature thereof. The hydrated salt composite phase change material prepared in Example 1, an Al2O3 silicone pad and an AIN silicone pad were respectively used as the heat dissipation material (thermal interface material) of the CPU, and the heat dissipation material was assembled with the CPU according to Figure 14 (heat dissipation material is located between the CPU and the heat dissipation component). The CPU was switched to maximum power by AIDA64 software to increase the surface temperature of the CPU. The real-time surface temperature of the test CPU was recorded by using a K-type thermocouple, and it can be known that Figure 15 when the Al2O3 silicone pad and the AIN silicone pad were used as the heat dissipation material, the surface temperature of the CPU rose to 74.5℃ and 76.4℃ respectively after 400 seconds. When the hydrated salt composite phase change film of Example 1 was used as the heat dissipation material, the maximum surface temperature of the CPU slowly rose to 58℃ after 620 seconds, and the temperature slightly decreased during the phase change. Therefore, the hydrated salt composite phase change film reduces the maximum surface temperature of the CPU by 20℃ compared with other heat dissipation materials, indicating that the hydrated salt composite phase change film has excellent cooling capacity in the thermal management of electronic devices.

[0087] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a hydrated salt composite phase change film, characterized in that: The following steps are involved: Step 1, preparation of a hydrated salt composite phase change material: stirring and melting an inorganic hydrated salt, sequentially adding a nucleating agent and a thickener to obtain a hydrated salt mixture, then adding an encapsulating matrix, and after the encapsulating matrix has fully absorbed the hydrated salt mixture, vacuum impregnating the mixture under heating conditions, removing the mixture and placing it in an oven for liquid leakage testing until any trace of liquid leakage disappears, thereby obtaining a hydrated salt composite phase change material; Step 2, adding polyvinylidene fluoride to NN dimethylformamide, heating and stirring to mix uniformly to obtain a mixed solution; Step 3: Grind the hydrated salt composite phase change material obtained in step 1 into powder and add it to the mixed solution obtained in step 2, heat and stir to obtain a phase change mixed slurry, apply the phase change mixed slurry by scraping, and obtain a hydrated salt composite phase change film by a deionized water bath method.

2. The preparation method according to claim 1, characterized in that In step 1, the inorganic hydrated salt is sodium acetate trihydrate or sodium sulfate decahydrate, and the nucleating agent is borax, aluminum oxide or disodium hydrogen phosphate dodecahydrate; When the nucleating agent is borax or aluminum oxide, the mass ratio of the nucleating agent to the inorganic hydrated salt is (1-3):100; When the nucleating agent is disodium hydrogen phosphate dodecahydrate and the inorganic hydrated salt is sodium sulfate decahydrate, the mass ratio of the nucleating agent to the inorganic hydrated salt is (1-5):

100.

3. The preparation method according to claim 1, characterized in that In step 1, the thickener is cooked lotus root starch, carboxymethyl cellulose or sodium polyacrylate; When the thickener is cooked lotus root starch, the mass ratio of the thickener to the inorganic hydrated salt is (1-6):100; when the thickener is carboxymethyl cellulose, the mass ratio of the thickener to the inorganic hydrated salt is (1-3):100; when the thickener is sodium polyacrylate, the mass ratio of sodium polyacrylate to the inorganic hydrated salt is 0.5:

100.

4. The preparation method according to claim 1, characterized in that In the step 1, the encapsulation substrate is expanded graphite, and the expanded graphite is obtained by expanding expandable graphite in a microwave oven at a power of 750 to 1500 W for 30 to 120 seconds. The mass ratio of the expanded graphite to the inorganic hydrated salt is (1 to 5):100, preferably (2 to 3):100, and more preferably 2.5:

100.

5. The preparation method according to claim 1, characterized in that In the step 1, the pressure of the vacuum impregnation is -0.06 to -0.08 MPa, the temperature of the vacuum impregnation is 40 to 90° C., and the time of the vacuum impregnation is 7 to 15 minutes.

6. The preparation method according to claim 1, characterized in that In the step 2, the mass ratio of the polyvinylidene fluoride to NN dimethylformamide is (8-13):100, the heating and stirring temperature is 40-60° C., and the stirring time is 2-24 hours.

7. The preparation method according to claim 1, characterized in that In the step 3, the mass ratio of the hydrated salt composite phase change material to polyvinylidene fluoride is 8:(1-5), preferably, the mass ratio of the hydrated salt composite phase change material to polyvinylidene fluoride is 8:(3-4), and more preferably 8:3, the heating and stirring temperature is 40-60°C, the stirring rate is 5-15 rpm, and the stirring time is 1-3h.

8. The hydrated salt composite phase change film obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the hydrated salt composite phase change film according to claim 8 in thermal management of electronic devices.

10. An electronic device, characterized in that: The invention comprises a hot spot device, a heat dissipation component and the hydrated salt composite phase change film according to claim 8 located between the hot spot device and the heat dissipation component. Preferably, the hot spot device is a battery or a CPU.

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