Hydrated salt phase change microcapsule for power battery and preparation method of hydrated salt phase change microcapsule

Abstract

The invention relates to the technical field of new energy automobile power battery thermal management, in particular to a hydrated salt phase change microcapsule for a power battery and a preparation method of the hydrated salt phase change microcapsule. According to the specific technical scheme, hydrated salt serves as a core material, methyl methacrylate serves as a shell material monomer, the monomers are polymerized on the surfaces of hydrated salt liquid drops to form a polymethyl methacrylate shell layer through an interfacial polymerization method, effective packaging of a phase change material (hydrated salt) is achieved, and the microcapsule with high phase change latent heat, low leakage rate and long cycle life is obtained. In addition, other doped auxiliary materials are deposited on an oil-water interface to improve the heat conductivity of the microcapsule. And mixing the microcapsules with heat-conducting oil to prepare suspension liquid, and driving the suspension liquid to circularly flow between the power battery packs by a peristaltic pump. According to the invention, microcapsules and liquid cooling heat dissipation are combined to provide a new thought and practical and effective temperature control and heat dissipation effects for a heat management scheme of the power battery pack.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy vehicle power battery thermal management, in particular to a hydrated salt phase change microcapsule for power battery and a preparation method thereof. BACKGROUND

[0002] In recent years, new energy vehicle technology has developed rapidly, and the demand for power batteries has also gradually increased. Battery endurance, service life and working power have been greatly improved to meet the needs of vehicles. Along with this, the safety problem of new energy vehicles has also occurred frequently, among which the battery explosion phenomenon has occurred frequently, causing serious threat to people's life and property safety. The reason for the explosion of power batteries is mainly due to the short circuit of positive and negative poles caused by component aging or strong extrusion and collision deformation puncture, etc. In addition, in order to meet the demand for fast charging, the charging power is getting larger and larger, and during the continuous discharging process, especially under the condition of vehicle acceleration, the power of the power battery increases instantaneously, which will also quickly produce heat, causing the temperature of the battery to continuously rise. Although it will not spontaneously cause a fire accident during normal driving, it will shorten the service life of the power battery and weaken the performance of the battery, etc. Therefore, it is necessary to effectively manage the heat of the power battery of the new energy vehicle.

[0003] The current common heat management methods include air cooling, liquid cooling, heat pipe cooling, phase change material cooling, multi-mode coupled heat dissipation, etc. Air cooling has low cost, but it is noisy, occupies a large space, is affected by the environment, and has limited heat dissipation; liquid cooling has good heat dissipation effect, uniform temperature, low noise, small occupation, flexible structure, and can meet complex installation requirements; phase change material cooling has good heat dissipation and good temperature stability, and can dissipate heat spontaneously, but cannot realize spontaneous solidification in a fixed environment and cannot realize continuous phase change heat absorption; heat pipe cooling has high heat conduction efficiency, but has high cost and complex installation; multi-mode coupled heat dissipation can combine the advantages of multiple heat dissipation methods and complement the disadvantages. The heat dissipation demand of power batteries is increasing, and it is urgent to develop a new heat management method to solve the problem of battery heat accumulation.

[0004] In view of the above problems of electric vehicle heat management, there are currently solutions of phase change materials or phase change materials coupled with other methods, such as patent application publication No. CN118144644A discloses a power battery cold and hot comprehensive management system and working method based on phase change cooling and thermoelectric power generation, which arranges the battery plate and the phase change material in a sandwich structure, inserts a heat pipe in the phase change material, and drives the air flow in the heat pipe with wind to achieve heat dissipation effect. Although this method can realize the continuous phase change of the phase change material to achieve continuous heat dissipation effect, the heat dissipation effect of air is limited and is greatly affected by the ambient temperature.

[0005] For example, patent publication No. CN208570863U discloses a cold and hot dual-purpose battery pack thermal management structure based on phase change coupled air cooling, which adopts a phase change material and air cooling coupled heat dissipation mode for thermal management, wraps the battery with a heat pipe sleeve, fills the heat pipe with a phase change material, connects the heat pipe sleeve with a uniform cooling plate and fins, and transmits the battery heat to the fins to promote air flow between the fins to achieve heat dissipation effect by using a fan, but has the same shortcomings of air cooling as patent application publication No. CN118144644A.

[0006] In addition, only patent application publication No. CN120663770A discloses a liquid-cooled charging gun temperature control method for electric vehicles, which improves the dynamic heat dissipation performance and working condition adaptability of the liquid-cooled charging gun by constructing a bionic fractal flow channel-phase change microcapsule-magnetic field regulation, but the heat dissipation scheme is applied to the thermal management of the charging gun of a new energy vehicle, and phase change and liquid cooling are not used in the field of power battery thermal management.

[0007] In summary, phase change materials are commonly used in combination with air cooling for battery thermal management, but have low circulation heat dissipation efficiency and large volume, and have great limitations. The combination with liquid cooling is less common for power battery thermal management, and there is a lack of reasonable and effective application scheme, which limits the application and actual performance of this coupling method in the field. Therefore, the present application develops a complete and feasible phase change coupled liquid cooling heat dissipation method for battery thermal management. SUMMARY

[0008] In view of the deficiencies of the prior art, the present application provides a hydrated salt phase change microcapsule for power batteries and a preparation method thereof to solve the problems of battery life reduction and performance decline caused by battery thermal runaway and heat accumulation in new energy vehicles.

[0009] To achieve the above object, the present application is realized by the following technical scheme: The present application discloses a hydrated salt phase change microcapsule for power batteries, which uses hydrated salt as the core material, adds an interface anchoring material, uses methyl methacrylate as the shell-forming monomer, adds an emulsifier and a nano material, and uses an interfacial polymerization method to encapsulate the hydrated salt with a poly methyl methacrylate organic shell layer polymerized, thereby obtaining the hydrated salt phase change microcapsule.

[0010] Preferably, the hydrated salt is dodecahydrate disodium hydrogen phosphate, the phase change melting point of the hydrated salt is 39-40℃, the interface anchoring material is maleic anhydride, the emulsifier is a mixture of Span series emulsifiers and Tween series emulsifiers in equal proportions, and the nano material is one of multi-walled carbon nanotubes, carboxymethyl carbon nanotubes and silicon carbide nanowires.

[0011] Accordingly, a method for preparing hydrated salt phase change microcapsules for power batteries includes the following steps: S1. Preparation of aqueous phase: Mix disodium hydrogen phosphate dodecahydrate with deionized water and heat and stir above the phase transition temperature until fully dissolved; then add maleic anhydride and heat and stir until dissolved; then add emulsifier and stir evenly to obtain aqueous solution. S2. Oil phase preparation: Using n-hexadecane as a continuous phase solvent, nanomaterials are added, and the mixture is stirred and ultrasonically mixed evenly. An emulsifier is then added and stirred evenly to obtain an oil phase suspension. S3. Emulsion preparation: The aqueous solution prepared in S1 is added dropwise to the oil suspension prepared in S2. Under the action of shear force and stirring, emulsification is carried out at a temperature above the phase transformation melting point to form a uniform and stable water-in-oil W / O type emulsion. S4. Microcapsule preparation: The emulsion prepared in S3 was heated to the reaction temperature, then 2',2-azobisisobutyronitrile was added, and methyl methacrylate was added dropwise. Then, n-hexadecane was added to replenish the oil phase environment. After heating, stirring, centrifugation, washing, and drying, hydrated salt phase change microcapsule powder was obtained.

[0012] Preferably, in step S1, the heating temperature is 50°C, the stirring speed is 600-1000 rpm, and the stirring time is 30 min.

[0013] Preferably, in step S2, the mass of the added nanomaterial is 0.3-1.2 wt% of the solvent mass, the stirring time is 20 min, the stirring speed is 800-1000 rpm, and the ultrasonic time is 10 min.

[0014] Preferably, in step S3, the temperature for dripping, shearing, and stirring is maintained at 50°C, the shearing speed is 12000-16000 rpm, the shearing time is 10 min, the stirring speed is 1000 rpm, and the stirring time is 20 min.

[0015] Preferably, in step S4, the reaction temperature is 70-80℃, the reaction time is 5-6h, the stirring speed is 600rpm, the washing reagents are cyclohexane and deionized water, and the product is dried at room temperature.

[0016] Correspondingly, a liquid-cooled thermal management method for the prepared hydrated salt phase change microcapsules for power batteries involves laying liquid-cooled pipes interspersed between battery packs, then mixing the hydrated salt phase change microcapsules with heat-conducting oil to form a suspension, and using a peristaltic pump to circulate it in the liquid-cooled pipes. The temperature control and heat dissipation of the battery pack are achieved through the phase change heat absorption of the hydrated salt phase change microcapsules.

[0017] Preferably, the heat transfer oil has a thermal conductivity of 0.458 W / (m·K) and a dynamic viscosity of 30.16 mm. 2 / s, density is 0.868g / cm³ 3 The hydrated salt microcapsules are added at a mass ratio of 1-5 wt%, and the hydrated salt microcapsules are uniformly dispersed in the heat transfer oil by stirring and ultrasonication.

[0018] Preferably, the liquid cooling pipeline is laid out in a serpentine pattern. The peristaltic pump pumps the suspension into the pipeline from the cold end. The hydrated salt in the hydrated salt microcapsules undergoes a phase change and melts to absorb heat through heat transfer from the battery pack, thereby controlling the temperature of the battery pack. Then, it flows back to the cold end to cool and undergo a phase change and solidify. The flow rate of the peristaltic pump is 1-2 cm / s.

[0019] The present invention has the following beneficial effects: 1. The phase change microcapsules used in this invention have a self-heating function. When the battery pack temperature is higher than the phase change temperature of the microcapsules, they will melt and absorb heat on their own to weaken or reduce the upward trend of the battery pack temperature and play a role in buffering and temperature control.

[0020] 2. Since the phase change of microcapsules is spontaneous and does not require additional energy to drive it, adding phase change microcapsules to the original liquid cooling can provide additional temperature control. In addition, disodium hydrogen phosphate dodecahydrate is biodegradable and will not pose a significant disposal challenge after disposal. It is energy-saving and environmentally friendly, which is consistent with the requirements of national strategic development.

[0021] 3. The hydrated salt in the microcapsule core of the present invention has a high latent heat of phase change, which can ensure sufficient heat absorption during use. The outer shell is made of organic shell, which has high toughness and can resist external pressure to maintain the integrity of the microcapsule. In addition, the organic shell has a higher polymerization crosslinking density, which ensures that the hydrated salt will not easily leak. It has a long cycle life, low supercooling, and low phase separation, which can maintain long-term cycle use and meet the long-term charge and discharge requirements of battery packs.

[0022] 4. The phase transition temperature of disodium hydrogen phosphate dodecahydrate is 39-40℃. By encapsulating it in microcapsules, a larger specific surface area and more nucleation sites are provided during the phase transition process, reducing the phase transition temperature of the microcapsules to 21-22℃, which is suitable for the operating temperature of the battery pack.

[0023] 5. The phase change material (hydrated salt) uses phosphate salt hydrate, which is non-flammable. Even if a vehicle accident causes a short circuit inside the battery and leads to deflagration, the exposed phase change material can form a phosphate flame retardant layer, which can inhibit combustion to a certain extent.

[0024] 6. Compared to the traditional single fixed phase change cooling method, when the total heat generated by the battery exceeds the upper limit of the microcapsule phase change heat absorption and energy storage, it can no longer play a role, resulting in poor continuous working ability in a fixed environment. This invention combines liquid cooling, which can carry out the microcapsules that have completed heat absorption and cool and solidify as the liquid flows, and then continue to be input into the system to play a role, showing strong cycle performance.

[0025] 7. Compared to combining with air cooling or heat pipes, the method of coupling with liquid cooling has a faster heat dissipation rate, is less affected by the environment, and can adapt to batteries of various shapes or complex working environments. Attached Figure Description

[0026] Figure 1 This is a macroscopic morphology diagram of the hydrated salt phase change microcapsules of the present invention; Figure 2 This is a SEM image of the microstructure of the phase change microcapsules of the present invention; Figure 3 This is a thermal performance analysis diagram of the microcapsules of the present invention; Figure 4 This is a conceptual diagram of the battery thermal management of the hydrated salt phase change microcapsules coupled with liquid cooling according to the present invention; Figure 5 This is a diagram illustrating the practical application of the microcapsules coupled with liquid cooling in this invention for battery thermal management. Figure 6 This invention relates to the macroscopic temperature performance and temperature difference variation trend of the battery pack under battery discharge conditions. Figure 7 This invention relates to the macroscopic temperature performance and temperature difference trend of the battery pack during battery charging. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0029] This invention discloses a hydrated salt phase change microcapsule for power batteries. The hydrated salt is used as the core material (i.e., phase change material), an interface anchoring material is added, methyl methacrylate is used as the shell-forming monomer, an emulsifier is added to reduce the surface energy to form a stable emulsion, and nanomaterials are added to improve performance. The material is deposited at the oil-water interface and the monomer is polymerized into a polymethyl methacrylate organic shell to effectively encapsulate the hydrated salt, thus obtaining the hydrated salt phase change microcapsule.

[0030] Furthermore, the hydrated salt is disodium hydrogen phosphate dodecahydrate, and the phase transition melting point of the hydrated salt is 39℃-40℃; the interface anchoring material is maleic anhydride; the emulsifier is a Span series emulsifier and a Tween series emulsifier (e.g., Span 80 and Tween 80), and they are mixed in equal proportions; the nanomaterial is one of multi-walled carbon nanotubes, carboxymethyl carbon nanotubes, and silicon carbide nanowires.

[0031] The aforementioned hydrated salt phase change microcapsules utilize an emulsifier to reduce the oil-water interfacial energy. The oil phase is the continuous phase, and the water phase is the discontinuous phase, forming a stable water-in-oil emulsion. Interfacial polymerization is employed to deposit nanomaterials at the oil-water interface, causing the shell-forming monomers to polymerize at the interface and form an outer shell encapsulating the core water phase. The preparation of a hydrated salt phase change microcapsule for power batteries disclosed in this invention includes the following steps: S1. Aqueous phase preparation: Mix disodium hydrogen phosphate dodecahydrate with deionized water and heat and stir above the phase transition temperature until fully dissolved; then add maleic anhydride and heat and stir until dissolved, then add emulsifier and stir evenly to obtain the aqueous phase solution; wherein, the heating temperature is 50℃, the stirring speed is 600-1000 rpm, and the stirring time is 30 min. The added emulsifier can be Tween 80.

[0032] S2. Oil Phase Preparation: Using n-hexadecane as the continuous phase solvent, add nanomaterials, mix thoroughly by stirring and ultrasonication, then add an emulsifier and stir until homogeneous to obtain the oil phase suspension. The added nanomaterials should be 0.3-1.2 wt% of the solvent mass. The total stirring time is 20 min at a stirring speed of 800-1000 rpm, and the ultrasonication time is 10 min. Span 80 can be used as the emulsifier.

[0033] S3. Emulsion Preparation: The aqueous phase solution prepared in S1 is added dropwise to the oil phase suspension prepared in S2. Under the action of shearing force and stirring (using a high-speed shearing machine and a stirring table), emulsification is carried out at a temperature above the phase transformation melting point to form a uniform and stable water-in-oil W / O type emulsion. The temperature for dropping, shearing and stirring is maintained at 50℃, the shearing speed is 12000-16000 rpm, the shearing time is 10 min, the stirring speed is 1000 rpm, and the stirring time is 20 min.

[0034] S4. Microcapsule Preparation: The emulsion prepared in S3 was heated to the reaction temperature, followed by the addition of 2',2-azobisisobutyronitrile (2',2'-azobisisobutyronitrile) and dropwise addition of methyl methacrylate (Methyl methacrylate). Hexadecane was then added to replenish the oil phase environment. After heating, stirring, centrifugation, washing, and drying, hydrated salt phase change microcapsule powder was obtained. The reaction temperature was 70-80℃, the reaction time was 5-6 h, the stirring speed was 600 rpm, and cyclohexane and deionized water were used for washing. Drying was carried out at room temperature.

[0035] This invention discloses a liquid-cooled thermal management method for hydrated salt phase change microcapsules used in power batteries. Liquid cooling pipes are laid interspersed between battery packs. Then, the hydrated salt phase change microcapsules are mixed with heat transfer oil to form a suspension. A peristaltic pump is used to circulate the suspension in the liquid cooling pipes. Temperature control and heat dissipation of the battery pack are achieved through the phase change heat absorption of the hydrated salt phase change microcapsules.

[0036] The heat transfer oil has a thermal conductivity of 0.458 W / (m·K) and a dynamic viscosity of 30.16 mm. 2 / s, density is 0.868g / cm³ 3 The hydrated salt microcapsules are added at a mass ratio of 1-5 wt%, and the mixture is stirred (at 1000 rpm for 30 min), sonicated (for 10 min), and then stirred at the same speed for another 30 min to ensure uniform dispersion of the hydrated salt microcapsules in the heat transfer oil. The heat transfer oil can be L-QB300 heat transfer oil, and the selected power battery is a 4680 battery manufactured by Panasonic for Tesla Model Y vehicles, assembled in series.

[0037] Furthermore, the liquid cooling pipeline is laid out in a serpentine pattern. The peristaltic pump pumps the suspension into the pipeline from the cold end. The hydrated salt in the hydrated salt microcapsules undergoes a phase change and melts to absorb heat through heat transfer from the battery pack, thereby controlling the temperature of the battery pack. Then, it flows back to the cold end to cool and undergo a phase change and solidify. The flow rate of the peristaltic pump is 1-2 cm / s.

[0038] The specific preparation process of microcapsules is as follows: S1. Aqueous phase preparation: Mix disodium hydrogen phosphate dodecahydrate with a small amount of deionized water and heat and stir at 50°C until fully dissolved. Add maleic anhydride and heat and stir until dissolved. Add Tween 80 and stir for 30 minutes. The mass ratio of disodium hydrogen phosphate dodecahydrate to maleic anhydride and emulsifier is 20:1-2:1-2.

[0039] S2. Oil phase preparation: Using 50 ml of n-hexadecane as the continuous phase solvent, add nanomaterials at a certain mass ratio of solvent, the amount of which is 0.3-1.2 wt% of solvent. Mix evenly by stirring for 10 min and sonicating for 10 min. Add Span 80 and stir for 10 min. The mass-volume ratio of the emulsifier to n-hexadecane is 100:0.5-1.5.

[0040] S3. Emulsion Preparation: The aqueous solution obtained in S1 is added dropwise to the oil suspension prepared in S2 under stirring at 50°C. The mixture is sheared for 5 minutes using a high-speed shear press at 12000-16000 rpm / min. Then, it is stirred for 20 minutes at 1000 rpm / min at 50°C. Finally, it is emulsified again using a shear press for 5 minutes to form a homogeneous and stable water-in-oil (W / O) emulsion. The mass ratio of the aqueous solution to the oil solution is 1:1-3.

[0041] S4. Microcapsule Preparation: The emulsion obtained in S3 was heated to 70℃, then 2',2-azobisisobutyronitrile was added, followed by the dropwise addition of methyl methacrylate. Hexadecane was then added to replenish the oil phase environment. The mixture was stirred at 70℃ and 600 rpm / min for 5 hours. After the reaction, the solution was centrifuged, washed with cyclohexane, dried, washed with deionized water, and dried again to obtain disodium hydrogen phosphate dodecahydrate phase change microcapsule powder. The mass ratio of the emulsion obtained in S3, 2',2-azobisisobutyronitrile, methyl methacrylate, and hexadecane was 500-550:0.5-1.5:80-120:450-550.

[0042] The preparation process of the liquid-cooled suspension is as follows: Phase change microcapsule powder is mixed with heat transfer oil, with the mass ratio of microcapsules being 1-5 wt%. The suspension is stirred at 1000 rpm / min for 30 min, ultrasonically dispersed for 10 min, and stirred again at the same speed for 30 min to obtain a liquid-cooled suspension with uniform texture.

[0043] The process of building a liquid cooling circulation system for battery thermal management: The liquid cooling pipes are laid in a serpentine pattern between the battery packs. The suspension is placed in the cold end container, and a peristaltic pump is used to pump the suspension into the pipes at a speed of 1-2 cm / s. Finally, the suspension flows back to the cold end container for cooling.

[0044] The present invention will be further described below with reference to specific embodiments.

[0045] Example 1 The specific synthesis process of a phase change microcapsule of disodium hydrogen phosphate dodecahydrate is as follows: S1. Aqueous phase preparation: Mix 10g of disodium hydrogen phosphate dodecahydrate with 5ml of deionized water and heat and stir at 50℃ until fully dissolved. Add 0.5g of maleic anhydride and heat and stir until dissolved. Add 0.5g of Tween 80 and stir at 800rpm / min for 30min.

[0046] S2. Oil phase preparation: Measure 50 ml of n-hexadecane, add 0.6 wt% of n-hexadecane mass of multi-walled carbon nanotubes (or 0.6 wt% carboxylated carbon nanotubes or 0.6 wt% silicon carbide nanowires or 0.3 wt% silicon carbide nanowires), pre-disperse by stirring at 1000 rpm for 10 min, sonicate for 10 min to ensure uniform dispersion in the oil phase, add 0.5 g of Span 80 and stir at the same speed for 10 min.

[0047] S3. Emulsion preparation: The aqueous solution obtained in S1 is added dropwise to the oil suspension prepared in S2 under stirring at 50°C. The mixture is sheared at 12,000 rpm for 5 minutes using a high-speed shearing machine. Then, it is stirred at 1,000 rpm for 20 minutes at 50°C using a stirring table. Finally, it is emulsified again at the same speed using a shearing machine for 5 minutes to form a uniform and stable water-in-oil W / O type emulsion.

[0048] S4. Microcapsule Preparation: The emulsion obtained in S3 was transferred to a round-bottom flask and heated to 70°C while stirring at 600 rpm. Then, 0.1 g of 2',2-azobisisobutyronitrile was added, followed by the slow addition of 10 g of methyl methacrylate. An additional 50 ml of n-hexadecane was added to replenish the oil phase. The reaction was carried out in a 70°C water bath with stirring at 600 rpm for 5 hours. After the reaction, the solution was centrifuged, leaving a precipitate. This precipitate was washed multiple times with cyclohexane, dried, washed with deionized water, and dried again to obtain disodium hydrogen phosphate dodecahydrate phase change microcapsule powder. The macroscopic morphology of phase change microcapsules prepared from different nanomaterials is shown below. Figure 1 As shown, its phase change properties and latent heat of phase change are as follows: Figure 2 The corresponding curves are shown in the figure. The results show that the microcapsules with different nanomaterials were all fine powder samples. After differential scanning calorimetry analysis, it was found that the microcapsules with 0.6 wt% and 0.3 wt% silicon carbide nanowires had relatively high latent heat of phase transition, among which the microcapsules with 0.3 wt% silicon carbide nanowires had the highest latent heat of phase transition.

[0049] Comparative Example 1 The preparation process of disodium hydrogen phosphate dodecahydrate phase change microcapsules is as follows: S1. Aqueous phase preparation: Mix 10g of disodium hydrogen phosphate dodecahydrate with 5ml of deionized water and heat and stir at 50℃ until fully dissolved. Add 0.5g of maleic anhydride and heat and stir until dissolved. Add 0.5g of Tween 80 and stir at 800rpm for 30min.

[0050] S2. Oil phase preparation: Measure 50 ml of n-hexadecane, add 0.5 g of Span 80, and stir continuously at 1000 rpm for 30 min.

[0051] S3. Emulsion preparation: The aqueous solution obtained in S1 is added dropwise to the oil suspension prepared in S2 under stirring at 50°C. The mixture is sheared at 12,000 rpm for 5 minutes using a high-speed shearing machine. Then, it is stirred at 1,000 rpm for 20 minutes at 50°C using a stirring table. Finally, it is emulsified again at the same speed using a shearing machine for 5 minutes to form a uniform and stable water-in-oil W / O type emulsion.

[0052] S4. Microcapsule preparation: The emulsion obtained in S3 was transferred to a round-bottom flask and heated to 70°C while stirring at 600 rpm / min. Then, 0.1 g of 2',2-azobisisobutyronitrile was added, and 10 g of methyl methacrylate was slowly added dropwise. An additional 50 ml of n-hexadecane was added to replenish the oil phase environment. The reaction was carried out in a water bath at 70°C with stirring at 600 rpm for 5 h. After the reaction was completed, the solution was centrifuged, leaving a precipitate. The precipitate was washed several times with cyclohexane, dried, washed with deionized water, and dried to obtain disodium hydrogen phosphate dodecahydrate phase change microcapsule powder.

[0053] Its macroscopic morphology is as follows Figure 1 As shown without any additional additions, its microstructure is as follows: Figure 2 As shown in the figure without additives, its morphology is an aggregated sphere with fluidity; its phase change properties and latent heat of phase change are as follows: Figure 3 The corresponding curves are shown in the table below. The thermal performance data of the microcapsules after differential scanning calorimetry analysis, after adding various nanomaterials, are shown in Table 1.

[0054] Table 1. Thermal performance data of microcapsules with various nanomaterials added.

[0055] Among them, T m It is the melting point, that is, the temperature at which a phase change material transforms from a solid to a liquid; ΔH m It is the enthalpy of fusion, which is the energy absorbed per unit mass of a phase change material as it transforms from a solid to a liquid; T c It is the freezing point, that is, the temperature at which a phase change material transforms from a liquid to a solid; ΔH c Enthalpy of solidification is the energy released when a unit mass of phase change material changes from liquid to solid. Table 1 shows that microcapsules without any added nanomaterials have relatively low latent heat of phase change, while microcapsules with added silicon carbide nanowires have higher latent heat, with the highest latent heat of phase change observed when the added concentration is 0.3 wt%.

[0056] A conceptual diagram of the phase change microcapsule coupled liquid cooling battery thermal management method prepared in this invention is shown below. Figure 4As shown, a peristaltic pump drives the microcapsules to circulate in the liquid-cooled pipes between the battery packs, and the charging and discharging equipment discharges and charges the 4680 battery packs; an infrared camera photographs and records the temperature of the battery packs. Actual battery thermal management applications are as follows... Figure 5 As shown.

[0057] Figure 6 and Figure 7 The figures show the thermal management temperature control effects achieved during discharge and charging. The results show that, under both discharge and charging conditions, due to the presence of microcapsules in the suspension, the temperature control effect of the suspension is more significant compared to pure thermal oil cooling. The temperature rise trend of the battery pack is significantly weakened, and the temperature difference between the two methods increases significantly with the extension of charging and discharging time. This indicates that the thermal management method of phase change microcapsules and thermal oil composite liquid cooling has a greater advantage in temperature control than traditional heat dissipation.

[0058] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A hydrated salt phase change microcapsule for use in a power cell, characterized by: The hydration salt is encapsulated by using the hydration salt as a core material, adding an interface anchoring material, using methyl methacrylate as a shell-forming monomer, adding an emulsifier and a nano material, and adopting an interfacial polymerization method to polymerize a poly methyl methacrylate organic shell layer.

2. The hydrated salt phase change microcapsule of claim 1, wherein: The hydration salt is sodium phosphate dibasic dodecahydrate, the phase transition melting point of the hydration salt is 39-40 DEG C, the interface anchoring material is maleic anhydride, the emulsifier is a Span series emulsifier and a Tween series emulsifier, and the nano material is one of a multi-walled carbon nanotube, a carboxymethyl carbon nanotube and a silicon carbide nanowire.

3. A method of producing the phase change microcapsules of hydrated salt for power cells according to claim 2, characterized in that: The method comprises the following steps: S1, water phase preparation: sodium phosphate dibasic dodecahydrate and deionized water are mixed, heated and stirred above the phase transition temperature until fully dissolved, maleic anhydride is added and heated and stirred until dissolved, and an emulsifier is added and stirred until uniform, thereby obtaining an aqueous solution; S2, oil phase preparation: n-hexadecane is used as a continuous phase solvent, a nano material is added, stirred and ultrasonically mixed until uniform, and an emulsifier is added and stirred until uniform, thereby obtaining an oil phase suspension; S3, emulsion preparation: the aqueous solution prepared in S1 is added dropwise into the oil phase suspension prepared in S2, emulsified under the action of shearing force and stirring at a temperature above the phase transition melting point, and a uniform and stable water-in-oil (W / O) emulsion is formed; S4, microcapsule preparation: the emulsion prepared in S3 is heated to a reaction temperature, 2'2-azobis isobutyronitrile is added, methyl methacrylate is added dropwise, n-hexadecane is additionally added to supplement an oil phase environment, and hydration salt phase transition microcapsules are obtained through heating, stirring, centrifugation, washing and drying.

4. The method of claim 3, wherein the method further comprises: In step S1, the heating temperature is 50 DEG C, the stirring speed is 600-1000 rpm, and the stirring time is 30 min.

5. The method of claim 3, wherein the method further comprises: In step S2, the added nano material has a mass of 0.3-1.2 wt% of the solvent, the stirring time is 20 min, the stirring speed is 800-1000 rpm, and the ultrasonic time is 10 min.

6. The method of claim 3, wherein the method further comprises: In step S3, the dropwise adding, shearing and stirring temperatures are all maintained at 50 DEG C, the shearing speed is 12000-16000 rpm, the shearing time is 10 min, the stirring speed is 1000 rpm, and the stirring time is 20 min.

7. The method of claim 3, wherein the method further comprises: In step S4, the reaction temperature is 70-80 DEG C, the reaction time is 5-6 h, the stirring speed is 600 rpm, the reagents for washing are cyclohexane and deionized water, and drying is performed at room temperature.

8. A liquid cooling thermal management method for power batteries using the hydrated salt phase change microcapsules prepared by the method of any one of claims 3-7, characterized in that: The liquid cooling pipe is arranged in a serpentine shape, the suspension is pumped into the pipe from the cold end by the peristaltic pump, the hydration salt in the hydration salt microcapsules is phase transitioned and melted to absorb heat through heat transfer of the battery pack, the battery pack is temperature-controlled, and then the suspension flows back to the cold end to be phase transitioned and solidified, and the flow rate of the peristaltic pump is 1-2 cm / s.

9. The liquid-cooled thermal management approach of hydrated salt phase change microcapsules for power batteries according to claim 8, characterized in that: The thermal conductivity of the heat conducting oil is 0.458 W / (m·K), the dynamic viscosity is 30.16 mm 2 / s, and the density is 0.868 g / cm 3 The mass ratio of the added hydrated salt microcapsules is 1-5 wt%, and the hydrated salt microcapsules are uniformly dispersed in the heat conducting oil by stirring and ultrasonic treatment.

10. The liquid-cooled thermal management approach of hydrated salt phase change microcapsules for power batteries of claim 8, wherein: ​

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