High-temperature-resistant electrolytic capacitor and preparation method thereof

Abstract

The invention relates to the technical field of power electronic components, and discloses a high-temperature-resistant electrolytic capacitor which comprises the following components in parts by weight: 80-90 parts of a graphene or carbon nanotube coating used for preparing an electrolytic capacitor shell; the invention further provides a preparation method of the high-temperature-resistant electrolytic capacitor, and the preparation method comprises the following steps: heat conduction optimization design: simulating a temperature field of the electrolytic capacitor through an unsteady-state heat conduction equation, optimizing a heat dissipation path of the electrolytic capacitor, and improving the heat dissipation performance of the electrolytic capacitor; and heat can be uniformly conducted to an external heat dissipation device. By introducing the microencapsulated phase change material, the graphene coating and the accurate temperature sensor array and optimizing heat dissipation design, efficient heat dissipation, temperature balance and long-term stability of the electrolytic capacitor in a high-temperature environment are achieved, the working performance of the electrolytic capacitor is remarkably improved, and the service life of the electrolytic capacitor is remarkably prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic components, and particularly to a high-temperature resistant electrolytic capacitor and a preparation method thereof. Background Art

[0002] In the field of modern technology, especially in industries such as aerospace, new energy vehicles, and industrial automation equipment, the demand for capacitors is increasing day by day, especially in high-temperature environments. As a common electronic component, the main functions of electrolytic capacitors are to provide power filtering, signal coupling, and energy storage.

[0003] In the prior art, although the heat dissipation and high-temperature resistance performance of electrolytic capacitors have been improved, most technologies still mainly rely on external heat dissipation materials or thickening the outer shell to enhance the heat resistance of the capacitors. Some technologies adopt improved electrolyte formulations to improve the temperature resistance performance of the capacitors by changing the components of electrolytic salts and solvents. These improvement measures have extended the service life of the capacitors to a certain extent, especially in environments with relatively stable temperatures.

[0004] However, there are still some deficiencies in the prior art. When traditional electrolytic capacitors face high-temperature environments, problems such as temperature accumulation and local overheating are still likely to occur. Even when using higher-temperature-resistant electrolytes, the problems of uneven heat dissipation and inability to dissipate heat in a timely manner have not been effectively solved. More importantly, the prior art usually relies on a single heat dissipation method and fails to comprehensively consider the synergistic effects of multiple factors such as electrolytes, heat sinks, and phase change materials. In addition, the temperature monitoring methods of the prior art are also relatively single, usually using basic temperature sensors, and it is difficult to achieve comprehensive monitoring of the temperatures of key regions inside the capacitors. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a high-temperature resistant electrolytic capacitor and a preparation method thereof, which solve the problems of uneven heat dissipation and performance degradation caused by temperature accumulation of electrolytic capacitors in high-temperature environments.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A high-temperature resistant electrolytic capacitor, the electrolytic capacitor comprising the following components in parts by weight: Graphene or carbon nanotube coating: 80 - 90 parts, used to prepare the outer shell of the electrolytic capacitor. Graphene and carbon nanotubes have excellent thermal conductivity and can quickly conduct heat from the inside of the capacitor to the outside. Their excellent thermal conductivity enables the outer shell of the electrolytic capacitor to effectively reduce temperature non-uniformity and prevent local overheating when bearing external high temperatures. At the same time, the two-dimensional structure of graphene enables heat energy to quickly diffuse over the entire surface, reducing the risk of heat accumulation. Through this coating design, the heat dissipation efficiency of the electrolytic capacitor has been significantly improved, and its service life has been extended; Epoxy resin: 10 - 20 parts, used to form a composite material with graphene or carbon nanotubes. When the epoxy resin is compounded with graphene or carbon nanotubes, it can form a strong network structure, which enables the composite material to maintain high mechanical strength and thermal stability in high-temperature environments. The chemical stability of the epoxy resin itself also enhances the high-temperature resistance of the capacitor housing, avoiding damage to the coating from external heat sources; Aluminum alloy or copper: 90 - 95 parts, used to make heat sinks and heat pipes. Copper has high strength and corrosion resistance, so it is suitable for long-term use in high-temperature environments. Aluminum alloy, on the other hand, has a lighter mass and better cost-effectiveness, making it suitable for the heat dissipation requirements of most conventional capacitors. Combining these two materials can optimize the heat dissipation system of the electrolytic capacitor, enabling it to operate stably in high-temperature environments; Na2SO4·10H2O, CaCl2·6H2O or stearic acid: 60 - 80 parts, used to make phase change materials, which are embedded in the electrolytic capacitor housing or heat sink. When the temperature rises, the crystal water of the hydrated salt in Na2SO4·10H2O will gradually be released during heating, absorbing a large amount of heat, thereby slowing down the temperature rise. The microencapsulation of the phase change material enables it to be evenly distributed in the electrolytic capacitor housing or heat sink, ensuring that the temperature inside the capacitor does not become locally too high and reducing material deformation and electrolyte leakage caused by thermal stress; Silica nanoparticles in the electrolyte: 15 - 30 parts, used for the preparation of the electrolyte. Silica nanoparticles have high thermal conductivity and surface activity, and can effectively interact with other components in the electrolyte to form a stronger stable structure. These nanoparticles can help the electrolyte conduct heat better at high temperatures, prevent heat from concentrating in local areas, and reduce failures of the electrolyte caused by thermal stress; Alcohol liquid: 5 - 10 parts, used to dissolve electrolytic salts and serve as the main solvent for the electrolyte. Alcohol solvents have low volatility and high solubility, and can remain stable at relatively high temperatures. In addition, the chemical stability of the alcohol liquid helps to improve the conductivity of the electrolyte at high temperatures, thereby improving the working efficiency of the electrolytic capacitor.

[0007] The present invention also provides a preparation method for a high-temperature resistant electrolytic capacitor, which includes the following steps: S1. Thermal conduction optimization design: Simulate the temperature field of the electrolytic capacitor through the unsteady heat conduction equation, optimize the heat dissipation path of the electrolytic capacitor, and ensure that heat is evenly conducted to the external heat dissipation device; S2. Phase change material selection and microencapsulation: Select inorganic hydrates or fatty acid-based phase change materials, and use microencapsulation technology to evenly distribute the phase change material in the electrolytic capacitor housing coating or heat sink to provide an efficient heat regulation function; S3. Electrolyte Preparation and Additive Addition: Prepare the electrolyte and add silicon dioxide nanoparticles to improve the high-temperature resistance and thermal stability of the electrolyte, ensuring the reliable operation of the capacitor in a high-temperature environment; S4. Heat Dissipation System Design: Design a heat sink and heat pipe system. Use high-thermal-conductivity metal materials to make the heat sink and combine heat pipe technology to improve the heat dissipation efficiency, ensuring uniform distribution of the internal temperature of the electrolytic capacitor; S5. Assembly and Testing: Assemble the electrolytic capacitor and conduct performance tests under high-temperature conditions to verify its heat dissipation performance and long-term stability.

[0008] Preferably, the optimized heat conduction design includes: Through numerical simulation and finite element analysis, calculate the heat flow path inside the electrolytic capacitor to determine the distribution of the temperature field. The FEM simulation takes into account all heat sources in the electrolytic capacitor (such as the heating of the electrolyte, the electrode temperature inside the capacitor, etc.), and through grid calculation, the influence of these heat sources is transmitted to each part of the capacitor. The calculation results show that the distribution of the temperature field determines the diffusion speed and uniformity of heat, thereby affecting the overall performance of the electrolytic capacitor; Based on the calculation of the thermal diffusivity, optimize the material selection of the electrolytic capacitor to ensure the high thermal conductivity of the shell, heat sink, and heat pipe. The thermal diffusivity is an important parameter reflecting the heat conduction characteristics of materials. The higher the thermal diffusivity, the faster the heat diffuses in the material. The formula for thermal diffusivity is: where k is the thermal conductivity of the material, ρ is the density of the material, and c is the specific heat capacity.

[0009] By selecting graphene or carbon nanotube coatings, the heat dissipation system of the electrolytic capacitor can more effectively transfer the internally generated heat to the external heat dissipation system, thereby improving the thermal management performance of the capacitor; Use the heat flux density optimization algorithm to adjust the layout of the heat sink to ensure that the heat inside the capacitor can be quickly and effectively conducted to the external heat dissipation device. The heat flux density q is the heat flow rate per unit area and can be calculated by the heat flux density formula: where k is the thermal conductivity of the material; is the temperature gradient, representing the temperature change per unit length; q is the heat flux density. The role of the heat sink is to accelerate heat transfer by increasing the contact area. The optimized layout can make the most of the surface area of the capacitor to quickly direct heat to the heat dissipation system. In addition, by optimizing the heat flow path, the formation of hot spots inside the capacitor can be avoided, ensuring uniform heat distribution and preventing leakage or other failures caused by local overheating of the electrolyte.

[0010] Preferably, the selection and microencapsulation of the phase change material include: Select an inorganic hydrate or a fatty acid material as the phase change material, and perform microencapsulation on the phase change material to ensure that it absorbs 30 - 40 J / g of heat in the temperature range of 150 - 200 °C and prevent leakage. The particle size range of the microcapsules is 50 - 500 μm. These phase change materials exhibit good heat regulation ability in the working temperature range of 150 °C to 200 °C, and can effectively slow down the increase in the internal temperature of the electrolytic capacitor. The core of the microencapsulation technology is to wrap the phase change material in a polymer or inorganic material to form a granular structure. The purpose of this is to ensure the stable existence of the phase change material in a high-temperature environment and prevent leakage; Uniformly coat or embed the microencapsulated phase change material in the outer shell coating or heat sink of the electrolytic capacitor, and achieve stable temperature regulation through its phase change characteristics. The heat sink and heat pipe system of the electrolytic capacitor can quickly guide the internal heat to the external heat dissipation device, while the phase change material absorbs the excess heat during this process to prevent the temperature from rising sharply. The combination of the two can ensure the stable operation of the capacitor in a high-temperature environment.

[0011] Preferably, the preparation of the electrolyte and the addition of additives include: Prepare the basic solvent of the electrolyte, mainly including carbonate solvents, dissolve the electrolytic salt to ensure good conductivity. Carbonate solvents have a low vapor pressure and good chemical stability, and can effectively reduce the volatilization of the electrolyte at high temperatures. They have good solubility and can dissolve the electrolytic salt into an ionic state to promote the conductivity of the electrolyte. At high temperatures, carbonate solvents can maintain a high conductivity while avoiding electrical failure caused by overheating or volatilization of the electrolyte; Add silicon dioxide nanoparticles with a particle size range of 10 - 100 nm and disperse them evenly. Silicon dioxide nanoparticles in this particle size range have a large specific surface area and can effectively interact with other components in the electrolyte, enhancing the chemical stability and thermal stability of the electrolyte. When the temperature of the electrolyte is too high, the silicon dioxide nanoparticles help to evenly disperse the heat, avoid excessive heat accumulation, and improve the thermal conductivity of the electrolyte; Conduct a high-temperature durability test on the prepared electrolyte to ensure that it does not volatilize or degrade in an environment of 150 - 200 °C. Since the electrolyte contains silicon dioxide nanoparticles, it can improve the chemical stability of the electrolyte at high temperatures, prevent the decomposition or chemical reaction of the electrolyte at high temperatures. In addition, the silicon dioxide nanoparticles can also enhance the thermal stability of the electrolyte, enabling it to better maintain the structure and performance of the electrolyte in a high-temperature environment. Through the test in this temperature range, ensure the stability and long-term use reliability of the electrolyte, and avoid the performance decline of the electrolytic capacitor caused by electrolyte degradation.

[0012] Preferably, the heat sink design includes: Design the shape and size of the heat sink, make the heat sink using copper or aluminum alloy, and calculate its surface area and heat dissipation efficiency. The heat sink is made of copper or aluminum alloy materials, which have excellent thermal conductivity and can efficiently conduct the heat generated inside the electrolytic capacitor to the external heat dissipation system. Copper and aluminum alloy have high thermal conductivities of 400 W / m·K and 200 W / m·K respectively, so they can effectively improve the heat dissipation efficiency and reduce the temperature accumulation inside the electrolytic capacitor; Through heat flow optimization and adjustment of the heat sink position, ensure that heat can be quickly transferred from inside the electrolytic capacitor to the external heat dissipation system, avoiding excessive local temperature inside the capacitor. The heat flow optimization algorithm calculates the heat transfer path between the heat source inside the capacitor and the radiator, and by changing the position and layout of the heat sink, the heat can be effectively diffused from inside the electrolytic capacitor to the external heat dissipation system. Inside the electrolytic capacitor, heat is usually concentrated around the electrolyte or electrode materials, so the heat sink should be close to these heat source areas to absorb and conduct heat more effectively; through heat flow optimization design, the accumulation of heat inside the electrolytic capacitor can be reduced, avoiding excessive local temperature.

[0013] Preferably, the heat pipe system design includes: Quickly conduct heat from inside the electrolytic capacitor to the external heat dissipation device through its evaporation and condensation process. The filling liquid of the heat pipe has a low evaporation temperature to ensure its efficient heat transfer at high temperatures. The working principle of the heat pipe system is based on the evaporation and condensation effect, and this process efficiently conducts heat. The evaporation end of the heat pipe absorbs the heat generated inside the electrolytic capacitor, and the liquid evaporates into gas at the evaporation end. The gas moves through the heat pipe towards the condensation end. At the condensation end, the gas releases heat and turns into liquid, and the liquid then returns to the evaporation end through the capillary structure of the heat pipe to continue absorbing heat. The design of the heat pipe realizes the rapid transfer of heat by continuously cycling this process. The liquid with a low evaporation temperature can start to evaporate at a relatively low temperature, thus achieving efficient heat transfer. For example, water as the filling liquid in the heat pipe has a low evaporation temperature (100 °C), so it can work efficiently in a high temperature environment of 150 °C to 200 °C.

[0014] Preferably, the assembly and testing include: Assemble the shell, phase change material, electrolyte, heat sink, and heat pipe system into an electrolytic capacitor, ensuring that there is no liquid leakage at all contact points and the shell has good sealing. As the temperature rises, the electrolyte will increase its internal pressure due to evaporation. If the sealing is not tight, it may lead to electrolyte leakage, short circuit, or failure. Therefore, by ensuring no liquid leakage at all contact points and the sealing of the shell, the above problems can be avoided, ensuring the reliability of the electrolytic capacitor in a high temperature working environment; The assembled electrolytic capacitor is subjected to high-temperature performance tests. The test temperatures are 150°C, 180°C, and 200°C, and the continuous working time is 1000 hours. The capacitance change, leakage current, and loss tangent of the capacitor are monitored. During the operation of the electrolytic capacitor, the electrolyte will volatilize to a certain extent over time and with the increase in temperature, resulting in a change in capacitance. Therefore, monitoring the change in capacitance can intuitively reflect the performance degradation of the electrolytic capacitor. The electrolyte may evaporate or degrade at high temperatures, leading to an increase in leakage current. An increase in leakage current means that the insulation performance of the electrolytic capacitor deteriorates, which may affect the working efficiency and lifespan of the capacitor. By monitoring the change in leakage current, it is possible to effectively determine whether the insulation performance of the electrolytic capacitor meets the requirements. A higher loss tangent indicates that the loss of the electrolytic capacitor is larger, which may cause the temperature to be too high or the energy efficiency to decrease. Therefore, monitoring the change in loss tangent can help evaluate the working efficiency and stability of the electrolytic capacitor; Adjust the design according to the test results to ensure that the electrolytic capacitor can operate stably in a high-temperature environment and meet various performance requirements. The test results can reflect the actual performance of the electrolytic capacitor in a high-temperature working environment. If the capacitance drops too much, the leakage current increases, or the loss tangent is too high, these will all affect the working efficiency and lifespan of the capacitor. At this time, by adjusting the design, the performance of the electrolytic capacitor can be effectively improved.

[0015] Preferably, the high-temperature environment test includes: Conduct a long-term high-temperature cycle test to simulate the long-term operating performance of the electrolytic capacitor in a high-temperature environment. The high-temperature cycle test simulates the usage of the electrolytic capacitor in a long-term high-temperature environment. The main purpose is to evaluate the stability of the electrolytic capacitor under different temperature fluctuations; Regularly measure the capacitance, leakage current, and withstand voltage performance of the electrolytic capacitor to ensure that the electrolytic capacitor meets the high-temperature working requirements. The leakage current is a key indicator of the insulation performance of the electrolytic capacitor. In a high-temperature environment, the volatilization of the electrolyte or the degradation of the electrolyte may cause the insulation performance of the capacitor to decline, resulting in an increase in leakage current. By measuring the change in leakage current, the insulation performance of the electrolytic capacitor at high temperatures can be evaluated to ensure that it meets the safety requirements; Monitor the change in the internal temperature of the electrolytic capacitor during the test through an infrared thermal imager and a temperature sensor array to ensure that its temperature remains within a safe range.

[0016] Preferably, the temperature sensor is an array of multiple K-type thermocouples or multiple surface-mounted thermistors combined to form a temperature sensor array, ensuring that the operating temperature range of the electrolytic capacitor is > 250°C. K-type thermocouples are suitable for high-temperature ranges, with a maximum of up to 1300°C, and have high sensitivity, capable of providing accurate temperature measurement results. K-type thermocouples can help monitor the high-temperature areas inside and outside the electrolytic capacitor in real time, especially the temperature at the contact areas of the electrolyte, heat sink, and heat pipe. Their thermoelectric effect can convert the temperature difference into a voltage signal, thus achieving precise temperature measurement. Thermistors have higher sensitivity in lower temperature ranges and are therefore suitable for real-time monitoring of minute temperature difference changes, helping to understand the heat distribution in real time; The temperature sensor array is evenly distributed in the key heat source areas of the electrolytic capacitor, including the contact area between the electrolyte and the heat sink, the surface of the heat sink, and the positions of the outer shell and the heat pipe, ensuring that the temperature changes of each part of the electrolytic capacitor can be monitored in real time. By arranging temperature sensors in the contact area between the electrolyte and the heat sink, the temperature change of the electrolyte can be monitored in real time to ensure that it remains within a safe range and avoid damage to the electrolyte caused by overheating. By arranging temperature sensors on the surface of the heat sink and at the position of the heat pipe, the temperature change of the heat dissipation system can be monitored in real time to ensure that heat can be efficiently conducted and released, preventing uneven heat dissipation or overheating;

[0017] The present invention provides a high-temperature resistant electrolytic capacitor and its preparation method. It has the following beneficial effects: 1. By introducing microencapsulated phase change materials, the present invention effectively improves the heat regulation ability of the electrolytic capacitor, enabling it to absorb and release heat freely in high-temperature environments, avoiding the problems of volatilization or leakage of the electrolyte in traditional solutions, and thus significantly extending the service life of the capacitor.

[0018] 2. By adopting the composite technology of graphene coating and epoxy resin, the thermal conductivity of the outer shell of the electrolytic capacitor has been greatly improved. This innovative design can withstand higher temperature changes, reduce the impact of thermal expansion on the capacitor performance, and avoid the limitations of traditional materials that cannot adapt to high-temperature environments.

[0019] 3. The innovation of the temperature monitoring system in the present invention is the thermocouple, thermistor array, and infrared thermal imaging technology, which realizes real-time and accurate monitoring of the internal and external temperatures of the electrolytic capacitor, solves the problem that the temperature change of the previous electrolytic capacitor could not be grasped in time, and ensures the safe operation of each part under high-temperature conditions.

[0020] 4. Through the collaborative work of the copper heat sink and the heat pipe system, the electrolytic capacitor of the present invention can effectively dissipate heat and maintain temperature balance. Compared with traditional heat sinks, the problem is thus improved, and the long-term reliability of the capacitor in extreme temperature environments is enhanced. Description of the Drawings

[0021] Figure 1 This is the flowchart of the method of the present invention. Detailed implementation manners

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the specification of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0023] Please refer to the attached Figure 1 : Example 1: Preparation and testing of high-temperature electrolytic capacitors Steps and process parameters: Housing production: Aluminum alloy material is used, with a thickness of 2 mm. The surface of the housing is coated with a composite coating of graphene: (85 parts) and epoxy resin: (15 parts). The thickness of this coating is controlled at 1 μm to ensure good thermal conductivity and mechanical strength of the housing.

[0024] Phase change material preparation and microencapsulation: Na2SO4·10H2O is selected as the phase change material and mixed with the polymer in a ratio of 70 parts. Through microencapsulation treatment, the particle size range is controlled at 100 μm to form a stable microcapsule structure. Then, the microencapsulated phase change material is evenly coated on the inner side of the housing and the surface of the heat sink.

[0025] Electrolyte preparation: Carbonate solvents (such as DMC and EC) are selected and 70 parts are used to dissolve electrolytic salts (such as LiPF6) to ensure good conductivity. Silicon dioxide nanoparticles with a particle size of 30 nm are added to the electrolyte, and the addition amount is 25 parts. And isopropanol is added as a solvent with a ratio of 5 parts to ensure that the electrolyte will not volatilize or degrade at high temperatures.

[0026] Heat sink and heat pipe design: The heat sink uses copper material with a thickness of 0.5 mm, and the area is designed to be 20 cm 2 . The heat pipe system is configured to be made of copper and contains water as a liquid with a low evaporation temperature. The length of the heat pipe is 8 cm, and the heat dissipation efficiency reaches 90%.

[0027] Assembly: The housing, microencapsulated phase change material, electrolyte, heat sink and heat pipe system are assembled in sequence. Laser welding is used to ensure that all contact points are tightly sealed to avoid electrolyte leakage.

[0028] Test: The assembled electrolytic capacitor is placed in an environment of 150°C and subjected to a 1000-hour high-temperature cycling test. During the test, the capacitance change, leakage current, and loss tangent are monitored regularly. An infrared thermal imager is used to monitor the surface temperature of the electrolytic capacitor in real time to ensure that the temperature remains within a safe range.

[0029] Example 2: Preparation of a high-temperature electrolytic capacitor based on a graphene coating Steps and process parameters: Outer shell coating: Select an aluminum alloy outer shell with a thickness of 2 mm. Coat with a graphene coating (90 parts) and epoxy resin (10 parts). The coating thickness is controlled at 1.5 μm to ensure that the outer shell has excellent thermal conductivity and can withstand the thermal expansion stress at high temperatures.

[0030] Phase change material microencapsulation: Select CaCl2·6H2O as the phase change material, which is 60 parts. After being compounded with a polymer, it is microencapsulated to ensure a particle size of 80 μm. After microencapsulation, it is evenly coated on the surface of the heat sink and the inner side of the outer shell.

[0031] Electrolyte preparation: Use a carbonate solvent (DMC:EC = 70:30, which is 75 parts) to dissolve LiPF 6 electrolytic salt to ensure its conductivity. Add silicon dioxide nanoparticles (particle size 20 nm), with a quantity of 20 parts. Add isopropyl alcohol as a solvent, with a ratio of 5 parts. This electrolyte remains stable in an environment of 150°C - 200°C and effectively avoids electrolyte volatilization.

[0032] Heat dissipation system and heat pipe design: Adopt a copper heat sink with a thickness of 0.8 mm and an area of 25 cm 2 . The heat pipe selects ammonia water as the filling liquid, and the evaporation temperature is relatively low to ensure efficient heat transfer of the heat pipe at 200°C. The designed length of the heat pipe is 10 cm, and the thermal conductivity is 200 W / m·K.

[0033] Assembly and sealing: The outer shell is assembled after being sealed with the heat dissipation system, heat pipe, and electrolyte. Vacuum injection technology is used to ensure that the electrolyte does not leak and to ensure good contact between the outer shell and the internal components, avoiding any heat source leakage.

[0034] Test: The assembled electrolytic capacitor is placed in an environment of 180°C for a 1000-hour high-temperature test. The capacitance change, leakage current, and withstand voltage performance are monitored every 200 hours. A temperature sensor array is used for real-time temperature monitoring to ensure that the operating temperature of the electrolytic capacitor remains within a safe range.

[0035] Example 3: A high-temperature resistant electrolytic capacitor based on the combination of a copper heat sink and a heat pipe Steps and process parameters: Outer shell coating and material selection: Select an aluminum alloy outer shell with a thickness of 2.5 mm, and use a graphene coating (90 parts) and epoxy resin (10 parts), with a coating thickness of 1.2 μm. This coating design not only ensures good thermal conductivity but also increases the thermal expansion resistance of the outer shell.

[0036] Phase change material selection and treatment: Select stearic acid as the phase change material, with a quantity of 75 parts, and use microencapsulation technology for treatment, with the particle size controlled at 50 μm. The microencapsulated phase change material is evenly coated on the inner and outer sides of the heat sink and around the electrolyte, optimizing the heat regulation performance.

[0037] Electrolyte preparation: Use a carbonate solvent (DMC and EC in a ratio of 70:30, 80 parts) to dissolve LiBF 4 electrolytic salt to ensure good conductivity at high temperatures. Add silica nanoparticles (particle size 15 nm), with a quantity of 25 parts. In addition, add ethanol as a solvent to ensure that the electrolyte is stable and does not volatilize at high temperatures.

[0038] Heat sink and heat pipe design: Use a copper heat sink with a thickness of 1 mm and an area of 30 cm 2 . The heat pipe is filled with methanol, which has a low evaporation temperature (-5 °C), enabling the heat pipe to efficiently transfer heat in an environment of 150 °C to 200 °C. The length of the heat pipe is 12 cm to ensure that heat can be quickly conducted from the inside of the electrolytic capacitor to the outside.

[0039] Assembly and sealing: Inject the electrolyte into the electrolytic capacitor through a vacuum injection process to ensure no bubbles and avoid electrolyte leakage. The capacitor outer shell is sealed by laser welding technology to ensure good sealing.

[0040] Testing and verification: Place the assembled electrolytic capacitor in an environment of 200 °C for high-temperature testing. Every 200 hours, measure the capacitance, leakage current, and loss tangent of the capacitor respectively, and use an infrared thermal imager and temperature sensors to monitor the temperature change inside the capacitor.

[0041] Comparative example 1 (corresponding to Example 1): Do not use a graphene coating and only use a traditional aluminum outer shell Preparation process: Outer shell production: Use an aluminum alloy outer shell without special coating treatment, with a thickness of 2 mm, and do not perform graphene or carbon nanotube coating treatment.

[0042] Phase change material preparation: Use Na2SO4·10H2O, with a weight ratio of 70 parts, perform microencapsulation, with a particle size of 100 μm, and evenly distribute it on the surface of the heat sink.

[0043] Electrolyte preparation: A carbonate solvent (a mixture of DMC and EC, 70 parts by weight) is used to dissolve the LiPF6 electrolyte salt, and no silica nanoparticles are added.

[0044] Heat dissipation system design: A copper heat sink (thickness 0.5 mm, area 20 cm 2 ) is used, and the heat pipe is filled with water, with a length of 8 cm.

[0045] Assembly and sealing: The outer shell, phase change material, electrolyte, heat sink and heat pipe system are assembled and sealed by ordinary welding.

[0046] Testing method: A 1000-hour high-temperature cycle test is carried out in an environment of 150 °C to measure the capacitance, leakage current and loss tangent.

[0047] Comparative example 2 (corresponding to Example 2): Instead of using the microencapsulated phase change material, a common phase change material is directly added. Preparation process: Outer shell coating: An aluminum alloy outer shell with a thickness of 2 mm is used, and a graphene coating (90 parts) + epoxy resin (10 parts) is coated on the surface, with a thickness of 1.5 μm.

[0048] Phase change material: CaCl2·6H2O (60 parts) is used, but it is not microencapsulated and is directly filled into the heat sink without particle size optimization.

[0049] Electrolyte preparation: A carbonate solvent (75 parts) is used to dissolve the LiPF6 electrolyte salt, and silica nanoparticles (20 parts) are added.

[0050] Heat dissipation system: A copper heat sink with a thickness of 0.8 mm and an area of 25 cm 2 is used, and the heat pipe is filled with ammonia water, with a length of 10 cm.

[0051] Assembly and sealing: The outer shell is combined with the heat sink, and the electrolyte is sealed by vacuum injection.

[0052] Testing method: A 1000-hour high-temperature test is carried out in an environment of 180 °C to measure the capacitance change, leakage current and withstand voltage performance.

[0053] Comparative example 3 (corresponding to Example 3): The optimized heat sink layout is not used. Preparation process: Outer shell coating: An aluminum alloy outer shell with a thickness of 2.5 mm is used, and a graphene coating (90 parts) + epoxy resin (10 parts) is coated, with a thickness of 1.2 μm.

[0054] Phase change material: Stearic acid (75 parts) is selected and microencapsulated, with a particle size of 50 μm, and is evenly coated on the inner and outer sides of the heat sink.

[0055] Electrolyte Preparation: Use a carbonate solvent (80 parts) to dissolve the LiBF4 electrolytic salt, and add silicon dioxide nanoparticles (25 parts).

[0056] Heat Dissipation System: Use a copper heat sink (with a thickness of 1 mm and an area of 30 cm 2 ), and the heat pipe is filled with methanol and has a length of 12 cm.

[0057] Unoptimized Heat Sink Layout: The position of the heat sink has not been adjusted by a heat flow optimization algorithm and is directly fixed on one side of the housing without adjusting the layout according to the heat flow path.

[0058] Assembly and Sealing: The housing and the electrolyte are sealed through a vacuum injection process.

[0059] Testing Method: Conduct a 1000-hour high-temperature test at 200 °C, measure the capacitance, leakage current, and loss tangent of the capacitor, and use an infrared thermal imager for temperature monitoring.

[0060] Experiment: Experimental Procedures: Experimental Preparation: Prepare six groups of electrolytic capacitors, including three groups of examples and three groups of comparative examples. For each group of electrolytic capacitors, prepare components such as the housing coating, electrolyte, and heat dissipation system according to the technical solutions involved. Ensure that each group of electrolytic capacitors is assembled before the high-temperature test and ensure that the electrolyte does not leak.

[0061] Set the Ambient Temperature: Place each group of electrolytic capacitors in environments of 150 °C, 180 °C, and 200 °C, and use a temperature control box to ensure accurate and stable temperature.

[0062] High-Temperature Cycling Test: Start the high-temperature cycling test. Each group of electrolytic capacitors operates at the set temperature for 1000 hours. Measure the capacitance, leakage current, and loss tangent every 200 hours.

[0063] Temperature Monitoring: Use an infrared thermal imager and a temperature sensor array to monitor the temperature changes of the electrolytic capacitors, especially in key areas such as the electrolyte, heat sink, and heat pipe.

[0064] Performance Detection: Regularly record and analyze the capacitance changes, leakage current, and loss tangent values during the test to evaluate the performance changes of the electrolytic capacitors in a high-temperature environment.

[0065] Experimental Materials: Electrolytic Capacitor Housing: Use an aluminum alloy housing with a thickness of 2 mm - 2.5 mm, and the surface is coated with a graphene coating and an epoxy resin composite coating.

[0066] Phase Change Material: Select Na2SO4·10H2O, CaCl2·6H2O, or stearic acid, which is microencapsulated with a particle size of 50 - 100 μm.

[0067] Electrolyte: Use carbonate solvents (such as DMC and EC), LiPF6 electrolytic salt, add silicon dioxide nanoparticles (particle size 10 - 30nm), and isopropyl alcohol as a solvent.

[0068] Heat dissipation system: Use a copper heat sink (thickness 0.5mm - 1mm), and the heat pipe is configured to be filled with water or other low evaporation temperature liquids (such as methanol).

[0069] Temperature sensor array: Includes K - type thermocouples and thermistors for real - time temperature monitoring.

[0070] Complete experimental process: Assembly and sealing: Assemble the outer shell, phase - change material, electrolyte, heat sink, and heat pipe system into an electrolytic capacitor. Ensure that the electrolyte has no bubbles and is tightly sealed through a vacuum injection process.

[0071] Temperature and environment monitoring: Place the electrolytic capacitor in a temperature - controlled chamber, ensure that the test environment temperatures are 150°C, 180°C, and 200°C, and use an infrared thermal imager and temperature sensor array to monitor the temperature of each key area of the electrolytic capacitor in real - time.

[0072] Performance testing: Every 200 hours, measure the capacitance, leakage current, and loss tangent, and record the temperature change. Regularly evaluate the working state of the electrolytic capacitor during the test to ensure that the capacitance decay and leakage current are within a reasonable range.

[0073] Data recording and analysis: Record the performance changes of each group of electrolytic capacitors and conduct comparative analysis to ensure that all experimental data fully reflects the effect differences between different examples and comparative examples.

[0074] Comparison of high - temperature cycle test results In this experiment, by comparing the performance of the example and the comparative example in a high - temperature environment, the superiority of the technical solution of the present invention is verified. The increases in capacitance change, leakage current, and loss tangent of the high - temperature electrolytic capacitor in the example during the high - temperature cycle test are all lower than those of the comparative example. This indicates that the innovative design of the present invention, especially the application of the micro - encapsulated phase - change material and the optimization of the heat dissipation system, improves the thermal management ability of the electrolytic capacitor.

[0075] Specifically, the graphene coating and microencapsulated phase change materials in the embodiments not only improve the heat dissipation efficiency of the electrolytic capacitor, but also effectively regulate the internal temperature and prevent local overheating. This effect is manifested in terms of temperature stability. The embodiments can maintain a uniform temperature distribution in the test environment from 150°C to 200°C, thereby reducing the risk of electrolyte volatilization and leakage. In contrast, in the comparative examples, the electrolytic capacitors without the graphene coating, without the microencapsulated phase change materials, or without the optimized heat dissipation system showed local overheating, resulting in capacitance decay and increased leakage current.

[0076] In addition, the experimental data also show that the effective combination of the temperature sensor array and the infrared thermal imager plays an important role in the real-time and accuracy of temperature monitoring. As the high-temperature cycle progresses, the embodiments exhibit better temperature uniformity, avoiding local overheating caused by insufficient thermal management in the comparative examples, and further improving the working stability and lifespan of the electrolytic capacitor.

[0077] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high temperature resistant electrolytic capacitor, characterized in that: The electrolytic capacitor comprises the following components in parts by weight: Graphene or carbon nanotube coating: 80-90 parts, used to prepare electrolytic capacitor casing; Epoxy resin: 10-20 parts, used to form a composite material with graphene or carbon nanotubes; Aluminum alloy or copper: 90-95 parts, used to make heat sinks and heat pipes; Na2SO4·10H2O, CaCl2·6H2O or stearic acid: 60-80 parts, used to make phase change materials, embedded in electrolytic capacitor casings or heat sinks; Silicon dioxide nanoparticles in electrolyte: 15-30 parts, used for the preparation of electrolyte; Alcohol liquid: 5-10 parts, used to dissolve electrolytic salt and serve as the main solvent of the electrolyte.

2. A method for preparing a high temperature resistant electrolytic capacitor, characterized in that: Using claim 1, comprising the following steps: Heat conduction optimization design: The temperature field of the electrolytic capacitor is simulated through the non-steady-state heat conduction equation, the heat dissipation path of the electrolytic capacitor is optimized, and the heat is evenly conducted to the external heat dissipation device; Phase change material selection and microencapsulation: Select inorganic salt hydrate or fatty acid phase change materials, and use microencapsulation technology to evenly distribute the phase change materials in the electrolytic capacitor shell coating or heat sink to provide efficient heat regulation function; Electrolyte preparation and additive addition: Prepare electrolyte and add silicon dioxide nanoparticles to improve the high temperature resistance and thermal stability of the electrolyte to ensure that the capacitor can work reliably in a high temperature environment; Heat dissipation system design: Design heat sink and heat pipe system, use high thermal conductivity metal materials to make heat sink, and combine heat pipe technology to improve heat dissipation efficiency and ensure uniform temperature distribution inside the electrolytic capacitor; Assembly and testing: Assemble into electrolytic capacitors and perform performance tests in high temperature environments to verify their heat dissipation performance and long-term stability.

3. The method for preparing a high temperature resistant electrolytic capacitor according to claim 2, characterized in that: The heat conduction optimization design includes: Through numerical simulation and finite element analysis, the heat flow path in the electrolytic capacitor is calculated to determine the distribution of the temperature field; Based on thermal diffusivity calculation, optimize the material selection of electrolytic capacitors to ensure high thermal conductivity of the housing, heat sink and heat pipe; The heat flux density optimization algorithm is used to adjust the heat sink layout to ensure that the heat inside the capacitor can be quickly and effectively transferred to the external heat sink.

4. The method for preparing a high temperature resistant electrolytic capacitor according to claim 2, characterized in that: The phase change material selection and microencapsulation include: Select inorganic salt hydrate or fatty acid materials as phase change materials, and microencapsulate the phase change materials to ensure that they absorb 30-40J / g of heat in the temperature range of 150-200°C and prevent leakage. The particle size range of the microcapsules is 50-500μm; The microencapsulated phase change material is evenly coated or embedded in the shell coating or heat sink of the electrolytic capacitor to achieve stable temperature regulation through its phase change characteristics.

5. The method for preparing a high temperature resistant electrolytic capacitor according to claim 2, characterized in that: The electrolyte preparation and additive addition include: Prepare electrolyte base solvents, mainly carbonate solvents, to dissolve electrolyte salts and ensure that they have good conductivity; Add silica nanoparticles with a particle size range of 10-100 nm and disperse them evenly; The prepared electrolyte is subjected to a high temperature durability test to ensure that it will not volatilize or degrade in an environment of 150-200°C.

6. The method for preparing a high temperature resistant electrolytic capacitor according to claim 2, characterized in that: The heat sink design includes: Design the shape and size of the heat sink, use copper or aluminum alloy to make the heat sink, and calculate its surface area and heat dissipation efficiency; By optimizing the heat flow and adjusting the position of the heat sink, it is ensured that the heat can be quickly transferred from the inside of the electrolytic capacitor to the external heat dissipation system to avoid excessive local temperature inside the capacitor.

7. The method for preparing a high temperature resistant electrolytic capacitor according to claim 2, characterized in that: The heat pipe system design includes: The heat pipe quickly conducts heat from the inside of the electrolytic capacitor to the external heat sink through its evaporation and condensation process. The filling liquid of the heat pipe has a low evaporation temperature, ensuring its efficient heat transfer at high temperatures.

8. The method for preparing a high temperature resistant electrolytic capacitor according to claim 2, characterized in that: The assembly and testing include: Assemble the shell, phase change material, electrolyte, heat sink and heat pipe system into an electrolytic capacitor, ensuring that there is no leakage at all contact points and the shell is well sealed; Conduct high temperature performance tests on assembled electrolytic capacitors at 150°C, 180°C and 200°C for 1000 hours, monitoring the capacitance change, leakage current and loss tangent of the capacitors. The design is adjusted according to the test results to ensure that the electrolytic capacitors can work stably in high temperature environments and meet various performance requirements.

9. The method for preparing a high temperature resistant electrolytic capacitor according to claim 8, characterized in that: The high temperature environment test includes: Conduct long-term high-temperature cycle tests to simulate the long-term operating performance of electrolytic capacitors in high-temperature environments; Regularly measure the capacitance, leakage current and withstand voltage performance of electrolytic capacitors to ensure that the electrolytic capacitors meet the high-temperature working requirements; The changes in the internal temperature of the electrolytic capacitor during the test are monitored by an infrared thermal imager and a temperature sensor array to ensure that its temperature remains within a safe range.

10. The method for preparing a high temperature resistant electrolytic capacitor according to claim 9, characterized in that: The temperature sensor is a temperature sensor array formed by combining multiple K-type thermocouples or multiple surface-mounted thermistors to ensure that the operating temperature range of the electrolytic capacitor is greater than 250°C; The temperature sensor array is evenly distributed in the key heat source areas of the electrolytic capacitor, including the contact area between the electrolyte and the heat sink, the surface of the heat sink, and the location of the casing and heat pipe, ensuring that the temperature changes of various parts of the electrolytic capacitor can be monitored in real time.

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