High-temperature-resistant solid aluminum electrolytic capacitor and preparation method thereof

Abstract

The application discloses a high-temperature-resistant solid aluminum electrolytic capacitor and a preparation method thereof, and relates to the field of solid aluminum electrolytic capacitors. The high-temperature-resistant solid aluminum electrolytic capacitor comprises an anode foil unit, a sandwich composite dielectric layer, a thermal expansion transition layer, a cathode foil unit and a lead-out electrode unit. The middle interlayer of the sandwich composite dielectric layer cooperatively inhibits the oxidation and aging of the dielectric layer at high temperature. In combination with the buffering effect of the thermal expansion transition layer, the high-temperature-resistant capacity of the high-temperature-resistant solid aluminum electrolytic capacitor is greatly improved compared with that of a traditional product. The high compactness and high dielectric constant of the sandwich composite dielectric layer, in cooperation with the low contact resistance characteristics of the cathode bottom layer DBSA-doped PEDOT, greatly reduce the leakage current control at high temperature compared with that of a traditional solid capacitor, thereby reducing the energy loss and heat accumulation of the device. The thermal expansion coefficient of the thermal expansion transition layer is between the sandwich composite dielectric layer and the cathode foil unit, and the interface stress generated by high-low temperature cycles is relieved through gradient matching, so that the interlayer peeling rate is greatly reduced, and the fatigue resistance is significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid-state aluminum electrolytic capacitors, in particular to a high-temperature-resistant solid-state aluminum electrolytic capacitor and a preparation method thereof. BACKGROUND

[0002] Solid-state aluminum electrolytic capacitors have been widely used in many electronic devices due to their high specific capacitance and small size. The basic structure of the solid-state aluminum electrolytic capacitor includes an anode aluminum foil, a dielectric oxide film, a cathode material (such as conductive polymer, etc.), and a lead electrode. In the process of technological development, the specific surface area of the anode aluminum foil has been continuously optimized by optimizing the etching process, thereby increasing the capacitance of the capacitor. At the same time, compared with the traditional liquid electrolyte, the application of conductive polymer and other cathode materials reduces the equivalent series resistance (ESR) and improves the high-frequency performance and stability of the capacitor.

[0003] However, the current solid-state aluminum electrolytic capacitor still has obvious defects in high-temperature resistance. In a high-temperature environment, the molecular structure of the cathode material (such as commonly used conductive polymer) changes, which leads to a decrease in its electrical conductivity, and thus increases the leakage current of the capacitor. In addition, high temperature also accelerates the aging of the dielectric oxide film, reduces its dielectric performance, and makes the capacitance of the capacitor decay more severely and the ESR increase significantly. When the working temperature exceeds 125℃, these problems become more prominent, which seriously affects the reliability and service life of the capacitor in high-temperature industrial applications (such as oil exploration, metallurgy, etc.), new energy vehicle applications (such as battery management system, motor drive system), etc.

[0004] The multi-layer structure (aluminum foil / oxide layer / polymer / silver paste) of the solid-state aluminum electrolytic capacitor delaminates due to the accumulation of thermal stress at high temperature. In particular, the interface between the oxide film layer and the conductive polymer layer in the cathode region decreases in bonding strength when the temperature exceeds 130℃. Delamination not only increases the low equivalent series resistance ESR, but more seriously, in a high-ripple current scenario (such as a new energy vehicle inverter), the increase in local contact resistance leads to the formation of hot spots, which may trigger a thermal runaway chain reaction. The traditional laminated capacitor will also crack due to the resin packaging in a high-temperature and high-humidity environment, which further reduces the insulation performance. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a high-temperature-resistant solid-state aluminum electrolytic capacitor and a preparation method thereof. The technical scheme adopted is as follows:

[0006] A high-temperature-resistant solid-state aluminum electrolytic capacitor comprises an anode foil unit, a sandwich composite dielectric layer, a thermal expansion transition layer, a cathode foil unit and a lead-out electrode unit, the surface of the anode foil unit uses a porous structure of a native oxide film as a basic dielectric layer, one side of the sandwich composite dielectric layer is close to the native oxide film of the anode foil unit, and an intermediate interlayer for reducing thermal conductivity is arranged in the middle, one side of the thermal expansion transition layer is close to the other side of the sandwich composite dielectric layer, the cathode foil unit uses DBSA combined with PEDOT to form a cathode bottom layer close to the other side of the thermal expansion transition layer, and the cathode foil unit uses a conductive polymer combined with graphene quantum dots to form a cathode top layer, the lead-out electrode unit comprises an anode lug and a cathode lug, the anode lug is connected to the anode foil unit, and the cathode lug is connected to the cathode foil unit.

[0007] By adopting the technical scheme, the intermediate interlayer of the sandwich composite dielectric layer cooperatively inhibits oxidation and aging of the dielectric layer at high temperature. In combination with the buffering effect of the thermal expansion transition layer, the high-temperature resistance of the capacitor is greatly improved compared with traditional products.

[0008] The high density and high dielectric constant of the sandwich composite dielectric layer, in combination with the low contact resistance characteristic of the DBSA-doped PEDOT cathode bottom layer, greatly reduce the leakage current at high temperature compared with traditional solid-state capacitors, thereby reducing the energy loss and heat accumulation of the device.

[0009] The thermal expansion coefficient of the thermal expansion transition layer is between the sandwich composite dielectric layer and the cathode foil unit, and the interface stress generated by high-low temperature cycles is relieved through gradient matching, so that the interlayer peeling rate is greatly reduced, and the fatigue resistance is significantly improved.

[0010] The porous structure of the anode foil unit and the frame support effect of the composite dielectric layer greatly improve the compressive strength of the overall structure, and the vibration impact of new energy vehicles and other scenes can be tolerated.

[0011] The core cathode layer adopts a double-layer structure of PEDOT:PSS, the conductivity retention rate is high, and in combination with the low loss characteristic of the dielectric layer, the capacity attenuation rate is reduced.

[0012] The cathode top layer introduces graphene quantum dots to construct a three-dimensional conductive network, so that the ESR value at high frequency is reduced to 8-12 mΩ, and the increase is less than 0% after 150℃ / 1000h aging, which meets the high-frequency filtering demand of the new energy vehicle motor driving system.

[0013] Each layer structure adopts a mature coating process and automatic assembly equipment, the material cost is lower than that of a full ceramic capacitor, and the product is suitable for large-scale production.

[0014] The product can be directly applied to extreme environments such as high-temperature industries and new energy vehicles (battery management system BMS, on-board charger OBC).

[0015] Optionally, the isolation packaging unit comprises an isolation layer and a packaging layer, the isolation layer is wrapped outside the cathode foil unit, and the packaging layer is packaged outside the isolation layer and the bottom of the lead electrode unit.

[0016] Optionally, the isolation layer is a polypropylene isolation paper in a fiber mesh structure, and the packaging layer is a modified epoxy resin packaging body.

[0017] Optionally, the sandwich composite dielectric layer comprises a frame structure and an intermediate layer, the frame structure is made of a high polymer nanocomposite material, a hollow part is arranged in the middle, and the intermediate layer is made of a liquid crystal polyarylate and high-entropy ceramic nanoparticles and is arranged in the hollow part.

[0018] By adopting the above technical scheme, the high polymer nanocomposite material (such as PI and nano-aluminum oxide composite) used in the frame structure itself has a high-temperature resistance of ≥400℃, forms a rigid support skeleton, and can resist structural deformation under high temperature; the liquid crystal polyarylate and high-entropy ceramic nanoparticle composite system of the intermediate layer further improves the heat aging resistance of the overall dielectric layer. The two work together to keep the insulation resistance retention rate of the dielectric layer at 150℃ environment high, providing a core guarantee for the long-term high-temperature operation of the capacitor.

[0019] The high polymer nanocomposite material of the frame structure has a high dielectric constant, which can ensure the basic power storage capacity of the dielectric layer; the liquid crystal polyarylate and high-entropy ceramic nanoparticle composite system of the intermediate layer improves the overall dielectric constant to 20-25 through the interface polarization effect, and controls the dielectric loss tangent value to be <0.002 (1kHz) by using the insulation property of high-entropy ceramics, which is much lower than that of traditional dielectric layers, reducing energy loss at high frequency.

[0020] The high polymer nanocomposite material of the frame structure has a thermal conductivity of 0.8-1.2 W / m·K, which can quickly conduct local heat; the liquid crystal polyarylate and high-entropy ceramic composite system of the intermediate layer has a thermal conductivity of 0.3-0.5 W / m·K, forming a high-middle-high thermal conductivity gradient. This design not only avoids the heat concentration caused by a single high-thermal-conductivity material, but also reduces the working temperature of the dielectric layer through the high-efficiency heat dissipation path of the frame structure, delaying the material aging speed.

[0021] Optionally, the thermal expansion transition layer is made of siloxane modified polythiophene.

[0022] By adopting the technical scheme, the siloxane-modified polythiophene has a controllable thermal expansion coefficient (30-40 ppm / ℃ in the range of 25-150℃), which is just between the sandwich composite dielectric layer and the cathode layer, forming a continuous thermal expansion gradient. This design can greatly reduce the interfacial shear stress generated by high and low temperature cycles, greatly reduce the peeling rate of the dielectric layer and the cathode layer, and significantly improve the stability of the interlayer structure.

[0023] The conjugated structure of the polythiophene main chain itself has certain high temperature resistance, and the introduction of the siloxane side chain further improves the oxidation resistance. The modified polythiophene has a low oxidation weight loss rate in an air atmosphere at 150℃, and can resist oxidation degradation in a high temperature environment for a long time, ensuring that the transition layer maintains structural integrity throughout the life cycle of the capacitor.

[0024] Optionally, the cathode foil unit comprises a cathode bottom layer, a core cathode layer and a cathode top layer, the core cathode layer adopts a double-layer conductive polymer composite material, the cathode bottom layer is formed by DBSA combined with PEDOT, and the cathode top layer is formed by a conductive polymer combined with graphene quantum dots, and the cathode bottom layer and the cathode top layer are respectively compounded on both sides of the core cathode layer.

[0025] Optionally, the cathode bottom layer is formed by DBSA doped PEDOT with a thickness of 0.5-1 μm to form a conductive slurry, which is coated on one side of the core cathode layer and dried;

[0026] The cathode bottom layer is formed by adding graphene quantum dots with a particle size of 3-5 nm to a conductive polymer solution, ultrasonic dispersion to form a conductive slurry, and then coating the other side of the core cathode layer by inkjet printing and drying.

[0027] By adopting the technical scheme, the double-layer conductive polymer composite material of the core cathode layer forms a synergistic conductive network, with an electrical conductivity of 500-800 S / cm, providing a main channel for current transmission; the DBSA doped PEDOT of the cathode bottom layer forms an ohmic contact with the core layer, with a contact resistance of less than 10 mΩ; and the graphene quantum dots of the cathode top layer construct a three-dimensional conductive path through quantum tunneling effect, reducing the equivalent series resistance at high frequency to 8-12 mΩ, which is more than 50% lower than the traditional single-layer cathode structure, significantly improving the high-frequency filtering performance of the capacitor.

[0028] The double-layer structure of the core cathode layer enhances the thermal stability through molecular chain interweaving, and the electrical conductivity retention rate is higher than that of the traditional PEDOT layer at 150℃;

[0029] DBSA doping makes the PEDOT molecular chain more compact, and the electrical conductivity attenuation rate of the cathode bottom layer is less than 8% after aging at 150℃ / 1000h;

[0030] The high thermal stability of graphene quantum dots can inhibit the thermal oxidation of the top layer of the cathode, so that the mass loss rate of the top layer is less than 1% at high temperature, and the three layers cooperate to ensure that the leakage current is stable at less than 0.7 μA in a 150°C environment.

[0031] The 0.5-1 μm thin film of the bottom layer of the cathode formed by microgravure printing is precisely matched with the surface roughness of the core cathode layer, and has high interface bonding strength;

[0032] The inkjet printing process of the top layer of the cathode can realize nanoscale adhesion with the core layer, and the graphene quantum dots fill the interface gap, so that the interlayer porosity is reduced, and the performance mutation caused by interface delamination at high temperature is effectively avoided.

[0033] The combined process of microgravure printing and inkjet printing can realize small thickness deviation of the cathode layer, and ensure that the performance fluctuation between batches is less than 3%;

[0034] The ultrasonic dispersion process of graphene quantum dots has high particle dispersion uniformity, avoids local non-uniform conduction caused by agglomeration, and controls the capacitor capacity deviation within ±2%.

[0035] Optionally, the anode tab is ultrasonically welded, and the cathode tab is bonded with conductive silver paste.

[0036] A preparation method of a high-temperature-resistant solid-state aluminum electrolytic capacitor is used to prepare a high-temperature-resistant solid-state aluminum electrolytic capacitor, comprising the following steps:

[0037] Step 1, preparation of an anode foil unit;

[0038] Step 2, the porous structure aluminum foil substrate is placed in a mixed borate-sulfate solution, and a primary oxide film is generated on the surface of the aluminum foil by using a step-by-step voltage boosting mode. After chemical conversion, vacuum drying is performed to obtain an anode foil unit;

[0039] Step 3, preparation of a frame structure slurry;

[0040] Step 4, melt the liquid crystal polyarylate particles, add high-entropy ceramic nanoparticles for melt blending, crush after cooling, disperse the powder in NMP solvent, ultrasonic dispersion, and form an intermediate interlayer slurry;

[0041] Step 5, preparation of a sandwich composite dielectric layer;

[0042] Step 6, under the protection of nitrogen, dissolve the thiophene monomer in chloroform solvent, add 3-aminopropyltriethoxysilane, stir to generate siloxane grafted thiophene precursor; add ferric chloride, stir to form a siloxane modified polythiophene solution, ultrasonic defoaming for 15 min, use a slit to coat the modified polythiophene solution on the surface of the sandwich composite dielectric layer, the wet film thickness is 150-200 nm, vacuum drying to form a thermal expansion transition layer;

[0043] Step 7, preparation of the core cathode layer, the first layer uses a conductive polymer composite to add carbon nanotubes, ultrasonic dispersion and drying;

[0044] The second layer uses a polypyrrole solution to add graphene nanosheets, ball milling dispersion, coating on the surface of the first layer, drying to form a double-layer core cathode layer;

[0045] Step 8, preparation of the cathode bottom layer;

[0046] Step 9, preparation of the cathode top layer;

[0047] Step 10, welding the anode lug on the non-porous area of the anode foil unit, smearing conductive silver glue on the surface of the cathode top layer, and pressing after the cathode lug is matched to obtain a solid aluminum electrolytic capacitor.

[0048] Optionally, it also includes the preparation step of isolating the packaging unit:

[0049] Step 11, using 25μm thick polypropylene isolation paper, completely wrapping the cathode foil unit through an automatic wrapping machine, the wrapping overlap is 1-2mm, and the edges are fixed with heat-resistant glue points;

[0050] Step 12, using modified epoxy resin to form in a transfer molding machine, and post-curing at 190℃ after forming.

[0051] In summary, the present application includes at least one of the following beneficial technical effects:

[0052] The present application can provide a high-temperature-resistant solid aluminum electrolytic capacitor and a preparation method thereof, the middle interlayer of the sandwich composite dielectric layer cooperatively inhibits the oxidation and aging of the dielectric layer at high temperature. Combined with the buffering effect of the thermal expansion transition layer, the high-temperature resistance of the traditional product is greatly improved;

[0053] The high density and high dielectric constant of the sandwich composite dielectric layer, combined with the low contact resistance characteristics of the DBSA-doped PEDOT of the cathode bottom layer, greatly reduce the leakage current control at high temperature compared with traditional solid capacitors, reducing the energy loss and heat accumulation of the device;

[0054] The thermal expansion coefficient of the thermal expansion transition layer is between the sandwich composite dielectric layer and the cathode foil unit, which relieves the interfacial stress generated by high-low temperature cycling through gradient matching, greatly reduces the interlayer peeling rate, and significantly improves the fatigue resistance.

[0055] The porous structure of the anode foil unit and the frame support effect of the composite dielectric layer greatly improve the compressive strength of the overall structure, and can withstand the vibration impact of new energy vehicles and other scenes.

[0056] Each layer structure adopts mature coating process and automatic assembly equipment, material cost is reduced compared with full ceramic capacitor, and the full ceramic capacitor is suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 is a cross-sectional structure principle schematic diagram of a high-temperature-resistant solid-state aluminum electrolytic capacitor of the present application;

[0058] Figure 2 is a preparation method flowchart of a high-temperature-resistant solid-state aluminum electrolytic capacitor of the present application.

[0059] BRIEF DESCRIPTION OF DRAWINGS: 11, original oxide film; 21, frame structure; 22, intermediate interlayer; 3, thermal expansion transition layer; 41, cathode bottom layer; 42, cathode top layer; 43, core cathode; 51, anode tab; 52, cathode tab; 61, isolation layer; 62, packaging layer. DETAILED DESCRIPTION

[0060] The present application will be further described in detail below with reference to the accompanying drawings.

[0061] The present application discloses a high-temperature-resistant solid-state aluminum electrolytic capacitor and a preparation method thereof.

[0062] REFERENCE Figure 1 and Figure 2 , embodiment 1, a high-temperature-resistant solid-state aluminum electrolytic capacitor, comprising an anode foil unit, a sandwich composite dielectric layer, a thermal expansion transition layer 3, a cathode foil unit and a lead electrode unit, the surface of the anode foil unit adopts a porous structure original oxide film 11 as a basic dielectric layer, one side of the sandwich composite dielectric layer is closely attached to the original oxide film 11 of the anode foil unit, and an intermediate interlayer 22 for reducing thermal conductivity is arranged in the middle, one side of the thermal expansion transition layer 3 is closely attached to the other side of the sandwich composite dielectric layer, the cathode foil unit adopts DBSA combined with PEDOT to form a cathode bottom layer 41 closely attached to the other side of the thermal expansion transition layer 3, the cathode foil unit adopts a conductive polymer combined with graphene quantum dots to form a cathode top layer 42, the lead electrode unit includes an anode tab 51 and a cathode tab 52, the anode tab 51 is connected to the anode foil unit, and the cathode tab 52 is connected to the cathode foil unit.

[0063] The intermediate interlayer 22 of the sandwich composite dielectric layer cooperates to inhibit oxidation and aging of the dielectric layer at high temperature. Combined with the buffering effect of the thermal expansion transition layer, the high-temperature resistance of the product is greatly improved compared with traditional products.

[0064] The high density and high dielectric constant of the sandwich composite dielectric layer, combined with the low contact resistance characteristics of the cathode bottom layer 41 DBSA doped PEDOT, greatly reduce the leakage current control at high temperature compared with traditional solid-state capacitors, reducing the energy loss and heat accumulation of the device.

[0065] The thermal expansion coefficient of the thermal expansion transition layer 3 is between the sandwich composite dielectric layer and the cathode foil unit, which relieves the interfacial stress generated by high and low temperature cycles through gradient matching, greatly reduces the interlayer peeling rate, and significantly improves the fatigue resistance.

[0066] The porous structure of the anode foil unit and the frame support of the composite dielectric layer greatly improve the compressive strength of the overall structure, and can withstand the vibration impact of new energy vehicles and other scenes.

[0067] The core cathode layer 43 adopts a double-layer structure of PEDOT:PSS, which has high conductivity retention rate, and cooperates with the low loss characteristics of the dielectric layer to reduce the capacity attenuation rate.

[0068] The cathode top layer 42 introduces graphene quantum dots to construct a three-dimensional conductive network, so that the ESR value at high frequency is reduced to 8-12 mΩ, and the increase is less than 0% after 150℃ / 1000h aging, meeting the high-frequency filtering requirements of new energy vehicle motor drive systems.

[0069] Each layer structure adopts mature coating process and automatic assembly equipment, and the material cost is lower than that of all-ceramic capacitors, suitable for mass production.

[0070] The product can be directly applied to extreme environments such as high-temperature industry, new energy vehicles (battery management system BMS, on-board charger OBC), etc.

[0071] Embodiment 2 further comprises an isolation packaging unit, which comprises an isolation layer 61 and a packaging layer 62, the isolation layer 61 is wrapped outside the cathode foil unit, and the packaging layer 62 is packaged outside the isolation layer 61 and the bottom of the lead electrode unit.

[0072] Embodiment 3, the isolation layer 61 is a polypropylene isolation paper in a fiber network structure, and the packaging layer 62 is a modified epoxy resin packaging body.

[0073] Embodiment 4, the sandwich composite dielectric layer comprises a frame structure 21 and an intermediate interlayer 22, the frame structure 21 is made of high molecular nanocomposite material, and a hollow part is arranged in the middle, and the intermediate interlayer 22 is composed of liquid crystal polyarylate and high-entropy ceramic nanoparticles, and is located in the hollow part.

[0074] The high polymer nanocomposite material (e.g., PI and nano-alumina composite) adopted by the framework structure 21 has a high-temperature resistance of ≥400°C itself, forms a rigid support skeleton, and can resist structural deformation under high temperature; the liquid crystal polyarylate and high-entropy ceramic nanoparticle composite system of the intermediate interlayer 22 further improves the heat aging resistance of the overall dielectric layer. The two work together to make the dielectric layer maintain a high insulation resistance retention rate of 150°C environment, providing a core guarantee for the long-term high-temperature operation of the capacitor.

[0075] The high polymer nanocomposite material of the framework structure 21 has a high dielectric constant, which can ensure the basic power storage capacity of the dielectric layer; the liquid crystal polyarylate and high-entropy ceramic nanoparticle composite system of the intermediate interlayer 22 improves the overall dielectric constant to 20-25 through the interface polarization effect, and controls the dielectric loss tangent to <0.002 (1 kHz) by using the insulation characteristics of high-entropy ceramics, which is much lower than that of traditional dielectric layers, reducing energy loss at high frequency.

[0076] The high polymer nanocomposite material of the framework structure 21 has a thermal conductivity of 0.8-1.2 W / m·K, which can quickly conduct local heat; the liquid crystal polyarylate and high-entropy ceramic composite system of the intermediate interlayer 22 has a thermal conductivity of 0.3-0.5 W / m·K, forming a high-medium-high thermal conductivity gradient. This design not only avoids the heat concentration caused by single high thermal conductivity material, but also reduces the working temperature of the dielectric layer through the high-efficiency heat dissipation path of the framework structure, delaying the material aging speed.

[0077] In Example 5, the thermal expansion transition layer 3 is made of siloxane-modified polythiophene.

[0078] The siloxane-modified polythiophene has a controllable thermal expansion coefficient (30-40 ppm / °C in the 25-150°C interval), which is just between the sandwich composite dielectric layer and the cathode layer, forming a continuous thermal expansion gradient. This design can greatly reduce the interfacial shear stress generated by high-low temperature cycling, greatly reduce the peeling rate of the dielectric layer and the cathode layer, and significantly improve the interlayer structure stability. The conjugated structure of the polythiophene backbone gives it certain high-temperature resistance, and the introduction of siloxane side chains further improves the oxidation resistance. The modified polythiophene has a low oxidation weight loss rate in a 150°C air atmosphere, and can resist oxidation degradation in a high-temperature environment for a long time, ensuring the structural integrity of the transition layer throughout the life cycle of the capacitor.

[0079] In Example 6, the cathode foil unit includes a cathode bottom layer 41, a core cathode layer 43, and a cathode top layer 42, the core cathode layer 43 adopts a double-layer conductive polymer composite material, the cathode bottom layer 41 is formed by DBSA combined with PEDOT, the cathode top layer 42 is a conductive polymer combined with graphene quantum dots, and the cathode bottom layer 41 and the cathode top layer 42 are respectively compounded on both sides of the core cathode layer 43.

[0080] The cathode bottom layer 41 is formed by micro gravure printing after the conductive paste formed by DBSA doped PEDOT with a thickness of 0.5-1 μm is coated on the side of the core cathode layer 43 and dried;

[0081] The cathode bottom layer 41 is formed by inkjet printing after the conductive paste formed by graphene quantum dots with a particle size of 3-5 nm in a conductive polymer solution is dispersed by ultrasonic and coated on the other side of the core cathode layer 43 and dried.

[0082] The double-layer conductive polymer composite of the core cathode layer 43 forms a synergistic conductive network, with an electrical conductivity of 500-800 S / cm, providing a main channel for current transmission.

[0083] The DBSA doped PEDOT of the cathode bottom layer 41 forms an ohmic contact with the core layer, with a contact resistance of <10 mΩ; the graphene quantum dots of the cathode top layer 42 construct a three-dimensional conductive path through quantum tunneling effect, reducing the equivalent series resistance under high frequency to 8-12 mΩ, a decrease of more than 50% compared to the traditional single-layer cathode structure, significantly improving the high-frequency filtering performance of the capacitor.

[0084] The double-layer structure of the core cathode layer enhances thermal stability through molecular chain interweaving, with a conductivity retention rate of more than the traditional PEDOT layer at 150°C;

[0085] DBSA doping makes the PEDOT molecular chain more compact, with a conductivity decay rate of <8% after aging at 150°C / 1000h;

[0086] The high thermal stability of graphene quantum dots can inhibit the thermal oxidation of the cathode top layer, with a mass loss rate of <1% at high temperature, and the three-layer synergy ensures that the leakage current is stable at <0.7 μA in a 150°C environment.

[0087] The 0.5-1 μm thin film of the cathode bottom layer 41 formed by micro gravure printing precisely matches the surface roughness of the core cathode layer, with high interfacial bonding strength;

[0088] The inkjet printing process of the cathode top layer 42 can achieve nanoscale adhesion with the core layer, and the graphene quantum dots fill the interface gaps, reducing the interlayer porosity and effectively avoiding performance mutations caused by interface delamination at high temperature.

[0089] The combined process of micro gravure printing and inkjet printing can achieve small thickness deviation of the cathode layer, ensuring that the performance fluctuation between batches is less than 3%;

[0090] The ultrasonic dispersion process of graphene quantum dots makes the particle dispersion uniformity high, avoiding local conductive unevenness caused by agglomeration, and controlling the capacitor capacity deviation within ±2%.

[0091] Example 8, the anode tab 51 uses ultrasonic metal welding, the cathode tab 52 uses conductive silver adhesive.

[0092] Example 9, a method for preparing a high-temperature-resistant solid-state aluminum electrolytic capacitor, for preparing a high-temperature-resistant solid-state aluminum electrolytic capacitor, comprising the following steps:

[0093] Step 1, preparation of anode foil unit;

[0094] Step 2, the porous structure of the aluminum foil substrate is placed in the mixed borate sulfate solution, and the primary oxide film is generated on the surface of the aluminum foil by using the step-by-step voltage boosting mode. After chemical conversion, vacuum drying is carried out for standby to obtain an anode foil unit;

[0095] Step 3, preparation of frame structure slurry;

[0096] Step 4, melt the liquid crystal polyarylate particles, add high-entropy ceramic nanoparticles, blend after melting, crush after cooling, disperse the powder in NMP solvent, ultrasonic dispersion, form the middle interlayer slurry;

[0097] Step 5, preparation of sandwich composite dielectric layer;

[0098] Step 6, under the protection of nitrogen, dissolve the thiophene monomer in chloroform solvent, add 3-aminopropyl triethoxysilane, stir to generate siloxane grafted thiophene precursor; add ferric chloride, stir to form siloxane modified polythiophene solution, ultrasonic defoaming for 15 min, use slit coating to coat the modified polythiophene solution on the surface of the sandwich composite dielectric layer, wet film thickness 150-200 nm, vacuum drying to form thermal expansion transition layer 3;

[0099] Step 7, preparation of core cathode layer 43, the first layer uses conductive polymer composite adding carbon nanotubes, ultrasonic dispersion and drying;

[0100] The second layer uses a polypyrrole solution adding graphene nanosheet, ball milling dispersion, coating on the surface of the first layer, drying to form a double-layer core cathode layer 43;

[0101] Step 8, preparation of cathode bottom layer 41;

[0102] Step 9, preparation of cathode top layer 42;

[0103] Step 10, weld the anode tab 51 on the non-porous area of the anode foil unit, smear conductive silver adhesive on the surface of the cathode top layer 42, press after pasting the cathode tab 52, solidification to obtain a solid-state aluminum electrolytic capacitor.

[0104] Specifically, the following steps are used:

[0105] Step 1, preparation of anode foil unit, aluminum foil is immersed in a mixed etching solution of hydrochloric acid and sulfuric acid, a porous aluminum foil substrate is formed by pulse current etching process, after etching, the aluminum foil is cleaned with deionized water by ultrasonic and dried;

[0106] Step 2, the porous aluminum foil substrate is placed in a mixed borate and sulfuric acid chemical conversion solution, a stepwise voltage rising mode is adopted to rise to 50V constant voltage at a rate of 3V / min, and then to 120V constant voltage at a rate of 2V / min, a native oxide film with a thickness of 100-130nm is formed on the surface of the aluminum foil, after chemical conversion, vacuum drying is carried out to obtain an anode foil unit;

[0107] Step 3, pyromellitic dianhydride and 4,4'-diamino diphenyl ether are dissolved in NMP solvent according to a molar ratio of 1:1.05, stirring to form PI precursor, nano-aluminum oxide particles are added to the precursor, planetary ball milling for 5h, the particle size distribution is less than or equal to 25nm, and a frame structure slurry is formed;

[0108] Step 4, melt the liquid crystal polyarylate particles, add high-entropy ceramic nanoparticles, melt blend by using a twin-screw extruder, crush into powder with a particle size of 5-10μm after cooling, disperse the powder in NMP solvent, ultrasonic dispersion, form an intermediate interlayer slurry;

[0109] Step 5, using a precision coating machine, first coat the frame structure slurry on the surface of the native oxide film of the anode foil, pre-bake at 150℃ to form a bottom frame, laser etching is used to process a hollow part with a thickness of 20-30nm on the surface of the bottom frame, then fill the intermediate interlayer slurry into the hollow part, pre-bake at 150℃, coat the frame structure slurry on the top of the hollow part, pre-bake at 120℃ for 15min, form a complete sandwich composite dielectric layer, the whole is stepwise cured in a nitrogen atmosphere to ensure that the imidization degree is greater than or equal to 96%;

[0110] Step 6, under the protection of nitrogen, dissolve the thiophene monomer in chloroform solvent, add 3-aminopropyl triethoxysilane, stir at 60℃ to generate siloxane grafted thiophene precursor; add ferric chloride, stir at 35℃ to polymerize and form siloxane modified polythiophene solution, ultrasonic defoaming for 15min, use slot coating to coat the modified polythiophene solution on the surface of the sandwich composite dielectric layer, the wet film thickness is 150-200nm, vacuum drying at 90℃ to form a thermal expansion transition layer 3 with a thermal expansion coefficient of 30-40ppm / ℃;

[0111] Step 7, preparation of core cathode layer 43, the first layer is a conductive polymer composite material with 10-20nm diameter carbon nanotubes, ultrasonic dispersion for 30min, coating thickness is 1μm, drying at 100℃;

[0112] The second layer is coated on the surface of the first layer by adding 1-2 nm thick graphene nanosheets to a polypyrrole solution, ball-milling dispersion, with a thickness of 0.8 μm, and drying at 80°C to form a double-layer core cathode layer 43;

[0113] In step 8, the PEDOT monomer and DBSA are dissolved in deionized water, ammonium persulfate solution is added, stirring is performed for polymerization to form a conductive slurry, the slurry is coated on one side of the core cathode layer by 300 mesh micro-gravure printing, the wet film thickness is 1-1.2 μm, drying is performed at 90°C for 40 min, and a cathode bottom layer 41 is formed.

[0114] In step 9, graphene quantum dots with a particle size of 3-5 nm are added to the conductive polymer composite solution and ultrasonic dispersion is performed, the other side of the core cathode layer is coated by inkjet printing, the wet film thickness is 1.5-2 μm, and vacuum drying is performed to form a cathode top layer 42.

[0115] In step 10, a 30 μm thick pure aluminum is selected as an anode tab 51, the anode tab 51 is welded to the non-porous area of the anode foil unit by an ultrasonic metal welding machine, a 50 μm thick nickel-plated copper is selected as a cathode tab 52, the cathode tab 52 is pasted to the surface of the cathode top layer 42 after the conductive silver paste is applied, a pressure of 0.15 MPa is applied, and solid-state aluminum electrolytic capacitors are obtained after curing at 160°C.

[0116] In step 10, a 30 μm thick pure aluminum is selected as an anode tab 51, the anode tab 51 is welded to the non-porous area of the anode foil unit by an ultrasonic metal welding machine, a 50 μm thick nickel-plated copper is selected as a cathode tab 52, the cathode tab 52 is pasted to the surface of the cathode top layer 42 after the conductive silver paste is applied, a pressure of 0.15 MPa is applied, and solid-state aluminum electrolytic capacitors are obtained after curing at 160°C.

[0117] In step 11, a 25 μm thick polypropylene isolation paper is used to completely wrap the cathode foil unit by an automatic wrapping machine, the wrapping overlap is 1-2 mm, and the edges are fixed by heat-resistant glue points.

[0118] In step 12, a modified epoxy resin is used to form a shape in a transfer molding machine, and post-curing is performed at 190°C after shaping.

[0119] The following specific examples are used to illustrate the implementation principles of the present application:

[0120] Core structure parameters: anode foil unit: 99.95% pure aluminum foil (thickness 60 μm), pulse etched by a hydrochloric acid-sulfuric acid mixed solution (pore diameter 3-4 μm, porosity 75%), and a 110 nm thick original oxide film (Al2O3) is generated. Sandwich composite dielectric layer: the frame structure is composed of PI and 18 wt% γ-Al2O3 nanoparticles (15 nm), the middle layer is liquid crystal polyarylate + 5 wt% high-entropy ceramic nanoparticles (10 nm), the hollow part has a thickness of 25 nm, and the total dielectric layer has a thickness of 90 nm.

[0121] Thermal expansion transition layer: siloxane modified polythiophene (thickness 180 nm), thermal expansion coefficient 35 ppm / °C. Cathode foil unit:

[0122] Core cathode layer 43: 1st layer PEDOT:PSS + 3wt% carbon nanotubes (1 pm), 2nd layer PPy + 2wt% graphene nanoplatelets (0.8 pm);

[0123] Cathode bottom layer 41: 0.8 pm thick DBSA doped PEDOT (30wt%), micro gravure printing (300 mesh); Cathode top layer: 1.8 pm thick PEDOT:PSS + 6wt% graphene quantum dots (4 nm), inkjet printing (1200 dpi).

[0124] Lead-out electrode 42: 30 pm aluminum tab (ultrasonic welding), 50 pm nickel plated copper tab (conductive silver adhesive).

[0125] Isolation packaging: 25 pm polypropylene isolation paper + 1.0 mm modified epoxy resin packaging body.

[0126] Sandwich dielectric layer curing: 320°C for 2h in nitrogen atmosphere, 97% imidization degree;

[0127] Thermal expansion transition layer drying: 90°C vacuum drying for 40min;

[0128] Cathode layer drying: bottom layer 90°C / 40min, top layer 110°C vacuum drying for 1h;

[0129] Packaging curing: 190°C post-curing for 5h, water absorption rate 0.07%.

[0130] II. Performance testing as shown in Table 1 (150°C / 1000h aging test):

[0131] Table 1

[0132]

[0133]

[0134] Test environment: 150°C constant temperature oven for 1000h, sample every 200h for testing;

[0135] Capacity and ESR test: LCR tester (frequency 1 kHz / 100 kHz) is used;

[0136] Leakage current test: 16V DC voltage is applied, read after 30min at 150°C;

[0137] Interlayer peeling rate: interface integrity is observed by scanning electron microscope (SEM), and the peeling area ratio is calculated; cost accounting: based on a large-scale production scene of 1 million units per day capacity.

[0138] The embodiment meets the strict requirements of high-temperature industry and new energy vehicles on capacitors through multi-layer structure cooperative design, and is particularly outstanding in 150 DEG C long-term stability and high-frequency performance.

[0139] The above are preferred embodiments of the present application, and do not limit the protection scope of the present application, so: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A high-temperature-resistant solid aluminum electrolytic capacitor, characterized by: The anode foil unit, the sandwich composite dielectric layer, the thermal expansion transition layer (3), the cathode foil unit and the lead-out electrode unit, the surface of the anode foil unit uses the porous structure of the original oxide film (11) as the basic dielectric layer, one side of the sandwich composite dielectric layer is close to the original oxide film (11) of the anode foil unit, the middle is provided with the intermediate interlayer (22) for reducing the thermal conductivity, one side of the thermal expansion transition layer (3) is close to the other side of the sandwich composite dielectric layer, the cathode foil unit adopts DBSA to combine PEDOT to form the cathode bottom layer (41) and is close to the other side of the thermal expansion transition layer (3), the cathode foil unit adopts the conductive polymer combined with graphene quantum dots to form the cathode top layer (42), the lead-out electrode unit includes the anode lug (51) and the cathode lug (52), the anode lug (51) is connected with the anode foil unit, and the cathode lug (52) is connected with the cathode foil unit; The sandwich composite dielectric layer includes the frame structure (21) and the intermediate interlayer (22), the frame structure (21) is made of high molecular nanocomposite, and a hollow part is arranged in the middle, and the intermediate interlayer (22) is made of liquid crystal polyarylate and high-entropy ceramic nanoparticles and is located in the hollow part; The thermal expansion transition layer (3) is made of siloxane modified polythiophene.

2. The solid aluminum electrolytic capacitor of claim 1, wherein: It also includes an isolation packaging unit, the isolation packaging unit includes an isolation layer (61) and a packaging layer (62), the isolation layer (61) is wrapped outside the cathode foil unit, and the packaging layer (62) is packaged outside the isolation layer (61) and the bottom of the lead-out electrode unit.

3. A solid state aluminum electrolytic capacitor with high temperature resistance according to claim 2, characterized in that: The isolation layer (61) is polypropylene isolation paper in a fiber network structure, and the packaging layer (62) is a modified epoxy resin packaging body.

4. The solid electrolytic capacitor of claim 1, wherein: the solid electrolyte is a solid aluminum electrolytic capacitor. The cathode foil unit includes a cathode bottom layer (41), a core cathode layer (43) and a cathode top layer (42), the core cathode layer (43) is made of double-layer conductive polymer composite material, the cathode bottom layer (41) is formed by combining DBSA with PEDOT, and the cathode top layer (42) is made of conductive polymer combined with graphene quantum dots, and the cathode bottom layer (41) and the cathode top layer (42) are respectively combined on both sides of the core cathode layer (43).

5. A solid state aluminum electrolytic capacitor with high temperature resistance according to claim 4, characterized in that: The cathode bottom layer (41) is formed by using DBSA doped PEDOT with a thickness of 0.5-1 μm to form a conductive slurry, which is coated on the side of the core cathode layer (43) and dried to form; The cathode bottom layer (41) adds graphene quantum dots with a particle size of 3-5 nm in a conductive polymer solution, and ultrasonic dispersion is formed to form a conductive slurry, which is coated on the other side of the core cathode layer (43) and dried to form.

6. A solid state aluminum electrolytic capacitor with high temperature resistance according to claim 5, characterized in that: The anode lug (51) is ultrasonically welded, and the cathode lug (52) is adhered by conductive silver glue.

7. A process for the production of a solid aluminum electrolytic capacitor of high temperature resistance according to any one of claims 1 to 6, characterized in that, The steps include: Step 1, preparation of anode foil unit; Step 2, the porous structure aluminum foil substrate is placed in a mixed borate-sulfate solution, and a step-by-step voltage boosting mode is used to generate an original oxide film on the surface of the aluminum foil, and vacuum drying is performed after chemical conversion to obtain an anode foil unit; Step 3, preparation of frame structure slurry; Step 4, melt the liquid crystal polyarylate particles, add high-entropy ceramic nanoparticles for melt blending, crush after cooling, disperse the powder in NMP solvent, ultrasonic dispersion to form an intermediate interlayer slurry; Step 5, prepare a sandwich composite dielectric layer; Step 6, under nitrogen protection, dissolve thiophene monomers in chloroform solvent, add 3-aminopropyl triethoxysilane, stir to generate siloxane grafted thiophene precursor; add ferric chloride, stir to polymerize and form a siloxane modified polythiophene solution, ultrasonic defoaming for 15 min, use slit coating to coat the modified polythiophene solution on the surface of the sandwich composite dielectric layer, wet film thickness 150-200 nm, vacuum drying to form a thermal expansion transition layer (3); Step 7, preparation of the core cathode layer (43), the first layer uses conductive polymer composite material added with carbon nanotubes, ultrasonic dispersion and drying; The second layer uses a polypyrrole solution added with graphene nanosheets, ball milling dispersion, coated on the surface of the first layer, dried to form a double-layer core cathode layer (43); Step 8, preparation of the cathode bottom layer (41); Step 9, preparation of the cathode top layer (42); Step 10, weld the anode lug (51) on the non-porous area of the anode foil unit, apply conductive silver paste on the surface of the cathode top layer (42), press after pasting the cathode lug (52), solidification to obtain a solid aluminum electrolytic capacitor.

8. The method for preparing a high-temperature resistant solid aluminum electrolytic capacitor according to claim 7, characterized in that, Also includes the preparation steps of the isolation packaging unit: Step 11, use 25 μm thick polypropylene isolation paper, completely wrap the cathode foil unit by automatic wrapping machine, wrap overlap 1-2 mm, use heat-resistant glue points to fix the edges; Step 12, use modified epoxy resin to form in the transfer molding machine, post-cure at 190℃ after molding.

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