Preparation method of a high-temperature and high-energy storage dielectric film based on porphyrin crosslinker-modified polyimide
By introducing an ultra-low content of TAPP crosslinking agent into the polyimide film to form a covalent crosslinking network and adding porphyrin traps, the problems of charge migration and leakage current of aromatic polyimides at high temperatures are solved, thereby improving the energy storage performance with high energy density and high efficiency at high temperatures.
Patent Information
- Application Number
- CN202610414336.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-31
- Publication Date
- 2026-05-26
AI Technical Summary
Existing aromatic polyimides exhibit a sharp increase in free carrier concentration and leakage current under high temperature and high electric field conditions, resulting in a rapid decline in charge and discharge efficiency. It is difficult to achieve both high energy density and high efficiency at temperatures above 200°C.
Using ultra-low content of 5,10,15,20-tetra(4-aminophenyl)porphyrin (TAPP) as a crosslinking agent, a covalent crosslinking network was formed with polyamic acid (PAA), and a porphyrin large π conjugated ring was introduced as a deep-level charge trap to construct an amorphous polyimide high-temperature dielectric film.
It significantly improves the breakdown strength and energy storage performance of the film at high temperatures. The breakdown field strength and discharge energy density are increased by 58% and 2.1 times respectively at 200℃, while maintaining high charge and discharge efficiency and dielectric loss of less than 0.015.
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Figure CN122080467A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer dielectric energy storage materials technology, specifically relating to a high energy storage density and high charge-discharge efficiency polymer film modified with ultra-low content porphyrin crosslinking agent for high temperature (150°C to 200°C) operation and its preparation method. Background Technology
[0002] With the development of high-end equipment in aerospace, oil and gas exploration, and new energy vehicles towards higher temperatures, smaller sizes, and higher power, the demand for film capacitors that can operate stably in extreme environments of 150~250℃ is becoming increasingly urgent. Aromatic polyimide (PI) is considered the preferred matrix material for high-temperature dielectrics due to its excellent thermal stability, mechanical strength, and insulation properties.
[0003] However, traditional aromatic polyimides in the existing technology have an inherent defect: under the combined action of high temperature and high electric field, the free carrier concentration of the aromatic PI backbone increases sharply, the leakage current increases significantly, and the charge and discharge efficiency decays rapidly, making it difficult to achieve both high energy density and high efficiency at temperatures above 200°C.
[0004] To suppress charge migration, current main modification strategies include introducing wide-bandgap inorganic nanofillers or organic semiconductor molecules. Existing high-temperature PI dielectric modification techniques have significant drawbacks: (1) Inorganic nanofiller composites: are prone to agglomeration, have poor interfacial compatibility, cause electric field distortion and local defects, and have difficulty in ensuring high-temperature stability; (2) Physical doping of small organic molecules: uneven dispersion, easy migration and precipitation, inability to form stable deep traps, and poor long-term effectiveness; (3) Traditional chemical crosslinking: high content of crosslinking agent and excessive stacking of molecular chains, which leads to increased film brittleness and decreased film-forming properties.
[0005] Furthermore, traditional crosslinking agents only play a single structural crosslinking role and lack functional design for charge trap engineering. The constructed network cannot actively capture charge carriers and has limited ability to suppress high-temperature charge migration.
[0006] Therefore, designing a crosslinking strategy with ultra-low load that can achieve both structural crosslinking and trap engineering (localization of charge) to suppress charge movement at the molecular level and improve high-temperature breakdown strength and energy storage efficiency has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention
[0007] This invention aims to solve the technical problems of low energy storage density and poor charge-discharge efficiency of existing polyimide dielectrics at high temperatures. It provides a method for preparing polyimide high-temperature energy storage dielectric films modified with ultra-low content porphyrin crosslinking agent. Using TAPP as the crosslinking agent, it achieves the dual functions of "covalent crosslinked network structure + deep-level charge trap introduction". It significantly improves the high-temperature energy storage performance at 200℃ with an ultra-low content of 0.1wt%, and the process is simple and suitable for large-scale production.
[0008] Technical solution
[0009] Material composition An ultra-low loading porphyrin crosslinked polyimide high-temperature dielectric film is composed of a polyimide matrix and a 5,10,15,20-tetra(4-aminophenyl)porphyrin (TAPP) crosslinking agent; the mass fraction of TAPP is 0.01wt%-20wt%, with an optimal mass of 0.1wt%; the polyimide is prepared by polycondensation-thermal imidization of pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA).
[0010] Structural features (1) The amino groups of TAPP form a covalent cross-linked network with the polyamic acid (PAA) chain ends, which inhibits charge migration; (2) The porphyrin large π conjugated ring acts as a deep-level electron trap, and the LUMO is completely localized in the TAPP unit, strongly binding the charge carriers; (3) The material has an amorphous structure, the chain spacing is increased, and the glass transition temperature T g ≥250℃, 5% thermogravimetric temperature T 5% ≥570℃; (4) The gel content is ≥80%, the mechanical strength and modulus are improved simultaneously, and the structure is stable under high temperature field strength.
[0011] Core performance (1) 25℃: Breakdown field strength 741 MV / m, discharge energy density 8.78 J / cm 3 Efficiency: 90% (2) 150℃: Breakdown field strength 612 MV / m, discharge energy density 6.01 J / cm 3 Efficiency: 90% (3) 200℃: Breakdown field strength 475 MV / m, discharge energy density 4.97 J / cm 3 Efficiency ≥ 85%; (4) Dielectric loss at 1 kHz tan d <0.015, extremely low leakage current.
[0012] Preparation method (1) Dissolve ODA in DMF, add PMDA in an ice-water bath, and stir at low temperature for 24 hours under nitrogen protection to obtain PAA precursor solution; (2) Dissolve TAPP in a small amount of DMF, add PAA solution at 0.01-20 wt%, and continue stirring for 24 h until the reaction is complete; (3) After degassing, the coating is applied to a glass substrate and heated at 80°C for 4 hours to complete the pre-crosslinking; (4) Gradient thermal imidization: 100℃ / 3h→200℃ / 2h→250℃ / 1h→300℃ / 1h; (5) Demolding in water and drying at 110°C for 12 hours to obtain cross-linked polyimide film (PCPI).
[0013] Innovation Mechanism (1) Covalent crosslinking: The four amino groups at the end of TAPP undergo amidation reaction with the anhydride groups at the end of PAA to form a stable chemical crosslinking network, which inhibits charge migration from the source.
[0014] (2) Porphyrin macrocycle deep trap: TAPP's large π conjugated porphyrin ring has a suitable energy level structure, which can be used as a deep energy level charge trap to effectively capture injected carriers, improve migration activation energy, and significantly reduce high-temperature leakage current and dielectric loss.
[0015] (3) Synergistic effect of ultra-low content: Only 0.1wt% content can achieve efficient control, no agglomeration, no interface defects, maintain film toughness and uniformity, and take into account both high breakdown strength and high energy storage density.
[0016] Beneficial effects
[0017] (1) Synergistic effect: TAPP molecules play a dual role. The outer amino groups and polyamic acid chains form a strong chemical cross-linking network, which restricts chain segment movement and fundamentally inhibits charge migration; its electron-rich large π-conjugated porphyrin macrocycle acts as an intrinsic deep-level charge trap, which can effectively localize charge carriers, increase the activation energy of charge migration, and further reduce high-temperature conduction loss.
[0018] (2) Ultra-low load and high efficiency modification: Only a very low content (e.g., 0.1 wt%) of TAPP is needed to achieve significant performance improvement, avoiding the problems of agglomeration, interface defects and mechanical property deterioration caused by high load fillers, and maintaining the good processability and flexibility of the system.
[0019] (3) Excellent high-temperature energy storage performance: The optimized thin film (PCPI-0.1) prepared by this method exhibits high discharge energy density (Ua) at room temperature, 150°C and 200°C. d ) and high efficiency ( orSpecifically, at 200°C, its breakdown strength reaches 475 MV / m, a 58% improvement over unmodified PI (300 MV / m); the discharge energy density reaches 4.97 J / cm². 3 The efficiency remained above 85%, which was 2.1 times and 1.5 times that of unmodified PI, respectively.
[0020] (4) Adjustable performance and good stability: By adjusting the content of TAPP, the dielectric constant of the film can be non-monotonically adjusted while maintaining extremely low dielectric loss (tan t). d <0.015). Attached Figure Description
[0021] Figure 1 This invention relates to the method for preparing TAPP-modified PI films. Figure 2 These are the energy storage test results of the TAPP modified thin film prepared according to the present invention at 200 degrees Celsius; Figure 3 These are the breakdown test results of the TAPP modified film prepared according to the present invention at room temperature, 150°C and 200°C; Figure 4 These are the energy storage test results of the TAPP modified thin film prepared according to the present invention at room temperature, 150°C and 200°C; Figure 5 These are the room temperature dielectric constant and dielectric loss test results of the TAPP modified thin film prepared according to the present invention. Detailed Implementation
[0022] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.
[0023] Example 1: PCPI-0.01 film 1. Dissolve ODA (8g, 40mmol) in 60mL LDM under nitrogen protection and stir until completely dissolved.
[0024] 2. The reaction system was placed in an ice-water bath, and stoichiometric amounts of PMDA (8.812 g, 40.4 mmol) were added gradually. The mixture was stirred continuously at low temperature for 24 hours to obtain a polyamic acid (PAA) precursor solution.
[0025] 3. Add 0.01wt% TAPP, which is pre-dissolved in 0.5ml LDM, and continue stirring for 12h after adding dropwise.
[0026] 4. Continue stirring for more than 20 hours to ensure that TAPP reacts fully with the residual anhydride groups at the ends of the PAA chains, resulting in a homogeneous and viscous mixed solution.
[0027] 5. After degassing the solution, cast it onto a clean glass substrate using a doctor blade (200μm gap).
[0028] 6. The wet film is first heat-treated at 80°C for 4 hours, and then subjected to stepwise thermal imidization: 100°C / 3h, 200°C / 2h, 250°C / 1h, 300°C / 1h.
[0029] 7. After the process is completed, allow it to cool naturally, peel the film off the substrate, and vacuum dry it at 110°C for 12 hours to obtain the final cross-linked polyimide film PCPI-0.01.
[0030] Example 2: PCPI-0.05 film The preparation steps are the same as in Example 1, except that the TAPP content is changed to 0.05wt%.
[0031] Example 3: PCPI-0.1 film (optimal) The preparation steps are the same as in Example 1, except that the TAPP content is changed to 0.1 wt%.
[0032] Example 4: PCPI-0.5 film The preparation steps are the same as in Example 1, except that the TAPP content is changed to 0.5wt%.
[0033] Example 5: PCPI-1 film The preparation steps are the same as in Example 1, except that the TAPP content is changed to 1 wt%.
[0034] Example 6: PCPI-10 film The preparation steps are the same as in Example 1, except that the TAPP content is changed to 10wt%.
[0035] Example 7: PCPI-20 film The preparation steps are the same as in Example 1, except that the TAPP content is changed to 20 wt%. Comparative example: Pure PI film Without TAPP, the remaining steps are exactly the same as in Example 1 to prepare a pure PI film.
[0036] Dielectric property testing of modified materials
[0037] The DC breakdown strength of the dielectric film of the present invention was measured at room temperature, 150 °C and 200 °C using a voltage breakdown tester (BDJC-50 kV, Beijing Beiguang Precision Instruments). The discharge energy density was measured at 200 °C using a unipolar waveform with a period of 0.01 s using PolyK (PK-WGCM20, LLC State College, PA.USA).
[0038] Dielectric and Breakdown Properties: At 1 kHz, the dielectric constant of the PCPI film exhibits a non-monotonic change, first decreasing and then increasing, with PCPI-0.1 showing the lowest dielectric constant (3.08). The dielectric loss of all samples was below 0.015. Breakdown strength tests show that PCPI-0.1 achieves breakdown strengths of 741, 612, and 475 MV / m at room temperature, 150°C, and 200°C, respectively, representing a significant improvement over pure PI (547, 414, and 300 MV / m), especially at 200°C where the improvement reaches 58%.
[0039] Energy storage performance: Optimized PCPI-0.1 film discharge energy density (Ua) at room temperature, 150°C, and 200°C. d The values reached 8.78 J / cm² respectively. 3 ( or =90%), 6.09 J / cm 3 ( or =90%), 4.97 J / cm 3 ( or =85%), which are 1.6, 1.8 and 2.1 times that of pure PI, respectively. Compared with high-temperature polymer dielectrics reported in the existing literature, the material of the present invention exhibits excellent energy density at 200°C.
Claims
1. A method for preparing a polyimide high-temperature energy storage dielectric film modified with an ultra-low content porphyrin crosslinking agent, characterized in that, Includes the following steps: (1) The diamine monomer is dissolved in a polar aprotic solvent, and the dianhydride monomer is added under nitrogen protection and low temperature conditions. The mixture is stirred and polycondensed to obtain a polyamic acid (PAA) solution. (2) Add ultra-low content TAPP crosslinking agent to PAA solution and continue stirring until fully reacted to obtain crosslinked PAA coating solution; (3) Degas the coating liquid, coat it evenly, and then perform gradient thermal imidization treatment. After cooling and demolding, TAPP crosslinked polyimide dielectric film (PCPI) is obtained.
2. The preparation method according to claim 1, characterized in that, In step (1): the diamine monomer is 4,4'-diaminodiphenyl ether (ODA); the dianhydride monomer is pyromellitic dianhydride (PMDA); the molar ratio of ODA to PMDA is 1:1.0~1.
2.
3. The preparation method according to claim 1, characterized in that, In step (1): the polar aprotic solvent is N,N-dimethylformamide (DMF); the solid content of the PAA solution is 10~20wt%; the low-temperature polycondensation temperature is 0~5℃; and the stirring time is 20~28h.
4. The preparation method according to claim 1, characterized in that, In step (2): the content of the TAPP crosslinking agent is 0.01-20wt% of the total mass of PAA solids, but the film with a content greater than 1wt% is brittle. Therefore, the optimal content range is 0.01-1wt%, and the optimal content is 0.1wt%.
5. The preparation method according to claim 1, characterized in that, In step (2): TAPP is dissolved in a small amount of DMF before being added to PAA solution, and the mixture is stirred at room temperature for 20-24 hours until the reaction is complete.
6. The preparation method according to claim 1, characterized in that, In step (3): the gradient thermal imidization process is: 80℃, 4h→100℃, 3h→200℃, 2h→250℃, 1h→300℃, 1h.
7. The preparation method according to claim 1, characterized in that, The prepared PCPI-0.1 film meets the following requirements at 200℃: breakdown strength ≥ 470 MV / m; discharge energy density ≥ 4.9 J / cm². 3 Charge / discharge efficiency ≥85%; 5% thermogravimetric temperature ≥570℃; glass transition temperature ≥250℃; dielectric loss tan δ <0.
015.
8. A TAPP crosslinked polyimide dielectric film prepared by the method of any one of claims 1 to 7.
9. The application of the dielectric thin film according to claim 8 in 200°C high-temperature thin film capacitors, aerospace power systems, oil and gas exploration downhole electronic equipment, and vehicle-mounted power devices.