A poly(p-xylene) thin film for high-temperature energy storage capacitors and its preparation method

Abstract

A poly(p-xylene) thin film for high-temperature energy storage capacitors and its preparation method are disclosed, as follows: a) Purifying three types of p-xylene dimers (N-type, C-type, and F-type); b) Placing the purified dimer powder into the sublimation zone of the feeding chamber, where it sublimates into a gas; c) After thorough mixing of the dimer gas and an inert gas, the inert gas carries it into the pyrolysis zone, where the CH2-CH2 bonds of the dimer break at high temperature, generating a high-temperature stable p-xylene diradical active monomer; d) Driven by the inert gas, it enters a low-temperature vacuum deposition zone, where it spontaneously polymerizes and deposits as a thin film on the surface of the substrate material. This invention employs chemical vapor deposition (CVD) and uses different types of p-xylene cyclic dimers as precursors to prepare different types of poly(p-xylene) thin films. The composition, structure, and thickness of the film can be controlled, resulting in a smooth surface and dense structure. It can be used on any substrate and can also be further modified to enhance the active interface.

Description

Technical Field

[0001] This invention relates to the field of high-temperature energy storage technology, and in particular to a poly(p-xylene) film for high-temperature energy storage capacitors and its preparation method. Background Technology

[0002] Dielectric capacitors are a special type of energy storage device that can completely release stored energy in an extremely short time (microseconds). Their high power and short-duration output make them widely used in high-pulse applications such as medical defibrillators and advanced electromagnetic systems. Furthermore, high-temperature operating fields such as aerospace electronics, automotive, and underground oil and gas exploration also show an urgent need for high-temperature resistant energy storage capacitors. Compared to brittle and difficult-to-process ceramic materials, the advantages of polymer dielectrics have been well-proven, including high breakdown strength, low mass density, low cost, flexibility, and ease of processing. Currently, mainstream capacitors use biaxially oriented polypropylene (BOPP) as the dielectric, but BOPP's maximum operating temperature is only 105℃, making it difficult to adapt to higher operating temperatures. Moreover, many polymer dielectrics are unstable at high temperatures, with losses increasing sharply and energy density decreasing as temperature rises, especially when the temperature reaches T0. g At these temperatures, the physical properties and mechanical performance drop sharply, making it unsuitable for high-temperature operation.

[0003] To obtain dielectric materials with higher temperature resistance, a common approach is to incorporate rigid structural units into the polymer backbone to prevent rotation and increase the backbone's stiffness. Additionally, side groups can physically restrict bond rotation; when the side groups are polar, the polar interactions further restrict rotation, increasing polymer stiffness and thus improving the material's high-temperature resistance.

[0004] The main chain of parylene itself contains a rigid benzene ring structure. The side group substitution of polar chlorine and fluorine atoms on the benzene ring can further improve the stiffness of the main chain, giving C-type and F-type parylene films better stiffness. As a result, it has better high-temperature resistance and energy storage performance than N-type parylene films, and can be well used in energy storage fields such as high-temperature energy storage capacitors.

[0005] Parylene films can be prepared by methods such as coating, plasma-enhanced deposition, chemical vapor deposition, and electrochemical deposition, but each method has some drawbacks. For example, films prepared by traditional electrochemical deposition have very low molecular weights and are not practical. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a parylene film for high-temperature energy storage capacitors and a method for preparing the same, involving the preparation of three types (Parylene N, Parylene C and Parylene F) parylene films: that is, using parylene cyclic dimers (N type), chlorinated parylene cyclic dimers (C type) and fluorinated parylene cyclic dimers (F type) as raw materials to prepare parylene films.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A type of parylene film for high-temperature energy storage capacitors includes three types: N-type, C-type, and F-type, with the following structural formulas:

[0009]

[0010] A method for preparing a parylene film for high-temperature energy storage capacitors is as follows:

[0011] a. Purify the three types of p-xylene dimers: N-type, C-type, and F-type;

[0012] b. Place the purified dimer powder into the sublimation zone of the feeding hopper and sublimate it into gas;

[0013] c. After the dimer gas and the inert gas are fully mixed, the inert gas carries it into the pyrolysis zone. At high temperature, the CH2-CH2 bond of the dimer breaks, generating a stable p-xylene diradical active monomer at high temperature.

[0014] d. Subsequently, propelled by an inert gas, it enters a low-temperature vacuum deposition zone, where it spontaneously polymerizes and deposits into a thin film on the surface of the substrate material.

[0015] The three types of p-xylene dimers in step a have the following structural formulas:

[0016]

[0017] In step b, the temperature of the sublimation zone is controlled at 150–170°C.

[0018] In step b, the pressure in the sublimation zone is controlled at 0.5–1 mbar.

[0019] The inert gas in step c includes argon;

[0020] In step c, the temperature in the pyrolysis zone is controlled at 600–700°C.

[0021] In step c, the pressure in the pyrolysis zone is controlled at 0.1–0.2 mbar.

[0022] In step d, the temperature of the deposition zone is controlled between -40 and 60°C.

[0023] In step d, the pressure in the deposition zone is controlled at 0.02–0.05 mbar.

[0024] In step d, the substrate material is a silicon wafer or an aluminum substrate.

[0025] Advantages of this invention:

[0026] 1. Different types of para-xylene cyclodimers can be used as precursors to prepare different types of para-xylene films; the operation is convenient and there are no byproducts.

[0027] 2. The main chain of parylene contains a rigid benzene ring structure, which gives N-type parylene films good temperature resistance. The side group substitution of polar chlorine and fluorine atoms on the benzene ring can further improve the rigidity of the main chain, giving C-type and F-type parylene films better high-temperature resistance than N-type parylene films.

[0028] 3. The present invention uses chemical vapor deposition (CVD) to control the composition, structure and thickness (from hundreds of nanometers to tens of micrometers). The resulting film process is adjustable, the film thickness is controllable, the surface is smooth and the structure is dense. It can be used on any substrate and can also be further modified to modify the active interface.

[0029] 4. The thin film prepared by the method of the present invention has excellent high temperature resistance and excellent dielectric properties. It is a good linear dielectric at both room temperature and high temperature (100°C) and has high energy storage capacity. It can be used in the field of high temperature energy storage capacitors. Attached Figure Description

[0030] Figure 1 shows a schematic diagram of the preparation process of three types of parylene films;

[0031] Figure 2(a) shows the energy storage density of the parylene film at room temperature under different electric field strengths; Figure 2(b) shows the charge-discharge efficiency spectra of the parylene film at room temperature under different electric field strengths.

[0032] Figure 3(a) shows the energy storage density of the parylene film at 70℃ under different electric field strengths; Figure 3(b) shows the charge-discharge efficiency spectra of the parylene film at 70℃ under different electric field strengths.

[0033] Figure 4(a) shows the energy storage density of the parylene film at 100℃ under different electric field strengths; Figure 4(b) shows the charge and discharge efficiency spectra of the parylene film at 100℃ under different electric field strengths. Detailed Implementation

[0034] The invention will be further explained below with reference to the schematic diagram.

[0035] This invention employs chemical vapor deposition to produce three types of thin films—N-type, C-type, and F-type—by changing the type of raw materials; and controls the final film thickness by controlling the content of the raw materials.

[0036] Commonly used thicknesses were selected to prepare N-type, C-type, and F-type parylene films with a thickness of 15 μm; to investigate the effect of thickness, a C-type parylene film with a thickness of 10 μm was also prepared.

[0037] Example 1

[0038] This embodiment uses N-type p-xylene cyclic dimer as raw material to provide a method for preparing N-type poly(p-xylene) thin film, as shown in Figure 1(a), and the steps are as follows:

[0039] a. Purify 35g of N-type p-xylene dimer;

[0040] b. Place the purified dimer powder into the sublimation zone of the feeding hopper, where it sublimates into gas; set the temperature of the sublimation zone to 160℃ and the pressure to 0.5mbar.

[0041] c. After the dimer gas and the inert gas are thoroughly mixed, the inert gas carries the mixture into the pyrolysis zone. The temperature of the pyrolysis zone is 650℃ and the pressure is 0.1mbar. At high temperature, the CH2-CH2 bond of the dimer breaks, generating a stable p-xylene diradical active monomer at high temperature.

[0042] d. Subsequently, driven by an inert gas, it enters a low-temperature vacuum deposition zone with a temperature of 20°C and a chamber pressure of 0.02 mbar, where it spontaneously polymerizes and deposits into a thin film on the surface of the substrate material; the resulting film is a Parylene N material with a thickness of 15 μm.

[0043] The specific experimental steps are as follows:

[0044] I. Preparatory Work

[0045] (1) Clean all chambers, platforms and pipes in the sublimation zone, high-temperature pyrolysis zone and deposition zone of the entire thin film preparation device. Wipe with distilled water and then wipe with ethanol and lint-free cloth to ensure a clean preparation environment.

[0046] (2) Turn on the power switch of the device, set the temperature of the sublimation zone to 160℃ and the pressure to 0.5mbar; set the temperature of the pyrolysis zone to 650℃ and the pressure to 0.1mbar; set the temperature of the deposition zone to 20℃ and the chamber pressure to 0.02mbar.

[0047] (3) Weigh 35g of N-type p-xylene cyclodimer powder raw material, place it on clean tin foil, put the tin foil containing the raw material into the feed pipe of the sublimation zone, and put the cleaned silicon wafer substrate into the deposition zone.

[0048] (4) Perform a pre-evacuation operation on the device: first evacuate the air to a pressure of 3 mbar, then release the air to 10 mbar, and repeat this operation twice.

[0049] II. Preparation

[0050] A third evacuation is performed. When the pressure in the chamber reaches 0.5 mbar, the sublimation and pyrolysis zones are adjusted to the heating state, and the preparation begins.

[0051] III. Preparation Completed

[0052] After the deposition process is completed, wait for the chamber temperature to cool to below 45°C, then turn off the instrument; slowly release the gas intermittently and remove the substrate; the resulting film is a Parylene N material with a thickness of 15 μm.

[0053] Example 2

[0054] This example provides a method for preparing a C-type parylene film, as shown in Figure 1(b). Unlike Example 1, this example uses C-type parylene cyclodimer as the raw material. All other preparatory work, operating procedures, and parameter settings are the same as in Example 1. The resulting film is a Parylene C material with a thickness of 15 μm.

[0055] Example 3

[0056] This example provides a method for preparing F-type parylene thin films, as shown in Figure 1(c). Unlike Example 1, this example uses F-type parylene cyclic dimer as the raw material. All other preparatory work, operating procedures, and parameter settings are the same as in Example 1. The resulting film is a 15 μm thick Parylene F material.

[0057] Example 4

[0058] This example provides a method for preparing a C-type parylene film. Unlike Example 1, the raw material used in this example is a C-type parylene cyclic dimer. Unlike Example 2, only 25g of the raw material is weighed in this example. All other preparatory work, operating procedures, and parameter settings are the same as in Example 1. The resulting film is a ParyleneC material with a thickness of 10μm.

[0059] The films obtained in the four embodiments above were subjected to relevant tests, as shown in Figures 2, 3, and 4. The parylene films prepared by this method exhibit good energy storage performance: at 70°C, the energy storage density of both C-type and F-type films remains at 3 J / cm³.3 @400MV / m and above, under the same conditions, BOPP (1.6J / cm) 3 It is twice as fast as other capacitors, and its charge and discharge efficiency remains above 80%. It also maintains good stability at 100℃ (the charge and discharge efficiency is still above 60% at 400MV / m), making it well-suited for energy storage applications such as high-temperature energy storage capacitors.

Claims

1. A method for preparing a parylene film for high-temperature energy storage capacitors, characterized in that, Specifically as follows: a. Purify the three types of p-xylene dimers: N-type, C-type, and F-type; b. Place the purified dimer powder into the sublimation zone of the feeding hopper and sublimate it into gas; c. After the dimer gas and the inert gas are fully mixed, the inert gas carries it into the pyrolysis zone. At high temperature, the CH2-CH2 bond of the dimer breaks, generating a stable p-xylene diradical active monomer at high temperature. d. Subsequently, propelled by an inert gas, it enters a low-temperature vacuum deposition zone, where it spontaneously polymerizes and deposits as a thin film on the substrate material surface; including three types: N-type, C-type, and F-type, with the following structural formulas: The three types of p-xylene dimers in step a have the following structural formulas: In step b, the temperature of the sublimation zone is controlled at 150–170°C. In step b, the pressure in the sublimation zone is controlled at 0.5 mbar. The inert gas in step c includes argon; In step c, the temperature in the pyrolysis zone is controlled at 600–700°C. In step c, the pressure in the pyrolysis zone is controlled at 0.1 mbar. In step d, the temperature of the deposition zone is controlled between -40 and 60°C. In step d, the pressure in the deposition zone is controlled at 0.02 mbar; In step d, the substrate material is a silicon wafer or an aluminum substrate.

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