阅读说明：本技术 柔性储能薄膜的制备方法 (Preparation method of flexible energy storage film ) 是由 冯雪 王志建 陈颖 于 2018-06-29 设计创作，主要内容包括：本发明涉及一种柔性储能薄膜的制备方法。所述制备方法包括：提供一柔性金属衬底；在所述柔性金属衬底上沉积形成钛酸锶薄膜预制层；对带有钛酸锶薄膜预制层的柔性金属衬底进行热处理得到钛酸锶层,从而得到柔性储能薄膜。该储能薄膜采用钛酸锶材料,通过该制备方法实现储能薄膜的柔性化。同时,制备得到的储能薄膜具有高介电常数、低介电损耗、高击穿场强和高储能密度,可以用作薄膜电容器的电介质材料。(The invention relates to a preparation method of a flexible energy storage film. The preparation method comprises the following steps: providing a flexible metal substrate; depositing a strontium titanate film prefabricated layer on the flexible metal substrate; and carrying out heat treatment on the flexible metal substrate with the strontium titanate film prefabricated layer to obtain a strontium titanate layer, thereby obtaining the flexible energy storage film. The energy storage film is made of strontium titanate material, and the energy storage film is flexible through the preparation method. Meanwhile, the prepared energy storage film has high dielectric constant, low dielectric loss, high breakdown field strength and high energy storage density, and can be used as a dielectric material of a film capacitor.)

1. A preparation method of a flexible energy storage film is characterized by comprising the following steps:

providing a flexible metal substrate;

depositing a strontium titanate film prefabricated layer on the flexible metal substrate;

and carrying out heat treatment on the flexible metal substrate with the strontium titanate film prefabricated layer to obtain a strontium titanate layer, thereby obtaining the flexible energy storage film.

2. The method for preparing the flexible energy storage film according to claim 1, wherein a strontium titanate film prefabricated layer is formed on the flexible metal substrate by deposition by a magnetron sputtering method by taking strontium titanate as a target material.

3. The preparation method of the flexible energy storage film according to claim 2, wherein the magnetron sputtering power is 50W-200W, and the deposition time is 1 min-60 min.

4. The method for preparing the flexible energy storage film according to claim 2, wherein the working atmosphere of the magnetron sputtering is argon, the flow rate of the argon is 30sccm to 120sccm, and the vacuum degree is 0.1Pa to 0.5 Pa.

5. The method for preparing the flexible energy storage film according to claim 1, wherein the thickness of the strontium titanate film prefabricated layer is 30 nm-3 μm, and the grain size is 10 nm-450 nm.

6. The method for preparing the flexible energy storage film according to claim 1, wherein oxygen is filled during the heat treatment, the flow rate of the oxygen is 30sccm to 150sccm, and the vacuum degree is 0.1Pa to 1 Pa.

7. The method for preparing the flexible energy storage film according to claim 1, wherein the temperature of the heat treatment is 300-600 ℃ and the time is 20-60 minutes.

8. The method for preparing the flexible energy storage film according to claim 1, wherein the thickness of the flexible metal substrate is 12 μm to 18 μm; and/or

The surface roughness of the flexible metal substrate is 0.4-0.8 μm; and/or

The surface tension of the flexible metal substrate is more than or equal to 60 dynes; and/or

The flexible metal substrate includes a copper foil.

Technical Field

The invention relates to the field of energy sources, in particular to a preparation method of a flexible energy storage film.

Background

With the gradual trend toward miniaturization, multi-functionality, and light weight of electronic devices, electronic components constituting the electronic devices also need to be developed toward miniaturization, light weight, high integration, and multi-functionality.

For a thin film capacitor, a desirable approach to achieve miniaturization is to increase the capacitance by increasing the dielectric constant of the dielectric thin film. The dielectric film mainly comprises a high-molecular energy storage film and a ceramic energy storage film, and in the traditional film capacitor, the used dielectric film is mainly the high-molecular energy storage film. Because the dielectric constant of the ceramic energy storage film is far higher than that of the polymer energy storage film, the ceramic energy storage film is used for replacing the polymer energy storage film, and the development trend of the film capacitor is met. However, ceramic energy storage films lack the flexibility of polymeric energy storage films.

Disclosure of Invention

Therefore, a preparation method of the flexible energy storage film is needed to solve the problem of insufficient flexibility of the ceramic energy storage film; the preparation method realizes the flexibility of the energy storage film, simultaneously enables the energy storage film to have high dielectric constant, low dielectric loss, high breakdown field strength and high energy storage density, and can be used as a dielectric material of a film capacitor.

A preparation method of a flexible energy storage thin film comprises the following steps:

providing a flexible metal substrate;

depositing a strontium titanate film prefabricated layer on the flexible metal substrate;

and carrying out heat treatment on the flexible metal substrate with the strontium titanate film prefabricated layer to obtain a strontium titanate layer, thereby obtaining the flexible energy storage film.

In one embodiment, strontium titanate is used as a target material, and a strontium titanate film prefabricated layer is deposited and formed on the flexible metal substrate by a magnetron sputtering method.

In one embodiment, the magnetron sputtering power is 50W-200W, and the deposition time is 1 min-60 min.

In one embodiment, the working atmosphere of the magnetron sputtering is argon, the flow rate of the argon is 30sccm to 120sccm, and the vacuum degree is 0.1Pa to 0.5 Pa.

In one embodiment, the thickness of the strontium titanate film prefabricated layer is 30 nm-3 μm, and the grain size is 10 nm-450 nm.

In one embodiment, oxygen is introduced during the heat treatment, the flow rate of the oxygen is 30sccm to 150sccm, and the vacuum degree is 0.1Pa to 1 Pa.

In one embodiment, the temperature of the heat treatment is 300-600 ℃ and the time is 20-60 minutes.

In one embodiment, the thickness of the flexible metal substrate is 12-18 μm; and/or

The surface roughness of the flexible metal substrate is 0.4-0.8 μm; and/or

The surface tension of the flexible metal substrate is more than or equal to 60 dynes; and/or

The flexible metal substrate includes a copper foil.

The invention adopts the flexible metal substrate to form the strontium titanate film on the flexible metal substrate, thereby not only realizing the flexibility of the ceramic energy storage film, but also having high preparation efficiency. Meanwhile, the prepared energy storage film has high dielectric constant, low dielectric loss, high breakdown field strength and high energy storage density, and can be used as a dielectric material of a film capacitor.

Drawings

FIG. 1 is a flow chart of a process for preparing a flexible energy storage thin film according to the present invention, wherein (a) is a flexible metal substrate, (b, c) is a strontium titanate thin film formed on the flexible metal substrate, and (d) is an electrode layer formed on the strontium titanate thin film;

fig. 2 is a schematic diagram of the energy storage thin films of example 1, example 10 and comparative example 1 of the present invention, in which (g) is the flexible energy storage thin film of example 1, (f) is the flexible energy storage thin film of example 10, and (e) is the strontium titanate energy storage thin film of comparative example 1.

Detailed Description

The preparation method of the flexible energy storage film provided by the invention is further explained below.

As shown in fig. 1, the preparation method of the flexible energy storage thin film provided by the invention comprises the following steps:

(a) providing a flexible metal substrate;

(b) depositing a strontium titanate film prefabricated layer on the flexible metal substrate by using a magnetron sputtering method by taking strontium titanate as a target material;

(c) carrying out heat treatment on the flexible metal substrate deposited with the strontium titanate film prefabricated layer to obtain a strontium titanate film; and

(d) and forming an electrode layer on the strontium titanate film to obtain the flexible energy storage film.

In the step (a), the flexible metal substrate is not limited to any material, as long as the flexible metal substrate has good flexibility, strong high-temperature oxidation resistance, conductivity and no reaction with the ceramic film, and the flexible metal substrate comprises one of Pt, Au, Ag, Cu, Ni, Ti and Al.

Considering that copper foil is the most cost-effective metal material in the field of electronics industry, its resistivity is 1.75X 10^-8Omega. m, second only to silver (1.65X 10)^-8Ω · m), a thermal conductivity 401W/(m · K), next to silver (420W/(m · K)), while the price of copper is much lower than that of silver. Secondly, industrial copper foil is mature, the copper foil is divided into rolled copper foil and electrolytic copper foil, and the rolled copper foil and the electrolytic copper foil are both subjected to electroplating treatment to prevent oxidation and high-temperature oxidation resistance, and cannot be oxidized when being calcined in air at 400-500 ℃. Therefore, the flexible metal substrate is preferably a copper foil.

Further, the rolled copper foil is composed of rod-shaped grains parallel to the surface of the copper foil and has superior bending resistance, and the electrolytic copper foil is composed of rod-shaped grains perpendicular to the surface of the copper foil and has lower bending resistance than the rolled copper foil, and therefore, the copper foil is preferably a rolled copper foil.

The thinner the flexible substrate is, the better the flexibility is, and therefore, the thickness of the flexible substrate is 12 to 18 μm, and more preferably, a rolled copper foil of 12 μm.

In the film capacitor, the flexible substrate is used as an electrode, the actual contact area of the strontium titanate film and the electrode is related to the surface roughness of the flexible substrate, and the larger the surface roughness is, the larger the actual contact area is, and the larger the capacitance value per unit geometric area is. However, the surface roughness of the flexible substrate is too large, which easily causes the generation of holes on the surface of the strontium titanate film and affects the energy storage performance of the flexible energy storage film. Therefore, the surface roughness of the flexible substrate is 0.4 μm to 0.8 μm.

The surface tension of the flexible substrate is more than or equal to 60 dynes, preferably more than 60 dynes, and the higher the surface tension of the flexible substrate is, the stronger the bonding force between the strontium titanate film and the flexible substrate is.

The surface activity can be increased by treating the surface of the flexible substrate, thereby increasing the surface tension. Preferably, the treatment method comprises the following steps: the method comprises the steps of heating a flexible substrate, setting the temperature to be 100-300 ℃, preserving heat for 10-30 minutes, and then processing the flexible substrate by using a Hall ion source, wherein the voltage of the Hall ion source is 800-2000V, the current is 0.5-2A, and the processing time is 1-10 min.

And (b) depositing a strontium titanate film prefabricated layer on the flexible metal substrate by adopting a magnetron sputtering process. The ions which spirally move at high speed under the action of an electric field and a magnetic field bombard the strontium titanate target material, and atoms or ion groups bombarded from the strontium titanate target material are deposited on the flexible metal substrate to form a strontium titanate film prefabricated layer. Because the magnetron sputtering particles have energy as high as 1eV to 10eV, and can maintain higher surface mobility on the surface of the flexible metal substrate, the formed strontium titanate film prefabricated layer has better crystallization performance and high deposition efficiency, the temperature of the flexible metal substrate required for forming the strontium titanate film prefabricated layer is lower, and the compatibility with an integration process is better.

Compared with PLD, sol-gel and hydrothermal methods and the like, the method for forming the strontium titanate film prefabricated layer on the flexible metal substrate by deposition through the magnetron sputtering process has the advantages of high deposition efficiency, good film forming crystallinity and the like, and is beneficial to improving the energy storage performance of the flexible energy storage film. And the whole process is a physical process, and oxygen cooling protection is not needed when film forming is finished, so that the flexible metal substrate is protected from being oxidized and has high conductivity.

If the compactness of the strontium titanate target material is not high, the surface and the inner air holes of the strontium titanate target material are more, and the strontium titanate target material is easy to generate microcracks under the action of high pressure and high temperature during magnetron sputtering, and the microcracks are expanded to cause the cracking of the strontium titanate target material. Therefore, the compactness of the strontium titanate target is preferably equal to or more than 96 percent, and more preferably more than 96 percent, so that the target is convenient for magnetron sputtering and works stably.

In the magnetron sputtering process, the working atmosphere of the magnetron sputtering is argon, the flow rate of the argon is 30 sccm-120 sccm, and the vacuum degree is 0.1 Pa-0.5 Pa. The magnetron sputtering power is 50W-200W, and the deposition time is 1 min-60 min.

Furthermore, the thickness of the deposited strontium titanate film prefabricated layer is 30 nm-3 μm, the grain size is 10 nm-450 nm, and the film structure is compact.

In the step (c), the flexible metal substrate deposited with the strontium titanate thin film pre-fabricated layer is subjected to a heat treatment, which is an annealing heat treatment. When annealing at 300-400 deg.C, SrTiO₃The Sr, Ti and O atoms in the ceramic can exchange energy with each other by virtue of lattice vibration, and some atoms in distorted positions can be restored to normal states, so that internal stress is correspondingly reduced. When annealing is carried out at 400 ℃ to 500 ℃, the mobility of Sr, Ti and O atoms is increased, so that some vacancies, interstitial atoms and dislocations which are originally frozen are recombined in the film, or move to the surface and the grain boundary to disappear, or are combined into defects with lower energyTrap configuration (e.g., dislocation loops, vacancy clusters, etc.). In this case, the internal stress of the film will be greatly reduced. When annealing is carried out at 500-600 ℃, the diffusion of Sr, Ti and O atoms is intensified, the frozen defects can be further eliminated, and various recrystallization can also occur, so that the grain boundary is reduced, and the internal stress of the film is obviously reduced. Preferably, the temperature of the heat treatment of the invention is 300-600 ℃ and the time is 20-60 minutes. By adopting annealing heat treatment at different temperatures and for different time, the non-equilibrium defects such as lattice mismatch, lattice reconstruction, impurities, phase change and the like in the strontium titanate film prefabricated layer disappear greatly, and the strontium titanate film is obtained. Compared with the strontium titanate film prefabricated layer, the internal stress of the strontium titanate film is obviously reduced.

Preferably, oxygen is introduced during the heat treatment, the flow rate of the oxygen is 30sccm to 150sccm, and the vacuum degree is 0.1Pa to 1 Pa. The oxygen can eliminate oxygen vacancy generated in the deposition process of the strontium titanate ceramic film, and can further reduce the defects of the strontium titanate ceramic film.

In the step (d), the electrode layer can be formed by deposition through a magnetron sputtering process, namely, the electrode layer is formed by deposition on the strontium titanate film through the magnetron sputtering process after the heat treatment, and the working efficiency is high.

Considering that the thinner the electrode layer is, the higher the sheet resistance of the electrode layer is, and correspondingly, the higher the voltage resistance of the electrode layer is; the thicker the electrode layer, the lower the sheet resistance of the electrode layer, and correspondingly, the higher the current resistance of the electrode layer. Moreover, the thinner the electrode layer, the more easily it is oxidized, resulting in a loss of capacity; the thicker the electrode layer is, the lower the voltage resistance of the electrode layer is, resulting in the electrode layer being easily broken down. Preferably, the thickness of the electrode layer is 100nm to 3 μm, and the sheet resistance of the electrode layer is 0.001 mOhm/□ to 0.5 Ohm/□.

Preferably, the material of the electrode layer includes at least one of copper, platinum, gold, silver, and aluminum, and is more preferably copper.

According to the invention, the flexible metal substrate is adopted, the strontium titanate film is formed on the flexible metal substrate through the magnetron sputtering process, and then the electrode layer is formed on the strontium titanate film to form the ceramic energy storage film, so that the ceramic energy storage film is not only flexible, but also high in preparation efficiency, good in microstructure such as crystallinity and grain size and low in internal stress, and the energy storage performance of the flexible energy storage film is improved.

The invention also provides a flexible energy storage film which comprises a flexible metal substrate, and a strontium titanate film and an electrode layer which are sequentially formed on the flexible metal substrate.

The thickness of the strontium titanate film is 10 nm-2 mu m, and the grain size is 30-500 nm; the thickness of the electrode layer is 100 nm-3 mu m.

The flexible metal substrate comprises a copper foil, and the thickness of the copper foil is 12-18 mu m; and/or

The surface roughness of the copper foil is 0.4-0.8 μm; and/or

The surface tension of the copper foil is not less than 60 dyne.

The minimum bending radius of the flexible energy storage film is 2-20 mm; and/or

The dielectric constant of the flexible energy storage film is 280-310; and/or

The dielectric loss of the flexible energy storage film is 0.003-0.05; and/or

The breakdown field strength of the flexible energy storage film is 1000 kV/cm-3000 kV/cm; and/or

The energy storage density of the flexible energy storage film is 12J/cm³～55J/cm³。

The energy storage film is composed of a flexible metal substrate, a strontium titanate material and an electrode layer, not only is the flexibility of the energy storage film realized, but also the energy storage film has high dielectric constant, low dielectric loss, high breakdown field strength and high energy storage density.

The invention also provides a film capacitor, which comprises the flexible energy storage film.

The flexible energy storage film provided by the invention is used for replacing a high polymer film, and the development of a film capacitor towards the trends of miniaturization, lightness, thinness, high integration and multiple functions can be promoted. Meanwhile, the film capacitor has the advantages of no polarity, high insulation resistance, excellent frequency characteristics (wide frequency response), small dielectric loss and the like. The method can be applied to a plurality of industries such as electronics, household appliances, communication, electric power, electrified railways, new energy vehicles, wind power generation, solar power generation and the like. Especially in the signal cross connection part, the thin film capacitor with good frequency characteristic and low dielectric loss of the invention can ensure that the signal is not distorted too much when being transmitted, and has good electrical performance and high reliability.

Hereinafter, the method for preparing the flexible energy storage film will be further described by the following specific examples.