阅读说明：本技术 一种高击穿场强的储能薄膜及其制备方法 (Energy storage thin film with high breakdown field strength and preparation method thereof ) 是由 张永泉 姚安权 张昌海 迟庆国 张天栋 冯宇 张月 于 2021-06-17 设计创作，主要内容包括：本发明公开了一种高击穿场强的储能薄膜及其制备方法,属于高性能储能薄膜材料制备技术领域。本发明解决了现有制备的储能薄膜击穿场强低、性能调控过程复杂以及储能密度低下等技术问题。本发明通过分层退火的方式,实现了高退火温度下的极化层叠加低退火温度下的耐压层,成功制备了具有电学性能的铁电薄膜。相较于现有离子掺杂、调控退火温度等现有解决手段相比,该薄膜结构设计方案,极大地降低了制备工艺的操作难度以及能源消耗,更加贴近工业生产并显著提高了储能密度。(The invention discloses an energy storage thin film with high breakdown field strength and a preparation method thereof, belonging to the technical field of preparation of high-performance energy storage thin film materials. The invention solves the technical problems of low breakdown field strength, complex performance regulation and control process, low energy storage density and the like of the existing prepared energy storage film. According to the invention, the polarization layer at high annealing temperature is superposed with the pressure-resistant layer at low annealing temperature in a layered annealing mode, and the ferroelectric film with electrical property is successfully prepared. Compared with the existing solutions of ion doping, annealing temperature regulation and the like, the film structure design scheme greatly reduces the operation difficulty and energy consumption of the preparation process, is more close to industrial production and obviously improves the energy storage density.)

1. The energy storage thin film with high breakdown field strength is characterized by comprising a crystallization layer and an amorphization layer, wherein the thickness of the thin film is 200-700nm, and the thickness ratio of the crystallization layer to the amorphization layer is 1: (1-5).

2. The energy storage thin film with high breakdown field strength as claimed in claim 1, wherein the thickness of the crystallized layer is 40-230nm, and the thickness of the amorphized layer is 60-670 nm.

3. The energy storage film with high breakdown field strength of claim 1, wherein the film is a lead zirconate antiferroelectric film.

4. A method for preparing an energy storage thin film with high breakdown field strength according to claim 1, comprising the following steps:

step 1, preparing a first layer of film by a gas phase method or a liquid phase method, wherein the thickness of the first layer of film is required to meet the thickness requirement of a crystallization layer, and then performing high-temperature annealing treatment to obtain the crystallization layer film;

and 2, coating a second layer of film on the surface of the crystallized layer film obtained in the step 1 by adopting a vapor deposition method or a liquid phase method, wherein the thickness of the second layer of film is required to meet the thickness requirement of the non-crystallized layer, then performing low-temperature annealing treatment, and preparing the non-crystallized layer film on the surface of the crystallized layer film to obtain the energy storage film with high breakdown field strength.

5. The method as claimed in claim 4, wherein the temperature of the high temperature annealing in step 1 is 650-750 ℃.

6. The method as claimed in claim 4, wherein the temperature of the low-temperature annealing in step 2 is 400-650 ℃.

7. The method for preparing an energy storage thin film with high breakdown field strength as claimed in claim 4, wherein the annealing atmosphere in step 1 and step 2 is oxygen, and the flow rate is 0.2-0.7L/min.

8. The method for preparing an energy storage thin film with high breakdown field strength according to claim 4, wherein the thin film prepared by the vapor deposition method is magnetron sputtering or chemical vapor deposition.

9. The method for preparing an energy storage thin film with high breakdown field strength as claimed in claim 4, wherein the liquid phase method is a sol-gel spin coating method.

10. The method of claim 4 is applied to prepare the lead zirconate-based energy storage film with high breakdown field strength. The preparation process comprises the following steps:

step one, carrying out heat treatment on lead acetate trihydrate for 0.5-2h at the temperature of 60-180 ℃, and adding the lead acetate trihydrate into the mixture according to the volume ratio of (6-8): 1, taking ethylene glycol and methyl ether as solvents, taking a plurality of drops of acetic acid as cosolvent, magnetically stirring for 1-2h at the normal temperature under the condition of the rotating speed of 350-450r/min, cooling to the room temperature, adding a zirconium n-propoxide solution, continuously stirring, filtering and aging for 24h to obtain lead zirconate sol with the concentration of 0.2-0.6 mol/L;

step 2, dripping the lead zirconate sol obtained in the step 1 on a substrate, spreading glue solution under the condition of the rotating speed of 500-5500r/min, then homogenizing the glue under the condition of the rotating speed of 3500-5500r/min, and transferring the glue solution onto a flat heater to heat and primarily remove the solvent;

step 3, repeating the step 2 until the thickness of the film reaches 40-230nm, and annealing the film to obtain a crystallized layer film;

the annealing treatment conditions are as follows: the atmosphere is oxygen, the flow rate of the oxygen is 0.2-0.7L/min, the temperature is raised to 650 plus 750 ℃ under the condition of the speed of 20-50 ℃/min, and the temperature is preserved for 2-7 min;

step 4, continuously dripping lead zirconate sol obtained in the step 1 on the surface of the crystallized layer film obtained in the step 3, spreading glue solution under the condition of the rotating speed of 500-;

step 5, repeating the step 2 until the thickness of the film reaches 200-700nm, carrying out annealing treatment, preparing an amorphous layer film on the surface of the crystallized layer film, and obtaining the energy storage film with high breakdown field strength;

the annealing treatment conditions are as follows: the atmosphere is oxygen, the flow rate of the oxygen is 0.2-0.7L/min, the temperature is raised to 400-650 ℃ at the speed of 20-50 ℃/min, and the temperature is kept for 2-7 min.

Technical Field

The invention relates to an energy storage film with high breakdown field strength and a preparation method thereof, belonging to the technical field of preparation of high-performance energy storage film materials.

Background

The dielectric capacitor has faster charge-discharge rate (ns) and higher power density (up to 108W/kg), and can meet the requirements of ultra-high power electronics and systems such as hybrid electric vehicles, medical defibrillators, satellites and the like. However, further development and application of dielectric capacitors are severely limited by low energy density. In recent years, due to the excellent characteristics of small thickness, few defects, moderate energy storage density and the like of the film materials, researchers gradually shift the eyesight from the block materials to the film materials.

For a dielectric capacitor such as an Antiferroelectric (AFE) material, increasing the breakdown field strength can further increase the storage density significantly. The existing methods for improving the breakdown field intensity comprise active introduction of ion doping, increase of film thickness, regulation of crystallization temperature, increase of heterojunction and the like, but the preparation process is complicated, so that the time cost and the preparation cost of the preparation are increased undoubtedly, and therefore, the energy storage film structure with high breakdown field intensity and the preparation method thereof are necessary, which can ensure that a larger breakdown electric field is improved on the basis of certain polarization intensity and greatly improve the energy storage density of the film.

Disclosure of Invention

The invention provides a novel energy storage thin film structure and a preparation method thereof, aiming at solving the technical problems of low breakdown field strength, complex performance regulation and control process, low energy storage density and the like of the existing prepared energy storage thin film.

The technical scheme of the invention is as follows:

an energy storage film with high breakdown field strength comprises a crystallization layer and an amorphization layer, the thickness of the film is 200-700nm, the thickness ratio of the crystallization layer to the amorphization layer is 1: (1-5).

Further limit, the thickness of the crystallization layer is 40-230nm, and the thickness of the non-crystallization layer is 60-670 nm.

Further, the thickness of the crystallized layer and the thickness of the amorphized layer are both 60-120 nm.

Further defined, the film thickness is 200-300 nm.

Further, the film is a lead zirconate anti-ferroelectric film.

A preparation method of the energy storage film with high breakdown field strength comprises the following steps:

step 1, preparing a first layer of film by a gas phase method or a liquid phase method, wherein the thickness of the first layer of film is required to meet the thickness requirement of a crystallization layer, and then performing high-temperature annealing treatment to obtain the crystallization layer film;

and 2, coating a second layer of film on the surface of the crystallized layer film obtained in the step 1 by adopting a vapor deposition method or a liquid phase method, wherein the thickness of the second layer of film is required to meet the thickness requirement of the non-crystallized layer, then carrying out low-temperature annealing treatment, and preparing the non-crystallized layer film on the surface of the crystallized layer film to obtain the energy storage film with high breakdown field strength.

Further defined, the temperature of the high temperature annealing in the step 1 is 650-750 ℃.

Further limiting, the temperature of the low-temperature annealing in the step 2 is 400-650 ℃.

Further limiting, the annealing atmosphere in the step 1 and the step 2 is oxygen, and the flow rate is 0.2-0.7L/min.

Further, the film prepared by the vapor deposition method is magnetron sputtering or chemical vapor deposition.

Further limited, the liquid phase method for preparing the film is a sol-gel spin coating method.

Further, the annealing method includes, but is not limited to, a rapid annealing furnace, and may also be a muffle furnace, a vacuum annealing furnace, a tube furnace, and the like.

The method for preparing the lead zirconate-based energy storage film with high breakdown field strength comprises the following specific steps:

step 1, carrying out heat treatment on lead acetate trihydrate at the temperature of 60-180 ℃ for 0.5-2h, and adding the lead acetate trihydrate into the mixture according to the volume ratio of (6-8): 1, taking ethylene glycol and methyl ether as solvents, taking a plurality of drops of acetic acid as cosolvent, magnetically stirring for 1-2h at the normal temperature under the condition of the rotating speed of 350-450r/min, cooling to the room temperature, adding a zirconium n-propoxide solution, continuously stirring, filtering and aging for 24h to obtain lead zirconate sol with the concentration of 0.2-0.6 mol/L;

step 2, dripping the lead zirconate sol obtained in the step 1 on a substrate, spreading the colloid at the rotation speed of 500-5500r/min, homogenizing the colloid at the rotation speed of 3500-5500r/min, and transferring the colloid onto a flat heater to heat and primarily remove the solvent;

step 3, repeating the step 2 until the thickness of the film reaches 40-230nm, and annealing the film to obtain a crystallized layer film;

the annealing treatment conditions are as follows: the atmosphere is oxygen, the flow rate of the oxygen is 0.2-0.7L/min, the temperature is raised to 650 plus 750 ℃ under the condition of the speed of 20-50 ℃/min, and the temperature is preserved for 2-7 min;

step 4, continuously dripping lead zirconate sol obtained in the step 1 on the surface of the crystallized layer film obtained in the step 3, spreading colloid under the condition of the rotating speed of 500-;

step 5, repeating the step 2 until the thickness of the film reaches 200-700nm, carrying out annealing treatment, preparing an amorphous layer film on the surface of the crystallized layer film, and obtaining the energy storage film with high breakdown field strength;

the annealing treatment conditions are as follows: the atmosphere is oxygen, the flow rate of the oxygen is 0.2-0.7L/min, the temperature is raised to 400-650 ℃ at the speed of 20-50 ℃/min, and the temperature is kept for 2-7 min.

Further defined, the substrate was dried for 1h using an air-blast drying oven after being sonicated for 15min using absolute ethanol before use and heated for 5min in a flat heater.

The invention has the following beneficial effects: according to the invention, the crystallization layer is formed at a high annealing temperature in a layered annealing mode, the low-temperature annealing is continued on the surface of the crystallization layer to form the non-crystallization layer, and the thickness ratio of the crystallization layer to the non-crystallization layer is regulated and controlled, so that the film realizes a larger improvement of a breakdown electric field on the basis of ensuring a certain polarization intensity, and the energy storage density of the film is greatly improved. In addition, the invention also has the following advantages:

(1) the process is simple, the annealing temperature does not need to be further finely regulated, the method is close to the industrial production level, and the development and application of the high-energy-storage-density dielectric capacitor are promoted;

(2) the method carries out high-temperature annealing on the film close to the substrate side to form a crystallization layer, provides the film with polarization capability under a lower electric field, improves the charge storage capability of the film under a low field, and continuously stores charges under a high electric field;

(3) according to the invention, the film with a certain thickness is continuously prepared on the crystallization layer film, and the annealing is completed at a lower crystallization temperature to form the amorphous layer, so that the voltage resistance of the film under a high electric field is provided, the integral breakdown field strength is obviously improved, and meanwhile, the further expansion of leakage current is limited to a certain extent by introducing a new interface;

(4) the crystallized layer and the amorphous layer belong to the same medium, so that the interface affinity is good, and the interlayer stress is small;

(5) the annealing temperature of the film is reduced, so that the energy loss in the preparation process of the film is reduced, the problem of product yield caused by volatilization of elements of the film is also reduced, and the integral energy storage density of the film is further improved.

Drawings

FIG. 1 is a comparative XRD plot of PZO thin film samples 1-5 obtained in example 1;

FIG. 2 is an SEM photograph of PZO thin film samples 1-5 obtained in example 1, wherein (a) - (e) correspond to samples 1-5 in this order;

FIG. 3 is a comparative graph of polarization curves of PZO thin film samples 1-5 obtained in example 1;

FIG. 4 is a graph comparing the energy storage density curves of PZO thin film samples 1-5 obtained in example 1;

FIG. 5 is a graph comparing the energy storage efficiency curves of PZO thin film samples 1-5 obtained in example 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The experimental procedures used in the following examples are conventional unless otherwise specified. The materials, reagents, methods and apparatus used, unless otherwise specified, are conventional in the art and are commercially available to those skilled in the art.

Example 1:

firstly, 2.5261g of lead acetate trihydrate (with the excess of 10%) is put in an oven at 125 ℃ to remove crystal water for 1h, the lead acetate trihydrate is transferred into a conical flask, then 15.3ml of ethylene glycol monomethyl ether is added as a solvent, 2ml of acetic acid is used as a cosolvent, the mixture is stirred for 2h at the rotation speed of 350r/min under the normal temperature magnetic force, then cooled to the room temperature, 2.7ml of zirconium n-propoxide solution is added, and the stirring is continued for 2h at the rotation speed of 350 r/min. Then filtering and aging for 24h by using filter paper with a pore size of 0.22 mu m to obtain lead zirconate sol of 0.3 mol/L.

Secondly, carrying out ultrasonic treatment for 15min, acetone wiping, drying in a blast oven and heating at 400 ℃ for 3min in advance to remove stress treated Pt (111)/Ti/SiO₂Dripping 8-11 drops of lead zirconate colloid obtained in the first step on a Si (100) substrate, homogenizing the colloid for 15s at a low rotating speed of 800r/min, thinning the colloid for 10s at a high rotating speed of 4000r/min to obtain a film with the thickness of 60nm, and then transferring the film to a flat heater to heat for 5min at 400 ℃ to remove the solvent.

And thirdly, operating the steps for m times, transferring the film to a rapid annealing furnace, raising the temperature to 700 ℃ at the heating rate of 30 ℃/s, and annealing the film for 180s in the oxygen atmosphere at the flow rate of 0.5L/min to obtain the crystallized layer film.

And fourthly, continuously dropwise adding colloid on the film, carrying out spin coating for n times by the operation of the third step, and carrying out annealing treatment at the annealing temperature of 550 ℃ under the same condition to obtain the PZO film.

When m was 4 times and n was 0 times, the obtained PZO thin film was designated as sample 1.

When m was 3 times and n was 1 time, the obtained PZO thin film was designated as sample 2.

When m was 2 times and n was 2 times, the obtained PZO thin film was designated as sample 3.

When m was 1 and n was 3, the obtained PZO thin film was designated as sample 4.

When m was 0 times and n was 4 times, the obtained PZO thin film was designated as sample 5.

The films of samples 1-5 above were characterized and tested for performance, and the results are shown in FIGS. 1-4.

As shown in FIG. 1, as the number n of low-temperature annealing layers increases, the (110) orientation becomes gradually weaker, and the pyrochlore phase of the film gradually increases, which shows that the film gradually has impure phases as the thickness of the amorphous layer increases.

As shown in FIG. 2, the pores on the surface of the film gradually decrease with the increase of the number n of the low-temperature annealing layers, wherein the surface of the film is the most dense when m is 1 and n is 3, and the deterioration begins with the increase of the number of the low-temperature annealing layers, which indicates that an amorphous layer with a certain thickness contributes to the improvement of the compactness of the film.

As shown in fig. 3, the polarization of the thin film gradually decreases as the number n of low-temperature annealing layers increases, but the breakdown field strength of the thin film gradually increases because the amorphous layer has a low dielectric constant and a low degree of polarization, and is subjected to a higher electric field strength, so that the breakdown field strength of the entire thin film increases.

As shown in fig. 4, when m is 1 and n is 3, the energy storage density of the thin film is significantly increased, because the crystallized layer and the amorphous layer with a certain thickness ratio are combined, the breakdown field strength of the whole thin film is increased, the polarization degree of the whole thin film is also increased, and the energy storage density is integrally increased.

As shown in fig. 5, when m is 1 and n is 3, the energy storage efficiency of the thin film is maintained at 55% or more, which is because the linear energy storage ratio is gradually increased and the charge-discharge efficiency is improved to a certain extent due to the increase of the thickness of the amorphous layer thin film.

Example 2:

first, 1.79919g of lead acetate trihydrate (excess 10%) were placed in an oven at 125 ℃ to remove the water of crystallization for 1h and transferred to an Erlenmeyer flask. Adding 11.6ml of ethylene glycol monomethyl ether as a solvent and 1ml of acetic acid as a cosolvent, stirring at the normal temperature and the rotation speed of 350r/min for 2h by magnetic force, cooling to the room temperature, adding 1ml of zirconium n-propoxide solution and 0.7ml of tetrabutyl titanate solution, and continuing stirring at the rotation speed of 350r/min for 2 h. Then filtering by using filter paper with a pore size of 0.22 mu m and aging for 24 hours to obtain the PZT sol with the concentration of 0.3 mol/L.

Secondly, carrying out ultrasonic treatment for 15min, acetone wiping, drying in a blast oven and heating at 400 ℃ for 3min in advance to remove stress treated Pt (111)/Ti/SiO₂Dripping 8-11 drops of lead zirconate titanate colloid on a Si (100) substrate, thinning the colloid for 10s at a low rotating speed of 800r/min and a high rotating speed of 4000r/min, and transferring the colloid to a flat heater to heat for 5min at 400 ℃ to remove the solvent.

And thirdly, repeating the steps until the thickness of the film is 180nm, transferring the film to a rapid annealing furnace, raising the temperature to 700 ℃ at the heating rate of 30 ℃/s, and annealing the film for 180s in an oxygen atmosphere at the flow rate of 0.5L/min.

And fourthly, continuously dropwise adding colloid to the film, carrying out spin coating in the same step until the thickness of the film is 240nm, and carrying out treatment at 550 ℃ as an annealing temperature under the same conditions as the three phases of the step to obtain the PZT film.

Example 3:

firstly, 2.4755g of lead acetate trihydrate (with the excess of 10%) and 0.0520g of lanthanum nitrate are put in an oven at 125 ℃ to remove crystal water for 1h, the mixture is transferred into an erlenmeyer flask, 15.3ml of ethylene glycol monomethyl ether is added to be used as a solvent, 2ml of acetic acid is used as a cosolvent, the mixture is stirred at the normal temperature for 2h at the rotating speed of 350r/min by magnetic force, then the mixture is cooled to the room temperature, 2.7ml of zirconium n-propoxide solution is added, and the stirring is continued for 2h at the rotating speed of 350 r/min. After filtering by using filter paper with a pore size of 0.22 mu m and aging for 24 hours, 0.3mol/L PLZO-2 sol is obtained.

Secondly, performing advanced ultrasonic treatment for 15min, acetone wiping, drying in a blast oven and heating at 400 ℃ for 3min to remove stress treatment on Pt (111)/Ti/SiO₂Dripping 8-11 drops of lead zirconate colloid on a Si (100) substrate, thinning the colloid for 10s at a low rotating speed of 800r/min and a high rotating speed of 4000r/min, and transferring the colloid on a flat heater to heat for 5min at 400 ℃ to remove the solvent.

And thirdly, repeating the steps until the thickness of the film is 180nm, transferring the film to a rapid annealing furnace, raising the temperature to 700 ℃ at the heating rate of 30 ℃/s, and annealing the film for 180s in an oxygen atmosphere at the flow rate of 0.5L/min.

And fourthly, continuously dropwise adding colloid to the film, carrying out spin coating in the same step until the thickness of the film is 240nm, and obtaining the PLZO-2 film by taking 550 ℃ as an annealing temperature under the same condition with the three phases in the step.

Compared with the existing implementation means, the energy storage thin film structure design scheme with high breakdown field strength and high polarization degree, provided by the invention, has the advantages that the preparation time is obviously reduced, the operation difficulty and the raw material waste are reduced, the preparation process is simple, the energy loss is low, the breakdown field strength and the energy storage promotion are obvious, and a thought is provided for preparing a high energy storage density thin film later.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.