CN114759253A - Preparation method of ultra-thin, light and high-mechanical-strength PEO-based solid electrolyte with cellulose membrane as supporting layer - Google Patents

Abstract

The invention relates to a preparation method of an ultrathin, light and high-mechanical-strength PEO-based solid electrolyte with a cellulose membrane as a supporting layer, which is characterized in that a cellulose membrane is introduced as the supporting layer, and the ultrathin, light and high-mechanical-strength PEO-based solid electrolyte membrane is prepared by simple coating and hot-pressing technologies. The surface of the cellulose membrane has a large number of hydroxyl groups, so that the compatibility of the cellulose membrane with PEO can be improved. Making it one of the most desirable support layers for PEO-based solid electrolytes. Compared with the traditional PEO-based solid electrolyte, the PEO-based solid electrolyte with the cellulose membrane as the supporting layer has extremely excellent mechanical property and electrochemical property in ultrathin thickness, and the assembled battery has high rate capability and high cycle performance, thereby being beneficial to realizing high energy density of the lithium battery. The PEO-based solid electrolyte prepared by the method has the advantages of cost advantage and simple operation, and is suitable for industrial production.

Description

Preparation method of ultra-thin, light-weight, high-mechanical-strength PEO-based solid electrolyte with cellulose membrane as support layer

technical field

The invention belongs to the technical field of lithium battery materials, and relates to a preparation method of an ultra-thin, light-weight and high-mechanical-strength PEO-based solid electrolyte with a cellulose film as a support layer.

Background technique

Due to the rapid development of portable devices and electric vehicles, current lithium batteries cannot meet future demands in terms of energy density, cycle life, and safety. By using a solid electrolyte in combination with a lithium metal negative electrode, it can not only improve the energy density, but also alleviate the safety problems caused by traditional liquid electrolytes. Polymer electrolytes composed of polymer matrix and lithium salts have the advantages of flexibility, light weight, good interfacial compatibility with electrodes, and easy mass production, and have better development prospects in practical applications. Among them, polyacetylene oxide (PEO) and solid electrolytes have been widely studied due to their good solubility of lithium salts and their stability with lithium metal anodes.

However, the mechanical strength of PEO itself is not enough to suppress the growth of lithium dendrites well, making it unsuitable for high areal capacity cathodes. Therefore, the thickness of the currently used PEO solid electrolyte is relatively thick, which is not conducive to achieving high energy density. In order to improve the ability of PEO-based solid electrolytes to suppress Li dendrites in relatively thin cases, this problem is usually ameliorated by adding a support layer to PEO-based electrolytes. The currently used support layers mainly include cross-linked polymer scaffolds, inorganic inert scaffolds and commonly used commercial separators. However, the ionic conductivity of the cross-linked polymer scaffold is low, the thickness of the inorganic inert support layer is still thick, and the density is high, which is not conducive to the realization of high energy density. Its lack of compatibility with solid electrolytes hinders the rapid transfer of lithium ions to a certain extent. Therefore, the ideal support layer should have the characteristics of flexibility, light weight, ultra-thinness, easy processing, good compatibility with PEO, and thermal stability. As an abundant, sustainable and inexpensive material, cellulose is simple to process, has excellent flexibility, relatively good thermal stability, light weight and high porosity. At the same time, there are a large number of hydroxyl groups on its surface, which can improve its compatibility with PEO, making it a possibility. Among various types of cellulose, Cladophora Cellulose (CC) is characterized by its high crystallinity, which makes it difficult to absorb water and retains its porous structure after drying. Therefore, we believe that Cladophora Cellulose (CC) can be used as a suitable support layer to prepare high mechanical properties, ultrathin, lightweight, and thermally stable PEO-based electrolytes, thereby improving the energy density of all-solid-state lithium metal batteries.

SUMMARY OF THE INVENTION

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention proposes a method for preparing an ultra-thin, light-weight, high-mechanical-strength PEO-based solid electrolyte with a cellulose film as a support layer, using the ultra-thin cellulose film as a support layer, An ultrathin PEO-based solid electrolyte with flexible, lightweight, thermally stable and high mechanical properties was prepared.

Technical solutions

A method for preparing an ultra-thin, light-weight, high-mechanical-strength PEO-based solid electrolyte with a cellulose film as a support layer, characterized in that the steps are as follows:

Step 1: Disperse the Cladophora Cellulose raw material evenly in the aqueous solution as the precursor solution;

Step 2: vacuum filtration and drying of the obtained precursor solution;

Step 3: Mix and stir PEO, LiTFSI and LLZTO in acetonitrile to obtain a PEO-based solid electrolyte slurry; wherein the proportion of LLZTO is 20%, and the ratio of PEO and LiTFSI is [EO/Li+]=16: 1;

Step 4: The slurry of PEO-based solid electrolyte is coated on both sides of Cladophora Cellulose by a coating machine and dried; the drying process is first at room temperature for 12 hours, and then in a vacuum oven at 60 degrees for 12 hours;

Step 5: hot-pressing the dried PEO-based solid electrolyte to obtain an ultra-thin, light-weight, high-mechanical-strength PEO-based solid electrolyte with a cellulose film as a support layer; the hot-pressing pressure is 40 MPa, and the hot-pressing temperature is 70 degrees , the hot pressing time is 10-30min.

In the step 1: the Cladophora Cellulose raw material is dispersed in an aqueous solution by an ultrasonic wall breaker; the power of the ultrasonic wall breaker is 650W; and the dispersion time is 10-30min.

In the step 2: the drying temperature is 100 degrees, and the time is 12 hours.

The stirring time of the step 3 is 12 hours.

In the step 4: the coating scale of the PEO-based solid electrolyte slurry is 15-35.

beneficial effect

The method for preparing an ultra-thin, light-weight, high-mechanical-strength PEO-based solid electrolyte with a cellulose membrane as a support layer proposed by the present invention uses a cellulose diaphragm as a support layer, and through simple coating and hot pressing technology, thereby A PEO-based solid electrolyte membrane with ultrathin, light weight and high mechanical strength was prepared. PEO-based solid electrolytes hinder practical applications due to insufficient mechanical properties at ultrathin thicknesses. As a material with abundant reserves, strong sustainability and low price, cellulose membrane is simple to process, has excellent flexibility, relatively good thermal stability, light weight and high porosity. At the same time, there are a large number of hydroxyl groups on its surface, which can improve its compatibility with PEO. This makes it one of the most ideal support layers for PEO-based solid electrolytes. Therefore, compared with the traditional PEO-based solid electrolyte, the PEO-based solid electrolyte with cellulose membrane as the support layer exhibits extremely excellent mechanical and electrochemical properties at ultra-thin thickness, and the assembled battery has high rate performance and High cycle performance is conducive to the realization of high energy density of lithium batteries. The PEO-based solid electrolyte prepared by the method has cost advantages, simple operation, and is suitable for industrial production.

The thickness of PEO-based solid electrolytes is a key issue hindering the achievement of high energy density, which can only be achieved with solid electrolytes with low specific gravity. The flexible, thermally stable, lightweight and high-porosity CladophoraCellulose can realize the ultrathin, lightweight, flexible and high mechanical strength requirements of PEO-based solid electrolytes. At the same time, a large number of hydroxyl groups on the surface of cellulose membrane can improve its compatibility with PEO and improve the electrochemical performance of PEO-based solid electrolyte to a certain extent. Combining the above characteristics, the preparation of ultra-thin, flexible, light-weight, and high-mechanical-strength PEO-based solid electrolytes can be realized, which is beneficial to the realization of high energy density of all-solid-state lithium metal batteries.

Therefore, using Cladophora Cellulose as a support layer to prepare an ultra-thin, light-weight, high-mechanical-strength PEO-based solid electrolyte to improve mechanical and electrochemical properties, so that the assembled battery has high rate performance and high cycle performance, which is beneficial to The realization of high energy density of lithium batteries.

Description of drawings

Fig. 1 is the SEM image of the ultrathin, light weight, high mechanical strength PEO-based solid electrolyte with the cellulose film obtained in Example 1, Comparative Example and Comparative Example 2 of the present invention as a support layer;

a: the thickness of Example 2 is 15 μm; b, the thickness of Comparative Example 1 is 25 μm; c, the thickness of Comparative Example 2 is 35 μm;

Figure 2 shows the ultra-thin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolytes (15 μm, 25 μm, 35 μm) with different thicknesses prepared in Example 2, Comparative Example 1, and Comparative Example 2 of the present invention and the comparative example 3. Comparison of tensile properties of the obtained traditional PEO-based solid electrolytes, i.e., stress-strain curves;

Figure 3 shows the ultra-thin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolytes (15 μm, 25 μm, 35 μm) with different thicknesses prepared in Example 2, Comparative Example 1, and Comparative Example 2 of the present invention and the comparative example 3 Comparison of critical current densities of the obtained traditional PEO-based solid electrolytes;

4 is a comparison of the ionic conductivity of the PEO-based solid electrolyte with the cellulose membrane obtained in Example 2 of the present invention as a support layer, which is ultra-thin, lightweight, and high mechanical strength, and the traditional PEO-based solid electrolyte obtained in Comparative Example 3;

5a is the lithium ion migration number of the ultra-thin, light-weight, high-mechanical-strength PEO-based solid electrolyte obtained by the cellulose film obtained in Example 2 of the present invention; ion migration number;

6 is a cycle performance comparison of the ultra-thin, light-weight, high mechanical strength PEO-based solid electrolyte with the cellulose film obtained in Example 2 of the present invention as a support layer and the traditional PEO-based solid electrolyte obtained in Comparative Example 3;

7 is a comparison of the rate performance of the ultra-thin, lightweight, high mechanical strength PEO-based solid electrolyte with the cellulose film obtained in Example 2 of the present invention as a support layer and the traditional PEO-based solid electrolyte obtained in Comparative Example 3;

Detailed ways

The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

The invention discloses a preparation method of an ultra-thin, light-weight and high-mechanical-strength PEO-based solid electrolyte with a cellulose membrane as a support layer. Ultrathin, flexible, and high mechanical strength PEO-based solid electrolyte membranes were fabricated by simple coating and hot pressing techniques. The flexible, thermally stable, lightweight and high-porosity Cladophora Cellulose can realize the ultrathin, lightweight, flexible and high mechanical strength requirements of PEO-based solid electrolytes. At the same time, a large number of hydroxyl groups on the surface of cellulose membrane can improve its compatibility with PEO and improve the electrochemical performance of PEO-based solid electrolyte to a certain extent. Combining the above characteristics, the preparation of ultra-thin, flexible, light-weight, and high-mechanical-strength PEO-based solid electrolytes can be realized, which is beneficial to the realization of high energy density of all-solid-state lithium metal batteries. At the same time, considering the characteristics of abundant cellulose reserves, strong sustainability, low price, and simple processing, the PEO-based solid electrolyte prepared by this method has a cost advantage, is simple to operate, and is suitable for industrial production. In view of this, the present invention is proposed.

The present invention provides an ultra-thin, light-weight, flexible, thermally stable, high-mechanical-strength PEO-based solid electrolyte, which is achieved by the following steps:

Step 1. The Cladophora Cellulose raw material is uniformly dispersed in the aqueous solution by an ultrasonic wall breaker; the power of the ultrasonic wall breaker is 650W; the dispersion time is 10-30min;

Step 2, drying the obtained precursor solution after vacuum filtration, the drying temperature is 100 degrees, and the time is 12 hours;

Step 3. Mix and stir a certain proportion of PEO, LiTFSI and LLZTO in acetonitrile to obtain a PEO-based solid electrolyte slurry; the proportion of LLZTO is 20%, and the proportion of PEO and LiTFSI is [EO/Li+] =16:1, stirring time is 12 hours;

Step 4. Coat the slurry of PEO-based solid electrolyte on both sides of Cladophora Cellulose by a coating machine and dry; the coating scale of the slurry of PEO-based solid electrolyte is 15-35; the drying process is 12 hours at room temperature, Then vacuum oven at 60 degrees for 12 hours;

Step 5, hot pressing the dried PEO-based solid electrolyte; the hot pressing pressure is 40MPa, the hot pressing temperature is 70 degrees, and the hot pressing time is 10-30min.

Example 2

Step 1. Disperse 20mg of Cladophora Cellulose raw material uniformly in the aqueous solution through an ultrasonic breaker; the power of the ultrasonic breaker is 650W; the dispersion time is 30min;

Step 2, drying the obtained precursor solution after vacuum filtration, the drying temperature is 100 degrees, and the time is 12 hours;

Step 3. Mix and stir 520 mg of PEO, 212 mg of LiTFSI and 183 mg of LLZTO in 10 ml of acetonitrile to obtain a PEO-based solid electrolyte slurry; the stirring time is 12 hours;

Step 4. Coat the slurry of PEO-based solid electrolyte on both sides of Cladophora Cellulose through a coating machine and dry; the coating scale of the slurry of PEO-based solid electrolyte is 25; the drying process is first at room temperature for 12 hours, and then vacuum Oven at 60 degrees for 12 hours;

Step 5, hot pressing the dried PEO-based solid electrolyte; the hot pressing pressure is 40 MPa, the hot pressing temperature is 70 degrees, and the hot pressing time is 15 minutes.

SEM characterization:

The ultra-thin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolyte prepared in Example 2 of the present invention was characterized by SEM. The results are shown in Figure 1. It can be seen that the thickness of the prepared PEO-based solid electrolyte is about is 25μm;

Mechanical property test

The ultra-thin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolytes (15 μm, 25 μm, 35 μm) prepared in Example 2, Comparative Example 1, and Comparative Example 2 of the present invention with different thicknesses were obtained from Comparative Example 3. The traditional PEO-based solid electrolyte was subjected to stress-strain test. The results are shown in Figure 2. It can be observed that the mechanical properties of the ultra-thin, lightweight, flexible, thermally stable, and high mechanical strength PEO-based solid electrolyte prepared in Example 2 have been obtained. greatly improved;

Critical Current Density Test

The ultra-thin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolytes (15 μm, 25 μm, 35 μm) prepared in Example 2, Comparative Example 1, and Comparative Example 2 of the present invention with different thicknesses were obtained from Comparative Example 3. The traditional PEO-based solid electrolyte was tested for critical current density. The results are shown in Figure 3. It can be observed that the ultra-thin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolyte prepared in Example 1 Ratio 3 has higher critical current density and lower overpotential, and at the same time comprehensively tests the critical current density, overpotential and mechanical properties, the comprehensive performance of Example 2 is the most excellent;

Ionic Conductivity Test

The ultra-thin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolyte prepared in Example 2 of the present invention and the traditional PEO-based solid electrolyte obtained in Comparative Example 1 were tested for ionic conductivity, and the results are shown in Figure 4. , it can be observed that the ultrathin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolyte prepared in Example 2 has higher ionic conductivity;

Lithium Ion Migration Number Test

The ultrathin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolyte prepared in Example 2 of the present invention was tested for lithium ion migration number, and the results are shown in Figure 5a; the traditional PEO-based solid electrolyte obtained in Comparative Example 1 The solid electrolyte was tested for lithium ion migration number, and the results are shown in Figure 5b; it can be observed that the ultra-thin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolyte prepared in Example 1 has a higher lithium ion Ion mobility number (0.56);

Electrochemical performance test

The ultra-thin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolyte obtained in Example 2 of the present invention, the traditional PEO-based solid electrolyte obtained in Comparative Example 1, LiFePO ₄ positive electrode and lithium metal negative electrode were assembled into a button battery The electrochemical performance test was carried out. The results are shown in Figures 6 and 7. The ultra-thin, lightweight, flexible, thermally stable, and high mechanical strength PEO-based solid electrolyte prepared in Example 2 has better cycle performance and rate performance.

Comparative Example 1

Step 1. Disperse 30mg of Cladophora Cellulose raw material uniformly in the aqueous solution through an ultrasonic breaker; the power of the ultrasonic breaker is 650W; the dispersion time is 30min;

Step 2, drying the obtained precursor solution after vacuum filtration, the drying temperature is 100 degrees, and the time is 12 hours;

Step 3. Mix and stir 520 mg of PEO, 212 mg of LiTFSI and 183 mg of LLZTO in 10 ml of acetonitrile to obtain a PEO-based solid electrolyte slurry; the stirring time is 12 hours;

Step 4. Coat the slurry of PEO-based solid electrolyte on both sides of Cladophora Cellulose by a coating machine and dry it; the coating scale of the slurry of PEO-based solid electrolyte is 35; the drying process is first at room temperature for 12 hours, and then vacuum Oven at 60 degrees for 12 hours;

Step 5, hot pressing the dried PEO-based solid electrolyte; the hot pressing pressure is 40 MPa, the hot pressing temperature is 70 degrees, and the hot pressing time is 25 minutes.

Comparative Example 2

Step 1. Disperse 15mg of Cladophora Cellulose raw material uniformly in the aqueous solution through an ultrasonic breaker; the power of the ultrasonic breaker is 650W; the dispersion time is 30min;

Step 2, drying the obtained precursor solution after vacuum filtration, the drying temperature is 100 degrees, and the time is 12 hours;

Step 3. Mix and stir 520 mg of PEO, 212 mg of LiTFSI and 183 mg of LLZTO in 10 ml of acetonitrile to obtain a PEO-based solid electrolyte slurry; the stirring time is 12 hours;

Step 4. Coat the slurry of PEO-based solid electrolyte on both sides of Cladophora Cellulose by a coating machine and dry it; the coating scale of the slurry of PEO-based solid electrolyte is 15; the drying process is first at room temperature for 12 hours, and then vacuum Oven at 60 degrees for 12 hours;

Step 5, hot pressing the dried PEO-based solid electrolyte; the hot pressing pressure is 40 MPa, the hot pressing temperature is 70 degrees, and the hot pressing time is 10 min.

Comparative Example 3

Step 1. Mix and stir 520 mg of PEO, 212 mg of LiTFSI and 183 mg of LLZTO in 10 ml of acetonitrile to obtain a PEO-based solid electrolyte slurry; the stirring time is 12 hours;

Step 2, pouring the obtained PEO-based solid electrolyte slurry onto a polytetrafluoroethylene mold, drying at room temperature for 12 hours, and drying in a vacuum at 60 degrees for 12 hours;

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention.

From Example 2, Comparative Example 1 and Comparative Example 2, it can be seen that the ultrathin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolyte prepared by the present invention has a thickness of about 25 μm. The comprehensive performance of electrical conductivity and critical current density is good. From Example 1 and Comparative Example 3, it can be seen that the ultra-thin, lightweight, flexible, thermally stable, high mechanical strength PEO-based solid electrolyte (25 μm thick) prepared by the present invention has With better mechanical properties, ionic conductivity, lithium ion migration number and critical current density, the assembled battery has better cycle performance and rate capability. Combining the above advantages, the electrolyte membrane is beneficial to the realization of high energy density of all-solid-state lithium metal batteries.

The foregoing has shown and described the basic principles and main features of the present invention, as well as the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (5)

1. a cellulose film is as the preparation method of the ultrathin, lightweight, high mechanical strength PEO-based solid electrolyte of support layer, it is characterized in that step is as follows: Step 1: Disperse the Cladophora Cellulose raw material evenly in the aqueous solution as the precursor solution; Step 2: vacuum filtration and drying of the obtained precursor solution; Step 3: Mix and stir PEO, LiTFSI and LLZTO in acetonitrile to obtain a PEO-based solid electrolyte slurry; wherein the proportion of LLZTO is 20%, and the ratio of PEO and LiTFSI is [EO/Li+]=16: 1; Step 4: The slurry of PEO-based solid electrolyte is coated on both sides of Cladophora Cellulose by a coating machine and dried; the drying process is first at room temperature for 12 hours, and then in a vacuum oven at 60 degrees for 12 hours; Step 5: hot-pressing the dried PEO-based solid electrolyte to obtain an ultra-thin, light-weight, high-mechanical-strength PEO-based solid electrolyte with a cellulose film as a support layer; the hot-pressing pressure is 40 MPa, and the hot-pressing temperature is 70 degrees , the hot pressing time is 10-30min. 2. cellulose membrane according to claim 1 is used as the preparation method of ultra-thin, lightweight, high mechanical strength PEO-based solid electrolyte of support layer, it is characterized in that: in described step 1: Cladophora Cellulose raw material is by ultrasonic breaker Disperse in aqueous solution; power of ultrasonic breaker is 650W; dispersion time is 10-30min. 3. cellulose film according to claim 1 is used as the preparation method of ultrathin, light, high mechanical strength PEO-based solid electrolyte of support layer, it is characterized in that: in described step 2: drying temperature is 100 degrees, time for 12 hours. 4. The method for preparing an ultra-thin, light-weight, high-mechanical-strength PEO-based solid electrolyte with a cellulose film as a support layer according to claim 1, wherein the stirring time in step 3 is 12 hours. 5. the preparation method of the ultra-thin, lightweight, high mechanical strength PEO-based solid electrolyte of the cellulose film according to claim 1, is characterized in that: in the step 4: the slurry of the PEO-based solid electrolyte The coating scale is 15-35.

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