Composite solid electrolyte, preparation method and sodium ion battery

Abstract

The invention relates to a composite solid electrolyte, a preparation method and a sodium ion battery, and belongs to the field of sodium batteries. The composite solid electrolyte comprises the following components in parts by mass: 70-90 parts of a polymer matrix, 1-15 parts of sodium salt and 1-15 parts of silicon dioxide nanoparticles. In the composite solid electrolyte disclosed by the invention, the silicon dioxide nanoparticles can adsorb PF6 <->, so that the dissociation of NaPF6 and the release amount of free sodium ions are promoted, and the improvement of ionic conductivity is facilitated.

Description

Technical Field

[0001] The invention relates to a composite solid electrolyte, a preparation method and a sodium ion battery, and belongs to the field of sodium batteries. Background Art

[0002] Faced with the huge energy storage market, people have vigorously developed lithium battery systems, but the current lithium battery system has certain limitations. In terms of resources, the current lithium resource reserves are relatively low, and there are problems such as difficulty in mining and high cost. In terms of application, lithium batteries, especially ternary material batteries, have problems such as low cycle life, insufficient safety, high cost and slow charging speed. Based on this, sodium-ion batteries have been proposed for their many advantages such as low cost and high safety performance. Despite this, the development of lithium batteries provides basic conditions for the development of sodium-ion batteries, such as research and development, materials can be referenced, and even some materials and equipment can be used interchangeably.

[0003] Electrolyte is the core part of battery operation. Organic liquid electrolytes are widely used in sodium-ion batteries. This type of electrolyte has the advantages of high ion conductivity and good wetting performance, but it still has problems such as poor processing performance, poor cycle performance and the formation of poor SEI film. Therefore, the research and development technology, preparation and application of sodium-ion solid electrolytes have attracted much attention. However, the combination of organic and inorganic materials to form a composite solid electrolyte is considered to be the most effective electrolyte at present, but the ion transport mechanism and electrochemical performance depend on factors such as the type and structure of the material. Sodium-ion batteries have no resource limitations and are cost-effective. Therefore, the development of highly safe, low-cost, and high-performance sodium-ion battery electrolytes is crucial for their commercial application. Summary of the invention

[0004] In view of the shortcomings of the prior art, one of the purposes of the present invention is to provide a composite solid electrolyte with high ion conductivity; the second purpose of the present invention is to provide a method for preparing a composite solid electrolyte; the third purpose of the present invention is to provide a sodium ion battery

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A composite solid electrolyte comprises, by weight, 70-90 parts of a polymer matrix, 1-15 parts of a sodium salt and 1-15 parts of silicon dioxide nanoparticles.

[0007] Furthermore, the composite solid electrolyte comprises 75-85 parts of a polymer matrix, 3-12 parts of a sodium salt and 3-12 parts of silicon dioxide nanoparticles.

[0008] Furthermore, the composite solid electrolyte includes 78-82 parts of a polymer matrix, 5-10 parts of a sodium salt and 5-10 parts of silicon dioxide nanoparticles.

[0009] Further, the polymer matrix includes PVDF. Optionally, the weight average molecular weight of the PVDF is 500000-1500000 g / mol.

[0010] Furthermore, the sodium salt includes sodium hexafluorophosphate.

[0011] Furthermore, the particle size of the silicon dioxide nanoparticles is 1-100 nm, further 10-90 nm, and further 15-85 nm.

[0012] Based on the same inventive concept, the present invention also provides: a method for preparing the composite solid electrolyte as described above, comprising the following steps:

[0013] S1, mixing the polymer matrix and the organic solvent in a mass ratio of 1:3-5 to obtain a polymer solution;

[0014] S2, dispersing sodium salt and silicon dioxide nanoparticles in the polymer solution to obtain a slurry;

[0015] S3. Dry the slurry under vacuum at 60-80° C. for 12-36 hours to obtain a composite solid electrolyte.

[0016] Furthermore, the organic solvent is NN-dimethylformamide.

[0017] Further, in S2, sodium hexafluorophosphate, silicon dioxide nanoparticles and the polymer solution are mixed, and stirred at a rate of 600-700 rpm for 20-24 hours to obtain a slurry.

[0018] Based on the same inventive concept, the present invention also provides: a sodium ion battery, comprising the composite solid electrolyte as described above or the composite solid electrolyte prepared by the preparation method as described above.

[0019] Optionally, the sodium ion battery further comprises a positive electrode sheet and a negative electrode sheet, and the composite solid electrolyte is arranged between the positive electrode sheet and the negative electrode sheet. Optionally, the positive electrode sheet and the negative electrode sheet are the positive electrode sheet and the negative electrode sheet of an existing sodium ion battery.

[0020] The present invention aims to solve the problems of low sodium ion transmission rate in sodium ion batteries, short circuit caused by the growth of Na dendrites, and poor instability of SEI films. The present invention adopts a technical idea of ​​combining organic materials with inorganic materials, takes polymers as the matrix, and combines sodium salts and silicon dioxide (SiO2) nanoparticles to form a composite solid electrolyte. At the same time, the proportions of the three in the electrolyte are controlled, which can effectively increase the diffusion channels of sodium ions, effectively accelerate the transmission of sodium ions and inhibit the growth of sodium dendrites, thereby improving the stability and electrochemical performance of sodium ion batteries.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) In the composite solid electrolyte of the present invention, the silicon dioxide nanoparticles can adsorb PF6 - , promoting the dissociation of NaPF6 and the release of free sodium ions, which helps to improve ionic conductivity. In addition, polymer matrices such as PVDF can help silica nanoparticles accelerate ion migration, effectively increase the number of sodium ion migration, inhibit the growth of sodium dendrites, and increase its electrochemical window.

[0023] (2) The preparation method of the composite solid electrolyte of the present invention is simple and convenient to operate, efficient, low in cost, environmentally friendly, easy to realize industrial production, and has good prospects for promotion and application. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below in conjunction with the embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0025] Example 1

[0026] The preparation method of the composite solid electrolyte of this embodiment comprises the following steps:

[0027] (1) Dissolve 2 g of PVDF in 8 g of NN-dimethylformamide and stir thoroughly for 1 h to obtain a clear polymer solution.

[0028] (2) Dispersing 0.25 g of sodium hexafluorophosphate and 0.25 g of silicon dioxide nanoparticles in the polymer solution, and continuously stirring at a rate of 650 rpm for 22 h to obtain a dispersed uniform slurry, ensuring that there is no agglomerated powder in the slurry. Then transfer the slurry to a vacuum drying oven at 70° C. and vacuum dry it for 24 h to obtain a composite solid electrolyte;

[0029] The obtained composite solid electrolyte has a PVDF content of 80 wt %, a sodium hexafluorophosphate content of 10 wt %, and a silicon dioxide nanoparticle content of 10 wt %.

[0030] The conductivity of sodium ions in the composite solid electrolyte was measured by electrochemical impedance spectroscopy and the value was 1.78×10 -3 S cm -1 .

[0031] Example 2

[0032] Example 1 was repeated, except that the content of sodium hexafluorophosphate in the composite solid electrolyte was 5 wt %, the content of silicon dioxide nanoparticles was 15 wt %, and the conductivity of sodium ions in the electrolyte was measured by electrochemical impedance spectroscopy to be 1.41×10 -3 S cm -1 .

[0033] Example 3

[0034] Example 1 was repeated, except that the content of sodium hexafluorophosphate in the composite solid electrolyte was 8 wt %, the content of silicon dioxide nanoparticles was 12 wt %, and the conductivity of sodium ions in the electrolyte was measured by electrochemical impedance spectroscopy to be 1.52×10 -3 S cm -1 .

[0035] Example 4

[0036] Example 1 was repeated, except that the content of sodium hexafluorophosphate in the composite solid electrolyte was 12 wt %, the content of silicon dioxide nanoparticles was 8 wt %, and the conductivity of sodium ions in the electrolyte was measured by electrochemical impedance spectroscopy to be 1.45×10 -3 S cm -1 .

[0037] Example 5

[0038] Example 1 was repeated, except that the content of sodium hexafluorophosphate in the composite solid electrolyte was 15 wt %, the content of silicon dioxide nanoparticles was 5 wt %, and the conductivity of sodium ions in the electrolyte was measured by electrochemical impedance spectroscopy to be 1.60×10 -3 S cm -1 .

[0039] The contents explained in the above embodiments should be understood as these embodiments are only used to more clearly illustrate the present invention, and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

Claims

1. A composite solid electrolyte, characterized in that: Calculated by weight, it comprises 70-90 parts of polymer matrix, 1-15 parts of sodium salt and 1-15 parts of silicon dioxide nanoparticles.

2. The composite solid electrolyte according to claim 1, characterized in that The composite solid electrolyte comprises 75-85 parts of a polymer matrix, 3-12 parts of a sodium salt and 3-12 parts of silicon dioxide nanoparticles.

3. The composite solid electrolyte according to claim 2, characterized in that: The composite solid electrolyte comprises 78-82 parts of a polymer matrix, 5-10 parts of a sodium salt and 5-10 parts of silicon dioxide nanoparticles.

4. The composite solid electrolyte according to any one of claims 1 to 3, characterized in that: The polymer matrix includes PVDF.

5. The composite solid electrolyte according to any one of claims 1 to 3, characterized in that: The sodium salt includes sodium hexafluorophosphate.

6. The composite solid electrolyte according to any one of claims 1 to 3, characterized in that: The particle size of the silicon dioxide nanoparticles is 1-100 nm.

7. The method for preparing a composite solid electrolyte according to any one of claims 1 to 6, characterized in that: The steps include: S1, mixing the polymer matrix and the organic solvent in a mass ratio of 1:3-5 to obtain a polymer solution; S2, dispersing sodium salt and silicon dioxide nanoparticles in the polymer solution to obtain a slurry; S3. Dry the slurry under vacuum at 60-80° C. for 12-36 hours to obtain a composite solid electrolyte.

8. The preparation method according to claim 7, characterized in that: The organic solvent is NN-dimethylformamide.

9. The preparation method according to claim 7, characterized in that: In S2, sodium hexafluorophosphate, silicon dioxide nanoparticles and the polymer solution are mixed and stirred at a rate of 600-700 rpm for 20-24 hours to obtain a slurry.

10. A sodium ion battery, characterized in that: The invention comprises a composite solid electrolyte according to any one of claims 1 to 6 or a composite solid electrolyte prepared by the preparation method according to any one of claims 7 to 9.