CN-118083980-B - Vacancy induction lifting single-layer Mo2Method for diffusing C fluoride ion

CN118083980BCN 118083980 BCN118083980 BCN 118083980BCN-118083980-B

Abstract

The invention discloses a method for improving the fluorine ion diffusion performance of a single-layer Mo 2 C by vacancy induction, which mainly adjusts and controls the structure of the single-layer Mo 2 C from the atomic scale by means of vacancy defects, reduces the diffusion energy barrier of fluorine ions in the single-layer Mo 2 C, thereby inducing the fluorine ions to rapidly diffuse in the vacancy system of the single-layer Mo 2 C and greatly improving the multiplying power performance of the single-layer Mo 2 C as a fluorine ion battery electrode material. The method comprises the steps of firstly adopting a first principle method to calculate the formation energy of the vacancy defect of single-layer Mo 2 C, screening and optimizing the vacancy defect system of single-layer Mo 2 C to obtain the most stable structure of Mo 1.78 C 0.89 , discussing the most stable fluorine ion adsorption sites on the basis to obtain the structure corresponding to the most stable fluorine ion adsorption system, and finding the optimal diffusion path of fluorine ions in Mo 1.78 C 0.89 , wherein the diffusion energy barrier of the corresponding fluorine ions is 0.07eV, which is far smaller than the diffusion energy barrier of the fluorine ions in single-layer Mo 2 C, which indicates that the introduction of the vacancy defect can obviously improve the transmission performance of the fluorine ions in single-layer Mo 2 C. In addition, mo 1.78 C 0.89 has good thermal stability at both temperatures of 300K and 500K. The invention provides a thought and a method for designing the fluoride ion battery electrode material with high diffusion performance.

Inventors

YANG ZHENHUA
WANG CHUANG
YOU LIDONG

Assignees

湘潭大学

Dates

Publication Date: 20260512
Application Date: 20231206

Claims (4)

1. A method for improving the diffusion performance of single-layer Mo 2 C fluoride ions by vacancy induction, which is characterized by comprising the following steps: Step 1, calculating the vacancy defect forming energy of single-layer Mo 2 C, and screening the vacancy type and stable structure of single-layer Mo 2 C, wherein the molecular formula of the structure is Mo 1.78 C 0.89 ; Step 2, energy band calculation is carried out on the structure of Mo 1.78 C 0.89 , and the electronic conductivity of the structure is analyzed; step 3, constructing adsorption structures corresponding to fluorine ions at different sites of Mo 1.78 C 0.89 according to structural symmetry, comparing total energy of the adsorption structures and calculating corresponding adsorption energy, thereby obtaining the most stable structure of Mo 1.78 C 0.89 F 0.125 ; Step 4, searching an optimal diffusion path of fluoride ions on Mo 1.78 C 0.89 by adopting a climbing elastic band method; Step 5, researching the thermal stability of Mo 1.78 C 0.89 at 300K and 500K respectively by adopting a de novo computational molecule dynamics method; In said step 1, the formation energies of different vacancy defect systems of the single-layer Mo 2 C are calculated according to the formula (1-1) Thereby obtaining a stable Mo 2 C vacancy structure; (1-1) in the formula (1-1), the amino acid sequence, Represents the energy of a single-layer Mo 2 C vacancy defect system, For a single atom or molecule of energy, The total energy of single-layer Mo 2 C; In the step 3, the corresponding fluorine ion adsorption energy is calculated according to the structure of the fluorine ions adsorbed at different sites of Mo 1.78 C 0.89 and the formula (1-2) ; (1-2) In the formula (1-2), 、 The total energy of Mo 1.78 C 0.89 F 0.125 and Mo 1.78 C 0.89 respectively, Then it is a single fluorine atom energy.
2. The method for improving the diffusion performance of single-layer Mo 2 C fluoride ions by vacancy induction according to claim 1, wherein in said step 2, energy band calculation is performed on Mo 1.78 C 0.89 to analyze the electron conductivity of the vacancy defect structure, and the specific steps are as follows: 2.1, carrying out structural optimization and static self-consistent calculation on the Mo 1.78 C 0.89 structure obtained in the step1 by adopting a Monkhorst-Pack type 2×2×1 and 4×4×1 Brillouin zone k point grid respectively; and 2.2, using the output file obtained by the static self-consistent calculation in the step 2.1 for energy band calculation of Mo 1.78 C 0.89 .
3. The method for improving the diffusion performance of single-layer Mo 2 C fluoride ions by vacancy induction according to claim 1, wherein in the step 4, an optimal diffusion path of fluoride ions in single-layer Mo 2 C and a vacancy defect system thereof is searched by adopting a climbing elastic band method, and the specific steps are as follows: Step 4.1, on the basis of obtaining the most stable fluorine ion adsorption site of Mo 1.78 C 0.89 in the step 3, namely a Mo 1.78 C 0.89 F 0.125 system, continuously searching adjacent equivalent fluorine ion adsorption sites; Setting two adjacent equivalent fluoride ion adsorption sites as an initial state and a final state of a fluoride ion diffusion path respectively, measuring the distance between the two states, and obtaining the number of inserted transition states according to the relation between the distance and the transition states so as to design the diffusion path of fluoride ions in Mo 1.78 C 0.89 ; And 4.3, optimizing a fluorine ion diffusion path in the Mo 1.78 C 0.89 by using a climbing elastic band method, and obtaining a fluorine ion diffusion energy barrier corresponding to the fluorine ion diffusion path.
4. The method for improving the diffusion performance of single-layer Mo 2 C fluoride ions by vacancy induction according to claim 1, wherein in the step 5, mo 1.78 C 0.89 has good thermal stability at both 300K and 500K temperatures as proved by the de novo molecular dynamics method.

Description

Method for improving single-layer Mo 2 C fluoride ion diffusion performance through vacancy induction Technical Field The invention belongs to the technical field of computing materials, and particularly relates to a method for improving the diffusion performance of single-layer Mo 2 C fluoride ions through vacancy induction. Background In recent years, with rapid development of electronic devices and electric automobiles, people put higher demands on the safety, high capacity, low cost and other aspects of energy storage products matched with the electronic devices and the electric automobiles, and how to develop high-performance secondary batteries is currently one of research hotspots in the current society. The fluoride ion battery is used as novel energy storage equipment and has the unique advantages that firstly fluoride ions are relatively stable, potential safety hazards are not easy to cause, secondly the fluoride ion battery has high energy density which is 6 to 10 times that of a lithium ion battery, abundant fluoride resources are reserved in crust, and the fluoride ion battery has the advantage of low cost. However, the poor rate performance severely restricts the further development of the fluoride ion battery, and the induction of rapid diffusion of fluoride ions in the electrode material is an effective method for solving the problem. The transition metal carbide has the advantages of high conductivity as a two-dimensional material, and the unique layered structure and the relatively stable adsorption sites of the transition metal carbide enable the transition metal carbide to have the advantage of high capacity. Among the transition metal carbides, the single-layer Mo 2 C has stable chemical property and larger specific surface area, and a sandwich structure is formed by alternately arranging (Mo-C-Mo) atomic layers, so that the storage of fluoride ions in the single-layer Mo 2 C is facilitated, and particularly, the single-layer Mo 2 C has higher energy density, but the diffusion performance of the fluoride ions in the single-layer Mo 3834C still needs to be further improved. Based on the internal correlation between the vacancy defects and the ion diffusion, the method for introducing the vacancy defects into the single-layer Mo 2 C improves the fluorine ion diffusion performance, the fluorine ion diffusion energy barrier is only 0.07eV, and the single-layer Mo 2 C-based fluorine ion battery electrode material with excellent rate performance is designed. Disclosure of Invention The invention aims to provide a method for improving the single-layer Mo 2 C fluoride ion diffusion performance by vacancy induction, which is a fluoride ion battery electrode material with excellent fluoride ion diffusion performance, and the specific implementation mode is carried out according to the following steps: step 1, screening the most stable structure (Mo 1.78C0.89) corresponding to single-layer Mo 2 C containing vacancy defects, and calculating the vacancy forming energy; step 2, obtaining the band gap of Mo 1.78C0.89 and confirming that the Mo has conductivity; Step 3, calculating the adsorption energy of fluoride ions at different sites on the surface of Mo 1.78C0.89, and screening out the most stable Mo 1.78C0.89F0.125; Step 4, in Mo 1.78C0.89F0.125, obtaining an optimal fluoride ion diffusion path and a fluoride ion diffusion energy barrier corresponding to the optimal fluoride ion diffusion path; Step 5, proving that Mo 1.78C0.89 has good thermal stability at the temperature of 300K and 500K; aiming at the problem of poor fluoride ion diffusion performance of single-layer Mo 2 C, the invention provides a method for improving the fluoride ion diffusion performance of single-layer Mo 2 C by vacancy induction, so as to obtain a design scheme and a technical route for realizing high diffusion performance of fluorine in the single-layer Mo 2 C. Firstly, single-layer Mo 2 C with different vacancy structures is subjected to structure screening to obtain the most stable vacancy defect structure (Mo 1.78C0.89), then the energy band gap calculation is carried out on the structure of Mo 1.78C0.89 to prove that the structure has excellent electronic conductivity, then the adsorption energy corresponding to different sites of Mo 1.78C0.89 is calculated and obtained, so that the most stable Mo 1.78C0.89 adsorption fluorine system (Mo 1.78C0.89F0.125) is screened out, on the basis, the minimum diffusion energy barrier of fluorine ions in Mo 1.78C0.89 and the corresponding fluorine ion diffusion path thereof are searched by adopting a climbing elastic band (CI-NEB) method, and finally the thermal stability of Mo 1.78C0.89 at the temperature of 300K and 500K respectively is studied by adopting the de novo computational molecular dynamics (AIMD). The minimum diffusion energy barrier of the fluorine ions in the Mo 1.78C0.89 is 0.07eV, meanwhile, the fluorine ions have good electron conductivity, and the Mo 1.78C0.8