Method for effectively improving RbPbF3 fluorine ion conductivity based on Cs doping

Abstract

The invention discloses a method for effectively improving RbPbF3 fluorine ion conductivity based on Cs doping, and aims to design an RbPbF3-based fluorine ion solid electrolyte material with relatively high fluorine ion conductivity, excellent insulation performance and a wide electrochemical window. The method comprises the following steps: firstly, calculating parameters such as structural stability, energy band gap, room-temperature fluorine ion conductivity and electrochemical window of a Cs-doped RbPbF3 system (RbCsxPb1-xF3-x) by adopting a first principle calculation method, and analyzing internal correlation between the Cs doping concentration (x) and lattice constant, electronic conductivity, thermal stability, mechanical property and electrochemical stability of the RbCsxPb1-xF3-x; therefore, the obtained RbCs0. 125Pb0. 875F2. 875 has the highest room-temperature fluorine ion conductivity, and belongs to an excellent fluorine ion solid electrolyte. The invention provides an effective method for quickly and accurately researching and developing the high-performance fluorine ion solid electrolyte.

Description

Technical Field

[0001] The present invention belongs to the technical field of computational material chemistry, and in particular relates to a method for effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping. Background Art

[0002] As a new type of energy storage device, fluoride ion solid-state battery has the advantages of high energy density, high voltage, high safety, long life and abundant resources. Therefore, fluoride ion solid-state battery has broad application prospects. As one of the key components of fluoride ion solid-state battery, solid electrolyte plays a key hub role. The development of fluoride ion solid electrolyte with high ionic conductivity and excellent electrochemical performance has become one of the research hotspots. Perovskite RbPbF3 has a unique three-dimensional tunnel structure and excellent electronic insulation, which has attracted much attention. However, the room temperature (300K) fluoride ion conductivity of RbPbF3 is only 1.41×10 -5 S / cm, which is difficult to be applied in practice. In addition, the method of doping RbPbF3 with Cs to achieve precise control of the crystal structure of RbPbF3 at the atomic scale is the fundamental way to solve this problem. The present invention aims to effectively improve the fluoride ion conductivity of RbPbF3. The first principles and molecular dynamics methods are used to clarify the mechanism of Cs doping RbPbF3, and the intrinsic relationship between the Cs doping concentration and the crystal structure, band structure, structural stability and fluoride ion conductivity of the Cs doped RbPbF3 system is obtained. The RbPbF3-based solid electrolyte (RbCs) with electrical insulation, high fluoride ion conductivity, good thermal stability and good electrochemical stability is designed. 0.125 Pb 0.875 F 2.875 ). Summary of the invention

[0003] The present invention aims to provide a method for effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping, and the specific implementation method is carried out according to the following steps:

[0004] Step 1: Use structure search method to search RbCs x Pb 1-x F 3-x and Rb 1-x Cs x PbF3 (x = 0.0843, 0.125, 0.25, 0.375) was used for structural screening, the chemical potential of each component was optimized, the chemical potential conditions required for synthesizing its stable structure were analyzed, and its formation energy and binding energy (E coh ), thus comparing the structural stability of these two different Cs-doped RbPbF3 systems (RbCs x Pb 1-x F 3-x Has a relatively stable structure);

[0005] Step 2: RbCs x Pb 1-x F 3-x (x=0, 0.0843, 0.125, 0.25, 0.375) to optimize the structure and obtain its most stable structure and lattice constant;

[0006] Step 3: Simulation of RbCs using ab initio molecular dynamics (AIMD) method x Pb 1-x F 3-x The fluoride ion diffusion process and fluoride ion conductivity at different temperatures were used to screen out the Cs-doped RbPbF3 system (RbCs 0.125 Pb 0.875 F 2.875 );

[0007] Step 4: Calculate and analyze RbCs with the help of pymatgen and vasp software 0.125 Pb 0.875 F 2.875 The probability density and charge density of fluoride ions;

[0008] Step 5: Calculate RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 elastic constants and analyze their mechanical properties;

[0009] Step 6: RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 Perform energy band calculations and analyze its electronic conductivity;

[0010] Step 7: Calculate and analyze RbCs using the ab initio molecular dynamics (AIMD) method 0.125 Pb 0.875 F 2.875 Thermal stability;

[0011] Step 8: Calculate RbCs with the help of pymatgen software 0.125 Pb 0.875 F 2.875 The electrochemical window

[0012] The present invention provides a method for effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping. x Pb 1-x F 3-xThe formation energy of (x=0.0834, 0.125, 0.25, 0.375) under different chemical potential conditions is used to determine its optimal growth environment; then the intrinsic relationship between Cs doping concentration (x) and its lattice constant, basic mechanical parameters, energy band gap and room temperature fluorine ion conductivity is established, thereby obtaining the optimal Cs-doped RbPbF3 structure (RbCs 0.125 Pb 0.875 F 2.875 ), and on this basis, the diffusion mechanism of fluoride ions in it was obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] By describing in detail the embodiments shown in the accompanying drawings, the drawings described below are only some embodiments of the present invention, in which:

[0014] Figure 1 A flow chart of a design method for effectively improving the fluoride ion conductivity of RbPbF3 based on Cs doping;

[0015] Figure 2 (a) The range of relative chemical potentials required to form RbPbF3 (see gray area); Figure 2 (b) shows that when CsPb3 is used as the doping material, RbCs x Pb 1-x F 3-x and Rb 1-x Cs x Formation energy of PbF3(x=0.0834,0.125,0.25,0.375); Figure 2 (c) represents RbCs x Pb 1-x F 3-x and Rb 1-x Cs x The binding energy (E) of PbF3 (x = 0.0834, 0.125, 0.25, 0.375) coh );

[0016] Figure 3 (a) is RbCs x Pb 1-x F 3-x Room temperature (300K) fluoride ion conductivity (σ) of (x=0, 0.0834, 0.125, 0.25, 0.375), Figure 3 (b) RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 The Arrhenius curve of

[0017] Figure 4 (a) and Figure 4(b) RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 The charge density diagram and its probability density of fluoride ions at a temperature of 300K;

[0018] Figure 5 For RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 The distribution of Young's modulus in three-dimensional space and its projections along the x, y and z directions, in GPa;

[0019] Figure 6 RbCs 0.125 Pb 0.875 F 2.875 The variation of total energy with ab initio molecular dynamics (AIMD) calculation time at temperatures between 300K and 800K;

[0020] Figure 7 When Pb is used as the negative electrode of the fluoride ion battery, RbCs 0.125 Pb 0.875 F 2.875 The relationship between the voltage and the amount of Pb reaction; DETAILED DESCRIPTION

[0021] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. The present invention proposes a method for effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping. Figure 1 The flow chart of this method is as follows. First, the formation energy and binding energy (E coh ) method to study its structural stability. Two Cs-doped RbPbF3 systems (Rb 1-x Cs x PbF3 and RbCs x Pb 1-x F 3-x ), the calculation results show that: RbCs x Pb 1-x F 3-x Rb 1-x Cs x PbF3 has good structural stability; then the ab initio molecular dynamics (AIMD) method was used to calculate RbCs x Pb 1-x F 3-x The fluorine ion conductivity of RbCs was determined by the variation of Cs doping concentration (x) and temperature. 0.125 Pb 0.875 F 2.875It has the best room temperature (300K) fluoride ion conductivity; on this basis, RbCs is further calculated and analyzed 0.125 Pb 0.875 F 2.875 mechanical properties, electronic conductivity, thermodynamic stability and electrochemical window.

[0022] The specific parameters of the first-principles calculation are as follows: the PBE (Perdew-Burke-Ernzerh) method based on the generalized gradient approximation (GGA) is used to deal with the exchange energy, and the projected augmented plane wave (PAW) method is used to describe the interaction between electrons and ions. The plane wave cutoff energy and the Monkhorst-Pack type k-point grid are set to 520 eV and 4×4×4, respectively. The energy and force convergence accuracy are set to 10 -5 eV / atom and

[0023] RbCs x Pb 1-x F 3-x and Rb 1-x Cs x PbF3 (x = 0, 0.0834, 0.125, 0.25, 0.375) is the research object, and the total energy of the two is calculated to obtain their stable structures. x Pb 1-x F 3-x and Rb 1-x Cs x The difficulty of PbF3 is calculated according to formula (1-1) and formula (1-2) under different chemical potential conditions. f1 (x) and E f2 (x)). E f1 (x) = E tot (RbC x Pb 1-x F 3-x )-E tot (bulk)+n Pb (Δμ Pb +μ Pb )+n F (Δμ F +μ F )-n Cs (Δμ Cs +μ Cs ) (1-1) E f2 (x) = E tot (Rb 1-x Cs x PbF3)-Etot (bulk)+n Rb (Δμ Rb +μ Rb )-n Cs (Δμ Cs +μ Cs )(1-2) Among them, E f1 (x) and E f2 (x) are RbCs x Pb 1-x F 3-x and Rb 1-x Cs x Formation energy of PbF3; E tot (RbC x Pb 1- x F 3-x )、E tot (bulk) and E tot (Rb 1-x Cs x PbF3) respectively RbCs x Pb 1-x F 3-x , RbPbF3 and Rb 1-x Cs x The total energy of PbF3; n Pb 、n Rb 、n F and n Cs is the number of atoms of the elements Pb, Rb, F and Cs in the structure; μ Pb , μ Rb , μ F and μ Cs is the chemical potential of elements Pb, Rb, F and Cs; Δμ Pb , Δμ Rb , Δμ F and Δμ Cs is the relative chemical potential of elements Pb, Rb, F and Cs. In order to solve Δμ Pb , Δμ Rb , Δμ F and Δμ Cs First, we searched for possible competing phases from the ICSD (Inorganic Crystal Structure Database) database. Based on the formation enthalpy of the competing phases, we found that the competing phases of RbPbF3 are RbF and PbF2 using the CPLAP method. In order to maintain the structural stability of RbPbF3 and avoid the formation of other competing phases, Δμ i(i is Pb, Rb, F) should satisfy the constraints (see formula (1-3) to formula (1-6)). According to this constraint, the range of relative chemical potential required to form stable RbPbF3 can be obtained, such as Figure 2 (a) shown. Δμ Rb +Δμ Pb +3Δμ F ≤ΔH f (RbPbF3) (1-3) Δμ Rb ≤0Δμ Pb ≤0Δμ F ≤0 (1-4) Δμ Rb +Δμ F ≤ΔH f (RbF) (1-5) Δμ Pb +2Δμ F ≤ΔH f (PbF2) (1-6)

[0024] Based on the relative chemical potential (Δμ i ) conditions (see Figure 2 (a) Considering five Cs-doped raw materials (CsF, Cs3Rb, CsRb, CsRb3, and CsPb3), the relative chemical potential constraints of these five compounds were calculated. x Pb 1-x F 3-x and Rb 1-x Cs x The formation energy of PbF3 (x = 0.0834, 0.125, 0.25, 0.375) at the boundary points (AD points) of different chemical potential stable regions is compared to show that: RbCs x Pb 1-x F 3-x and Rb 1-x Cs x PbF3 at point B (Δμ Rb =-5.15eV,Δμ Pb =-7.52eV,Δμ F =0eV) has the lowest formation energy. At the same time, it was found that when CsRb3 is used as the doping material, as the Cs concentration (x) increases, RbCs x Pb 1-x F 3-x Average ratio Rb 1-x Cs x PbF3 (x = 0.0834, 0.125, 0.25, 0.375) has a lower formation energy (such as Figure 2 (b) shows that the former is easier to form than the latter. According to formula (1-7), RbCs x Pb 1-x F 3-x and Rb 1-x Cs x The binding energy (E) of PbF3 (x = 0.0834, 0.125, 0.25, 0.375) coh ), the calculation results are as follows Figure 2 As shown in (c), from Figure 2 (c) It can be seen that: RbCs x Pb 1-x F 3-x The binding energy is lower than that of Rb 1-x Cs x PbF3, thus further proving that RbCs x Pb 1-x F 3-x Rb 1-x Cs x PbF3 has good structural stability. In formula (1-7), the integers a, b, c and d are RbCs respectively. x Pb 1-x F 3-x (or Rb 1-x Cs x The number of Rb, Cs, Pb and F atoms in PbF3; E total , and RbCs x Pb 1-x F 3-x (or Rb 1-x Cs x PbF3), the total energy of a single Rb atom, the energy of a single Cs atom, the energy of a single Pb atom, and the energy of a single F atom.

[0025] Calculate RbCs x Pb 1-x F 3-x The lattice constant and volume expansion rate of RbCs change with the Cs concentration (x). The calculation results show that: x Pb 1-x F 3-x The lattice constant and unit cell volume decrease continuously with the increase of Cs concentration (x).

[0026] Ab initio molecular dynamics (AIMD) simulations were performed to simulate the fluoride ion in RbPbF3 and Cs-doped RbPbF3 systems (RbCs xPb 1-x F 3-x ) and calculate its fluoride ion conductivity. First calculate RbCs x Pb 1-x F 3-x The average mean square displacement (MSD) of (x=0, 0.0834, 0.125, 0.25, 0.375) is used to calculate RbCs based on the slope of the average mean square displacement (MSD) curve and formula (1-8) x Pb 1-x F 3-x The variation of the fluoride ion diffusion coefficient (D) with the Cs concentration (x). Based on the Nernst-Einstein equation (see formula (1-9)) and RbCs x Pb 1-x F 3-x The fluoride ion diffusion coefficient (D) was obtained, and the fluoride ion conductivity at a temperature of 300K was obtained. The calculation results are as follows Figure 3 (a). Among them, RbCs 0.125 Pb 0.875 F 2.875 The fluoride ion conductivity is as high as 1.03×10 -1 S / cm(temperature is 300K). In formula (1-8), d is the dimension factor, t is the diffusion duration, and Δr(t) is the average mean square displacement (MSD). In formula (1-9), T, ρ, z, F and R are temperature, molar density of fluoride ions, charge number of fluoride ions, Faraday constant and gas constant, respectively.

[0027] According to formula (1-10), the fluoride ion conductivity (σ) and temperature (T) are fitted to obtain RbCs x Pb 1-x F 3-x The activation energy (E a ) changes with the Cs concentration (x). In formula (1-10), T, z, l, v0 and k are temperature, charge number of fluoride ion, migration distance of fluoride ion, transition frequency of fluoride ion and Boltzmann constant, respectively.

[0028] Based on the above method, calculate RbCs x Pb 1-x F 3-x The room temperature (300K) fluoride ion conductivity of (x=0, 0.0834, 0.125, 0.25, 0.375) shows that RbCs0.125 Pb 0.875 F 2.875 It has the highest room temperature fluoride ion conductivity (1.03×10 -1 S / cm); In addition, RbCs 0.125 Pb 0.875 F 2.875 The activation energy (E a ) is only 0.07 eV, which is significantly smaller than the activation energy (E a =0.24eV)(see Figure 3 (b)).

[0029] Based on RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 The ab initio molecular dynamics (AIMD) calculation results (temperature 300K, simulation time 200ps) are used to further calculate and analyze the charge density and probability density function of fluoride ions in the two. The calculation results are as follows Figure 4 (a) and 4(b), where ρ max represents the highest fluoride ion probability. Figure 4 (a) and Figure 4 (b) It can be seen that for RbPbF3, fluoride ions are only distributed along the Pb-F bond and their diffusion is relatively difficult, which is the reason why RbPbF3 has extremely low room temperature fluoride ion conductivity. 0.125 Pb 0.875 F 2.875 The three-dimensional channel of RbCs is continuously distributed, and fluoride ions can diffuse easily. 0.125 Pb 0.875 F 2.875 It has higher fluoride ion conductivity than RbPbF3.

[0030] Calculate RbPbF3 and RbCs according to formula (1-11) 0.125 Pb 0.875 F 2.875 The elastic constant (C ij ), and further derive the basic mechanical parameters. In formula (1-11), E(V0,0) and E(V,ε) are RbPbF3 and RbCs respectively. 0.125 Pb 0.875 F 2.875 The total energy before and after strain occurs, V0 is the volume, C ij is the elastic constant, ε is the strain tensor, e i and e j For strains. RbPbF3 and RbCs 0.125Pb 0.875 F 2.875 Belongs to the tetragonal system, and its three independent elastic constants (C 11 , C 12 and C 44 ) all satisfy the constraints of the elastic constants (see formula (1-12)). C 11 >0, C 11 -C 12 >0, C 44 >0, C 12 >0 (1-12)

[0031] Based on RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 The elastic constant (C 11 , C 12 and C 44 ), and calculate the bulk modulus (B), shear modulus (G) and B / G value of the two according to equations (1-13) to (1-17).

[0032] R 0.125 Pb 0.875 F 2.875 The B / G value is 2.24. According to the judgment criteria of material toughness and brittleness (if the B / G value of a material is greater than 1.75, it is ductile, otherwise it is brittle), RbCs 0.125 Pb 0.875 F 2.875 It is ductile.

[0033] In order to analyze RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 The mechanical properties of the two vary with direction. According to formula (1-18), the three-dimensional Young's modulus (E) and its projection along the x, y and z directions are obtained. The calculation results are shown in Figure 5 As shown. Figure 5 It can be seen that RbCs 0.125 Pb 0.875 F 2.875 It exhibits more obvious isotropy than RbPbF3, which helps it maintain better structural stability during the charge and discharge process. In formula (1-18), l1, l2 and l3 represent unit vectors, S ij is the elastic compliance constant.

[0034] Calculate RbCs 0.125 Pb 0.875 F 2.875 The energy band gap values ​​of RbPbF3 and RbPbF3 are 3.04eV and 3.07eV, respectively, which indicates that both have excellent electronic insulation properties.

[0035] Ab initio molecular dynamics (AIMD) method was used to calculate the RbCs 0.125 Pb 0.875 F 2.875 The total energy of the sample changes with time, and its thermal stability in the temperature range of 300K to 800K is further analyzed. The calculation results are as follows Figure 6 As shown. Figure 6 It can be seen that RbCs 0.125 Pb 0.875 F 2.875 The total energy can maintain a stable distribution in the temperature range of 300K to 800K, which indicates that it has excellent thermal stability.

[0036] Using Pb metal as the negative electrode material of fluoride ion battery, RbCs was analyzed by pymatgen software 0.125 Pb 0.875 F 2.875 (Rb8CsPb7F 23 ) and Pb (as shown in Table 1), and calculate RbCs 0.125 Pb 0.875 F 2.875 (Rb8CsPb7F 23 ) to study its electrochemical stability. The calculation results are as follows Figure 7 As shown. Figure 7 RbCs can be found 0.125 Pb 0.875 F 2.875 It has a wide electrochemical window (3.92V). Table 1 RbCs 0.125 Pb 0.875 F 2.875 (Rb8CsPb7F 23 ) and Pb under different voltage conditions

[0037] Finally, it is necessary to explain here that the above-mentioned specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above-mentioned contents of the present invention belong to the protection scope of the present invention.

Claims

1. A method for effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping, characterized in that: The method comprises the following steps: Step 1: Use structure search method to search for RbCs x Pb 1-x F 3-x and Rb 1-x Cs x PbF3 (x = 0.0843, 0.125, 0.25, 0.375) was used for structural screening, the chemical potential of each component was optimized, the chemical potential conditions required for synthesizing its stable structure were analyzed, and its formation energy and binding energy (E coh ), thus comparing the structural stability of these two different Cs-doped RbPbF3 systems (RbCs x Pb 1-x F 3-x Has a relatively stable structure); Step 2: RbCs x Pb 1-x F 3-x (x=0, 0.0843, 0.125, 0.25, 0.375) to optimize the structure and obtain its most stable structure and lattice constant; Step 3: Simulation of RbCs using ab initio molecular dynamics (AIMD) method x Pb 1-x F 3-x The fluoride ion diffusion process and fluoride ion conductivity at different temperatures were used to screen out the Cs-doped RbPbF3 system (RbCs 0.125 Pb 0.875 F 2.875 ); Step 4: Calculate and analyze RbCs with the help of pymatgen and vasp software 0.125 Pb 0.875 F 2.875 The probability density and charge density of fluoride ions; Step 5: Calculate RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 elastic constants and analyze their mechanical properties; Step 6: RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 Perform band structure calculations and analyze its electronic conductivity; Step 7: Calculate and analyze RbCs using the ab initio molecular dynamics (AIMD) method 0.125 Pb 0.875 F 2.875 Thermal stability; Step 8: Calculate RbCs with the help of pymatgen software 0.125 Pb 0.875 F 2.875 electrochemical window.

2. A method for effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping according to claim 1, characterized in that: In step 1, a structure search method is used to identify RbCs x Pb 1-x F 3-x and Rb 1-x Cs x PbF3 (x = 0.0843, 0.125, 0.25, 0.375) was used for structural screening, and the binding energy (E coh ), and further calculate the chemical potential (μ i ) and its relative chemical potential (Δμ i ), the relative chemical potential stable region of RbPbF3 was obtained, and the relatively stable Cs-doped RbPbF3 system (RbCs x Pb 1-x F 3-x ).

3. The method of effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping according to claim 1, characterized in that: In step 2, RbCs x Pb 1-x F 3-x (x=0, 0.0843, 0.125, 0.25, 0.375) were used for structural analysis to obtain the most stable Cs doping site and lattice constant.

4. The method of effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping according to claim 1, characterized in that: In step 3, the ab initio molecular dynamics (AIMD) method is used to calculate RbCs x Pb 1-x F 3-x The fluoride ion conductivity of (x=0, 0.0843, 0.125, 0.25, 0.375) screened out the optimal Cs-doped RbPbF3 system as RbCs 0.125 Pb 0.875 F 2.875 , which has the best fluoride ion conductivity; the specific steps are as follows: Step 3.1: Simulation of fluoride ion in RbCs x Pb 1-x F 3-x The diffusion process in (x=0, 0.0843, 0.125, 0.25, 0.375) is analyzed, and its MSD curves under different temperature environments are obtained. Step 3.2: Based on the RbCs obtained in step 3.1 x Pb 1-x F 3-x The fluoride ion conductivity was deduced from the MSD curves under different temperature environments (x=0, 0.0843, 0.125, 0.25, 0.375).

5. The method of effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping according to claim 1, characterized in that: In step 4, by analyzing RbCs 0.125 Pb 0.875 F 2.875 The fluoride ion probability density and charge density are calculated to further clarify the fluoride ion diffusion mechanism.

6. The method of effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping according to claim 1, characterized in that: In step 5, by calculating RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 Elastic constants, determine RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 The specific steps are as follows: Step 5.1: Calculation of RbPbF3 and RbCs using first-principles methods 0.125 Pb 0.875 F 2.875 The elastic constants of the material are obtained, and its mechanical parameters are derived, including bulk modulus (B), shear modulus (G), B / G value and Young's modulus (E). Step 5.2: Based on the mechanical parameters obtained in step 5.1, analyze the RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 The distribution law of Young's modulus in three-dimensional space and its projection along the x, y and z directions are obtained, so as to obtain the distribution law of Young's modulus of the two with direction.

7. The method of effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping according to claim 1, characterized in that: In step 6, RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 Perform energy band calculations and analyze its electronic conductivity; the specific steps are as follows: Step 6.1: RbPbF3 and RbCs obtained in step 2 0.125 Pb 0.875 F 2.875 Static calculations were performed based on the Monkhorst-Pack (MP) type Brillouin zone k-point grid and cutoff energy set to 4 × 4 × 4 and 520 eV, respectively. Step 6.2: Use the output file from step 6.1 for RbPbF3 and RbCs 0.125 Pb 0.875 F 2.875 Energy band calculation.

8. The method of effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping according to claim 1, characterized in that: In step 7, when the temperature is in the range of 300K to 800K, RbCs 0.125 Pb 0.875 F 2.875 The total energy remains stable over time.

9. The method of effectively improving the fluorine ion conductivity of RbPbF3 based on Cs doping according to claim 1, characterized in that: In step 8, RbCs was calculated using the pymatgen software package. 0.125 Pb 0.875 F 2.875 The electrochemical window of the device was used to analyze its electrochemical stability.

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