Ca / sr / ba doped modified sodium-rich anti-perovskite solid-state electrolyte material and method

Abstract

This invention belongs to the field of solid electrolyte materials technology, and particularly relates to a Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material and method. The material uses sodium-rich anti-perovskite Na3SI as a matrix, and is obtained by doping with at least one metal atom selected from Ca, Sr, and Ba to replace some of the Na atoms in the matrix. The crystal structure of the material belongs to the Pm-3m space group, with lattice parameters satisfying a=b=c=10.0-11.0 Å, α=β=γ=90°, formation energy ≤-1.14 eV, band gap of 3.27-3.40 eV, and room temperature ionic conductivity.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte materials technology, and particularly relates to a Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material and method. Background Technology

[0002] Solid-state electrolytes, as core materials for next-generation energy storage devices, have become a key direction for solving problems such as leakage, flammability, and narrow electrochemical windows of traditional liquid electrolytes due to their high safety and good electrochemical stability. Anti-perovskite materials have attracted much attention in the field of solid-state electrolytes due to their tunable crystal structure, excellent mechanical stability, and ion transport potential. Among them, sodium-rich anti-perovskite Na3SI has become a promising matrix material due to its abundant sodium resources and intrinsic structural stability. However, the ionic conductivity of raw Na3SI is still insufficient to meet the requirements of high-performance energy storage devices, and its mechanical toughness needs to be optimized to adapt to the electrode interface contact requirements.

[0003] Doping modification is one of the core strategies for regulating the properties of anti-perovskite materials. By introducing heteroatoms, the lattice structure and ion transport channels can be controlled, thereby improving ionic conductivity. However, in existing doping studies, some metal element doping can disrupt the lattice stability of the material, or introduce defect energy levels leading to a reduction in band gap and leakage risk. Other doping elements can reduce the mechanical toughness of the material, limiting its practical applications. Therefore, it is crucial to screen doping elements that combine structural compatibility, electrical insulation retention, and performance enhancement to achieve… The synergistic optimization of material ionic conductivity and mechanical properties has become a key technical challenge in the current research and development of sodium-rich anti-perovskite solid electrolytes. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned technical problems by providing a Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material and method.

[0005] In view of this, the present invention provides a Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material, which uses sodium-rich anti-perovskite Na3SI as the matrix and obtains it by doping with at least one metal atom selected from Ca, Sr, and Ba to replace part of the Na atoms in the matrix. The material has a crystal structure belonging to the Pm-3m space group, with lattice parameters satisfying a=b=c=10.0-11.0 Å, α=β=γ=90°, a formation energy ≤-1.14 eV, a band gap of 3.27-3.40 eV, and a room temperature ionic conductivity of [missing information]. .

[0006] Preferably, when the doped atom in the material is Sr, the formation energy is -1.28 eV, and the room temperature ionic conductivity can reach [value missing]. .

[0007] Preferably, the elastic constant of the material satisfies C 11 =37.11-37.80 GPa, C 12 =4.30-8.42GPa, C 44 =5.78-6.68 GPa, and meets the mechanical stability criterion C. 11 >C 12 C 44 >0, C 11 +2C 12 >0.

[0008] Preferably, the material has a bulk modulus B = 15.47-17.98 GPa, a shear modulus G = 9.00-9.33 GPa, a Young's modulus E = 22.61-23.61 GPa, a B / G ratio ≥ 1.72, and a Poisson's ratio v ≥ 0.26.

[0009] Preferably, the material contains Na + The activation energy is 0.27-0.31 eV, and in the temperature range of 300K-1300K, Na... + As the main migrating ion, S 2- and I - They hardly migrate.

[0010] A method for preparing a Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material includes the following steps: Step 1: Using Na3SI as the matrix, construct a Na3SI cubic unit cell, in which Na atoms occupy vertex positions, S atoms are located at face-centered positions, and I atoms are located at body-centered positions; Step 2: Expand the cubic unit cell into a 2×2×2 supercell, replace one Na atom in the supercell with at least one metal atom from Ca, Sr, and Ba, and construct a doping model; Step 3: Optimize the structure of the doped model using density functional theory and the Vienna ab initio simulation software package. The optimization parameters are: Using the PBE generalized gradient approximation exchange-correlated functional and the projected fused wave method, a 5×5×5k-point grid centered at Γ point is employed, with a plane wave cutoff energy of 550 eV and atomic relaxation forces. Electron step energy convergence accuracy 10 -6 eV; Step 4: Perform ab initio molecular dynamics simulation on the optimized doping model. The simulation temperature range is 300K-1300K, the total duration is 120ps, the time step is 2fs, and the first 10ps are used for system equilibration to obtain the target solid electrolyte material.

[0011] Preferably, after structural optimization in step three, the electronic band structure is calculated using the HSE06 functional, and the self-consistent field convergence criterion is 10. -6 eV.

[0012] Preferably, the plane wave cutoff energy in step four of the AIMD simulation is 400 eV, and the energy convergence threshold is 10 eV. -5 eV, the Brillouin zone is sampled only at the Γ point.

[0013] Preferably, in step four, the activation energy is derived from the diffusion coefficient using the Arrhenius relation, and the diffusion coefficient is converted into ionic conductivity using the Nernst-Einstein relation.

[0014] Preferably, the chemical bonds in the material are mainly ionic bonds, with a small number of covalent bonds between Ca, Sr, Ba and S atoms, resulting in a high degree of atomic ionization and no obvious defect energy levels.

[0015] The beneficial effects of this invention are as follows: By modifying sodium-rich anti-perovskite Na3SI with Ca / Sr / Ba doping, the synergistic optimization of material structure and electronic properties is achieved. The doped material retains its original cubic crystal structure, with minimal changes in lattice parameters that meet mechanical stability requirements, resulting in significantly enhanced system stability. Simultaneously, it maintains a large band gap, with no defective energy levels introduced, effectively preventing internal leakage in the battery. The high degree of atomic ionization and the predominantly ionic bonding characteristics ensure the material's electrical insulation and structural integrity.

[0016] This doping strategy significantly improves the mechanical toughness and ion transport performance of the material. Metal doping gives the material good toughness, which is conducive to forming a tight contact with the electrode material. The ionic conductivity is greatly improved compared with the original material, the sodium ion migration barrier is reduced, and the efficient ion transport capability can be maintained over a wide temperature range. It successfully solves the technical pain points of insufficient ionic conductivity and poor mechanical toughness of the original Na3SI, and provides reliable support for the practical application of high-performance solid electrolytes. Attached Figure Description

[0017] Figure 1 The present invention provides (a) a supercell model of Na3SI and (b) a heteroatom doping model. Figure 2 The formation energy of the metal doping model (Mg, Ca, Sr, Ba, Al, Ga-Na3SI) of this invention; Figure 3 (a) Band diagram of the Na3SI model and (b) DOS diagram; (c) Band diagram of the Mg-Na3SI doped model and (d) DOS diagram; (e) Band diagram of the Al-Na3SI doped model and (f) DOS diagram; Figure 4(a) Band and (b) density of states diagram of the Ca-Na3SI doped model, (c) Band and (d) density of states diagram of the Sr-Na3SI doped model, (e) Band and (f) density of states diagram of the Ba-Na3SI doped model, (g) Band and (h) density of states diagram of the Ga-Na3SI doped model. Figure 5 This is a differential charge density diagram of the Mg, Ca, Sr, Ba, Al, Ga-Na3SI doping model of this invention; Figure 6 (a) Diffusion coefficient of Na3SI and metal doping model; (b) Conductivity; (c) Diffusion coefficient of Na3SI and metal doping model. The mean square displacement (MSD) versus temperature curve; (d) at 1000 K Mean square displacement (MSD); Figure 7 The mean orientation of Na, S, and I ions is given by the Na3SI model at (a) 800, (b) 1000, and (c) 1200 K. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0019] This study selected Na3SI, a sodium-rich anti-perovskite with good structural stability, as the research object. A metal doping strategy was employed to improve its ionic conductivity while maintaining its mechanical stability. A doping model was constructed using various metal atoms (Mg, Ca, Sr, Ba, Al, Ga), all of which have higher valence states than Na. + When these metals replace Na sites in the crystal lattice, the charge compensation effect forces the system to generate sodium ion vacancies, thereby increasing the conductivity of Na+. Density functional theory (DFT) was used to systematically study the effects of metal doping on the crystal structure, electronic properties, mechanical strength, and ion transport characteristics of Na3SI. The modulation rules of these properties by different doping atoms were summarized, and metal doping models suitable for solid-state electrolyte applications were screened, providing a theoretical basis for the design of high-performance solid-state electrolyte materials.

[0020] All calculations were performed using density functional theory and the Vienna Ab initio Simulation software package (VASP). The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) exchange-correlation functional was used to describe electron-electron interactions; the projected fused wave (PAW) method was used to describe ion-electron interactions. To achieve convergence in the structure optimization, a 5×5×5 k-point grid centered at the Γ point and a plane wave cutoff energy of 550 eV were used. All atomic coordinates and lattice parameters were optimized using the conjugate gradient method to minimize the total energy and atomic forces of the system: during atomic relaxation, the force on a single atom was limited to no more than [value missing]. The energy convergence accuracy between electronic steps is 10. -6 eV. Based on this, the stability, electronic properties, ion migration ability, and mechanical properties of the Na3SI model were systematically studied.

[0021] The electronic band structure was calculated using the HSE06 functional to obtain accurate bandgap values, with a self-consistent field convergence criterion of 10⁻⁶ eV. Based on the same calculation parameters, the three independent elastic constants C11, C12, and C44 of the optimized crystal structure were calculated. To study the migration behavior of sodium ions, ab initio molecular dynamics simulations were performed in a 2×2×2 supercell at temperatures ranging from 300 K, 500 K, 600 K, 700 K, 800 K, 900 K, 1000 K, 1100 K, 1200 K, and 1300 K, using a plane wave cutoff energy of 400 eV and a 10⁻⁶ eV threshold. -5 The energy convergence threshold is eV, and the Brillouin zone is sampled only at the Γ point. The total AIMD simulation duration is 120 ps with a time step of 2 fs, and the first 10 ps are used for the system to reach equilibrium. The diffusion coefficient and conductivity are derived from the activation energy.

[0022] Heteroatom doping is one of the important methods for regulating the properties of anti-perovskite materials. This work theoretically investigates the regulatory effects of various common metal doping defects (Mg, Ca, Sr, Ba, Al, Ga) on the properties of Na3SI anti-perovskite. In the constructed Na3SI cubic unit cell, Na atoms occupy the cell vertices, S atoms are located at the face centers, and I atoms are located at the body center. The optimized crystal structure belongs to the Pm-3m space group, with lattice parameters a=b=c=10.60Å, α=β=γ=90°. To study metal doping defects, the Na3SI unit cell is first extended into a 2×2×2 supercell (model shown in Figure 1). Figure 1 As shown in a), a metal doping defect model was then constructed by replacing one Na atom in the supercell with a Mg, Ca, Sr, Ba, Al, or Ga atom, respectively. Figure 1(b) The metal-doped model was then structurally optimized. The lattice parameters of the metal-doped model are shown in Table 1. Compared to the undoped Na3SI model, these parameters show minimal changes, with the angle remaining at 90°, indicating that these metal dopants do not disrupt lattice stability. Notably, the sum of the rates of change of the a, b, and c axes increases with the increase of the doped atomic radius, indicating that the doped atomic radius has a significant impact on the lattice structure.

[0023] Table 1. Lattice constants of Na3SI and metal doping models (Mg, Ca, Sr, Ba, Al, Ga-Na3SI).

[0024] Formation energy is a commonly used indicator of the stability of a doped defect system. A lower formation energy indicates higher system stability; a higher formation energy indicates greater difficulty in the formation of doped defects. The formation energy of a compound is calculated based on the chemical potential of its constituent substances or elements. The expression for defect formation energy is: (1); The total energy of the metal-doped system. The energy of an undoped Na3SI unit cell; The number of atoms added or removed is indicated by a negative sign (-) for addition and a positive sign (+) for reduction. The chemical potentials of the corresponding atoms are given. The formation energies of the Na3SI model for Mg, Ca, Sr, Ba, Al, and Ga doped with Na are 0.08 eV, -1.27 eV, -1.28 eV, -1.14 eV, 1.29 eV, and 0.55 eV, respectively. Figure 2 The results show that the formation energies of Mg, Al, and Ga-doped Na3SI are positive, while those of Ca, Sr, and Ba-doped Na3SI are negative. Among them, Sr-doped Na3SI has the lowest formation energy, indicating that its structure is the most stable.

[0025] Solid electrolyte materials must maintain electrical insulation to prevent internal leakage in the battery; therefore, studying the impact of metal doping on the electronic properties of sodium-rich anti-perovskite Na3SI is crucial. This study analyzes the band gap and charge contribution using band structure and density of states (DOS); and charge transfer in the doped system is analyzed using differential charge density and Bader charge. The HSE06 functional was used to calculate the band structure of Na3SI and the metal-doped model to obtain simulation results closer to experimental values. Figure 3 The band structure and DOS plots for the Na3SI, Mg, and Al doped models are shown; the band structure and DOS plots for other metal doped models are shown below. Figure 4 As shown, the Fermi levels are all set to 0 eV. The band gap of the undoped Na3SI model is 3.58 eV. Figure 3a) The band gaps of the Mg, Ca, Sr, and Ba doped models are 3.30 eV, 3.40 eV, 3.34 eV, and 3.27 eV, respectively, which are close to those of the undoped model; the band gaps of the Al and Ga doped models are 1.78 eV and 2.39 eV, respectively. Figure 3 e and Figure 4 (g) It can be seen that defect energy levels appear in the band gap of these two doping models, leading to a decrease in the band gap value. Electrons occupying the impurity state are more likely to jump to the conduction band, causing leakage in the electrolyte material. The Mg, Ca, Sr, and Ba doping models have larger band gap values, which can avoid leakage in practical applications and are suitable for performance control of solid electrolyte materials. In addition, the energy bands of the metal doping models are shifted to lower energy levels to varying degrees, indicating that the doped system has lower energy and higher stability. The DOS diagram shows that the valence band of Na3SI is mainly contributed by the p orbitals of S and the atomic orbitals of I ( Figure 3 (b) The conduction band is contributed by the atomic orbitals of Na, S, and I. For the Mg doping model ( Figure 3 d) The valence band is mainly composed of the p orbitals of S and the atomic orbitals of I, while the conduction band is contributed by the atomic orbitals of Na, Mg, S, and I, with no obvious defect states; the DOS diagrams of the Ca, Sr, and Ba doping models are similar, with the doped atomic orbitals mainly contributing to the conduction band. Figure 4 b, d, f). The band structures of the Al and Ga doped models exhibit distinct donor impurity levels, which are represented as corresponding defect states in the DOS diagram: In the Al doped model, Al, S, and I atoms undergo orbital hybridization to form defect states ( Figure 3 f), the valence band is mainly composed of the p orbitals of S and the atomic orbitals of I, while the conduction band is contributed by the atomic orbitals of Na, Al, S, and I; the DOS diagrams of the Ga-doped model and the Al-doped model show similar atomic orbital contribution characteristics. The DOS diagram of Na3SI shows a small overlap area between positive and negative ions, indicating weak hybridization between different orbitals. Therefore, it is inferred that the chemical bonds in Na3SI are mainly ionic bonds. Figure 3 b). The DOS diagrams for the Mg, Ca, Sr, and Ba doping models are similar to those for Na3SI ( Figure 3 d、 Figure 4 (b, d, f). Based on electronic structure performance analysis, Mg, Ca, Sr, and Ba doping can enhance system stability while maintaining the large band gap of Na3Si (avoiding leakage), making them suitable for performance optimization of solid electrolytes; while Al and Ga doping introduce defect energy levels, reduce the band gap, and increase the risk of leakage, making them unsuitable as doping elements for solid electrolytes.

[0026] Bader charge analysis reveals interatomic interactions and the number of electrons around each atom in the Na3SI doped system. The sign of the Bader charge reflects the direction of charge transfer in the anti-perovskite material: positively charged atoms gain electrons, and negatively charged atoms lose electrons. Table 2 lists the Bader charges of each atom in the six Na3SI doping models: in the Na3SI model, the Bader charges of Na, S, and I atoms are -0.80, 1.49, and 0.90, respectively, indicating that a Na atom loses 0.8 electrons, and a S atom and an I atom gain 1.49 and 0.9 electrons, respectively; the net Bader charge of the Na3SI compound is close to zero, indicating that electrons are transferred from Na to S and I atoms. The Bader charge is close to the number of valence electrons of each atom, indicating that the atoms in the Na3SI model are highly ionized. + S 2- and I - They are bonded together by Coulomb attraction to form a solid structure. The Bader charges of Na, S, and I atoms in the doping model are close to those in the Na3SI model, but the Bader charges of the doped atoms differ significantly: Mg, Ca, Sr, and Ba atoms lose about 1.4 electrons, which is close to their valence electron number; Al atoms lose 0.74 electrons, and Ga atoms lose 0.41 electrons, which is significantly different from their valence electron number (+3), indicating that Al and Ga atoms are not completely ionized.

[0027] Table 2 Bader charge for Na3SI and metal doping models;

[0028] When atoms form crystals, the charge within the system redistributes, and the differential charge density can intuitively reflect the charge distribution state and bonding ability. To study the effect of metal atom (Mg, Ba, Ca, Sr, Al, Ga) doping on the charge distribution in Na3SI, the differential charge density of the Na3SI doping model was calculated. On the (110) crystal plane ( Figure 5 The blue and green areas represent charge depletion, while the red and yellow areas represent charge accumulation. The differential charge map of Mg-doped Na3SI shows that the Mg and Na atoms are surrounded by blue areas with similar charge distributions, while the S and I atoms are surrounded by electron accumulation regions. Figure 5 a) indicates that Mg and Na atoms are highly ionized, with electrons transferred to S and I atoms. In the Na3SI model doped with Ca, Sr, and Ba atoms ( Figure 5In the Al and Ga doping models, electrons mainly transfer from cations to anions, but a small amount of charge accumulates around the doped atoms. Although Mg, Ca, Sr, and Ba atoms belong to the same group and have the same number of valence electrons, the Coulomb attraction between the nucleus and electrons increases with increasing atomic number: Mg has lower electronegativity, while Ca, Sr, and Ba have higher electronegativity, and the electrons ionized from them cannot be completely transferred to S and I atoms. Therefore, there is significant electron accumulation between Ca, Sr, Ba, and S atoms, indicating the existence of covalent bonds between these atoms. In the Al and Ga doping models, the charge distribution around the doped atoms is represented by the blue region (…). Figure 5 (e, f) indicates electron depletion, which may be due to partial ionization of Al and Ga atoms, with only one electron in the p orbital ionizing and transferring to the anion. This result is consistent with Bader charge analysis. In summary, Bader charge analysis and differential charge density results corroborate each other: Na3SI in the Mg, Ca, Sr, and Ba doping models has a high degree of ionization, mainly bonded by ionic bonds (a small number of covalent bonds exist in the Ca, Sr, and Ba doping models); while Al and Ga, due to incomplete ionization, show significantly different charge distribution and bonding characteristics in their doping models compared to the former.

[0029] Mechanical properties can predict a material's mechanical stability and resistance to deformation; solid electrolyte materials possess a certain degree of toughness, which facilitates good contact with electrode materials. Elastic constants Describing the deformation properties of materials, it can reflect structural stability, bonding characteristics between adjacent atomic planes in crystalline materials, and bonding anisotropy. The mechanical properties of Na3SI and metal-doped models are analyzed using elastic constants: all models belong to cubic lattices and have three independent elastic constants. , and The elastic constants of the compounds are listed in Table 3. The mechanical stability of the compounds is determined by the following criteria: The results show that the elastic constants of Na3SI and each doped model satisfy the mechanical stability criterion, and it is preliminarily determined that the studied models all have mechanical stability. Based on the elastic constants, the linear modulus and other parameters are derived through the standard relation (Equation 2), and the shear modulus (G) and bulk modulus (B) are calculated using the Voigt-Reuss-Hill approximation model.

[0030] ; ; ; (2); ; ; ; Young's modulus (E) quantifies the stiffness of a material; a higher value indicates greater stiffness. Table 3 shows that the Young's modulus of all metal-doped models is lower than that of undoped Na3SI, indicating that metal doping leads to a decrease in material stiffness. Toughness and brittleness are important parameters reflecting the practicality of solid-state electrolyte materials: the Pugh criterion correlates the plasticity of a material with the B / G ratio, using approximately 1.75 as the boundary to distinguish between tough and brittle materials; a B / G ratio greater than 1.75 indicates a tough material, and less than 1.75 indicates a brittle material. In this study, the B / G ratios of all models are mostly around 1.75, with the pure Na3SI, Sr-Na3SI, and Al-Na3SI models having ratios slightly less than 1.75, indicating that these compounds are slightly brittle; the B / G ratios of other doped models are all greater than 1.75, exhibiting toughness characteristics. Poisson's ratio (… The Poisson's ratio is used to evaluate the toughness and brittleness of materials: materials with a Poisson's ratio less than 0.26 are considered brittle, while those greater than 0.26 are considered tough. Here, the Poisson's ratios of the Na3SI, Sr-Na3SI, and Al-Na3SI models are less than or equal to 0.26, and are classified as brittle materials; other doping models have a Poisson's ratio greater than 0.26, exhibiting toughness. This result is consistent with the conclusions obtained from the Pugh criterion. Therefore, based on mechanical property analysis, metal atom doping does not destroy the mechanical stability of Na3SI, but it reduces its stiffness; Mg, Ca, Ba, and Ga atom doping can improve the toughness of the material, which is beneficial for the assembly of energy storage devices.

[0031] Ionic conductivity is closely related to the application of anti-perovskite materials in solid-state electrolytes; the higher the ionic conductivity, the more suitable the material is for high-performance solid-state electrolytes. This work uses AIMD simulations to calculate the activation energy and ionic conductivity of sodium ions in anti-perovskite: sodium ion vacancies are constructed in a 2×2×2 supercell to study the Na... + The migration behavior was studied; the total AIMD simulation duration was 120 ps, ​​with a time step of 2 fs, and the first 10 ps were used for the system to reach equilibrium; the simulation temperature range was 300 K-1300 K (temperature intervals of 100 K). The mean square displacement (MSD) of sodium ions was extracted from the AIMD data, the diffusion coefficient (D) of the material was calculated, and the activation energy of the material was derived using the Arrhenius relation. ), and used the Nernst-Einstein relation to convert the diffusion coefficient into electrical conductivity ( The relevant formulas are as follows: ; (3); Taking the logarithm of the diffusion coefficients of Na3SI and each doping model, the relationship between logD and 1000 / temperature was obtained. The activation energy was calculated from the slope by linearly fitting the curve. Figure 6 a). The activation energy range is 0.27 eV-0.68 eV, which is consistent with the results reported in the literature (Na). 2.875 The activation energy of OCl is 0.42 eV, and that of Na3OBr is... 0.5 I 0.5 The activation energy is 0.69 eV. The activation energies of Ca and Sr-doped Na3SI are lower than those of the Na3SI model, indicating that these two dopants can reduce the activation energy. Migration barriers, promoting Na+ migration is facilitated; conversely, Mg and Al atom doping significantly increases the activation energy, which is unfavorable for Na+ migration. The conductivity of each model at 300 K was calculated using the Nernst-Einstein relation. Figure 6 (b) The results show that the room-temperature conductivity of both the undoped Na3SI and metal-doped models is within a reasonable range. The conductivity of the undoped Na3SI model is... , and the literature reports The conductivity of the metal-doped models is significantly higher than that of the Na3SI model, with the ionic conductivity of Mg, Ca, Sr, and Ba-Na3SI being approximately [missing value]. The maximum value of the Sr-Na3SI model is The ionic conductivity of Al and Ga-Na3Si is approximately The maximum value of the Ga-Na3SI model is The room-temperature conductivity of the Al and Ga atom-doped models is significantly higher, which may be due to the strong electronegativity of these two atoms, forming negatively charged centers, thereby promoting the formation of positively charged atoms. migrate.

[0032] The ionic conductivity of the electrolyte material is also affected by the operating temperature of the solid-state battery. This work compares the MSD (Mean Displacement) of various ions using the Na3SI model at 800 K, 1000 K, and 1200 K. Figure 7 The results showed that, at different temperatures, the main migrating ions in the Na3SI model were all... S 2- and I - Almost no migration; as temperature rises, The migration rate is improved, while S 2- and I - The migration of these particles remains extremely weak, indicating that their movement is mainly confined to the vicinity of their equilibrium positions. This demonstrates that increasing temperature does not destroy the structure of Na3SI, indicating its high stability. (In the metal doping model...) The migration of [elements] exhibits different trends with temperature changes: Figure 6 c shows the Na3SI and metal doping models in the temperature range of 500 K to 1300 K. At an MSD of 10000 fs, the results indicate that the migration of sodium ions in the metal-doped model is greater than that in the Na3SI model at low temperatures. Figure 6 The results for b are consistent; as temperature increases, the MSD of all models increases at different rates, with the Ca, Sr, Ba-Na3SI, and Na3SI models showing the most significant increases. The migration rate is relatively high, while the Mg, Al, and Ga doping models... The migration rate is relatively slow, possibly due to the small atomic radii of Mg, Al, and Ga, which leads to lattice shrinkage and distortion, hindering migration. The diffusion of [the material / mechanism] was observed. All models were structurally stable at 1000 K, and the diffusion of [the material / mechanism] within the models was investigated at this temperature. Changes in MSD over time ( Figure 6 d) The results show that the Na⁺ movement rate is faster in the Ca, Sr, Ba-Na₃SI and Na₃SI models, while it is faster in the Mg, Al, and Ga-Na₃SI models. The movement speed is relatively slow, in all models The migration follows a consistent pattern with time and temperature. Combined with activation energy analysis, it was found that the metal doping model with low activation energy... Metal doping models with high migration rates and conversely high activation energies. The migration rate is low. In summary, at low temperatures, the ionic conductivity of the metal-doped model is higher than that of the undoped Na3SI model; as the temperature increases, the ionic conductivity of all models decreases. The migration rates all increased, and the Ca, Sr, and Ba-Na3SI models... The migration rate is significantly higher than that of the Mg, Al, Ga-Na3SI model. This may be due to the smaller atomic radii of Mg, Al, and Ga, leading to lattice shrinkage near the doped atoms. The diffusion channels narrow; the activation energy results also indicate that in the Ca, Sr, Ba-Na3SI model... With lower activation energy, they diffuse more easily from lattice sites. Therefore, sodium-rich anti-perovskite materials doped with Ca, Sr, and Ba metal atoms can adapt to a wide operating temperature range and have high ionic conductivity.

[0033] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material, characterized in that: The method is to use sodium-rich anti-perovskite Na3SI as a matrix and replace some of the Na atoms in the matrix by doping with at least one metal atom selected from Ca, Sr and Ba. The material has a crystal structure belonging to the Pm-3m space group, with lattice parameters satisfying a=b=c=10.0-11.0 Å, α=β=γ=90°, a formation energy ≤-1.14 eV, a band gap of 3.27-3.40 eV, and a room temperature ionic conductivity of [missing information]. .

2. The Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material according to claim 1, characterized in that: When the doped atom in the material is Sr, the formation energy is -1.28 eV, and the room temperature ionic conductivity can reach [value missing]. .

3. The Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material according to claim 1, characterized in that: The elastic constant of the material satisfies C 11 =37.11-37.80 GPa, C 12 =4.30-8.42GPa, C 44 =5.78-6.68 GPa, and meets the mechanical stability criterion C. 11 >C 12 C 44 >0, C 11 +2C 12 >0.

4. The Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material according to claim 1, characterized in that: The material has a bulk modulus B = 15.47-17.98 GPa, a shear modulus G = 9.00-9.33 GPa, a Young's modulus E = 22.61-23.61 GPa, a B / G ratio ≥ 1.72, and a Poisson's ratio v ≥ 0.

26.

5. The Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material according to claim 1, characterized in that: Na in the material + The activation energy is 0.27-0.31 eV, and in the temperature range of 300K-1300K, Na... + As the main migrating ion, S 2- and I - They hardly migrate.

6. A method for preparing a Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material, based on the Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material according to any one of claims 1-5, characterized in that: Includes the following steps: Step 1: Using Na3SI as the matrix, construct a Na3SI cubic unit cell, in which Na atoms occupy vertex positions, S atoms are located at face-centered positions, and I atoms are located at body-centered positions; Step 2: Expand the cubic unit cell into a 2×2×2 supercell, replace one Na atom in the supercell with at least one metal atom from Ca, Sr, and Ba, and construct a doping model; Step 3: Optimize the structure of the doped model using density functional theory and the Vienna ab initio simulation software package. The optimization parameters are: Using the PBE generalized gradient approximation exchange-correlated functional and the projected fused wave method, a 5×5×5k-point grid centered at Γ point is employed, with a plane wave cutoff energy of 550 eV and atomic relaxation forces. Electron step energy convergence accuracy 10 -6 eV; Step 4: Perform ab initio molecular dynamics simulation on the optimized doping model. The simulation temperature range is 300K-1300K, the total duration is 120ps, the time step is 2fs, and the first 10ps are used for system equilibration to obtain the target solid electrolyte material.

7. The method for preparing a Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material according to claim 6, characterized in that: After structural optimization in step three, the electronic band structure was calculated using the HSE06 functional, and the self-consistent field convergence criterion was 10. -6 eV.

8. The method for preparing a Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material according to claim 6, characterized in that: In step four, the plane wave cutoff energy simulated by AIMD is 400 eV, and the energy convergence threshold is 10 eV. -5 eV, the Brillouin zone is sampled only at the Γ point.

9. The Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material and method according to claim 6, characterized in that: In step four, the activation energy is derived from the diffusion coefficient using the Arrhenius relation, and the diffusion coefficient is converted into ionic conductivity using the Nernst-Einstein relation.

10. The Ca / Sr / Ba doped modified sodium-rich anti-perovskite solid electrolyte material and method according to claim 6, characterized in that: The chemical bonds in the material are mainly ionic bonds, with a small number of covalent bonds between Ca, Sr, Ba and S atoms. The atoms are highly ionized and there are no obvious defect energy levels.

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