A method for improving zinc ion transmission performance of TiSe2 by doping Sb

Abstract

The application discloses a method for improving zinc ion transmission performance of Sb-doped TiSe2, and mainly solves the problem of high diffusion energy barrier of zinc ions in a TiSe2 negative electrode material. x The most stable structure of TiSe2 (x=0, 0.056, 0.111, 0.167, 0.222, 0.278) is obtained; then the most stable zinc ion adsorption site is discussed, and the structure corresponding to the zinc ion adsorption system is obtained; on this basis, the Sb x The internal correlation between the Sb doping concentration (x) of TiSe2 and the zinc ion diffusion energy barrier thereof is studied, and the Sb 0.111 TiSe2 has the lowest zinc ion diffusion energy barrier (0.26 eV), which is significantly lower than the diffusion energy barrier (0.70 eV) of zinc ions in TiSe2. In addition, Sb 0.111 TiSe2 has good electrical conductivity and thermodynamic stability. The application opens up a new way for developing TiSe2-based zinc ion battery electrode materials with excellent rate performance.

Description

Technical Field

[0001] This invention belongs to the field of computational materials science, specifically relating to a method for improving the zinc ion transport performance of TiSe2 by doping it with Sb. Background Technology

[0002] Zinc-ion batteries, as an energy storage device, possess advantages such as high specific capacity, low cost, and environmental friendliness, and have broad application prospects. However, the rate performance of zinc-ion batteries still needs further improvement, and developing electrode materials with high zinc ion transport performance is an effective way to solve this problem. TiSe2 exhibits excellent electronic conductivity, and its unique sandwich layered structure provides abundant sites for metal ion adsorption and transport channels for metal ion diffusion. However, due to the large radius of zinc ions, rapid diffusion within TiSe2 remains difficult. Furthermore, the Se-Ti-Se layers exhibit weak van der Waals forces (vdW), providing a prerequisite and foundation for widening the interlayer spacing in TiSe2. On the other hand, Sb has a large atomic radius and exhibits a strong anchoring effect with the Se-Ti-Se layers of TiSe2. Based on this, this invention proposes a method for Sb-doped TiSe2 to precisely widen its interlayer spacing and designs an optimal Sb-doped TiSe2 system (Sb... 0.111 The diffusion barrier of zinc ions in TiSe2 is only 0.26 eV, which is significantly lower than its diffusion barrier in TiSe2 (0.70 eV). Summary of the Invention

[0003] The purpose of this invention is to provide a method for improving the zinc ion transport performance of TiSe2 by doping it with Sb, thus providing a theoretical basis and method for improving the rate performance of TiSe2-based zinc ion battery electrode materials. The specific implementation method is as follows:

[0004] Step 1: Use the structure search method to search Sb x TiSe2 and Sb x Ti 1-x The structure of Se2(x=0,0.056,0.111,0.167,0.222,0.278) is screened to obtain the most stable structure;

[0005] Step 2: Calculate and analyze Sb using the CPLAP software package and first-principles methods. x TiSe2 and Sb x Ti 1-x The formation energy of Se2 varies with the Sb concentration (x), and the Sb concentration is determined. x TiSe2 exhibits superior structural stability;

[0006] Step 3: Calculate and analyze Sbx The variation of the lattice constant (c) of TiSe2 along the c-axis with the Sb concentration (x);

[0007] Step 4: Calculate Sb x The density of states and band structure of TiSe2 (x = 0, 0.056, 0.111, 0.167, 0.222, 0.278) are analyzed, along with its electronic conductivity.

[0008] Step 5: Based on structural symmetry, construct zinc ions in Sb x The adsorption structures corresponding to different sites in TiSe2 (x=0,0.056,0.111,0.167,0.222,0.278) were analyzed, and the adsorption energies between them and zinc ions were calculated.

[0009] Step 6: Use the Climbing Elastic Band (CI-NEB) method to search for zinc ions in Sb x The optimal diffusion path of TiSe2 (x=0,0.056,0.111,0.167,0.222,0.278) was determined, and the corresponding zinc ion diffusion barriers were calculated and compared. This led to the discovery of the optimal diffusion path of Sb. 0.111 TiSe2 exhibits the best zinc ion diffusion performance;

[0010] Step 7: Use ab initio molecular dynamics (AIMD) to study Sb separately. 0.111 Thermal stability of TiSe2 at temperatures of 300K and 400K;

[0011] This invention addresses the difficulty of zinc ion diffusion between TiSe2 layers by proposing a method to enhance zinc ion transport performance using Sb-doped TiSe2, thereby obtaining a design scheme and technical route with optimal Sb-doped TiSe2 system. First, Sb is calculated and analyzed. x The intrinsic relationship between the structure, band gap, and electronic density of states of TiSe2 and the Sb concentration (x) is then calculated; x The zinc ion adsorption energies of TiSe2 (x = 0, 0.056, 0.111, 0.167, 0.222, 0.278) were determined to identify the most stable zinc ion adsorption sites. Then, the CI-NEB (Climbing Elastic Band) method was used to study the zinc ion adsorption on Sb. x The diffusion barrier of TiSe2 (x = 0, 0.056, 0.111, 0.167, 0.222, 0.278) varies with Sb doping concentration, thus identifying the optimal Sb-doped TiSe2 system. 0.111 TiSe2, Sb provided by this invention 0.111 TiSe2 not only has a low zinc ion diffusion barrier (0.26 eV), but also exhibits good thermal stability at temperatures of 300 K and 400 K. Attached Figure Description

[0012] The embodiments illustrated in the accompanying drawings will be described in detail below. The accompanying drawings are merely some embodiments of the present invention. In the accompanying drawings:

[0013] Figure 1 This is an overall flowchart of a method for improving the zinc ion transport performance of TiSe2 by Sb doping;

[0014] Figure 2 For Sb x TiSe2 and Sb x Ti 1-x The formation energy of Se2 (E) form );

[0015] Figure 3 The possible diffusion pathways of zinc ions in TiSe2 and their corresponding zinc ion diffusion barriers are shown.

[0016] Figure 4 For zinc ions in Sb 0.111 Possible diffusion pathways in TiSe2 and their corresponding zinc ion diffusion barriers;

[0017] Figure 5 For zinc ions in Sb x The diffusion barrier in TiSe2 (x = 0, 0.056, 0.111, 0.167, 0.222, 0.278) varies with the Sb doping concentration (x);

[0018] Figure 6 (a) is Sb 0.111 The total energy of TiSe2 changes with AIMD time (temperature 300K). Figure 6 (b) is Sb 0.111 The structure of TiSe2 after 9000 fs treatment (at a temperature of 300 K);

[0019] Figure 7 (a) is Sb 0.111 The total energy of TiSe2 changes with AIMD time (temperature 400K). Figure 7 (b) is Sb 0.111 The structure of TiSe2 after 9000 fs treatment (at a temperature of 400 K); Detailed Implementation

[0020] This embodiment provides a method for improving the zinc ion transport performance of TiSe2 by Sb doping, including the following steps:

[0021] With Sb xUsing TiSe2 as the research object, the effects of different Sb concentrations (x = 0, 0.056, 0.111, 0.167, 0.222, 0.278) on Sb were considered. x The structure, electronic conductivity, stability, and the influence of zinc ion diffusion barrier on TiSe2 were investigated. First, Sb was screened. x The most stable structure of TiSe2 was determined, and its band gap and electronic density of states were calculated. Then, the climbing elastic band (CI-NEB) method was used to calculate and compare the zinc ion concentration in Sb. x The diffusion energy barrier in TiSe2 (x=0,0.056,0.111,0.167,0.222,0.278) was determined to obtain its optimal zinc ion diffusion path. Comparison shows that Sb... 0.111 TiSe2 is the optimal Sb-doped TiSe2 system, possessing the lowest zinc ion diffusion barrier (0.26 eV); based on this, further calculations were performed on the Sb... 0.111 Thermodynamic stability of TiSe2. Figure 1 The overall process for a method to improve the zinc ion transport performance of TiSe2 by doping with Sb is presented.

[0022] The exchange correlation energy of electrons is handled using the Perdew-Burke-Ernzerh (PBE) method based on the generalized gradient approximation (GGA), and the projected added plane wave (PAW) method is used to describe the interaction between electrons and ions. The valence electrons of Ti, Se, and Zn are 3d... 2 4s 2 3D 10 4s 2 4p 4 and 3D 10 4s 2 The plane-wave cutoff energies for both the Ti-Se and Ti-Se-Sb systems were set to 520 eV. 3×3×4 and 6×6×8 k-point grids of Monkhorst-Pack (MP) type were used for structural optimization and electronic structure calculations of the TiSe2 system and its Sb-doped system, respectively. The convergence accuracies for force and energy were set to... and 10 -5 eV / atom. For Sb x TiSe2 and Sb x Ti 1-x The structure of Se2(x=0,0.056,0.111,0.167,0.222,0.278) is screened to obtain its most stable structure.

[0023] Research forms Sb x TiSe2 and Sb x Ti 1-xThe chemical potential conditions required for Se2 and the optimal Sb doping raw materials. To determine the composition of Sb-doped TiSe2 compounds to be Sb... x TiSe2, calculate and compare Sb respectively x TiSe2 and Sb x Ti 1-x The formation energy (E) of Se2 (x = 0, 0.056, 0.111, 0.167, 0.222, 0.278) form The specific calculation steps are as follows: First, calculate the Ti-Se system (including Sb2Se3, Ti...). 20 (Sb3Se)3, Ti2Sb, Ti5Sb3, Ti3Sb, TiSb2, Ti 13 The formation enthalpy of Sb3 and TiSb was determined; then, the relative chemical potential of Ti (Δμ) was obtained by analyzing it using CPLAP software. Ti The relative chemical potentials (Δμ) of Se and Se Se The values ​​of ) are in the range of -3.34eV ≤ Δμ Ti ≤0 eV and -1.93 eV ≤ Δμ Se ≤-0.71eV. Then according to Δμ Ti and Δμ Se The value of Sb is calculated for the Sb-doped TiSe2 system (Sb x The formation energy of TiSe2) was determined, and its optimal growth conditions were further analyzed. Based on Sb x Elemental composition of TiSe2, calculate Sb2Se3, Ti 20 (Sb3Se)3, Ti2Sb, Ti5Sb3, Ti3Sb, TiSb2, Ti 13 The formation enthalpy of Sb3 and TiSb. Based on the formation enthalpy of these compounds and the constraint condition of the relative chemical potential required for TiSe2, the relative chemical potential of Sb (Δμ) is determined. Sb The value of Sb is then calculated according to equations (2-1) and (2-2). x TiSe2 and Sb x Ti 1-x The formation energy of Se2 (E) form The calculation results show that as the Sb concentration (x) increases, Sb... x The formation energies of TiSe2 are all lower than those of Sb. x Ti 1-x The formation energy of Se2 indicates that Sb x TiSe2 exhibits superior structural stability, with Sb most readily occupying the octahedral interstitial sites between TiSe2 layers. (Except for Ti...) 20 Besides (Sb3Se)3, the other seven Ti-Se compounds can be used as raw materials for the synthesis of stable Sb doping. xTiSe2.

[0024] E form =E tot (Sb x TiSe2)-E tot (TiSe2)-x(Δμ Sb +μ Sb (2-1)

[0025] E form =E tot (Sb x Ti 1-x Se2)-E tot (TiSe2)-x(Δμ Sb +μ Sb )+x(Δμ Ti +μ Ti (2-2)

[0026] Where E tot (Sb x TiSe2), E tot (Sb x Ti 1-x Se2) and E tot (TiSe2) represent Sb x TiSe2, Sb x Ti 1-x The total energy of Se2 and TiSe2. x represents the Sb concentration or Ti concentration. Δμ Sb and Δμ Ti μ represents the relative chemical potentials of elements Sb and Ti, respectively. Ti μ Se and μ Sb These represent the total energy of a single Ti, a single Se, and a single Sb, respectively.

[0027] Based on this, Sb is calculated according to equation (2-3). x The rate of change (Δc) of the lattice constant of TiSe2 along the c-axis was found to be Sb x The lattice constant of TiSe2 along the c-axis increases continuously with the increase of Sb doping concentration (x), which not only provides suitable storage space for zinc ions, but also provides a driving force for the free diffusion of zinc ions in it.

[0028]

[0029] in, and Sb x The lattice constants of TiSe2 and TiSe2 along the c-axis.

[0030] Calculate Sbx The electronic density of states and band gap of TiSe2 (x = 0, 0.056, 0.111, 0.167, 0.222, 0.278) are calculated, and its electronic conductivity is analyzed. First, spin polarization is considered, and Sb is calculated. x The total electronic density of states of TiSe2 (x = 0.056, 0.111, 0.167, 0.222, 0.278) shows symmetry between its spin-up and spin-down bands, indicating that Sb x TiSe2 exhibits non-spin polarization characteristics; then its band structure and corresponding partial-wave electronic state density are calculated, Sb x TiSe2 (x=0,0.056,0.111,0.167,0.222,0.278) has bands that all cross the Fermi level, exhibiting excellent electronic conductivity.

[0031] Determine zinc ions in Sb x Intercalation sites in TiSe2. The zinc ion occupancy in Sb is calculated according to equation (2-4). x The adsorption energies (E) corresponding to different adsorption sites of TiSe2 ad It can be seen that zinc ions tend to occupy the interstitial sites of the Sb layer.

[0032]

[0033] in and E Zn Sb x The total energy of zinc ion adsorption by TiSe2 (x=0,0.056,0.111,0.167,0.222,0.278), Sb x The total energy of TiSe2 and the energy of a single zinc atom.

[0034] Zinc ion concentration in Sb was calculated using the Climbing Elastic Band (CI-NEB) method. x The diffusion barrier in TiSe2 (x=0,0.056,0.111,0.167,0.222,0.278) is determined to obtain its optimal diffusion path. First, the diffusion barrier of Sb is... x Two adjacent equivalent zinc ion-occupied structures in TiSe2 are used as the initial and final states in the zinc ion diffusion path, respectively. The distance between the initial and final states is then measured, and the number of transition states is determined based on this value. This invention utilizes Sb... x Four transition states are inserted between the initial and final states of TiSe2, forming the diffusion pathway for zinc ions. Based on Sb x The structural characteristics of TiSe2 and its coordination mode with zinc ions were considered, taking into account two zinc ion pathways in Sb 0.111 There may be two different diffusion pathways in TiSe2 (see...) Figure 4Path1 and Path2 in the model are used to compare the zinc ion diffusion barriers (e.g., Path1 and Path2 in the model). Figure 4 (as shown); based on this, the relationship between Sb concentration (x) and Sb was studied. x The relationship between the zinc ion diffusion barriers of TiSe2, thereby further obtaining Sb 0.111 TiSe2 represents the optimal Sb-doped TiSe2 structure, exhibiting the lowest zinc ion diffusion barrier (0.26 eV), which is significantly lower than the zinc ion diffusion barrier in TiSe2 (0.70 eV). Therefore, Sb 0.111 TiSe2 exhibits optimal zinc ion diffusion performance. Therefore, this invention proposes Sb-doped TiSe2 as an effective method to improve its zinc ion diffusion performance.

[0035] Excellent thermal stability is an essential requirement for electrode materials. The ab initio molecular dynamics (AIMD) method was used to further investigate Sb... 0.111 Thermal stability of TiSe2 at 300 K and 400 K. Analysis of Sb 0.111 The variation of the total energy of TiSe2 at this temperature with AIMD running time was observed, and its structure after 9000 fs processing was obtained. From Figure 6 (a) and Figure 7 (a) It can be seen that at temperatures of 300K and 400K, Sb 0.111 The total energy of TiSe2 showed a stable distribution with AIMD time. Furthermore, after heat treatment at 300K and 400K, Sb... 0.111 The structure of TiSe2 did not show obvious structural distortion, which further proves that Sb 0.111 TiSe2 exhibits excellent thermal stability at temperatures of 300K and 400K.

[0036] Finally, it is necessary to state that the specific embodiments described above are merely illustrative of or explanations of the principles of the present invention, and do not constitute a limitation thereof. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention.

Claims

1. A method for improving the zinc ion transport performance of TiSe2 by Sb doping, the method comprising the following steps: Step 1: Use the structure search method to search Sb x TiSe2 and Sb x Ti 1-x Se2 is used to screen structures to obtain the most stable structures of both, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.278; Step 2: Calculate and analyze Sb using the CPLAP software package and first-principles methods. x TiSe2 and Sb x Ti 1-x The formation energy of Se2 varies with the Sb concentration (x), and the Sb concentration is determined. x TiSe2 exhibits superior structural stability; Step 3: Calculate and analyze Sb x The variation of the lattice constant (c) of TiSe2 along the c-axis with the Sb concentration (x); Step 4: Calculate Sb x The density of states and band structure of TiSe2 were analyzed, and its electronic conductivity was determined, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.

278. Step 5: Based on structural symmetry, construct zinc ions in Sb x The adsorption structures corresponding to different sites in TiSe2 were determined, and the adsorption energies between them and zinc ions were calculated, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.278; Step 6: Use the Climbing Elastic Band (CI-NEB) method to search for zinc ions in Sb x The optimal diffusion path in TiSe2 was determined and the corresponding diffusion barrier was calculated. Sb was found to be... 0.111 TiSe2 exhibits the best zinc ion diffusion performance, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.278; Step 7: Use ab initio molecular dynamics (AIMD) to study Sb separately. 0.111 Thermal stability of TiSe2 at temperatures of 300K and 400K.

2. The method for improving the zinc ion transport performance of TiSe2 by Sb doping according to claim 1, characterized in that, In step 1, a structure search method is used to search Sb. x TiSe2 and Sb x Ti 1-x The Se2 structure was screened to obtain the most stable structure, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.

278.

3. The method for improving the zinc ion transport performance of TiSe2 by Sb doping according to claim 1, characterized in that, In step 2, the Sb formation energy is studied using the CPLAP software package and the method of calculation. x The structural stability of TiSe2, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.278, is determined by the following steps: Step 2.1: Obtain the structures of Ti-Se compounds from the Materials Project database, including TiSe, Ti9Se2, Ti8Se3, Ti5Se4, Ti3Se4, Ti2Se, Ti2Se3, and Ti... 45 Se 16 Ti 19 Se 20 Ti 11 Se4 and Ti3Se; Step 2.2: Calculate the formation enthalpy (ΔH) of the Ti-Se compound. f ); Step 2.3: Based on the relative chemical potential condition required for the formation of stable TiSe2: Δμ Ti and Δμ Se Research forms Sb x The growth conditions required for TiSe2, where Δμ Ti and Δμ Se The following conditions should be met (see Equations 1-1 to 1-15): Step 2.4: Obtain Δμ using CPLAP software. Ti and Δμ Se The values ​​range for Δμ are -3.34 eV ≤ Δμ Ti ≤0 eV and -1.93 eV ≤ Δμ Se ≤-0.71eV; according to Δμ Ti and Δμ Se The value of is used to calculate the formation energy of the Sb-doped TiSe2 system, and further obtain the conditions for the chemical potential required to form a stable Sb-doped TiSe2 system. Step 2.5: According to Sb x The composition of TiSe2 was calculated, and the values ​​of Sb2Se3 and Ti were determined. 20 (Sb3Se)3, Ti2Sb, Ti5Sb3, Ti3Sb, TiSb2, Ti 13 The formation enthalpy of compounds such as Sb3 and TiSb is used to determine the relative chemical potential Δμ of Sb. Sb The range of values ​​for; Step 2.6: Calculate Sb according to equations (1-16 to 1-17). x TiSe2 and Sb x Ti 1-x The formation energy E of Se2 form Compare the stability of these two; AND form =E tot (Sb x TiSe2)-E tot (TiSe2)-x(Δμ Sb +μ Sb ) (1–16) AND form =E tot (Sb x You 1-x Se2)-E tot (TiSe2)-x(Δμ Sb +μ Sb )+x(Δμ Ti +μ Ti ) (1–17) Where E tot (Sb x TiSe2), E tot (Sb x Ti 1-x Se2) and E tot (TiSe2) represent Sb x TiSe2, Sb x Ti 1-x The total energy of Se2 and TiSe2; x is the Sb concentration or Ti concentration; Δμ Sb and Δμ Ti The relative chemical potentials of elements Sb and Ti are respectively; μ Ti μ Se and μ Sb These represent the total energy of a single Ti, a single Se, and a single Sb, respectively.

4. The method for improving the zinc ion transport performance of TiSe2 by Sb doping according to claim 1, characterized in that, In step 3, Sb is calculated and analyzed. x The variation of the lattice constant (c) of TiSe2 along the c-axis with Sb concentration (x); the specific steps are as follows: Step 3.1: Take the Sb obtained in Step 1 x Data analysis was performed on the most stable structure of TiSe2 to obtain its lattice constant along the c-axis, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.278; Step 3.2: Calculate Sb according to equation (1-18). x The rate of change (Δc) of the lattice constant of TiSe2 along the c-axis was found to be Sb x The lattice constant of TiSe2 along the c-axis increases continuously with the increase of Sb doping concentration (x), which not only provides suitable storage space for zinc ions, but also provides a driving force for the free diffusion of zinc ions in it; in, and Sb x The lattice constants of TiSe2 and TiSe2 along the c-axis.

5. The method for improving the zinc ion transport performance of TiSe2 by Sb doping according to claim 1, characterized in that, In step 4, Sb x The band structure and electronic density of states of TiSe2 were calculated to analyze the electronic conductivity of the Sb-doped TiSe2 system, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.278; the specific steps are as follows: Step 4.1: Perform static calculations on the TiSe2 and its Sb-doped system obtained in Step 1. Set the Brillouin zone k-point grid of Monkhorst-Pack (MP) type to 6×6×8. Step 4.2: Use the output file obtained in Step 4.1 to calculate the band structure and electronic density of states of TiSe2 and its Sb-doped system.

6. The method for improving the zinc ion transport performance of TiSe2 by Sb doping according to claim 1, characterized in that, In step 5, based on structural symmetry, zinc ions occupy Sb... x The adsorption structures corresponding to different sites of TiSe2 were analyzed, and the corresponding zinc ion adsorption energies (E) were calculated according to equation (1-19). ad It was found that zinc ions readily occupy interstitial sites in octahedrons containing Sb layers; in and E Zn Sb x The total energy of zinc ion adsorption by TiSe2, Sb x The total energy of TiSe2 and the energy of a single zinc atom, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.

278.

7. The method for improving the zinc ion transport performance of TiSe2 by Sb doping according to claim 1, characterized in that, In step 6, the climbing elastic band (CI-NEB) method is used to search for zinc ions in Sb. x The optimal diffusion path in TiSe2 yields Sb 0.111 TiSe2 exhibits the best zinc ion diffusion performance, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.278; the specific steps are as follows: Step 6.1: Obtain the most stable Sb in step 4 x Based on the TiSe2 zinc ion adsorption system, we searched for its adjacent equivalent zinc ion adsorption sites, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.278; Step 6.2: Place Sb x Two adjacent equivalent zinc ion adsorption sites of TiSe2 were set as the initial and final states of its zinc ion diffusion path, and the distance between them was measured. Then, based on the relationship between this distance and the transition state spacing, the number of inserted transition states was obtained, thereby designing the zinc ion adsorption path in Sb. x Possible diffusion paths in TiSe2, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.278; Step 6.3: Optimize zinc ion concentration in Sb using the climbing elastic band (CI-NEB) method. x The diffusion pathways in TiSe2 were determined, and the corresponding zinc ion diffusion barriers were obtained, where x = 0, 0.056, 0.111, 0.167, 0.222, 0.

278.

8. The method for improving the zinc ion transport performance of TiSe2 by Sb doping according to claim 1, characterized in that, In step 7, the ab initio molecular dynamics (AIMD) method is used to determine Sb. 0.111 TiSe2 exhibits good thermal stability at both 300K and 400K.

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