Engineering Li₂ZrCl₆ with Ga³⁺/Ge⁴⁺ Doping for High Ionic Conductivity and Stable Interfaces in Solid-State...

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Lithium₂Zirconium Chloride (Li₂ZrCl₆) is a promising solid electrolyte due to its low cost and cathode compatibility.
• Its room-temperature ionic conductivity, however, is insufficient for widespread application in solid-state batteries.
• Elemental doping is a known strategy to enhance the ionic conductivity of solid electrolytes.

Purpose of the Study:

• To investigate the potential of doped Li₂ZrCl₆, specifically Li_2.5Zr_0.75Zn_0.25Cl₆, Li_2.25Zr_0.75Ga_0.25Cl₆, and Li₂Zr_0.75Ge_0.25Cl₆, as solid electrolytes.
• To analyze the atomic-scale mechanism of doping-induced enhancement in ionic conductivity.
• To evaluate the electrochemical window and phase stability of these doped materials.

Main Methods:

• First-principles density functional theory (DFT) calculations.
• Ab initio molecular dynamics (AIMD) simulations.
• Pymatgen tool for electrochemical window and phase stability analysis.

Main Results:

• The nature of the dopant and a lithium-rich strategy significantly influence Li⁺ conductivity, particularly in Li_2.25Zr_0.75Ga_0.25Cl₆.
• Li_2.25Zr_0.75Ga_0.25Cl₆ exhibits substantially improved ionic conductivity compared to pristine Li₂ZrCl₆.
• Enhanced conductivity in Li_2.25Zr_0.75Ga_0.25Cl₆ is attributed to a lower migration energy barrier and additional ion transport pathways in the ab plane.
• Gallium doping facilitates Li⁺ conduction at the interface between Li₂ZrCl₆ and Li₂S.

Conclusions:

• Elemental doping, especially with gallium, is an effective strategy to enhance the ionic conductivity of Li₂ZrCl₆ solid electrolytes.
• Understanding the microscopic mechanisms of doping-induced ion transport is crucial for designing advanced solid electrolytes.
• This research contributes to the development of high-performance solid electrolytes for all-solid-state batteries.