Harnessing Cation Disorder for Enhancing Ionic Conductivity in Lithium Inverse Spinel Halides

Area of Science:

• Materials Science
• Solid-State Chemistry
• Electrochemistry

Background:

• Halide solid-state electrolytes offer high stability and conductivity for lithium batteries.
• Current limitations include reliance on expensive and rare elements.
• The Li₂MgCl₄ inverse spinel system presents a potential cost-effective alternative.

Purpose of the Study:

• Investigate Li₂MgCl₄ as a practical solid-state electrolyte.
• Enhance ionic conductivity at room temperature through doping.
• Understand the mechanisms behind conductivity enhancement.

Main Methods:

• Utilized molecular dynamics simulations to study Li₂MgCl₄.
• Experimentally synthesized and characterized Li Zr_1-Mg Cl₄ systems.
• Measured ionic conductivity at room temperature.

Main Results:

• Molecular dynamics showed lithium disordering reduces activation energy in Li₂MgCl₄ at high temperatures.
• Zr doping in Li Zr_1-Mg Cl₄ induced cation disorder at room temperature.
• Li_1.25Zr_0.375Mg_0.625Cl₄ achieved a conductivity of 1.4 × 10^-5 S cm^-1, a two-order-of-magnitude increase.

Conclusions:

• Zr doping effectively stabilizes cation disorder at room temperature, enhancing ionic conductivity.
• Cation disordering to the 16c site is the primary driver of conductivity increase.
• Lithium vacancy concentration plays a minimal role in conductivity enhancement for this system.