Fast Ionic Conductivity in the Most Lithium-Rich Phosphidosilicate Li₁₄SiP₆

Area of Science:

• Materials Science
• Solid-State Chemistry
• Electrochemistry

Background:

• All-solid-state batteries require solid electrolytes with high ionic conductivity for safe and efficient energy storage.
• Existing solid electrolytes face challenges in achieving both high conductivity and stability.
• Lithium phosphidotetrelates represent a promising class of materials for solid electrolytes.

Purpose of the Study:

• To synthesize and characterize a novel "lithium-rich" phosphidosilicate solid electrolyte.
• To investigate the ionic conductivity and lithium ion transport mechanisms within this new material.
• To expand the family of lithium phosphidotetrelates for potential battery applications.

Main Methods:

• Ball mill synthesis followed by thermal treatment to obtain the crystalline material.
• Temperature-dependent powder neutron diffraction and DFT calculations to analyze diffusion pathways.
• Maximum entropy method, impedance spectroscopy, and 7Li NMR spectroscopy to study lithium ion mobility.

Main Results:

• A novel crystalline "lithium-rich" phosphidosilicate with 3D conducting pathways was synthesized.
• The material exhibits superionic conductivity (σ > 10^-3 S cm^-1) at room temperature with low activation energy (30-32 kJ mol^-1).
• Analysis revealed lithium diffusion through both tetrahedral and octahedral voids, facilitated by disordered Li/Si occupancy.

Conclusions:

• The developed "lithium-rich" phosphidosilicate is a promising solid electrolyte for all-solid-state batteries.
• The material's structure and composition enable high lithium ion conductivity and mobility.
• This work contributes to the advancement of solid electrolyte materials for next-generation energy storage.