Elucidating and Optimizing I Occupation in Lithium Argyrodite Solid Electrolytes for Advanced All-Solid-State Li...

Area of Science:

• Solid-state chemistry
• Materials science
• Electrochemistry

Background:

• Lithium argyrodite sulfide electrolytes are promising for solid-state batteries.
• Understanding the role of halogen doping, specifically iodine, on ionic conductivity is crucial.

Purpose of the Study:

• To investigate the influence of iodine (I) occupancy on the ionic conductivity of Li6PS5Cl.
• To elucidate the mechanism of enhanced ion transport through theoretical calculations and experimental synthesis.

Main Methods:

• Ab initio molecular dynamics theoretical calculations to determine migration energy barriers.
• Synthesis of iodine-rich Li6-xPS5-xClIx electrolytes.
• Electrochemical characterization of Li symmetric cells and full cells.

Main Results:

• Incorporation of excess iodine at sulfur sites lowers the Li+ migration energy barrier to 0.28 eV, enhancing ionic diffusion.
• Synthesized iodine-rich electrolytes exhibit high ionic conductivity.
• Stable Li/electrolyte interfaces were achieved, inhibiting side reactions and lithium dendrite growth.
• Li symmetric cells demonstrated excellent cyclic stability (7000 h at 0.1 mAh cm-2).

Conclusions:

• Iodine doping significantly improves ionic conductivity in Li6PS5Cl electrolytes.
• The optimized electrolytes enable stable and high-performance lithium batteries across various conditions.
• This study provides fundamental insights into structure-ion transport relationships in argyrodite electrolytes.