Unparalleled Lithium and Sodium Superionic Conduction in Solid Electrolytes with Large Monovalent Cage-like Anions

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Organic liquid electrolytes in rechargeable batteries have limitations.
• Solid electrolytes offer potential solutions but require high conductivity and stability.
• Previous research identified Na2B12H12 and Li2B12H12 salts with high conductivity but high transition temperatures.

Purpose of the Study:

• To investigate chemically related LiCB11H12 and NaCB11H12 salts as potential solid electrolyte materials.
• To determine the ionic conductivity and phase transition temperatures of these novel salts.
• To assess their suitability for next-generation all-solid-state batteries.

Main Methods:

• Synthesis and characterization of LiCB11H12 and NaCB11H12 salts.
• Measurement of ionic conductivity at various temperatures.
• Determination of phase transition temperatures through thermal analysis.

Main Results:

• LiCB11H12 and NaCB11H12 exhibit significantly lower phase transition temperatures (around 400 K and 380 K, respectively) compared to previously studied salts.
• Both salts demonstrate excellent ionic conductivities exceeding 0.1 S cm⁻¹ at these lower temperatures.
• The monovalent CB11H12⁻ anion enables lower transition temperatures while maintaining high conductivity.

Conclusions:

• LiCB11H12 and NaCB11H12 represent promising solid electrolyte materials with high ionic conductivity at accessible temperatures.
• The use of large polyhedral anions like CB11H12⁻ is a viable strategy for developing room-temperature superionic solid electrolytes.
• These findings pave the way for practical all-solid-state batteries with enhanced safety and performance.