Superionic Transition in Mixed Conducting Graphite Intercalation Compounds CsC₈ and RbC₈

Area of Science:

• Materials Science
• Solid-State Chemistry
• Computational Physics

Background:

• Mixed ionic-electronic conductors (MIECs) are crucial for solid-state battery electrodes.
• Graphite intercalation compounds (GICs) are promising candidates for MIEC applications.

Purpose of the Study:

• Investigate ionic diffusion in CsC8 and RbC8 graphite intercalation compounds.
• Determine their potential as high-performance electrode materials for solid-state batteries.

Main Methods:

• First-principles calculations.
• Ab initio molecular dynamics simulations.

Main Results:

• CsC8 and RbC8 exhibit superionic transitions at 500 K and 600 K, respectively.
• Achieved ionic conductivities of 0.0127 S/cm (CsC8) and 0.0787 S/cm (RbC8).
• Electrical conductivities reached up to 10^7 S/m; RbC8 showed a stacking transition at 500 K.
• Defects reduced superionic transition temperature to 400 K.
• Identified Cs+ and Rb+ ion migration via vacancy mechanism through specific pathways.

Conclusions:

• CsC8 and RbC8 demonstrate excellent ionic and electronic conductivity.
• These MIECs possess good thermal stability and mechanical properties.
• Findings provide insights for designing advanced MIEC materials for energy storage.