Boron-Doped Graphite Intercalation Compounds as Mixed Ionic–Electronic Conductors

Abstract

Mixed ionic–electronic conductors (MIECs) are of great significance in electrode and interface design, but their transport mechanisms and high-temperature stability still require further understanding and exploration. In this work, we employ molecular dynamics simulations based on machine learning force fields to investigate the superionic behavior of B-doped graphite intercalation compounds (CaB2C6, SrBC5, Sr2BC11, BaBC5, and Ba2BC11). Within an assumed carrier concentration range of 1014–1020 cm–3, these systems exhibit electronic conductivities of 105–107 S·m–1; at temperatures above 1300 K, the ionic conductivity reaches the order of 10–2 S·cm–1. For CaB2C6 with a defect concentration of 5.56%, the superionic transition temperature can be further reduced to 600 K. The analysis indicates that the vacancy mechanism drives the diffusion of alkaline-earth metal ions, while strong covalent bonds ensure the stability of the B–C layer framework. Different activation energies account for the differences in the superionic state transition temperature. Moreover, these materials exhibit favorable thermal stability and mechanical properties, providing a theoretical reference for the development of MIEC candidates for high-temperature tolerance and interface-enhancing materials.