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

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.