High-Pressure Investigation of the Phase Diagram of the C-N-Alkali Metal Systems

Ternary carbon nitrides systems are especially attractive, not only as they are terra incognita under extreme conditions and thus of fundamental interest, but also because they provide a means to functionalize the very robust networks resulting from corner-sharing CN4 units for the design of novel materials (meta)stable to ambient conditions. In particular, a CN4-based framework with large pores would be of significant interest in the context of battery anodes, enabling improved charge storage, fast ion transport and low volume expansion. In this context, the study of the Li-, Na-, and K-C-N systems, in which the alkali cations could help trigger the formation of the CN4 network at lower pressures and then be removed easily at ambient conditions. This study therefore aims to investigate the Li-, Na-, and K-C-N systems up to 125 GPa in laser-heated diamond anvil cells, characterizing the resulting polycrystallites with single-crystal X-ray diffraction methodology.