Pressure-Induced Stable Li5P for High-Performance Lithium-Ion Batteries

Black phosphorus, the result of white P under high pressure, has received much attention as a promising anode material for Li-ion batteries (LIBs). However, the final product of lithiation, P6(3)/mnic Li3P, is not satisfactory due to its poor conductivity. In this article we explore the high-pressure phase diagram of the Li-p system through first principles swarm-intelligence structural search and present two hitherto unknown stable Li-rich compounds, Fm-3m UP, at 4.2 GPa and P6/mmm Li5P at 10.3 GPa. Metallic Li5P exhibits interesting structural features, including graphene-like Li layers and P-centered octadecahedrons, where P is 14-fold coordinated with Li. Interestingly, both compounds exhibit good dynamical and thermal stability properties at ambient pressure, and the theoretical capacity of P6/mmm Li5P reaches 4326 mAhg(-1), the highest among the already known Li-P compounds. Additionally, their mechanical properties are also favorable for electrode materials. Our work represents a significant step toward the performance improvement of Li-P batteries and understanding Li-P compounds.