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, P 6 3 / mmc Li 3 P, 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 -3 m Li 3 P at 4.2 GPa and P 6/ mmm Li 5 P at 10.3 GPa. Metallic Li 5 P 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 P 6/ mmm Li 5 P 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.