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/mmc LiP, is not satisfactory due to its poor conductivity. In this article we explore the highpressure phase diagram of the Li-P system through firstprinciples swarm-intelligence structural search and present two hitherto unknown stable Li-rich compounds, Fm-3m LiP at 4.2 GPa and P6/mmm LiP at 10.3 GPa. Metallic LiP 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 LiP reaches 4326 mAhg, 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.This research was supported by Natural Science Foundation of China under No. 21573037, the Postdoctoral Science Foundation of China under grant 2013M541283, and the Natural Science Foundation of Jilin Province (20150101042JC). A.B. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (FIS2016-76617-P) and the Department of Education, Universities and Research of the Basque Government and the University of the Basque Country (IT756-13).Peer Reviewe