Predicted stable Li5P2 and Li4P at ambient pressure: novel high performance anodes for lithium-ion batteries

Lithium-rich phosphides have recently attracted considerable attention in their potential application as high-capacity and high-rate anodes for lithium-ion batteries (LIBs). However, it is still a lack of a promising candidate thus far because of the poor electrical conductivity or huge volume change in the already known Li-P compounds. In this work, we herein report two novel Li-P states as Li5P2 and Li4P stabilized under high pressures that are predicted to be quenchable down to ambient conditions by first-principles swarm structure calculations. The predicted P3m1 Li5P2 shows interesting features as p-type semiconductor with an indirect band gap of 0.787 eV, possessing significant anisotropy properties in electrical transport, while the R-3m Li4P exhibits as a typical electride with metallic behavior at pressures of 0-82 GPa. More importantly, our calculations reveal that the theoretical capacities of Li5P2 and Li4P are predicted to reach 2164 and 3462 mAhg-1, respectively. Combining the good electrical transport properties, the calculated volume expansion of Li5P2 (130 %) is found to much smaller than that of the previous reported Li-P compounds, indicating possible high performance anode materials for LIB.