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

Lithium-rich phosphides have recently attracted considerable attention due to their potential application as high-capacity and high-rate anodes for lithium-ion batteries (LIBs). However, there is still short of the 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 report two novel Li-P states, 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 a p-type semiconductor with an indirect band gap of 0.787 eV, possessing significant anisotropy properties in electrical transport, while R3[combining macron]m Li₄P acts 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 mA h g^-1, respectively. Combined with the good electrical transport properties, the calculated volume expansion of Li₅P₂ (130%) is found to be much smaller than those of the previously reported Li-P compounds, indicating its potential as a high performance anode material for LIBs.