A comparative study on A2MnPO4F (A = Na and Li) cathodes for rechargeable batteries

For safety issues, various polyanion-based materials such as LiMPO4, Li2MSiO4, LiMBO3, LiMSO4F, and Li2MPO4F (M = Fe/Mn/Co/Ni) have been extensively studied as cathodes for lithium rechargeable batteries.[1-4] Among them, the A2MPO4F (A = Na/Li) group has been at the center of interest because of the possibility of using two alkali metal ions per transition metal ion during battery operation that would ultimately deliver higher specific capacities and energy densities.[5, 6] Recently, it was reported that A2FePO4F can exhibit suitable electrochemical performance near the 3 V range.[5, 6] The two-dimensional open structure of the Pbcn space group of both Na2FePO4F and Li2FePO4F is believed to be responsible for these properties. As a similar concern, Li2CoPO4F and Li2NiPO4F have been considered a