We evaluate the possible formation of recently proposed PO4-deficient FePO4 by calculating its structure and stability at various charge states using the DFT+U theory.  Unpaired electrons resulting from PO4 deficiency tend to localize on undercoordinated Fe neighbors.  The absence of a PO4 unit causes local lattice distortions which are found to be sensitive to the charge state.  Our calculations show that neutral and negatively charged PO4 vacancies may coexist under intrinsic conditions.  Similar studies have also been done on PO4-deficient LiFePO4 which is reported in this work.  Both PO4-deficient FePO4 and LiFePO4 matrix turns out to be substantially softened, which may contribute to enhanced Li diffusion and provide clues towards the design of high performance cathode.

First principles prediction on the formation and properties of polyanion deficient iron phosphate

247th National Meeting (2014)

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