Transport properties of LiCoPO4 and Fe-substituted LiCoPO4

Abstract LiCoPO 4 is a promising cathode material to enable high energy, abuse tolerant Li-ion batteries. However, LiCoPO 4 has relatively poor electronic conductivity which may be improved by chemical substitution. In this work, the ionic and electronic conductivities of dense, polycrystalline LiCoPO 4 and Fe 2+ /Fe 3+ -substituted LiCoPO 4 (Li 1− x Co 0.9 Fe 0.1 PO 4 ) are measured and compared. Both materials are predominantly ionic conductors with relatively good bulk ionic and relatively poor electronic conductivities. Li 1− x Co 0.9 Fe 0.1 PO 4 exhibits both higher bulk ionic and electronic conductivity. The increased bulk ionic conductivity of Li 1− x Co 0.9 Fe 0.1 PO 4 is believed to originate mainly from extra Li vacancies and the increased electronic conductivity is believed to originate mainly from creating more mobile hole polarons compared to LiCoPO 4 as a result of Fe 2+ /Fe 3+ substitution.