Transport properties of LiCoPO4 and Fe-substituted LiCoPO4

LiCoPO4 is a promising cathode material to enable high energy, abuse tolerant Li-ion batteries. However, LiCoPO4 has relatively poor electronic conductivity which may be improved by chemical substitution. In this work, the ionic and electronic conductivities of dense, polycrystalline LiCoPO4 and Fe2+/Fe3+-substituted LiCoPO4 (Li1−xCo0.9Fe0.1PO4) are measured and compared. Both materials are predominantly ionic conductors with relatively good bulk ionic and relatively poor electronic conductivities. Li1−xCo0.9Fe0.1PO4 exhibits both higher bulk ionic and electronic conductivity. The increased bulk ionic conductivity of Li1−xCo0.9Fe0.1PO4 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 LiCoPO4 as a result of Fe2+/Fe3+ substitution.