New active titanium oxyphosphate material for lithium batteries

Ni0.5TiOPO4 oxyphosphate has been identified in the (NiO-TiO2-P2O5) ternary diagram as a new insertion compound for lithium batteries. The 3-dimensional structure of this material consists of corner sharing octahedra [TiO6], isolated [PO4] tetrahedra, and [NiO6] octahedra located between the titanium chains. The material also contains octahedral vacant sites that constitute favorable sites for lithium insertion. The Ni0.5TiOPO4 electrode intercalates three lithium atoms during the first discharge with an equivalent specific capacity of 415 mAh/g. The cell based on this new cathode material operates at 1.8 V vs. metallic lithium and exhibits low area specific impedance values. The large observed capacity and the fairly good cycling characteristics of the cell based on this new cathode material make this system an excellent system for applications that require low voltage and high energy density.