Synthesis, structural and electrochemical properties of V₄O₉ cathode for lithium batteries

Single-phase three-dimensional vanadium oxide (V₄O₉) was synthesized by reduction of V₂O₅ using a gas stream of ammonia/argon (NH₃/Ar). The as-synthesized oxide, prepared by this simple gas reduction method was subsequently electrochemically transformed into a disordered rock salt type-"Li3.7V4O9" phase while cycling over the voltage window 3.5 to 1.8 V versus Li. The Li-deficient phase delivers an initial reversible capacity of ∼260 mAhg^-1 at an average voltage of 2.5 V vs. Li⁺/Li⁰. Further cycling to 50 cycles yields a steady 225 mAhg^-1. Ex situ X-ray diffraction studies confirmed that (de) intercalation phenomena follows a solid-solution electrochemical reaction mechanism. As demonstrated, the reversibility and capacity utilization of this V₄O₉ is found to be superior to battery grade, micron-sized V₂O₅ cathodes in lithium cells.