Performance evaluation of the electroactive material, γ-LiV2O5, made by a carbothermal reduction method

The electroactive phase, gamma-LiV2O5, has been prepared by a preparative approach based on a modified carbothermal reduction (CTR) reaction. The CTR approach uses a particulate carbon as a selective and controlled reducing agent while also allowing simultaneous lithium ion incorporation. A preparative reaction window of 550 to 700degreesC is found to be suitable for the quantitative formation of single-phase gamma-LiV2O5. At lower reaction temperatures a mixture of reaction products is formed, while at carbothermal reduction temperatures in excess of 700degreesC the formation of LiV2O4 and LiVO2 is favored. Electrochemical evaluation of the optimized gamma-LiV2O5 demonstrates that the active material is capable of a reversible specific capacity of 130 mAh/g, a performance equivalent to cycling of x=0.92 in gamma-LixV2O5. High-resolution electrochemical testing indicates that the lithium insertion process is characterized by two highly reversible reactions. The stability of these insertion reactions is established by lifetime cycling of the gamma-LiV2O5 in both metallic lithium and lithium-ion cells. Preliminary evaluation in the lithium ion configuration indicates a high first-cycle charge efficiency and long-term cycling characterized by relatively low capacity fade. The demonstrated performance compares favorably with that reported elsewhere for the alternate graphite/LiFePO4 lithium-ion system. In summary, we believe the CTR method offers an energy efficient, economical, and scalable process for producing the promising electroactive compound gamma-LiV2O5. (C) 2003 The Electrochemical Society.