High capacity vanadium oxide electrodes: effective recycling through thermal treatment

Abstract

This study demonstrates that thermal regeneration is an effective approach to convert degraded phases to functioning electroactive materials, restore functional delivered capacity and recover material crystallinity while retaining the integrity of the parent electrode. V₂O₅ nanowires were synthesized through a facile hydrothermal method and used to fabricate V₂O₅/carbon nanotube (CNT) binder free electrodes. Discharge of the V₂O₅–CNT electrodes coupled with operando energy dispersive X-ray diffraction shows no evidence of phase segregation throughout the 150 μm thick binder free electrodes indicating full utilization of a thick electrode. When V₂O₅ is highly electrochemically lithiated (x > 2 in Li_xV₂O₅), irreversible phase transformation to ω-Li_xV₂O₅ was observed, accompanied by a capacity decrease of ∼40% over 100 cycles. A simple thermal treatment of the entire electrode results in a delivered capacity equal to or higher than the original value. Both phase conversion and an increase in material crystallinity as a result of thermal treatment are observed where structural analysis indicates the formation of Li₁V₃O₈. The electrode design approach with thick electrodes and functional thermal regeneration may provide a broader choice of electroactive materials through decreasing the environmental burden by extending the lifetime of energy storage systems.