A porous puckered V2O5 polymorph as new high performance cathode material for aqueous rechargeable zinc batteries

Abstract

Abstract Aqueous rechargeable zinc batteries are getting increasing attention for large-scale energy storage owing to their advantages in terms of cost, environmental friendliness and safety. Here, the layered puckered γ’-V2O5 polymorph with a porous morphology is firstly introduced as cathode for an aqueous zinc battery system in a binary Zn2+/Li+ electrolyte. The Zn|| γ’-V2O5 cell delivers high capacities of 240 and 190 mAh g-1 at current densities of 29 and 147 mA g-1, respectively, and remarkable cycling stability in the 1.6 V - 0.7 V voltage window (97% retention after 100 cycles at 0.15 A g-1). The detailed structural evolution during first discharge-charge and subsequent cycling is investigated using X-ray diffraction and Raman spectroscopy. We demonstrate a reaction mechanism based on a selective Li insertion in the 1.6 V - 1 V voltage range. It involves a reversible exchange of 0.8 Li+ in γ’-V2O5 and the same structural response as the one reported in lithiated organic electrolyte. However, in the extended 1.6 V - 0.7 V voltage range, this work puts forward a concomitant and gradual phase transformation from γ’-V2O5 to zinc pyrovanadate Zn3V2O7(OH)2.2H2O (ZVO) during cycling. Such mechanism involving the in-situ formation of ZVO, known as an efficient Zn and Li intercalation material, explains the high electrochemical performance here reported for the Zn|| γ’-V2O5 cell. This work highlights the peculiar layered-puckered γ’-V2O5 polymorph outperforms the conventional α-V2O5 with a huge improvement of capacity of 240 mAh g-1 vs 80 mAh g-1 in the same electrolyte and voltage window.