A porous puckered V_(2)O_(5) polymorph as new high performance cathode material for aqueous rechargeable zinc batteries

摘要

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 puckeredγ’-V_(2)O_(5) polymorph with a porous morphology is firstly introduced as cathode for an aqueous zinc battery system in a binary Zn^(2+)/Li^(+)electrolyte.The Zn‖γ’-V_(2)O_(5) cell delivers high capacities of 240 and190 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 the1.6 V-1.0 V voltage range.It involves a reversible exchange of 0.8 Li^(+)in γ’-V_(2)O_(5) 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’-V_(2)O_(5) to zinc pyrovanadate Zn_(3)V_(2)O_(7)(OH)2.2 H_(2)O(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’-V_(2)O_(5) cell.This work highlights the peculiar layered-puckeredγ’-V_(2)O_(5) polymorph outperforms the conventionalα-V_(2)O_(5) with a huge improvement of capacity of 240 mAh g^(-1)vs 80 mAh g^(-1) in the same electrolyte and voltage window.