Ultra-long cycle H-doped VO2(B) cathode for high capacity aqueous Zn-ion battery

VO2 as a potential type of cathode material for aqueous Zn-ion batteries (AZIBs) has attracted increasing interest over the past few years, owing to the various oxidation states of vanadium and unique tunnel transport pathway. However, the major challenge for VO2 is the absence of a high-capacity and stable structure because of the slow electron transport kinetics and the collapsible crystal structure. Herein, an ultra-long life H-doped VO2 is obtained by an efficient chelation reaction with ascorbic acid (AA). Benefiting from the H-doped, the crystallinity of VO2 is reduced, and the oxygen vacancies and electron conductivity in VO2 are enhanced, which is also confirmed by the calculated results of Density Functional Theory (DFT). Based on the H-doped VO2 (AA-VO2), ultra-long 22,000 cycles at 10 A g−1 are obtained as well as high specific capacity (572 mAh g−1) and energy density (443 Wh kg−1) at 0.2 A g−1. By contrast, the AZIBs with untreated VO2 exhibit only 251 mAh g−1 specific capacity and 235 Wh kg−1 energy density. And the batteries can work no more than 2000 cycles. Therefore, this H-doped VO2 by chelation with AA is a promising cathode material for high performance aqueous zinc-ion batteries.