Oxygen defect engineering triggered by S-doping boosts the performance of H2V3O8 nanobelts for aqueous Zn-ion storage

The exploration of cathode materials with high capacity is of great importance to the fast development of zinc-ion batteries (ZIBs). Yet the traditional cathode materials suffer from sluggish kinetics of Zn2+ diffusion. Herein, sulfur-doped and oxygen-deficient rich H2V3O8 (S-H2V3O8) cathode in-situ in carbon cloth with nanobelt structure is prepared via efficient defect engineering using sulfurization reaction, thus leading to improved Zn2+ transport kinetics and enhanced electrochemical performance. The obtained ZIBs exhibit a high reversible capacity of 496.5 mAh/g at 0.3 A/g and 287.4 mAh/g at 10 A/g, a significant energy density of 487 Wh kg−1, and a good stability performance, outperforming pristine H2V3O8 and many previous cathodes of ZIBs. The ex-situ morphology and crystalline characterizations reveal the insertion and extraction of Zn2+ during the charging/discharging process. DFT calculation certifies oxygen atoms in H2V3O8 replaced by some sulfur atoms to produce rich oxygen defects, which provide enhanced conductivity and Zn2+ adsorption free energy to store energy. Furthermore, the flexible soft-packaged batteries demonstrate outstanding electrochemical behaviors even under different bending angles and compressive conditions. This work offers a new insight into the anionic doping to construct oxygen defects in metal oxides, which provides an opportunity for designing high-performance and flexible energy storage applications.