Adjusting oxygen vacancy of VO2·xH2O nanoarray architectures for efficient NH4+ storage
Jia’ni Gong, Pengfei Bai, Jingjing Sun, Yanyan Liu, Xueying Dong, Tao Hu, Changgong Meng, Yifu Zhang
Abstract
Aqueous rechargeable batteries are the promising energy storge technology due to their safety, low cost, and environmental friendliness. Ammonium ion (NH 4 + ) is an ideal charge carrier for such batteries because of its small hydration radius and low molar mass. In this study, VO 2 · x H 2 O with rich oxygen defects (d-HVO) is designed and synthesized, and it exhibits unique nanoarray structure and good electrochemical performances for NH 4 + storge. Experimental and calculation results indicate that oxygen defects in d-HVO can enhance the conductivity and diffusion rate of NH 4 + , leading to improved electrochemical performances. The most significant improvement is observed in d-HVO with 2 mmol thiourea (d-HVO-2) (220 mAh·g −1 at 0.1 A·g −1 ), which has a moderate defect content. A full cell is assembled using d-HVO-2 as the anode and polyaniline (PANI) as the cathode, which shows excellent cycling stability with a capacity retention rate of 80% after 1000 cycles and outstanding power density up to 4540 W·kg −1 . Moreover, the flexible d-HVO-2∥PANI battery, based on quasi-solid electrolyte, shows excellent flexibility under different bending conditions. This study provides a new approach for designing and developing high-performance NH 4 + storage electrode materials.