Gong Jia’ni,Bai Pengfei,Sun Jingjing,Liu Yanyan,Dong Xueying,Hu Tao,Meng Changgong,Zhang Yifu
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.
VO2 has emerged as a promising cathode material for aqueous zinc-ion batteries, attributed to its unique one-dimensional tunnel structure and reversible Zn2+ de/intercalation. However, its practical application is hindered by intrinsically poor conductivity, slow ion diffusion and structural instability during long-term cycling. In this study, we introduce a novel dual-ion synergy strategy by co-doping NH4+ and F− to systematically address these challenges. The combined effects of NH4+-induced lattice expansion and F−-mediated electronic modulation significantly enhance the electrochemical performance of VO2·xH2O (VONF-0.4). Specifically, NH4+ increases the tunnel spacing for facile Zn2+ diffusion and stabilizes the V–O framework via the “pillar” effect and hydrogen bonding, while the partial substitution of O2− with F− enhances conductivity and suppresses vanadium dissolution by forming a hydrophobic interface. The optimized VONF-0.4 cathode delivers satisfactory rate capability and a high initial specific capacity of 415.4 mAh g−1 at 1.0 A g−1, which can be maintained at 371.1 mAh g−1 after 300 cycles. Notably, it shows outstanding long-term stability and retains 99.4% of its initial capacity after 1400 cycles at 10 A g−1. This work demonstrates the feasibility of dual-ion engineering in designing advanced cathode materials for high-performance aqueous zinc-ion batteries.
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