Enhanced Reversible Zinc Ion Intercalation in Deficient Ammonium Vanadate for High-Performance Aqueous Zinc-Ion Battery

Highlights The partial removal of ammonium cations from ammonium vanadate results in an expanded interplanar space. The deficient ammonium vanadate exhibits highly reversible redox reaction. Ex situ characterizations suggest the reversible Zn 3 V 2 O 7 (OH) 2 ·2H 2 O formation/decomposition in deficient ammonium vanadate during charge/discharge processes. Ammonium vanadate with bronze structure (NH 4 V 4 O 10 ) is a promising cathode material for zinc-ion batteries due to its high specific capacity and low cost. However, the extraction of NH 4 + at a high voltage during charge/discharge processes leads to irreversible reaction and structure degradation. In this work, partial NH 4 + ions were pre-removed from NH 4 V 4 O 10 through heat treatment; NH 4 V 4 O 10 nanosheets were directly grown on carbon cloth through hydrothermal method. Deficient NH 4 V 4 O 10 (denoted as NVO), with enlarged interlayer spacing, facilitated fast zinc ions transport and high storage capacity and ensured the highly reversible electrochemical reaction and the good stability of layered structure. The NVO nanosheets delivered a high specific capacity of 457 mAh g −1 at a current density of 100 mA g −1 and a capacity retention of 81% over 1000 cycles at 2 A g −1 . The initial Coulombic efficiency of NVO could reach up to 97% compared to 85% of NH 4 V 4 O 10 and maintain almost 100% during cycling, indicating the high reaction reversibility in NVO electrode.