2D (NH ₄ ) _0.5 V ₂ O ₅ nanobelt cathode for high performance zinc ion batteries

Abstract Facile synthesis of ammonium vanadium bronze (NH 4 ) 0.5 V 2 O 5 (NVO) material with a 2D nanobelt shape via hydrothermal route, characterized by XRD, SEM, TEM, and XPS measurements. NVO material, with a layered structure and large interlayer spacing, makes zinc ion intercalation kinetics faster. Thus, NVO nanobelts showed a high specific capacity of 287 mAh g −1 in the first cycle at a C/2 rate and 210 mAh g −1 after 100 cycles, corresponding to a capacity retention of 73%. The initial Coulombic efficiency is above 98%. To further evaluate the intercalation mechanism and diffusion kinetics, ex situ XRD is measured to investigate the structural evolution of the NVO cathode during the cycling process, which indicates that the insertion of zinc ion into the electrode makes the characteristic lattice spacing (001) being more contractive. In contrast, the charging process leads to an expansion of interlayer spacing corresponding to extracted zinc ions. Accordingly, the GITT method shows an impressive average diffusion coefficient D Zn 2+ of 7.5 × 10 −10 cm 2 s −1 .