Boosting the Zinc-Ion Storage Capability of NH<sub>4</sub>V<sub>3</sub>O<sub>8</sub> via Cation-Defect Engineering
Hongwei Tang, Kexin Wan, Kang Zhang, Juan Xie, Mingkun Wang, Pengcheng Su, Huilong Dong, Jishi Wei, Yihui Li
Abstract
Ammonium vanadate (NVO) is regarded as one of the most promising cathodes for aqueous zinc-ion batteries (AZIBs) by virtue of its favorable theoretical capacity and comparatively stable layered structure. Nevertheless, the crowded NH 4 + cation in the interlayer would partially occupy the transfer routes of Zn 2+, and the strong electrostatic interaction contributed by the excessive NH 4 + would further lower the mobility of Zn 2+, thus resulting in the sluggish kinetics of Zn 2+ and inferior rate performances. Herein, cation-modulated engineering is proposed and achieved via a facile thermal-treatment process. By modulating the number of NH 4 + cations, the interlayer spacing of NH 4 V 3 O 8 is significantly broadened and the migration barrier of Zn 2+ is effectively reduced. As a result, the proposed NH 4 V 3 O 8 cathode with moderate NH 4 + removal exhibits the favorable capacity of 375 mAh g –1 at 2 A g –1, while ∼363 mAh g –1 could be maintained after 1000 cycles, corresponding to a superior capacity retention of ∼97%, suggesting the significantly boosted electrochemical properties contributed by the cation-modulated engineering. Moreover, the related ex-situ characterizations substantiate the Zn 2+ /H 2 O co-intercalation mechanism of the proposed NVO cathode. This work sheds light on the potential of the cation-modulation strategy on accelerating the kinetics of zinc-ions and improving the electrochemical properties of ammonium vanadate-based cathodes and further broadens the application potentials of vanadium-based cathodes in rechargeable AZIBs.