Achievement of in-situ solid-to-solid conversion mechanism of thick ZnO-based anodes (30 mAh cm−2) in lean electrolyte environment for alkaline NiZn batteries

Abstract

Alkaline NiZn batteries exhibit promising prospects owing to the advantages on safety, cost, eco-compatibility and considerable energy density. Nevertheless, their commercialization is still under great restrictions owing to the poor cycling life. To overcome this challenge, it is critical to explore the charge storage behavior and the corresponding failure mechanism of full cells in practical environment with thick electrodes and lean electrolyte. Herein, an in-situ ZnO↔Zn conversion dominate mechanism is accomplished in the system assembled with ZnO@C as anode with 100 % depth of charge (DOC) and a charge capacity of ~30 mAh cm⁻², which can induce all the Zn formed in the core, resulting in dendrites and deformation-free charging. With a lower DOC of ~33 %, the cell can be well remained for ~320 cycles with a high average coulombic efficiency of ~93 % cycled at 10 mA cm⁻²/10 mAh cm⁻². Even after the cell failure, there is still no dendrites or passivation on the anode. Yet, Zn phase dominates the anode, and obvious polarization increase can be detected accompanied by the decrease of pH. Therefore, water decomposition, and mismatch of reaction kinetics of anode and cathode are proposed to be the main reason of cell failure.