Elucidating the performance variations and critical issues of Zn electrodes in different types of aqueous electrolytes for Zn-based rechargeable batteries

Abstract

Zn-based batteries attract extensive attention as the next-generation energy storage devices for both electronics and large power grids due to the high capacity, energy density, low cost, and safety derived from the inherent properties of metallic Zn and the safety of aqueous electrolytes. Herein, the performance variations and critical issues of the Zn electrodes in the alkaline and neutral/slightly acid electrolytes are systematically investigated by evaluating the cycle stability, electrode reaction kinetics, and stripping/plating reversibility in three kinds of electrolytes, including ZnSO4, Zn(CF3SO3)2, and KOH+Zn(CH3COO)2. The lifespan of the Zn electrode in the neutral/slightly acid electrolytes is >1400% higher than the one in the alkaline electrolyte at a current density of 1 mA cm−2. However, the Zn electrode in the alkaline solution exhibits better reaction kinetics and low polarization. Besides, in the neutral/slightly acid electrolytes, higher coulombic efficiency is obtained, corresponding to better stripping/plating reversibility. Therefore, research in neutral/slightly acid electrolytes should focus on elevating the electrode kinetics and reducing polarization, while in alkaline electrolytes, the dendrite, hydrogen evolution, and self-discharge should be treated to elevate the calendar life and reversibility. This work provides a guideline for further construction of high-performance Zn electrodes in different electrolyte systems.