An appropriate Zn2+/Mn2+ concentration of the electrolyte enables superior performance of AZIBs

Abstract

Rechargeable aqueous Zn-ion batteries (AZIBs) are promising candidates for large-scale energy storage due to their high capacity, low cost, high safety, and sustainability. However, critical issues, such as the dendrites of the anode, the Jahn–Teller distortion of the cathode material, and the formation of inert phases, limit the service lifetime and hinder their practical application. Among various strategies to address these issues, designing of the electrolyte is an effective way since the electrolyte impacts directly on the electrochemical processes of both the anode and the cathode. Herein, a superior cycle performance of 248 mA h g⁻¹ after 5000 cycles at the current density of 1 A g⁻¹ with the AZIB containing MnO as the cathode material is achieved by optimizing the electrolyte to the composition of 0.5 M ZnSO₄ + 0.5 M MnSO₄. This electrolyte provides a faster ion diffusion rate and more uniform zinc deposition on the anode, inhibits Mn (III) production in the cathode, thus reducing the Jahn–Teller distortion, suppresses the generation of inert phases in the cathode, and regulates the dissolution/re-deposition of manganese during cycling. This investigation provides new and convenient ideas in the perspective of electrolyte design for the large-scale application of AZIBs.