Affiliation:
1. School of Chemical Engineering UNSW Sydney Kensington NSW 2052 Australia
2. Department of Materials Engineering Indian Institute of Science Bengaluru 560012 India
3. School of Chemistry UNSW Sydney Kensington NSW 2052 Australia
4. School of Mechanical and Manufacturing Engineering UNSW Sydney Kensington NSW 2052 Australia
Abstract
AbstractH+ co‐intercalation chemistry of the cathode is perceived to have damaging consequences on the low‐rate and long‐term cycling of aqueous zinc batteries, which is a critical hindrance to their promise for stationary storage applications. Herein, the thermodynamically competitive H+ storage chemistry of an attractive high‐voltage cathode LiMn2O4 is revealed by employing operando and ex‐situ analytical techniques together with density functional theory‐based calculations. The H+ electrochemistry leads to the previously unforeseen voltage decay with cycling, impacting the available energy density, particularly at lower currents. Based on an in‐depth investigation of the effect of the Li+ to Zn2+ ratio in the electrolyte on the charge storage mechanism, a purely aqueous and low‐salt concentration electrolyte with a tuned Li+/Zn2+ ratio is introduced to subdue the H+‐mediated charge storage kinetically, resulting in a stable voltage output and improved cycling stability at both low and high cathode loadings. Synchrotron X‐ray diffraction analysis reveals that repeated H+ intercalation triggers an irreversible phase transformation leading to voltage decay, which is averted by shutting down H+ storage. These findings unveiling the origin and impact of the deleterious H+‐storage, coupled with the practical strategy for its inhibition, will inspire further work toward this under‐explored realm of aqueous battery chemistry.