(Invited) Zn Batteries: Stable Anode and High Energy Cathodes

Abstract

Our research focuses on a stable aqueous Zn-based battery with long cycling stability, decent energy density, and ultimate safety performance for large-scale energy storage. To achieve this purpose, we did systematic studies on the Zn metal anode, electrolytes, and new cathode development.For the anode side, we developed a few strategies, including pH value manipulation, ion redistribution coating, gradient coating, etc to induce stable stripping and plating of Zn. Moreover, we also found that a Zn initially plated can be much more stable than the one initially stripped during the subsequent deposition. We further utilize this observation to develop a pre-deposited Zn for Zn batteries with improved stability.For the electrolyte, we develop a reverse micelle electrolyte, with it, the Zn anode exhibits balanced merits including strong H2 coevolution suppression, prevention of dendritic and dead Zn, inhibition of corrosion, as well as relatively fast reaction kinetics. In a more extensive context, the new reverse micelle structure of electrolytes is expected to benefit other emerging battery chemistries, where a balance between fast ion transport and sufficient stabilization against side reactions is required.For the cathode with high energy density, we studied the critical research concerns and further potential developments of chalcogen/halogen-based batteries, primarily focusing on the electrochemically active chalcogen/halogen sources, reaction modes, soluble products, and electrolyte adaptability.For the cathode, we use iodine as the fixing agents working in highly concentrated electrolytes to successfully enable reversible Cl-based redox electrode. The interhalogen coordinating chemistry fixes Cl in a configuration of ICl3 -. Furthermore, we simultaneously exploit two redox centers of Cl and I to realize a novel three-electrons transfer electrode, in which the Cl-I electrode can deliver remarkably high capacity up to 612.5 mAh gI -1 and energy density as 905 Wh kgI -1. The as-obtained energy density is 387% higher compared to the traditional one-electrons transfer of ZnǁI2 battery system and superior cycling stability with capacity retention as 95.7% after 2,000 cycles.