Investigating the Effects of Modified Interlayer Spacing within Mixed Metal Oxide Cathode Materials for Next-Generation Aqueous Rechargeable Zinc-Ion Batteries

Aqueous rechargeable zinc-ion batteries (ZIBs) are a promising addition to the current energy storage landscape, particularly supporting the decarbonization of the power sector as a low-cost, high safety alternative to lithium-ion batteries. Unfortunately, the relative infancy of ZIBs means that there are a limited number of reported cathode materials, and a divisive understanding of the operating principles for those which have been reported including Mn- and V-oxides. The large solvation shell of the working cation (Zn2+) imparts several design requirements for cathode material development, specifically the need for sufficient void space for Zn2+ intercalation, further limiting the materials which have been reported. Looking to other well-established battery chemistries, we considered the use of layered mixed metal oxides (MMOs) with Mn due to its known electrochemical activity within the operating voltage of aqueous ZIBs. We developed several MMO cathodes with tuned interlayer distance to achieve the larger void spacing capable of accommodating Zn2+. We investigated the impact of composition on the structural and electrochemical properties of 15+ different MMO materials. We determined that interlayer spacing plays critical role in electrochemical performance and that there is an optimal composition to provide enhanced specific capacity to the battery. Considering the narrow range of reported ZIBs cathodes, in this study we proposed several new materials that expand the scope of viable cathodes for next generation ZIBs and provides direction for future researchers to accelerate new material development for this technology.