Roadmap for the development of transition metal oxide cathodes for rechargeable zinc-ion batteries

Rechargeable zinc-ion batteries (RZIBs) are a promising multivalent battery technology for grid-scale energy storage applications, thanks to their abundant materials, lower environmental impact, and higher safety due to the use of aqueous electrolytes as compared to lithium-based batteries. However, there is still a lack of cathode materials with suitable stability and performance for reliable implementation in these energy storage applications. In this study, we have utilized readily available thermodynamic properties obtained from first-principle atomistic simulations to calculate the intercalation potential of zinc in numerous potential candidate cathode materials. We confined our chemical space to simple transition metal oxides (MxOy, where M is a transition metal). While some materials in this class were previously experimentally studied (e.g., MnO2, V2O5, MoO3), a literature survey revealed multiple oxides for which no prior investigation on their use as cathodes for RZIBs had been performed. We considered previously reported structures with similar atomic arrangements for the charged and discharged phases, the feasibility of experimental realization of the materials, the electrochemical stability of the charged cathode in an aqueous environment, and the potential degradation of aqueous electrolytes in our analysis. We mapped the zinc intercalation potential for over 50 redox pairs involving oxides of 12 different elements. These calculated theoretical potentials were then compared to previously obtained experimental results, with the relatively small difference between them (mean absolute error of 0.11 V) demonstrating the predictive capabilities of the utilized methodology. The failure mechanism for the experimentally observed capacity fade was determined from the electrochemical stability analysis to be related to the dissolution of the transition metal during battery cycling. Fully stable transition metals in the RZIBs potential and pH operating conditions were discovered and proposed for use as alloying elements in RZIBs cathodes to improve the capacity retention. Previously overlooked materials with high intercalation potential (above 1.6 V vs Zn/Zn2+) were then proposed as cathode materials for RZIBs. The Zn2+ intercalation potential mapping and electrochemical stability analysis for the oxide redox pairs achieved in this study provides a roadmap for future experimental investigations of novel cathode materials for RZIBs.