Computational discovery of cathode materials for rechargeable aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (RAZIBs) attract major interest for deployment in grid-scale energy storage due to higher safety and lower cost when compared to lithium-ion batteries. However, currently studied cathode materials suffer from capacity fade when cycling at rates appropriate for grid-scale applications ($<$ C/2). To address the present limitation on cathode material availability, more than 2000 previously synthesized oxides, chalcogenides, Prussian blue analogues, and polyanion materials were computationally screened for the discovery of highly stable RAZIB cathode materials. The structural, electrochemical, and chemical properties of the materials were respectively evaluated through an investigation of the available Zn$^{2+}$ percolation paths, the stability of the material in aqueous media under RAZIB operation conditions, and the attained transition metal oxidation state during cycling. The transition metal oxidation state and intercalating ion coordination environment were determined to govern the magnitude of the calculated Zn$^{2+}$ intercalation potential, with this finding guiding the development of batteries with high operation voltages. 12 materials previously unexplored as cathodes for RAZIBs were identified to have promising operational properties as cathodes, such as high Zn$^{2+}$ (de)intercalation potential, electrochemical stability, theoretical gravimetric capacity, and energy density. Finally, $\alpha$-FePO$_{4}$ was experimentally tested as a RAZIB cathode, with a main redox peak observed from cyclic voltammetry matching previous results for amorphous FePO$_{4}$ as a cathode for RAZIB. However, the subpar charge storage performance highlights the necessity of further experimental investigations. Overall, the materials identified in this study present a guide for the experimental development of stable next-generation cathode materials for RAZIBs.