Dual-Cation Batteries via Synergistic Cation-Sieving Electrodes and Tailored Electrolytes

This study presents a dual-cation battery enabled by electrolyte engineering and cation-sieving electrodes. The design leverages the high capacity, low working potential, and stable cycling performance of Li⁺ intercalation in the graphite anode along with the high discharge voltage, fast kinetics, and low cost of K⁺ storage in the K₂Mn[Fe(CN)₆] cathode. The proposed hybrid electrolyte promotes Li⁺-anion aggregations and preferential decomposition, producing a Li-dominant solid electrolyte interphase that suppresses K⁺ intercalation at the anode. Simultaneously, it reduces the number of highly coordinated K⁺, lowers the desolvation barrier, and facilitates charge transfer, thus enhancing the K⁺ insertion kinetics at the cathode. As a result, the designed dual-cation cell delivers an average discharge voltage of 3.80 V, a specific energy of 336.7 Wh kg^-1 (based on total mass of graphite and K₂Mn[Fe(CN)₆]), 72.5% of capacity obtained at 20 C discharge rate, and 80% capacity retention after 1200 cycles at 3 C. This synergistic electrolyte-electrode strategy not only overcomes key challenges in hybrid-ion battery design but also establishes a mechanistic framework for designing cost-effective, high-performance dual-cation energy storage systems.