Anion Hosting Cathodes in Dual-Ion Batteries

Dual-ion batteries operate on two intercalants: anions for the cathode and cations for the anode. This battery was initially known as a dual-graphite battery, where both electrodes are graphitic carbon. The primary challenge of dual-graphite batteries is the very high operation potential of the cathode, often requiring an upper cutoff potential above 5 V vs Li+/Li. Such a potential readily oxidizes alkyl and alkylene carbonate based electrolytes. The anode side, in fact, can employ any anode of most metal-ion batteries, although, to date, the focus has still been the Li-graphite anode. Recent progress has significantly advanced the technology readiness level for this battery. Additives or ionic liquid electrolytes help mitigate cathode irreversibility; nongraphite anodes, such as aluminum, allow new carbonate electrolytes that lack the necessity of ethylene carbonate; nongraphite cathodes, including metal organic frameworks and polycyclic aromatic hydrocarbons have exhibited a remarkable potential. This Perspective highlights the challenges, summarizes the recent progress, and attempts to point out future directions in the field.