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.