Rechargeable Aluminum-OrganicBatteries with Electro-Oligomers

Abstract Rechargeable Al-organic batteries using an Al metal anode and organic cathode are promising next-generation energy storage devices with high safety, but with limitations such as large polarization, sloping charge–discharge curves with low voltages, and fast capacity decay. Here, we demonstrate high-performance Al-organic batteries based on amorphous electro-oligomers derived from a new molecule, 1,4-bis(3,7-di(9H-carbazol-9-yl)-10H-phenothiazin-10-yl)benzene (named “MILES-1”). MILES-1 underwent in situ electro-oligomerization into redox-active oligomers with distinct electronic structures on conductive carbon during battery cycling via terminal carbazole groups. In our low-cost and nonflammable ternary ionic liquid electrolyte, MILES-1 electro-oligomers, consisting of approximately seven monomers with phenothiazine motifs, enabled well-defined charge–discharge curves and an unprecedentedly high discharge voltage of up to 2.04 V. With a high N and S atoms-to-aryl ratio of 4:5 in the phenylene bis(phenothiazine) motif, the Al/MILES-1 battery delivered a high capacity of 137 mAh g–1 with a CE of 99.3% at 200 mA g–1. Al/MILES-1 batteries presented low self-discharge, excellent rate performance, and cyclability, and they can operate over a wide temperature range from −20 to 60 °C. Our large Al/MILES-1 pouch cell, with a high mass loading of 25.8 mg cm–2 delivered a reversible capacity of 0.8 Ah and an areal capacity of 2.5 mAh cm–2. The combined low cost, high safety, high mass loading, wide temperature range, improved energy density, and superior cyclability highlight the potential of Al-organic batteries as future energy-storage systems.