Rechargeable Aluminum-Organic Batteries with Electro-Oligomers

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.