Aluminum-ion batteries with increased capacity

June 16, 2023

Researchers from the University of Ulm and the University of Freiburg have developed a positive electrode material for aluminium-ion batteries using an organic redox polymer based on phenothiazine. The material has demonstrated a storage capacity of 167 milliampere hours per gram (mAh/g) in experiments, surpassing the capacity of graphite, which is commonly used in batteries. Aluminium-ion batteries are considered a promising alternative to conventional batteries due to the abundance and recyclability of aluminium. This breakthrough in electrode material development brings aluminium-ion batteries closer to becoming a viable option for energy storage, offering a safer, less expensive, and more sustainable alternative to lithium-ion batteries. The research was published in the journal Energy & Environmental Science.

Electrode material inserts complex aluminium anions

The electrode material is oxidized during charging of the battery, thereby taking up complex aluminate anions. In this way, the organic redox polymer poly(3-vinyl-N-methylphenothiazine) manages to insert two [AlCl4]− anions reversibly during charging. The researchers used the ionic liquid ethylmethylimidazolium chloride as electrolyte with added aluminium chloride. “The study of aluminium batteries is an exciting field of research with great potential for future energy storage systems,” says Gauthier Studer. “Our focus lies on developing new organic redox-active materials that exhibit high performance and reversible properties. By studying the redox properties of poly(3-vinyl-N-methylphenothiazine) in chloroaluminate-based ionic liquid, we have made a significant breakthrough by demonstrating for the first time a reversible two-electron redox process for a phenothiazine-based electrode material.”