Aluminum Chloride-Graphite Batteries with Flexible Current Collectors Prepared from Earth-Abundant Elements

In the search for low-cost and large-scale stationary storage of electricity, nonaqueous aluminum chloride-graphite batteries (AlCl₃-GBs) have received much attention due to the high natural abundances of their primary constituents, facile manufacturing, and high energy densities. Much research has focused on the judicious selection of graphite cathode materials, leading to the most notable recent advances in the performance of AlCl₃-GBs. However, the major obstacle to commercializing this technology is the lack of oxidatively stable, inexpensive current collectors that can operate in chloroaluminate ionic liquids and are composed of earth-abundant elements. This study presents the use of titanium nitride (TiN) as a compelling material for this purpose. Flexible current collectors can be fabricated by coating TiN on stainless steel or flexible polyimide substrates by low-cost, rapid, scalable methods such as magnetron sputtering. When these current collectors are used in AlCl₃-GB coin or pouch cells, stable cathodic operation is observed at voltages of up to 2.5 V versus Al³⁺/Al. Furthermore, these batteries have a high coulombic efficiency of 99.5%, power density of 4500 W kg^-1, and cyclability of at least 500 cycles.