AlCl3‐Saturated Ionic Liquid Anolyte with an Excess of AlCl3 for Al–Graphite Dual‐Ion Batteries

Abstract

AbstractAl–graphite dual‐ion batteries (AGDIBs) represent a compelling battery concept for large‐scale stationary storage of electricity in view of their safety, low cost, long cycling life, and high energy efficiency (80–90 %). However, at present, the deployment of AGDIBs is intrinsically limited by their low cell‐level energy density as a result of the non‐rocking‐chair operation principle and, consequently, the need for large quantities of acidic chloroaluminate ionic liquid (IL) anolytes as a reservoir of Al2Cl7− ions required for AGDIB operation. Thus far, AGDIBs have commonly employed IL anolytes with moderate acidity (AlCl3/Lewis base molar ratio of 1.3), which corresponds to charge‐storage anolyte capacity of ca. 19 mAh g−1, eventually resulting in low cell‐level energy densities of 20–30 Wh kg−1. In this work, we present an AGDIB utilizing an AlCl3‐saturated IL anolyte, containing an excess of AlCl3 powder for maintaining constant acidity during operation, leading to a theoretical capacity of 52 mAh g−1. The resultant AGDIB possesses an energy density of 59.1 Wh kg−1, along with a high energy efficiency of 85 % and an average discharge voltage of 1.71 V.