Nonmetal Current Collectors: The Key Component for High-Energy-Density Aluminum Batteries

As one of the emerging safe energy-storage devices with high energy-to-cost ratio, nonaqueous aluminum batteries with enhanced energy density are intensively pursued by researchers. Although significant progress has been made on positive electrode materials, the effective energy density of aluminum batteries is still limited by the presence of high-density refractory metal current collectors, which are known to be electrochemically inert in highly acidic ionic-liquid electrolytes. To address such critical issues, here, a novel low-density (<2 g cm^-3 ) nonmetal current collector is presented, which uses poly(ethylene terephthalate) (PET) substrates coated with indium tin oxide (ITO), with the purpose of significantly reducing the ratio of nonactive components in the electrodes. In addition to the excellent chemical and electrochemical stability (with voltage as high as ≈2.75 V vs Al³⁺ /Al), this nonmetal current collector, also encompassing a carboxymethyl cellulose (CMC) binder, allows as-assembled pouch cells to deliver a reversible specific capacity of ≈120 mAh g^-1 at a current density of 50 mA g^-1 . In comparison with the high-density refractory metal Mo or Ta current collectors, these nonmetal current collectors offer a novel strategy for constructing high-energy-density aluminum batteries by substituting the key components, with the aim of boosting the energy density of nonaqueous aluminum batteries.