High‐Performant All‐Organic Aqueous Sodium‐Ion Batteries Enabled by PTCDA Electrodes and a Hybrid Na/Mg Electrolyte

Abstract Aqueous sodium‐ion batteries (ASIBs) are aspiring candidates for low environmental impact energy storage, especially when using organic electrodes. In this respect, perylene‐3,4,9,10‐tetracarboxylic dianhydride (PTCDA) is a promising anode active material, but it suffers from extensive dissolution in conventional aqueous electrolytes. As a remedy, we here present a novel aqueous electrolyte, which inhibits the PTCDA dissolution and enables their use as all‐organic ASIB anodes with high capacity retention and Coulombic efficiencies. Furthermore, the electrolyte is based on two, hence “hybrid”, inexpensive and non‐fluorinated Na/Mg‐salts, it displays favourable physico‐chemical properties and an electrochemical stability window >3 V without resorting to the extreme salt concentrations of water‐in‐salt electrolytes. Altogether, this paves the way for ASIBs with both relatively high energy densities, inexpensive total cell chemistries, long‐term sustainability, and improved safety.