Nonplanar Tertiary-N Extended Nitrobenzene Enables Insoluble and Low-Energy-Barrier Organic Small Molecule Cathode for High-Performance Aqueous Batteries

Abstract

Organic small molecules with a high mass content ratio of redox-active sites are promising high-capacity cathode materials for aqueous zinc batteries, but their strong interaction with aqueous electrolytes causes serious dissolution and limited cycling life. Here we demonstrate nonplanar tertiary-N extended nitrobenzene, which harnesses its strong intramolecular π−π interaction beyond the H2O dissociation energy, to create an insoluble and low-energy-barrier nitroarene (TNB) small molecule cathode. Two rotating tert-N linkages bring the extended π-aromatic nonplane configuration of TNB, exhibiting a maximum negative intramolecular potential energy of −35.8 kcal mol−1 compared to its large repulsive force of 15.1 kcal mol−1 in H2O medium. Consequently, the intramolecular π-π interaction of TNB is significantly stronger than the dissociation energy of H2O, which affords structural anti-dissolution in aqueous electrolyte, extending battery lifespan to the state-of-the-art level (180,000 cycles). Meanwhile, the nonplanar structure of TNB allows for 98.9% utilization of nitro/tert-N motifs with low activation energy (0.23 eV), liberating superior capacity (430 mAh g−1) and large-current tolerance (100 A g−1). Significantly, this nonplanar molecular design shows promising preliminary generalizability to develop versatile insoluble carboxylic, cyano, and imine compounds. These proof-of-concept results suggest a potential paradigm for highly active and ultrastable organic molecules towards better aqueous batteries.