Binding Zinc Ions by Carboxyl Groups from Adjacent Molecules toward Long-Life Aqueous Zinc-Organic Batteries

The newly emerged aqueous Zn-organic batteries are attracting extensive attention as a promising candidate for energy storage. However, most of them suffer from the unstable and/or soluble nature of organic molecules, showing limited cycle life (≤3000 cycles) that is far away from the requirement (10 000 cycles) for grid-scale energy storage. Here, a new aqueous zinc battery is proposed by using sulfur heterocyclic quinone dibenzo[b,i]thianthrene-5,7,12,14-tetraone (DTT) as the cathode. The cell shows a high reversible capacity of 210.9 mAh g_DTT ^-1 at 50 mA g_DTT ^-1 with a high mass loading of 5 mg_DTT cm^-2 , along with a fast kinetics for charge storage. Electrochemical measurements, ex situ analyses, and density functional theory calculation successfully demonstrate that the DTT electrode can simultaneously store both protons (H⁺ ) and Zn²⁺ to form DTT₂ (H⁺ )₄ (Zn²⁺ ), where Zn²⁺ is bound to the carboxyl groups from the adjacent DTT molecules with improved stability. Benefitting from the improved molecular stability and the inherent low solubility of DTT and related discharge products, the DTT//Zn full cell exhibits a superlong life of 23 000 cycles with a capacity retention of 83.8%, which is much superior to previous reports.