Proton-insertion dominated polymer cathode for high-performance aqueous zinc-ion battery

Abstract

Electroactive organic materials with flexible molecular design and fast reaction kinetics are promising for aqueous zinc ion batteries (AZIBs). While it is still a challenge to solve the solubility and conductivity of organic cathode materials for AZIBs. Herein, a polymer (PTO-4NH2Ph) is developed by polymerizing pyrene-4, 5, 9, 10-tetraone (PTO) and 1, 2, 4, 5-tetraaminobenzene (4NH2Ph). The introduced π-conjugated amino groups and extended aromatic plane not only suppress the dissolution of PTO unit, but also improve the reaction activity and conductivity of whole molecule. Aromaticity and binding-H2O ability are used to evaluate the structural stability and solubility of PTO-4NH2Ph polymer by density functional theory (DFT) calculations. The Zn//PTO-4NH2Ph battery is further fabricated with 3 M ZnSO4 electrolyte and shows satisfactory cycling stability with 83 % of capacity retention over 5000 cycles. A high discharge capacity of 125.4 mAh/g is obtained even at high current density of 25 A g−1 (100 C). More importantly, the PTO-4NH2Ph electrode is demonstrated to accomplish dominated proton insertion from weakly acidic zinc electrolyte by comprehensive tests. This work paves a way for designing high-performance organic electrode materials.