Molecular Engineering Design for High-Performance Aqueous Zinc-Organic Battery

Novel small sulfur heterocyclic quinones(6a,16adihydrobenzo[b]naphtho[2′,3′:5,6][1,4]dithiino[2,3-i]thianthrene-5,7,9,14,16,18-hexaone(4S6Q) and benzo[b]naphtho[2′,3′:5,6][1,4]dithiino[2,3-i]thianthrene-5,9,14,18-tetraone(4S4Q)) are developed by molecule structural design method and as cathode for aqueous zincorganic batteries. The conjugated thioether(–S–) bonds as connected units not only improve the conductivity of compounds but also inhibit their dissolution by both extended π-conjugated plane and constructed flexible molecular skeleton. Hence, the Zn//4S6Q and Zn//4S4Q batteries exhibit satisfactory electrochemical performance based on 3.5 mol L-1(M) Zn(ClO4)2 electrolyte. For instance, the Zn//4S6Q battery obtains 240 and 208.6 mAh g-1 of discharge capacity at 150 mA g-1 and 30 A g-1, respectively. The excellent rate capability is ascribed to the fast reaction kinetics. This system displays a superlong life of 20,000 cycles with no capacity fading at 3 A g-1. Additionally, the H+-storage mechanism of the 4S6Q compound is demonstrated by ex situ analyses and density functional theory calculations. Impressively, the battery can normally work at-60 ℃ benefiting from the anti-freezing electrolyte and maintain a high discharge capacity of 201.7 mAh g-1, which is 86.2% of discharge capacity at 25 ℃. The cutting-edge electrochemical performances of these novel compounds make them alternative electrode materials for Zn-organic batteries.