Molecular Evolution of Target Organosulfur Enables High-Performance Aqueous Zinc Batteries

Abstract

Organic cathode materials for aqueous zinc-ion batteries (AZIBs) have garnered significant attention due to their environmental friendliness and structurally customizable nature. However, the low voltage, sluggish redox kinetics, and high solubility of most n-type cathode materials hinder their wide deployment. To overcome these challenges, through molecular evolution, we rationally select a cheap industrial material, organodisulfide 2,2′-dithiobis (benzothiazole) (MBTS), as an n-type cathode material for AZIBs. Due to the presence of N-containing benzothiazole rings, the dissociation energy of the sulfur−sulfur (S–S) bond is reduced, substantially enhancing the discharge voltage and improving the reaction kinetics. They regulate the π-conjugated plane to achieve a low solubility and fast charge transfer. Moreover, density functional theory (DFT) calculations elucidate the synergistic effect between adjacent active sites and Zn²⁺ storage reactions, revealing that the formation of weak coordination bonds between N and Zn atoms (N–Zn–S bond) reduces the solubility of the discharge product. Molecular evolution has led to the fast reaction kinetics of zinc ion storage, thus achieving a high performance under high mass loading. At a current density of 0.05 A g^–1, MBTS exhibits an average discharge voltage of 1.02 V, with a mere overpotential of 100 mV, and delivers a high specific capacity of 153.6 mAh g^–1. The assembled pouch cell demonstrates an excellent rate capability of 124.4 mAh g^–1 at 1 A g^–1 and displays a stable cycle life after 200 cycles with 96.8% capacity retention. Remarkably, MBTS maintains high specific capacity and favorable cycle stability under various ultrahigh loadings, up to 18.2 mg cm^–2. The findings provide substantial guidance for practical applications of organic electrode materials in AZIBs.