Achieving High-Performance in Zinc Hybrid Capacitors with Zn(TFSI)2/PEGDME Molecular Crowding Electrolytes

Aqueous Zinc-hybrid capacitors (ZHCs) are gaining attention for their high-safety, low cost, easy maintenance, high-power, and longevity. Despite various strategies to mitigate dendrites, corrosion, and HER, practical application remains challenging. Here, we utilize an advanced polyethylene glycol dimethyl ether (PEGDME)-based molecular crowding electrolyte (MCE) to significantly enhance performance of ZHCs. Our MCE offers a wider electrochemical stability window (2.7 V), low HER activity, and superior Zn anti-corrosion properties due to reduced water activity compared to conventional electrolyte. This results in higher coulombic efficiencies (98–100 %) at various areal capacities and current densities, and longer longevity of Zn//Cu and Zn//Zn symmetric cells with MCE compared to conventional and water-in-salt electrolytes. The Zn/MCE/AC displays an enhanced voltage window (∼2 V), achieving the highest capacitance (281 F/g), competitive energy density (138 Wh/kg), low self-discharge, and excellent cyclability (19100 cycles at 1 A/g with 100 % capacity retention), indicating that MCE is a promising approach for practical energy storage applications.