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