Boosting the Mechanical and Electrochemical Performance of MnO2 Dry Electrode with Bentonite for Ampere-Hour Aqueous Zn-ion Batteries

Abstract

Aqueous zinc-ion batteries, distinguished by their robust safety, abundance, and cost-effectiveness, represent an ideal solution for wearable devices, backup power sources, and microgrid energy storage applications. Among various cathode materials, MnO₂ stands out as one of the most promising candidates due to its high potential relative to Zn, high theoretical specific capacity, low cost, and non-toxicity. However, the electrochemical performance of MnO₂ cathode is hindered by Mn death and pH fluctuations. Additionally, the internal inhomogeneity resulting from solvent evaporation during the slurry coating process further compromises their stability. In this study, we introduce a modification using sodium-based bentonite and successfully fabricate high-loading industrial-grade electrolytic MnO₂ cathode through a pilot-scale solvent-free dry process. The sodium-based bentonite enhances the structural stability of the electrode by forming Na−F bonds with polytetrafluoroethylene and optimizes Zn²⁺ transport through its ion-exchange properties to regulate pH. Impressively, high-loading Ben-SFC//Zn battery, with a loading exceeding 10 mg cm⁻², maintains a coulombic efficiency above 98 % and capacity of 80 % after approximately 400 cycles. Similarly, a 3Ah aqueous pouch cell demonstrates stable cycling over 400 cycles. This research not only addresses the challenges in manufacturing process of practical high-loading MnO₂ dry electrodes but also elevates the electrochemical performance of batteries.