Chloride Ions Tuning Organic Alkaline Electrolyte for Optimizing MnO2 Cathodes in Aqueous Sodium Batteries

The growing demand for efficient energy storage solutions has highlighted the potential of aqueous sodium-ion (Na+) batteries, known for their cost-effectiveness and environmental benefits. Despite their promise, challenges such as low specific capacities resulting from proton (H⁺) intercalation issues have limited their effectiveness. This study introduces a novel alkaline electrolyte environment using tetrabutylammonium hydroxide (TBAH) combined with chloride ions (Cl−) to improve the Na+ storage performance of manganese oxide (MnO2) cathodes. The optimized electrolyte achieved a remarkable reversible capacity of 101 mAh g−1 for γ-MnO2 at a current density of 0.1 A g−1, surpassing conventional aqueous solutions. The synergistic effect of TBAH and Cl− not only suppresses H+ intercalation, but also prevents the formation of manganese hydroxide passivation layers during cycling. These advancements contribute to a better understanding of electrolyte design for high-performance Na+ storage electrodes, marking a significant step forward in aqueous sodium-ion battery technology.