Preinserted Ammonium in MnO₂ to Enhance Charge Storage in Dimethyl Sulfoxide Based Zinc-Ion Batteries

Abstract

Nonaqueous zinc-ion batteries (NZIBs) featuring manganese dioxide (MnO₂) cathodes position themselves as viable options for large-scale energy storage systems. Herein, we demonstrate the use of ammonium cation as a preintercalant to improve the performance of the δ-MnO₂ cathode in wet dimethyl sulfoxide based electrolytes. Employing in situ X-ray absorption spectroscopy, Raman spectroscopy, and synchrotron X-ray diffraction, we reveal that the integration of ammonium cations promotes the formation of NH-O-Mn networks. These networks are crucial for manipulating the distortion of the MnO₆ octahedral units during discharging, thereby mitigating charge disproportionation, which is a primary limitation to MnO₂'s charge-storage efficiency. The modified MnO₂, through this idea, displays a notable improvement in capacity (∼247 mAh/g) and can pass charge-discharge cycles up to 500 cycles with a capacity retention of 85%. These findings underscore the potential of modified MnO₂ in advancing MnO₂-based hosts for Zn-MnO₂ batteries, marking significant progress toward next-generation energy storage solutions.