Ammonium Ion-Pre-Intercalated MnO₂ on Carbon Cloth for High-Energy Density Asymmetric Supercapacitors

With the continuous development of green energy, society is increasingly demanding advanced energy storage devices. Manganese-based asymmetric supercapacitors (ASCs) can deliver high energy density while possessing high power density. However, the structural instability hampers the wider application of manganese dioxide in ASCs. A novel MnO₂-based electrode material was designed in this study. We synthesized a MnO₂/carbon cloth electrode, CC@NMO, with NH₄⁺ ion pre-intercalation through a one-step hydrothermal method. The pre-intercalation of NH₄⁺ stabilizes the MnO₂ interlayer structure, expanding the electrode stable working potential window to 0-1.1 V and achieving a remarkable mass specific capacitance of 181.4 F g^-1. Furthermore, the ASC device fabricated using the CC@NMO electrode and activated carbon electrode exhibits excellent electrochemical properties. The CC@NMO//AC achieves a high energy density of 63.49 Wh kg^-1 and a power density of 949.8 W kg^-1. Even after cycling 10,000 times at 10 A g^-1, the device retains 81.2% of its capacitance. This work sheds new light on manganese dioxide-based asymmetric supercapacitors and represents a significant contribution for future research on them.