Investigating the Influence of Sodium Preintercalation on the Electrochemical Behavior of Ultrathin MnO2Nanowires for Enhanced Supercapacitor Performance

We have successfully synthesized bare and Na+preintercalated MnO2nanowires (NWs) (NaxMnO2, x= 0.05, 0.1, and 0.15) using a facile hydrothermal method. Supercapacitors are the state-of-the-art technology to overcome the global energy crisis, owing to their fast charging/discharging rates and higher power density. One-dimensional morphology (nanorods, nanowires, etc.) boosts the inherent low conductivity of transition metal oxides including MnO2by confining charge transport only in one direction. Here, we have preintercalated Na+ions into MnO2nanowires (NWs) as a conductivity booster as well as a tunnel-stabilizing agent for α-MnO2. Morphological analysis reveals that nanowires have <50 nm diameter and their surface gets cracked with Na+preintercalation, offering a less dead area. Linear sweep voltammetry (LSV) results revealed an increase in oxygen evolution overpotential by Na+preintercalation, which can enable the supercapacitor to operate at an extended potential window. Na+preintercalation and control on morphology not only increased the conductivity but also shielded the electrode pulverization against tedious charging/discharging cycles and reduced the electrolyte diffusion pathway. These features enabled Na0.10MnO2NWs to exhibit a specific capacitance of 1061 F g–1@1 A g–1and an excellent rate capability of 85.6% at 9 A g–1along with 95.9% capacitance retention after 6000 charging–discharging cycles at 12 A g–1current density. This study showed that Na+preintercalation in MnO2could improve the electrochemical performance and open up new horizons to manufacture high-performance next-generation supercapacitors.