N-doped carbon fibers protection boost electrochemical performance of MnO-based cathode in rate capability and cycling-life

Abstract

MnO, as a potential cathode for aqueous zinc ion batteries (AZIBs), has received extensive attention. Nevertheless, the foggy energy storage mechanism and sluggish Zn ion kinetics pose a significant impediment for its future commercialization. Given this, we constructed N-doped carbon fiber surrounding MnO nanoparticles, which not only can provide a conductive highway for Zn ions penetration through the electrode/electrolyte interphase attributing to the electron-rich N elements that facilitates to reduce desolvation penalty, but also gives a conductive matrix for the deposition of MnOx that enhances the active site for Zn ion storage. Combining the phase diagram of the Zn-Mn-O with the experiment results, the essential energy storage behavior of the obtained cathode can be explained as follows: (1) MnO-based active material evolved into ZnMn2O4 for the repeatedly Zn2+ insertion/extraction, and (2) Zn2+ insertion/extraction into the MnOx originated from the oxidation of Mn2+ in the electrolyte. Consequently, the synergistic effect between those two parts leads to superior electrochemical performance. Thus, the results from this study provide a new angle for designing a high-performance MnO-based cathodes for AZIBs.