Scanning transmission X-ray microscopy studies of electrochemical activation and capacitive behavior of Mn₃O₄ supercapacitor electrodes

Abstract

This investigation, which is motivated by promising pseudocapacitive properties of Mn3O4 for energy storage in cathodes of supercapacitors, addresses the need to understand both the activation and the charge storage...

Influence of Capping Agents on the Synthesis of Mn3O4 Nanostructures for Supercapacitors

“…C S and C m were higher than those obtained for MnO 2 −MWCNT electrodes of the same AM. 64 A previous investigation 25 showed relatively high Mn 3 O 4 − MWCNT electrode resistance after VSRP1. The resistance decreased during continuous testing procedures from VSRP1 to VSRP5.…”

“…CV studies involved testing at sweep rates of 2, 5, 10, 20, 50, and 100 mV s −1 . This various sweep rate testing procedure (VSRP) was similar to the VSRP used in a previous investigation 25 for Mn 3 O 4 prepared without CAs. The obtained CV curves were of nearly rectangular shape without redox peaks (Figure 6A−C).…”

“…19,21,23,24 Numerous X-ray photoelectron spectroscopy (XPS) studies 19,21,23,24 demonstrated an increase of the oxidation state of Mn after long cycling. Recent scanning transmission X-ray microscopy (STXM) investigations 25 was based on in situ oxidation of Mn 3 O 4 and redox transformation of Mn 4+ /Mn 3+ in the electrode material. 25 The high capacitance values obtained in the investigation of Mn 3 O 4 electrodes indicated that this material can potentially outperform other promising cathode materials, such as MnO 2 .…”

“…Recent scanning transmission X-ray microscopy (STXM) investigations 25 was based on in situ oxidation of Mn 3 O 4 and redox transformation of Mn 4+ /Mn 3+ in the electrode material. 25 The high capacitance values obtained in the investigation of Mn 3 O 4 electrodes indicated that this material can potentially outperform other promising cathode materials, such as MnO 2 . It should be noted that KMnO 4 or NaMnO 4 precursors are usually used for the synthesis of MnO 2 particles.…”

“…The subsequent charging behavior involved the following reaction: Na δ MnO italicx · normalH 2 normalO ↔ MnO italicx · normalH 2 normalO + δ Na + + δ normale − Other investigations demonstrated Mn 3 O 4 activation at the beginning of cycling, which resulted in a significant capacitance increase. ,, A significant activation effect was reported for high-AM electrodes, − and it was related to the changes of the material morphology and oxidation state of Mn. ,,, Numerous X-ray photoelectron spectroscopy (XPS) studies ,,, demonstrated an increase of the oxidation state of Mn after long cycling. Recent scanning transmission X-ray microscopy (STXM) investigations analyzed Mn 3 O 4 activation by cycling at various potential sweep rates and at a constant sweep rate. The capacitance increase during electrode activation correlated with the STXM data, which demonstrated transformation of Mn 3 O 4 to MnO 2 .…”