Exploring the Energy Storage Mechanism of High Performance MnO₂ Electrochemical Capacitor Electrodes: An In Situ Atomic Force Microscopy Study in Aqueous Electrolyte

Abstract

The basic microstructure‐dependent charge storage mechanisms of nanostructured MnO2 are investigated via dynamic observation of the growth and in situ probing the mechanical properties by using in situ AFM in conjunction with in situ nanoindentation. The progressive nucleation followed by three‐dimensional growth yields pulsed current deposited porous nanostructured γ‐MnO2, which exhibits a high specific capacitance of 437 F/g and a remarkable cycling performance with >96% capacitance retention after 10 000 cycles. The proton intercalation induced expansion of MnO2 can be self‐accommodated by the localized compression and reduction of the porosity. More coincidentally, the proton intercalation induced softening is favorable for the elastic deformation of MnO2. This self‐adaptive capability of nanostructured MnO2 could generate high structural reliability during cycling. These discoveries offer important mechanistic insights for the design of advanced electrochemical capacitors.

Anode Characterization in Zinc-Manganese Dioxide AA Alkaline Batteries Using Electrochemical-Acoustic Time-of-Flight Analysis

“…According to the literature, as the cell is anode limited, the MnO 2 cathode does not undergo appreciable density or modulus shifts during discharge. 26 This is consistent with the slight shifts in the MnO 2 EDXRD peaks during discharge that we previously reported. 14 However, the cathode does experience an influx of electrolyte during discharge, as shown by Riley et al through neutron tomography, 15 particularly at lower discharge rates.…”

Birnessite based nanostructures for supercapacitors: challenges, strategies and prospects

“…[11][12][13][14][15][16][17] The theoretical capacitance of Mn-based oxides can be calculated based on the average charge transfer energy of Mn 4+ to Mn 3+ and Mn 3+ to Mn 2+ . [18][19][20] Similar to other Mn-based oxides, the theoretical capacitance of birnessite is also close to 1370 F g À1 , but it is reduced by the inherent low valence Mn in the bulk of birnessite. However, these inherent low valence Mn are always coupled with some intercalated cations (Na + , K + , Ca 2+ , etc.…”

Flexible Microsupercapacitors Using Silk and Cotton Substrates

“…Many materials used in charge storage applications undergo volume change. 62 Gold, being malleable and ductile, and silk, being soft, results in the substrate in this report being able to accommodate volume change of the active materials. Cotton threads were coated with gold by following the procedure used for SFs (SEM image shown in Figure 3a).…”