Electrode Design for MnO2-Based Aqueous Electrochemical Capacitors: Influence of Porosity and Mass Loading

Abstract

The purpose of this study is to highlight the influence of some fabrication parameters, such as mass loading and porosity, which are not really elucidated and standardized during the realization of electrodes for supercapacitors, especially when using metal oxides as electrode materials. Electrode calendering, as one stage during the fabrication of electrodes, was carried out step-by-step on manganese dioxide electrodes to study the decreasing porosity effect on the electrochemical performance of a MnO2 symmetric device. One other crucial parameter, the mass loading, which has to be understood and well used for realistic supercapacitors, was investigated concurrently. Gravimetric, areal and volumetric capacitances are highlighted, varying the porosity for low-, medium- and large-mass loading. Low-loading leads to the best specific capacitances but is not credible for realistic supercapacitors, except for microdevices. Down 50% porosities after calendering, capacitances are increased and become stable faster, suggesting a faster wettability of the dense electrodes by the electrolyte, especially for high-mass loading. EIS experiments performed on electrodes without and with calendering lead to a significant decrease of the device’s time response, especially at high loading. A high-mass loading device seems to work as a power battery, whereas electrode calendaring, which allows decreasing the time response, leads to an electrical behavior closer to that expected for a supercapacitor.

Macro‐ and Nano‐Porous 3D‐Hierarchical Carbon Lattices for Extraordinarily High Capacitance Supercapacitors

“…These outstanding areal capacitances are among the highest values reported so far for MnO 2 -based high-mass-loading electrodes. [8,[53][54][55][56] The reason why these high-mass-loading electrodes possess high areal capacitances with excellent rate capabilities is likely due to the 3D-ordered macropores promoting ion diffusion throughout the electrode, and the MnO 2 /carbon nanostructure making it possible to store a large number of ions. However, when too much MnO 2 is deposited on the 3D electrodes, the areal capacitance decreases because the electrical conductivity of MnO 2 is too low to be a suitable electrode material and the thick coatings cause some portion of the material to be electrically inactive, resulting in poor charge transport.…”

Engineering nanostructured Ag doped α-MnO2 electrocatalyst for highly efficient rechargeable zinc-air batteries

“…Additionally, the low-frequency region of the straight line is attributed to diffusion processes, correspond to the adsorption–desorption of oxygen, the surface diffusion of intermediate oxygen species and oxygen diffusion at the air electrode interface [ 62 ]. Indeed, the impedance profiles were fit to an equivalent circuit as presented in Figure 10 b [ 63 ] . The EIS data equivalent circuit consists of R1, R2, CPE1 and Wo1 which corresponds to bulk resistance of the cell (electrolyte and electrodes), charge-transfer resistor, constant phase element and a Warburg element, respectively.…”

Binder‐Free Electro‐Deposited MnO2 @3D Carbon Felt Network: A Positive Electrode for 2V Aqueous Supercapacitor

“…[30] This is also higher than the value of 113 F g À1 at 10 mV s À1 . [31,32] The specific capacitance versus scan rate plot of MnO 2 @CF is shown in Figure 4b; the MnO 2 @CF electrode delivered specific capacitances of 145.6, 109.3, 88.2, 73.78, 63.3, 55.36, 48.9, and 43.81 F g À1 at different scan rates 20, 30, 40, 50, 60, 70, 80, and 90 mV s À1 , respectively; the electrode also delivered 39.5 F cm À2 at 100 mV s À1 which about 17% of its initial capacitance value.…”