Electrochemical Impedance Spectroscopy Study into the Effect of Titanium Dioxide Added to the Alkaline Manganese Dioxide Cathode

Abstract

A combination of step potential electrochemical spectroscopy (SPECS) and electrochemical impedance spectroscopy (EIS) has been used to examine the effect of anatase titanium dioxide added to the alkaline manganese dioxide electrode. The inclusion of titanium dioxide was found to improve performance by lowering the resistance to charge transfer at the MnO2/electrolyte/graphite interface. Furthermore, a consideration of mass transport processes within the electrode indicates that titanium ions may become incorporated into the γ-MnO2 lattice upon cycling, impacting H+/e− mass transport.

The Effect of Barium Hydroxide on the Rechargeable Performance of Alkaline γ-MnO2

“…This provides a strong indication of a favorable interaction between dissolved Ba(II) ions and the porous EMD surface; a feature also noted previously upon inclusion of TiO 2 . 23,24 In terms of the dominant reduction process, occurring in the region 0 to −0.25 V, a broad peak consistent with the homogeneous reduction of γ-MnO 2 was observed. This process comprises overlapping contributions from the constituent ramsdellite and pyrolusite domains within the γ-MnO 2 structure.…”

Chemical Charging on a MnO2 Electrode of a Fuel Cell/Battery System in a Highly O2-Dissolved Electrolyte

“…This value is reasonable because the weight of the active material may include water and other impurities such as Fe, Cu, and Pb [15,16]. The dQ/dV discharge curve revealed that three main peaks were present near À0.1 V, À0.2 V, and À0.4 V. These correspond to the reactions of i) the surface of EMD, ii) the ramsdellite domain, and iii) the pyrolusite domain, respectively [16].…”

“…The structure of EMD consists of the intergrowth of two different structural domains: a complex tunnel of ramsdellite (1 Â 2) and pyrolusite (1 Â1) [15][16][17][18][19]. From the dQ/dV curve obtained during charging, three peaks were also obtained near À0.28 V, 0.02 V, and 0.4 V. These correspond to oxidation reactions at the pyrolusite and ramsdellite domains, and the oxygen evolution reaction upon the electrolysis of the electrolyte, respectively [15][16][17][18][19].…”

Electrode Additives and the Rechargeability of the Alkaline Manganese Dioxide Cathode

“…The variation in charge-transfer resistance across the potential range examined for each of the electrodes is shown in Figure 2. We have previously explored the change brought about by inclusion of titanium dioxide, with R ct decreasing and remaining relatively stable across the entire potential range, 25,26 and this is readily evident in Figure 2. The behavior of the 3% Ba(OH) 2 electrode appears to be intermediate between the EMD and 10% TiO 2 electrodes, with R ct decreased in magnitude but still showing many of the features of the EMD electrode.…”

“…A detailed explanation of this process and the resulting equivalent circuit model can be found in our previous studies. 25,26 This model accounts for the single semicircular arc, followed by a low frequency diffusional tail, observed throughout the EIS spectra recorded for each electrode. As shown inset in Figure 1, the model contains four elements which relate to the series resistance (R s ), charge-transfer resistance (R ct ), double layer charging (CPE1) and diffusive properties of the electrode (CPE2).…”