Self-Discharge Related to Iron Ions and its Effect on the Parameters of HES PbO[sub 2]∣H[sub 2]SO[sub 4]∣C Systems

Abstract

This work contains the results of research on the mechanism of the shuttle self-discharge detd. by Fe2+ and Fe3+ ions in the electrolyte of a heterogeneous electrochem. supercapacitor (HES) of a PbO2|H2SO4|C system, as well as the results of the measurements of the effect of the shuttle self-discharge current on the energy, capacity, and operation parameters of HES capacitors. The presence of the iron ions in the electrolyte of a HES capacitor brings about shuttle self-discharge, which continues until the voltage decreases to the value of 1.05 V. The shuttle mechanism is related to oxidn. and redn. of Fe2+ and Fe3+ ions in the pos. and neg. electrodes, resp. An anal. expression was obtained for the calcns. of the shuttle self-discharge current detd. by different types of impurity ions in the electrolyte of HES capacitors. An anal. was made with respect to the obtained exptl. and theor. data of the self-discharge current, energy, and capacity parameters, as well as their dependence on the concn. of iron ions in the electrolyte, the separator's thickness, and modes of the capacitors' charge. The processes of oxidn. and redn. of iron ions take place in the near-surface layers of the capacitor electrodes. The linear increase of the separator thickness did not bring about any linear decrease of the shuttle self-discharge current detd. by Fe2+ and Fe3+ ions. [on SciFinder (R)]