Oscillatory Current Behavior in Energy Storage Electrode Materials

Abstract

Here we report on unexpected oscillations in current observed during a step potential electrochemical spectroscopy (SPECS) study of manganese dioxide and nickel hydroxide electrodes in an alkaline electrolyte, conditions traditionally considered as a battery system, although more often now associated with electrochemical capacitors. These oscillations in current were observed at short times (<0.5 s) after each potential step in the SPECS experiment and were modelled in a similar fashion to a damped harmonic oscillator. They were associated with capacitive processes in the electrode because of their response time and were interpreted in terms of the competition between the rates of charge transfer and surface charge dissipation from the three-phase boundary between the electroactive material, the conductive additive and the electrolyte in the electrode. The presence of current oscillations in fundamentally insightful but detracts from the overall performance of these electrodes.