Highly Reliable Electrochemical Characterization of Electrode/Electrolyte Interface in Sub-Second Time Based on Impulse Response Analysis

Electrochemical analysis on electrode/electrolyte interface (EEI) is utilized in numerous research areas, such as batteries, skin electrodes, and biochemical sensors. Contact impedance, the most intuitive indicator of the electrochemical reaction between electrode and electrolyte, was generally extracted through electrochemical impedance spectroscopy (EIS). However, the EIS is too time-consuming to be implemented at the industry level [1]. Also, the long measurement latency leads to low reliability in time-variant measurement conditions, such as a human body and a microfluidic channel. Therefore, a contact impedance extraction method with a short measurement latency is required for ultrafast electrochemical analysis of EEI.<br/>In this study, we propose a novel approach to extract contact impedance in an extremely short period (&lt;1 sec) through an impulse response analysis. Our approach only measures an instantaneous response of EEI to an impulse input, and then extracts the contact impedance by analyzing the response with a unique algorithm. The extracted contact impedance exhibits a slight deviation of 6.4% with conventional EIS despite of its significantly short measurement latency. The ultrafast measurement enables to reliably extract contact impedance even on human skin, which has inhomogeneous characteristics with time. Furthermore, we demonstrated the impulse response analysis in a dynamic measurement condition which moves at high speed (500 mm/s) on a linear rail. The deviation rate of the impulse response analysis exhibits 5 times lower than EIS, which suggests that the impulse response analysis has robust characteristics in time-variant environments. The superiority and practicality of impulse response analysis will be of great help to numerous electrode-related research areas as well as the industry site by providing a concise and quantitative analysis of EEI.<br/><br/>[1] N. Meddings, M. Heinrich, F. Overney, J-S. Lee, V. Ruize, E. Napolitano et al., " Application of electrochemical impedance spectroscopy to commercial Li-ion cells: A review," Journal of Power Sources, vol. 480, no. 228742, Dec 31 2020.