In Situ Measurements of Potential, Current and Charging Current across an EDL Capacitance Anode for an Aqueous Sodium Hybrid Battery

Abstract

This paper presents a novel method for obtaining in situ, through-thickness measurements of potential, current, charging current, and charge stored or discharged across capacitor and battery electrodes. Here we apply the method to an electrochemical double layer capacitance (EDLC) negative electrode for an aqueous sodium hybrid battery. In this approach, an electrode scaffold (ES) is used to directly measure the electric potential at discrete distances through the electrode under charging and discharging conditions. Finite difference methods are used to calculated local current and charging/discharging rates. The distributions obtained from these measurements are used to show non-uniform charging across an ultra-thick electrode intended for high area-specific energy storage in grid-scale energy storage applications. Using the ES we are able to gain insight into several complex phenomena that cannot be directly observed by other methods. For instance, we identify the portions of the electrode that are underutilized as well as the location of stray, parasitic currents.