An automated and lightweight framework for electrolyte diagnostics using quantitative microelectrode voltammetry

Abstract

Voltammetry is a ubiquitous electroanalytical method that can be used to help probe sustainable electrochemical technologies. When conducted with a microelectrode (radius ca. μm), voltammetry enables special interrogation of electrolyte solutions by minimizing distortions and facilitating near-steady-state measurements. Methodologies aimed to evaluate the behavior of redox-active species often leverage well-established, physically-grounded expressions that can be extended to examine electrolyte solutions under non-ideal conditions (e.g., signal convolution from multiple redox events) by simulating the entire voltammogram. To characterize these analyte systems, we first develop closed-form expressions—building on previous work that utilizes oblate spheroidal coordinates—and establish a framework for rapidly evaluating electrolyte composition. We subsequently apply finite difference transient voltammogram models to assess the performance of this workflow. We then validate our findings using model, deterministically-prepared nonaqueous electrolyte solutions containing N-[2-(methoxyethoxy)ethyl]phenothiazine. Overall, we show the toolkit is particularly adept at rapidly (< 1 min) estimating the degree to which an electrolyte solution is charged (its “state-of-charge”) and remains intact (its “state-of-health”). Finally, we highlight potential extensions of this method towards advancing in situ or operando diagnostic methods within operating electrochemical devices.