Alkali metal ion (secondary) batteries store energy reversibly by shuttling ions between anode and cathode materials capable of electrodepositing them or providing a host for their intercalation. While the performance characterization of these electrodes at the macroscale is common, very little is known about their structural and reactive heterogeneity at the micro- and nano-scale. For example, extensive discharging and repeated cycling results in increased overpotentials and decreased total charge capacity of anode electrodes, but the spatial distribution of these losses and how they relate to structural defects with unequal reactivity has remained a mystery. Understanding and visualizing these mechanisms is therefore of paramount importance to battery development.<br/> <br/>In this study, amperometric ion-sensitive platforms are developed. The sensitivities and detection limits of mercury-based microprobes for ionic lithium, sodium, and potassium were characterized under oxygen- and water-free conditions in commercially relevant solvent systems, such as propylene carbonate and ethylene carbonate. Additionally, a mercury-capped microelectrode was brought into close proximity to a carbon substrate onto which controlled defects had been previously generated. By collecting alkali ions at the probe during substrate cycling, the current response served as a direct measure of battery cyclability. Furthermore, by coupling the probe with a scanning electrochemical microscope (SECM), this study obtained quantitative maps of ion deintercalation activity, which can be correlated to defects and structures with dissimilar electron transfer kinetics. This technique provides an unprecedented view of anode degradation, accessing details that are often lost in conventional electrochemical methods.

Amperometric probes for investigating energy storage processes

249th National Meeting (2015)

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