title: Lithium ion quantification using mercury amalgams as in situ electrochemical probes in nonaqueous media.
abstract: We report on the quantitative, spatially resolved study of ionic processes for energy materials in nonaqueous environments by in situ electrochemical means at the micro- and nanoscale. Mercury-capped platinum ultramicroelectrodes (Hg/Pt UMEs) were tested as probes for alkali ions in propylene carbonate (PC) in an oxygen- and water-free environment. Anodic stripping voltammetry (ASV) performed at Hg/Pt UMEs displayed a linear response to Li(+) concentration extending from 20 μM to at least 5 mM. The sensitivities of these probes for ionic lithium are 1.93 and -23.2 pA μM(-1) by the steady-state amalgamation current and the peak stripping current, respectively. These values showed excellent agreement with simulated results as well as to those obtained experimentally for Cd(2+) in H2O. We further explored the interfacial imaging of lithium ion flux at an electrified interface. Scanning electrochemical microscopy (SECM) using Hg/Pt UMEs showed that the steady-state amalgamation of ionic lithium could be used to reliably position a probe close to a substrate. Investigations on a selectively insulated gold electrode in an organic solvent system showcased the response of Hg/Pt UMEs to lithium uptake by an electroactive material. Additionally, lithium stripping voltammetry at Hg deposits on a 120 nm carbon nanoelectrode demonstrated the possibility of implementing the introduced imaging strategy at the nanoscale. This work opens a way to directly correlate material defects and reactive heterogeneity in energy materials with unprecedented spatial and temporal resolution.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign , 58 Roger Adams Laboratory, 600 South Matthews Avenue, Urbana, Illinois 61801, United States.
authors.forename: Zachary J
authors.initials: ZJ
authors.lastname: Barton
authors.forename: Joaquín
authors.initials: J
authors.lastname: Rodríguez-López