Application of microelectrodes to the study of the Li, Li+ couple in ether solvents. Part 1

Abstract

The electrodeposition and anodic dissolution of lithium metal in ether solvents, including tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, dioxolane and mixtures of these solvents, each containing LiAsF₆, have been studied. It is demonstrated that experiments with microelectrodes (in this work copper discs, area 5 × 10^–5 cm²) lead to high-quality data, free of effects from IR drop even in these low-dielectric-constant solvents. As a result, cyclic-voltammetric and potential-step experiments show that at a freshly deposited lithium surface the Li,Li⁺ couple is rapid and a film is formed on the surface only relatively slowly. The mechanism and kinetics of the nucleation and growth of lithium metal on a copper substrate have been probed by potential-step experiments from 0 V vs the Li,Li⁺ reference electrode to values in the range from –40 to –500 mV; well defined rising I against t transients were recorded in response to these potential steps. Double-potential-step experiments have been used to obtain further data for the deposition of lithium and also in a study of the anodic oxidation of the electrodeposited lithium metal.