Linear potential sweep and potential step experiments at Cu and Ni microelectrodes have been used to investigate the Li/Li+ couple in various diethyl ether/tetrahydrofuran mixtures containing lithium hexafluoroarsenate as the electrolyte, Lithium deposition and dissolution are clearly observed in all homogeneous solvent compositions; indeed, the cyclic voltammetric responses are all similar although the concentration of the electroactive species for lithium deposition appears to decrease with increasing diethyl ether content of the medium. On the other hand the electrochemistry of lithium tetrafluoroborate solutions is different and it is not even always possible to deposit lithium metal.
The medium 90% diethyl ether/lo% tetrahydrofuran containing 1 moldm 3 lithium hexafluoroarsenate is used to study the influence of small additions of water ( i 30 mmol drne3) on the couple and to investigate the sources of films on the lithium surface after storage on open circuit. Further evidence is presented that the primary film results from reaction between the lithium surface and the hexafluoroarsenate anion.