The electrodepositiori and dissolution of lithium were investigated in an equimolar mixture of glyme and lithium bis(trifluoromethylsulfonyl)amide. An impedance technique electrochemical quartz crystal microbalance (EQCM-A) was used to monitor the product of the viscosity (eta L) and density (rho L) of the electrolyte, eta L rho L, near the electrode in addition to the mass change. The value of eta L rho L decreased during Li deposition and sharply increased during Li dissolution because of the changes in the concentration and the dissolved state of Li ion around the electrode. The sharp increase in viscosity during Li dissolution may affect the diffusion of Li(I) near the electrode/electrolyte interface, which is a key issue for the Li secondary battery. (C) 2013 The Electrochemical Society. All rights reserved.