Application of electrochemical quartz crystal microbalance to lithium-ion batteries

An electrochemical quartz crystal microbalance (EQCM) was used in an investigation of the corrosion of aluminum and of the formation of the solid electrolyte interphase (SEI) on carbon in electrolytes appropriate for lithium-ion batteries. Aluminum corrosion in some electrolytes such as LiN(CF₃SO ₂)₂/propylene carbonate was examined and a corrosion mechanism was suggested.; The behavior of the carbon electrode in LiClO₄ or LiPF ₆/EC+DMC was examined by combining electrochemical methods with EQCM. A difficulty encountered in this use of the EQCM was a monotonic decrease in crystal resonant frequency with time. It was determined that this was due to a change in the viscosity of the electrolyte. Viscosities of some electrolytes that contained ethylene carbonate (EC) and dimethyl carbonate (DMC) were measured and they increased when in contact with carbon, nickel, and aluminum electrodes but did not change with time when stored in glass vials. The SO density in LiClO₄/EC+DMC was estimated to be about 1.3 g/cm3 by combining the EQCM and ellipsometry.