Electrochemical quartz crystal microbalance measurement of a Li4Ti5O12 composite electrode in a carbonate electrolyte

• Electrochemical quartz crystal microbalance measurement of Li4Ti5O12 was conducted.
• The changes in the frequency were consistent with the theoretical mass changes.
• The changes in the local viscosity and density of the electrolyte were measured.
• The concentration of Li+ was discussed via the local property of the electrolyte.
• The effect of gravity convection for the concentration of Li+ was observed.

Electrochemical quartz crystal microbalance (EQCM) measurement is conducted with a Li4Ti5O12 (lithium titanium oxide, LTO)-coated quartz crystal electrode in a carbonate electrolyte (ethylene carbonate + dimethyl carbonate; 50: 50 vol%) containing 1 M LiPF6. In-situ monitoring of the mass change during the charge and discharge of the LTO electrode can be achieved quantitatively because of the “zero-strain” property of LTO with Li+ insertion and the probably low reactivity between LTO and the electrolyte. The local changes of viscosity and density of the electrolyte contacting the LTO electrode are detected via the resonance resistance of the quartz crystal electrode, suggesting the local concentrations of Li+ and counter anion changed significantly during insertion and extraction of Li+ in the organic electrolyte.