Unraveling the two-phase lithiation process in TiS2 by using the combination of operando EQCM and Electrochemical Dilatometry techniques

A combination of operando Electrochemical Quartz Microbalance (EQCM) and Electrochemical Dilatometer (ECD) techniques have been used to study Li-ion intercalation into TiS2. Confirmation of two distinct Li-ion intercalation regions was achieved, showing different diffusion kinetics and interlayer space parameters. Start -ing from Li0TiS2, a first lithiation zone exhibits diffusion limited (battery-like) behavior, which is associated with a significant electrode volume expansion. Conversely, once a maximum interlayer distance is attained, subse-quent lithiation results in non-diffusion limited (capacitive-like) behavior, with no further evolution of the volume of the material. EQCM motional resistance analysis shows that the TiS2 under consideration undergoes a reversible transformation, while keeping the rigid properties of the film unchanged. This study sheds light on the mass transport and deformation analysis of a model material such as TiS2. Finally, a correlation analysis between two operando techniques such as ECD and EQCM to explain charge storage mechanism is for the first time reported.