Electrochemically Induced Deformation Determines the Rate of Lithium Intercalation in Bulk TiS2

High Resolution Image Download MS PowerPoint Slide Understanding the kinetic limitations of intercalation reactions is essential to create high-power intercalation host materials. In this Letter, we show the existence of both diffusion-limited and non-diffusion-limited lithiation regimes in the model material bulk TiS 2 . The regions can be clearly identified by electrochemical impedance spectroscopy. A decreasing charge-transfer resistance is observed with increasing electrode polarization in the diffusion-limited region, whereas it remains constant when the electrochemical process is non-diffusion-limited. We highlight how TiS 2 interlayer deformation is closely tied to the intercalation kinetics. While regions of TiS 2 interlayer expansion/contraction are correlated with diffusion limitations, lithiation occurring under constant interlayer spacing is non-diffusion-limited: the material exhibits pseudocapacitive behavior. Larger TiS 2 interlayer spacing results in faster ionic transport. The study sheds light on the close ties between deformation, interlayer distance, and intercalation kinetics in a model layered host material.