Operando study of Chemical and Structural Evolutions of TiS2 in Li-Ion and Na-Ion Batteries

Abstract

Since the first report of the inserting reaction of alkali metals in layered dichalcogenides in 1959, titanium disulfide (TiS2) has been widely studied as a model material of intercalation host compound in energy storage for Li-ion batteries. Due to its high electric conductivity, fast rate capability, good cycling performance and natural abundance, TiS2 electrode also became a promising candidate for the low-cost Na-ion battery system. However, the differences regarding the detailed chemical and structural evolutions and reaction mechanism of TiS2 in Li-ion and Na-ion batteries are not yet well understood. In this work, the chemical and structural evolutions of TiS2 in both Li-ion and Na-ion batteries are investigated via operando synchrotron absorption spectroscopy (XAS) at both the sulfur and titanium K-edges using complementary hard x-rays and tender x-rays at the National Synchrotron Light Source II. By combining X-ray diffraction and operando XAS with the Multivariate Curve Resolution - Alternating Least Squares (MCR-ALS) method, we reveal the chemical speciation during the electrochemical cycling. Our study also sheds light on the reaction mechanism of Na-TiS2, which is compared with that of the Li-TiS2 system. ACKNOWLEDGMENT We thank DOE Office of Energy Efficiency and Renewable Energy under the Advanced Battery Materials Research (BMR) program, Contract No. DE-SC0012704; we thank ISS, TES, and XPD beamlines of NSLS-II, supported by DOE Office of Science. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704. Funding was supported by Stony Brook University and Brookhaven National Laboratory. Figure: An illustration of the structural and chemical evolutions during sodiaiton observed by operando XAS and ex situ XPD approaches. Figure 1