Speaker
Description
Lithium-ion batteries are considered as power source for electric vehicles (EV), as well as off-grid energy storage for power plant. These specific applications drive the research on high energy density, cost-effective, safe and environmental friendly battery materials. Silicon, the earth crust’s 3rd abundant material, shows very promising properties for use in battery anodes, such as the highest known Li-alloy capacity, safety, or environmental friendliness. Yet, its lithiation mechanism remains unclear. One reason is the electrode’s amorphous structure indcuced by Li insertion. Also, there are a series of side reactions which happen at the surface forming the solid electrolyte interface (SEI). We consider Atom Probe Tomography (APT) [1] as a powerful tool to understand the phase changes at anatomic level. Aided by Focus Ion Beam (FIB), we can address the element distribution in any local structure. On the other hand, Hard X-Ray Photoelectron Spectroscopy (HAXPES) is adopted for a detailed SEI study. The employed high energy X-ray beams can probe deeper information of core level photoemission. In this study, the silicon alloy Si/Ti4Ni4Si7 (STN) has been studied [2] for both, its phase change and SEI composition during lithiation.
[1] Diercks et al., Microscopy of Chemical and Mechanical Heterogeneities in Lithium Cobalt Oxide, Microscopy and Microanalysis 21 (2015), 523.
[2] Son et al. “A Highly Reversible Nano Si Anode Enabled by Mechanical Confinement in an Electrochemically Activated LiXTi4Ni4Si7 Matrix.” Advanced Energy Materials 2 (2012), 1226.
