RIXS combined with PCA for the Study of the Li4Ti5O12 (LTO) Molecule with Different Levels of Charge

JOSE ROBLEDO; H.J. SÁNCHEZ; JUAN JOSÉ LEANI; C. PEREZ; F. OLIVA

Campinas

Congreso; Annual Users´ Meeting of the Brazilian Synchrotron Light Laboratory (LNLS-RAU) 2016; 2016

Brazilian Synchrotron Light Laboratory (LNLS)

In the last few years, the Li4Ti5O12 compound (also known as LTO) has been studied as anode material of lithium ion batteries for applications as energy storage for electric and hybrid vehicles [1-3]. This LTO compound has shown exceptional features, as an extraordinary Li-ion intercalation/de-intercalation reversibility, zero-strain volume change during the cycling process and a distinguished safety performance. Additionally, LTO has a high voltage plateau in comparison with other anode material candidates, helping to avoid the formation of metallic lithium [4]. Due to both its performance and potential applications, a better knowledge of this LTO compound is of highly interest. In order to fulfill this need, different techniques and tools have to be used.In this work, Resonant Inelastic X-ray Scattering (RIXS) has been used for studying titanium local environment changes in the LTO molecule when different levels of charge are applied. As complementary technique, XANES spectra of the Ti-K edge were also measured.The measurements were carried out at the Brazilian Synchrotron Light Source (LNLS, Campinas) in the D09B beamline in a reflection geometry and using monochromatic photons of 4900 eV, just beneath the K absorption edge of titanium. Six samples with different charges (not charged, partially charged and fully charged) were studied. XANES measurements were obtained scanning the incident beam energy in the range 4930-5080 eV.Principal Component Analysis (PCA) was used on both RIXS and XANES spectra in order to discriminate the changes on the titanium chemical state of the LTO molecule.The results showed that RIXS is a very sensitive tool, allowing the detection of slight changes in the chemical environment of the LTO compound due to different levels of charge. Moreover, chemical studies similar to the ones performed with absorption techniques (XANES, EXAFS) can be performed with this novel RIXS technique, with the clear advantages of fast acquisition and the avoidance of any energy scan during the survey, being even possible to employ an X-ray tube of proper anode material or an adequate secondary target.