Orientation-dependent electronic structure of Li2WO4 films epitaxial grown on LiCoO2 by spontaneous lithiation

Understanding and modulating the properties of materials requires a deep knowledge of their electronic structures. However, analysis of the electronic structure of a single material can be challenging, particularly for modified electrode materials, due to the complexity of mixed interface structures. In this study, we employ pulsed laser deposition (PLD) to epitaxially synthesize Li2WO4 (LWO) films on LiCoO2 (LCO) layers with different orientations. Based on a series of high-resolution synchrotron-based techniques including X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS), the electronic structure of LWO is carefully scrutinized where a higher main energy level of W5d(eg)-O2p orbitals hybridization in LWO/LCO(1 0 4) as compared to LWO/LCO(0 0 3) has been observed. This experimental finding is further validated by a comprehensive set of density of states calculations. Furthermore, detailed polarized XAS characterization unveils distinct anisotropy between the two oriented LWO configurations. This comprehensive scientific investigation, harnessing the capabilities of synchrotron-based techniques, provides invaluable insights for future studies, offering guidance for the optimized utilization of LWO as a solid-state electrolyte or modification layer for LCO cathodes in high-powered Li-ion batteries.