Unraveling Anisotropic Hybridizations of Solid-state Electrolyte Nano-films in Li-ion Batteries

TL;DR

This study investigates the electronic structure and anisotropic hybridizations of epitaxially grown Li2WO4 nano-films on LiCoO2, revealing orientation-dependent properties that inform their application as solid-state electrolytes in high-performance Li-ion batteries.

Contribution

It provides the first detailed analysis of anisotropic hybridizations in epitaxial LWO nano-films interfaced with LCO, combining advanced synchrotron techniques and density of states calculations.

Findings

Higher W5d(eg)-O2p hybridization in LWO/LCO(104) compared to LWO/LCO(003)

Distinct anisotropy observed between different LWO orientations

Insights into electronic structure guiding electrolyte optimization

Abstract

Li2WO4 (LWO) is recognized for its potential as a solid-state electrolyte and it has demonstrated the ability to enhance the electrochemical performance of LiCoO2 (LCO) cathodes in Li-ion batteries. However, prior investigations into LWO have predominantly involved polycrystalline structures, thereby lacking a comprehensive understanding of its behavior when interfaced with single crystal systems, particularly those intricately connected to LCO. In this study, we employ pulsed laser deposition (PLD) to epitaxially synthesize LWO nano-films on 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(104) as compared to LWO/LCO(003) 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.