Advanced characterization of high-capacity electrodes with x-ray Compton scattering

Li-rich layered oxides (LRLOs) have been very promising cathode materials due to their exceptionally high capacity of ~300 mAh/g and energy density of ~1000 mWh/g. However, the reaction mechanism underlying their electrochemical operation is not fully understood. Recent work on pristine cathode materials shows that Compton scattering spectroscopy can provide a useful tool to unravel the relationship between the key battery characteristics and the nature of the electronic orbitals involved in Li intercalation reactions [1]. Here, we discuss high-energy x-ray Compton scattering spectra along with parallel first-principles computations from Li_1.2-xTi_0.4Me_0.4O₂ (Me = Mn and Fe) for the purpose of developing advanced spectroscopic tools for characterizing LRLO battery materials. Our study gives insight into how we can obtain a faithful reconstruction of the redox orbitals using the Compton scattering technique. We also discuss the reversibility of the solid-state redox processes, and the related issues of lattice distortions, charge compensation, and the covalent mechanism of transition metal and oxide ions as a pathway to provide a new generation of insights into the mechanisms at play in LRLO battery materials.
[1] Hafiz et al. Science Advances 3 (8), e1700971 (2017).