Operando SAXS and Synchroton Based X-Ray Analysis for Insights into Se Reaction Mechanisms Confined in Ordered Mesoporous Carbon for Li-Se Batteries

Increasing demand for advanced rechargeable batteries, especially in an electric vehicle market, requires further progress to increase energy density. Lithium-selenium (Li-Se) battery is one of the promising candidates for next-generation rechargeable batteries due to their high energy density and good kinetics. However, there is the primary problem to be commercialized, which is called shuttle effect. It is caused by the dissolution of polyselenide from Se cathode into the electrolyte in the repetitive charging and discharging, resulting in capacity fading.<br/>Herein, we report on ordered mesoporous carbon (OMC) to confine Se (Se/OMC) to suppress the shuttle effect by providing a sufficient capability for adsorbing dissolved polyselenide.^[1] It shows improved electrochemical performances, like higher capacity, better cycle retention, and lower resistance. <i>Operando</i> small-angle X-ray scattering (SAXS) is a powerful technique to analyze the structure dynamics of mesoporous materials in real-time conditions during electrochemical reations. ^[2,3] <i>Operando </i>SAXS, an innovative investigation on the behaviors of selenium species in the nanopores of OMC materials, combined with ex-situ analysis by synchrotron-based X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM) allows us to understand the role of mesopores and the reaction mechanisms of selenium in OMC.<br/><br/>[1] Y. Kwon, J. Yu, <i>et al</i>. manuscript in preparation.<br/>[2] G. O. Park, <i>et al</i>. <i>ACS nano</i>. <b>2015</b>, 9, 5470.<br/>[3] Y. S. Choi, <i>et al</i>. <i>Chem. Commun.</i> <b>2021</b>, 57, 10500.