Theoretical modelling of lithium environment in composite solid electrolyte batteries investigated through x-ray absorption near edge spectroscopy*

Liquid electrolytes in conventional batteries are volatile, flammable, and cause many of the fires and explosions of lithium ion batteries. Moving to solid state electrolytes not only removes these instabilities but also suppress dendritic growth of lithium that can short a battery. Ion transport is a main limitation in these solid-electrolytes. Composite electrolytes made of nanostructured combinations of ceramics and polymers show promise to increase ion transport at the ceramic-polymer interface^[1]. To investigate the mechanisms that preferentially transport lithium ions at this interface, x-ray absoprtion near edge spectroscopy (XANES) of lithium K-edge was performed experimentally and elucidated through theoretical simulation. The solid-electrolyte system investigated is lithium perchlorate (ClO₄^-) dissolved in poly(ethylene oxide) (PEO) in nanopores of anodized aluminum oxide. Simulation results explicate a complex relationship between the XANES edge shift and lithium environment, going beyond the preliminary expectation that coordination number of lithium with oxygen causes the XANES shift.
[1] X. Zhang et al., Nano Lett., 18