Electronic signatures of Lorentzian dynamics and charge fluctuations in lithiated graphite structures

Abstract

Lithium graphite intercalation compounds (Li-GICs) are essential materials for modern day portable electronics and obtaining insights into their atomic structure and thermodynamics is of fundamental interest. Here we explore the electronic and atomic states of Li-GICs at varying degrees of Lithium loading (i.e., “staging”) by means of ab-initio molecular dynamics simulations and simulated X-ray adsorption spectroscopy (XAS). We analyze the atomic correlation functions and shows that the enhancements of the Li-ion entropy with increased staging result from Lorentzian lithium-ion dynamics and charge fluctuations, which activate low-energy phonon modes. The associated electronic signatures are modulations of the unoccupied π*/σ* orbital energy levels and unambiguous fingerprints in Carbon K-edge XAS spectra. Thus, we extend the canonical view of XAS, establishing that these “static” measurements in fact encode the signature of the thermodynamic response and relaxation dynamics of the system. This causal link between atomic structure, spectroscopy, thermodynamics, and information theory can be generally exploited to better understand stability in solid-state electrochemical systems.

Hierarchical Spatial Confinement Unlocking the Storage Limit of MoS2 for Flexible High-Energy Supercapacitors

“…Lithium-ion batteries have been extensively used in flexible and portable electronic devices for decades . However, their widespread application is plagued by limitations, such as high cost, limited lithium sources, and safety concerns arising from flammable and potentially toxic organic electrolytes .…”

“…Lithium-ion batteries have been extensively used in flexible and portable electronic devices for decades. 1 However, their widespread application is plagued by limitations, such as high cost, limited lithium sources, and safety concerns arising from flammable and potentially toxic organic electrolytes. 2 Flexible solid-state supercapacitors (FSSCs) have emerged as promising candidates for next-generation energy storage devices owing to their high power density, good flexibility, high safety, and ease of handling.…”