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Possible Existence of a Monovalent Coordination for Nitrogen Atoms in LixPOyNz Solid Electrolyte: Modeling of X‑ray Photoelectron Spectroscopy and Raman Spectra

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journal contribution
posted on 15.10.2015, 00:00 by Émilie Guille, Germain Vallverdu, Yann Tison, Didier Bégué, Isabelle Baraille
LixPOyNz is an amorphous solid electrolyte widely used in microbattery devices. The present study, based on a confrontation between experiment and theory, aims at providing new knowledge regarding the ionic conductivity model of such systems in correlation with its structure. The computational strategy involved molecular dynamic simulations and first-principle calculations on molecular and periodic models. The experimental target data involve electronic and vibrational properties and were considered through the simulation of Raman and X-ray photoemission spectra in order to identify characteristic patterns of LixPOyNz. In particular, the presence of short phosphate chains is suggested by molecular dynamics calculations, and the simulation of Raman spectra clearly evidenced a new coordination for nitrogen atoms in the amorphous state, not considered until now in the experimental structural model of the electrolyte and initially hypothesized based on core level binding energy computations. Monovalent nitrogen atoms together with short phosphate chains were used to build a structural model of the electrolyte and appeared to lead to a better reproduction of the target experimental results, while it implies a necessary refinement of the diffusion schemes commonly considered for lithium ions.