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Nitridation effect on lithium iron phosphate cathode for rechargeable batteries. | LitMetric

Nitridation effect on lithium iron phosphate cathode for rechargeable batteries.

RSC Adv

Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC) Sor Juana Inés de la Cruz 3 E-28049 Madrid Spain

Published: January 2022

A novel oxynitride LiFePON with olivine structure (space group , no. 62) has been synthesized by heating a parent LiFePO precursor obtained by citrate chemistry in flowing ammonia at 650 °C. The polycrystalline sample has been characterized by X-ray and neutron powder diffraction (NPD), elemental and thermal analysis, scanning electron microscopy (SEM) and electrochemical measurements. Based on the existing contrast between the scattering lengths of the N and O species, a Rietveld refinement of the structure from NPD data revealed that N preferentially occupies the O2 positions, as likely required to fulfil the bonding power of N ions. The refined crystallographic formula implies an oxidation state of 2.2+ for Fe cations. The differential thermal analysis, in still air, shows a strong exothermic peak at 520-540 °C due to the combustion of C contents, which are embedding the olivine particles, as observed by SEM. The electrochemical measurements suggest a better performance for the nitrided sample relative to the unnitrided LiFePO material, as far as capacity and cyclability are concerned. A bond-valence energy landscape study reveals a decrease in the percolation activation energy of about 6% upon nitridation, concomitant with the better electrochemical properties of the oxynitride compound. Additionally, ceramic samples prepared under NH flow could be obtained as pure and well-crystallized olivine phases at milder temperatures (650 °C) than those usually described in literature.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8979366PMC
http://dx.doi.org/10.1039/d1ra07574hDOI Listing

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