Synthesis, Characterization and Evaluation of GO-LFP as Cathode Material for Li-ion Battery

MARIELA GISELA ORTIZ; M.P. QUIROGA ARGAÑARAZ; K. JORI; A RODRIGUEZ; J.M. RAMALLO LOPÉZ; F. REQUEJO; A. VISINTIN

Mar del Plata

Congreso; 34th Topical Meeting International Society of of the Electrochemistry; 2023

INTEMA- Universidad Nacional de Mar del Plata

The aim of thepresent work was to study the improvements that can be introduced in activematerials of LiFePO4 (LFP) to be used as cathodes in Li-ion batteries.Intensive attention has been focused on the LiFePO4 because of itslow cost, excellent abuse tolerance, a reversible specific capacity of 170 mAhg-1, a flat charge/discharge profile at intermediate voltage (3.45 Vvs. Li+/Li), and long cycle life [1]. However, one of thelimitations of LFP is associated with its low conductivity. To overcome thisproblem, modifications to the synthesis were proposed, such as time andtemperature reaction, additives (ascorbic acid), and the incorporation ofcarbon-based materials. The purpose of these modifications was to reduce thegrain size of the particles, as well as to provide them with greaterconductivity through a conductive carbon coating that facilitates the migrationof Li ions in the cathode charge-discharge process [2-3]. To increase theconductivity and stability of Fe2+, various graphene-oxide reductiontreatments were tested. LFP was synthesized by the solvothermal route of LiOH.H2O,FeSO4.7H2O, and H3PO4 usingethylene glycol as solvent; graphene oxide (GO) was added in differentsynthesis steps. These new materials were electrochemically evaluated.Structural and chemical characterization was performed by X-ray absorptiontechniques at Fe K-edge (XANES) and X-ray diffraction (XRD). The formationmechanism and the influence of GO on the morphology of LiFePO4micro- and nanocrystals were investigated. The results of electrochemicalperformance measurements revealed that the charge/discharge cyclingcharacteristics of the samples varied by tailoring their carbon coating.Particularly, the rhomboid-like LiFePO4 without GO particles presentedan initial discharge capacity of 141 mAh/ g at C/2 rate similar values for LFPmaterials with GO, but the cycling stability of this sample was better thanthat of LFP materials without GO. Also, the position of Fe K-absorption edgeindicates a +2 oxidation state for Fe atoms that are found mostly forming LFP(82%) with a small fraction of FeO (18%). These results coincide with XRD datathat indicate there is 86% concordance with LFP.