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Structural and Morphological Tuning of LiCoPO4 materials Synthesized By Solvo-Thermal Methods for Li-Cell Applications

Thursday, 2 June 2016: 16:40
Sapphire Ballroom A (Hilton San Diego Bayfront)
S. Brutti, J. Manzi (Dipartimento di Scienze, Università della Basilicata), D. Di Lecce (Sapienza University of Rome), J. Hassoun (Università di Ferrara), and S. Panero (Sapienza University of Rome)
Olivine-type lithium metal phosphates (LiMPO4) are promising cathode materials for lithium-ion batteries. LiFePO4 (LFP) is commonly used in commercial Li-ion cells but the Fe3+/Fe2+ couple can be usefully substituted with Mn3+/Mn2+, Co3+/Co2+ or Ni3+/Ni2+, in order to obtain higher redox potentials. In this communication we report a systematic analysis of the synthesis condition of LiCoPO4 (LCP) using a solvothermal route at low temperature, being the latter a valuable candidate to overcome the theoretical performances of LFP. In fact LCP shows higher working potential (4.8 V vs 3.6 V) compared to LFP and similar theoretical capacity (167 mAh g-1). Our goal is to show the effect of the synthesis condition of the ability of LCP to reversibly cycle lithium in electrochemical cells. LCP samples have been prepared through a solvo-thermal method in aqueous-non aqueous solvent blends. Different Co2+salts have been used to study the effect of the anion on the crystal growth as well as the effect of solution acidity, temperature and reaction time. Materials properties have been characterized by fast-Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopies. The correlation between structure/morphology and electrochemical performances has been investigated by galvanostatic charge-discharge cycles in lithium half cells with a EC:DMC LiPF6 electrolyte. Going beyond the stoichiometrically-pure LCP phase, we also investigated the effect of iron doping on LCP structural features and the corresponding electrochemical properties. The simultaneous effect of iron doping and post-synthesis high-temperature annealing boosts the electrochemical performances in Li cells. The optimized material has been assempled with an high capacity anode based on a Sn-C composite to demostrate the use of an LCP-based material in a complete Li-ion cell.