Solution Combustion Synthesis of LiFePO4/C by using Li2CO3 as precursor

CUSCUETA, D.J.; M. S. MORENO; O. CECH; M. SEDLARIKOVA; L. TRNKOVA

Buenos Aires

Congreso; 20th Topical Meeting of the International Society of Electrochemistry, Advances in Lithium and Hydrogen Electrochemical Systems for Energy Conversion and Storage; 2017

Olivine LiFePO4 (LFP) is a promising cathode candidate for high power lithium-ion batteries due to its excellent thermal stability, while Fe is inexpensive and environmentally benign [1]. The solution combustion synthesis method takes advantage of the highly exothermic nature of a reaction to complete combustion process within a short span of just 150-180 seconds with flame temperatures reaching as high as 1500ºC. It is a fast and easy to scale up [2] process that uses relatively simple equipment, allowing controlling composition, structure, homogeneity and stoichiometry of the products [3]. The use of Li2CO3 over other Li-precursors has advantages like the lower cost and the lower environment impact since its production requires less steps of industrial processing. In this work, LiFePO4/C was synthesized by the glycine-assisted combustion method and making use of Li2CO3 as Lithium precursor. It is shown that combination of Li2CO3 and the synthesis method would be commercially advantageous in mass production, despite a reduction in electrochemical discharge capacity. We also analyze the effect of post-synthesis annealing between 700 and 850 ºC for 6h under Ar atmosphere. Results of powder X-ray diffraction confirmed the formation of the olivine LiFePO4 as the main phase, while other minor impurities also appear depending on the temperature treatment. Lattice parameters show the growth of crystallite size with increasing treatment temperature, which is in accordance with results of discharge capacity, rate capability and linear sweep cyclic voltammetry of electrochemical tests. HRTEM images confirmed the one step carbon-coating of LiFePO4 particles during combustion synthesis and its morphology. Gas adsorption, laser diffraction and SEM measuring of particles were also compared to determine the chemical Li+ diffusion coefficient into LiFePO4/C.