TiO2 Nanoparticles for Li-Ion Battery Anodes: Mitigation of Growth and Irreversible Capacity Using LiOH and NaOH

TiO2 anatase and rutile nanoparticles with various sizes and morphologies have been synthesized by very facile and scalable methods, involving common acids as catalysts for room-temperature precipitations. A post-treatment including addition of LiOH or NaOH to the particles followed by heating at 180 degrees C in air or autoclave suppressed crystallite growth of both rutile and anatase. Furthermore, the treatment with LiOH or NaOH consistently increased the first-cycle Coulombic efficiency in half-cells from similar to 0.77 to similar to 0.90 on average and even to similar to 1.00 in some cells. Whether LiOH or NaOH was used, or the amount, did not appear to affect the electrochemical properties significantly. The structural properties were investigated by Rietveld refinement of powder X-ray diffractograms and related to the electrochemical performance in half-cells. The crystal structure, sizes, and morphologies of the TiO2 nanoparticles were found to depend on the synthesis conditions, e.g., hydrolysis ratio and the type and concentration of the acid catalyst. Furthermore, increasing the size of rutile crystallites from similar to 6 to 11 nm decreased the maximal capacity and rate ability of the half-cells. The anatase crystallites showed optimal electrochemical performance for crystallite sizes of similar to 5-8 nm.