Solvothermal Synthesis of Nasicon-Type LiTi2(PO4)3/C and Their Application As Electrode Material in Lithium-Ion Battery
Aiming to decrease the synthesis temperature and further improve the performance of LiTi2(PO4)3/C by tailoring the particle size and morphology, we intended to prepare LiTi2(PO4)3/C by solvothermal method. In our recent research, the “bare” LiTi2(PO4)3 and LiTi2(PO4)3/C were synthesized from an intermediate precursor of Li-Ti-P-O or Li-Ti-P-O-C via one-pot solvothermal method and subsequent heat treatment under 350-650 oC to obtain carbon coating. Stoichiometric amounts of LiOH·H2O, Ti(OC2H5)4, and NH4H2PO4 were used as starting materials. Cetyltrimethylammonium bromide (CTAB) and oxalic acid (OA) are simultaneously used as surfactant and carbon source for the carbon coating on the surface of LiTi2(PO4)3. Ammonia solution was used to adjust the pH value to a certain range. All the chemicals in this work are purchased from Sigma-Aldrich and used as received. The reaction took place in a reactor with the starting pressure at 7.8 bar and constant stirring for 3 days under 210 oC. Pressure and temperature changes are recorded. Additionally, LiTi2(PO4)3/C was also prepared by using a Pechini-type polymerizable complex method for comparison. Crystalline phases, structures and morphology of the materials were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM) and Raman spectroscopy. The electrochemical experiments were performed using a coin cell incorporating metallic lithium foil as a counter electrode. The working electrode was prepared from a mixture of 90 wt% LiTi2(PO4)3/C, 5 wt% carbon black as conductive additive, and 5 wt% Polyvinylidene difluoride dissolved in N-methylpyrrolidone as binder. This slurry was spread onto copper foil by tape casting and then dried at 100 oC for 12 h. Galvanostatic charge/discharge, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were conducted using a potentiostat from Biologic.
. D. P. Dubal, O. Ayyad, V. Ruiz and P. Gómez-Romero, Chem. Soc. Rev., (2015) DOI: 10.1039/C4CS00266K.
. M. Winter, R. J. Brodd, Chem. Rev., 104 (2004) 4248-4269.
. V. Aravindan, W. Chuiling and S. Madhavi, RSC Adv., 2 (2012) 7534-7539.
. Z. Li, K. C. Smith, Y. Dong, N. Baram, F. Y. Fan, J. Xie, P. Limthongkul, W. C. Carter and Y. M. Chiang, Phys. Chem. Chem. Phys., 15 (2013) 15833-15839.
. V. Aravindan, W. Chuiling, M. V. Reddy, G. V. Subba Rao, B. V. R. Chowdari and S. Madhavi, Phys. Chem. Chem. Phys., 14 (2012) 5808-5814.
. L. Liu, M. Zhou, G. Wang, H. Guo, F. Tian and X. Wang, Electrochimica Acta, 70 (2012) 136-141.
. J. Luo and Y. Xia, Adv. Funct. Mater., 17 (2007) 3877-3884.