Synthesis and Characterization of Spherical La-Doped Nanocrystalline Li4Ti5O12/C Compound for Lithium-Ion Batteries

A spherical La3+-doped Li4Ti5O12/C composite with nanocrystalline morphology and high tap density was synthesized by an "outer gel" method and a sintering process. The crystal structure, morphology, and composition of the synthesized products were investigated by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectrometry, respectively. The investigation of Brunauer, Emmett, and Teller (BET) testing, tap density testing, ac impedance analyzing, and the determination of the electrochemical properties showed that La-doped Li4Ti5O12/C exhibited a high tap density, a large BET area, and an excellent rate capability. In contrast to Li4Ti5O12/C, the conductivity of La-doped Li4Ti5O12/C was obviously improved. It was observed that the tap density of spherical La-doped Li4Ti5O12/C powders (the mass content of C is 2.9% and the mole ratio La:Ti=0.91:100) was as high as 1.79 g cm(-3), and the BET area was 9.55 m(2) g(-1). Between 1.0 and 3.0 V vs Li, the initial discharge capacity of the La-doped Li4Ti5O12/C compound was as high as 140.3 mAh g(-1) at the 2.0C rate. After 100 cycles, the reversible capacity was still 135.8 mAh g(-1).