Synthesis of spinel lithium titanate anodes incorporated with rutile titania nanocrystallites by spray drying followed by calcination

Lithium insertion into spinel Li4Ti5O12 incorporated with rutile TiO2 was investigated in order to clarify the redox mechanism responsible for the first plateau at 1.5 V vs. Li/Li+. Spherical Li4Ti5O12 powders with an average diameter of 2–3 μm can be achieved by spray drying followed by sintering process. The Li/Ti molar ratio in the precursor is selected as the factor for preparing spinel Li4Ti5O12 powders with different concentrations of rutile TiO2. The specific capacity from the first plateau at 1.5 V contributes to the major portion in the overall capacity. The rutile TiO2 in spinel Li4Ti5O12 anodes tends to improve the specific capacity at the first plateau. This can be attributed to two possible reasons: (i) rutile TiO2 provides an additional number of sites (i.e., oxygen octahedral vacancy in rutile TiO2) for the Li insertion, and (ii) less amount of residual Li oxides results in high electronic conductivity. The Li4Ti5O12 anodes display high rate capability with low irreversible capacity, indicating good reversibility of insertion/de-insertion of Li ions. The results presented in this work show unambiguously that the presence of rutile TiO2 in spinel Li4Ti5O12 has a positive effect on the performance promotion of Li4Ti5O12 anodes.