Facile synthesis of Li4Ti5O12/C composite with super rate performance

Abstract

The Li₄Ti₅O₁₂/C composite with lump morphology and excellent rate performance are synthesized using a facile hydrothermal method followed by a low temperature heat treatment. In the hydrothermal process, the introduction of cetyltrimethylammonium bromide (CTAB) as a surfactant significantly improves the rate performance of Li₄Ti₅O₁₂/C composite as anode material for lithium ion battery (LIB). The specific capacities of the obtained composite at charge and discharge rates of 0.1, 1, 5, 10 and 20 C are 176, 163, 156, 151 and 136 mA h g⁻¹, respectively, which is apparently larger than those of the Li₄Ti₅O₁₂/C free from CTAB in the preparation. The Li₄Ti₅O₁₂/C prepared in presence of CTAB also shows excellent cycling performance at high rate, which is attributed to its larger diffusion coefficient of lithium ion (6.82 × 10⁻¹² cm² s⁻¹) and smaller charge-transfer resistance (R_ct) (19.2 Ω) than those of the composite (1.22 × 10⁻¹³ cm² s⁻¹ and 50.2 Ω) free from CTAB in the preparation. The Li₄Ti₅O₁₂ particles obtained in presence of CTAB are coated uniformly by a thin carbon layer with a thickness of ∼1 nm, whereas the Li₄Ti₅O₁₂ particles obtained in absence of CTAB are covered by relatively thick surface layers with a thickness of ∼2.5 nm, which is too thick, blocks the lithium ion diffusion and leads to low ionic conductivity.