Ionothermal synthesis of sponge-like nano Li4Ti5O12 for high rate lithium-ion batteries

The sponge-like Li4Ti5O12 (LTO) with nanostructure was synthesized by a novel ionothermal method using 1-decyl-3-methylimidazolium tetrafluoroborate ([DEMIM]BF4) as both structure-directing agent and reaction medium at ambient pressure. The samples were characterized by powder x-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, N2 adsorption measurement, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy. The results show that the sponge-like LTO material present nanostructure with even distribution of pore diameter mainly ranging from 3.7 to 5.0 nm and large specific surface area of 182 m2 g−1. The LTO electrode exhibits high specific capacity of 170.2 and 161.2 mAh g−1 at the rate of 1 and 20 concentrations (C) for the first cycle and remained 95.1 and 91.0 % after 100 cycles, the charge transfer resistance and lithium-ion diffusion coefficient are 22.70 Ω and 9.8 × 10−10 cm2 s−1, respectively. Sample carbon coating further improves electrochemical performance of LTO with reduced charge transfer resistance and enhanced cycling stability. These excellent performances can be ascribed to the sponge-like nanostructure for improving ion diffusion and electron conductivity.