Nanostructured Li4Ti5O12 synthesized in a reverse micelle: A bridge between pseudocapacitor and lithium ion battery

Nanoparticles of the Li–Ti–O precursors have been prepared using a reverse micelle method. Transmission electron microscopy (TEM) analysis showed that the precursor had an amorphous structure. The average diameter of the amorphous Li–Ti–O particles was approximately 5 nm (within a range of ±2 nm). X-ray diffraction measurement (XRD) results showed that the conversion of the amorphous precursor to crystalline spinel Li4Ti5O12 occurred upon a heat treatment at 450 °C in an atmosphere. This is much lower than that for a standard solid-state reaction of Li2CO3 and TiO2. An interesting result was that the spinel Li4Ti5O12 synthesized at 450 °C, with a particle size of 10–20 nm, had a good pseudocapacitor performance. The charge/discharge testing indicated that the specific capacity, using the activated material of the spinel Li4Ti5O12 synthesized at 450 °C, still remained 91 mAh g−1 even at a high charge/discharge rate of 40C after 100 cycles. In comparison, the Li4Ti5O12 particles synthesized at 650 °C have been grown to be the size of 50–60 nm, which mostly indicated a battery performance with a remaining specific capacity of 116 mAh g−1 at a charge/discharge rate of 40C over 100 cycles. The significance in this work disclosed that the nanostructured Li4Ti5O12 prepared as a reverse micelle could be a bridging material between pseudocapacitor and lithium ion battery.