pH effect upon sol–gel processing of titanium butoxide and lithium acetate precursors on the characteristics of Li₄Ti₅O₁₂ as an anode for lithium-ion batteries

Abstract

This research investigates the effect of different precursor’s pH values on the fabrication of lithium titanate (Li₄Ti₅O₁₂) via sol–gel processing and its characteristics as an anode for lithium-ion batteries. The precursor solution of lithium acetate was dropped into titanium butoxide at various initial pH values of 0.14, 0.39 and 0.69. The study of synthesis of Li₄Ti₅O₁₂ in the extreme acid environment is rarely investigated. Thermogravimetry-differential thermal analyzer was used to examine the thermal profile of the dried Li₄Ti₅O₁₂ precursor to determine the required sintering temperature, while the crystal structure and morphology of the sintered samples were characterized using an X-ray diffractometer and scanning electron microscope. The thermal analysis shows that the precursor should be sintered at 850°C to acquire pure spinel Li₄Ti₅O₁₂ crystal. An investigation of the crystal structure shows that a higher purity of Li₄Ti₅O₁₂ phase with smaller crystallite is obtainable in a more acidic condition. The resultant products contain an agglomerated and irregular morphology with non-uniform size distribution. These results show that the sample with the highest purity of Li₄Ti₅O₁₂ provides the best electrochemical performance, with a specific capacity of 100 mAh g⁻¹ at 0.1 C scanning rate and fast charging characteristics up to 10 C scanning rate.