Effects of activated carbon treatment on Li4Ti5O12 anode material synthesis for lithium-ion batteries

Conventional solid-state reaction method that is widely adopted to synthesize Li4Ti5O12 (LTO) typically generates rutile TiO2 phase at calcination temperature range between 700 and 900 °C in which two competitive reactions between anatase-to-rutile TiO2 and Li2TiO3-to-Li4Ti5O12 formations occur simultaneously. This study investigates the effectiveness of coconut shell-based activated carbon treatment to eliminate the formation of anatase-to-rutile TiO2. X-ray diffraction (XRD) results indicate that mixing LTO precursors with 3, 6, and 10 wt% activated carbon prior to calcination process could reduce the amount of rutile TiO2 phase in LTO down to 6.9, 4.6, and 3.5 wt%, respectively, versus 9.1 wt% in untreated LTO. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements show that LTO pretreated with 10 wt% AC has discharge capacity of 168.35 mAh g−1 and also Li+-ion diffusion rate of 1.2 × 10−13 cm2 s−1. These values are comparably higher than those of untreated LTO that gains lower discharge capacity of 134.93 mAh g−1 and Li+-ion diffusion rate of 6.9 × 10−14 cm2 s−1. This improvement could be attributed to the suppression of anatase-to-rutile TiO2 formation during calcination process