Raman spectroscopic determination of phase evolutions in LiAlxCo1-xO2 battery materials

Superior battery materials LiAlxCo1-xO2 (x = 0.0, 0.1, 0.3, 0,5, and 0.7) w ere synthesized using a solution-based route at various sintering temperatu res (450-800 degreesC). In this communication, we report on the use of Rama n spectroscopy to study effect of composition and sintering temperature on the resulting material. The phase evolutions in LiAlxCo1-xO2 compositions w ere studied using micro-Raman spectroscopy and a phase diagram is proposed based on the observations. For less Al content, the low-temperature phases of LiAlxCo1-xO2 showed Raman spectra corresponding to a monoclinic (space g roup C2/m) structure, while a low-temperature spinel (space group Fd3m) pha se was observed for 50% or more Al in these compounds. All these compositio ns exhibited a layered hexagonal (space group R (3) over barm) structure wh en sintered above 700 degreesC. Raman spectra also revealed residual Co3O4 in the low-temperature forms of LiCoO2 and LiAl0.01Co0.9O2.