Local structure of LiCoO2 nanoparticles studied by Co K-edge x-ray absorption spectroscopy

The rate capability of the Li ion batteries is strongly influenced by the structural stability of the LiCoO₂ cathode. In LiCoO₂ nanoparticles, XAFS allowed to investigate the Co ion distribution inside the cathode as a function of nanoparticles size and indicates the local disorder as a limiting factor for efficiency.
L. Maugeri et al., J. Phys. Cond. Matt.  24, 335305 (2012).

LiCoO2 is a well known high efficiency cathode material for rechargeable batteries. However, the efficiency is limited by the structure of the cathode, that become instable during the Li+ diffusion. To solve this problem, the LiCoO2 nanoparticles are preferred instead of bulk cathode, in order to increase the Li ion diffusion and decrease the strain during the charge process. We have studied the local structure of the ex-situ LiCoO2 nanoparticles using the x-ray absorption spectroscopy. The Co K-edge EXAFS data provide clear evidence of local disorder in the nanoparticles, increasing with the decreasing particle size while the bond lengths are decreasing. The correlated Debye–Waller factor of the Co–O shows an increase with decreasing particle size, a mere indication of larger disorder in the nanoparticles. The XANES spectra reveal that nanoparticles are behaving like delithiated LiCoO2

. Therefore, nanoparticles of LiCoO2 seem to have atomic disorder similar to that sustained during the charging process. In conclusion, our study of the local structure of LiCoO2 nanoparticles underlines the key role of local atomic disorder and this disorder appears to be a limiting factor for the diffusion and the reversibility of the Li+ intercalation when LiCoO2 nanoparticles are used as cathodes for batteries. Retrieve article Local structure of LiCoO2 nanoparticles studied by Co K-edge x-ray absorption spectroscopy L. Maugeri, A. Iadecola, B. Joseph, L. Simonelli, L. Olivi, M. Okubo, I. Honma, H. Wadati, T. Mizokawa and N. L. Saini Journal of Physics Condensed Matter  24, 335305 (2012). 10.1088/0953-8984/24/33/335305