Comparative study of Al2O3-coated LiCoO2 electrode derived from different Al precursors: uniformity, microstructure and electrochemical properties

• The Al2O3 has successfully coated on LiCoO2 by hydrolysizing two Al precursors.
• The AIP-induced Al2O3 coating exhibits an excellent electrochemical performance.
• The effect of the Al2O3 layer on cycle performance is discussed in detail.

In this work, two different Al precursors are used to modify the surface of LiCoO2 particles with Al2O3 layer, and the corresponding structural and electrochemical properties of as-prepared Al2O3-coated LiCoO2 are examined. The SEM, TEM and charge-discharge cycling results suggest that the method using aluminum isopropoxide (AIP) as Al precursor can obtain more uniform Al2O3 coating layer and more excellent electrochemical performance. The ICP results reveal that the cobalt dissolution ability is different for coated LiCoO2 prepared by two Al precursors when the charge cutoff voltage is different, and when charge cutoff voltage further increasing to 4.6 V, the dominant factor of cycling decay transform from cobalt dissolution to structural collapse caused by the excessive of Li+ delithiation. Besides, EIS analysis indicates that two kinds of Al2O3 coating layer lead to different polarization impedance, and the growth of polarization impedance during charging/discharging can be effectively suppressed by Al2O3 coating, and thus the electrochemical performance of the coated samples is greatly enhanced.