Novel LiCoO2 Cathode Material with Al2O3 Coating for a Li Ion Cell

A high-performance LiCoO2 cathode was successively fabricated by a sol−gel coating of Al2O3 to the LiCoO2 particle surfaces and subsequent heat treatment at 600 °C for 3 h. Unlike bare LiCoO2, the Al2O3-coated LiCoO2 cathode exhibits no decrease in its original specific capacity of 174 mA h/g (vs lithium metal) and excellent capacity retention (97% of its initial capacity) between 4.4 and 2.75 V after 50 cycles. A similar excellent capacity retention of the coated LiCoO2 is also observed in a Li ion cell (C/LiCoO2). This is because the high concentration of Al atoms at the particle surface region leads to the enhancement of structural stability of LiCoO2 during cycling, which originates from the disappearance of the phase transition from a hexagonal to monoclinic phase.