Comparative study of LiCoO 2 surface modified with different oxides

Abstract

It has been shown that crystal and local structure of LiCoO 2 does not noticeably change after surface modification with different inert oxides (MgO, Li 2O·2B 2O 3, Al 2O 3, ZnO, ZrO 2) using wet chemical method. However, in the case of LiCoO 2/Al 2O 3, a small amount of Co 3O 4 phase was observed. Chemical delithiation study shows better structural and chemical stability of LiCoO 2/Al 2O 3 under treatment in water and acid solutions. Surface modification, despite of oxide, leads to improved cyclability in the 3–4.5 V range and to enlarged rechargeable capacity up to 175 mAh g −1. The capacity increases in the row ZnO ∼ Al 2O 3 > Li 2O·2B 2O 3 > ZrO 2 > MgO > bare LiCoO 2. On the other hand, LiCoO 2 treated with ethanol without salts also shows improved capacity retention. According to −d Q/d U = f( U) curves, phase transitions of LiCoO 2 during charge–discharge are not suppressed. It is concluded that surface modification results both in nanoparticlate shell with suitable electronic and ionic conductivity formation and in surface stabilization via inhibiting surface active centers.