Layered LiNi0.8Co0.1Mn0.1O2 Prepared through Calcination in Air with Preoxidized Precursor

Abstract

The layered Ni-rich oxide LiNi0.8Co0.1Mn0.1O2 is very attractive as a cathode material owing to its large reversible capacity. However, the inherent poor cycling stability of Ni-rich cathode materials has always been a serious issue limiting their commercialization. Moreover, LiNi0.8Co0.1Mn0.1O2 should be calcined under oxygen flow to promote the oxidation of Ni2+ to Ni3+, which makes it costly. In this study, we introduce a technique for preoxidation of the LiNi0.8Co0.1Mn0.1O2 precursor by KMnO4 to partially oxidize Ni2+ in the precursor (KMnO4-treatment) and eliminate the need for calcination in pure oxygen atmosphere. X-ray photoelectron spectroscopy analysis of the KMnO4-treated precursor and LiNi0.8Co0.1Mn0.1O2 obtained from the KMnO4-treated precursor in air (KMnO4-LiNi0.8Co0.1Mn0.1O2) indicates that the valence states of nickel ions are higher than those in the untreated (pristine) precursor and LiNi0.8Co0.1Mn0.1O2 obtained from the pristine precursor in air (Air-LiNi0.8Co0.1Mn0.1O2). The structure of the KMnO4-LiNi0.8Co0.1Mn0.1O2 shows no distinct differences except for a slight expansion along the c-axis and lower cation disorder. Electrochemical measurements demonstrate that KMnO4-LiNi0.8Co0.1Mn0.1O2 has better rate capability and cycling stability at cutoff voltages of 4.3 and 4.5 V than Air-LiNi0.8Co0.1Mn0.1O2. The improved cycling performance of KMnO4-LiNi0.8Co0.1Mn0.1O2 can be attributed to the favorable structural change due to the more oxidized trivalent nickel ion.