X-ray absorption spectroscopy studies of the Ni ion of Li(Ni{sub 0.8}Co{sub 0.15}Al{sub 0.05}){sub 0.8}(Ni{sub 0.5}Mn{sub 0.5}){sub 0.2}O{sub 2} with a core–shell structure and LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} as cathode materials

Core–shell materials have attracted a great deal of interest since core–shell particles have superior physical and chemical properties compared to their single-component counterparts. The cathode material Li(Ni{sub 0.8}Co{sub 0.15}Al{sub 0.05}){sub 0.8}(Ni{sub 0.5}Mn{sub 0.5}){sub 0.2}O{sub 2} (LNCANMO) with a core–shell structure was synthesized via a co-precipitation method and investigated as the cathode material for lithium ion batteries. The core–shell particle consisted of LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} (LNCAO) as the core and LiNi{sub 0.5}Mn{sub 0.5}O{sub 2} as the shell. The cycling behavior between 2.8 and 4.3 V at a current of 0.1 C-rate showed a reversible capacity of ∼195 mAh g{sup −1} with little capacity loss after 50 cycles. Extensive assessment of the electronic structures of the LNCAO and LNCANMO cathode materials was carried out using X-ray absorption spectroscopy (XAS). XAS has been used for structure refinement on the transition metal ion of the cathode. In particular, XAS studies of electrochemical reactions have been done from the viewpoint of the transition metal ion. In this study, Ni K-edge XAS spectra of the charge and discharge processes of LNCAO and LNCANMO were investigated.