Characterization of LiNi _0.9Co _0.05[Mn _1/2 Mg _1/2] _0.05O ₂ solid solution for secondary lithium ion batteries

A CoMnMg co-substituted LiNi _0.9Co _0.05[Mn _1/2 Mg _1/2] _0.05O ₂ solid solution was synthesized and characterized by XRD, XPS, SEM and its electrochemical electrochemical performance was investigated. Potato-like (∼ 15 μm) single phase LiNi _0.9Co _0.05[Mn _1/2 Mg _1/2] _0.05O ₂ compound was obtained and its crystal structure was analyzed by Rietveld refinements. XPS results showed that Ni, Co, Mn and Mg at the surface of LiNi _0.9Co _0.05[Mn _1/2 Mg _1/2] _0.05O ₂ powder exist at + 4, + 3, + 3 and + 2 oxidation states respectively. And Ni in the bulk was also determined to occur as electrochemical-active Ni ^{3 +} ion, which is beneficial for high capacity electrode. The synthesized LiNi _0.9Co _0.05[Mn _1/2 Mg _1/2] _0.05O ₂ can deliver a high initial discharge capacity of 191.5 mAhg ^{- 1} at 0.2C rate and more than 93% of the initial specific discharge capacity was retained after 50 cycles.