Characterization of LiNi0.9Co0.05[Mn1/2 Mg1/2]0.05O2 solid solution for secondary lithium ion batteries

A CoMnMg co-substituted LiNi0.9Co0.05[Mn1/2 Mg1/2]0.05O2 solid solution was synthesized and characterized by XRD, XPS, SEM and its electrochemical electrochemical performance was investigated. Potato-like (~ 15 μm) single phase LiNi0.9Co0.05[Mn1/2 Mg1/2]0.05O2 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 LiNi0.9Co0.05[Mn1/2 Mg1/2]0.05O2 powder exist at + 4, + 3, + 3 and + 2 oxidation states respectively. And Ni in the bulk was also determined to occur as electrochemical-active Ni3 + ion, which is beneficial for high capacity electrode. The synthesized LiNi0.9Co0.05[Mn1/2 Mg1/2]0.05O2 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.

► Structure and electrochemical performance of LiNi0.9Co0.05[Mn1/2 Mg1/2]0.05O2 were investigated.
► Oxidation states of Ni, Co, Mn and Mg in LiNi0.9Co0.05[Mn1/2 Mg1/2]0.05O2 solution were determined by XPS.
► The excellent electrochemical performance of the cathode material is related to 2.5% of Mn-Mg co-doping.
► 2.5% of Mn-Mg co-doping can reduce the charge-transfer resistance rise over cycling.