Structure and electrochemical characterization of LiNi0.5Mn1.5-xTixO4 prepared by solid-state reaction method

초록

We synthesized LiNi0.5Mn1.5-xTixO4 (x=0-1.0) by solid-state reaction method. Additional annealing process at 700ºC for 48 h induced an ordering of the Ni and Mn ions and LiNi0.5Mn1.5O4 have a P4332 symmetry. However, as the Ti content increased, LiNi0.5Mn1.5-xTixO4 had the Fd m symmetry rather than P4332 as evidenced by X-ray diffraction (XRD) and selected-area electron diffraction (SAED). Such behavior is attributed to the disordering of the octahedral site by replacing Mn with Ti. Ex-situ XRD patterns of the LiNi0.5Mn1.5-xTixO4 (x=0, 0.3, and 0.5) showed that phase transition was suppressed during delithiation with the increase in Ti content. As the amount of Ti increases, the plateau stemming from Ni2+/4+ redox appears at higher voltage region. GITT measurements on the LiNi0.5Mn1.5-xTixO4 electrodes showed that lithium diffusion coefficient increased with the increase in Ti content, x. The Li1- δNi0.5Mn1.0Ti0.5O4 electrode showed monotonous DLi value of 4 × 10-9 cm2 s-1 during cycling.