Preparation of Li1.03Mn1.97O4 and Li1.06Mn1.94O4 by the Polymer Precursor Method and X-ray, Neutron Diffraction and Electrochemical Studies

Abstract

The compounds, Li1.03Mn1.97O4 and Li1.06Mn1.94O4 were prepared by the polymer precursor method followed by heat treatment at 650°C for 6 hours in air. X-ray and neutron diffraction, scanning electron microscopy, and the Brunauer-Emmett-Teller surface area and density determination techniques were used to characterise the compounds. The lattice parameters obtained using neutron diffraction data of Li1.03Mn1.97O4 and Li1.06Mn1.94O4 are smaller than the parent LiMn2O4 at a = 8.20717(17) and 8.22899(13) Å, respectively. Cyclic voltammetry studies were carried out in the potential range of 3.5-4.4V at scan rate of 0.058 mV/sec. Li-doped LiMn2O4 showed the main cathodic and anodic redox peaks at ∼3.9/4.0 and ∼4.1/4.15V, respectively. The reversible charge capacities of Li1.03Mn1.97O4 with an applied current rate of 360 mA g−1 at the end of 2nd and 230 th cycle are 88 and 83 (±3) mAh g−1, respectively. At a current rate of 600 mA g−1 these charge capacities are 67 and 61 (±3) mAh g−1, respectively. Li1.06Mn1.94O4 shows a capacity of 64 and 62 (±3) mAh g−1 at the end of 2nd and 100th cycles, respectively, at a current rate of 360 mA g−1.