Improved Electrochemical Performance of Li2MnSiO4/C Composite Synthesized by Combustion Technique

Li2MnSiO4 cathode powders were synthesized by a simple combustion technique using citric acid as a chelating agent. The as-synthesized powder was ballmilled with acetylene black (0-20 wt %) and heated at 700 degrees C in argon atmosphere to form a Li2MnSiO4/C composite. X-ray powder diffraction indicated the formation of Li2MnSiO4 possessing an orthorhombic crystal structure along with manganese oxide as a minor impurity phase. Field-emission-scanning electron microscopy showed that pristine Li2MnSiO4 consists of large agglomerates of similar to 500 to 800 nm. The addition of acetylene black resulted in a drastic change in morphology for Li2MnSiO4/C composites consisting of uniform grains of similar to 50 nm. The electrochemical discharge capacity as well as the rate capability of Li2MnSiO4 also improved dramatically with an increasing amount of conducting carbon (acetylene black) in the matrix, and a value as high as 164 mAh g(-1) was obtained at a current density of 0.01 mA/cm(2). Impedance spectroscopy showed that the addition of acetylene black decreases the charge-transfer impedance and checks the growth of cell impedance during cycling. Cyclic voltammetry showed two oxidation/reduction couples at 3.6/2.9 and 4.5/4.3 V with good reversibility.