Improved Electrochemical Performance of Li[sub 2]MnSiO[sub 4]/C Composite Synthesized by Combustion Technique

Abstract

Li 2 MnSiO 4 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°C in argon atmosphere to form a Li 2 MnSiO 4 /C composite. X-ray powder diffraction indicated the formation of Li 2 MnSiO 4 possessing an orthorhombic crystal structure along with manganese oxide as a minor impurity phase. Field-emission-scanning electron microscopy showed that pristine Li 2 MnSiO 4 consists of large agglomerates of ∼500 to 800 nm. The addition of acetylene black resulted in a drastic change in morphology for Li 2 MnSiO 4 /C composites consisting of uniform grains of ∼50 nm. The electrochemical discharge capacity as well as the rate capability of Li 2 MnSiO 4 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. © 2009 The Electrochemical Society.