Effect of carbon content and annealing atmosphere on phase purity and morphology of Li2MnSiO4 synthesized by a PVA assisted sol–gel method

Abstract

Lithium transition metal orthosilicates of the general formula Li2MSiO4 have gained great interest as potential positive electrode material for Li-ion batteries. This study reports the dependence of phase purity and morphology on heat treatment atmosphere and the amount of corn-starch as carbonization agent during a PVA assisted sol–gel synthesis of nano-sized porous Li2MnSiO4/C composites. All samples were indexed to the orthorhombic Pmn21 polymorph, but samples with carbon contents less than 6% showed traces of the second orthorhombic polymorph Pmnb. Highest phase purities and a desired porous nano-sized morphology were obtained when heat treatments were carried out in 5% H2 and corn-starch amounts were ≥ 25 wt.%. Powders with varying carbon amounts were produced and the electrochemical performance was determined by galvanostatic cycling at different current densities. Samples with a corn-starch amount of 25 wt.% offered the highest initial discharge capacity of 155 mAh g−1 at a current density of 3 mA g−1.