High capacity nanostructured Li2FexSiO4/C with Fe hyperstoichiometry for Li-ion batteries

Li2FeSiO4-based materials have attracted a great deal of interest as cathodes for lithium ion batteries for its excellent thermal stability and good cycling ability. Nanoporous Li2FeSiO4/C composites with varying Fe stoichiometry were synthesized by a PVA-assisted sol–gel method. Different gel formation processes were used to control morphology and pore size distribution. The pore size distribution was controlled by adjusting the parameters of the gel ageing process, the carbon content and phase purity was controlled by adjusting the starch content, and the amount of secondary phases was controlled by adjusting the Fe stoichiometry. The electrochemical properties of the Li2FeSiO4/C composite were assessed using coin cells at 24 °C, and the optimized material showed an initial discharge capacity of 163 mAh g−1 at a discharge rate of C/16 (C = 160 mA g−1) and a high capacity retention of 96% after 200 cycles at a discharge rate of 1 C.

► PVA-assisted sol–gel method was used to prepare nanoporous Li2FeSiO4/C.
► Pore size distribution was controlled by the parameters of the gel ageing process.
► Samples with large amounts of mesopores and macropores can give higher capacity.
► The amount of secondary phases was controlled by adjusting the Fe stoichiometry.
► The highest capacity resulted from gel aged at 24 °C for 10 h with Fe excess 10 mol%.