A new class of tailor-made Fe0.92Mn0.08Si2 lithium battery anodes: Effect of composite and carbon coated Fe0.92Mn0.08Si2 anodes

As an approach to surpass the unavoidable capacity fading of native silicon anodes upon cycling, newer anodes such as FeSi2 (alloy anode), Fe0.92Mn0.08Si2 (doped alloy anode), FeSi2/graphite and Fe0.92Mn0.08Si2/graphite composite anodes were prepared via mechanical ball milling process. Subsequently, coating of disordered carbon on the parent FeSi2 and Fe0.92Mn0.08Si2 matrix was carried out through the pyrolysis of PVC. The introduction of co-milling component (8% manganese) as dopant into the parent FeSi2 structure was found to enhance only the specific capacity values of native FeSi2 anodes during the initial cycles, whereas the deployment of composite alloy anodes (FeSi2/graphite and Fe0.92Mn0.08Si2/graphite) and the carbon coated FeSi2 and Fe0.92Mn0.08Si2 anodes has exhibited good cyclic reversibility (<10%) and excellent coulombic efficiency (>95%) values upon extended cycling. From the set of alloy anodes chosen for the present study, Fe0.92Mn0.08Si2/graphite composite seems to have promising anode capability with an initial discharge capacity of 547 mAh/g followed by minimal capacity fade. It is believed that graphite plays an important role of buffering the volume expansion of alloy anodes and the carbon coating enhances the interface strength between electrode active material and current collector so as to realize improved electrochemical properties of alloy anodes upon extended cycling.