Graphene/silicon nanocomposite anode with enhanced electrochemical stability for lithium-ion battery applications

A graphene/silicon nanocomposite has been synthesized using a green approach during both synthesis and electrode processing. It has been characterized and tested as anode active material for lithium-ion batteries. The synthesis was performed by dispersing silicon nanoparticles in a carbonaceous matrix, obtained by a dual step reduction process of a previously functionalized graphene oxide substrate which avoids the formation of aggregates of Si particles and partially buffers the huge volume variations associated with Li/Si alloying processes. The graphene oxide matrix functionalization was achieved using low-molecular weight polyacrylic acid and a low-cost and eco-friendly solvent like ethylene glycol. As concerns electrode processing, composite anodes were prepared using high-molecular PolyAcrylic Acid as green binder and using ethanol as non- toxic and cheap solvent, thus avoiding the standard PVDF/NMP system which is, on the other hand, toxic and highly expensive. Furthermore, Vinylene Carbonate (VC) was used as electrolyte additive. Long cycling performance was evaluated at a current of 500 mAg-1 : after 100 cycles the anode showed a discharge capacity retention of about 80%. Analyzing the impedance spectra of the tested cells, the beneficial effect of the VC additive was showed in terms of lower SEI resistance in the long term.