Silicon-graphene composite anodes for high-energy lithium batteries

A chemical vapor deposition process is introduced to prepare silicon (Si)-graphene composite anode materials for lithium-ion batteries. Highly ordered crystalline Si particles are deposited onto graphene sheets by using a liquid chlorosilane as Si source. The Si-graphene composite exhibits high utilization of Si in charge-discharge processes. The capacity retention of 90% after 500 full cycles and an average Coulombic efficiency in excess of 99.5% are achieved in half cells. Moreover, atomic layer deposition (ALD) Al₂O₃ coating is directly applied on the Si-graphene electrode, which greatly suppresses the side reactions between the electrode and electrolyte, resulting in the enhancement in initial Coulombic efficiency and reversible capacity. Finally, a 3.6 V full cell device is demonstrated, which works very well by combining a Si-graphene anode with a Li-excess layer-structured composite Li_1.2Ni_0.2Mn_0.6O₂ cathode. This approach is very promising for realizing a high-energy lithium-ion battery.