Carbon-encapsulated gigaporous microsphere as potential Si anode-active material for lithium-ion batteries

A gigaporous carbon microsphere implanted with Si particles and encapsulated by a carbon nanoshell is proposed as an active material for anodes. This material has the advantage of being processable by the economical tape-casting method for electrode fabrication. Because the implanted Si is distributed in a three-dimensional carbon skeleton of the proposed structure, the anode made of this new composite shows excellent conductivity. In addition, the pores in the structure offer the benefit of absorbing the expanded volume of the Si particles during lithiation, which helps to prevent the Si-expansion-caused physical damage of the fabricated anode. The constructed battery shows good cell performance with a highly stable capacity of ∼3300 mAh g−1 and a good retention of ∼90% under a charge/discharge current of 420 mA g−1 for 100 cycles. The good cyclability is found to be correlated with excellent structural integrity and a lower increase in the resistance of the anode after long-term cycling. Moreover, a simple increase in the thickness of the anode is effective in providing a good areal mass loading with high areal capacity of 4–7 mAh cm−2, demonstrating that the anode-active material is practical for lithium-ion batteries.