A compact silicon–carbon composite with an embedded structure for high cycling coulombic efficiency anode materials in lithium-ion batteries

Abstract

The poor structural stability and cycling coulombic efficiency (CE) of silicon–carbon composites largely limit their commercial application. In this report, a compact silicon–carbon composite with an embedded structure (Si@C) is fabricated by a facile and scalable approach. Coal tar pitch is carbonized to obtain amorphous carbon. Nano-silicon is uniformly embedded in an amorphous carbon matrix which acts as a three-dimensional conductive network. Meanwhile, no obvious interface can be observed between amorphous carbon and nano-silicon. As the anode material, the Si@C composite displays a high specific capacity of 1314.6 mA h g⁻¹ and an average CE of 99.66% from the 10th to 100th cycle. The amorphous carbon can restrain the volume variation of nano-silicon, and the structure of the Si@C composite can remain intact during cycling. The Si@C-G composite is designed, which comprises the Si@C composite and commercial graphite anode materials, to further improve the CE and make the Si@C composite suitable for lithium-ion batteries with different energy densities. The capacity of the Si@C-G composite is controlled to 669.5 mA h g⁻¹; the composite shows an initial CE of 83.76%, a high average CE of 99.88% and a capacity retention of 80.10% over 250 cycles. Besides, the full cell of Si@C-G exhibits the excellent electrochemical performance. Therefore, this Si@C composite can be developed into anode materials with high CE for lithium-ion batteries.