Silicon/carbon nanotubes anode for lithium-ion batteries: Synthesis, interface and electrochemical performance

Silicon/carbon composite has been a promising anode material for lithium-ion batteries (LIBs). Carbon nanotubes (CNTs) possess high electrical conductivity, specific area, and mechanical strength, holding great potential for constructing advanced Si/C anode materials. However, the unstable interface and tricky synthesis processes hinder practical applications of Si/CNTs anode. In this work, we develop a one-step method to prepare Si/CNTs composite by magnesium reduction of SiO₂ mixed with CNTs. The interface between Si nanoparticles and CNTs upon the weight ratio of SiO₂ to CNTs and their influences on the electrochemical performances of Si/CNTs composite have been systematically studied. The Si nanoparticle partly reacts with CNTs and forms Si-C bonds in the interface when the mass ratio of SiO₂ to CNTs is above 1.5. The electrochemical performance of this three-phase heterostructure (Si/CNTs-2) are significantly improved due to the Si-C chemical bonding. A high initial reversible capacity of 1100.2 mAh g⁻¹ at 0.2 A g⁻¹ is obtained, and the capacity of 922.4 mAh g⁻¹ remains after 200 cycles with a high capacity retention of 83.3 %. The rate capability is excellent and the capacity is 797 mAh g⁻¹ at 5 A g⁻¹ and remains 612.3 mAh g⁻¹ after 1000 cycles. The interfacial design of Si/CNTs composite provides guidance to prepare high- performance Si/C composite anode.