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 threephase 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.