Si@环化聚丙烯腈/多壁碳纳米管负极复合材料的制备及电化学性能

通过简单高能球磨和高温热解法制备了锂离子电池Si/C电极复合材料，聚丙烯腈（PAN）包覆的纳米颗粒（Si@PAN）与多壁碳纳米管（MWCNTs）混合，制得Si@环化PAN/MWCNTs（Si@c-PAN/MWCNTs）复合材料作为锂离子电池的负极材料。包覆在纳米Si外层的高温热解后的PAN能够有效缓冲Si在充放电过程中巨大的体积变化产生的应力，同时MWCNTs作为Si@c-PAN的基体阻止Si@c-PAN颗粒的团聚，也提高了Si@c-PAN/MWCNTs复合材料电极的导电性能。电化学测试结果表明，Si@c-PAN/MWCNTs复合材料电极在电流密度为0.2 A/g时，其首次放电比容量达到2 098 mA?h/g，库伦效率达到86%；循环50次后Si@c-PAN/MWCNTs复合材料电极的可逆比容量仍能够达到1 278 mA?h/g，在2 A/g放电时其比容量为600 mA?h/g，仍保持良好的循环稳定性。 

Preparation and electrochemical performance of Si@cyclized-polyacrylonitrile/ multi-walled carbon nanotubes anode composites

Si/C electrode composites were prepared by simple high-energy ball milling and high-temperature pyrolysis. The polyacrylonitrile (PAN) coated nano Si particles (Si@PAN) were mixed with multi-walled carbon nanotubes (MWCNTs) to prepare Si@cyclized-PAN/MWCNTs(Si@c-PAN/MWCNTs) composites as the anode material for lithium ion battery. A thin layer of c-PAN was coated on Si nanoparticles to efficiently accommodate a large volume change of Si particles in cycles. The MWCNTs network functions as matrix for Si@c-PAN nano particles, which not only prevent the agglomeration of Si@c-PAN particles, but also improve the electrical conductivity of electrodes significantly. The electrochemical tests show that the first discharge specific capacity of the Si@c-PAN/MWCNTs composite electrode is 2 098 mA?h/g at the current density of 0.2 A/g and the initial coulomb efficiency is 86%. After 50 cycles, the reversible specific capacity of Si@c-PAN/MWCNTs composite electrode maintains at 1 278 mA?h/g. When the current rate reaches 2 A/g, the specific capacity of Si@c-PAN/MWCNTs composite electrode keeps at 600 mA?h/g, exhibiting good cycle stability.