Synthesis And Modification Of Silicon-based Composite As Anode Materials For Lithium Ion Batteries

Abstract:Silicon-based material is regarded as one of the most promising anode materials for high energy density Li-ion batteries because of its extremely high theoretical specific capacity and relatively low potential for insertion/extraction of Li+. The research process of silicon based materials for Li-ion batteries had been summarized and the electrochemical performance of Si anode were also investigated. In order to improve the electrochemical performance of Si, two types of silicon-based materials were successfully synthesized. The composites were silicon/graphite/carbon composite and silicon-graphene composite and their morphologies, phase components and electrochemical properties of these materials had also been investigated.The electrochemical performances of flake graphite and nano-Si had been studied. At50mA g-1, the nano-Si anode exhibited a charge capacity of1800.2mAh g-1and discharge capacity of3483.6mAh g-1, the capacity retention was15.2%after20cycles. The charge and discharge capacity of flake graphite were345.8mAh g-1and434.9mAh g-1, respectively, and the capacity kept at370mAh g-1during the cycling.Using flake graphite, nano-Si and glucose monohydrate as raw materials, Si/G/C composites were successfully synthesized via steps of liquid solidification and subsequent pyrolysis. When the mass ratio of Si and graphite was3:7, the as synthesized Si30FG70composite exhibited the best electrochemical performance. The Si30FG70composite delivered an initial charge capacity of733.6mAh g-1and discharge capacity of1048.3mAh g-1, corresponding to an initial columbic efficiency of69.9%at50mA g-1, and the capacity retention was80.1%after20cycles.Si-graphene composite (Si-G composite) had been synthesized via self assembly of nano-Si and graphite oxide (GO) followed by subsequent hydrothermal process. When the concentration of GO solution was2mg/mL, the as synthesized Si-G-2composite showed the best cycling performance. The Si-G-2composite exhibited a first charge capacity of1123.4mAh g-1and discharge capacity of2259.3mAh g-1, along with an initial columbic efficiency of49.7%. A charge capacity of871.1mAh g-1could be achieved after50cycles at100mA g-1, corresponding to the capacity retention of77.5%.