Synthesis and electrochemical characteristics of mesoporous silicon/carbon/CNF composite anode

Abstract

Si/C/CNF composites as anode materials for lithium-ion batteries were examined to improve the capacity and cycle performance. Si/C/CNF composites were prepared by the fabrication process including the synthesis and magnesiothermic reduction of SBA-15 to obtain Si/MgO by ball milling and the carbonization of phenol resin with CNF and HCl etching. Prepared Si/C/CNF composites were then analysed by BET, XRD, FE-SEM and TGA. Among SBA-15 samples synthesized at reaction temperatures between 50 and 70 ℃, the SBA-15 at 60 ℃ showed the largest specific surface area. Also the electrochemical performances of Si/C/CNF composites as an anode electrode were investigated by constant current charge/discharge test, cyclic voltammetry and impedance tests in the electrolyte of LiPF6 dissolved in mixed organic solvents (EC: DMC: EMC = 1: 1: 1 vol%). The coin cell using Si/C/CNF composites (Si: CNF = 97: 3 in weight) showed better capacity (1,947 mAh/g) than that of other composition coin cells. The capacity retention ratio decreased from 84% (Si: CNF = 97: 3 in weight) to 77% (Si: CNF = 89: 11 in weight). It was found that the Si/C/CNF composite electrode shows an improved cycling performance and electric conductivity.