Electrochemical Characteristics of Pitch Coated Silicon/Graphite Anode Composites Using Surface Modification Process

Abstract

The electrochemical characteristics of pitch coated graphite / silicon composites were investigated as anode material in lithium ion batteries. The anode materials were prepared with etched graphite using nickel chloride hexahydrate to create spherical pores on the graphite surface. The pore size was controlled depending on the calcination retention time and optimized for the insertion of silicon nanoparticles. Scanning electron microscopy, x-ray diffraction and thermogravimetric analysis were used to analyze the physical properties of pitch coated graphite / silicon composites. The electrochemical characteristics of the batteries were investigated by charge-discharge cycle, rate performance, cyclic voltammetry and electrochemical impedance spectroscopy tests in the eletrolyte of 1.0 M LiPF6 ( EC : DMC : DEC = 1 : 1 : 1 vol % ). Graphite/silicon/pitch electrode showed better electrochemical properties than the graphite electrode, and even nickel etched graphite was superior to graphite. Also, it was confirmed that both capacity and rate performance were significantly improved when the ratio of graphite, silicon, and pitch is 8 : 1 : 1 ( G8 Si1 P1 ). It is found that G8 Si1 P1 have the initial discharge capacity of 680 mAh / g, the capacity retention ratio of 90 % during 100 cycles and the retention rate capability of 91 % in 2 C / 0.1 C, 87 % in 5 C / 0.1 C.