Wednesday, 16 May 2018
Ballroom 6ABC (Washington State Convention Center)
Recently, with increasing use of mobile electronic devices and electric vehicles, demand for electrical energy storage devices is greatly rising. Among them, lithium ion batteries (LIBs) are one of the most attractive devices because of their reasonable cost and energy density. To meet the consumer demand for energy density, high-capacity electrode materials should be developed. Currently, carbonaceous materials such as graphite are widely used in anodes and however, its capacity is limited due to the use of intercalation chemistry (theoretical capacity of graphite: 372 mAh g–1). To increase the capacity of an anode, Li-alloy type materials have been intensively examined. For example, Si has the theoretical capacity of 3580 mAh g–1 for Li15Si4 phase, which is the final phase of electrochemical lithiation. However, the Li-alloying type materials have a problem of cycle performance. When Li ions are inserted and extracted during cycling, the active materials suffer from huge volume expansion and shrinkage (100~400 %). The volume changes cause the mechanical degradation of the active materials and the material can be separated from the current collectors. As a result, the cycle performance of the electrodes is deteriorated. To solve the problem, lots of researchers have tried to prepare composite materials by adopting diverse methods. For instance, composite materials including inactive phases were prepared to alleviate the volume change. In this study, we prepared Sb-Si-C composites as high-capacity anode materials. Antimony (Sb) is considered one of the candidates as Li-alloy type active material and it has the theoretical capacity of 660 mAh g–1 for the Li3Sb phase. To obtain high-capacity and stable cycling stability, porous Sb-Si-C composites were synthesized by high energy mechanical milling and etching process. First, antimony oxide (Sb2O3), magnesium silicide (Mg2Si), and a carbon source were ball-milled. During the milling process, Sb2O3 was reduced to Sb by Mg and the formed MgO phase was removed by a solution etching process. Finally, the porous Sb-Si-C composite was prepared, which was evaluated as LIB anode materials.