Influence of Solid Electrolyte Interphase Stabilization on Cycling Performance of Silicon-Graphite Composite Battery Anodes

Abstract

Silicon-graphite composites have drawn significant attention as promising anode materials for higher energy density Li-ion batteries due to larger theoretical specific capacity of silicon than currently commercialized graphite.1 They, however, suffer from a large volume change during lithiation and delithiation, causing the particle cracking, structural degradation of the electrode, an instability of the solid electrolyte interphase (SEI) and finally leading to poor cycle life. In order to address the problems, several strategies in the aspects of improved electrical conductivity and buffering effect of volume change have been developed but the fabrication of silicon composites with carbon materials combined with the use of functional binder and electrolyte additives 2- 4 are recognized as a promising approach. In this presentation, we report the control of electrode-electrolyte interfacial reaction and the formation of a stable SEI layer using various additives, and SEI characterization using ATR FTIR spectroscopy combined with X-ray photoelectron spectroscopy. In the conventional electrolyte of 1M LiPF6/EC:EMC (3:7 volume ratio), the half-cell with Si-graphite composite anode, which is cycled between 0.01 and 1.5 V at the rate of 0.2C, shows a rapid capacity fade and a low capacity retention of 68 % at the 50th cycle. On the contrary, the cell with the designed blended additives yields improved capacity retention to 81 %, with well-maintained coulombic efficiency of higher than 99 %. Further studies of additive-dependent SEI composition and stability and their correlation to cycling performance would be discussed in the meeting. Acknowledgements This research was supported by the Korean Ministry of Trade, Industry & Energy (10049609), and Nano-Material Technology Development Program by the Ministry of Science, ICT and Future Planning (2009-0082580).