Invited Presentation: Research on Nano-Si/C Nanocomposites as Anode for Li-Ion Batteries

Abstract

Nanosized silicon has been paid much attention as high capacity anode materials for Li-ion batteries since our first report in 1999. The main challenge for Si anode is the large volume variation during lithium insertion and extraction, which shows a linear dependence on the capacity. Several problems are caused consequently: 1) the total specific capacity of anode has to be limited due to fairly strict restriction on volume variation of batteries during operating, especially for tablet devices. Thus, the advantages of the high theoretical capacity and the volumetric energy density are not as significant as expected. 2) The solid electrolyte interphase (SEI) on the surface of silicon is not as stable as graphite and could be very thick, which consume lithium from cathode and nonaqueous electrolyte irreversibly, leading to low columbic efficiency, capacity fading, increase of internal resistance and gas release. 3) Nanosized silicon particles tend to agglomerate or merge into big pieces and follow further cracking, leading to the formation of the SEI on freshed surface and the loss of electronic contact for active particles. In order to solve above problems, great efforts have been paid and many strategies have been considered. Among them, SiOx, amorphous Si alloy and nano-Si/C composite are more promising for practical application in view of the electrochemical performances and cost. In this report, we will summarize our investigation on the formation of very thick solid electrolyte interphase (SEI) on naked silicon anode at low rate, direct 3Dvisualization of multiple layer structured SEI. The optimization on additive, binder and microstructure for controlling interfacial properties and maintaining the structure stability of nano-Si/C composite anodes will be reported. Acknowledgment: Financial support from CAS project (KJCX2-YW-W26), "Strategic Priority Research Program" of the Chinese Academy of Sciences,Grant No. XDA09010102 and National project 973 (2012CB932900) are appreciated.