Structural and Electrochemical Performance of Ternary Type-I Clathrate As Anode Materials for Lithium-Ion Batteries
In our group, we have investigated silicon clathrate materials, which have cage-like structures, as an anode material of Li-ion battery. Our studies on type II clathrate based on Na24Si136 show that lithium insertion is energetically feasible inside silicon cages that are fully occupied by other guest atoms. However, large amounts of lithium insertion cause a transformation between from the clathrate structure to an amorphous silicide and eventually Li15Si4 .
This presentation discusses the structure and electrochemical performance of ternary Ba-X-Si type-I clathrate (where X = Cu, Al). Polycrystalline silicon clathrate materials are synthesized using thermal annealing and arc-melting methods. Electrochemical and structural analysis show these cage-like silicon structures have the ability to allow lithium insertion and removal without a large volume change or pulverization. Lithiation/delithiation of silicon clathrate anodes will be presented comparing to that of diamond cubic and amorphous silicon. Ex-situ X-ray diffraction, X-ray photoelectron spectroscopy, and nuclear magnetic resonance are also employed to understand the structural changes upon lithiation and delithiation.
 K.S. Chan, C.K. Chan, W. Liang, Silicon clathrate anodes for lithium ion batteries. U.S. Patent Application no. 12/842,224 (2010)