Although silicon (Si) exhibits very high theoretical capacity (4200 mAh/g) as an anode for Li-ion batteries, it suffers fast capacity fade because of the large volume expansion during lithiation. Various nanostructured silicon-based materials have been developed to mitigate this problem. Here, we developed porous structured Si-based nanocomposites to alleviate the volume expansion and hence to greatly improve the electrochemcial performance of Si based anodes during charge/discharge processes. In one design, a hollow core-shell structured porous Si-C nanocomposite with void space up to tens of nanometers is designed to accommodate the volume expansion during lithiation. An initial capacity of ~760 mAh/g with 86% capacity retention over 100 cycles is achieved at a current density of 1 A/g. In a separate effort, we have developed macroporous Si with etched channels (diameter ~50 nm).   This macroporous Si exhibits less than 30% overall volume change during charge/discharge process because the internal opening of the channels can accommodate most of volume expansion. The macroposous Si has demonstrated a very stable cycling performance with the capacity of ~600 mAh/g and >90% capacity retention over 300 cycles at a current density of 1A/g. This unique structure eliminates the pulverization of particles with sizes up to tens of microns. It also minimizes the formation of solid electrolyte interface inside the channels and reduces cycle loss due to side reactions.

Porous structured Si-based nanocomposites as high performance Li-ion battery anodes

246th National Meeting (2013)

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