Porous Si anode materials for lithium rechargeable batteries

Si anode materials for lithium rechargeable batteries have received much attention due to their high capacity. The Si itself can alloy with lithium up to Li4.4Si, corresponding to 4212 mAh/g (4.4Li + Si ↔ Li4.4Si). However, the large volume expansion of over 300% due to the formation of various LixSiy phases generates enormous mechanical stress within the ionic character material, which becomes pulverized during the first few cycles and loses electrical integrity. Although such a drastic volume change cannot be removed completely, the degree of the volume change can be effectively reduced to utilize its application in anode materials. In this regard, when porous particles contain ordered pores, these pores act as a buffer layer for volume changes, demonstrating another means of controlling the volume expansion/contraction. In this review, recent developments in porous Si anodes, such as mesoporous nanowires, 3D porous particles, and nanotubes have been highlighted.