Yolk-shell structured silicon-polypyrrole (Si-PPy) composite has been prepared by an in situ chemical polymerization approach. The designed parcel method significantly improves the cycling stability and rate capability compared to those of bare silicon. The Si-PPy composite exhibits a high specific capacity of 1400mAhg-1 after 100 cycles, which is approximately 4 times higher than bare Si. Moreover, the Si-PPy composite delivers a high reversible capacity of ∼1200mAhg-1 at a high current density of 10Ag-1, while the bare Si only achieves a low capacity of ∼490mAhg-1 at the same current density. The outstanding electrochemical properties of the Si-PPy composites are attributed to the stability and conductivity of the PPy shell and the nanoscale structure of the composite.
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