Si/PANI core/shell composite is simply synthesized by an in-situ chemical polymerization method. The images of the obtained Si/PANI composites show that an amorphous PANI layer is adsorbed evenly on the nano-Si surface with a thickness of about 6 nm, forming the Si/PANI core/shell structure. It is observed that the Si/PANI anodes display the well cycling stability at a high rate of 1 C with the cutoff potential window of 0.01 V and 1.5 V. The initial charge capacity is 2083.8 mAh g(-1), 1015.9 mAh g(-1) and 583.6 mAh g(-1) for the Si/PANI anodes containing 70 wt%, 50 wt% and 30 wt% PANI, respectively. Over 100 cycles, the capacity is kept at 889.6 mAh g(-1), 672.5 mAh g(-1) and 545.3 mAh g(-1) respectively. Furthermore, the reversible capacity of the Si/PANI anode containing 70 wt% PANI still maintains at 1087.8 mAh g(-1) even at the rates of 1 C, 0.5 C and 0.2 C after each 100 cycles. The results indicate that the PANI shell accommodates the large volume expansion and shrinkage of Si core during the lithium intercalation and extraction process, which facilitates the contact of electrode materials, thus ensures the higher discharge and charge capacity and better cycling stability. (C) 2013 The Electrochemical Society. All rights reserved.