Abstract
Recent years,alloy attracted significant research interest as anode materials for room temperature sodium-ion batteries,due to its high specific capacity and low cost.Among them,the study of Si-based alloy anodes are very limited,owing to the low electrochemical reactivity of Si with Na ions.In this study,Sb-Si nanocomposite thin films were successfully prepared by pulsed laser deposition.Their electrochemical performance and reaction mechanism were studied as new anode materials for sodium ion batteries.They exhibited a reversible specific capacity of about 0.011 mAh/cm2（corresponding to 270 mAh/g） over 100 cycles at a rate of 10 μA/cm2,which is much higher than those for pure Si or Sb thin films prepared under the same condition.The investigation of electrochemical reaction mechanism reveals that Na3Sb and NaSi nanocrystallines are formed after discharge,due to the alloying reaction between the Sb-Si films and Na.During the recharge process,Na3Sb and NaSi phases both decompose and form Sb and Si nanocrystallines again,respectively.It is proposed that heterogeneous grain boundaries existing in the Sb-Si nanocomposite thin films are benefical to Na-ion transportation,thus enhance the electrochemical performance of the nanocomposite thin film electrode.