锑硅纳米复合薄膜作为钠离子电池负极材料的电化学行为研究

摘要

近年来, 合金作为钠离子电池的负极材料具有较高的比容量而受到广泛关注.然而, 硅与钠离子的电化学反应活性很低, 硅基合金型负极材料鲜有报道.本研究通过脉冲激光沉积技术制备了锑硅(Sb-Si)纳米复合薄膜, 并对其作为钠离子电池负极材料的电化学性能和反应机理进行了研究.电化学性能表征发现, 锑硅纳米复合薄膜在10 μA/cm2的电流密度下, 循环100次后能保持约0.011 mAh/cm2(270 mAh/g)的可逆比容量, 远优于同样方法和条件下制备的单质锑和单质硅薄膜电极的电化学性能.进一步的研究表明, 在放电过程中, Sb和Si分别和钠离子发生合金化反应生成了Na3Sb和NaSi的纳米晶.在充电过程中, Na3Sb和NaSi纳米晶发生可逆的脱钠反应, 重新形成单质Sb和Si纳米晶粒.大量存在于锑硅纳米复合薄膜中的异质晶界有利于钠离子的扩散和输运, 从而提高了纳米复合薄膜电极的电化学性能.%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 lim-ited, 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 be-tween 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 nano-composite thin films are benefical to Na-ion transportation, thus enhance the electrochemical performance of the nanocomposite thin film electrode.