本文介绍互不溶Sn-Al合金表面上Sn纳米线(直径为100～500 nm)自发生长的两种情况,它们都不需要模板和催化剂。通过SEM、TEM分析和对Al、Sn相的相互作用机理研究表明,这些Sn纳米线具有[200]生长方向,它们的生长与Sn熔点和Al-Sn共晶点的差异,以及Sn-Al合金(块体、薄膜)中存在的残余压应力有关。将含有Sn纳米线的Sn-Al薄膜作为锂离子电池负极材料进行电化学测试,在0.3～1.5 V vs.Li/Li+(Li/Li+为对电极和参比电极)电压范围循环时,它的稳定可逆容量为300 mAh/g。通过与纯Sn薄膜负极比较研究可知,Sn纳米线的一维特征有利于改善Li+的扩散动力学,从而提高Sn-Al薄膜电极的电化学性能。
Thin-film lithium-ion batteries are the most competitive power sources for various kinds of micro-electro-mechanical systems and have been extensively researched.The present paper reviews the recent progress on Sn-based thin-film anode materials,with particular emphasis on the preparation and performances of pure Sn,Sn-based alloy,and Sn-based oxide thin films.From this survey,several conclusions can be drawn concerning the properties of Sn-based thin-film anodes.Pure Sn thin films deliver high reversible capacity but very poor cyclability due to the huge volume changes that accompany lithium insertion/extraction.The cycle performance of Sn-based intermetallic thin films can be enhanced at the expense of their capacities by alloying with inactive transition metals.In contrast to anodes in which Sn is alloyed with inactive transition metals,Sn-based nanocomposite films deliver high capacity with enhanced cycle performance through the incorporation of active elements.In comparison with pure Sn anodes,Sn-based oxide thin films show greatly enhanced cyclability due to the in situ formation of Sn nanodispersoids in an Li2O matrix,although there is quite a large initial irreversible capacity loss.For all of these anodes,substantial improvements have been achieved by micro-nanostructure tuning of the active materials.Based on the progress that has already been made on the relationship between the properties and microstructures of Sn-based thin-film anodes,it is believed that manipulating the multi-phase and multi-scale structures offers an important means of further improving the capacity and cyclability of Sn-based alloy thin-film anodes.
