Department of Chemical and Materials Engineering, University of Alberta , 9107 116th Street, Edmonton, Alberta, T6G 2V4, Canada.
ACS Nano. 2014 May 27;8(5):4415-29. doi: 10.1021/nn4063598. Epub 2014 Apr 16.
Here we provide the first report on several compositions of ternary Sn-Ge-Sb thin film alloys for application as sodium ion battery (aka NIB, NaB or SIB) anodes, employing Sn50Ge50, Sb50Ge50, and pure Sn, Ge, Sb as baselines. Sn33Ge33Sb33, Sn50Ge25Sb25, Sn60Ge20Sb20, and Sn50Ge50 all demonstrate promising electrochemical behavior, with Sn50Ge25Sb25 being the best overall. This alloy has an initial reversible specific capacity of 833 mAhg(-1) (at 85 mAg(-1)) and 662 mAhg(-1) after 50 charge-discharge cycles. Sn50Ge25Sb25 also shows excellent rate capability, displaying a stable capacity of 381 mAhg(-1) at a current density of 8500 mAg(-1) (∼10C). A survey of published literature indicates that 833 mAhg(-1) is among the highest reversible capacities reported for a Sn-based NIB anode, while 381 mAhg(-1) represents the optimum fast charge value. HRTEM shows that Sn50Ge25Sb25 is a composite of 10-15 nm Sn and Sn-alloyed Ge nanocrystallites that are densely dispersed within an amorphous matrix. Comparing the microstructures of alloys where the capacity significantly exceeds the rule of mixtures prediction to those where it does not leads us to hypothesize that this new phenomenon originates from the Ge(Sn) that is able to sodiate beyond the 1:1 Na:Ge ratio reported for the pure element. Combined TOF-SIMS, EELS TEM, and FIB analysis demonstrates substantial Na segregation within the film near the current collector interface that is present as early as the second discharge, followed by cycling-induced delamination from the current collector.
本文首次报道了几种三元 Sn-Ge-Sb 薄膜合金作为钠离子电池 (NIB，NaB 或 SIB) 负极材料的组成，其中采用了 Sn50Ge50、Sb50Ge50 和纯 Sn、Ge、Sb 作为基准材料。Sn33Ge33Sb33、Sn50Ge25Sb25、Sn60Ge20Sb20 和 Sn50Ge50 均表现出良好的电化学性能，其中 Sn50Ge25Sb25 的综合性能最佳。该合金的初始可逆比容量为 833 mAhg(-1)（在 85 mAg(-1)时），经过 50 次充放电循环后为 662 mAhg(-1)。Sn50Ge25Sb25 还具有出色的倍率性能，在 8500 mAg(-1)（约 10C）的电流密度下可稳定保持 381 mAhg(-1)的容量。对已发表文献的调查表明，833 mAhg(-1)是报道的基于 Sn 的 NIB 负极中最高可逆容量之一，而 381 mAhg(-1)是最佳快速充电值。HRTEM 表明，Sn50Ge25Sb25 是由 10-15nm 的 Sn 和 Sn 合金化的 Ge 纳米晶组成的复合材料，这些纳米晶在非晶基质中密集分散。将容量明显超过混合物预测值的合金的微观结构与容量未超过混合物预测值的合金的微观结构进行比较，使我们假设这种新现象源于 Ge(Sn)，其能够在纯元素报道的 1:1 Na:Ge 比例之外进行钠化。结合 TOF-SIMS、EELS TEM 和 FIB 分析，证明在靠近集流器界面的薄膜内存在大量的 Na 分离，这早在第二次放电时就已存在，随后在循环过程中与集流器发生分层。
