Tin (Sn)-based anodes attract extensive attention for magnesium ion batteries however challenges and issues exist, such as relatively difficult alloying reaction, sluggish diffusion kinetics and rapid capacity decay. Herein, we introduce a second phase of bismuth (Bi) with varying contents into Sn via magnetron co-sputtering and get insight into how the Bi introduction boosts the electrochemical reactivity of Sn through experimental and density functional theory (DFT) calculations. The experimental results reveal that the introduction of Bi can effectively trigger the alloying reaction of Sn with Mg and the further increasing of Bi significantly improves the electrochemical performance of Sn–Bi electrodes. Moreover, the activated function of introducing the Bi phase into Sn is found in the bulk rolled Sn–Bi system. The DFT calculations demonstrate that the introduction of Bi into Sn obviously lowers the defect formation energy of Mg insertion in Sn, which further rationalizes the experimental results. Additionally, operando X-ray diffraction is performed to probe the activation process and magnesiation/demagnesiation mechanisms of the Sn–Bi electrode. The activation mechanism of Bi on Sn alloying with Mg is discussed, considering the function of second phase, the influence of Bi solid solution, as well as the size effect.

锡（Sn）基阳极引起镁离子电池的广泛关注，但是存在挑战和问题，例如相对困难的合金化反应，缓慢的扩散动力学和快速的容量衰减。在这里，我们通过磁控管共溅射将具有不同含量的铋（Bi）的第二相引入到Sn中，并通过实验和密度泛函理论（DFT）计算来了解Bi的引入如何提高Sn的电化学反应性。实验结果表明，Bi的引入可以有效地引发Sn与Mg的合金化反应，Bi的进一步增加显着改善了Sn-Bi电极的电化学性能。此外，在批量轧制的Sn-Bi系统中发现了将Bi相引入Sn的激活功能。DFT计算表明，将Bi引入Sn中明显降低了Mg插入Sn中的缺陷形成能，从而进一步合理化了实验结果。另外，进行操作X射线衍射以探测Sn-Bi电极的激活过程和放​​大/缩小功能。考虑到第二相的功能，Bi固溶体的影响以及尺寸效应，讨论了Bi对Sn与Mg合金化的活化机理。