State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding Xi Road, Shanghai, 200050, China.
University of Chinese Academy of Sciences, Beijing, 100039, China.
Adv Mater. 2018 Feb;30(7). doi: 10.1002/adma.201704166. Epub 2018 Jan 8.
Mg batteries have the advantages of resource abundance, high volumetric energy density, and dendrite-free plating/stripping of Mg anodes. However the injection of highly polar Mg cannot maintain the structural integrity of intercalation-type cathodes even for open framework prototypes. The lack of high-voltage electrolytes and sluggish Mg diffusion in lattices or through interfaces also limit the energy density of Mg batteries. Mg-S system based on moderate-voltage conversion electrochemistry appears to be a promising solution to high-energy Mg batteries. However, it still suffers from poor capacity and cycling performances so far. Here, a ZIF-67 derivative carbon framework codoped by N and Co atoms is proposed as effective S host for highly reversible Mg-S batteries even under high rates. The discharge capacity is as high as ≈600 mA h g at 1 C during the first cycle, and it is still preserved at ≈400 mA h g after at least 200 cycles. Under a much higher rate of 5 C, a capacity of 300-400 mA h g is still achievable. Such a superior performance is unprecedented among Mg-S systems and benefits from multiple factors, including heterogeneous doping, Li-salt and Cl addition, charge mode, and cut-off capacity, as well as separator decoration, which enable the mitigation of electrode passivation and polysulfide loss.
镁电池具有资源丰富、体积能量密度高、镁阳极无枝晶电镀/剥离等优点。然而，即使对于开放式框架原型，高极性的镁的注入也不能维持插层型阴极的结构完整性。缺乏高压电解质和镁在晶格或界面中的扩散缓慢也限制了镁电池的能量密度。基于中压转化电化学的 Mg-S 体系似乎是高能 Mg 电池的一种有前途的解决方案。然而，到目前为止，它仍然存在容量和循环性能差的问题。在这里，提出了一种由 N 和 Co 原子共掺杂的 ZIF-67 衍生的碳骨架作为有效的 S 主体，用于高度可逆的 Mg-S 电池，即使在高倍率下也是如此。在第一个循环中，其放电容量高达 ≈600 mA h g，至少 200 次循环后仍保持 ≈400 mA h g。在更高的倍率 5 C 下，仍可实现 300-400 mA h g 的容量。这种卓越的性能在 Mg-S 体系中是前所未有的，这得益于多种因素，包括不均匀掺杂、锂盐和 Cl 添加剂、充电模式和截止容量以及隔膜修饰，这些因素缓解了电极钝化和多硫化物损失。
