Fu Xuewei, Dunne Francis, Chen Min, Zhong Wei-Hong
School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164, USA.
Nanoscale. 2020 Mar 5;12(9):5483-5493. doi: 10.1039/c9nr10966h.
Developing flexible, robust and lightweight sulfur cathodes by rationally designing their structures and configurations through a viable and scalable strategy is a critical enabler for fulfilling flexible lithium-sulfur (Li-S) batteries. However, besides the requirements for cathode flexibility, intrinsic limitations from the shuttling of lithium polysulfides and the growth of Li dendrites have restricted the widespread implementations of Li-S batteries. Here, we report a wet-processed strategy by dissolving and recrystallizing S in a suitable solvent to fabricate a flexible, binder-free S cathode. Integrating the resulting S cathode with a dual-functional separator has demonstrated to be able to suppress both the shuttle effect and growth of dendritic Li. The wet-processed strategy not only enables the fabrication of flexible and binder-free S-nanomat cathodes, but also facilitates the deposition of the cathodes on the separators. Meanwhile, a dual-functional separator is fabricated by vapor-phase polymerization of polypyrrole (PPy) coating on both surfaces of the commercial separator, which leads to the reduction of the shuttle effect and the suppression of the growth of dendritic Li simultaneously. As a result, by integrating the S-nanomat and the dual-functional separator, the cathode exhibits exceptional mechanical properties and electrochemical performance. Li-S pouch cells are further demonstrated to show stable cycling performance in the bending state, indicating the feasibility of the integrated S cathode for flexible Li-S batteries.
通过可行且可扩展的策略合理设计其结构和构型来开发灵活、坚固且轻质的硫阴极，是实现柔性锂硫（Li-S）电池的关键因素。然而，除了对阴极柔韧性的要求外，多硫化锂穿梭和锂枝晶生长的内在限制阻碍了Li-S电池的广泛应用。在此，我们报道了一种湿法策略，即将硫溶解并在合适的溶剂中重结晶以制备柔性、无粘结剂的硫阴极。将所得硫阴极与双功能隔膜集成已证明能够抑制穿梭效应和枝晶锂的生长。该湿法策略不仅能够制备柔性且无粘结剂的硫纳米阴极，还便于阴极沉积在隔膜上。同时，通过在商业隔膜的两个表面上进行聚吡咯（PPy）涂层的气相聚合制备了双功能隔膜，这同时导致穿梭效应的降低和枝晶锂生长的抑制。结果，通过集成硫纳米阴极和双功能隔膜，阴极表现出优异的机械性能和电化学性能。进一步证明Li-S软包电池在弯曲状态下具有稳定的循环性能，表明集成硫阴极用于柔性Li-S电池的可行性。
