Wang Xiao, Liu Shujie, Zhang Yijun, Wang Haiye, Aboalhassan Ahmed Abdulqawy, Li Guang, Xu Gang, Xue Chenliang, Yu Jianyong, Yan Jianhua, Ding Bin
College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.
State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, China.
ACS Appl Mater Interfaces. 2020 Aug 26;12(34):38132-38139. doi: 10.1021/acsami.0c10005. Epub 2020 Aug 17.
Silicon (Si) is a promising anode material to replace the broadly adopted graphite due to its high capacity and abundant source. However, Si anodes suffer from severe problems of huge volume change (∼300%), and the commonly used binders like poly(vinylidene fluoride) (PVDF) cannot accommodate such changes. Here, we report a tough block copolymer PVDF--Teflon (PTFE) binder that can coalesce pulverized Si and thus enhance the stability of Si anodes. The suspension copolymerization of vinylidene fluoride and tetrafluoroethylene produces elastic PVDF--PTFE with large breaking elongations of >250% and high viscosity as well as high ionic conductivity and thermal stability. We show that 5 wt % of the binder forms elastic cobweb structures in the electrode matrix that can effectively coalesce Si particles and conductive agents together, enabling long cycling stability (>250 cycles) and high rate performance (1 C) for electrodes at a commercial-level Si loading of 1 mg·cm. The findings point out to a promising strategy for developing highly elastic and tenacious binders for electrodes with large volume changes during the electrochemical reactions.
硅（Si）因其高容量和丰富的来源，是一种有潜力取代广泛使用的石墨的负极材料。然而，硅负极存在严重的问题，即体积变化巨大（约300%），而常用的粘结剂如聚偏氟乙烯（PVDF）无法适应这种变化。在此，我们报道了一种坚韧的嵌段共聚物PVDF-Teflon（PTFE）粘结剂，它可以使粉碎的硅凝聚，从而提高硅负极的稳定性。偏氟乙烯和四氟乙烯的悬浮共聚产生了具有大于250%的大断裂伸长率、高粘度以及高离子电导率和热稳定性的弹性PVDF-PTFE。我们表明，5 wt%的粘结剂在电极基体中形成弹性蜘蛛网结构，能够有效地将硅颗粒和导电剂凝聚在一起，在1 mg·cm的商业级硅负载量下，使电极具有长循环稳定性（>250次循环）和高倍率性能（1 C）。这些发现指出了一种有前景的策略，用于开发在电化学反应期间具有大体积变化的电极的高弹性和坚韧粘结剂。
