Fluorine-containing soluble polyimide binder improves the cycling performance of Si/C anode in lithium batteries

Si/C anode is regarded as a competitive candidate for next generation lithium-ion batteries due to its outstanding specific capacity. However, the practical application of Si/C anode is still obstructed by its significant volumetric variation during charging and discharging. Numerous studies have demonstrated that polyimide (PI) can effectively mitigate volumetric deformation. However, the majority of these investigations have predominantly utilized insoluble PI, whose high-temperature imidisation process would produce large internal stresses and holes that are detrimental to the performance of the battery. In this study, two types of soluble polyimides were synthesized and applied to Si/C anode: a fluorine- and silicon-containing variant and a fluorine- and amino-group-containing variant. Both PI-FS and PI-FN have relatively well bonding properties. Meanwhile, PI-FN, which introduces amino groups, has lower energy gap and better conductive ability. Compared with PVDF, the PI-based binder changes the component distribution of the solid electrolyte interface and significantly improves the cycling stability of the Si/C anode.