Modified poly(vinylidene fluoride) polymer binder enables ultrathin sulfide solid electrolyte membrane for all-solid-state batteries

Abstract

All-solid-state batteries (ASSBs) employing high-ionic-conductivity sulfide solid electrolytes (SEs) are the most promising next-generation batteries. Scalable fabrication of sulfide SE membranes is the priority for mass production of ASSBs. However, due to the poor chemical stability of sulfide SEs, the wet-slurry-based preparation of sulfide SE membranes is still hindered by limited choices of solvent-binder systems. Herein, we reported a modified poly(vinylidene fluoride) (M-PVDF) binder to achieve environment-friendly fabrication of sulfide SE membranes. Copolymerization is firstly performed on the widely-used PVDF binder to decrease crystallinity, which facilitate excellent solubility in the isobutyl isobutyrate-based slurry. Utilizing this efficient M-PVDF binder, the sulfide SE membrane achieves a high ionic conductivity of 2 mS cm⁻¹ at 25 °C, an ultra-thin thickness of 26 μm, and good flexibility. The resulting ASSBs exhibit excellent rate performance with 53.51 % capacity utilization ratio at 5C. The ASSB also maintains high capacity retention rates of 96.9 % after 350 cycles under 0.5C at 25 °C and 87.8 % after 1000 cycles under 5C at 45 °C. This work can facilitate the non-toxic wet-slurry-based manufacturing of sulfide SE membrane, helping to promote the commercialization of ASSBs.