Tailoring Slurries Using Cosolvents and Li Salt Targeting Practical All-Solid-State Batteries Employing Sulfide Solid Electrolytes

Polymeric binders that can undergo slurry fabrication and minimize the disruption of interfacial Li+ contact are imperative for sheet-type electrodes and solid electrolyte films in practical all-solid-state Li batteries (ASLBs). Although dry polymer electrolytes (DPEs) are a plausible alternative, their use is complicated by the severe reactivity of sulfide solid electrolytes and the need to dissolve Li salts. In this study, a new scalable fabrication protocol for a Li+-conductive DPE-type binder, nitrile-butadiene rubber (NBR)-LiTFSI, is reported. The less-polar dibromomethane and more-polar hexyl butyrate in cosolvents work synergistically to dissolve NBR and LiTFSI, while preserving Li6PS5Cl0.5Br0.5. It is found that the dispersion of NBR can be controlled by the fraction of the antisolvent (hexyl butyrate), which in turn affects the corresponding performance of the ASLBs. Sheet-type LiNi0.70Co0.15Mn0.15O2 electrodes tailored using NBR-LiTFSI outperform those prepared using the conventional insulating binder (NBR) in terms of capacity (163 vs 147 mA h g(-1)) and initial Coulombic efficiency (78.9 vs 70.4%), which is attributed to the facilitated interfacial Li+ transport, as confirmed by Li-6 nuclear magnetic resonance and electrochemical measurements. Moreover, NBR-LiTFSI is functional at 70 degrees C and in a graphite anode. Finally, the promising performance of pouch-type LiNi0.70Co0.15Mn0.15O2/graphite ASLBs is also demonstrated.

Automated summary

In this study, a new scalable fabrication protocol for a Li+-conductive dry polymer electrolyte (DPE)-type binder, nitrile-butadiene rubber (NBR)-LiTFSI, is reported. The dispersion of NBR can be controlled by adjusting the fraction of antisolvent in the cosolvents, ultimately affecting the performance of all-solid-state Li batteries. Sheet-type electrodes tailored using NBR-LiTFSI demonstrate superior capacity and initial Coulombic efficiency compared to those prepared using conventional insulating binder, attributed to facilitated interfacial Li+ transport.