Multi-Faceted Binder Enhancement via Slurry-Applicable Thiol-Ene Click Chemistry for Low-Pressure-Operable All-Solid-State Batteries

Abstract

Ensuring low-pressure operability is imperative in the practical deployment of all-solid-state batteries (ASSBs) with sulfide solid electrolytes, highlighting the pivotal roles of functional binders. Herein, slurry-applicable thiol-ene click reaction-derived modifications of styrene-butadiene rubber (SBR) binders are introduced to enhance the electrochemo-mechanical stabilities of composite cathodes under low operating pressures. Two key modifications are realized: the grafting of carboxylate functional groups to improve the adhesion and cross-linking to enhance the modulus and elasticity. A key insight gained is that cross-linking is considerably more critical in improving the low-pressure performance than adhesion enhancement. Electrochemical evaluations using single-crystalline LiNi0.8Co0.1Mn0.1O2|Li6PS5Cl|(Li-In) half-cells at 0.3 MPa indicate that LiNi0.8Co0.1Mn0.1O2 electrodes with the cross-linked binder exhibit superior electrochemical performances, including higher initial discharge capacities and improved initial Coulombic efficiencies and capacity retentions compared to those of the unmodified-SBR-based electrodes (163 vs. 133 mA h g-1, 68% vs. 73%, and 67% vs. 75% at the 100th cycle, respectively). Comprehensive analyses, including operando electrochemical pressiometry, reveal that cross-linking effectively maintains the electrode integrity, thereby stabilizing the interfacial resistance during cycling. These findings offer critical design guidelines for practical, high-performance ASSB systems.