Composite Cathodes with Succinonitrile-Based Ionic Conductors for Long-Cycle-Life Solid-State Lithium Metal Batteries

Poor interfacial contacts between cathode active materials and solid-state electrolytes in solid-state lithium (Li) metal batteries often lead to a poor Li-ion conductive pathway, and thus a short cycle life and a low energy density. In this work, we synthesized succinonitrile (SCN)-based ionic conductors (ICs) with different flowability at room temperature for using in the composite cathodes and investigated the effect of the ICs on the cycle performance of the solid-state Li metal batteries with a poly(vinylidene fluoride) (PVDF)-based polymer electrolyte separator. Our results showed that the gel-like SCN-LiClO₄ IC was superior to the flowable SCN-LiTFSI [lithium bis(trifluoromethanesulfonyl)imide] IC and the rigid SCN-LiClO₄ IC. The gel-like IC can build an effective Li-ion conduction path in the cathodes, establish a stable cathode/electrolyte interface with a small interfacial resistance change during cycling, and allow a high mass loading of active materials, which enables a long cycle life and high energy density of solid-state batteries.