Reactive Aramid Nanofiber-Reinforced Polyvinyl-Alcohol-Based Solid Polymer Electrolyte for High-Performance Li Metal Batteries

Solid polymer electrolytes (SPEs) with high ionic conductivity and strong mechanical properties are preconditions for the stable cycling of high-performance Li metal batteries. However, single-polymer SPEs often have low ionic conductivity, which greatly limits their further application. Herein, a SPE composed of polyvinyl alcohol (PVA), reactive aramid nanofibers (RANFs), and lithium bistrifluoromethanesulfonimide (LiTFSI) is prepared using a simple solution-casting method. After introducing the RANFs, the SPE of RANFs/PVA-containing LiTFSI not only exhibits high mechanical properties but also has good thermal stability. The RANFs/PVA SPE constructed from the strong hydrogen bond interaction between rigid RANFs and flexible PVA shows high migration efficiency of lithium ions. When the loading amount of RANFs is 2 wt %, the ionic conductivity of RANFs/PVA reaches ∼7.7 × 10 –4 S·cm –1, and the lithium-ion migration number is ∼0.54 at 60 °C. Toward the Li|RANFs/PVA-2 wt %|LiFePO 4 full cell, the discharge specific capacity could reach 162.5 mA h·g –1 at 60 °C and 0.1 C. Meanwhile, the Li|RANFs/PVA-2 wt %|LiFePO 4 battery also shows outstanding long-term cycling performance and could maintain 81% of the initial capacity after 1200 cycles at 1 C. The solid-state Li|RANFs/PVA|LiFePO 4 cell also exhibits excellent resilience in destructive tests such as cell bending, piercing, and cutting.