Two-macro-phased fluorinated polymer electrolytes for lithium batteries

Interfacial properties and mechanical rigidity of polymer electrolytes are important for inhibiting the lithium dendrite growth in lithium metal batteries. Introducing rigid and crosslinking moieties in polymer electrolytes improves mechanical strength while decreases their ion transport capacity. Herein, we report fluorinated polymer electrolytes (FPEs) containing two macro-phases, e.g., one rigid and crosslinking polymer-brush networks (CPBNs) phase swollen by Li salts and the other phase composing of amorphous methoxy poly(ethylene glycol) (MPEG) with a -OCH2CF3 terminal (MPEG-3F) and dissolved Li salts. The crosslinking CPBNs phase enhances the mechanical strength of FPEs, decreases the Li stripping/plating overpotential and enables dendritefree lithium cycling. The MPEG-3F phase facilitates the Li ion transport and decreases the interface resistance. The optimized FPEs have a considerable mechanical strength, a room-temperature ionic conductivity of 2.96 x 10-4 S/cm, and a wide ESW of 5.0 V at room temperature. The assembled LiFePO4/FPEs/Li and LiFePO4/FPEs/ Li@C cells show excellent cycling performance.