Flexible Composite Solid Electrolyte with an Active Inorganic Filler

Solid polymer electrolytes (SPEs) attract great attention due to their wide electrochemical stability window, low cost, and excellent processability. However, some obstacles, including their low ionic conductivity, poor solid-solid contact between the SPE and lithium metal electrode, and uneven lithium deposition behavior, hinder their application in solid-state lithium batteries. Herein, a flexible composite solid electrolyte is facilely designed and successfully fabricated by introducing reactive petal-like MoS2 nanosheets to a poly(vinylidene fluoride-co-hexa-fluoropropylene) (PVDF-HFP)/lithium bis(fluorosulfonyl)imide (LiFSI) polymer electrolyte. The addition of petal-like MoS2 nanosheets not only greatly improves the room-temperature ionic conductivity to 2.8 × 10-4 S cm-1 but also decreases interfacial impedance and in situ suppresses lithium dendrite growth. In the resulting solid-state batteries, both rate capacity (137 mAh g-1 at 0.54C) and cycling stability (Coulombic efficiency in each cycle close to 100% during 200 cycles) are obtained by employing the electrolyte. In addition, the rational mechanism of MoS2 in improving ion conduction and suppressing lithium dendrite growth is suggested.