MIL-125 (Ti) and porous dielectric polymer substrate introducing composite gel polymer electrolyte with enhanced mechanical property, thermal stability and electrochemical property

Abstract

Lithium metal batteries have potentially high energy density, but severe uncontrolled lithium dendrites and unstable side reactions prevent large-scale applications. Serial three-dimensional porous poly (vinylidene fluoride) and copolymer membrane-based composite gel electrolytes are designed by introducing MIL-125 (Ti) and ethylene carbonate. Abundant lithium-ion transportation channels and homogeneous ion transport microregion are provided the new type porous fluoropolymer substrate. We also find that crystalline phase and dielectric properties of serial polymer membrane have significant impact on electrochemical performance for composite gel electrolytes. The mechanical and dielectric property of composite electrolyte enhanced by incorporating uniform and well distribution MIL-125 (Ti), which improve the electrolyte/electrode interface charge distribution and promote uniform lithium deposition, leading to lithium dendrite suppression. MIL-125 (Ti)/P(VDF-TrFE-CTFE) composite membrane shows the enhanced maximum strain of 181 %, thermal stability (188 °C) and corresponding composite gel electrolyte reflects higher ionic conductivity of 1.7 × 10–3 S cm-1 and wider electrochemical window at room temperature than PVDF and PVDF-HFP composite electrolytes. Expectedly, quasi-solid state lithium metal battery of MIL-125 (Ti)/P(VDF-TrFE-CTFE) composite gel electrolyte exhibits higher discharge capacity (152.8 mAh g-1) at 240th cycle and 1 C, longer cycling life and better rate performance under large current density than PVDF and PVDF-HFP composite electrolytes.