Three-Dimensional Porous Structural Polyvinylidene Fluoride-Blending Ethylene Carbonate and MIL-125 (Ti) Composite Membrane-Based Gel Polymer Electrolyte for Lithium Metal Battery

Abstract

Lithium metal batteries are considered promising contenders for the next generation of high energy density batteries. However, lithium metal anode with inhomogeneous lithium deposition in liquid electrolyte causes the uncontrolled growth of lithium dendrites. Owing to the high dielectric constant, thermal stability and electromechanical stability of polyvinylidene fluoride, we design a novel gel polymer electrolyte consisting of porous polyvinylidene fluoride polymer matrix, liquid electrolyte, ethylene carbonate and MIL-125 (Ti) (Ti8O8(OH)4(BDC)6, BDC = 1,4-benzene dicarboxylate) for facilitating Li+ transfer and alleviating the growth of lithium dendrites. The high dielectric constant environment facilitates the dissociation of Li+, and the porous polymer matrix structure accommodates more Li+ for fast transfer. Ethylene carbonate reduces the crystallinity of the polymer matrix and improves the ionic conductivity. MIL-125 (Ti) nanoparticles with surface area and uniform micropores improve toughness for enhancing mechanical property, and synergistically promote the Li+ transfer for building stable interfacial phase to alleviate the growth of Li dendrites. Therefore, the gel polymer electrolyte has high ionic conductivity of ∼1.50 × 10−3 S cm−1 at 25 °C, and quasi-solid-state Li/LiFePO4 battery has high discharge capacity of 153.5 mAh g−1 after 250 cycles at 25 °C and 0.3 C.