Electrochemical Properties of a TetraPEG-based Gel Electrolyte Containing a Nonflammable Fluorinated Alkyl Phosphate for Safer Lithium-ion Batteries

We report a nonflammable gel electrolyte based on two key soft materials: 1) a homogeneous polymer network prepared from tetra-armed poly(ethylene glycol) (TetraPEG) and 2) a tris(2,2,2-trifluoroethyl) phosphate (TFEP)-based electrolyte solution. At the equilibrium swelling state, the concentration of the polymer in the TetraPEG gel was relatively low, at only 5.6 wt.%. The TetraPEG gel exhibits a wide electrochemical window of similar to 5.0V and thus works well as an electrolyte for a positive electrode, i.e., a lithium iron phosphate (LiFePO4).