Polysiloxane/Poly(vinylidene fluoride)‐co‐Hexafluoropropylene Polymer Blend‐based Lithium‐Ion Conducting Polymer Electrolytes for Room‐Temperature Lithium‐Metal Batteries

Abstract

To harness the synergistic effect of different polymer chains, poly(methyl(2‐(tris(2‐H methoxyethoxy)silyl)ethyl)siloxane)) grafted with Si‐tripodant centers (2550EO) known for their flexible structure was physically blended with poly(vinylidene fluoride‐co‐hexafluoropropylene (PVdF‐HFP). Here, 2550EO containing varying amounts of amide salts (LiF(SO2CF3)2 (LiTFSI)) was used as the main matrix. PVdF‐HFP was used in concentrations of up to 30 % to increase the film‐forming ability of 2550EO/LiTFSI, and a series of solid polymer electrolyte (SPE) membranes were prepared. After incorporating the blended SPE with a minute amount of organic carbonates (only 15 wt%), the electrochemical features, such as Li+ conductivity and transference number (tLi+), significantly increased. For example, a tLi+ of 0.42 and ionic conductivities of 0.64 and 0.3 S cm−1 at 60 °C and 25 °C, respectively, were achieved. In addition, the electrochemical stability exceeded 5 and 4.8 V at 25 °C and 60 °C, respectively. Thus, a high Li/LiFePO4 battery performance with high coulombic efficiencies exceeding 96 % and 98 % at 60 °C and 25 °C were achieved at 0.1 C, respectively. This was due to the superiority of the polysiloxane structure over its organic counterpart, attributed to its highly flexible backbone, high segmental mobility, and outstanding thermal and chemical stability.