Synthesis, structure and electrochemical characterization, and dynamic properties of double core branched organic–inorganic hybrid electrolyte membranes

Organic–inorganic hybrid electrolyte membranes based on the reaction of tri-block copolymer poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether), 3-isocyanatepropyltriethoxysilane and central core 2,4,6-trichloro-1,3,5-triazine doped with LiClO4 were synthesized by a sol–gel process to obtain a double core branched structure. The structural and dynamic properties of the materials thus obtained were systematically investigated by a variety of techniques including alternate current impedance, Fourier transform infrared spectroscopy, differential scanning calorimetry, multinuclear solid-state NMR and 7Li diffusion coefficient measurements. A VTF (Vogel–Tamman–Fulcher)-like temperature dependence of ionic conductivity was observed for solid hybrid electrolyte membranes, implying that the diffusion of charge carriers was assisted by the segmental motions of the polymer chains. The Li-ion mobility was determined from 7Li static NMR linewidth and diffusion coefficient measurements and correlated with their ionic conductivities. A maximum ionic conductivity of 6.2×10−5 Scm−1 was obtained at 30 °C for the solid hybrid electrolyte membrane with a [O]/[Li] ratio of 32. After swelled in electrolyte solvent, the plasticized hybrid membrane exhibited a maximum ionic conductivity of 7.2×10−3 Scm−1 at 30 °C. The good value of electrochemical stability window (~5 V) makes the plasticized hybrid electrolyte membrane promising for lithium-polymer battery applications.