Synthesis of an aliphatic hyper-branched polycarbonate and determination of its physical properties for solid polymer electrolyte use

An aliphatic hyper-branched polycarbonate (HBPC) was synthesized as a novel host material for solid polymer electrolytes (SPEs). The HBPC was synthesized through A2 + B3 polymerization to yield a branched polycarbonate structure. HBPC-based SPE films were prepared by drying mixed solutions of HBPC and 1–60 mol% LiClO4. The temperatures for 5% weight loss (Td5s) of the HBPC-based SPEs were in the range of 174.4–189.3 °C, higher than those in normal use. The HBPC-based SPE exhibited higher ionic conductivities (1.86 × 10−4 S∙cm−1 at 70 °C and 8.52 × 10−6 S∙cm−1 at 30 °C) than a poly(trimethylene carbonate) (LPC)-based SPE (4.79 × 10−6 S∙cm−1 at 70 °C and 8.32 × 10−8 S∙cm−1 at 30 °C) for 20 mol% lithium content. Activation energies of lithium ion transport for the HBPC- and LPC-based SPEs were estimated to be 11.47 and 15.88 kJ∙mol−1, respectively. Introduction of this branched structure in polycarbonates is effective for promoting lithium ion transport. [Display omitted] •Aliphatic hyper-branched polycarbonate (HBPC) was synthesized by polycondensation.•HBPC films containing LiClO4 were evaluated as solid polymer electrolytes (SPEs).•The Li ion conductivities were compared with that of linear polycarbonate-based SPE.•The SPEs showed relatively high ionic conductivity and low activation energy.•Introduction of branched structure is effective for the lithium ion transport.