High-performance solid polymer electrolytes for lithium batteries operational at ambient temperature

• Polymer electrolytes were prepared based on poly(ε-caprolactone).
• Optimal performance was attained by addition of 20 mol% carbonate repeating units.
• High total ionic conductivity; 4.1 × 10−5 S cm−1 at 25 °C, 1.1 × 10−4 S cm−1 at 40 °C.
• High Li+ transference numbers; 0.62 at 40 °C, 0.66 at 60 °C.
• Li polymer half-cells were cycled with high stability at room temperature.

Incorporation of carbonate repeating units in a poly(ε-caprolactone) (PCL) backbone used as a host material in solid polymer electrolytes is found to not only suppress crystallinity in the polyester material, but also give higher ionic conductivity in a wide temperature range exceeding the melting point of PCL crystallites. Combined with high cation transference numbers, this electrolyte material has sufficient lithium transport properties to be used in battery cells that are operational at temperatures down to below 23 °C, thus clearly demonstrating the potential of using non-polyether electrolytes in high-performance all-solid lithium polymer batteries.

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