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Block Copolymer Electrolytes with Excellent Properties in a Wide Temperature Range
journal contribution
posted on 2020-06-30, 02:13 authored by Fan Wu, Longfei Luo, Zhehao Tang, Dong Liu, Zhihao Shen, Xing-He FanA series
of block copolymers (BCPs) with a polynorbornene backbone
containing short poly(ethylene oxide) (PEO) side chains and rigid
side chains were synthesized by tandem ring-opening metathesis polymerization
(ROMP). The contents of PEO in the BCPs are regulated by the degrees
of polymerization (DPs) of main chains. The crystallization of the
PEO side chains is suppressed. Confirmed by small-angle X-ray scattering
(SAXS) results, the BCPs doped with lithium salt and ionic liquid
self-assemble into lamellar (LAM) or hexagonally packed cylindrical
(HEX) nanostructures that remain stable up to 200 °C. The ionic
conductivity (σ) values of the complexes with an optimized doping
ratio are above the order of 1 × 10–4 S/cm
over the temperature range of −25 to 200 °C, and the highest
is 6.41 × 10–3 S/cm at 200 °C, reaching
the top level for PEO-based polymer electrolytes at high temperatures.
In addition, the results of shear rheological experiments indicate
that the thermally stable electrolyte membranes can maintain the solid
state up to 200 °C. These BCP electrolytes with high σ
values and excellent thermal stability in a wide temperature range
may be applied in high-temperature lithium-ion batteries.