High-entropy polymer produces a giant electrocaloric effect at low fields
High-entropy polymer produces a giant electrocaloric effect at low fields
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高熵聚合物在低场下产生巨大的电热效应
DOI：
10.1038/s41586-021-04189-5
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发表时间：
2021-12-23
期刊：
影响因子：
64.8
通讯作者：
Zhang, Q. M.
中科院分区：
文献类型：
--
作者：
Qian, Xiaoshi;Han, Donglin;Zhang, Q. M.
对电热（EC）效应的十多年研究已经产生了EC材料和EC多层芯片，其满足热量热泵（1-3）所需的5 K的最小EC温度变化。然而，这些EC温度变化是通过施加高电场（4-8）（接近其介电击穿强度）产生的，这导致EC性能的快速退化和疲劳。在这里，我们报道了一类EC聚合物，其在50 MV m（-1）下表现出37.5 J kg（-1）K-1的EC熵变和7.5 K的温度变化，在相同的场强下比最先进的EC聚合物提高了275%。我们表明，转化成共价双键的聚（偏氟乙烯-三氟乙烯-氯氟乙烯）聚乙烯中的少量的氯氟乙烯基团显着增加的极性实体的数量，并提高了聚合物的极性-非极性界面面积。聚合物中的极性相采用松散相关的高熵态，具有低的电场诱导开关能垒。该聚合物在实际EC冷却应用所需的低场下保持超过一百万次循环的性能，这表明这种策略可能会产生适用于热量热泵的材料。
More than a decade of research on the electrocaloric (EC) effect has resulted in EC materials and EC multilayer chips that satisfy a minimum EC temperature change of 5 K required for caloric heat pumps(1-3). However, these EC temperature changes are generated through the application of high electric fields(4-8) (close to their dielectric breakdown strengths), which result in rapid degradation and fatigue of EC performance. Here we report a class of EC polymer that exhibits an EC entropy change of 37.5 J kg(-1) K-1 and a temperature change of 7.5 K under 50 MV m(-1), a 275% enhancement over the state-of-the-art EC polymers under the same field strength. We show that converting a small number of the chlorofluoroethylene groups in poly(vinylidene fluoride-trifluoroethylenechlorofluoroethylene) terpolymer into covalent double bonds markedly increases the number of the polar entities and enhances the polar-nonpolar interfacial areas of the polymer. The polar phases in the polymer adopt a loosely correlated, high-entropy state with a low energy barrier for electric-field-induced switching. The polymer maintains performance for more than one million cycles at the low fields necessary for practical EC cooling applications, suggesting that this strategy may yield materials suitable for use in caloric heat pumps.