聚合物-金属导体纳米复合热电材料研究

Thermoelectric (TE) materials, as one kind of eco-and renewable energy materials, can directly convert heat into electricity. Organic-inorganic thermoelectric composites exhibit favorable properties than their organic or inorganic counterparts. However, their zT values are comparatively low, the relationships among component, structure and TE performance are unclear, the electrical and thermal transport mechanisms are complicated, thus limiting the development and applications. Currently, most thermoelectric composites employed carbon based nanomaterials and semiconductor nanoparticles, yet metal conductors with lower cost and equally high conductivity are barely reported. To resolve these issues, this proposal aims to investigate polymer-metal conductor nanocomposite based thermoelectric materials. Firstly, we will prepare the insulating polymer-metal conductor TE composites to clarify the TE contribution from inorganic part. Next, we will fabricate the conducting polymer-metal conductor TE composites in order to reveal the effects of organic polymer part. Furthermore, we will examine the influences of the coupling between organic and inorganic components on charge carrier and phonon transport, which in turn guide the experimental optimization. Based on these studies, we will implement effective chemical doping strategy, improve the avenue towards nanocomposites, and modulate both electrical and thermal conduction channels to remarkably improve the TE conversion efficiency. Lastly, we will explore the potential applications of these hybrids on the wearable and flexible TE modules.

热电材料是一种能实现热能和电能之间直接转换的新型清洁可再生能源材料。有机-无机复合热电材料呈现出比传统无机或有机热电材料更为优异的性能，但zT优值较低，组分-结构-性能的相关性仍不清楚，电、热输运机制尚不明确，因而制约其发展和应用。目前用于复合热电材料的无机部分如碳基纳米材料、半导体纳米颗粒等主要是利用其高电导率，而价格更为低廉的同样具有高电导率的金属却鲜见报道。针对这些问题，本项目拟开展聚合物-金属导体复合热电材料的研究。首先，制备以绝缘聚合物基体的复合热电材料，明晰无机部分对热电性能的贡献；进一步将金属导体与导电聚合物纳米复合，考察有机聚合物部分对热电参数的影响规律；最后，探究有机与无机组分之间的耦合对载流子及声子输运行为的影响机制。在此基础上，实施有效的化学掺杂手段，优化纳米复合的路径，开展对导电、导热通道的微观调控，以大幅提高热电转换效率，进而探索在可穿戴式柔性热电元件的潜在应用。

有机-无机复合热电材料既具有类似于无机热电材料的高电导率，又具备有机材料的柔性、易加工性及电子结构可调控性等优点，但与传统无机材料相比，有机-无机复合热电材料的zT值仍处于较低水平，组分–结构–性能的关联性仍不清楚，电、热输运机制尚不明确，因而制约其发展和应用。基于上述问题，本项目分别通过构建以绝缘、导电聚合物与无机纳米导体复合的新型热电材料体系，明晰其中有机聚合物、无机导体对热电性能的各自贡献，揭示分子结构与电、热输运机制的内在关联，进一步开展结构形貌调控，以大幅改善各热电参数，最终制备高效稳定的柔性热电材料及器件。例如，我们首先制备了绝缘聚合物聚偏氟乙烯（PVDF）与金属Ni纳米线的复合材料，其弯曲性能优异，且可保持形变，由于有机/无机组分间较大的界面热阻及声子散射，获得较低的热导率，首次证明了绝缘聚合物和金属这两类本身不良的热电材料，复合之后却可以呈现出优越的热电性能。其次，通过引入磁场诱导磁性金属纳米线发生取向，从而在取向方向极大地提高了电学传输性能。随着金属纳米线渗流网络的形成，Seebeck系数和电导率呈现解耦合的现象，成功实现了两者的同步提高，使得热电性能获得显著的提升，揭示了无机部分与热电性能的内在关联。接着，系统研究了基于一维、二维和三维纳米结构为填料的PVDF基复合体系的热电材料性能，表明了填料的拓扑结构是实现“电子渗流-声子绝缘”的关键因素，填料的本征Seebeck系数和填料之间的接触电阻也起着重要作用。进一步，将绝缘聚合物替换为半导体聚合物，显著提高了热电纳米复合材料的Seebeck系数，并通过引入第三组分的方式改善了有机与无机组分之间的连接性，使得电导率也得以提升，从而明晰了有机部分与复合材料热电性能之间的关联机制。最后，将所制备的热电纳米复合材料用于构筑柔性热电器件，证明了其在实际应用中具有极大的潜力。