Supramolecular Thermo-Electrochemical Cells: Enhanced Thermoelectric Performance by Host–Guest Complexation and Salt-Induced Crystallization

Thermo-electrochemical
cells have potential to generate thermoelectric
voltage 1 order higher than that given by semiconductor materials.
To overcome the current issues in thermoelectric energy conversion,
it is of paramount importance to grow and fulfill the full potential
of thermo-electrochemical cells. Here we report a rational supramolecular
methodology that yielded the highest Seebeck coefficient of ca. 2.0
mV K–1 around ambient temperatures. This is based
on the encapsulation of triiodide ions in α-cyclodextrin, whose
equilibrium is shifted to the complexation at lower temperatures,
whereas it is inverted at elevated temperatures. This temperature-dependent
host–guest interaction provides a concentration gradient of
redox ion pairs between two electrodes, leading to the eminent performance
of the thermo-electrochemical cells. The figure of merit for this
system, zT reached a high value of 5 × 10–3. The introduction of host–guest chemistry
to thermoelectric cells thus provides a new perspective in thermoelectric
energy conversion.

热电化学电池（thermo-electrochemical cells）具备产生比半导体材料高出一个数量级的热电电压的潜力。为解决当前热电能量转换领域现存的问题，充分发挥热电化学电池的全部应用潜能至关重要。本研究报道了一种合理设计的超分子方法，在室温附近实现了约2.0 mV·K⁻¹的最高塞贝克系数（Seebeck coefficient）。该方法基于三碘离子在α-环糊精（α-cyclodextrin）中的包合作用：低温下平衡向络合反应方向移动，高温下则发生逆转。这种温度依赖的主客体相互作用在两个电极之间形成了氧化还原离子对的浓度梯度，从而赋予热电化学电池优异的性能表现。该体系的无量纲热电优值（figure of merit, zT）达到了5×10⁻³的较高水平。将主客体化学引入热电电池领域，为热电能量转换研究提供了全新的视角。