Giant Negative Thermopower Enabled by Bidirectionally Anchored Cations in Multifunctional Polymers.

The lack of high-quality ionic thermoelectric materials with negative thermopowers has stimulated scientists' broad research interest. The effective adjustment of the interaction between ions and a polymer network is an important way to achieve high-quality ion thermoelectric properties. Integrating different types of ion-polymer interactions into the same thermoelectric device seems to lead to unexpected gains. In this work, we propose a strategy for bidirectionally anchoring cations to synergistically generate a giant negative thermopower and high ionic conductivity. This is mainly achieved through synergistic ion-polymer coordination and Coulomb interactions. An ionic thermoelectric material was prepared by infiltrating a polycation electrolyte [poly(diallyldimethylammonium chloride)] with CuCl 2 into the poly(vinyl alcohol)-chitosan aerogel. The confinement effect of copper-coordinated chitosan on cations, the repulsive property of the polycationic electrolyte on cations, and the unique chemical configuration of a transition metal chloride anion ([CuCl 4 ] 2- ) are the fundamental guarantees for achieving a thermopower of -28.4 mV·K -1 . Moreover, benefiting from the high charge density of the polycationic electrolyte, we obtain an ionic conductivity of 40.5 mS·cm -1 . These findings show the application prospect of synergistic different types of ion-polymer interactions in designing multifunctional ionic thermoelectric materials.