Specific behavior of transition metal chloride complexes for achieving giant ionic thermoelectric properties

When people are keen to exploring the thermoelectric properties of polymer composite inorganic electrolyte aqueous flexible electronic devices, the complicated chemical configuration of transition metal chloride anion has not been paid attention and reported. Here, we demonstrate a hydrated polyvinyl alcohol (PVA)-cellulosic membrane that relies on the thermal gradient diffusion of transition metal and chloride complexe [CuCl4](2-) enhanced by copper-coordinated carboxylated cellulose. The PVA-cellulosic membrane exhibits a thermopower of -26.25 mV center dot K-1, rendering it among the best n-type ionic thermoelectric materials under the same conditions. We attribute the enhanced thermally generated voltage to the highly-coordinated configuration of Cu2+ - Cl-, which converts the independent thermal motion of Cu2+ and Cl- to the higher ion transport heat of [CuCl4](2-) anion via carboxylated cellulose, while this phenomenon do not occur in the other transition metal chlorides. This specific heat transport behavior of [CuCl4](2-) has important implications in designing high-quality ionic thermoelectric materials.