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Abstract Although ionic thermoelectric (iTE) materials can have very high thermopower, it is of great significance to develop novel methods to further improve the ionic thermopower and figure of merit ( ZT i ). Here, significant improvement in the thermopower and thus the ZT i value of an ionogel by cationic doping, is reported. Doping sodium dicyanamide (Na:DCA) into the ionogels of poly(vinylidene fluoride‐ co ‐hexafluoropropylene) (PVDF‐HFP) and 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIM:DCA) that is an ionic liquid can greatly enhance the thermopower. This is attributed to the interactions between the doped Na + cations and DCA – anions, thereby increasing the difference in the mobilities of EMIM + cations and DCA – anions. Moreover, through the combination with the solid networks engineering by an anti‐solvent to PVDF‐HFP, the PVDF‐HFP/EMIM:DCA ionogel doped with 0.5 mol% Na + with respect to EMIM + exhibits an ionic thermopower of 43.8 ± 1.0 mV K –1 , ionic conductivity of 19.4 ± 0.3 mS cm –1 and thermal conductivity of 0.183 W m –1 K –1 at the relative humidity of 85% and room temperature. The corresponding ZT i value thus reaches 6.1 ± 0.4, much higher than the previous ZT i records of iTE materials. These ionogels can be used in the iTE capacitors for the thermoelectric conversion.
Liu et al. (Sat,) studied this question.