Engineering nanoscale solid networks of ionogel for enhanced thermoelectric power output and excellent mechanical properties

Thermoelectric (TE) materials can directly convert heat into electricity, which is of great significance to sustainable development. Thermoelectric ionogels have received extensive attention due to high thermopower and excellent flexibility. However, their low ionic conductivity and poor mechanical properties severely limit their potential applications. Here, engineering the solid network structure of polyvinyl alcohol (PVA) hydrogel by ionic liquids (IL) significantly improves the ionic conductivity as well as the overall thermoelectric properties and mechanical properties. The introduction of 1-ethyl-3-methylimidazolium dicyanamide (EMIM:DCA) into PVA solution before the formation of PVA/IL ionogels reduces the mobility of polymer chains, resulting in significantly reduced crystal size. Thus, the microstructure of PVA/IL ionogels promotes the ion transport ability. The ionic conductivity of PVA/IL ionogels increases from 0.77 to 2.78 S m−1, resulting in a power factor 70 times higher than that of PVA hydrogel. In addition, the abundant microcrystalline regions in PVA/IL ionogels with nanoscale network structure can dissipate a large amount of energy and endow the PVA/IL ionogels with excellent mechanical properties, which can greatly broaden the application potential of ionogels.