A double network facilitated ion-electron conductor for thermoelectric harvesting with high energy density

As a young member of the thermoelectric (TE) family, ionic thermoelectric (i-TE) technology stands out due to its exceptionally high thermopower. However, the intermittent nature of its heat utilization results in a weak power output, thus limiting its practical application. To tackle this issue, combining i-TE with electronic thermoelectric (e-TE) materials that exhibit stable heat-to-electricity conversion capabilities presents itself as a promising solution. With this aim, we introduced interpenetrating network (IPN) structure in the fabrication process of mixed ionic-electronic TE (MIETE) materials. Specifically, we created a double network MIETE converter through the in-situ polymerization of ionic poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) on a loosely structured poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/lithium bis(trifluoromethane)sulfonimide (LiTFSI) electronic conductive framework. This subsequent construction of the inert network ensures uninterrupted electronic conductivity and boosts density for improved conductivity (σ). The innovative structural design effectively amalgamates thermodiffusion and Seebeck effects, facilitating continuous electricity generation. The resulting hybrid PEDOT:PSS/LiTFSI/PAMPS-LiCl (PLiP) hydrogels exhibit exceptional TE performance, showing a thermopower of 7.86 mV K−1 and σ of 33.3 mS cm−1. It is worth noting that the PLiP hydrogel illustrates a power generation time of over 4 h and an ultra-high energy density of 93.7 J m−2, which exceeds other TE hydrogels based on the thermodiffusion principle.