Highly ion-conducting, robust and environmentally stable poly(vinyl alcohol) eutectic gels designed by natural polyelectrolytes for flexible wearable sensors and supercapacitors

Abstract

Flexible conductive materials have received a lot of attention due to their versatility in wearable devices, etc. Eutectic gels are expected to replace the traditional hydrogel as a new generation of soft conductors. Here, sodium alginate (SA), a polysaccharide polyelectrolyte with surface charge, was ingeniously used to construct the energy dissipation and ion transport network. Thus, a double-network polyvinyl alcohol composite eutectic gel with various physical effects was prepared by salting out and solvent replacement process. The obtained gels showed excellent mechanical properties, frost resistance and stability; the maximum fracture strain and toughness can reach 3.87 MPa and 9.87 MJ/m3, respectively. Surprisingly, the –COO− contained in SA plays an active role in the ion transport, and the conductivity (0.30 S/m) was improved by 5 times. Based on this composite gel, a supercapacitor with a wide operating window of 1.7 V and good cyclic charging and discharging stability (capacitance retention at 82.1 % after 1500 cycles) was prepared. And the prepared sensor can sensitively monitor the movement of human joints and perform handwriting recognition. This strategy realizes the balance between mechanical properties and conductivity of eutectic gel and opens up the application of natural polyelectrolytes in the construction of high-performance ion-transport networks.