Fast self-healing and rebuildable polyphosphate-based metallo-gels with mixed ionic-electronic conductivity.

The development of self-healing materials opens perspectives to fabricate devices with unprecedented lifetimes and recyclability that can be integrated with flexible electronics. However, the timescale at which these materials operate remains an important challenge to overcome. This article describes the fast self-healing behavior of aluminum/iron polyphosphate metallo-gels and their hybrids with polyaniline and gives a detailed investigation of their electrical behaviors. The samples can be cut, molded and healed by manual handling. The rebuilding process is mediated by water uptake and was directly observed by environmental scanning electron microscopy. Metallo-gels with and without polyaniline can be mixed to give homogeneous samples, where the conducting polymer is uniformly distributed within the inorganic matrix. Cyclic voltammetry experiments showed that polyaniline behaves within the metallo-gel in the same manner as it does in aqueous electrolytes. Furthermore, polyaniline adds electronic conductivity to the originally ion-conducting polyphosphate metallo-gel, as demonstrated by impedance spectroscopy. The ionic and electronic conductivities are 1.3-1.7 × 10-2 S·cm-1 and 5.2 × 10-4 S·cm-1 , respectively. Such properties result from the "free" and "bound" water within the hydrogel network and the dynamic nature of the aluminum-phosphate interactions within the supramolecular network. The features presented here make these materials good candidates to be used as moldable electroactive binders in carbon-based electrodes and in all-solid-state flexible separators for repairable electrochemical capacitors and batteries.