Taming of heteropoly acids into adhesive electrodes using amino acids for the development of flexible two-dimensional supercapacitors

The development of heteropoly acid (HPA)-based functional soft materials is an important topic in material science and energy devices. The noncovalent supramolecular strategy has continued to evolve in its capacity to create innovative HPA materials with increasingly complex functions that are not accessible using conventional covalent synthesis. In this study, we explored a type of HPA-containing conductive adhesive via a simple noncovalent strategy. We demonstrated that concomitant ionic bonds, hydrogen bonds, charge–transfer interactions, π–π stacking, and hydrophobic effects enable aromatic amino acids, HPAs, and carbon materials to crosslink with each other. Consequently, the formed soft materials exhibited collective advantages, such as exceptional wet adhesion to flexible substrates and electrolytes, adaptive and deformable properties, and conduction and reversible redox behavior. These features allow us to fabricate flexible two-dimensional (2D) supercapacitors (SCs) by conveniently injecting all-in-one adhesives onto flexible substrates. The capacitance retention of the fabricated flexible SC was 92% during bending and folding deformation. In particular, the adhesives can be patterned into tandem 2D SCs for high-voltage output with metal-free interconnects.