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

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