Highly stretchable, compressible and arbitrarily deformable all-hydrogel soft supercapacitors

Most developed flexible energy storage devices lack sufficient softness and toughness to tolerate various deformations, such as stretching, compressing, twisting, folding and puncturing, meanwhile guarantee a stable energy output required for the soft human-machine interfaces and intelligent wearable electronics. In this work, all-hydrogel soft supercapacitors consisting of reversibly deformable hydrogel electrodes and electrolyte are constructed without using additional stretchable substrate or separator membrane. Both electrode and electrolyte contain the same polyacrylamide/sodium alginate dual-network hydrogel matrix, making them possess superb self-adhesion due to hydrophilic interaction/hydrogen bonds, and highly softness/toughness thanks to the energy-dissipative mechanism. After adding carbon nanotube conductive network/electrode active material and electrolyte salt/redox couple in the hydrogel matrix, the newly developed supercapacitor with all-in-one architecture is intrinsically highly stretchable/compressible and can even be deformed arbitrarily under various severe stress-strain deformation conditions at device level, simultaneously deliver high areal capacitance (232 mF cm^-2 at 5 mV s^-1 and 128 mF cm^-2 at 1 mA cm^-2) and maintain stable energy output. The simple device architecture, novel structural components, steady mechanical properties combined with excellent electrochemical properties make the soft supercapacitors promising for truly wearable applications.