Superior self-healability and stretchability are critical elements for the practical wide-scale adoption of personalized electronics such as portable and wearable energy storage devices. However, the low healing efficiency of self-healable supercapacitors and the small strain of stretchable supercapacitors are fundamentally limited by conventional polyvinyl alcohol-based acidic electrolytes, which are intrinsically neither self-healable nor highly stretchable. Here we report an electrolyte comprising polyacrylic acid dual crosslinked by hydrogen bonding and vinyl hybrid silica nanoparticles, which displays all superior functions and provides a solution to the intrinsic self-healability and high stretchability problems of a supercapacitor. Supercapacitors with this electrolyte are non-autonomic self-healable, retaining the capacitance completely even after 20 cycles of breaking/healing. These supercapacitors are stretched up to 600% strain with enhanced performance using a designed facile electrode fabrication procedure.

Stretchability and compressibility of supercapacitors is an essential element of modern electronics, such as flexible, wearable devices. Widely used polyvinyl alcohol-based electrolytes are neither very stretchable nor compressible, which fundamentally limits the realization of supercapacitors with high stretchability and compressibility. A new electrolyte that is intrinsically super-stretchable and compressible is presented. Vinyl hybrid silica nanoparticle cross-linkers were introduced into polyacrylamide hydrogel backbones to promote dynamic cross-linking of the polymer networks. These cross-linkers serve as stress buffers to dissipate energy when strain is applied, providing a solution to the intrinsically low stretchability and compressibility shortcomings of conventional supercapacitors. The newly developed supercapacitor and electrolyte can be stretched up to an unprecedented 1000 % strain with enhanced performance, and compressed to 50 % strain with good retention of the initial performance.

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Here we propose a facile, one-pot in situ free radical polymerization strategy to prepare self-healable, super tough graphene oxide (GO)/poly(acrylic acid) (PAA) nanocomposite hydrogels by using Fe 3+ ions as a cross-linker. The 3-dimensional network structure of the GO/PAA nanocomposite hydrogels is facilitated by dual cross-linking effects through dynamic ionic interactions: (i) first cross-linking points 10 are Fe 3+ ions creating ionic cross-linking among PAA chains; (ii) second cross-linking points are GO nanosheets linking PAA chains through Fe 3+ coordination. When the GO/PAA nanocomposite hydrogels are under stretching, the ionic interactions among PAA chains can dynamically break and recombine to dissipate energy, while the GO nanosheets coordinated to the PAA chains maintain the configuration of the hydrogels and work as stress transfer centers transferring the stress to the polymer matrix. In this 15 regard, the GO/PAA nanocomposite hydrogels exhibit superior toughness (tensile strength = 777 kPa, work of extension = 11.9 MJ m -3 ) and stretchability (elongation at break = 2980%). Furthermore, after being treated at 45 o C for 48 h, the cut-off GO/PAA nanocomposite hydrogels exhibit a good self-healing property (tensile strength = 495 kPa, elongation at break = 2470%). The self-healable, super tough GO/PAA nanocomposite hydrogels lay a basis for developing advanced soft materials holding potential 20 applications in modern biomedical engineering and technology.

We present a facile strategy to synthesize self-healable tough and highly stretchable hydrogels. Our design rationale for the creation of ionic cross-linked hydrogels is to graft an acrylic acid monomer on the surface of vinyl hybrid silica nanoparticles (VSNPs) for the growth of poly(acrylic) acid (PAA), and the obtained VSNP-PAA nanobrush can be used as a gelator. Physical cross-linking through hydrogen bonding and ferric ion-mediated ionic interactions between PAA polymer chains of the gelators yielded ionic nanocomposite physical hydrogels with excellent and balanced mechanical properties (tensile strength 860 kPa, elongation at break ∼2300%), and the ability to self-repair (tensile strength ∼560 kPa, elongation at break ∼1800%). The toughness and stretchability arise from the reversible cross-linking interactions between the polymer chains that help dissipate energy through stress (deformation) triggered dynamic processes. These unique properties will enable greater application of these hydrogel materials, especially in tissue engineering.