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Multiple stretchability has never been demonstrated as supercapacitors because the hydrogel used cannot fully recover after being heavily deformed. Now, a highly reversibly stretchable all‐polymer supercapacitor was fabricated using a developed double network hydrogel (DN hydrogel) as electrolyte and pure polypyrrole (PPy) as electrode. The DN hydrogel provides excellent mechanical properties, which can be stretched up to 500 % many times and then restore almost 100 % of the original length. To fabricate the fully recoverable stretchable supercapacitor, we annealed a free‐standing pure conducting polymer film as electrode so that the electrodes induced retardance is minimized. The as‐fabricated DN hydrogel/pure conducting polymer supercapacitors can be perfectly recovered from 100 % strain with almost no residual deformation left and the electrochemical performance can be maintained even after 1000 stretches (but not bending). [ABSTRACT FROM AUTHOR]

Abstract Three challenges remain unsettled for current flexible energy storage devices. One is that most developed devices are not soft enough to conform various deformations; another is that they can hardly guarantee a stable energy output when being dynamically deformed―most of the ever-reported tests on flexibility are performed under static conditions; the third is that they lack sufficient toughness at device level, meaning they are vulnerable to severe mechanical stresses. We believe these problems must be well settled before wearable devices can be practically applied. Here we report a hydrogel with excellent energy-dissipating ability that can be simultaneously used as high-performance electrolyte, super-tough separator and highly effective electrode protector for supercapacitors. The developed supercapacitor is highly soft and super tough at device level. It can well maintain its stable output when being dynamically bent and exhibits high resistance to severe mechanical stimuli including blade-cut, hammering, etc. It can be arbitrarily deformed into irregular shapes while keeping original performances. Moreover, it can even survive extremely harsh conditions including 6 days' treading and 50 times of car run-over without notable deterioration in capacitance and long-term stability. This super tough supercapacitor shows great potential in truly wearable applications involving severe mechanical stresses and impacts. Graphical abstract fx1 Highlights • A dual-crosslinked hydrogel with enhanced modulus and superior energy dissipation capability is developed. • The hydrogel functions as high-performance electrolyte, super-tough separator and highly effective electrode protector. • The resultant supercapacitor shows high resistance to various dynamic mechanical stimuli. • The supercapacitor is highly flexible and arbitrarily deformable. • The supercapacitor exhibits super toughness to endure catastrophic mechanical impacts. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Research into flexible energy‐storage devices with high energy density and superior mechanical performance has aroused considerable interest for the development of flexible electronics. Numerous new materials and strategies have been developed to obtain soft, safe, and high‐performance flexible electrodes, which are essential components of flexible energy storage devices. The common preparation methods and fabrication techniques of flexible electrode are summarized, including their mechanisms, operations, advantages and disadvantages, applicable conditions, and suitable materials. The electrode materials are also briefly discussed according to their characteristics and morphologies, and suggestions on the method preferred for different materials are given. Perspectives on the development of flexible‐electrode fabrication are also given. [ABSTRACT FROM AUTHOR]