Advances in next-generation soft electronic devices rely on the development of highly deformable, healable, and printable energy generators to power these electronics. Development of deformable or wearable energy generators that can simultaneously attain extreme stretchability with superior healability remains a daunting challenge. We address this issue by developing a highly conductive, extremely stretchable, and healable composite based on thermoplastic elastomer with liquid metal and silver flakes as the stretchable conductor for triboelectric nanogenerators. The elastomer is used both as the matrix for the conductor and as the triboelectric layer. The nanogenerator showed a stretchability of 2500% and it recovered its energy-harvesting performance after extreme mechanical damage, due to the supramolecular hydrogen bonding of the thermoplastic elastomer. The composite of the thermoplastic elastomer, liquid metal particles, and silver flakes exhibited an initial conductivity of 6250 S cm −1 and recovered 96.0% of its conductivity after healing.

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polyanilines (0.12 S cm −1 ) [14] are made for strain sensors, but such conductivities are not high enough for energy storage applications. Until now, SH supercapacitors were reported using an SH electrolyte [15] or SH sealant, [16] but the restretchability after breaking/healing was not reported. Similarly, most self-healing batteries [17,18] and supercapacitors [19][20][21][22][23] did not provide the stretchability. Recently, an SH electrode for Li-ion battery has been reported using the foam structure with self-healing polymer coating, however, the device was only evaluated in the coin cell, because a Li metal counter electrode is rigid. [24] Therefore, there is an urgent need to realize fully SH energy storage devices with recoverable electrochemical performances based on stretchable electrodes with mechanical and electrical healability under strain and/ or damage.Ga-based liquid metals (LMs) are fascinating materials as soft electronics, [25,26] because they are infinitely deformable while retaining metallic conductivity [25] and useful for self-healing electrodes where an autonomic LM filling restores the broken circuits. [27,28] Some prior works were attempted to introduce LMs into electrochemical energy storage devices. [29,30] Nevertheless, utilizing LMs into soft electrochemical devices has encountered severe constraints due to the high electrochemical activity of gallium (−1.22 V vs normal hydrogen electrode (NHE)) and the instability of LM during electrochemical operation. The thickness of surface oxide (β-Ga 2 O 3 ) layer that stabilizes LM in air [25,26] can be altered by the applied voltage, inducing the interfacial tension changes and shape reconfiguration of conductors, [31,32] thus making it difficult to be used as a stable conductor for electrochemical applications. Recently, stretchable metal-air fiber battery was reported, nevertheless, it was only used as a primary battery due to the corrosion of Ga in KOH electrolyte (2Ga + 6H 2 O → 2Ga(OH) 3 +3H 2 ). [33] Hence, an innovative approach is essential to create a LM-based electrode for a stretchable and electrochemically stable SH energy storage devices.Autonomic self-healing is attractive in comparison with other healing approaches that require external stimulus to trigger the reversible reaction. [34] Previous studies have shown that the specific strong hydrogen-bonding (HB) modules [35,36] and prevalent weaker HB motifs [37,38] are effective for forming supramolecular Stretchable and self-healing (SH) energy storage devices are indispensable elements in energy-autonomous electronic skin. However, the current collectors are not self-healable nor intrinsically stretchable, they mostly rely on strain-accommodating structures that require complex processing, are often limited in stretchability, and suffer from low device packing density and fragility. Here, an SH conductor comprising nickel flakes, eutectic gallium indium particles (EGaInPs), and carboxylated polyurethane (CPU) is presented. An energy storage device is constructed by the two S...

For emerging biocompatible, wearable, and stretchable epidermal electronic devices, it is essential to realize novel stretchable conductors with the attributes of transparency, low‐cost and nontoxic components, green‐solvent processbility, self‐healing, and thermal stabililty. Although conducting materials–rubber composites, ionic hydrogels, organogels have been developed, no stretchable material system that meets all the outlined requirements has been reported. Here, a series of P(SPMA‐r‐MMA) polymers with different ratios of ionic side chains is designed and synthesized, and it is demonstrated that the resulting stretchable ionic conductors with glycerol are transparent, water processable, self‐healable, and thermally stable due to the chemically linked ionic side chain, satisfying all of the aforementioned requirements. Among the series of polymer gels, the P(SPMA0.75‐r‐MMA0.25) gel shows optimum conductivity (6.7 × 10−4 S cm−1), stretchability (2636% of break at elongation), and self‐healing (98.3% in 3 h) properties. Accordingly, the transparent and self‐healable P(SPMA0.75‐r‐MMA0.25) gels are used to realize thermally robust actuators up to 100 °C and deformable and self‐healable thermal sensors.

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