Rational Design of Dynamically Super-Tough and Super-Stretchable Hydrogels for Deformable Energy Storage Devices.

Hydrogels possess unique polymer networks that offer flexibility/stretchability, high ionic conductivity, and resistance to electrolyte leakage, making them suitable for deformable energy storage devices. Endowing the mechanical functionality of the hydrogel electrolytes focus on either enhancing the stretchability or the toughness. However, the stretchability and the toughness are generally a trade-off that the stretchable gels are intrinsically prone to damage and sensitive to notches and cracks. Here, the regulating strategies on the hydrogel's mechanical properties are provided to develop the designated hydrogel electrolyte, where different polymeric network structures are constructed, including single network structures, semi-interpenetrating network structures, and interpenetrating dual-network structures. A comprehensive comparison of these polymer network structures is conducted to evaluate their mechanical stretchability and toughness. Designing super-tough and super-stretchable hydrogels based on specific application requirements can be realized by striking a balance by regulating the hydrogel structure. In specific, incorporating semi-interpenetrating networks significantly can enhance stretchability to achieve a break elongation up to 1300%, while the interpenetrating dual-networks can largely improve the toughness to realize the extraordinary fracture toughness of 6.843 kJ m-2. These findings offer valuable designing guidance for designated hydrogel electrolytes and the deformable zinc-silver battery is demonstrated with high mechanical stability and electrochemical performance.

Anti-Freezing Strategies of Electrolyte and their Application in Electrochemical Energy Devices.

Wider scenes of human's activities under low temperature demand promising performance of anti-freezing electrochemical energy devices, and the promotion of performance is mainly limited by electrolyte. However, despite many relevant research works reported, there are still few reviews that systematically and comprehensively summarize these modified approaches and applications. In this focus review, we classify the prominent anti-freezing strategies as high concentration aqueous electrolyte, organic additives, organic electrolyte and others. Relevant research works have been put to clarify their anti-freezing mechanisms and exhibit the modification effects. Besides, various energy devices including metal-air batteries, non-gas batteries and supercapacitors which employed aforementioned strategies are discussed and their key low-temperature performance indexes are summarized to exhibit the advanced research progress. Finally, we put forward some remaining challenges of these modification strategies toward practical application and propose prospects on future development of low-temperature electrochemical energy devices.