Smart Quasi‐Solid‐State Electrolytes with the “Dual Insurance” Mechanism for Thermal Safety and Autonomous Operation in Flexible Energy Storage Devices

Abstract The thermal effect crisis poses a significant challenge to large‐scale application of energy storage devices. Hydrogel electrolytes are regarded as promising substrates for these applications due to the ionic conductivity and safety. This work presents a quasi‐solid‐state electrolyte with a dual thermal insurance mechanism based on the unique structural, designed for the long‐term safe operation of energy devices. The first protection involves microspheres embedded in the matrix and the hydrogel network, which initiate a dual‐linkage effect and accelerate the hydrophilic‐to‐hydrophobic state transition in response to heat accumulation. This process rapidly closes the ion transport channels. Complementing this mechanism, water evaporation further impedes ion migration, forming the second thermal insurance. Due to the thermal reversibility of hydrogel network, the device's initial capacity can be restored upon cooling. Moreover, the regenerative behavior of electrolyte dynamically regulates matrix's water content, ensuring the recovery of ion transport capacity. Theoretical simulations and experiments demonstrate that the designed hydrogel electrolyte offers a broad and tunable temperature protection range. Notably, this thermally reversible protection can be repeated multiple times without compromising electrochemical performance, facilitating autonomous operation. The prepared hydrogels also demonstrate self‐healing capabilities and mechanical flexibility, thereby enhancing the durability of self‐heating protected energy storage devices.