Self-healable gels in electrochemical energy storage devices

In the green energy and carbon-neutral technology, electrochemical energy storage devices have received continuously increasing attention recently. However, due to the unavoidable volume expansion/shrinkage of key materials or irreversible mechanical damages during application, the stability of energy storage and delivery as well as the lifetime of these devices are severely shortened, leading to serious performance degradation or even safety issues. Therefore, the utilization of self-healable gels into electrochemical energy storage devices, such as electrodes, binders, and electrolytes, is proven as an effective method to realize long-term stable operation of these devices via the self-repairing of mechanical and electrochemical characteristics. Herein, this review first summarizes the feature and fabrication of different gels, paying special attention to hydrogels, organohydrogels, and ionogels. Then, basic concepts and figure of merit of self-healable gels are analyzed with a detailed discussion at the healing mechanisms, from reversible dynamic bonds to physical molecular diffusion, and to external healing trigger. Then we introduce all the important parts of electrochemical energy storage devices, which could be replaced by healable gels to enhance the durability, including electrodes, binders, and electrolytes. Finally, the critical challenges and future perspectives regarding the future development of healable gels based high-performance electrochemical energy storage devices or electronics are provided.