Self-Healing polymer electrolytes driven by dynamic bonds: molecular structure design and characterization analysis

Since the commercialization of lithium-ion batteries in the 1990s, they have become indispensable in modern life, having been seamlessly integrated into nearly all aspects of social and economic development. However, currently, commercialized liquid electrolytes (LEs) suffer from inherent drawbacks, such as poor thermal stability, leakage tendencies, and flammability, posing serious safety risks when used in batteries. Solid polymer electrolytes (SPEs) possess excellent safety (including nonflammable, leakage-proof, and dendrite inhibition properties) and can achieve high energy densities. They are expected to replace LEs and become an important candidate for the next generation of high-safety and -energy density battery technologies. However, the polymer matrix of conventional SPEs often does not have sufficient strength to withstand external mechanical impact or prolonged stress, making conventional SPEs susceptible to mechanical damage and crack formation, which compromises the overall performance of batteries. Furthermore, traditional SPEs generally cannot self-repair after damage, shortening the lifespan of batteries and increasing maintenance costs. Consequently, SPEs must possess self-healing capabilities to address these challenges. Further research on self-healing polymer electrolytes (SHPEs) can alleviate the scarcity of resources and improve the sustainability of current energy storage technologies.Currently, considerable progress has been made in SHPEs with autonomous repair capabilities. To effectively introduce the self-healing function in a specific polymer electrolyte system, it is crucial to comprehensively understand self-repair mechanisms. SHPEs can achieve self-repair properties via the incorporation of reversible dynamic bonds. Their healing mechanisms primarily rely on the reversible dissociation and recombination of these dynamic bonds under external stimuli (e.g., thermal field, light radiation, or mechanical stress), enabling autonomous restoration at damage sites. According to the literature, such dynamic bond-driven self-healing materials can restore their original structural integrity during the microcrack nucleation stage via bond recoordination and can also effectively maintain the ion transport pathway continuity, ensuring superior ionic conductivity. More importantly, the exchange reactions of dynamic bonds considerably promote the coordinated movement of polymer chains, substantially improving the mechanical flexibility of SHPEs while optimizing the chemical compatibility and physical interface contact at the electrode–electrolyte interface. Based on the physicochemical properties of dynamic bonds, self-healing mechanisms can be divided into two major categories, i.e., self-healing based on dynamic covalent bonds (e.g., disulfide bonds, borate ester bonds, imine bonds, and Diels-Alder reactions) and self-healing based on dynamic noncovalent bonds (e.g., hydrogen bonds, metal coordinations, and ion interactions). However, maintaining a delicate balance between the self-healing capability, mechanical strength, and ionic conductivity of SHPEs using different dynamic bonds remains challenging. A single dynamic bond system often faces a trade-off between mechanical strength and self-healing efficiency, while the synergistic effect of multiple dynamic bonds can overcome the performance limit of single dynamic bond systems. Additionally, the visualization of the self-repair process and chemical structural analysis of dynamic bonds are essential for designing and optimizing SHPEs.This review systematically summarizes molecular structural design strategies and advanced characterization techniques for dynamic bond-driven polymer electrolytes. First, the repair mechanisms and applications of covalent and noncovalent dynamic bonds in solid-state electrolytes based on their physicochemical nature are discussed. Second, considering the limitations of a single dynamic bond system, the regulation of the mechanical properties and self-repair efficiency of SHPEs via the synergistic effect of multiple dynamic bonds is discussed. Finally, advanced characterization techniques that can be used for investigating self-healing mechanisms are highlighted, providing multiscale research perspectives for understanding dynamic bond repair processes. Through multiscale optimization, dynamic bond-driven SHPEs may promote the development of the next generation of high-performance and long-life energy storage devices.