Hybrid Electrolytes for Next-Generation Electrochemical Energy Storage: A Review and Perspectives

Hybrid electrolytes are needed for next-generation electrochemical energy storage because they offer significant advantages over conventional electrolytes. Although conventional electrolytes are widely used in electrochemical energy storage devices, they face several persistent challenges including limited electrochemical stability, flammability, and poor compatibility with high-performance electrodes. Consequently, hybrid electrolytes, including blends of aqueous, organic, ionic-liquid, and gel-based systems, have emerged as viable alternatives. By integrating the complementary advantages of different electrolyte classes, hybrid electrolytes offer a promising pathway toward enabling safer, more stable, and higher-performance next-generation energy-storage systems. However, each hybrid approach entails trade-offs. Enhancing stability often increases viscosity or cost, and raising conductivity can come at the expense of safety. In this critical review, we comprehensively assess the physicochemical and electrochemical characteristics of hybrid electrolytes, examining key parameters such as ionic conductivity, viscosity, electrochemical stability window, and thermal behavior through recent literature and experimental insights. By synthesizing emerging trends and contradictions, we compare how aqueous–organic, ionic liquid-organic, and gel-based hybrid systems navigate the trade-offs between conductivity, stability, and safety. Furthermore, the compatibility between electrolytes and electrodes is critically examined through insights into the electrode–electrolyte interphase (EEI) and the solvation structure of electrolytes, which govern interfacial stability and overall electrochemical performance. This review also outlines the challenges associated with hybrid electrolyte development and highlights future research directions to facilitate their commercial viability. By offering a balanced perspective on performance, safety, and sustainability, this work highlights the emerging potential of hybrid electrolytes in revolutionizing energy storage technologies.