Recent Progress of the Crystalline Organic Electrolytes for Solid-State Battery Applications

Crystalline organic electrolytes (COEs) have recently emerged as promising alternatives to conventional solid-state electrolytes, including oxide, sulfide, and polymeric electrolytes. This interest arises from the limitations of traditional solid-state electrolytes, which often suffer from inadequate ionic conductivity, poor electrochemical stability, and difficulty in establishing intimate contact with cathode particles. In this review, COEs are introduced with a focus on their classification, unique characteristics, and case studies highlighting their application in solid-state batteries. COEs are fundamentally composed of alkali metal salts and organic crystalline solvents. Based on the type of solvent, they are classified into three categories: organic ionic plastic crystal electrolytes (OIPCs), non-ionic plastic crystal electrolytes (NIPCs), and non-plastic crystal organic electrolytes (NOPCs). COEs offer several advantageous properties, including high ionic conductivity, low-to-negligible flammability, and excellent compatibility with electrodes achieved through meltcasting processes. These features position COEs as a transformative solution for advancing solid-state battery technologies, enabling the development of safe, high-performance, and energy-dense devices for electrified applications.