Recent Developments in Solid-State Electrolytes for Advanced Energy Storage Devices

The quest for efficient energy storage solutions has intensified in recent years, driven by the growing demand for portable electronic devices, electric vehicles (EVs), and renewable energy systems. Solid-state electrolytes (SSEs) have emerged as a promising alternative to traditional liquid electrolytes in batteries and supercapacitors for next-generation energy storage systems. They offer many advantages, including enhanced safety, superior thermal stability, and compatibility with high-energy-density electrodes, such as lithium metal. Unlike conventional liquid electrolytes that depend on solvent-based ion transport, SSEs enable ion migration through well-defined crystalline, amorphous, or polymeric matrices, effectively mitigating detrimental issues such as leakage, flammability, and dendrite formation. This article offers a critical review of the latest emerging trends in SSEs for Li-ion batteries and other energy storage systems. First, it examines different material systems and designs, namely ceramic-based, polymer-based, and composite electrolytes, and their key properties, like ionic conductivities and mechanical properties. Second, it assesses the ion transfer mechanisms of the different systems and the key factors influencing their ion conductivity, such as temperature, composition, and microstructure of solid electrolytes, and solid electrolyte-electrode interphase, along with the strategies developed to enhance it. Next, recent applications of SSEs in different energy storage devices, including Li-ion batteries, Na-ion batteries, load-bearing structural batteries, and supercapacitors, are identified. Finally, the article discusses current article discusses current challenges and future research directions for SSEs to unlock their full potential in applications ranging from EVs and grid-scale storage to flexible and wearable electronics.