Solvent-free fabrication of freestanding inorganic solid electrolyte membranes: Challenges, progress, and perspectives

All-solid-state Li batteries (ASSBs) have become the frontrunner in the search for a better safety and stable energy storage systems that possess remarkable energy and power density. Until now, research on inorganic solid electrolytes (SEs) has primarily aimed to enhance interfacial stability and boost ionic conductivity. However, the importance of electrolyte thickness in ASSB's electrochemical performance and energy density has been relatively overlooked. The slurry processing is a primary method used in the preparation of thin inorganic SE. This method has drawbacks including the use of harmful organic solvents and significant energy for solvent evaporation and recovery. Recognizing this, our review assesses studies that go beyond the conventional casting method and focuses on the solvent-free fabrication of inorganic SE membranes. Implementing a solvent-free method in the fabrication of inorganic SE membranes affords an eco-friendly manufacturing process. Furthermore, a thinner membrane, which can be fabricated using this method, is highly advantageous for constructing high-energy ASSBs. An overview of inorganic SE membranes fabrication using the solvent-free approach is given in this review. We systematically discuss the employed methods to manufacture inorganic SE membranes using solvent-free approach and highlight the required polymeric binders. Then, we provide recent advances and challenges of solvent-free fabrication of inorganic SE membranes followed by future perspectives.