High ceramic content composite solid-state electrolyte films prepared via a scalable solvent-free process

The development of high-performance solid-state electrolyte (SSE) films is critical to the practical application of all-solid-state Li metal batteries (ASSLMBs). However, developing high-performance free-standing electrolyte films remains a challenging task. In this work, we demonstrate a novel scalable solvent-free process for fabricating high ceramic content composite solid-state electrolyte (HCCSE) films. Specifically speaking, a mixture of ceramic and polymer is dry mixed, fibered, and calendered into a free-standing porous ceramic film, on which polymer precursor is coated and polymerized to bridge the inorganic ceramic particles, resulting in a flexible HCCSE film with a ceramic content of up to 80 wt.%. High ceramic content not only leads to high ionic conductivity but also brings good mechanical properties; while the organic phase enables electrode|electrolyte interfacial stability. When Li₁₀GeP₂S₁₂ (LGPS) and polymeric ionic liquid-based solid polymer electrolytes (PIL-SPEs) were used as the inorganic and organic phases, respectively, the room temperature ionic conductivity of the resulted HCCSE reaches 0.91 mS·cm⁻¹. Based on this HCCSE, Li||Li symmetric battery cycled stably for more than 2,400 h with ultra-low overpotential, and ASSLMBs with different cathodes (LiFePO₄ and sulfurized polyacrylonitrile (PAN-S)) present small polarization and decent cyclability at room temperature. This work provides a novel scalable solvent-free strategy for preparing high-performance free-standing composite solid-state electrolyte (CSE) film for room temperature ASSLMBs.