Abstract
The development of solid-state electrolytes (SSEs) is critical for realizing high-energy-density lithium metal batteries (LMBs) with enhanced safety. This review systematically analyzes rational design strategies for SSEs, encompassing inorganic, polymer, and composite systems. We evaluate key performance metrics including ionic conductivity, mechanical stability, and interfacial compatibility with lithium metal anodes. A comprehensive literature analysis from 2013 to 2023 identifies critical design parameters such as grain boundary engineering, polymer matrix modification, and additive incorporation. Our findings reveal that composite SSEs integrating garnet-type ceramics with poly(ethylene oxide) achieve ionic conductivities exceeding 10⁻⁴ S cm⁻¹ at 60°C while suppressing dendrite growth. Additionally, we propose a unified framework correlating mechanical properties with electrochemical stability. The results underscore the importance of interfacial engineering and multi-scale design for practical applications. This work provides actionable guidelines for next-generation SSE development, targeting energy densities above 500 Wh kg⁻¹.