Interfacial lithium-ion transportation in solid-state batteries: Challenges and prospects

Solid-state lithium-ion batteries (SSBs) have gained widespread attention due to their enhanced safety and energy density over conventional liquid electrolyte systems. However, their practical application is hindered by significant polarization during cycling, primarily caused by increased interface impedance. To address the challenges of slow lithium-ion diffusion, optimizing interfacial kinetics has emerged as a key strategy to improve the electrochemical performance of SSBs. However, the mechanisms behind battery failure, especially interface polarization, are not fully understood and require further investigation. This review explores the origins of interfacial polarization, including poor contact, parasitic reactions, and space charge layer, supported by theoretical calculations, experimental data, and advanced characterizations. Then, the latest progress categorized as in-situ solidification, buffer layer, ionic liquid, solid-state electrolytes modification, artificial solid electrolyte interphases, coating layers, dielectric additives, and piezoelectric additives are summarized to elucidate the underlying mechanisms of Li⁺ transport across interfaces. Finally, the integration of mechanical behavior with outstanding interfacial engineering is emphasized as a key factor for advancing SSBs performance and stability, providing insights for the development of next-generation lithium-based batteries. During the operation of solid-state lithium metal batteries, excessive interfacial impedance is often caused by poor contact, parasitic reactions and space charge layer. This review systematically expounds methods to improve the interfacial Li + transport dynamics, combined with advanced characterizations and research in recent years, and prospects of interfacial Li + engineering are also discussed. • Sluggish interfacial Li + diffusion mechanisms in SSBs are systematically exposed. • The advanced characterizations in Li + diffusion of SSB are summarized. • The current progress for improving the interfacial Li + dynamics are summarized. • SSEs engineering and prospects of various electrolytes are highlighted.