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.