Ion transport mechanism in sodium-ion batteries: Fundamentals, applications, and future trends

In this review, the mechanisms of ion transport in sodium-ion batteries (SIBs) are described based on the increase in the demand for long-term energy storage systems worldwide. The research is placed within the context of renewable energy to stress the need for SIBs as putative large-scale energy storage candidates by discussing the mechanisms of ion diffusion, migration, and conductivity in different battery components. However, several challenges remain regarding SIBs, including the ability to achieve fine control of ion transport pathways that can significantly influence improved rate capability, stability, and energy density of batteries. This review conducts an information search, reviews literature on the fundamentals, analyzes material consequences, evaluates applications and outcomes, and considers future trends. Based on this synthesis, this review highlights certain areas of concern and precise research opportunities and requirements for the next steps toward overcoming current constraints for cathode and anode materials, solid electrolytes, and interfacial processes. These insights underscore the complex interplay of the knowledge base, emerging material, and probing activities that are critical in enhancing the technology of SIB and gaining more energy solutions.