Development and Implementation of Sodium‐Ion Conductive NASICON Ceramic Electrolytes for Seawater‐Based Electrochemical Devices

Seawater‐based electrochemical devices have attracted increasing attention as sustainable energy and resource conversion systems due to the abundance of seawater and their inherent compatibility with marine environments. Among the key enabling components, sodium‐ion conductive ceramic electrolytes, particularly Na super ionic conductor (NASICON)‐structured materials, have emerged as promising alternatives to conventional polymer membranes owing to their high sodium‐ion selectivity and conductivity, as well as their excellent chemical stability and mechanical robustness. The review begins by outlining the stringent requirements for ceramic electrolytes in seawater environments and briefly discusses the limitations of existing materials that necessitate more stable alternatives. A detailed exploration of NASICON follows, focusing on their unique structural and ion‐transport characteristics, as well as their exceptional chemical stability in aqueous media. We then summarize recent advances in performance enhancement of NASICON ceramic electrolytes through composition engineering, doping strategies, microstructural control, as well as new processing techniques. Beyond material fundamentals, the review examines the implementation of these electrolytes in diverse electrochemical devices. We outline the operating principles of primary and secondary seawater batteries. The implementation of NASICON ceramic electrolytes in secondary seawater batteries is then examined, with particular emphasis on long‐term stability. Beyond energy storage, emerging seawater‐based electrochemical systems utilizing NASICON membranes for desalination and chemical production are also introduced, highlighting the versatility of ceramic electrolytes in multifunctional seawater technologies. Finally, remaining challenges and future research directions are discussed to guide further development. This review aims to provide an integrated perspective on the role of NASICON ceramic electrolytes in advancing seawater‐based electrochemical technologies toward practical and sustainable applications.