The concept, structure, and progress of seawater metal-air batteries

Seawater metal-air batteries (SMABs) are promising energy storage technologies for their advantages of high energy density, intrinsic safety, and low cost. However, the presence of such chloride ions complex components in seawater inevitably has complex effects on the air electrode process, including oxygen reduction and oxygen evolution reactions (ORR and OER), which requires the development of highly-active chloride-resistant electrocatalysts. In this review, we first summarized the developing status of various types of SMABs, explaining their working principle and comparing the battery performance. Then, the reported chlorine-resistant electrocatalysts were classified. The composition and structural design strategies of high-efficient chlorineresistant ORR/OER electrocatalysts in seawater electrolytes were comprehensively summarized. Finally, the main challenges to be overcome in the commercialization of SMABs were discussed.