Progress and Applications of Seawater-Activated Batteries

Obtaining energy from renewable natural resources has attracted substantial attention owing to their abundance and sustainability. Seawater is a naturally available, abundant, and renewable resource that covers >70% of the Earth’s surface. Reserve batteries may be activated by using seawater as a source of electrolytes. These batteries are very safe and offer a high power density, stable discharge voltage, high specific energy, and long dry storage life and are widely used in marine exploration instruments, life-saving equipment, and underwater weaponry. This review provides a comprehensive introduction to seawater-activated batteries. Here, we classify seawater-activated batteries into metal semi-fuel, high-power, and rechargeable batteries according to the different functions of seawater within them. The working principles and characteristics of these batteries are then introduced, and we describe their research statuses and practical applications. Finally, we provide an outlook on the development of seawater-activated batteries and highlight practical issues to drive further progress.