Rechargeable seawater batteries (SWBs) using seawater as a catholyte have attracted extensive attention owing to the ocean's high theoretical energy density (3051 Wh L‐1, 3145 Wh kg‐1) and excellent thermal management. However, despite many improvements in materials and cell designs used in SWBs so far, there is a limit on the energy density in practical use, because of the lack of optimization of the cell structure. Herein, this work introduces a novel design by applying a rigid frame with an extended space called “prismatic‐type.” Consequently, an energy density of 23 Wh (242 Wh L‐1) is obtained by increasing the specific area of the unit cell and the capability of the anode active materials in the internal space. In addition, it enables the design of a discrete type that can improve the power density by increasing the surface area of the cathode current collectors. With the increased surface area, a peak power of 1162 mW is achieved for the discrete type compared to 727 mW for the integral type. These results suggest that these newly designed prismatic SWBs could contribute to practical applications in the near future.
Seawater batteries (SWBs) are a type of sodium-air batteries that use abundant seawater as the source of the catholyte. A cathode current collector in traditional SWBs is composed of titanium (Ti) and carbon-based current collectors. The high contact resistance between Ti and carbon-based current collectors as well as the slow kinetics of oxygen evolution and reduction reactions increase the overpotential, resulting in side reactions such as carbon corrosion. To enhance the performance of SWBs, previous studies have focused on carbon current collectors, catalysts, and polymer binders, while ignoring the importance of Ti. In this study, a facile carbon diffusion technique is employed to successfully form titanium carbide (TiC) on the surface of Ti. SWBs with engineered Ti demonstrate considerably improved performance (four times higher cycling stability, 30% increased power performance, 40% reduced voltage gap) in relation to those with pristine Ti. This significantly improved electrochemical performance is found to be attributable to the prevention of carbon corrosion due to i) the reduction of contact resistance (owing to rough TiC surface) and ii) the electrocatalytic effect of TiC. Finally, engineered Ti is applied to large-area SWBs and its potential applicability in energy storage systems is confirmed.
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