A novel desalination seawater battery (DSWB) has been developed by adapting the design of a rechargeable seawater battery, which operates for both seawater desalination and energy storage. The DSWB system has a unique architecture composed of two subsystems used for desalination and salination during charging and discharging, respectively. A higher energy density (4010 Wh/kg) can be achieved at high nominal cell potential (EO = 3.46 V, pH 8.4) in the DSWB system throughout the charging (desalination) process which is much larger than those of any reported desalination battery system (< 78 Wh/kg and <1.25 V). In addition, the system provides a compartment for desalination, which is independent from the salination (discharging) process, enabling the salination process to be carried out without renewing the seawater for every step, which enables the proposed system to achieve high levels of seawater desalination (up to 84%). The results affirm that further optimization of the cell system will facilitate economical and practical desalination battery applications with high energy density.