Zinc-Air Battery-Based Desalination Device

Efficiently storing electricity generated from renewable resources and desalinating brackish water are both critical for realizing a sustainable society. Previously reported desalination batteries need to work in alternate desalination/salination modes and also require external energy inputs during desalination. Here, we demonstrate a novel zinc-air battery-based desalination device (ZABD), which can desalinate brackish water and supply energy simultaneously. The ZABD consists of a zinc anode with a flowing ZnCl₂ anolyte stream, a brackish water stream, and an air cathode with a flowing NaCl catholyte stream, separated by an anion-exchange membrane and a cation-exchange membrane, respectively. During the discharging, ions in brackish water move to the anolyte and catholyte, and they return to the feed steam during charging. The ZABD can desalt brackish water from 3000 ppm to the drinking water level at 120.1 ppm in one step and concurrently provide an energy output up to 80.1 kJ mol^-1 under a discharge current density of 0.25 mA cm^-2. Further, the ZABD can be charged/discharged over 20 cycles without significant performance deterioration, demonstrating its reversibility. Moreover, the desalination performances can be adjusted by varying current densities and are also influenced by the initial concentration of salt feeds. Besides, two ZABD devices were connected in series to drive 60 light-emitting diodes during the salt removal process without external power supply over 2000 min. Overall, this ZABD system demonstrates the potential for simultaneous water desalination and energy supply, which is suitable for many urgent situations.