Integrating Desalination and Energy Storage using a Saltwater-based Hybrid Sodium-ion Supercapacitor

Ever-increasing freshwater scarcity and energy crisis problems require efficient seawater desalination and energy storage technologies; however, each target is generally considered separately. Herein, a hybrid sodium-ion supercapacitor, involving a carbon-coated nano-NaTi₂ (PO₄ )₃ -based battery anode and an activated-carbon-based capacitive cathode, is developed to combine desalination and energy storage in one device. On charge, the supercapacitor removes salt in a flowing saltwater electrolyte through Cl^- electrochemical adsorption at the cathode and Na⁺ intercalation at the anode. Discharge delivers useful electric energy and regenerates the electrodes. This supercapacitor can be used not only for energy storage with promising electrochemical performance (i.e., high power, high efficiency, and long cycle life), but also as a desalination device with desalination capacity of 146.8 mg g^-1 , much higher than most reported capacitive and battery desalination devices. Finally, we demonstrate renewables to usable electric energy and desalted water through combining commercial photovoltaics and this hybrid supercapacitor.