Ultrahigh-Desalination-Capacity Dual-Ion Electrochemical Deionization Device Based on Na3V2(PO4)(3)@C-AgCl Electrodes

Seawater desalination is a promising way to alleviate water scarcity nowadays. Present capacitive desalination methods have limitation of salt removal capacity. Herein, a new dual-ion electrochemical desalination system with an ultrahigh desalination capacity is reported. It is composed of Na3V2(PO4)(3)@C wires as a sodium ion Faradaic electrode, AgCl as a chloride ion Faradaic electrode, and salt feed solution as the electrolyte. When a constant current is applied, redox reactions occur on electrodes, releasing or removing sodium ions and chloride ions. Na3V2(PO4)(3) has a high sodium specific capacity, and as a sodium superionic conductor, Na3V2(PO4)(3)@C wires form an ion conductor network, providing high sodium ion mobility. Additionally, both the wire structure and carbon shell enhance the electrical conductivity of Na3V2(PO4)(3). Benefiting from these, outstanding desalination performance, rate capability, and cycle capability have been achieved with the Na3V2(PO4)(3)@C wire-AgCl device. An ultrahigh desalination capacity of 98.0 mg/g is obtained at a current density of 100 mA/g for more than 50 cycles. This system provides a viable dual-ion electrochemical desalination strategy, which outperforms most of the existing desalination methods.