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.