Electrochemical Driven Phase Segregation Enabled Dual-Ion Removal Battery Deionization Electrode

Battery deionization (BDI) offers a powerful platform for integrating water treatment and energy conversion. Exploring novel BDI electrode materials with high energy storage capacity and high efficiency for both cations and anions removal is the key to advancing the BDI technique. Herein, we report the first BDI electrode material capable of simultaneously removing Cl– (58.4 mg g–1) and Na+ (8.7 mg g–1) in water with a reversible capacity of 160 mAh g–1. In situ powder X-ray diffraction (PXRD) unravels that the dual-ion removal capability is attributed to a novel reversible electrochemical driven phase segregation reaction mechanism between NaBi3O4Cl2 and the in situ formed metallic Bi. The unique dual-ion storage capability demonstrated with the NaBi3O4Cl2 electrode indicates that exploring electrochemical reversible phase segregation electrode material holds great promise for advancing the BDI electrode for future desalination techniques and aqueous rechargeable battery systems.