A novel aqueous rechargeable dual-ion battery system is demonstrated in this study, which consists of BiF3 as a fluoride ion electrochemical anode, NMO as a sodium ion electrochemical cathode, and aqueous NaF as the electrolyte.

Both freshwater shortage and energy crisis are global issues. Herein, we present a double-function system of faradaic desalination and a redox flow battery consisting of VCl3|NaI redox flow electrodes and a feed stream. The system has a nominal cell potential (E0 = +0.79 V). During the discharge process, the salt ions in the feed are extracted by the redox reaction of the flow electrodes, which is indicated by salt removal. Stable and reversible salt removal capacity and electricity can be achieved up to 30 cycles. The energy consumption is as low as 10.27 kJ mol-1 salt. The energy efficiency is as high as 50% in the current aqueous redox flow battery. With energy recovery, the desalination energy consumption decreases greatly to 5.38 kJ mol-1; this is the lowest reported value to date. This "redox flow battery desalination generator" can be operated in a voltage range of 0.3-1.1 V. Our research provides a novel method for obtaining energy-saving desalination and redox flow batteries.

Chloride-ion battery is considered as the promising electrochemical system due to its high energy density in theory. However, aqueous chloride-ion redox materials are limitedly reported owing to their instability or dissolution in aqueous electrolyte. Here, we synthetize a new electrochemical chloride-ion material, Sb 4 O 5 Cl 2 , investigate its electrochemical performance in aqueous NaCl electrolyte, and assemble into aqueous chloride-ion battery with silver as cathode. During the battery charge process, Sb 4 O 5 Cl 2 anode electrochemically releases chloride ions, which are captured by Ag cathode with the formation of silver chloride while the discharging reverses the process. The battery demonstrates favorable electrochemical performance. With current density of 600 mA g −1 , the battery discharge capacity of 34.6 mAh g −1 can be maintained for 50 cycles. This work is greatly significant for the development of anion electrochemical energy storage. KEYWORDS: chloride-ion battery, Sb 4 O 5 Cl 2 , energy storage device, chloride-ion electrochemistry, aqueous battery