Effect of Concentrated Electrolyte on Aqueous Sodium-ion Battery with Sodium Manganese Hexacyanoferrate Cathode

Abstract

From the viewpoint of the cost and safety, aqueous sodium-ion batteries are attractive candidate for large-scale energy storage. Although the operating voltage range of the aqueous battery is theoretically limited to 1.23 V by the electrochemical decomposition of water, the voltage restriction is a little bit eased in real aqueous battery system by the charge/discharge overvoltage. Effect of the concentrated electrolyte on the operation voltage was studied in aqueous Na-ion battery with Na 2 MnFe(CN) 6 hexacyanoferrates cathode and NaTi 2 (PO 4 ) 3 NASICON-type anode, in order to increase the discharge voltage. According to the cyclic voltammetry, the electrochemical window of diluted 1 mol kg −1 NaClO 4 aqueous electrolyte is only 1.9 V, whereas the corresponding electrochemical window of concentrated 17 mol kg −1 NaClO 4 aqueous electrolyte is widen to 2.8 V. This wide electrochemical window of the concentrated aqueous electrolyte allows the Na 2 MnFe(CN) 6 //NaTi 2 (PO 4 ) 3 aqueous sodium-ion system to work reversibly. By contrast, the framework of Na 2 MnFe(CN) 6 cathode was destroyed by the hydroxide anion generated in diluted 1 mol kg −1 electrolyte.

Water in Rechargeable Multivalent‐Ion Batteries: An Electrochemical Pandora's Box

“…Bulk water has an electrochemical stability window of about 1.23 V. Recently, however, reports of high‐voltage aqueous batteries (2.5 to 4 V) have claimed the successful use of interfacial controls to isolate bulk water from electrochemical contact ,,. This was achieved through the creation of an artificial solid–electrolyte interface (SEI) on the electrode surface, which passivates against proton/hydroxyl electrolytic decomposition, but allows cation‐specific diffusion.…”

High‐Efficiency Na‐Storage Performance of a Nickel‐Based Ferricyanide Cathode in High‐Concentration Electrolytes for Aqueous Sodium‐Ion Batteries

“…Previous studies have demonstrated that electrolyte concentration is an important factor affecting the electrochemical properties . Designing high‐concentration electrolytes can largely improve the Coulombic efficiency and cycling stability of electrode materials as the high concentrations of electrolyte salts decrease the activity of electrolyte solvents.…”

Nickel‐Substituted Copper Hexacyanoferrate as a Superior Cathode for Aqueous Sodium‐Ion Batteries

“…On the other hand, designing high‐concentration electrolytes can enhance the electrochemical properties of Prussian‐blue analogues owing to suppression of side reactions with electrolytes. As reported, the electrochemical stability window of concentrated NaClO 4 electrolyte (17 mol Kg −1 ) can be widen to 2.8 V, which enables aqueous Na 2 MnFe(CN) 6 /NaTi 2 (PO 4 ) 3 battery working reversibly . The NaClO 4 electrolyte with concentrations of more than 6 M can achieve high‐efficiency Na‐storage performance of nickel‐based hexacyanoferrates .…”