High-performance aqueous sodium-ion battery using a hybrid electrolyte with a wide electrochemical stability window

The practical application of aqueous sodium-ion batteries (ASIBs) is limited by the electrolysis of water, which results in a low working voltage and energy density of ASIBs. Here, a NaClO4-based acetonitrile/water hybrid electrolyte (NaClO4(H2O)(2)AN(2.4)) is applied to ASIBs for the first time, which effectively extends the electrochemical stability window (ESW) to 3.0 V and reduces the internal resistance of the battery. Based on this hybrid electrolyte, an ASIB full cell using carbon coated Na2.85K0.15V2(PO4)(3)and NaTi2(PO4)(3)as the cathode and anode materials, respectively, can afford a discharge capacity and energy density of 52 mA h g(-1)and 51 W h kg(-1), respectively, at a current density of 1 A g(-1). The energy density of this battery exceeds almost all reported traditional ASIBs.