Development and characterization of aqueous sodium-ion hybrid supercapacitor based on NaTi2(PO4)3//activated carbon

In this work, for the first time, the sodium ion intercalated compound NaTi2(PO4)(3) has been designed to function as the anode in combination with activated carbon as the cathode to develop a novel aqueous sodium-ion hybrid supercapacitor based on the Na2SO4 aqueous electrolyte. Both anode and cathode have been fabricated with a thick (>1 mm) freestanding structure. The as-proposed NaTi2(PO4)(3)//activated carbon hybrid supercapacitor exhibits a typical supercapacitor-battery behavior. During the galvanostatic charging and discharging process, a linear sloping voltage range from 0 to 0.8 V corresponding to supercapacitor has been observed and an obvious voltage plateau in the range of 0.8-1.6 V could be related with the battery characterization. The hybrid supercapacitor thus brings a much high energy density over conventional supercapacitor based on activated carbon electrode. The NaTi2(PO4)(3)//activated carbon system shows a discharge capacity of 27.5 mAh g(-1) with an average working voltage of 1.15 V, corresponding to a high energy density of 31.6 Wh kg(-1) at a power density of 23 W kg(-1) based on the total weight of active electrode materials. It also exhibits excellent cycling behavior with less than 11.7% capacitance loss after 2000 cycles at current density of 200 mA g(-1). The cell delivers a relatively high power ability of 420 W kg(-1) with the energy density of 15.5 Wh kg(-1). (C) 2017 Published by Elsevier B.V.