Highly Stable Na3Fe2(PO4)3@Hard Carbon Sodium-Ion Full Cell for Low-Cost Energy Storage

Abundant flake-porous Na3Fe2(PO4)(3) has been prepared via a simple spray drying method. As a cathode material in sodium-ion batteries (SIBs), the galvanostatic charge/discharge test results indicate that the initial reversible discharge specific capacity of the flake-porous Na3Fe2(PO4)(3) electrode can reach to 100.8 mAh g(-1) (about 93% of the theoretical capacity of 105 mAh g(-1)) under a current density of 10 mA g(-1) (0.1 C) and the high rate capability at 500 mA g(-1) (5 C) is up to 60 mAh g(-1) after 1100 cycles. The in situ X-ray diffraction pattern and ex situ X-ray photoelectron spectroscopy results indicate that the charge/discharge processes of this cathode material go through a reversible electrochemical reaction of Na3Fe2(PO4)(3)/Na5Fe2(PO4)(3). The outstanding electrochemical performance of Na3Fe2(PO4)(3) is attributed to its [Fe-2(PO4)(3)] "lantern unit" stacked NASICON-type structure and two-dimensional (2D) porous-sheet morphology. The flake-porous Na3Fe2(PO4)(3) cathode with a commercial hard carbon anode full cell shows an energy density of 76 Wh kg(-1) and the maximum power density of up to 760 W kg(-1). The full cell also shows excellent low-temperature performance even at -20 degrees C (40 mAh g(-1) at 100 mA g(-1)). The outstanding electrochemical and low-temperature performances prove that this full cell is an ideal device for large-scale electrical energy storage (EES).