Highly stable Na3Fe2(PO4)3@hard carbon sodium-ion full cell for low-cost energy storage
ACS Sustainable Chemistry and Engineering
American Chemical Society
School of Engineering
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 [Fe2(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 °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).