Fe-F Co-doped NaTi2(PO4)3/C anode material for high performance and long-life aqueous Li-ion battery

NASICON-type NaTi2(PO4)3 (NTP) with stable 3D framework exhibits great application prospect as anode materials for aqueous lithium ion battery (ALIB). However, the low electrical conductivity of NTP adversely affects its rate and cycling performance. Surface coating and lattice doping are considered to be effective means to improve the performance of the material. Herein, carbon coated and Fe-F co-doped NTP anode materials were synthesized for ALIBs. It is found that the LiMn2O4||NTP-Fe0.1-F0.1/C full cell delivers a high discharge specific capacity of 112.8, 103.2 and 96.2 mAh g−1 at 0.5, 5 and 10 C, respectively, in the voltage range of 0.5–1.9 V when Ni foam is used as gasket for the cell assembly. The performances of the cell especially the cycling lifetime at high charge-discharge rates are further improved using electrochemically stable stainless steel as gasket. A high coulombic efficiency of 100% and a low capacity decay of only 0.8% at 5 C and 14.9% at 10 C are achieved even after 2000 cycles of charge-discharge test. This is the most stable NTP-based ALIBs reported in the literature. The outstanding electrochemical property and the long cycling lifetime of the NTP-Fe0.1-F0.1/C material is due to the enhanced structural stability and electron/Li+ ion transfer kinetics.