Superior high-rate and cycle performances of a single-phase ferrous orthophosphate Na1.2Fe4(PO4)3 anode material for lithium-ion batteries

The development of low-cost and eco-friendly electrode materials is crucial for the next-generation rechargeable lithium-ion batteries (LIBs). Herein, the single-phase Na 1.2 Fe 4 (PO 4 ) 3 (NFP) with a monoclinic NaCo 4 (PO 4 ) 3 -type structure is demonstrated to be a suitable anode material for LIBs. The NFP anode exhibits superior high-rate performance, releasing an initial charge capacity of 128.6 mAh g −1 at 10C and a high-capacity retention rate of 86.7% over 1500 cycles. The prominent rate performance and cycling stability of the NFP anode are attributed to the stable single-phase crystal structure and fast Li-ion diffusion verified by galvanostatic intermittent titration technique (GITT). Furthermore, the structure evolution and Li-ion diffusion pathway of the NFP anode are clarified by ex-situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and first-principles calculations.