In-situ induced sulfur vacancy from phosphorus doping in FeS2 microflowers for high-efficiency lithium storage

In this work, via in-situ induction of phosphorus doping, FeS2 microflowers with sulfur vacancies were rationally designed and fabricated for lithium-ion batteries (LIBs). Phosphorus doping enlarged interlayer spacings, effectively enhanced the conductivity and facilitated the diffusion and intercalation/deintercalation of Li+. Moreover, the in-situ induced sulfur vacancies also partly rearranged electronic structures and increased more active adsorption sites for Li+. The P1.0-FeS2-x electrode delivered the excellent rate performance (642.6 mAh/g at 5.0 A/g) and long-cyclic performance (544.7 mAh g-1 at 2.0 A/g after 1000 cycles). X-ray absorption fine structure spectroscopy was employed to reveal the decrease of Fe oxidation state and coordination number, confirming sulfur vacancies were in-situ induced through phosphorus doping process. Density function theory calculation declared the doping of phosphorus atoms and in-situ induced sulfur vacancies in FeS2 could effectively adjust the charge distribution at the active sites for Li adsorption, which enhanced the conductivities and facilitated the electrochemical reaction kinetics. The anionic doping strategy may provide new ideas and routes of constructing transition metal sulfides for high-performance LIBs.