Effect of the N,S-Codoped Carbon Layer on the Rate Performance of Air-Stable Lithium Iron Oxide Prelithiation Additives

Lithium iron oxide (Li5FeO4, LFO) holds great promise in cathode prelithiation additives for lithium-ion batteries. However, it is hard to make full use of the power under high current rates due to its poor air stability and electronic conductivity. The carbon protective layer is an effective approach, and introducing heteroatoms would be beneficial to further improving Li+ kinetics. However, the interplay between the dopants and Li+ is always ignored. Herein, we aim to reveal the interaction among Li+ ions and the defects of carbon layers from nitrogen/sulfur dopants and the corresponding influence on delithiation performances of LFO. It is found that the codoping of nitrogen and sulfur on carbon layers contributes to the boosted capacity and rate capability. The modified SNC@LFO presents a large irreversible capacity (779.3 mAh g–1 at 0.1 C) and excellent rate performance (537.1 mAh g–1 at 1 C), which is up to 16.6 and 64.0%, respectively, compared to LFO.