Boosting the intercalation reaction of FeOF-based cathode toward highly reversible lithium storage

Abstract

FeOF as an intercalation-conversion cathode features a high theoretical capacity toward high energy density lithium-ion batteries (LIBs). However, the inadequate intercalation process and poor reversibility of redox reaction deteriorate its practical capacity and cycling stability. Herein, a S-substitution strategy in FeOF (FeOF-S) is proposed to boost the intercalation reaction and enhance the reaction kinetics, achieving a record-high capacity of 668 mAh g⁻¹ at 0.05 A g⁻¹ and a long cycling stability up to 1500 cycles at 0.5 A g⁻¹. Under this strategy, the Li⁺ intercalation energy of FeOF-S is remarkably reduced in thermodynamics, promoting the intercalation capacity to 230 mAh g⁻¹ which is 50% higher than that of FeOF. Furthermore, a nearly zero band gap with superior electronic conduction is achieved in FeOF-S, leading to excellent rate capability with much enhanced pseudo-capacitance contribution. This work presents new insights into the regulation of thermodynamics and kinetics toward the boosted electrochemical performance of conversion-type electrodes for high energy density LIBs.