Synergistic Intercalation and Vacancy Engineering Boosting Superior Rate Performance for High-Performance Potassium Storage

Abstract In this work, a dual-strategy approach of Ti-intercalation and Mo vacancies was utilized to engineer VMo-Ti-MoSe2, aiming to enhance the electrochemical performance of potassium-ion batteries (PIBs). The intercalation strategy reduces the band gap and expands the layer spacing of MoSe2, which alleviates the volume expansion during potassiation/depotassiation processes and accelerates the rapid migration of potassium ions. Furthermore, the engineered Mo vacancies not only facilitate the excitation and conduction of electrons but also significantly accelerate carrier transfer, thereby enhancing the reaction kinetics during the charge/discharge process. Additionally, these vacancies provide abundant active sites that ensure a more stable and superior potassium ion adsorption capability. More importantly, in-situ X-ray diffraction and in-situ Raman spectroscopy, coupled with density functional theory calculations, elucidate the potassification/depotassification behaviors of VMo-Ti-MoSe2 anode during the cycling process. Consequently, VMo-Ti-MoSe2 anode demonstrates an outstanding cycling performance, retaining of 360.1 mAh g-1 after 100 cycles at 2 A g-1. It also delivers a high rate capability of 270.9 mAh g-1 at 5 A g-1. This study shows that vacancy and intercalation strategies significantly enhance the electrochemical performance of PIBs and may be applicable to other battery systems to achieve higher capacity and better cycling stability.