Hierarchical interlayer-expanded MoSe2/N–C nanorods for high-rate and long-life sodium and potassium-ion batteries

Abstract

Sodium and potassium ion batteries have attracted considerable attention in the last few years owing to abundant resources of sodium and potassium compared to those of lithium. Transition metal dichalcogenide MoSe₂ shows great potential as an anode because of its high achievable capacity. However, the sluggish kinetics, large volume expansion and pulverization of MoSe₂ result in severe decay of sodium or potassium storage performance. In this work, a hierarchical MoSe₂/N–C nanorod is synthesized with expanded interlayer spacing. Ethylenediamine (EDA) in MoO₃·EDA precursor plays an important role in obtaining the hierarchical nanorod structure. The insertion of C and N into the interlayer of the MoSe₂ results in the enlarged interlayer spacing, which is derived from the carbonization of EDA. The expanded d-spacing of (002) planes enhances the diffusion kinetics of Na⁺ and K⁺ ions. The hierarchical structure and the N-doped carbon coating buffer the volume expansion during the charging/discharging process maintaining the structural integrity of MoSe₂. As a result, MoSe₂/N–C exhibits long cycle performance and high rate capability for both sodium and potassium storage.