Robust pseudocapacitive Na+ intercalation induced by MoS2 on active Mo2C current collector interface for high areal capacity sodium-ion batteries

Abstract

Sodium-ion batteries (SIBs) have emerged as compelling alternatives in the realm of electrochemical energy devices, poised to substitute lithium-ion batteries (LIBs). The primary challenge encompasses not only the scarcity of anode materials exhibiting exceptional Na+ storage capacity but also the endeavor to achieve high areal capacity. To address this challenge, a comprehensive strategy is proposed that entails utilizing a highly conductive molybdenum dicarbide (Mo2C) current collector (denoted as CCM) as a supporting scaffold for the bottom-up growth of molybdenum disulfide nanosheets (MoS2, serving as the main active component) (denoted as CCM@MoS2). The CCM improves interfacial bonding with MoS2 nanosheets and offers additional capacity to accommodate the increased Na+ insertion activity. Both theoretical and kinetic analyses reveal that the enhanced Na+ storage properties primarily stem from favorable adsorption energy, reduced diffusion barrier, and intercalation pseudocapacitance due to the strong electronic interfacial interaction between active CCM and MoS2. Hence, the as-prepared optimized CCM@MoS2 electrode exhibits a superior areal capacity of 6.36 mAh cm−2 at 0.4 mA cm−2, excellent rate capability of 1.02 mAh cm−2 at 24 mA cm−2 and long cycle life up to 500 cycles at 4 mA cm−2. Interesting, our as-prepared CCM@MoS2 electrode shows better performance for Na+ storage than Li+ storage at higher current density, affirming the enhanced kinetics in our architecture. This work proposes a rational strategy to enhance the areal capacity and stability of MoS2-based anode for SIBs and beyond.