A MnS/FeS2 heterostructure with a high degree of lattice matching anchored into carbon skeleton for ultra-stable sodium-ion storage

Abstract

Combining two different compounds into a heterostructure recently emerged as an auspicious strategy to mitigate the issues associated with the sluggish sodium diffusion kinetics of anode materials. Nevertheless, studies relating to as-designed heterostructures, so far, have not considered the matching of crystal structures between different compounds. In this work, a heterostructure between MnS and FeS₂, featuring identical cubic systems and close lattice parameters, confined in one-dimensional carbon nanofibers was synthesized through electrospinning technology (denoted as MnS/FeS₂@CNFs). An internal built-in electric field is generated at the interface of the heterostructure owing to differences in the bandgaps of the two compounds, and this is conducive to accelerating the Na⁺ diffusion kinetics and enhancing charge transport. Meanwhile, the one-dimensional carbon skeleton can effectively alleviate volume variations and prevent the aggregation of active material during the sodium storage process. As expected, the MnS/FeS₂@CNFs composite delivered good rate performance (322.3 mA h g⁻¹ at 10.0 A g⁻¹) and excellent cycling durability (194.0 mA h g⁻¹ at 10.0 A g⁻¹ over 3600 cycles). In line with DFT calculations, the constructed heterojunction with a small mismatch of ∼3.9% can effectively enhance the electronic conductivity of the composite, thereby accelerating charge transfer. This work can help the development of rational design strategies for heterostructures and provide an in-depth understanding of the functions of heterostructures in the energy-storage field.