Heterointerface magic: How FeS₂/NiS₂@NC nanoparticles transform sodium-ion battery anode performance

Transition metal sulfides (TMS) are acknowledged as potential anode materials for sodium ion batteries (SIBs); however, their practical application is significantly hindered by suboptimal cycling durability and inadequate rate performance, primarily stemming from limited electronic conductivity and substantial volume swelling during the sodiation/desodiation process. Constructing heterojunction incorporating multiple active components has been emerged as an effective strategy to mitigate these limitations. In this study, high lattice matching FeS₂/NiS₂ heterojunction nanoparticles anchored on a carbon skeleton (FeS₂/NiS₂@NC) were synthesized by a facile high-temperature pyrolysis and sulfidation process. The combination of experimental characteristics and theoretical simulations confirms that this unique heterojunction, characterized by an electric field at the interface, offers an adjustable electronic structure and strong Na⁺ adsorption energy, thus expediting Na⁺ diffusion kinetics. Consequently, the FeS₂/NiS₂@NC electrode demonstrates superior rate capabilities (491.2 mAh/g at 10.0 A/g) and enhanced cycling stability (490.8 and 274.7 mAh/g at 10.0 and 20.0 A/g over 5000 cycles) when employed as anode in SIBs. This research underscores the pivotal role of the heterointerface engineering in enhancing rechargeable battery performance and presents a promising avenue for optimizing the electrochemical properties of TMS.