Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) due to the abundant sodium resources, suitable redox potential, and similar charge store mechanism. 

However, the larger diameter of Na ions compared to Li ions makes the sodiation/desodiation process more difficult with a larger volumetric variation of the electrode material, thus leading to poor capacity and cycling stability. Therefore, a rational design of electrode materials is critical for improving the electrochemical performance of SIBs. 

A research group led by Prof. DENG Dehui from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with Prof. ZHANG Jianan from Zhengzhou University, reported a synergetic effect in the atomic-interface of well-constructed 2H-MoS₂/Fe_(SA)-N-C anode assembled with 2H-MoS₂ layer and N-doped carbon-confined Fe atom, which boosts the reversible sodium storage capacity. 

This study was published in Angewandte Chemie International Edition on Feb. 2.

The researchers found that driven by the work function difference at the heterointerface, the electron could transfer from Fe_(SA)-N-C to 2H-MoS₂ easily, enhancing the adsorption Na⁺ ion at the S sites of electron-rich MoS₂.

Meanwhile, they also indicated that the change in spin-state of the Fe site of Fe_(SA)-N-C optimized the electronic structure and catalytic activity of the Fe site. 

Compared with nitrogen-doped carbon (N-C) and pure carbon, the Fe sites of Fe_(SA)-N-C could effectively promote the phase transition and structural evolution of 1T/2H-MoS₂ during the sodiation/desodiation process, thus prolonging the lifetime of the material. The 2H-MoS₂/Fe_(SA)-N-C anode showed a robust long-term cycling performance with a capacity of 350 mA h g^-1 after 2000 cycles at 2.0 A g^-1.