Bimetallic heterojunction of CuSe/ZnSe@Nitrogen-doped carbon with modified band structures for fast sodium-ion storage

Abstract

Transition metal selenides have attracted extensive attention for sodium-ion batteries (SIBs) by virtue of high capacity and intrinsic safety. However, mono-metallic selenides suffer from the low conductivity and sluggish kinetics for Na+ ions transfer. Herein, bimetallic selenide (CuSe/ZnSe@NC) is constructed with modified band structure to boost the fast Na+ ions diffusion. Particularly, the implantation of heterojunction triggers the sublattice distortion and charge redistribution, which is beneficial to provide abundant active sites and regulate band structure. As expected, bimetallic CuSe/ZnSe@NC delivers the specific capacities of 411.5 mA h g−1 after 1000 cycles at 1 A g−1 and 361.8 mA h g−1 at 5 A g−1, indicating the superior cycle and rate performance than that of mono-metallic selenides. Meanwhile, in-situ XRD, TEM, and EIS further reveal the high reversibility and the conversion and alloying mechanisms of bimetallic CuSe/ZnSe@NC for SIBs. Moreover, first-principles calculations (DFT) further confirm that the fast Na+ ions diffusion is attributed to the optimized band structure and the charge rearrangement. Therefore, bimetallic heterojunctions not only combined the multifunctional properties, but also exhibited unique physicochemical properties that transcend mono-metallic selenides.