High-Capacity and High-Rate sodium storage of CoS2/NiS2@C anode material enabled by interfacial C-S covalent bond and Mott-Schottky heterojunction

In this paper, carbon-matrix-embedded Mott-Schottky (MS) heterojunction of CoS2/NiS2 (CoS2/NiS2@C) is prepared. The obtained CoS2/NiS2@C offers superior sodium storage performance such as large specific capacity (861.0 mAh/g at 2 A/g), extraordinary rate capability (649.2 mAh/g at 10 A/g, 371.4 mAh/g at 40 A/g) and excellent cycling stability (380.5 mAh/g after 3000 cycles at 10 A/g, and 298.5 mAh/g after 2000 cycles at 40 A/ g). Electrochemical measurements and density functional theory (DFT) calculations as well as in/ex-situ characterization techniques are employed to reveal the underlying mechanisms. It is found that the outperforming sodium storage properties of CoS2/NiS2@C can be mainly attributed to the C-S bond and the MS heterojunction. The C-S bond formed at the interface between CoS2/NiS2 and the carbon matrix promotes the migration of the sodium ions in the carbon matrix to the embedded CoS2/NiS2, while the MS heterojunction accelerates the electrochemical reaction kinetics of CoS2/NiS2. Moreover, full-cell is assembled with CoS2/NiS2@C and Na3V2(PO4)3/C to validate the practical application of CoS2/NiS2@C. The full-cell achieves both high specific capacity and outstanding rate performance, demonstrating the great application potential of such CoS2/NiS2@C anode in high-performance sodium-ion batteries.