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

A Mott–Schottky (MS) heterojunction of CoS2/NiS2 embedded in a carbon matrix is successfully synthesized to form a high sodium storage CoS2/NiS2@C anode material for sodium-ion batteries. The underlying mechanism for performance enhancement are investigated by both in/ex-situ measurements and DFT calculations. This research has taken an important step towards the development of high-performance electrode materials for sodium-ion batteries. [Display omitted] •Carbon-matrix-embedded MS heterojunction of CoS2/NiS2 is successfully prepared.•The as-prepared CoS2/NiS2@C exhibits exceptional sodium storage properties.•The mechanism is revealed by DFT calculations & in/ex-situ characterizations.•The C-S bond promotes Na+ in the carbon matrix to migrate to embedded CoS2/NiS2.•MS heterojunction in CoS2/NiS2 accelerates electrochemical reaction kinetics. 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.