Polydopamine-derived nitrogen-doped carbon-coated NiS nanoparticles as a battery-type electrode for high-performance supercapacitors

The design of core-shell nanocomposites has become a valid solution to improve the electrochemical performance of materials. This study reports a simple and extensible method for preparing N-doped carbon-coated NiS core-shell composites at different temperatures (300 °C and 500 °C, denoted as NiS@NC-300, NiS@NC-500). We discussed the effect of pyrolysis temperature on composites. At high temperature, the coating of PDA protects the original crystalline structure and microstructure of NiS to a certain extent, lowering the original high temperature instability of NiS. In addition, the core-shell structure contributes to adapting and buffering the volume change of NiS in charge-discharge cycles. Moreover, carbon layer tightly connects NiS nanoparticles to form a stable interconnected network framework structure to enhance electrochemical stability. Benefiting from these structural advantages, NiS@NC-300 exhibits a higher specific capacity of 665C g⁻¹ (1330 F g⁻¹) at 0.5 A g⁻¹ and significantly enhanced cycle stability that 92.3% of the initial capacity is retained over 3000 cycles at 10 A g⁻¹, which are far better than NiS. An asymmetric supercapacitor (ASC) comprised of NiS@NC-300 and the commercial activated carbon (AC) electrodes delivers a high energy density of 28.6 Wh kg⁻¹ at the power density of 884.5 W kg⁻¹ and shows great cycle stability with the retention of 81.7% after 3000 cycles. NiS@NC-300 demonstrates its attractive potential in the domain of practical energy storage devices.