In situ synthesis of nitrogen site activated cobalt sulfide@N, S dual-doped carbon composite for a high-performance asymmetric supercapacitor

[Display omitted] Cobalt sulfides with high theoretical capacity are considered as potential electrodes for supercapacitors (SCs). However, the insufficient reactive sites and low electrical conductivity of bulky cobalt sulfides restrict their applications. Here, we proposed an efficient approach for in situ formation of nitrogen site activated cobalt sulfide@N, S dual-doped carbon composite (CS@NSC) by vulcanizing the cobalt-glutamine complex (CG) precursor in a tube furnace. The effects of the molecular structure and calcination temperature of CG precursors on the morphology, structure and electrochemical performance of CS@NSC were studied. The designed CS@NSC-2 exhibited a specific capacity of 593 C g−1 at the current density of 1 A g−1 and good cyclic stability with 88.7% retention after 2000 cycles. Moreover, an asymmetric supercapacitor (ASC) was fabricated by CS@NSC-2 (positive electrode) and activated carbon (AC) (negative electrode), which delivered ultra-high energy density of 67.8 Wh kg−1 at a power density of 400 W kg−1 and possessed 83.1% capacitance retention after 5000 cycles. The eco-friendly method was also suitable for synthesizing nickel sulfide. This work may provide an innovative horizon for the in situ formation of active sites in electrode materials.