Constructing CoNC coordination in Co9S8 embedded N,S-codoped carbon nanotube as an advanced electrode for supercapacitor and Na-ion battery.

Yolk-shell-structured transition metal sulfides (TMSs)/carbon nanocomposites are highly desirable in advanced energy storage system, such as sodium-ion batteries (SIBs) and supercapacitors (SCs). Nevertheless, practical applications are still prevented by the loose attachment of TMSs with carbon caused by conversion stress, the aggregation of TMSs nanoparticles and the sluggish ion transport caused by high crystallinity of carbon. Here, the disperse hollow Co9S8 nanoparticles encapsulated into N,S-codoped carbon nanotubes (CNTs) with poor crystallinity through CoNC bond was synthesized (CS-NSCNT) to overcome the above obstacles. The designed CS-NSCNT can provide the short diffusion path and prevent the huge volume expansion of conversion reaction. Moreover, the established CoNC bond endows the strong interaction and regulates the electronic structure thus promote the stability and rate performance effectively. The CS-NSCNT SCs's electrode delivers a high specific capacitance of 1150 F g-1 at 1 A g-1, with a high cycling life stability and rate performance. For SIBs, the CS-NSCNT cathode demonstrates an initial reversible capacity of 475 mAh g-1 at 0.1 A g-1 and an excellent rate performance with a capacity retention of 53 % at 10 A g-1. This work may satisfy the long-stability, high-capacitance/capacity, high-power/energy density application requirements of future applications.

In situ synthesis of core-shell vanadium nitride@N-doped carbon microsheet sponges as high-performance anode materials for solid-state supercapacitors.

Vanadium nitride (VN) with high conductivity exhibits the potential promising as anode materials for supercapacitors, but VN suffered the obvious performance fading due to the dissolution of VN in aqueous electrolyte. In this work, we solve these problems through realizing 3D structural VN microsheets shelled with N-doped carbon layer (VN@NC) by introducing melamine as nitrogen source and PVP as carbon source. The as-prepared VN@NC electrode display high capacitance of 368 F g-1 and good rate property. A solid-state asymmetric supercapacitor (ASC) with NiCo2O4 nanowires as cathode materials and VN@NC as anode materials was fabricated. The ASC device exhibits the high energy density of 65.3 W h kg-1, and good cycling stability (92% capacitance retention) after 4000 cycles. Moreover, the ASC device shows good mechanical flexibility with negligible capacitance loss after 1000 bending cycles.