Metallic 1T-MoS2 boosts the kinetics for NiS2-based hybrid supercapacitors with superb rate performance

Abstract

NiS2 with high theoretical capacitance shows great potential for supercapacitors (SCs). However, the poor cycling stability and sluggish redox kinetics have limited the development of high-rate NiS2-based SCs. Integrating materials with high conductivity potentially reinforces its structure and improves its rate capability. 1T-MoS2 featuring extended interlayer spacing and superior electronic conductivity emerges as an ideal candidate. Therefore, we designed a hybrid material with an alternating interconnected structure of NiS2 and MoS2 with adjustable content of 1T-MoS2. Owing to the improved ion/electron transmittability and the mutual shielding effect, an obvious positive correlation between rate capability and stability with 1T-MoS2 content was established. The optimized 1T-MoS2/NiS2 nanosheets (NMS-2) with 1T phase purity of up to 67.6% in MoS2 demonstrated exceptional specific capacity (579.4 C g−1 at 1 A g−1) and impressive rate capability (345.0 C g−1 at 30 A g−1), which suggests much faster kinetics compared to pure NiS2. Notably, the hybrid supercapacitor (HSC) assembled with NMS-2 as the cathode and activated carbon as the anode (NMS-2//AC HSC) exhibited a maximum specific capacitance of 137.4 F g−1 at 1 A g−1. Furthermore, this HSC can deliver a high energy density of 45.9 Wh kg−1 at 774.9 W kg−1, and could retain 17.7 Wh kg−1 even at a high power density of 7731.7 W kg−1. After 5000 cycles at a high current density of 5 A g−1, the HSC still remained 93.23% of its initial capacitance with an extremely low fading rate of 0.0014% per cycle.