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.