MXene-induced interfacial charge modulation in sulfide/hydroxide heterostructures for fast redox kinetics toward high-performance and durable hybrid supercapacitors

The limited accessibility of active sites within electrode materials significantly reduces the electrochemical performance of supercapacitors (SCs) and poses challenges such as low energy density and poor stability in real-world conditions. This has increased the need for highly active, durable and cost-effective electrode materials. In this study, a NiCo 2 S 4 /CuFe-LDH hybrid electrode with Mo 2 TiC 2 T X MXene (NCM) was developed via a hydrothermal method, in which the MXene layers form well-defined heterojunctions. This technique allowed precise adjustment of the NiCo 2 S 4 /CuFe-LDH electronic structure by controlling its MXene content. The NCM electrode demonstrated excellent energy storage efficiency due to the synergistic interaction among the MXene, NiCo 2 S 4 and CuFe-LDH, which promoted charge transfer and improved electrochemical kinetics. The NCM20 electrode with optimized MXene loading performed exceptionally well as a positive electrode, delivering a high specific capacity of 194.5 mAh g −1 at 2 A g −1 in 6 M KOH and maintaining 94.4% of its initial capacity after 20,000 cycles. The assembled hybrid supercapacitor (NCM20 (+) //N-doped carbon (−) ) reached a maximum energy density of 44.3 W h kg −1 at 723.0 W kg −1 power density, retaining 89.2% capacity after 15,000 cycles. Theoretical analysis indicates the presence of an intrinsic electric field at heterointerfaces and MXene incorporation significantly improves NCM's electronic conductivity, thereby increasing ion adsorption and energy storage efficiency.