Atomically engineered Ni3S2/Co9S8 heterointerfaces on carbon backbone enable ultra-stable and high-energy–density supercapacitors

Transition metal sulfides (TMSs) hold immense promise for high-performance supercapacitors due to their rich redox chemistry and exceptional theoretical capacitance. However, their practical realization is severely hampered by intrinsically poor electronic conductivity and detrimental volumetric changes during cycling, which compromise rate performance and long-term stability. Herein, we rationally design and fabricate Ni 3 S 2 /Co 9 S 8 heterostructures intimately anchored on conductive carbon nanofibers (CNFs). This unique architecture creates abundant heterointerfaces that induce synergistic charge redistribution, generating a robust built-in electric field. This field critically accelerates redox reaction kinetics and interfacial charge transfer, while the integrated CNF network ensures efficient electron pathways and buffers pulverization, thus maintaining structural integrity. Consequently, the optimized Ni 3 S 2 /Co 9 S 8 @CNFs electrode delivers a specific capacitance of 1679F g −1 at 0.5 A g −1 . Moreover, an assembled Ni 3 S 2 /Co 9 S 8 @CNFs//AC asymmetric supercapacitor achieves a energy density of 67.7 W kg −1 at power density of 750 W kg −1 , coupled with excellent cycling stability (96.2 % capacitance retention after 10,000 cycles). This work not only demonstrates a potent strategy for fabricating advanced TMS-based electrodes but also provides fundamental insights into heterointerface engineering for superior electrochemical energy storage, paving the way for next-generation high-energy–density devices.