In Situ Engineered Multimetal Phases of NiTe/Fe ₃ O ₄ on Few-Layer MXene for Supercapattery Cathodes

The strategic integration of multimetal phases within nanoengineered heterostructures enables the synergistic utilization of enriched redox sites, optimized electronic structures, and stabilized nanointerfaces. Herein, we present a rationally designed high-performance hybrid cathode material achieved via in situ hydrothermal growth of NiTe/Fe 3 O 4 (NTFO) nanoparticles (∼3–4 nm) on alkali-assisted flocculated few-layer MXene (f-MXene, ∼2.1 nm). The few-layer morphology of f-MXene maximizes the interfacial contact, improves the electrolyte accessibility, and provides robust mechanical support. Benefiting from the nanoscale advantages of the individual components, rich redox activity of NTFO, and metallic conductivity as well as high interfacial area of f-MXene, the resulting NTFO/f-MXene (NTFO@f-MX) composites demonstrate exceptional electrochemical performance. Specifically, the NTFO@f-MX60 heterostructure with an optimized f-MXene content exhibits a high specific capacitance of 1347.8 F/g (808.7 C/g) at 1 A/g and maintains an outstanding rate performance of 1039.5 F/g (623.7 C/g) at 9 A/g. The NTFO@f-MX60∥AC (AC, activated carbon) asymmetric device delivers a high energy density of 37.3 Wh/kg and a power density of 7200 W/kg, outperforming many previously reported supercaps. Furthermore, the device retains 89.1% of its initial capacitance for up to 6000 charge–discharge cycles at 9 A/g. This outstanding charge storage behavior is attributed to the synergistic interfacial effects at the nanoscale, where intimate NTFO–f-MXene contact facilitates enhanced faradaic activity, efficient charge transport, and mechanical stability. Our findings underscore the vital role of multimetal phases and precisely engineered heterointerfaces in advancing next-generation hybrid energy storage devices.