Designed formation of C/Fe₃O₄@Ni(OH)₂ cathode with enhanced pseudocapacitance for asymmetric supercapacitors

The rational design and synthesis of advanced electrode materials are significant for the applications of supercapacitors. Ferroferric oxide (Fe₃O₄), with its high theoretical capacitance is a renowned cathode material. Nevertheless, its low electronic conductivity and poor cycling stability during a long-term charge/discharge process limit its large-scale applications. In this work, the precise modulation of multiple components was reported to enhance electrochemical performance. The ternary heterostructures were fabricated by wrapping ultrathin nickel hydroxide (Ni(OH)₂) nanosheets on the surfaces of Fe₃O₄ nanoparticles-loaded on sodium carboxymethyl cellulose (CMC)-derived porous carbon, named as C/Fe₃O₄@Ni(OH)₂. Due to the large specific surface area and excellent conductivity of CMC-derived porous carbon and the abundant reaction sites of Ni(OH)₂ nanosheets, the optimized C/Fe₃O₄@Ni(OH)₂-1.0 sample exhibited the highest specific capacitance of 3072F g^-1 at a current density of 0.5 A g^-1. Furthermore, the assembled asymmetric supercapacitor (ASC) with activated carbon and C/Fe₃O₄@Ni(OH)₂-1.0 as the negative and positive electrodes, respectively, showed an energy density of 123 W h kg^-1 at 381 W kg^-1, and a long-life stability with an excellent capacitance retention of 90.04 % after 10,000 cycles. The route for preparing composite electrode materials proposed in this work provides a reference for realizing high-performance energy storage devices.