Sustainable utilization of cellulose-rich corn husk for activated carbon in high-performance sodium-ion capacitors

• Corn husk-derived activated carbon delivers superior performance in sodium-ion capacitor cathodes. • The composite achieves an energy density of 101 W h kg −1 , outperforming commercial activated carbon. • The composite retains 82% capacity after 10,000 cycles, showcasing long-term durability. • The sustainable corn husk-based activated carbon offers a low-cost, eco-friendly option. Sodium-ion capacitors (SICs) are a promising next-generation energy storage system, offering high energy and power densities by utilizing sodium as a cost-effective alternative. A key challenge in developing SICs is identifying suitable active materials. While commercial activated carbon (AC) is predominantly used for capacitor-type cathodes, developing ACs with a significantly higher capacitance is necessary to achieve higher energy densities. Herein, the potential of an AC derived from a corn husk and graphene oxide composite (CHGO) is investigated as a capacitive-type cathode for the SIC, taking advantage of the natural abundance, low production cost, and straightforward preparation process of corn husk. The corn husk-derived AC is prepared via chemical activation with KOH, and the graphene oxide content is optimized to improve the conductivity and stability. The rate capability and cyclic stability of the prepared CHGO are tested in an organic electrolyte, demonstrating its superior electrochemical performance compared to commercial AC. The assembled SICs exhibit a high energy density of 101 W h kg −1 , a high-power density of 8.8 kW kg −1 , and an outstanding capacity retention of 82 % after 10,000 cycles. These findings underscore the potential of utilizing corn husk-derived AC for enhanced electrochemical performance in SICs.