Heterointerface-engineered Fe3O4@NiS/Co3S4 electrodes for high-performance flexible all-solid-state asymmetric supercapacitors

Simultaneously achieving high energy density, flexibility, and durability remains a core challenge in next-generation energy storage, largely due to the intrinsic incompatibility between electrochemically complementary electrode materials. To address this challenge, we design a flexible all-solid-state asymmetric supercapacitor (ASC) using Fe 3 O 4 @NiS/Co 3 S 4 electrodes, where Fe 3 O 4 nanorods are grown on carbon cloth, and NiS/Co 3 S 4 is electrochemically deposited in distinct cycles for the anode and cathode. The fabricated ASC device exhibits remarkable electrochemical performance, including a high energy density of 77.6 Wh kg −1 , a power density of 828.3 W kg −1 , and excellent cycle stability with 91.7% capacitance retention after 10,000 cycles, clearly outperforming commercial activated-carbon supercapacitors that typically provide only 5–10 Wh kg −1 (at ∼200–500 W kg −1 ). Additionally, the device maintains stable performance even under mechanical deformation, with bending angles ranging from 0 to 180 degrees and twisting, demonstrating its robustness as a flexible energy storage solution. Density functional theory calculations reveal that the Fe 3 O 4 @NiS/Co 3 S 4 heterostructure enables strong K + adsorption (–1.55 eV) and low diffusion energy (0.25 eV), thereby promoting interfacial charge transfer and ion migration, enhancing ion/electron transport dynamics, and maximizing overall device performance. The synergistic electrode configuration offers scalable potential for high-performance energy storage applications.