2-nm-Thick NiCo LDH@NiSe Single-Crystal Nanorods Grown on Ni Foam as Integrated Electrode with Enhanced Areal Capacity for Supercapacitors

It remains a great challenge to simultaneously guarantee the conductivity and high areal loading of active materials for integrated electrode of supercapacitors. Herein, we designed a hierarchical structure with cores of NiSe single-crystal nanorods and sheaths of 2-nm-thick NiCo thin sheets grown on nickel foam (NiCo LDH@NiSe/NF) as integrated electrode. It reaches a high areal capacity of 1131 μAh cm⁻² at a current density of 5 mA cm⁻², which is 2.2 times of NiSe/NF (522 μAh cm⁻²) and 6.0 times of NiCo LDH/NF (189 μAh cm⁻²), superior to most reported integrated electrodes. The enhanced areal capacity can be ascribed to the high active material loading of 6.5 mg cm⁻² (twice more than other reported values) and considerable conductivity of single-crystal NiSe nanorods of 2630 S cm⁻¹. The fabricated hierarchical integrated electrode of NiCo LDH@NiSe/NF assembled with activated carbon shows a maximum energy density of 0.454 mWh cm⁻² and a maximum power density of 80 mW cm⁻². This work presents supports of single-crystal nanorods for thin LDH sheets to fabricate high-density hierarchical structure for integrated electrode, which improves the conductivity and structural stability of active materials especially the LDHs, resulting in excellent electrochemical performance. It offers a promising approach to engineer and fabricate advanced supercapacitors with enhanced areal capacity.