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

Abstract

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.

In Situ Growth and Electrochemical Activation of Copper-Based Nickel–Cobalt Hydroxide for High-Performance Energy Storage Devices

“…Figure e shows the Ragone plot of our device in comparison with the earlier reported Cu-, Ni-, or Co-based HSCs. Our device exhibits a maximum energy density of 0.648 mW h cm –2 (29.4 W h kg –1 ) at a power density of 8.874 mW cm –2 (403 W kg –1 ) and shows a high energy density of 0.396 mW h cm –2 (18.0 W h kg –1 ) at a power density of 32.741 mW cm –2 (1488 W kg –1 ), which are quite impressive compared to some previously reported devices (Table S3), such as Cu 0.2 Ni 0.8 O//RGO, NiCo–CH@EGP//AC, Cu 3 Mo 2 O 9 NCAs//AC, CuO@Zn 1 Co 2 –OH//LSDC, Co 3 S 4 @Ni 3 S 4 //PC, NiCo LDH@NiSe//AC, CuO NBs//AC, CuO NSs//AC, H–NiCo LDH@ACC//AC, and Cu­(OH) 2 /Cu/Dacron//CNF/Dacron . Meanwhile, the EA-CuO/NiCo–OH//AC HSC exhibited enhanced stability with 93.4% capacity retention over 8000 GCD cycles under 50 mA cm –2 (Figure f).…”

Chemical Modifications of Layered Double Hydroxides in the Supercapacitor

“…In addition, the electrical conductivity and electron transfer rate of the LDHs are critical factors for pseudocapacitance. Hence, using a conductive template (Graphene, [32] conductive polymer [33] and metal substrate [34] ), and adding elements with good electrical conductivity [11] to increase the electrical conductivity and electron transfer rate are good modification strategies for LDH-based electrode materials. The effects of the modification strategies on the chemical properties and structural characteristics of the LDHs can be clarified to improve the pseudocapacitance ( Figure 3).…”

Nanostructure Nickel-Based Selenides as Cathode Materials for Hybrid Battery-Supercapacitors

“… Lu et al (2020) designed a layered structure with NiSe single-crystal nanorods as the core, and the outer layer uses nickel foam as the base to grow 2 nm ultra-thin thickness NiCo nanosheets to wrap the core( Figure 13 ). After testing, the specific capacitance of this electrode material reached 1,131 µAh/cm 2 at 5 mA/cm 2 .…”

“…The SC assembled with this electrode material and reduced graphene oxide has a maximum energy density of 37.5 Wh/kg, a maximum power density of 22.2 kW/kg, and cycle stability of more than 10,000 times. Lu et al (2020) designed a layered structure with NiSe singlecrystal nanorods as the core, and the outer layer uses nickel foam as the base to grow 2 nm ultra-thin thickness NiCo nanosheets to wrap the core(Figure 13). After testing, the specific capacitance of this electrode material reached 1,131 µAh/cm 2 at 5 mA/cm 2 .…”