NiX Layered Double Hydroxide Nanowire Arrays (X = Co, Fe, and Mn) Coated with Nanometer-Thick Films of NiOOH and Then NiO as Electrodes for Supercapacitors

Abstract

Owing to their low cost, transition metal layered double hydroxides (LDHs) have the potential to become the electrode material of choice for supercapacitors if they can provide good cyclic stability and high specific capacity. Herein, we introduce an approach for forming a high-quality, uniform thin film of nickel oxide (NiO) that can act as an auxiliary nickel oxyhydroxide (NiOOH) layer during redox cycling in an alkaline electrolyte. This approach leads to a core/double-shell NiCo-LDH/NiOOH/ALD-NiO electrode that exhibits an unprecedented specific capacity of 1420.2 C g–1 (even at 4 A g–1), retaining 93% of the capacity after 20,000 cycles. Even when combined with a simple anode of activated carbon, an asymmetric supercapacitor with this cathode provides an energy density of 72.6 W h kg–1 with exceptional durability (9.1% loss over 10,000 cycles). This extraordinary electrode when combined with an articulated anode in a supercapacitor is expected to meet or exceed the current energy density limit of lithium-ion batteries.

Atomic Layer Deposition—A Versatile Toolbox for Designing/Engineering Electrodes for Advanced Supercapacitors

“…[285] The same research team synthesized a NiCo-LDH/NiOOH/ALD-NiO with a coredouble-shell structure in which a thin film of ALD-NiO acted as a support to NiOOH to stabilize the electrode during tests, thereby improving the performance. [281] A 2-step process of hydrothermal and chemical bath deposition was performed to construct core/shell structures on NF, followed by ALD on the top shell to obtain the core/double-shell structure, as depicted in Figure 13g. The obtained electrode exhibited an unusual specific capacity (1420.2 C g -1 at 4 A g -1 ) and reserved 93% capacity even after 20 000 cycles.…”

“…Charge storage process of AC anode and CNN heteronanostructure cathode in the two-electrode system. Reproduced with permission [281]. Copyright 2021, American Chemical Society.…”

Solvent-induced structural regulation over Ni2P/CNT hybrids towards boosting the performance of supercapacitors

“…59 Additionally, it should be noted that the coulombic efficiency presents an increasing trend over the range of current densities, which can be ascribed to the formation of intermediate by-products such as NiO during the long-term oxygen reduction reaction at low current. 60,61 The calculated specific capacitances of the flower-like Ni 2 P/CNT hybrid are 1486, 1396, 1240, 1200, 1140 and 1115 F g −1 , at 1, 2, 4, 6, 8 and 10 A g −1 , respectively. In addition, we estimated the durability of the electrode materials following their long-term charge-discharge testing at a constant current density of 4 A g −1 .…”