Hierarchically constructed NiCo₂S₄@Ni_(1−x)Co_x(OH)₂core/shell nanoarrays and their application in energy storage

Abstract

We report a new type of core-shell heterostructure consisting of a rod-like NiCo2S4 (NCS) core and an urchin-like Ni(1-x)Co x (OH)2 (NCOH) shell via a simple hydrothermal route coupled with a facile electrodeposition. NCS nanorod arrays (NRAs) can not only act as excellent electrochemically active materials by themselves, but they can also serve as hierarchical porous scaffolds capable of fast electron conduction and ion diffusion for loading a large amount of additional active materials. Moreover, it is observed that the urchin-like NCOH nanosheets coating could bind the inner NCS nanorods together and thereby reinforce the whole structure mechanically. Meanwhile, more effective pathways for electrons are available in the NCS@NCOH hybrids than an individual NCS nanorod. Benefiting from both structural and compositional features, the NCS@NCOH electrode exhibits greatly improved electrochemical performance with high capacity (3.54 C cm(-2) at 1 mA cm(-2)) and excellent cycling stability (78% capacity retention after 4000 cycles). Moreover, a battery-type device is also fabricated by using NCS@NCOH as a positive electrode and activated carbon (AC) as a negative electrode, displaying high capacity (2.51 C cm(-2) at 2 mA cm(-2)) and good durability (88.8% capacity retention after 4000 cycles) as well.

Enhanced cycling stability of NiCo2S4@NiO core-shell nanowire arrays for all-solid-state asymmetric supercapacitors

“…And the calculated results of the specific capacitance based on the active mass was also provided in Figure S2. Obviously, the NiCo 2 S 4 @NiO NWAs electrode delivers much higher areal specific capacitance than the NiCo 2 S 4 nanowire arrays or NiO nanosheets, and also higher than many previously reported electrodes based on NiCo 2 S 4 , such as NiCo 2 S 4 @Ni (1−x) Co x (OH) 2 core-shell nanoarrays (3.54 F cm −2 at 1 mA cm −2 )31, NiCo 2 S 4 nanotube@Ni-Mn Layered Double Hydroxide arrays/graphene sponge (1.74 F cm −2 at 1 mA cm −2 )28, NiCo 2 S 4 nanotube@ NiCo 2 S 4 nanosheet arrays on Ni foam (4.38 F cm −2 at 5 mA cm −2 )32 and NiCo 2 S 4 @MnO 2 heterostructures (2.6 F cm −2 at 3 mA cm −2 )33. The high specific capacitance of the electrode can be attributed to the specific core-shell arrays structure and the well-designed combination of NiCo 2 S 4 with NiO.…”

Supercapacitor Performance of Nickel-Cobalt Sulfide Nanotubes Decorated Using Ni Co-Layered Double Hydroxide Nanosheets Grown in Situ on Ni Foam

“…As calculated, the values of SC of the NCS@NCOH_2 electrode are 2105.1, 1887.7, 1708.3, 1503.5, 1364.7, and 1128.3 Fg −1 at 2, 5, 10, 20, 30, and 50 Ag −1 current densities, respectively. Once the CD increases, the electrochemical reaction is noticeably slower than the rate of electron transfer, and thus, the electrode materials do not have sufficient time to contribute to a redox reaction, resulting in a reduction in capacity [28]. Figure 8a shows that the NCSNTs decorated with NCOH nanosheets electrodeposited as an electrode for 40 s achieve a high SC of 2105.1 Fg −1 at 2 Ag −1 .…”

Synthesis of the Urchin‐Like NiS@NiCo2S4 Composites on Nickel Foam for High‐Performance Supercapacitors

“…Ni@NiS@NiCo 2 S 4 //AC ASC exhibited excellent cycling stability with 78.7 % capacitance retention when cycling at 50 mA cm À 2 for 5000 cycles. The electrochemical performance is superior or equivalent to the reported nickle cobalt sulfides previously [46][47][48][49][50][51][52][53][54][55][56][57] and the result is listed in Table 1. These results demonstrate that the self-supported and binder-free Ni@NiS@NiCo 2 S 4 composite electrode is a potential candidate for highly stable energy storage devices.…”