Co₃O₄/NiCo₂O₄ Perforated Nanosheets for High-Energy-Density All-Solid-State Asymmetric Supercapacitors with Extended Cyclic Stability

Abstract

To develop new-generation electrode materials for high-performance all-solid-state asymmetric supercapacitors (ASSASCs), herein, Co3O4/NiCo2O4 perforated nanosheets are synthesized using a trisodium-citrate-assisted chemical precipitation by the hydrothermal method, at an elevated pH medium. The physicochemical analyses of Co3O4/NiCo2O4 by powder X-ray diffraction (PXRD), Fourier transform (FT)-Raman, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) methods show ideal properties of a supercapacitor electrode material, such as discrete phases due to Co3O4 and NiCo2O4, small-size crystallites, and uniquely perforated nanosheets with an overlapped architecture. The preliminary charge storage efficiency study of Co3O4/NiCo2O4 in a three-electrode setup shows pseudocapacitive charge storage phenomena, significant kinetic reversibility, high specific capacitance and good rate capacitance, very low charge transfer resistance, and bias-potential-independent total series resistance. Further, the 1.8 V Co3O4/NiCo2O4∥N-rGO ASSASC device, fabricated using Co3O4/NiCo2O4 and nitrogen-doped reduced graphene oxide (N-rGO) as the positive and negative electrode materials, respectively, delivers excellent capacitance (areal- and mass-specific) and rate capacitance at extreme reaction conditions. The ASSASC device also delivers high energy density, excellent rate energy density at elevated power density conditions, and ∼93.8% capacitance retention, after 10 000 successive galvanostatic charge/discharge (GCD) cycles. The outstanding efficiency of the Co3O4/NiCo2O4∥N-rGO ASSASC device is ascribed to the superior conductivity of Co3O4/NiCo2O4 perforated nanosheets augmented by N-rGO, abundant electrolyte channels in the overlapped perforated nanosheets of Co3O4/NiCo2O4, and improved electromechanical stability offered by the “OH– ion-buffering-reservoir”-like behavior of Co3O4/NiCo2O4.

Significantly improved conductivity of spinel Co3O4 porous nanowires partially substituted by Sn in tetrahedral sites for high-performance quasi-solid-state supercapacitors

“…The small capacitance loss (5.61%) of the CSO@GF electrode aer 10 000 cycles indicates the prominent long-term cycling stability of the CSO@GF electrode. Furthermore, the CSO@GF electrode showed remarkable capacitance performance and long-term cycling stability, which are superior to those of previously reported Co 3 O 4 -based electrodes, such as Co 3 O 4 /g-C 3 N 4 (780 F g À1 , 80% aer 1000 cycles), 34 Co 3 O 4 /NiCo 2 O 4 hollow spheres (1767 F g À1 ), 35 and CoWO 4 /Co 3 O 4 octahedrons (1728 F g À1 , 85.9% aer 5000 cycles). 36 The electrochemical impedance spectra were recorded to evaluate the electrical conductivity of the GF, Co 3 O 4 @GF, and CSO@GF electrodes and the results are shown in Fig.…”

Encapsulation of Co3O4 Nanocone Arrays via Ultrathin NiO for Superior Performance Asymmetric Supercapacitors

“…Additionally, the asymmetric device composed of Co 3 O 4 /NiCo 2 O 4 ||N‐rGO retains 93.8% areal capacitance after 10 000 operating cycles. [ 28 ] An excellent core–shell type CoO@Co 3 O 4 nanocrystals were grown solvothermally which delivered 3377 F g −1 specific capacitance at current density 2 A g −1 and the capacity retention was about 58.6% after 4000 charge–discharge cycles. [ 29 ] Lu et al.…”

Iron-Facilitated Transformation of Mesoporous Spinel Nanosheets into Oxyhydroxide Active Species in the Oxygen Evolution Reaction

“…The structure of Fe x Ni 1– x Co 2 O 4 nanosheets was further characterized by Raman spectroscopy. As shown in Figure b, the corresponding Raman shifts located at 185, 468, 513, 602, and 651 cm –1 can be ascribed to the characteristic F 2g , E g , F 2g , F 2g , and A 1g phonon modes of NiCo 2 O 4 and Fe 0.2 Ni 0.8 Co 2 O 4 . , The results of Raman spectra further verify that the structure of Fe x Ni 1– x Co 2 O 4 nanosheets is similar to that of NiCo 2 O 4 nanosheets, which indicated that Fe substitution did not change the local structure. This result is in good agreement with the XRD results.…”

“…X-ray photoelectron spectroscopy (XPS) measurements were further carried out to measure the surface chemical environment of Fe x Ni 1– x Co 2 O 4 nanosheets (Figure S5). In the pure NiCo 2 O 4 and Fe 0.2 Ni 0.8 Co 2 O 4 , the high-resolution Ni 2p spectra (Figure a) contain two different types of nickel species, suggesting two chemical states of Ni. ,, Specifically, the two spin–orbit doublet peaks centered at 853.7 and 871.4 eV can be assigned to Ni 2p 3/2 and Ni 2p 1/2 of the Ni 2+ oxidation state, while the peaks located at 855.4 and 873.3 eV are attributed to the Ni 3+ oxidation state. In contrast to the pristine NiCo 2 O 4 , the increased intensity ratio of Ni 3+ /Ni 2+ in Fe 0.2 Ni 0.8 Co 2 O 4 indicates an increase in the amount of Ni 3+ .…”