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

Abstract

traditional battery systems. [10,11] Practically, lower energy density bounds the applicability of supercapacitors over battery systems, leaving more room in developing high energy density supercapacitors without having to compromise the power competence. [12-14] A well-known approach offering such outstanding energy density is via fabrication of asymmetric supercapacitor device that focusses on the positive materials excellency exhibiting high specific capacitance and providing a broad potential window when combined with a double-layer type negative electrode material. [15-17] Co 3 O 4 , a pseudocapacitive metal oxide, belonging to the family of spinel is a promising positive active material in electrochemical energy storage devices owing to its high specific capacitance (3560 F g −1) theoretically with being earthabundant, cost-effective, and also environment friendly. [18-20] Pseudocapacitors follow faradaic redox electrochemical reactions on the material's surface through continuous intercalation/deintercalation of electrons or ions which makes the surface vulnerable to destruction resulting in lower efficiency of the electroactive material affecting the electrochemical cycles. [21-23] Therefore, much effort has been put forward to increase the efficiency and stability of the Co 3 O 4 structures through nanostructured, [18] heterostructured, [24,25] and core-shell type structures [26] to reduce the structural deterioration from Co 3 O 4 and increase the overall specific capacitances. For instance, a 3D hierarchical structure of CoWO 4 /Co 3 O 4 was developed that exhibited significantly high specific capacitance of 1728 F g −1 at a current density of 1 A g −1 retaining about 85.9% specific capacitance after 5000 cycles. [27] Paliwal and Meher design a heterostructure of Co 3 O 4 /NiCo 2 O 4 perforated nanosheets that delivers specific capacitance of 1767 F g −1 at a current density of 0.5 A g −1 maintaining 552 F g −1 capacitance at high current density 16 A g −1. 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. reported Co 3 O 4 /CoS core-shell nanosheets grown over Ni-foam by room temperature sulfurization process. The structure showed an improved specific capacitance as high as 1658 F g −1 at 1 A g −1 Designing of multicomponent transition metal oxide system through the employment of advanced atomic layer deposition (ALD) technique over nanostructures obtained from wet chemical process is a novel approach to construct rational supercapacitor electrodes. Following the strategy, core-shell type NiO/Co 3 O 4 nanocone array structures are architectured over Ni-foam (NF) substrate. The high-aspect-ratio Co 3 O 4 nanocones are hydrothermally grown over NF following the p...

All Si3N4 Nanowires Membrane Based High‐Performance Flexible Solid‐State Asymmetric Supercapacitor

“…[7] Construction of asymmetric supercapacitors (ASCs) with the extended V is considered as an effective method to improve the energy density, arising from the opposite potential windows of the positive and negative electrodes. [8][9][10] Accordingly, many attempts have been devoted to the rational design of electrodes, including the construction of active materials and current collectors, which play a vital role to achieve superior performance of flexible ASC devices. [11] For active materials, transition metal oxides (TMOs) or hydroxides, due to their abundance, low cost, hypotoxicity, and multiple oxidation states, have been widely investigated and attracted considerable attention.…”

Atomic Layer Deposition of NiO on Self‐Supported Co3O4 Nanoneedle Array for Electrocatalytic Methanol Oxidation Reaction

“…The fitted peaks at 855.57 and 873.62 eV are ascribed to Ni 3þ , whereas the fitted peaks at 853.95 and 871.95 eV correspond to Ni 2þ . [30,32,33] The Ni 2þ peaks from the Ni─O bonds confirm the formation of NiO on Co 3 O 4 nanoneedle array, whereas Ni 3þ state should be ascribed to the generation of Ni 3þ due to the surface oxidation. The O1s spectra of 400c-NiO-Co 3 O 4 NA can be divided into three peaks marked as O1, O2, and O3, located at 529.54, 531.08, and 532.7 eV, respectively.…”

Transition Metal Oxide Electrode Materials for Supercapacitors: A Review of Recent Developments

“…Co 3 O 4 has the advantages of high theoretical specific capacitance (3560 F g −1 ), low price, environmental friendliness, and good chemical durability, so it is a promising active material [ 75 , 76 , 77 ]. However, the capacitance in practical application differs a lot from the theoretical value.…”