Ordered mesoporous Co3O4/CMC nanoflakes for superior cyclic life and ultra high energy density supercapacitor (original) (raw)
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Journal of Solid State Electrochemistry, 2019
Innovative electrode materials are the need of the hour towards the fabrication of electrochemical energy storage systems with superior performance. In the objective of designing flexible high power supercapacitors, herein, we have synthesized β-cobalt hydroxide/carboxymethyl cellulose nanoflakes via a facile route using anionic, cationic, and non-ionic structure directing agents. When tested as a supercapacitor electrode, β-cobalt hydroxide/carboxymethyl cellulose nanoflakes prepared using cationic surfactant (cetyltrimethylammonium chloride) exhibit better electrochemical behaviour including specific capacitance (306 C g −1 at a scan rate of 2 mV s −1), excellent cycle life (89% capacitance retention even after 5000 repeated charge/ discharge cycles) in an aqueous alkaline solution. Furthermore, we have designed an asymmetric supercapacitor utilizing βcobalt hydroxide/carboxymethyl cellulose and activated carbon as electrodes which is capable of delivering an energy density of 29.7 W h kg −1 with the power density of 695 W kg −1. The notable features of this device open pathways for the new electrode materials in supercapacitors.
Journal of Materials Science: Materials in Electronics, 2018
This paper reports ecofriendly synthesis of mesoporous cobalt hydroxide using carboxymethyl cellulose as carbon source. Different analytical investigations on this material indicate the formation of mesoporous flakes. This kind of morphology is highly favorable for energy storage applications. The electrochemical performance of the electrode material is evaluated for supercapacitor, in an alkaline electrolyte; it shows high specific capacitance and good rate capacity. In addition, it retains 93% of initial capacitance after 3000 repeated charge-discharge cycles. This attractive nanocomposite shows very low value of charge transfer resistance (1 Ω). We design an asymmetric supercapacitor device using β-Co (OH) 2 /C and activated carbon as electrode. This device exhibits a specific capacitance of 102 F g −1 at 1 A g −1. The outcomes of these studies suggest its usefulness in supercapacitor devices.
Carbon, 2019
Low-cost multi-heteroatom doped porous carbons derived from agricultural waste were prepared as the base material. Then, the cobalt oxides nanosheets were anchored to the surface of the carbon material to obtain the composites. It was found that the adoption of porous carbon is of great significance for the improvement of materials properties. The presence of porous structure derived from carbon materials not only increases the stability of the material, but also facilitates the diffusion and transfer of electrolyte ions. Meanwhile, the flaky Co 3 O 4 endows the material with high energy density and high charge transport efficiency. The resulted composite materials exhibit high specific surface area with low electrochemical impedance. Both aqueous and solid-state SCs were assembled separately. The energy density of aqueous SC can reach up to 42.5 Wh kg À1 at a power density of 746 W kg À1 and even with power density up to 30 kW kg À1 as the energy density still maintained 25 Wh kg À1. As for solid-state SC, the energy density can reach 40.6 mWh cm À2. The retention of solid-state SC can maintain at 87.1% even after 3000 cycle numbers. The excellent performance of composites enables them to be promising electrode materials for energy storage.
Cubic spinel Co 3 O 4 nanoparticles with spherical (0D) and hexagonal platelet (2D) morphologies were synthesized using a simple solvothermal method by tuning the reaction time. XRD and HRTEM analyses revealed pure phase with growth of Co 3 O 4 particles along [111] and [110] directions. UV−vis studies showed two clear optical absorption peaks corresponding to two optical band gaps in the range of 400−500 nm and 700−800 nm, respectively, related to the ligand to metal charge transfer events (O 2-→ Co 2+,3+ ). Under the electrochemical study in two electrode assembly system (Co 3 O 4 /KOH/ Co 3 O 4 ) without adding any large area support or a conductive filler, the hexagonal platelet Co 3 O 4 particles exhibited comparatively better characteristics with high specific capacitance (476 F g −1 ), energy density 42.3 Wh kg −1 and power density 1.56 kW kg −1 at current density of 0.5 Ag −1 , that suited for potential applications in supercapacitors. The observed better electrochemical properties of the nanoporous Co 3 O 4 particles is attributed to the layered platelet structural arrangement of the hexagonal platelet and the presence of exceptionally high numbers of regularly ordered pores.
SSRN Electronic Journal, 2021
Bimetal oxides are promising materials in the field of energy storage due to their various oxidation states, synergistic interactions among multiple metal species, and stability. In this work, Co 3 V 2 O 8 hollow spheres are synthesized by a two-step hydrothermal method: (i) synthesis of V 2 O 5 spheres and (ii) partial replacement of V by Co through the Kirkendall effect. As an electrode, it shows an extrinsic pseudocapacitive charge-storage mechanism due to different oxidation states of V and Co ions. Because of the low crystallinity degree of the mesoporous wall and high accessible surface area of hollow spheres, the optimum Co 3 V 2 O 8 electrode reaches a high specific capacitance of 2376F g − 1 at a current density of 2 A g − 1 , which is more than two times higher than the top reported values, and a rate capability retention of ~80% at 20 A g − 1. Using Co 3 V 2 O 8 , activated carbon, and KOH as positive, negative electrodes, and electrolyte, respectively, a hybrid supercapacitor device presents maximum energy and power densities of 59.2 Wh kg − 1 and 36.6 kW kg − 1 , respectively. Further, the aqueous supercapacitor device shows superior structural and electrochemical stabilities after 10,000 galvanostatic charge-discharge cycles because of the arrays of voids in the orthorhombic crystal structure of Co 3 V 2 O 8 that can decrease the volume expansion/shrinkage during the intercalation/deintercalation processes. Our results provide a platform for exploring bimetallic Co and V-based oxides, hydroxides, and sulfides nanostructures as promising energy storage materials in the future.
ACS applied materials & interfaces, 2017
A general synthetic methodology is reported to grow ultrafine cobalt-based nanoparticles (NPs, 2-7 nm) within high-surface-area mesoporous carbon (MC) frameworks. Our design strategy is based on colloidal amphiphile (CAM) templated oxidative self-polymerization of dopamine. The CAM templates consisting of a hydrophobic silica-like core and a hydrophilic PEO shell can coassemble with dopamine and template its self-polymerization to form polydopamine (PDA) nanospheres. Given that PDA has rich binding sites such as catechol and amine to coordinate metal ions (e.g., Co(2+)), PDA nanospheres containing Co(2+) ions can be converted into hierarchical porous carbon frameworks containing ultrafine metallic Co NPs (Co@MC) using high-temperature pyrolysis. The CAM templates offer strong "nanoconfinements" to prevent the overgrowth of Co NPs within carbon frameworks. The yielded ultrafine Co NPs have an average size of <7 nm even at a very high loading of 65 wt %. Co@MC can be furt...
Journal of Power Sources, 2014
A facile hydrothermal process with hexadecyltrimethyl ammonium bromide (CTAB) as the soft template is proposed to tune the morphology and size of cobalt hydroxide (Co(OH) 2 ). Monodisperse b-phase Co(OH) 2 nanowires with uniform size are obtained by controlling the CTAB content and the reaction time. Due to the uniform well-defined morphology and stable structure, the Co(OH) 2 nanowires material exhibits high capacitive performance and long cycle life. The specific capacitance of the Co(OH) 2 nanowires electrode is 358 F g À1 at 0.5 A g À1 , and even 325 F g À1 at 10 A g À1 . The specific capacitance retention is 86.3% after 5000 chargeedischarge cycles at 2 A g À1 . Moreover, the asymmetric supercapacitor is assembled with Co(OH) 2 nanowires and nitrite acid treated activated carbon (NTAC), which shows an energy density of 13.6 Wh kg À1 at the power density of 153 W kg À1 under a high voltage of 1.6 V, and 13.1 Wh kg À1 even at the power density of 1.88 kW kg À1 .