Electrochemical Pseudocapacitor Materials Research Articles

Porous spherical NiO@NiMoO4@PPy nanoarchitectures as advanced electrochemical pseudocapacitor materials

In this work, a rational design and construction of porous spherical NiO@NiMoO4 wrapped with PPy was reported for the application of high-performance supercapacitor (SC). The results show that the NiMoO4 modification changes the morphology of NiO, and the hollow internal morphology combined with porous outer shell of NiO@NiMoO4 and NiO@NiMoO4@PPy hybrids shows an increased specific surface area (SSA), and then promotes the transfer of ions and electrons. The shell of NiMoO4 and PPy with high electronic conductivity decreases the charge-transfer reaction resistance of NiO, and then improves the electrochemical kinetics of NiO. At 20Ag−1, the initial capacitances of NiO, NiMoO4, NiO@NiMoO4 and NiO@NiMoO4@PPy are 456.0, 803.2, 764.4 and 941.6Fg−1, respectively. After 10,000 cycles, the corresponding capacitances are 346.8, 510.8, 641.2 and 904.8Fg−1, respectively. Especially, the initial capacitance of NiO@NiMoO4@PPy is 850.2Fg−1, and remains 655.2Fg−1 with a high retention of 77.1% at 30Ag−1 even after 30,000 cycles. The calculation result based on density function theory shows that the much stronger Mo-O bonds are crucial for stabilizing the NiO@NiMoO4 composite, resulting in a good cycling stability of these materials.

Amorphous Niobium Oxide Thin Film As Anode for High Rate Lithium Ion Battery

Electrochemical pseudo-capacitor materials that can deliver high power and store high capacity energy for applications that required faster rate performance than traditional energy storage battery are needed. Amorphous Nb2O5 has been evaluated as a pseudo-capacitor. Amorphous thin film (550 nm) was synthesized by RF magnetron sputtering. The morphology of the Nb2O5 nanoparticle thin films was smooth as evaluating in field emission scanning electron microscope (FE-SEM) with nanoparticle size ranged between 5 and 15 nm. A cross-sectional FE-SEM image shows thickness was approximately 550 nm with excellent adhesion to the SS substrates. XPS revealed that the as-deposited materials are Nb2O5. To understand the electrochemical redox reactions, cyclic voltammetry (CV) and galvanostatic discharge-charge (GDC) experiments were performed at different rates. The CVs were performed at scan rates of 0.1, 1, 2, and 5 mV/s. For example, for the scan rate at 1 mV/s a sharp peak current is observed at ~0.85 V during the first cycle which has been assigned to the formation of the solid electrolyte interface (SEI) and reduction of Nb+5 to Nb+4. As the cathodic sweep continues to zero volt no conversion reaction took place. The anodic sweep shows two broad and weak peak currents at ~0.7 and ~1.5 V. During the second cycle, the peak current at ~0.85 V disappeared which is typical of irreversibility and loss of capacity in the first cycle. All subsequent cycles were smooth with quasi rectangular CV curves which indicated the pseudo-capacitive characteristics of amorphous Nb2O5. This is opposite to sharp peak currents typically observed in CV that are characteristics of battery electrodes. Ex-situ XPS were performed on the sample stopped at 1.0 V during the reverse potential sweep and 1.84 V during the forward potential sweep. A very thick SEI layer was observed when the sample was stopped and analyzed at 1.0 V. NbOx was observed after fifteen minutes of sputtering at 1 KeV Ar+ and Nb+4/+5 after 90 min of sputtering. The SEI is composed of carbonates (Li2CO3), aliphatic carbon species, and fluorides (LiF). The capacity observed during the first cycle was 436 mAh/g at C/3 rate. After 100 cycles, the coulumbic efficiency was maintained at 100% and the capacity retention was 160 mAh/g. The materials responded very well to different cycling rates. Figure 1

Hierarchical Co3O4@ZnWO4 core/shell nanostructures on nickel foam: Synthesis and electrochemical performance for supercapacitors

To improve the electrochemical properties of Co3O4 for supercapacitors application, a hierarchical Co3O4@ZnWO4 core/shell nanowire arrays (NWAs) material is designed and synthesized successfully via a facile two-step hydrothermal method followed by the heat treatment. Co3O4@ZnWO4 NWAs exhibits excellent electrochemical performances with areal capacitance of 4.1Fcm−2 (1020.1Fg−1) at a current density of 2mAcm−2 and extremely good cycling stability (99.7% of the initial capacitance remained even after 3000 cycles). Compared with pure Co3O4 electrodes, the results prove that this unique hierarchical hybrid nanostructure and reasonable assembling of two electrochemical pseudocapacitor materials are more advantageous to enhance the electrochemical performance. Considering these remarkable capacitive behaviors, the hierarchical Co3O4@ZnWO4 core/shell NWAs nanostructure electrode can be revealed promising for high-performance supercapacitors.

In-Situ Fabrication of Graphene Oxide Hybrid Ni-Based Metal-Organic Framework (Ni-MOFs@GO) with Ultrahigh Capacitance as Electrochemical Pseudocapacitor Materials.

This paper reports a series of novel Ni-based metal-organic framework (Ni-MOFs) prepared by a facile solvothermal process. The synthetic conditions have great effects on the Ni-MOFs morphologies, porous textures, and their electrochemical performance. Improved capacitance performance was successfully realized by the in-situ hybrid of Ni-MOFs with graphene oxide (GO) nanosheets (Ni-MOFs@GO). The pseudocapacitance of ca. 1457.7 F/g for Ni-MOFs obtained at 180 °C with HCl as the modulator was elevated to ca. 2192.4 F/g at a current density of 1 A/g for the Ni-MOFs@GO with GO contents of 3 wt %. Additionally, the capacitance retention was also promoted from ca. 83.5% to 85.1% of its original capacitance at 10 A/g even after 3000 cycles accordingly. These outstanding electrochemical properties of Ni-based MOF materials may be related to their inherent characteristics, such as the unique flower-like architecture and fascinating synergetic effect between the Ni-MOFs and the GO nanosheets.

Synthesis and properties of morphology controllable copper sulphide nanosheets for supercapacitor application

CuS nanosheets and their various assembled forms prepared by dealloying a Ti-Cu amorphous alloy have been investigated as electrochemical pseudocapacitor materials for energy storage applications. The properties of the assembled forms of the CuS nanosheets are determined by using the concentration of H2SO4 employed in the dealloying process. Spherical clusters composed of CuS nanosheets were fabricated by this process. These clusters have the highest specific surface areas provided by the nanosheets and exhibit high electrochemical and charge storage-release performances. The CuS spherical clusters showed a high specific capacitance of ∼276Fg−1 (at a scan rate of 5mVs−1 in cyclic voltammetry tests) and ∼713Fg−1 (at a charge-discharge current of 1.0Ag−1). The high pseudocapacitive performance can be attributed to the highest specific surface area in our case and absence of volume change of the nanosheets. These results suggest the importance of a rational nanostructure design for high-performance energy applications.

Excellent Electrochemical Performance Hierarchical Co3O4@Ni3S2 core/shell nanowire arrays for Asymmetric Supercapacitors

Three-dimensional hierarchical Co3O4@Ni3S2 core/shell nanowire arrays were designed and fabricated on nickel foam via a facile two-step route for supercapacitor applications. Compared with the pristine Co3O4 nanowire arrays and Ni3S2 nanosheets, the hierarchical nanostructure demonstrates much more excellent capacitive behaviors. The Co3O4@Ni3S2 electrode exhibited an ultrahigh specific capacitance of 1710Fg−1 at 1Ag−1 and 1474Fg−1 at 10Ag−1. An asymmetric supercapacitor based on Co3O4@Ni3S2 core/shell nanowire arrays on nickel foam as the positive electrode and activated carbon (AC) as negative electrode was successfully assembled. A specific capacitance of 126.6Fg−1 at 1Ag−1 (retaining 83.5% capacity after 5000 cycles at a current density of 2Ag−1) and an outstanding energy density of 44.9 Wh kg−1 was achieved. The remarkable electrochemical properties could be attributed to the unique hierarchical architectures of Co3O4@Ni3S2 core–shell nanowire arrays on 3D on nickel foam and a rational combination of two electrochemical pseudocapacitor materials. The results indicate that our asymmetric supercapacitors have great potential in energy storage device applications.

Well-Defined, Nanostructured, Amorphous Metal Phosphate as Electrochemical Pseudocapacitor Materials with High Capacitance

Amorphous micro/nanomaterials are very important members of the noncrystalline materials family and have attracted tremendous interest and exhibited their excellent performance in the application of electrical catalysis and energy storage. The complexity of this research field is limited ultimately by the lack of a facile and practicable strategy to synthesize well-defined ultrathin amorphous nanomaterials. Here, for the first time, we report the random attachment of Co3(PO4)2 amorphous nanoplate building blocks into ultrathin nanosheets with dimensions on the micrometer scale. We found the structure of obtained Co3(PO4)2 amorphous nanosheet can be converted into nanowire by a split process. On the basis of our observations, an assemble-split mechanism for synthesizing ultrathin amorphous nanostructure is proposed. Furthermore, our strategy is general and can be used to prepare other metal phosphate amorphous ultrathin nanostructures. As a demonstration, the synthesized Co3(PO4)2 ultrathin nanowire has be...

Pine needle β-Co(OH)2 grown on Ni foam substrate for high specific capacitance and good cycling stability as advanced electrochemical pseudocapacitor materials

Pine needle β-Co(OH)2 grown on Ni foam (β-Co(OH)2/NF) substrate was fabricated via a simple hydrothermal process for improved electrochemical properties. The sample has been characterized by FTIR, XRD, TG, SEM, TEM, cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance study. It exhibits high specific capacitance of 1215F/g and 790F/g at current density of 5 and 50A/g, respectively. The capacitance can retain about 91.4% after 1000 charge-discharge cycles at a current density of 50A/g. The β-Co(OH)2/NF has high specific capacitance and long cycle stability, which makes it suitable for supercapacitor application.

CoMoO4·0.9H2O nanorods grown on reduced graphene oxide as advanced electrochemical pseudocapacitor materials

In this work, one-dimensional CoMoO4·0.9H2O nanorods grown on reduced graphene oxide hybrid composites (CoMoO4·0.9H2O–rGO) with good electrochemical properties have been synthesized by a simple and environmentally friendly hydrothermal synthesis procedure. The conductive graphene not only improves the electron conductivity of the overall electrode but also provides strong synergistic effects with Faradaic pseudo-capacitance (CoMoO4·0.9H2O). Meanwhile, rGO can act as a buffer for the volume change, which can provide an assurance for better cycling performance of the CoMoO4·0.9H2O–rGO hybrid composites. An exceptionally high specific capacitance of 802.2 F g−1 at a current density of 1 A g−1 and good cycle stability with capacitance retention of ∼86.3% after 5000 cycles is obtained for the CoMoO4·0.9H2O–rGO composites. The remarkable electrochemical performance can make the CoMoO4·0.9H2O–rGO composites one of the most competitive electrode materials for electrochemical energy storage.

β-Ni(OH)2 nanosheets grown on graphene as advanced electrochemical pseudocapacitor materials with improved rate capability and cycle performance

Nanosheets composite consisting of β-Ni(OH)2 and reduction graphene oxide (β-Ni(OH)2/RGO) was successfully synthesized by improved hydrothermal process as electrochemical capacitor materials. The β-Ni(OH)2/RGO composite was tested as positive electrode material in a KOH aqueous electrolyte. The results show that the sample exhibits a high specific capacitance of 1740.56F/g at a charge and discharge current density of 2.5A/g, and the specific capacitance of β-Ni(OH)2/RGO is as high as 1326F/g, even if the current density increase to 50A/g. What is more, it exhibits an excellent long cycle life along with 93.8% specific capacitance retained after 1000 charge/discharge cycles. This composite displays a great promise as electrode materials for supercapacitor.

NiO nanoflakes grown on porous graphene frameworks as advanced electrochemical pseudocapacitor materials

A NiO–graphene hybrid film with 3D hierarchically porous structure has been rationally designed and constructed through a series of controlled fabrication processes. Multilayered porous graphene sheet network with the pore size of several micrometers is created via a so-called “on-water spreading” method, which is facile, economical, efficient and scalable. Then, the cross-like NiO nanoflakes film is uniformly grown onto the porous graphene sheet framework by a chemical bath deposition. The NiO–graphene hybrid film exhibits specific capacitance of 540 F g−1 at 2 A g−1 with 80% capacitance retention after 2000 cycles in 2 M KOH aqueous solution, which is much higher than that achieved from the bare NiO nanoflakes film (370 F g−1, with 66% capacitance retention). Moreover, chronoamperometry and electrochemical impedance spectroscopy measurements reveal that the NiO–graphene hybrid demonstrates enhanced reaction kinetics with about only 50% of respond time for NiO/NiOOH reaction and 79% of charge-transfer resistance compared with those of the bare NiO film. The proposed strategy could offer an effective way to fabricate graphene-based electrode materials for applications in various energy-storage devices.

Amorphous nickel–boron and nickel–manganese–boron alloy as electrochemical pseudocapacitor materials

The nanoparticles of amorphous Ni–B and Ni–Mn–B alloys are synthesized and investigated as electrochemical pseudocapacitor materials for potential energy storage applications.

Amorphous nickel hydroxide nanospheres with ultrahigh capacitance and energy density as electrochemical pseudocapacitor materials

Among numerous active electrode materials, nickel hydroxide is a promising electrode in electrochemical capacitors. Nickel hydroxide research has thus far focused on the crystalline rather than the amorphous phase, despite the impressive electrochemical properties of the latter, which includes an improved electrochemical efficiency due to disorder. Here we demonstrate high-performance electrochemical supercapacitors prepared from amorphous nickel hydroxide nanospheres synthesized via simple, green electrochemistry. The amorphous nickel hydroxide electrode exhibits high capacitance (2,188 F g−1), and the asymmetric pseudocapacitors of the amorphous nickel hydroxide exhibit high capacitance (153 F g−1), high energy density (35.7 W h kg−1 at a power density of 490 W kg−1) and super-long cycle life (97% and 81% charge retentions after 5,000 and 10,000 cycles, respectively). The integrated electrochemical performance of the amorphous nickel hydroxide is commensurate with crystalline materials in supercapacitors. These findings promote the application of amorphous nanostructures as advanced electrochemical pseudocapacitor materials.

The rods-like manganese dioxide films grown on nickel foam for electrochemical capacitor applications

MnO2 films grown on nickel foam (NF) with a desirable 3D structure are investigated as electrochemical pseudocapacitor materials for potential energy storage applications. The prepared MnO2 films are characterized by X-ray diffraction, FT-IR and scanning electron microscopy. Results indicate that the products are typical hexagonal ɛ-MnO2 with a uniform nanorod structure. The electrochemical measurements showed that the MnO2 films with rods-like morphology have excellent electrochemical performances and its specific capacitance value as single electrode is up to 664 F g−1 at a discharge current density of 5.5 A g−1, which is higher than that of most reported corresponding materials. The specific capacitance retention ratio is 76.7% at the current density range from 5.5 to 30 A g−1. Furthermore, we found that the deposition conditions such as deposition potential and deposition mass have a pronounced effect on their electrochemical activities.

Facile synthesis and superior supercapacitor performances of Ni2P/rGO nanoparticles

Ni2P nanoparticles grown on reduced graphene oxide (rGO) were successfully synthesized via the low-temperature solid state reaction method and investigated as electrochemical pseudocapacitor materials for potential energy storage applications. The specific capacitance of the as-prepared Ni2P/rGO is 2266 F g−1 and the Ni2P/rGO composite also exhibits superior cycling performance when they are used as the capacitor materials. The as-prepared Ni2P/rGO sample demonstrates interesting supercapacitive properties with high capacitance and good cycling performance.

3D porous layered double hydroxides grown on graphene as advanced electrochemical pseudocapacitor materials

A 3D hybrid nickel-aluminum layered double hydroxide (NiAl-LDH)–graphene nanosheets (GNS) composite as a supercapacitor material has been fabricated by in situ deposition of LDH nanosheets on graphene oxide (GO) through a liquid phase deposition method. The results reveal that NiAl-LDH homogeneously grew on the surface of GNS as spacers to keep the neighboring sheets separate. Optimum effects could be achieved when feeding ratio, reaction time and temperature are tuned. The obtained porous GNS/NiAl-LDH composite exhibited high-capacitance performance with a specific capacitance of 1255.8 F g−1 at a current density of 1 A g−1 and 755.6 F g−1 at 6 A g−1, respectively. Moreover, the composite exhibited excellent cycling performance with an increase of 6% capacitance compared with the initial capacitance after 1500 cycle tests. Such high specific capacitance, rate capability and exceptional cycling ability of the composite offered great promise in energy storage device applications.

Hydrothermal Synthesis of β-Ni(OH)2 Nanoplates as Electrochemical Pseudocapacitor Materials

Hydrothermal Synthesis of β-Ni(OH)2 Nanoplates as Electrochemical Pseudocapacitor Materials

Block copolymer assisted synthesis of porous α-Ni(OH)2 microflowers with high surface areas as electrochemical pseudocapacitor materials

Porous α-Ni(OH)(2) microflowers are successfully synthesized via a one-step aqueous-phase reaction assisted by block copolymers under mild conditions. The electrochemical measurement demonstrates that the α-Ni(OH)(2) microflowers calcined at 200 °C are capable to deliver a specific capacity of 1551 F g(-1) in 6 M KOH solution, suggesting their high potential as a novel electrochemical pseudocapacitor.

Spherical α-Ni(OH)2 nanoarchitecture grown on graphene as advanced electrochemical pseudocapacitor materials

This work reports a new graphene-based composite for supercapacitor material, and the maximum specific capacitance of 1760.72 F g(-1) at a scan rate of 5 mV s(-1), with excellent cycling stability.

MoO 3 nanoparticles distributed uniformly in carbon matrix for supercapacitor applications

A highly uniform nanocomposite of MoO 3 and carbon with a weight ratio of 1:1 is prepared by employing a simple procedure of ball milling. Such composite as electrochemical pseudocapacitor materials for potential energy storage applications exhibits a high specific capacitance of ~ 179 F/g at a charge and discharge current density of 50 mA/g with excellent cycling ability over 1000 cycles. Compared with the capacitance of pure milled graphite (~ 22 F/g) and MoO 3 (< 10 F/g), an enhanced electrochemical performance of the composite with a weight ratio of 1:1 is attributed to its unique structure, in which MoO 3 nanoparticles (with a size range of 1–180 nm) are uniformly dispersed in an electrically conductive carbon host.