Symmetric Pseudocapacitor Research Articles

Hierarchical nickel phosphide/carbon nanofibers for high performance pseudocapacitors

Nickel phosphide (Ni3P)/Carbon nanofibers (CNFs) with controllable sizes and morphologies are synthesized using micro arc oxidation method combined with thermochemical vapor deposition, with adjustment of different annealing temperatures to control the dimension of CNFs. In this study, we report the in situ formation of transition metal phosphide nanoparticles through the conversion of 1D Ni5TiO7 nanowires. This fabrication strategy ensures the high growth density of CNFs. The initially formed Ni3P nanoparticles boost the catalytic growth of CNFs, which feature a high specific surface area and excellent conductivity. Together with redox electrolyte, the specific capacitance of Ni3P/CNFs based pseudocapacitor (PC) is 114.6 mF cm−2 at a scan rate of 10 mV s−1 and maintains 95.0 % of initial capacity after 10,000 cyclic charging/discharging test. Moreover, such composite based symmetric PCs offer an energy density of as high as 31.6 Wh kg−1 accompanied with a power density of 10.3 kW kg−1. The performance of formed PC devices is comparable to market-available (Li-/Na-) batteries. Therefore, Ni3P/CNFs composite film is a suitable capacitor electrode material for constructing high performance symmetric carbon material based PCs.

A novel benzoquinone‐azo linked polymer‐based active electrode material for high‐performance symmetric pseudocapacitors

AbstractPseudocapacitors (PSCs) have attracted researcher's attention due to their potential electrochemical performance as the power source for electronic devices. However, to maintain the high electrochemical properties of pseudocapacitive materials becomes critical. Therefore, the active electrode materials design and synthesis is a challenging task. To tackle these problems, herein, we rationally designed new polymer based on benzoquinone with azo linker. The polymer AZO‐BQ‐P was synthesized and tested for their energy storage applications in combination with graphite foil (GF). In three‐electrode supercapacitor (SC) device, the AZO‐BQ‐P/GF electrode exhibits excellent specific capacitance (Csp) of about 306.27 F g−1 at 0.5 A g−1 current density and higher cycling stability. The pseudocapacitive performance of SC cells result from synergistic effect of AZO‐BQ‐P and GF and due to faster electrolyte ion diffusion and increased availability at electrode/electrolyte interfaces. Furthermore, AZO‐BQ‐P/GF electrode was employed to fabricate two‐electrode AZO‐BQ‐P/GF//AZO‐BQ‐P/GF symmetric SC device. The optimal SSC device shows a Csp reaching 200 F g−1 at 0.5 A g−1, which is an impressive value. Also, it exhibits remarkable cycling stability with 86.18% Csp retention after 5000 galvanostatic charging–discharging (GCD) cycles at 3 A g−1. The SSC device applying AZO‐BQ‐P/GF electrode delivers an excellent energy density (ED) of 25.00 Wh kg−1 at 900.00 W kg−1 power density (PD). Thus, the novel polymer design offers efficient electrode materials to enhance the pseudocapacitive electrochemical performance of the SSC device. This concept can be extended for fabricating other electrochemical systems and accelerate its applications for modern electronic devices.

A 2.5V In-Plane Flexi-Pseudocapacitor with Unprecedented Energy and Cycling Efficiency for All-Weather Applications.

As electronic devices for aviation, space, and satellite applications become more sophisticated, built-in energy storage devices also require a wider temperature spectrum. Herein, an all-climate operational, energy and power-dense, flexible, in-plane symmetric pseudocapacitor is demonstrated with utmost operational safety and long cycle life. The device is constructed with interdigital-patterned laser-scribed carbon-supported electrodeposited V5O12·6H2O as a binder-free electrode and a novel high-voltage anti-freezing water-in-salt-hybrid electrolyte. The anti-freezing electrolyte can operate over a wide temperature range of -40-60°C while offering a stable potential window of ≈2.5V. The device undergoes rigorous testing under diverse environmental conditions, including rapid and regular temperature and mechanical transition over multiple cycles. Additionally, detailed theoretical simulation studies are performed to understand the interfacial interactions with the active material as well as the local behavior of the anti-freeze electrolyte at different temperatures. As a result, the all-weather pseudocapacitor at 1Ag-1 shows a high areal capacitance of 234.7mFcm-2 at room temperature and maintains a high capacitance of 129.8mFcm-2 even at -40°C. Besides, the cell operates very reliably for over 80950 cycles with a capacitance of 25.7mFcm-2 at 10Ag-1 and exhibits excellent flexibility and bendability under different stress conditions.

Fabrication of high-performance symmetric pseudocapacitor by synthesizing ionic liquid-modified graphene/MoS2 NS binary electrode

The combination of graphene with metal sulfides has always been getting attention from researchers due to the compatibility in their two-dimensional structure with active sites on their edges and their exceptional optical, magnetic, and physiochemical properties. Herein, we synthesize highly efficient pseudocapacitive electrode material using ionic liquid-modified graphene (IL-rGO) and ultrathin MoS2 nanosheets (MoS2 NS). The electrochemical properties of graphene were tuned by modifying its surface with green solvents such as ionic liquids. Modification of the graphene surface with IL increased the number of active sites at the edges, and provided a more compact arrangement to the graphene layers which enabled them to accommodate MoS2 NSs between them. Among the synthesized binary electrodes, 1.5 g IL-modified rGO loaded with 15 wt% of MoS2 NS electrode, the PIRM15 binary electrode, exhibits a high specific capacitance of 955 F/g. TEM micrographs of the PIRM15 electrode delineated the intercalation of MoS2 NSs between the graphene layers. The PIRM15 electrode displayed 93.7 % of pseudocapacitance and 6.7 % electrical double-layer capacitance. The symmetric pseudocapacitor integrated with the PIRM15 binary electrode possesses 97 % capacitance retention and 87 % coulombic efficiency at 0.008 A. The pseudocapacitor's calculated energy and power densities are 25 Wh/kg and 3333 W/kg at a current of 0.003 A and 0.05 A, respectively.

Archetypical 2D sheet-like Cu2MoS4 for all-solid-state symmetric pseudocapacitors with ultra-steady performance efficiency

2D sheet-like Cu2MoS4 with rich phase purity, low crystallinity and high surface area possesses novel physicoelectrochemical characteristics for application in all-solid-state symmetric pseudocapacitors with remarkable performance efficiency.

Two birds with one stone: cobalt/silicon species encapsulated in MOF-derived nitrogen-doped carbon as an integrated electrode for next-generation symmetric pseudocapacitors with energy density over 100 W h kg−1

The concept of “two birds with one stone” is employed to fabricate a symmetric pseudocapacitor. The Si/Co with optimized content in the MOF-derived N-doped carbon-based electrode can work at an ultra-large potential window of −1.0 to 0.4 V.

Reversible surface reconstruction of Na3NiCO3PO4: A battery type electrode for pseudocapacitor applications

Recently, a new class of mixed polyanionic compounds with general formula Na3MPO4CO3 (M = Ni, Mn, Fe, Co, Cu), discovered through high-throughput computations have attracted much attention for its secondary battery applications and safety aspects. Here, we combine electrochemical measurements with inductively coupled plasma-optical emission spectrometer (ICP-OES), energy-dispersive X-ray (EDX), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), and an ab-initio DFT approach to unravel the dynamic self-limiting surface restructuring of Na3NiCO3PO4 in aqueous 1 M KOH/NaOH electrolyte. The etching of lattice CO32-, PO43- and Na serves as the key to trigger the surface reconstruction. This work establishes a fundamental understanding of the pseudocapacitance mechanism associated with surface self-reconstruction of mixed polyanionic compounds. The reconstruction-derived self-limiting dense Ni(OH)2 layers at the surface and its oxidation to NiOOH at anodic potentials can be attributed to the observed high-performance pseudocapacitive behavior. The surface reconstructed Na3NiCO3PO4 electrode exhibits high specific capacitance (2378.2 F g−1 at 1 A g−1). The assembled symmetric pseudocapacitor delivers a high energy density (57.2 Wh kg−1), power density (1500 W kg−1) at 1 Ag-1 and long cycle life (13000 cycles) with 100% retention.

One-Step Hydrothermal Synthesis of Nitrogen-Doped Reduced Graphene Oxide/Hausmannite Manganese Oxide for Symmetric and Asymmetric Pseudocapacitors.

In this paper, the pseudocapacitive performance of nitrogen-doped and undoped reduced graphene oxide/tetragonal hausmannite nanohybrids (N-rGO/Mn3O4 and rGO/Mn3O4) synthesized using a one-pot hydrothermal method is reported. The nanohybrid electrode materials displayed exceptional electrochemical performance relative to their respective individual precursors (i.e., reduced graphene oxide (rGO), nitrogen-doped reduced graphene oxide (N-rGO), and tetragonal hausmannite (Mn3O4)) for symmetric pseudocapacitors. Among the two nanohybrids, N-rGO/Mn3O4 displayed greater performance with a high specific capacitance of 345 F g–1 at a current density of 0.1 A g–1, excellent specific energy of 12.0 Wh kg–1 (0.1 A g–1), and a high power density of 22.5 kW kg–1 (10.0 A g–1), while rGO/Mn3O4 demonstrated a high specific capacitance of 264 F g–1 (0.1 A g–1) with specific energy and power densities of 9.2 Wh kg–1 (0.1 A g–1) and 23.6 kW kg–1 (10.0 A g–1), respectively. Furthermore, the N-rGO/Mn3O4 nanohybrid exhibited an impressive pseudocapacitive performance when fabricated in an asymmetric configuration, having a stable potential window of 2.0 V in 1.0 M Na2SO4 electrolyte. The nanohybrid showed excellent specific energy and power densities of 34.6 Wh kg–1 (0.1 A g–1) and 14.01 kW kg–1 (10.0 A g–1), respectively. These promising results provide a good substance for developing novel carbon-based metal oxide electrode materials in pseudocapacitor applications.

Core-sheath 3D printing of highly conductive and MoS2-loaded electrode with pseudocapacitive behavior

Pseudocapacitance holds great promise for energy density improvement of supercapacitors. However, how to enable a pseudocapacitor with combined feature of high mass loading of pseudocapacitive material, efficient ion/electron transport, as well as facile and scalable manufacturing, still remains a significant challenge. Herein, we demonstrated an efficient and scalable extrusion-based core-sheath 3D printing strategy for directly and controllably constructing pseudocapacitive carbon nanotube (CNT)- MoS2 (CM)-CNT/graphene electrode, with high mass loading up to 55% and uniform distribution of MoS2, hierarchically porous configuration and highly interconnected conductive network framework built by coupling graphene scaffold located in shell layer and CNTs situated in core layer. The unique architecture featuring adequate channels and pathways can act as a “superhighway” for ultrafast ion diffusion and electron transport throughout the entire device, thereby enabling fast kinetics of Faradaic reactions and abundant availability of electrochemical active sites. A symmetric pseudocapacitor assembled with 3D-printed electrode and in situ electrospun poly(vinylidene fluoride) (PVDF) nanofiber separator delivered high specific capacitance (558 mF cm−2) and energy density (49 µWh cm−2), remarkable cycling stability (87% after 8000 cycles), and superior capacity even at large electrode thickness. This work has shed light on new strategies for designing and fabricating high-performance pseudocapacitors toward future uses.

Pseudocapacitive charge storage in layered oxides SrLaFe1−xCoxO4−δ (x = 0–1)

Pseudocapacitive energy storage has been demonstrated for three materials belonging to a family of layered oxides. This work is the first report on the observation of charge-storage properties in this family of materials that feature 2-dimensional layers, consisting of MO6 units (M = transition metal). The spaces between layers are occupied by alkaline-earth or rare-earth metals. Systematic trends have been demonstrated, where the charge-storage properties are enhanced as a function of Co-concentration, structural distortion and oxygen-deficiency in SrLaFe1−xCoxO4−δ. Symmetric pseudocapacitor cells based on these materials show substantial specific capacitance, energy density and power density. They are also remarkably stable and retain their charge storage capacity even after 1000 cycles of charge-discharge. The observation of pseudocapacitive charge-storage properties in these materials indicates the potential of this class of layered oxides for utilization in energy storage.

3D Network V2O5 Electrodes in a Gel Electrolyte for High-Voltage Wearable Symmetric Pseudocapacitors

A 3D network composed of V2O5 nanofibers was manufactured on a novel conductive printing paper [urea-LiClO4-PVA (ULP) deep eutectic solvent gel-doped graphite/printing paper, U-paper] for use as electrodes linked with a ULP neutral gel electrolyte for 3D network V2O5 wearable symmetric pseudocapacitors (WSSCs). The function of the ULP gel is not only that it can be doped into the conductive ink to decrease the resistance of the conductive printing paper but also that it increases the stability of V2O5-based electrodes. Moreover, 3D network V2O5 WSSCs containing the ULP gel can support high operating voltages of 4.0 V with great specific capacitance (160 F/g) and offer a high energy density (355 W h/kg at 0.2 kW/kg). The 3D network V2O5 WSSCs exhibit a superior cycling stability/durability after 5000 cycles (capacitance retention of ∼91%). Operando X-ray absorption spectroscopy experiments show the reversibility and pseudocapacitive properties of V2O5 from the ULP gel and offer the information of the oxidation states of vanadium during charge-discharge cycles. The 3D network V2O5 WSSCs with the ULP gel electrolyte show great potential prospective candidates for smarter 3D wearable energy-storage devices and Internet-of-Things applications.

MnO2-deposited lignin-based carbon nanofiber mats for application as electrodes in symmetric pseudocapacitors

Low-cost, high-performance electrodes are highly attractive for practical supercapacitor applications. MnO2-deposited carbon nanofiber mats (MnO2-CNFMs) are prepared for use as binder-free supercapacitor electrodes. MnO2 is deposited on the mats in situ by hydrothermally decomposing aqueous KMnO4, leading to the formation of nanocrystals of MnO2. The MnO2-CNFM electrode produced with 38.0μmol KMnO4 (this electrode) shows a high specific capacitance of ~171.6F·g−1 at a scan rate of 5mV·s−1. Moreover, a symmetric supercapacitor with the electrode exhibits a specific capacitance of 67.0F·g−1, an energy density of 6.0Wh·kg−1 and a power density of 160W·kg−1 at a special current of 0.1A·g−1. Further, the symmetric supercapacitor displays excellent cycling stability, retains approximately 99% of the capacitance after 1000cycles. The simplicity and ease of preparation of the MnO2-CNFMs as well as their suitability for use in coin-type supercapacitor cells make them ideal for application in cost-effective and high-performance electrodes for supercapacitors.

Titanium Disulfide Coated Carbon Nanotube Hybrid Electrodes Enable High Energy Density Symmetric Pseudocapacitors

While electrochemical supercapacitors often show high power density and long operation lifetimes, they are plagued by limited energy density. Pseudocapacitive materials, in contrast, operate by fast surface redox reactions and are shown to enhance energy storage of supercapacitors. Furthermore, several reported systems exhibit high capacitance but restricted electrochemical voltage windows, usually no more than 1 V in aqueous electrolytes. Here, it is demonstrated that vertically aligned carbon nanotubes (VACNTs) with uniformly coated, pseudocapacitive titanium disulfide (TiS2 ) composite electrodes can extend the stable working range to over 3 V to achieve a high capacitance of 195 F g-1 in an Li-rich electrolyte. A symmetric cell demonstrates an energy density of 60.9 Wh kg-1 -the highest among symmetric pseudocapacitors using metal oxides, conducting polymers, 2D transition metal carbides (MXene), and other transition metal dichalcogenides. Nanostructures prepared by an atomic layer deposition/sulfurization process facilitate ion transportation and surface reactions to result in a high power density of 1250 W kg-1 with stable operation over 10 000 cycles. A flexible solid-state supercapacitor prepared by transferring the TiS2 -VACNT composite film onto Kapton tape is demonstrated to power a 2.2 V light emitting diode (LED) for 1 min.

Electrochemical Behaviour of Lithium, Sodium and Potassium Ion Electrolytes in a Na0.33V2O5 Symmetric Pseudocapacitor with High Performance and High Cyclic Stability

AbstractA high‐performance symmetric supercapacitor was fabricated using a Na0.33V2O5 nanocomposite synthesized by means of a simple co‐precipitation technique. The structural and morphological investigation showed that the synthesized Na0.33V2O5 nanocomposite exhibited a monoclinic structure with a nanorod‐like morphology. The electrochemical properties of the Na0.33V2O5 symmetric supercapacitor were studied utilizing three different aqueous electrolytes, such as 1 M of LiCl, NaCl and KCl, respectively. Interestingly, the fabricated Na0.33V2O5 symmetric supercapacitors exhibited excellent electrochemical capacitance behaviour in all the electrolytes with a maximum specific capacitance value of 168 F g−1 in 1 M LiCl, 146 F g−1 in 1 M NaCl and 132 F g−1 in 1 M KCl electrolytes at 0.5 A g−1 discharge current density. In addition, Na0.33V2O5 symmetric supercapacitors demonstrated an excellent cyclic stability in 1 M NaCl electrolyte with high capacitance retention of approximately 81 % after 50 000 charge/discharge cycles.

High-performance Mn3O4/onion-like carbon (OLC) nanohybrid pseudocapacitor: Unravelling the intrinsic properties of OLC against other carbon supports

The electrochemical performance of the tetragonal hausmannite Mn3O4, when embedded on various carbon materials, onion-like carbon (OLC), carbon nanotubes (CNT), reduced graphene oxide (RGO) and activated carbon (AC) (i.e., OLC/Mn3O4, CNT/Mn3O4, GO/Mn3O4, and AC/Mn3O4), has been investigated as electrode material for symmetric and asymmetric pseudocapacitor device. The nanohybrid electrode materials demonstrated higher electrochemical performance (in terms of specific capacitance and rate capability as energy storage devices) compared to the pure Mn3O4. The OLC/Mn3O4-based symmetric pseudocapacitor device exhibited higher specific capacitance of 195 F g−1, specific energy of 4.3 Wh kg−1 and power density of 52 kW kg−1 compared to other carbon nanohybrid materials studied. From the symmetric experiments, the best-performing OLC/Mn3O4 nanohybrid has been further explored as high-voltage asymmetric pseudocapacitor, with maximum energy and power densities of ca. 19 Wh kg−1 (at 0.1 A g−1) and 45 kW kg−1 (at 10 A g−1) respectively. The high-performance of the OLC-based system compared to the other carbon systems is ascribed to the combined unique intrinsic properties of the OLC; high electrical conductivity, highly accessible outer surface and large interparticle pore volumes. The above properties have ensured OLC/Mn3O4 nanohybrid as a suitable candidate for the high-voltage asymmetric pseudocapacitor device.

Electrochemical Fabrication of Monolithic Electrodes with Core/Shell Sandwiched Transition Metal Oxide/Oxyhydroxide for High-Performance Energy Storage.

Transition metal oxides/oxyhydroxides (TMOs) are promising high-capacity materials for electrochemical energy storage. However, the low rate and poor cyclability hinder practical applications. In this work, we developed a general electrochemical route to fabricate monolithic core/shell sandwiched structures, which are able to significantly improve the electrochemical properties of TMO electrodes by electrically wiring the insulating active materials and alleviating the adverse effects caused by volume changes using engineered porous structures. As an example, a lithium ion battery anode of porous MnO sandwiched between CNT and carbon demonstrates a high capacity of 554 mAh g-1 even after 1000 cycles at 2 A g-1. An all-solid-state symmetric pseudocapacitor consisting of CNT@MnOOH@polypyrrole exhibits a high specific capacitance of 148 F g-1 and excellent capacitance retention (92% after 10000 cycles at 2 A g-1). Several other examples and applications have further confirmed the effectiveness of improving the electrochemical properties by core/shell sandwiched structures.

Graphene oxide-modified nickel (II) tetra-aminophthalocyanine nanocomposites for high-power symmetric pseudocapacitor

Pseudocapacitive properties of nickel (II) tetraaminophthalocyanine-modified graphene oxide sheets (GO/NiTAPc) composites have been studied. Microscopic and spectroscopic analysis of the GO/NiTAPc electrode material with its precursors (GO and NiTAPc) were examined using Field Emission Scanning Electron Microscopy (FESEM), High-Resolution Transmission Electron Microscopy (HRTEM), X-ray Diffraction (XRD) and UV-vis. Electrochemical properties of GO/NiTAPc composite, GO and NiTAPc electrode materials were examined using Cyclic Voltammetry (CV), Charge-Discharge (CD), and Electrochemical Impedance Spectroscopy (EIS), and are reported. A symmetrical device, fabricated with the Ni foam, of GO/NiTAPc composite showed a large specific capacitance (Csp) of 163Fg−1 and maximum specific energy density (Esp) of 3.6Whkg−1, which are much higher than those of its individual precursors of NiTAPc (60F g−1 and 1.3Whkg−1) and GO (15Fg−1 and 0.3Whkg−1) at 0.1Ag−1. The GO/NiTAPc symmetric pseudocapacitor device showed high power density (Psp) of 140.0kWkg−1 with superior retention of capacitance when subjected to a long-hour (50h) voltage-holding test. This excellent energy storage performance of the composite materials is advantageous for the potential development of aqueous-based pseudocapacitors fabricated from metallophthalocyanine (MPc) complexes (N4-macrocyclic metal compounds) and their derivatives.

Ultrahigh-Power Pseudocapacitors Based on Ordered Porous Heterostructures of Electron-Correlated Oxides.

Nanostructured transition‐metal oxides can store high‐density energy in fast surface redox reactions, but their poor conductivity causes remarkable reductions in the energy storage of most pseudocapacitors at high power delivery (fast charge/discharge rates). Here it is shown that electron‐correlated oxide hybrid electrodes made of nanocrystalline vanadium sesquioxide and manganese dioxide with 3D and bicontinuous nanoporous architecture (NP V2O3/MnO2) have enhanced conductivity because of metallization of electron‐correlated V2O3 skeleton via insulator‐to‐metal transition. The conductive V2O3 skeleton at ambient temperature enables fast electron and ion transports in the entire electrode and facilitates charge transfer at abundant V2O3/MnO2 interface. These merits significantly improve the pseudocapacitive behavior and rate capability of the constituent MnO2. Symmetric pseudocapacitors assembled with binder‐free NP V2O3/MnO2 electrodes deliver ultrahigh electrical powers (up to ≈422 W cm23) while maintaining the high volumetric energy of thin‐film lithium battery with excellent stability.

The Effects of Morphology Re-Arrangements on the Pseudocapacitive Properties of Mesoporous Molybdenum Disulfide (MoS2) Nanoflakes

Mesoporous molybdenum disulfide (MoS2) with different morphologies have been prepared via hydrothermal method using different solvents, water or water/acetone mixture. The MoS2 obtained with water alone gave a graphene-like nanoflakes (g-MoS2) while the other with water/acetone (1:1 ratio) gave a hollow-like morphology (h-MoS2). Both materials are modified with carbon nanospheres as conductive material and investigated as symmetric pseudocapacitors in aqueous electrolyte (1 M Na2SO4 solution). The physico-chemical properties of the MoS2 layered materials have been interrogated using the surface area analysis (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, fourier-transform infrared (FTIR) spectroscopy, and advanced electrochemistry including cyclic voltammetry (CV), galvanostatic cycling with potential limitation (GCPL), repetitive electrochemical cycling tests, and electrochemical impedance spectroscopy (EIS). Interestingly, a simple change of synthesis solvents confers on the MoS2 materials different morphologies, surface areas, and structural parameters, correlated by electrochemical capacitive properties. The g-MoS2 exhibits higher surface area, higher capacitance parameters (specific capacitance of 183 F g−1, maximum energy density of 9.2 Wh kg−1 and power density of 2.9 kW kg−1) but less stable electrochemical cycling compared to the h-MoS2. The findings show promises for the ability to tune the morphology of MoS2 materials for enhanced energy storage.

Symmetric pseudocapacitors based on molybdenum disulfide (MoS2)-modified carbon nanospheres: correlating physicochemistry and synergistic interaction on energy storage

Flower-like MoS2modified with carbon nanospheres (CNS) displays energy-storage capability when used as an aqueous symmetric pseudocapacitor.