Synthesis and characterization of hierarchical Bi2MoO6/Polyaniline nanocomposite for all-solid-state asymmetric supercapacitor

High-performance aqueous rechargeable nickel//bismuth batteries with Bi2MoO6@rGO and Co0.5Ni0.5MoO4@rGO as electrode materials

Aqueous rechargeable nickel–bismuth batteries have surfaced as a prospective energy storage and conversion system because of their merits of good safety, high power density, and low cost.

High-performance Bi2O3-NC anodes through constructing carbon shells and oxygen vacancies for flexible battery-supercapacitor hybrid devices

Battery-supercapacitor hybrid (BSH) devices generally provide both high energy density and power density, but usually suffer from the serious electrochemical kinetics mismatch of cathodes and anodes mainly due to complex faradaic reactions of the unmatched battery-type electrodes used for charge storage, which inevitably degrade the rate capability and power density. To solve this, we propose a facile and efficient strategy of constructing carbon shells and oxygen vacancies. Oxygen-deficient Bi2O3 nanoflakes stabilized by N-doped carbon and supported on graphite fibers (GF@Bi2O3-NCs) were prepared to improve specific capacity, rate capability and cycling stability. The N/S-codoped carbon aerogels supported on graphite fibers (GF@NS-CAGs) provided a high capacitance of 312 F g-1 at 1 A g-1, which was mainly attributed to the microporous structure and high active N content. The flexible quasi-solid-state BSH device based on the GF@Bi2O3-NC anode and the GF@NS-CAG cathode with a stable voltage window of 2.3 V could deliver a remarkable capacity of 103 mA h g-1, an energy density of 118 W h kg-1 and capacity retention of 95.7% after 10 000 cycles, reflecting that this was a highly-efficient approach to develop high-performance flexible energy storage devices.

Photo-induced self-catalysis of nano-Bi2MoO6 for solar energy harvesting and charge storage

Photo-induced self-catalytic redox reaction of nano Bi₂MoO₆ for solar energy harvesting and pseudo-capacitance charge storage.

Construction of heterostructure based on hierarchical Bi2MoO6 and g-C3N4 with ease for impressive performance in photoelectrocatalytic water splitting and supercapacitor

This work demonstrates the formation of g-C₃N₄/Bi₂MoO₆ heterostructure for water splitting and supercapacitor; which shows highest PEC efficiency and symmetric device delivered a energy density and power density of 47 W h kg⁻¹ and 4.5 kW kg⁻¹.

Chemically grown bismuth-oxy-iodide (BiOI/Bi9I2) nanostructure for high performance battery-type supercapacitor electrodes

A dual phase bismuth oxyiodide (BiOI/Bi₉I₂) nanostructure battery type supercapacitor electrode is synthesized using chemical bath deposition (CBD) and the capacitance and energy/power density (ED/PD) reported.

Facile Chemical Synthesis and Potential Supercapattery Energy Storage Application of Hydrangea-type Bi2MoO6

Soft chemical synthesis is used to obtain a hydrangea-type bismuth molybdate (Bi2MoO6) supercapattery electrode that demonstrates considerable energy/power density and cycling life. Structure and morphology studies, initially, reveal a phase-pure polycrystalline and hydrangea-type surface appearance for Bi2MoO6, which upon testing in an electrochemical energy storage system displays supercapattery behavior, a combination of a supercapacitor and a battery. From the power law, an applied-potential-dependent charge storage mechanism is established for the Bi2MoO6 electrode material. A Trasatti plot evidences the presence of inner and outer surface charges. The hydrangea-type Bi2MoO6 electrode demonstrates a specific capacitance of 485 F g-1 at 5 A g-1 and a stability of 82% over 5000 cycles. An assembled symmetric supercapattery with a Bi2MoO6//Bi2MoO6 configuration demonstrates energy and power densities of 45.6 W h kg-1 and 989 W kg-1, respectively. A demonstration elucidating the lighting up of three light-emitting diodes, connected in series, by the symmetric supercapattery signifies the practical potentiality of the as-synthesized hydrangea-type Bi2MoO6 electrode in energy storage devices.

Bi2MoO6 Microsphere with Double-Polyaniline Layers toward Ultrastable Lithium Energy Storage by Reinforced Structure

Given its competitive theoretical capacity, Bi₂MoO₆ is deemed as a promising anode material for the realization of efficient Li storage. Considering the severe capacity attenuation caused by the lithiation-induced expansion, it is essential to introduce effective modification. Remarkably, in this work, Bi₂MoO₆ microsphere with double-layered spherical shells are successfully prepared, and the polyaniline are coated on both inner and outer surfaces of double-layered spherical shells, working as buffer layers to strain the volume expansion during electrochemical cycling. Inspiringly, when utilized as anode in LIBs, the specific capacity of Bi₂MoO₆@PANI is maintained at 656.3 mAh g^-1 after 200 cycles at 100 mA g^-1, corresponding to a high capacity of 82%. However, the counterpart of individual Bi₂MoO₆ is only 36%. This result confirms that the polyaniline layer can dramatically promote stable cycling performances. Supported by in situ EIS and ex situ technologies followed by detailed analysis, the enhanced pseudocapacitance-dominated contributions and electron/ion transfer rate, benefiting from the combination with polyaniline, are further proved. This work confirms the significant effect of polyaniline on the ultrastable energy storage, further providing an in-depth sight on the impacts of polyaniline coating to the electrical conductivity as well as the resistances of electron/ion transport.

Ammonium Nitrate-Assisted Synthesis of Nitrogen/Sulfur-Codoped Hierarchically Porous Carbons Derived from Ginkgo Leaf for Supercapacitors

Biomass-derived carbons for supercapacitors provide a promising and sustainable strategy to address the worldwide energy and climate change challenges. Here, we have designed and constructed three-dimensional nitrogen/sulfur-codoped hierarchically porous carbons for high-performance supercapacitor electrode materials in a one-step process, in which ginkgo leaf is used as a carbon source and S source and ammonium nitrate (AN) is used as an activating agent and a N source. During the synchronous carbonization and activation process, AN could be decomposed completely into gaseous byproducts and be removed easily without leaving residues after product formation. The as-synthesized ginkgo leaf-derived carbons exhibited a high specific capacitance of 330.5 F g^-1 at a current density of 0.5 A g^-1 and a capacitance of 252 F g^-1 even at a high current density of 10 A g^-1 with an excellent capacitance retention of 85.8% after 10 000 cycles in 6 mol L^-1 KOH electrolyte. The present study provides an efficient, sustainable, and facile approach to prepare renewable hierarchically porous carbons as advanced electrode materials for energy storage and conversion.

Enhanced electrochemical performance of nanoplate nickel cobaltite (NiCo2O4) supercapacitor applications

Well-ordered, unique interconnected nanostructured binary metal oxides with lightweight, free-standing, and highly flexible nickel foam substrate electrodes have attracted tremendous research attention for high performance supercapacitor applications owing to the combination of the improved electrical conductivity and highly efficient electron and ion transport channels. In this study, a unique interconnected nanoplate-like nickel cobaltite (NiCo2O4) nanostructure was synthesized on highly conductive nickel foam and its use as a binder-free material in energy storage applications was assessed. The nanoplate-like NiCo2O4 nanostructure electrode was prepared by a simple chemical bath deposition method under optimized conditions. The NiCo2O4 electrode delivered an outstanding specific capacitance of 2791 F g-1 at a current density of 5 A g-1 in a KOH electrolyte in a three-electrode system as well as outstanding cycling stability with 99.1% retention after 3000 cycles at a current density of 7 A g-1. The as-synthesized NiCo2O4 electrode had a maximum energy density of 63.8 W h kg-1 and exhibited an outstanding high power density of approximately 654 W h kg-1. This paper reports a simple and cost-effective process for the synthesis of flexible high performance devices that may inspire new ideas for energy storage applications.

Pseudocapacitance electrode and asymmetric supercapacitor based on biomass juglone/activated carbon composites

A novel electrode material incorporating renewable biomass-derived juglone biomolecules with commercial activated carbon (AC) granules has been through simple ultrasonic dispersion and dissolution–recrystallization and was found to exhibit good electrochemical performance. The juglone biomolecules are prepared by an ultrasound-assisted extraction method from abandoned walnut peel, which decreases pollution and increases economic efficiency. Through the dissolution–recrystallization process with AC, a hierarchical structure with nanosized juglone particles was obtained, and the AC particles worked as scaffolding to strengthen the slight biomolecules, thus expanding the active sites and effectively reducing the dissolution of the active materials. The pseudocapacitance fading mechanism was investigated by ex situ FTIR measurement and the porous structure ensures that the composite electrode has an enhanced specific capacitance of 248 F g⁻¹ compared to 172.8 and 62.5 F g⁻¹ for the respective AC and juglone samples. Besides, the excellent cyclic stability (retained 75% after 3000 charge–discharge cycles) was demonstrated. The highest area-specific capacitance of the composites was 1300 mF cm⁻². An asymmetric supercapacitor based on this composite electrode was assembled with an AC electrode as the counter electrode and exhibited good cyclic performance at a voltage of 1.2 V (retained 77% after 3000 charge–discharge cycles), which provides a high energy density of 12 W h kg⁻¹ at a power density of 0.18 kW kg⁻¹ and a high power density of 2 kW kg⁻¹ at an energy density of 9 W h kg⁻¹. This work explores the application of biomolecule-based composites in energy storage devices and provides a potential strategy for constructing environmentally friendly electrodes.

A strategy for transforming abandoned walnut peel to excellent pseudocapacitance material. The activated carbon reshapes and anchors the juglone, which combined the EDLC and pseudocapacitance to achieve high electrochemical performance.

Facile synthesis of a Bi2MoO6/TiO2 nanotube arrays composite by the solvothermal method and its application for high-performance supercapacitor

In this study, bismuth molybdate/titania nanotube arrays (Bi₂MoO₆/TNTs) as a binder-free electrode for supercapacitors were fabricated via a facile solvothermal method. The effects of precursor amounts, solvothermal time and temperature on the microstructure and electrochemical properties of the composite were analyzed. The surface morphology, microstructure, chemical composition and chemical states of the composite electrode material were analyzed using scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Cyclic voltammetry tests, galvanostatic charge–discharge measurements, and electrochemical impedance spectroscopy were employed to analyze the electrochemical behavior of the composite. A specific capacitance of ∼330 mF cm⁻² has been achieved for this Bi₂MoO₆ nanosheets/TNTs composite electrode at the current density of 1 mA cm⁻². Galvanostatic charge–discharge experiments suggest a moderate cycling stability together with 76.7% capacitance retention after 1000 cycles of continuous charge–discharge operation. These results indicate that the Bi₂MoO₆/TNTs composite is a promising electrode material for supercapacitors.

In this study, bismuth molybdate/titania nanotube arrays (Bi₂MoO₆/TNTs) as a binder-free electrode for supercapacitors were fabricated via a facile solvothermal method.

Designed formation of Co3O4/ZnCo2O4/CuO hollow polyhedral nanocages derived from zeolitic imidazolate framework-67 for high-performance supercapacitors

Zeolitic imidazolate frameworks have stimulated great attention due to their potential applications in energy storage, catalysis, gas sensing, drug delivery etc. In this paper, the three-dimensional porous nanomaterial Co3O4/ZnCo2O4/CuO with hollow polyhedral nanocage structures and highly enhanced electrochemical performances was synthesized successfully by a zeolitic imidazolate framework-67 route. The composites hold the shape of the ZIF-67 templates well and the shell has multiple compositions. In the process, we first synthesized the nanostructure hydroxide precursors and then transformed them into the corresponding metal oxide composites by thermal annealing in air. In addition, the mass ratio of Zn to Cu in this material is discussed and optimized. We found that when the mass ratio is 3, the composite material has better electrochemical properties. When applied as an electrode material, Co3O4/ZnCo2O4/CuO-1 shows enhanced pseudocapacitive properties and good cycling stability compared with Co3O4/ZnCo2O4, Co3O4/CuO and Co3O4/ZnCo2O4/CuO-2, and Co3O4/ZnCo2O4/CuO-3. The assembled Co3O4/ZnCo2O4/CuO-1//AC hybrid device can be reversibly cycled in a large potential range of 0-1.6 V and can deliver a high energy density of 35.82 W h kg-1 as well as the maximum power density of 4799.25 W kg-1.

An urchin-like MgCo2O4@PPy core-shell composite grown on Ni foam for a high-performance all-solid-state asymmetric supercapacitor

In recent years, the electrochemical properties of supercapacitors have been greatly improved due to continuous improvement in their composite materials. In this study, an urchin-like MgCo2O4@PPy/NF (MgCo2O4@polypyrrole/Ni foam) core-shell structure composite material was successfully developed as an electrode for supercapacitors. The MCP-2 composite material, obtained by a hydrothermal method and in situ chemical oxidative polymerization, shows a high specific capacitance of 1079.6 F g-1 at a current density of 1 A g-1, which is much higher than that of MC (783.6 F g-1) under the same conditions. Simultaneously, it has low resistance and an excellent cycling stability of 97.4% after 1000 cycles. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) was assembled using MCP-2 as the positive electrode and activated carbon (AC) as the negative electrode. The MCP-2//AC ASC exhibits high specific capacitance (94 F g-1 at a current density of 0.4 A g-1), high energy density (33.4 W h kg-1 at a power density of 320 W kg-1), high volumetric energy density (17.18 mW h cm-3 at a volumetric power density of 0.16 W cm-3) and excellent cycling stability (retaining 91% of the initial value after 10 000 cycles). Simultaneously, the device has low leakage current and excellent self-discharge characteristics. All these results indicate that the MCP-2//AC ASC is a good energy storage device; it can support the function of two LEDs for 20 minutes. These results indicate that the MCP-2//AC ASC will play an important role in energy structures in the future.