The development of pseudocapacitive materials for energy-oriented applications has stimulated considerable interest in recent years due to their high energy-storing capacity with high power outputs. Nevertheless, the utilization of nanosized active materials in batteries leads to fast redox kinetics due to the improved surface area and short diffusion pathways, which shifts their electrochemical signatures from battery-like to the pseudocapacitive-like behavior. As a result, it becomes challenging to distinguish "pseudocapacitive" and "battery" materials. Such misconceptions have further impacted on the final device configurations. This Review is an earnest effort to clarify the confusion between the battery and pseudocapacitive materials by providing their true meanings and correct performance metrics. A method to distinguish battery-type and pseudocapacitive materials using the electrochemical signatures and quantitative kinetics analysis is outlined. Taking solid-state supercapacitors (SSCs, only polymer gel electrolytes) as an example, the distinction between asymmetric and hybrid supercapacitors is discussed. The state-of-the-art progress in the engineering of active materials is summarized, which will guide for the development of real-pseudocapacitive energy storage systems.

True Meaning of Pseudocapacitors and Their Performance Metrics: Asymmetric versus Hybrid Supercapacitors

As modern society develops, the need for clean energy becomes increasingly important on a global scale. Because of this, the exploration of novel materials for energy storage and utilization is urgently needed to achieve low-carbon economy and sustainable development. Among these novel materials, metal–organic frameworks (MOFs), a class of porous materials, have gained increasing attention for utilization in energy storage and conversion systems because of ultra-high surface areas, controllable structures, large pore volumes and tunable porosities. In addition to pristine MOFs, MOF derivatives such as porous carbons and nanostructured metal oxides can also exhibit promising performances in energy storage and conversion applications. In this review, the latest progress and breakthrough in the application of MOF and MOF-derived materials for energy storage and conversion devices are summarized, including Li-based batteries (Li-ion, Li–S and Li–O2 batteries), Na-ion batteries, supercapacitors, solar cells and fuel cells.

Metal–Organic Frameworks (MOFs) and MOF-Derived Materials for Energy Storage and Conversion

Creating oxygen-vacancies in MoO3-x nanobelts toward high volumetric energy-density asymmetric supercapacitors with long lifespan

Supercapacitors (SCs) have attracted much attention as energy storage devices due to their high power density, fast charge/discharge capability, and long cycling life. The core/shell structure design of the electrocapacitive material is one of the effective ways to achieve large surface area and high conductivity for providing more faradaic reaction sites and accelerating the charge transfer, respectively, and therefore to enhance the electrocapacitive performance of SCs. To better understand the core/shell structure, this review paper compares the material category, morphology, and synthesis methods for the core/shell structures as well as their electrochemical performances for the corresponding SCs. The electroactive materials applied in the core/shell structure include carbon materials, conducting polymers, metals, metal hydroxides, metal oxides and metal sulfides, while zero-dimensional, one-dimensional, two-dimensional, and three-dimensional structures are considered for the core/shell material. This review article outlines the most commonly used methods for making the core and shell materials over the past decade (2007–2018), and points out the most efficient combination of the material categories and morphologies for the core/shell structure. By understanding the details of the core/shell materials, more efficient design regarding the choices of material category and morphology can be achieved, and therefore better electrocapacitive performance for the resulting SCs can be realized.

A review of electrode materials based on core–shell nanostructures for electrochemical supercapacitors

Construction of magnetic lignin-based adsorbent and its adsorption properties for dyes.

The invention belongs to the technical field of synthesis of composite materials, relates to preparation of CoFe-LDH composite materials, and specifically relates to a preparation method of CoFe-LDH/polypyrrole/graphite oxide ternary composite materials. The preparation method of CoFe-LDH/polypyrrole/graphite oxide ternary composite materials includes the steps: preparing a nitrate mixed solutionby dissolving 25-100 mg of Ppy/GO, 2-3 mmol of cobalt nitrate hexahydrate, and 1 mmol of ferric nitrate nonahydrate in 50 mL of deionized water; and preparing a mixed alkali solution with the concentration of 0.35 mol/L of NaOH and 0.15mol/L of NaCO3 per 250 mL, slowly dropping the mixed alkali solution to the nitrate solution, adjusting the pH to 10.0 pm 0.1, stirring for 20-30 min, and reactingin a 65 DEG C water bath for 20-24 h, and then obtaining the CoFe-LDH/polypyrrole/graphite oxide ternary composite material after washing and drying. In the preparation method of CoFe-LDH/polypyrrole/graphite oxide ternary composite materials, the pyrroles are loaded on the graphite oxide by in-situ polymerization, and the CoFe-LDH prepared by electrostatic adsorption coprecipitation is adsorbed on the Ppy/GO, thus obtaining a binderless ternary composite material which can be used as an SC electrode, and the prepared material has a regular ultra-thin hexagonal layered sheet structure. The preparation method of CoFe-LDH/polypyrrole/graphite oxide ternary composite materials has the advantages of being simple in the process and being low in the price of the raw materials, and the obtained material is suitable as an electrode material of a super capacitor, and the preparation method of CoFe-LDH/polypyrrole/graphite oxide ternary composite materials is easy for industrial production.

Preparation method of CoFe-LDH/polypyrrole/graphite oxide ternary composite materials

The invention provides a preparation method for a bismuth molybdate/polyaniline composite supercapacitor electrode material. The preparation method comprises the following steps of dissolving bismuth nitrate and sodium molybdate into ethylene glycol at a molar ratio at a room temperature to obtain a mixed solution A, and performing ultrasonic uniformity and adding a mixed solution of urea and absolute ethyl alcohol; stirring continuously and uniformly and then pouring the mixed solution into a polytetrafluoroethylene stainless steel hydrothermal reaction kettle, sealing and performing a solvothermal reaction; after naturally cooling, performing washing and drying to obtain bismuth molybdate; performing ultrasonic dispersion of bismuth molybdate and lignin sodium sulfonate into deionized water to obtain a mixed solution, then adding an aniline monomer and p-toluenesulfonic acid, and then changing into ice- bath stirring, after the aniline is dispersed, obtaining a mixed solution B; and slowly dropwise adding an ammonium persulfate solution to the mixed solution B, and after the ice-bath reaction is completed, performing washing and drying to obtain the bismuth molybdate/polyaniline composite material. The method is simple, and the capacitance performance of the prepared bismuth molybdate/polyaniline composite material is greatly improved.

Preparation method for bismuth molybdate/polyaniline composite supercapacitor electrode material

The invention belongs to the technical field of nano-material preparation, and relates to synthesis of a composite photocatalyst, especially to a method for preparing a cobaltosic oxide composite photocatalyst through a liquid phase precipitation method and an application of the composite photocatalyst. The method comprises: taking metal bismuth salt as an additive, taking cobalt salt and sodium bicarbonate which is a precipitating agent as raw materials, performing liquid phase precipitation, and through adjustment of additive content and other variables, performing high-temperature drying toobtain the composite photocatalyst. The liquid phase precipitation method is low in cost and simple to operate. The prepared particle products are uniformly dispersed, are high in performance, and maintain the dispersion system to be relatively stable. The size and shape of nano-particles can be regulated, and the particle dispersity and shaper are good. The prepared nanomteter bismuth compositecobaltosic oxide can be used as a photocatalyst used for wastewater treatment. The photocatalyst has an obvious effect on photocatalytic degradation of dye, and is suitable for industrial production.

Method for preparing cobaltosic oxide composite photocatalyst through liquid phase precipitation method and application of composite photocatalyst

The invention belongs to the technical field of nanometer material preparation, and relates to a preparation of copper cobalt oxide composite electrode material by a solvothermal method and application thereof The method comprises the steps of: using urea as precipitant, and copper salt, cobalt salt, sodium lignosulfonate as raw material, wherein the above copper salt, cobalt salt, sodium lignosulfonate and deionized water or absolute ethanol have a volume ratio of 1-4 mmol: 2-9 mmol: 2-12 mmol: 0-04 g: 50-85 mL; performing thermoprecipitation via a solvent; adjusting the content of a precipitator and the copper salt, cobalt salt, sodium lignosulfonate and other variable; performing calcinating, drying and calcinating to obtiain the copper cobalt oxide composite electrode material The method of the invention has the advantages of low cost, simple operation, uniform particle distribution of the prepared product, high particle performance, relatively stable dispersion system, good particle size dispersion and good morphology The prepared copper cobalt oxide nanocomposite electrode material is fixed on the nickel foam substrate by binder and applied to the supercapacitor, which has excellent electrochemical performance and is suitable for industrial production

Preparation of copper cobalt oxide composite electrode material by solvothermal method and application thereof

The invention belongs to the technical field of composite electrode material preparation, relates to synthesis of nano composite electrode materials and particularly relates to a method for preparinga nickel-based magnesium cobaltate composite electrode material by using a solvent heat-in-situ oxidation polymerization method and the application thereof. The method comprises the following steps: by taking urea as a precipitant, and a magnesium salt, a cobalt salt, pyrrole p-toluenesulfonic acid and ammonium persulphate as raw materials, carrying out hydrothermal precipitation, adjusting contents and other variables of the precipitant, the magnesium salt and the cobalt salt, and calcining so as to obtain sea urchin-shaped magnesium cobaltate; further carrying out in-situ oxidation polymerization, and carrying out high-temperature drying, so as to obtain a sea urchin-shaped magnesium cobaltate composite electrode material. Polypyrrole is adopted as a conductive macromolecule, so that theconductivity of the material can be improved, and internal resistance can be reduced. With the combination of a hydrothermal method and an in-situ oxidation polymerization method, the method is low in cost, simple to operate, uniform in product granule distribution, good in granule property, relatively stable in dispersion system, good in particle size dispersion, relatively good in morphology, applicable to electrode materials of supercapacitors, excellent in electrochemical property and applicable to industrial production.

Method for preparing nickel-based magnesium cobaltate composite electrode material by using solvent heat-in-situ oxidation polymerization method and application

Zhou Saisai

Papers

Preparation method of CoFe-LDH/polypyrrole/graphite oxide ternary composite materials

Preparation method for bismuth molybdate/polyaniline composite supercapacitor electrode material

Method for preparing cobaltosic oxide composite photocatalyst through liquid phase precipitation method and application of composite photocatalyst

Preparation of copper cobalt oxide composite electrode material by solvothermal method and application thereof

Method for preparing nickel-based magnesium cobaltate composite electrode material by using solvent heat-in-situ oxidation polymerization method and application