When amorphous \"love\" the graphene supercapacitor begins to be magical
North star energy storage net news: editor's note: the development and utilization of renewable energy is more and more aroused people's attention, energy storage technology at this stage to promote energy system is critical to economic, super capacitor is being as a substitute for energy/power production.
The super capacitor
Super capacitor is a cross between traditional capacitor and no maintenance between the secondary battery of new type energy storage device, its specific energy, specific capacitance is 1000 times more than conventional capacitors, power is 10 times more than secondary battery, with a wide working temperature range, can fast charge and discharge, long cycle life and pollution-free advantages of zero emissions. Super capacitor, therefore, as a kind of high power energy storage device, the electric vehicles, hybrid vehicles, special truck, electric power, railway, communications, defense, and consumer electronics products, and many other fields has great application value and market potential. Supercapacitors can be divided into two electrical and Faraday capacitors according to their charge storage principle. Double layer capacitors are based on the two-layer theory, which USES the interface between electrodes and electrolytes to store energy. Faraday capacitor based on Faraday process, near the electrode surface or body in a certain range, to the electrical activity of phase change material, reversible and rapid owe potential deposition, chemical absorption, stripping or REDOX reaction, resulting in a related to charging voltage of capacitor for energy storage.
There are major problems
For a long time, the super capacitor electrode materials research focuses on the nanocrystalline material, but nanocrystalline materials difficult to expansion or contraction, and the properties of ion diffusion characteristics of the various members of the opposite sex limit cycle life and fast charging and discharging performance of the supercapacitor. At the same time, the synthesis of nanocrystalline materials are usually carried out under high temperature, has greatly increased the production cost, and the process is complex, it's hard to do mass production, greatly limits the super capacitor is widely available, only a small amount of commercial application of super capacitor products.
What happens with nanocrystals
In recent years, amorphous materials have been proposed as electrode materials for supercapacitors, and have attracted the interest of researchers. Compared to the synthetic temperature of the crystalline material, the amorphous materials are lower, thus reducing the synthetic cost of electrode material. Amorphous materials, free lattice, belong to the fixed type, so the structure is more stable, volume control, which helps transport of ions, therefore as energy storage material, amorphous materials has a broad prospect. However, the deficient conductivity of non-crystalline materials and the smaller surface area limit the performance of supercapacitors to a certain extent. So, the development of mass production, low cost, high cycle life and fast charging and discharging of new amorphous materials is a core matter of science, in the field of new energy storage at the same time is also a difficult problem in the world super capacitor industrialized production.
Why would you think of nanomaterials
Nanocrystalline material block crystallization compared on a variety of performance has improved substantially, by analogy, nano amorphous materials compared with bulk amorphous materials must has more excellent performance. To nano amorphous materials, can effectively improve the specific surface area, material for super capacitor electrode materials, using nano amorphous materials will greatly improve energy storage active sites on the surface of the electrode and shorten ion transport path, the electrode electrochemical energy storage performance will be improved to a great extent.
Nanoparticles have a look at graphene
Nanjing university of technology professor Xia Hui team developed a suitable for mass production such as synthesis methods of success at room temperature was prepared nano amorphous FeOOH quantum dots (average particle size of 2 nm) and the load on the graphene FeOOH/graphene composite nanometer film. The three dimensional conductive network built through graphene and FeOOH nano amorphous quantum dots with large active surface, make the composite electrode materials exhibit excellent properties of super capacitor. The potential window of a single electrode in -0.8 -0v (vsAg/AgCl) can reach 365F/g's high over capacitance, and it will retain the capacity of 189F/g at 128A/g's large current density. It is better than the crystalline electrode material. This work proposes nano amorphous iron oxides/hydroxyl material is a kind of new type has a good prospect of super capacitor electrode materials, and designed for high performance of super capacitor electrode materials to provide a new way of thinking.
What needs to be improved further
Although the resulting amorphous FeOOH/graphene composite nano piece within the range of 0-0.8 - v voltage showed good capacitive performance, the composite electrode materials within the range of 0-1.3 - v voltage can be obtained up to 1243 f/g of specific capacitance values, but partly dissolved electrode materials, affected the stability of the electrode, needs further research work to improve.
The development prospect
Synthetic amorphous FeOOH/graphene composite nanochip, the synthetic method of invention is green and simple. Under the atmospheric pressure, the material is iron and carbon, etc., in the nature reserves are abundant, and it is easy to extract, greatly reduces the cost; At the same time, the synthesis process of no poisonous and harmful gas generated, more important is the quantity of materials synthesis depends on the size of the container, make its industrialized production. The composite electrode material shows excellent super capacitance, high cycle life and rapid charge and discharge. Xia Hui professor said: "compared to other synthetic process of nanocrystalline material, amorphous nanometer material synthesis method is simple, simple process, easy to control, can meet the requirements of industrial production technology, the new material into the industrialization production has a bright future."
The journal of the findings in related disciplines of AdvancedFunctionalMaterials 26 (2016) 919, the work is a professor at Xia Hui group in the early stage of the ferric oxide/graphene composite nanometer materials used in the study of asymmetric supercapacitor, developed on the basis of previous study, published in the AdvancedFunctionalMaterials 25 (2015) 2015-635.