| As an important energy storage device,supercapacitors with high power density,long cycle life and superior safety have been paid more and more attention all over the world.In this paper,high yield ultra-thin porous nickel-based materials and uniformly distributed cobalt-based nanorods with low crystallinity can be obtained by novel electrochemical methods.I will introduce these two kinds of applications in detail.Two-dimensional materials have large specific surface area and many active sites.Among them,higher theoretical capacity(289 mAh g-1)and lower cost β-Ni(OH)2 in hydroxide with typical layered structure of brucite have attracted more and more attention.At present,there are many ways to synthesize(3-Ni(OH)2 nanomaterials.Among these attempts,chemical coprecipitation is the simplest approach with low cost,but it often leads to agglomeration and is difficult to control the morphology of product.Hydrothermal method is more attractive for the synthesis of Ni-based nanomaterials with various morphologies.However,hydrothermal synthesis constantly involves high temperature,high pressure and long reaction period which not only is disadvantageous to mass production,but sometimes also cause safety concerns.Relatively,the metal hydroxides can be deposited on conductive substrate by cathodic deposition,however,high loads constantly result in stacked and compact Ni(OH)2 layers,which own limited active sites for electrochemical application.Based on the above considerations,it will be introduced in this paper that only nickel foam has been used in 1 M NaCl aqueous solution by three electrode electrochemical oxidation at near room temperature.A large number of crystalline β-Ni(OH)2 nanosheets with the thickness of 4 nm and 2～3nm nano-pore can be easily obtained.The novel synthesis method can effectively avoid the high temperature and high pressure process of traditional synthesis.In general,mass production ultrathin β-Ni(OH)2 nanosheets can be obtained by this safe and simple method.,which greatly reduces the cost and difficulty of the synthesis process and provides a great possibility for industrial production in the future.Where the reaction of supercapacitor mainly occurs is the interface between the material and electrolyte.It is difficult to use the active material inside of the nanomaterials,becaused the redox reaction is carried out on the surface or near the surface of the electrode.How to make full use of all the active substances is an urgent problem.A simple method for preparing low crystallinity CoO/CoOOH nanoarrays with uniform morphology and distribution was studied in this paper.First,CoO nanowires were prepared.Due to the complete redox reaction,the crystallinity of well crystallized CoO becames lower and mixture of CoO、CoOOH nanorods were formed after further electrochemical activation.Because of the high content of CoOOH on the surface of nanorods,the hydrophilicity of the material increases.It is favorable for the infiltration of electrolyte in the nanorods by the high content of amorphous CoO inside of the nanorods,which could increase the reactive sites of the nanomaterials.This non-uniform distribution of the special core-shell structure enables the active material to fully contact the electrolyte inside.It is helpful to increase the capacity of active materials by allowing the internal materials of nanorods to fully react with redox reaction.the maximum capacity of 200 mAh g-1 can be obtained,when the current density is 1A g-1.The volume value is still 169 mAh g-1,84.5%of the initial capacity,when the current density is 20 A g-1.Compared with commercial activated carbon,A hybrid cell can be obtained.The energy density could reach 38.75 Wh kg-1 with the power density of 726 W kg-1.And with the current density of 12 A g-1,the capacity of the hybrid device can still keep 83.3%of the initial value after 5000 cycles,which indicates the good stability of the electrode.In general,this novel preparation method provides a new way to improve the energy storage energy of active materials. |
PDF Full Text Request