Preparation And Capacitance Performance Of Nickel/cobalt Phosphate Materials

The consumption of fossil fuels and increasing environmental pollution have accelerated the development of new energy sources as sustainable energy sources.At present,supercapacitor have aroused the attention of numerous researchers,which owes to their quick charging and discharging rate,long cycle life,environmental friendly and wide range of applications served as electrochemical energy storage device.The core part of the supercapacitor is the electrode material,so the research should focus on the preparation and properties of the electrode material for supercapacitor.In recent years,the transition metal phosphates have become a research hotspot and many previous studies have reported the potential applications of transition metal phosphates in the fields of catalysis and lithium ion battery but few for supercapacitors.In addition,the synthesis methods of transition metal phosphate are mostly hydrothermal method and coprecipitation method,but they also exist disadvantages,for instance,the hydrothermal method owns long reaction time and the products prepared by coprecipitation method have low purity.Therefore,we will synthesize a series of products of metal phosphates to study the performance of the electrode materials for supercapacitors using efficient and adjustable microwave-assisted method.The main contents of our work are as follows:?1?The products of Ni₃?PO₄?₂·8H₂O with different morphology was prepared via a microwave-assisted method.The Ni?NO₃?₂·6H₂O and NH₄H₂PO₄ acted as nickel source and phosphorus source,respectively,and the NaHCO₃ served as precipitant.The growth mechanism was discussed preliminarily.In order to determine the best reaction time,SEM characterization and electrochemical performance test were carried out.What's more,an assembled hybrid asymmetric supercapattery device fabricated from the optimizing products of N-90 with better electrochemical properties as the cathode material and rGO as anode material.The hybrid device is used to assess its feasibility in practical application.The present work will direct a perfect generation of metal phosphate oxide material for supercapattery and the facile route will give rise to the metal phosphate oxides as an attractive active material for promising application in electrochemical energy storage.?2?There is a general problem of poor circulation stability using metal phosphate as supercapacitor electrode materials.In this chapter,microflower-like cobalt phosphate via microwave-assisted method followed by annealing was synthesized.When tested as supercapacitor electrode,the product delivers a super cyclic stability.?3?Aiming at the shortcomings in the above chapter,the product Ni-Co phosphate was obtained by adjusting the raw ratio of nickel and cobalt with microwave-assisted method followed by subsequent calcination using Ni?NO₃?₂·6H₂O and Co?CH₃COO?₂·4H₂O as nickel source and cobalt source,respectively.NH₄H₂PO₄acted as phosphorus source and the NaHCO₃ served as precipitant.The characterization analysis concludes that the capacitance value of the electrode material by introducing Ni elements was greatly improved compared with that of pure cobalt-based phosphate,which delivered a high specific capacitance reached up to1214 F g^-1 at 1 A g^-1 and an improved potential window,as well as an outstanding cycling stability.