Preparation Of Prussian Blue Derivatives Electrode Materials And Energy Storage Performance Research In Supercapacitors

In recent years,some new demands have been created by the social needs and the declining reserves of non-renewable resources for energy storage and conversion devices.Supercapacitors are small and light,environmentally friendly,high power density and long service life as a novel type device of energy storage.Prussian blue and its analogues play an important role as new metal-organic framework for electrode materials.Based on the current research status of Prussian blue analogues and derivatives（PBA）,a series of derivative materials have been synthesized using Prussian blue analogues as precursors in the direction of derivatives.The corresponding positive/negative materials were also synthesized.The asymmetric supercapacitors were assembled and its electrochemical performance was analyzed.The main research of this paper is as follows.（1）The negative electrode material Fe₂O₃ nanoparticles were obtained by a combination of chemical precipitation and annealing methods using ferric ferricyanide as precursor.The specific capacitance of Fe₂O₃ was 193 F g^-1 at a current density of 1 A g^-1 and good cycling stability(70%remaining after 2000 cycles at 5 A g^-1),showing a relatively long cycle life.The asymmetric supercapacitor was assembled using the NiCo-LDH/rGO material as positive material and Fe₂O₃ as negative material.And the NiCo-LDH/rGO//Fe₂O₃ asymmetric supercapacitor（ASC）achieves an energy density of 14.6 Wh kg^-1 at 801.2 W kg^-1.And the cycle life of 78.3%was still achieved after 10,000 long-term cycles,which proves the advantage of Fe₂O₃as positive material for supercapacitors.（2）In this work,a simple strategy combining chemical precipitation and hydrothermal methods was developed to prepare a sea urchin-like Co Ni₂S₄ compound with remarkable specific capacity(149.1 m A h g^-1 at 1 A g^-1)and good cycling stability（83.1%remaining after 3000 cycles）using nickel hexamyanocobaltate as a precursor.In addition,the 94.7%initial capacity of porous carbon nanospheres（PCNs）was remained after 10,000 cycles at 10 A g^-1.A novel Co Ni₂S₄//PCNs ASC was constructed using Co Ni₂S₄ as the positive and PCNs as the negative.The ASC exhibited an impressive energy density of 41.6 Wh kg^-1 at 797 W kg^-1.The superior performance of ASCs indicates that the prepared Co Ni₂S₄ and PCNs materials are potential energy storage materials.（3）A rectangular nanorod nanostructure derived from bismuth hexacyanoferrate with large specific surface area and porosity was designed.The internal porous rectangular nanorods can reduce the volume shrinkage during the charging and discharging process.Bi₂O₃/BiFeO₃ material achieves a specific capacitance of 741 F g^-1 and a long-term cycle life by chemical precipitation and annealing.NiCo-LDH/rGO(954 F g^-1)was synthesized by one-step hydrothermal and exhibited a cycling stability of 86%after 10,000 cycles.It was used as a positive to build asymmetric supercapacitors.Surprisingly,the NiCo-LDH/rGO//Bi₂O₃/BiFeO₃ ASC achieves a huge energy density of 59.7 Wh kg^-1 at 800 W kg^-1.The initial value of79.3%was still retained after 7000 cycles of charging and discharging at a current density of 3 A g^-1.This work shows that Bi₂O₃/BiFeO₃ has great potential in the direction of energy storage materials.