Preparation And Application Of Copper-cobalt-nickel Prussian Blue Composites In Sodium And Potassium Ion Flexible Supercapacitors

Supercapacitors play an important role due to their wide applications.Flexible supercapacitor devices are of special interest due to their potential application in wearable technologies.Prussian blue(PB)is a non-toxic and cost-effective material with special structure.Its struction can be modified through transition metal doping or acid etching.Conductive materials are usually applied to obtain PB hybrid struction for superiorelectrochemical performance,such as carbon materials,conductive polymer(such as polypyrrole,polyaniline)and metal oxide etc.As for substrate materials,carbon material,polymer membrane and metal sheet are generally used..In this paper,PB based supercapacitor devices with various conductive hybrid mateirals and flexible substrates are studied,specific as follows:(1)Removal of crystal water from nickel-cobalt Prussian blue analogs by polyaniline coating and its application in flexible sodium ion supercapacitorsNickel-Cobalt prussian blue analogs(NiCoPBA)and aniline in situ deposition and polymerization on the carbon sponge(CS)by coprecipitation method.The polyaniline coating nickel and cobalt Prussian blue flexible material(NiCoPBA@PANI@CS)is prepared.The addition of polyaniline removed the interstitial water of NiCoPBA structure,greatly improve the electrochemical performance.This article verifies the NiCoPBA@PANI@CS whether successfully removal of interstitial water,and the influence of different contant of PANI for materials.The research results show that the addition of polyaniline is benefit to remove intertial water.The electrochemical performance of 100 mg PANI electrode material is superior to 200 mg PANI material.The two materials are named as NiCoPBA@PANI-1@CS and NiCoPBA@PANI-2@CS,respectively.At the current density of 1 A g^-1,the specific capacitance of AC//NiCoPBA@PANI-1@CS is 700 F g^-1.The capacity retention rate of the asymmetric supercapacitor AC//NiCoPBA@PANI-1@CS is 86%after 2000 cyclesat 9A g^-1.The energy density of AC//NiCoPBA@PANI-1@CS is 17.5 Wh kg^-1while the power density is 6.23 k W kg^-1.When the energy density is 32 Wh kg^-1,the power density is0.576 kg^-1.The CV curve and GCD curve of the asymmetric supercapacitor change slightly under different bending angles,which indicates that the material has good flexibility and toughness.(2)Preparation of NiCoPBA@rGO electrode material and its application in sodium ion flexible supercapacitorNiCoPBA@rGO material is prepared by hydrothermal method with ascorbic acid as reducing agent,followed by freeze-dring.The flexible asymmetric supercapacitor is prepared with carbon cloth as flexible substrate.The structural morphology and electrochemical performance of the material in sodium solution are studied.We can see from these characterizations that GO is successfully reduced to rGO,and the electrical conductivity is enhanced due to the addition of rGO.Electrochemical performance of NiCoPBA is also improved.The specific capacitance of the material(NiCoPBA@rGO@Carbon Cloth)at the current density of 1A g^-1 is 150 F g^-1 in the three-electrode system,and the specific capacitance of the material at the two-electrode system is 85 F g^-1 at 1 A g^-1.The energy density of AC//NiCoPBA@rGO@CC is11.8Wh kg^-1(the power density is 0.445 k W kg^-1).When the energy density is 5.56Wh kg^-1,the power density is 10 k W kg^-1.The power density of AC//NiCoPBA@rGO@CC are 0.445 k W kg^-1and 10 k W kg^-1 while the energy density are 11.8Wh kg^-1and 5.56Wh kg^-1 respectively.The capacity retention rate of this asymmetric supercapacitor is 84.36%after 4000 cycles.(3)Preparation of copper-cobalt prussian blue potassium ion supercapacitors by carbon nanotubes coatingThe treated carbon nanotubes are mixed with cobalt nitrate and copper nitrate solution,and the two metal cations are adsorbed on the carbon nanotubes through electrostatic reaction.Then,the ternary Cu_0.66Co_0.33PBA@CNTs materials were prepared by aniline polymerization reaction.The electrochemical properties of the electrode materials with different contents of carbon nanotubes were studied with nickel foam as flexible substrate and potassium ion solution as electrolyte.The results show that the electrochemical performance of the material is best when CNTs content is20wt%.Excessive CNTs will cause aggolomeration and affect ion transport.The specific capacitance of 20 wt%CNT Cu_0.66Co_0.33PBA@CNTs(Cu_0.66Co_0.33PBA@CNTs-20)material at 1 A g^-1 is 226.9 F g^-1.The energy density of AC//Cu_0.66Co_0.33PBA@CNTs-20 is 5.56 Wh kg^-1 at the power density of 0.5 k W kg^-1.