The Preparation Of Cobalt Nickel Hexacyanoferrate And The Study Of It's Capacitance Performance

Supercapacitors,as a new type of energy storage devices between battery and traditional capacitor,is recently developed.Currently,research about prussian-blue as the electrode materials is increasing because of the unique properties of prussian-blue,such as the high capacity,low price,and less environmental pollution.Cobalt nickel hexacyanoferrate(Ni_xCo_1-xHCF,0<x<1)as a prussian-blue derivatives,with a 3D mesh structure,which is similar to molecular sieve of cubic structure.This paper mainly studies on the electrochemical properties of Ni_xCo_1-xHCF?0<x<1?and the composites of Ni_xCo_1-xHCF?0<x<1?and carbon nano-tubes.To investigate the electrochemical properties of prepared devices,cyclic voltammetry,galvanostatic charge-discharge,electrochemical impedance spectroscopy and cycle life are uesd.This paper adopts hydrothermal synthesis method to prepare Ni_x Co_1-x HCF?x=1,2/3,1/2,1/3,0?,at the same time to compare the electrochemical performance of different Ni_xCo_1-xHCF?x=1,2/3,1/2,1/3,0?materials in condition of the KNO₃ electrolyte's concentration is 1 mol/L.The result shows that:when x=2/3,the production of K_1.15Ni_0.55Co_0.37Fe?CN?₆ has the best electrochemical performance.When the current density is 1 A/g,the discharge capacity of K_1.15Ni_0.55Co_0.37Fe?CN?₆ reaches 493.3 F/g,which is higher than the discharge capacity of Ni_xCo_1-xHCF?x=1,1/2,1/3,0?;when the current density increased from 0.2 A/g to 5 A/g,its specific capacity reduced from 535.3 F/g to391.6 F/g,and the capacity retention rate is 73.2%,which is the highest rate;when the current density is 1 A/g,after 2000 cycles,its specific capacity is still the highest.Therefore,K_1.15Ni_0.55Co_0.37Fe?CN?₆ electrode has the best electrochemical performance.Research about the impact of different potassium electrolyte to the electrochemical performance of K_1.15Ni_0.55Co_0.37Fe?CN?₆ electrode.The conclusion shows that:the electrode with the best electrochemical performance when it immerse in the KCl electrolyte,also its polarization and charge transfer resistance is the smallest.After that,study on the influence of the concentration of KCl for the working electrode's electrochemical performance.The results reveal that the highest specific capacitance value is 540 F/g when the KCl electrolyte's concentration is 4 mol/L?near saturation?and the current density is 1 A/g;the maximum capacitance retention is 86.9%when the current density increased from 0.2 A/g to5 A/g and the specific capacitance value reduced from 556.3 F/g to 483.3 F/g.So it is concludedthatwecanachievethebestelectrochemicalperformanceof K_1.15Ni_0.55Co_0.37Fe?CN?₆ electrode when the KCl electrolyte's concentration is 4 mol/L.Researchontheelectrochemicalperformanceofthecompositeof K_1.15Ni_0.55Co_0.37Fe?CN?₆andcarbonnano-tube.Thedischargecapacityof K_1.15Ni_0.55Co_0.37Fe?CN?₆/CNT can reach 580 F/g,which is still higher than the discharge capacity of K_1.15Ni_0.55Co_0.37Fe?CN?₆ in the condition that the concention of KCl electrolyte is 4 mol/L and the current density is 1 A/g;after 2000 cycles,K_1.15Ni_0.55Co_0.37Fe?CN?₆/CNT electrode's specific capacitance reaches 520 F/g,which is still higher than the discharge capacity of K_1.15Ni_0.55Co_0.37Fe?CN?₆ electrode.Therefore,the electrochemical performance of K_1.15Ni_0.55Co_0.37Fe?CN?₆/CNT electrode's is better than that of K_1.15Ni_0.55Co_0.37Fe?CN?₆ electrode.