Synthesis Of Transition Metal Hydroxides And Oxides And Their Electrochemical Properties Study

Supercapacitor has some advantages over secondary battery such as higher power density, faster charge and discharge rate, higher efficiency and longer cycle life. It is a kind of practical, efficient, environmental friendly energy storage device. As the electrode material of supercapacitor, hydroxides have high specific capacity and many other advantages, which have been received more and more attention.In this paper, aluminum doped cobalt hydroxide and cobalt-nickel double hydroxide as well as cobalt-nickel double hydroxide/carbon composite as supercapacitor electrode materials were synthesized by liquid phase precipitation and solid state reaction,respectively. The physical and electrochemical characterization such as XRD, SEM and cyclic voltammograms, constant current charge and discharge, cycle life test, and electrochemical impedance were used to study the performance of the electrode materials.The main contents are as follows:Different doping ratio of aluminum doped cobalt hydroxide were synthesized using liquid phase precipitation method. XRD test shows that the synthesized Al doped cobalt hydroxide were α-Co(OH)2, The morphology of the Co0.83Al0.17(OH)2.13 sample is patch from SEM images. Cyclic voltammograms test showed the synthesized aluminum doped cobalt hydroxide have excellent Faraday pseudocapacitive performance. Constant current charge-discharge test shows the discharge capacity of Co0.83Al0.17(OH)2.13 is the highest(607.3F/g at 0.5A/g) among the synthesized Al doped cobalt hydroxide. After 1000 cycles, its capacity still have 512 F/g, the capacity retention ration is 84.3%. Electrode kinetics research showed the discharge process was controlled by diffusion. The electrochemical impedance test showed Co0.83Al0.17(OH)2.13 electrode has the minimum charge transfer resistance.Different doping ratio of aluminum doped cobalt hydroxide were also synthesized using solid state reaction method. XRD test shows that the synthesized sample without doping Al was β-Co(OH)2, the Al doped samples were α-Co(OH)2. The morphology of the Co0.83Al0.17(OH)2.13 sample is granular particles from SEM images, and particle sizewere between 100~200 nm. Cyclic voltammograms test showed the synthesized aluminum doped cobalt hydroxide have excellent Faraday pseudocapacitive performance.Constant current charge-discharge test shows the discharge capacity of Co0.83Al0.17(OH)2.13 is the highest(417.5F/g at 1A/g) among the synthesized Al doped cobalt hydroxide. After 1000 cycles, its capacity still have 410 F/g, the capacity retention ration is 98.2%. Electrode kinetics research showed the discharge process was controlled by diffusion. The electrochemical impedance test showed Co0.83Al0.17(OH)2.13 electrode has the minimum charge transfer resistance.Different cobalt-nickel ratio of cobalt-nickel double hydroxide and cobalt-nickel double hydroxide/carbon composite were synthesized using solid state reaction method.XRD test shows that the synthesized cobalt-nickel double hydroxide were β phase hydroxide, The morphology of the Co0.6Ni0.4(OH)2 sample is mainly granular, the particle size were between 1~3 micrometers, and there is an obvious conglomeration from SEM images.After adding suitable amount of carbon, the synthesized sample was tiny particles,and the particle size were between 100-300 nm, which showed only a small amount of conglomeration. constant current charge-discharge test showed that the discharge capacity of Co0.6Ni0.4(OH)2 is the highest(956.3F/g at 0.5A/g) among the synthesized cobalt-nickel double hydroxides, after 1000 cycles, its capacity decrease to 306.3 F/g, the capacity retention ration is 32.7%. After adding suitable amount of carbon black, the discharge capacity of CNC1 was 1010 F/g at 0.5A/g, after 1000 cycles, its capacity still have 360 F/g, the capacity retention ration is 35.5%.,which shows that the addition of carbon black can increase cobalt nickel double hydroxide specific capacity, and improve the cycle stability. Electrode kinetics research showed the discharge process of Co0.6Ni0.4(OH)2 and CNC1 electrodes were controlled by diffusion. The electrochemical impedance test showed CNC1 electrode has the minimum charge transfer resistance.