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Study on Metal Oxide and Its Composite Materials for Supercapacitor Electrode

Author: LangJunWei
Tutor: KangLong；KongLingBin
School: Lanzhou University of Technology
Course: Materials Science
Keywords: Supercapacitor Electrode material Specific capacitance Cobalt oxide Nickel oxide USY
CLC: TM53
Type: PhD thesis
Year: 2010
Downloads: 460
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Abstract

Supercapacitor is a new type of energy storage device, because of its high specific power, cycle performance, to become one of the hot spots in the study of new chemical power. This paper reviewed the latest research progress of supercapacitor electrode materials and preparation of the electrode material. XRD, SEM, TEM and BET analysis of the microstructure and morphology of the electrode material, constant current charge and discharge, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) technology test its electrochemical properties. The main content is as follows: 1. Using different chemical precipitation method to prepare several different cobalt hydroxide, nickel hydroxide and nickel oxide material. To characterize the structure and performance of the resulting oxide materials, and preliminary investigation of the relationship between the structure and performance of the electrode materials. The results show that having a layered structure and has a very wide layer spacing of the metal oxide has a significantly excellent electrochemical properties; effective mesoporous pore distribution and the effective specific surface area of ??the material produces a high specific capacity of the important reasons, and in the electrode material than influence on the capacitor, the effective dielectric Pore Size Distribution gt; specific surface area. To further validate the above conclusions, in order to obtain high specific capacitance of supercapacitor electrode materials, this paper, a mixed oxide of Ni-Co and Co-Mn mixed oxide prepared by chemical co-precipitation method, the results show that the mixed oxide by a mixture consisting of pure oxides, the degree of crystallinity of the resulting mixed oxide was small, and very small particles. Co _0.56 Ni _0.44 oxide 2-7 nm range sharp narrow mesoporous pore size distribution, and the maximum specific capacity 1227F / g, nearly pure NiO material 3 times. Mn _0.36 Co _0.64 oxide in the range of 2-20 nm, a sharp and narrow pore size distribution of mesoporous within the range of 20-140 nm wide but short pore size distribution; Mn _0.36 the Co _0.64 oxide than capacity of 370 F / g, close to the pure Mn ₃ O ₄ Material of about 7 times; additional electrochemical test results show that the resulting mixed oxide material having a good large-current discharge performance. Since hydrated ions in the electrolyte having a diameter of 6-7.6, so the pore size range of 8-50 the Faraday pseudocapacitive and the electric double layer capacitor for a must. Therefore, the effective pore size distribution is the main reason of the mixed oxide oxide material with high specific capacity. Further, the mixed oxide material has a unique pattern structure, we believe that this special structure helps in the transfer of OH-in the electrolyte to the electrode active material as well as in diffusion of redox white, so it is the high specific capacity of the material an important morphology foundation. 3 the directing agent Hydrothermal synthesis of NaY molecular sieve, and then with ammonium chloride and hydrochloric acid modified for USY and DUSY,, the last using simple chemical coprecipitation synthesized Ni (OH) ₂ / USY and out of the Co (OH) _{the 2} / USY composite as an electrode active material, the test results show that in the preparation of NaY Zeolite related factors by controlling the synthesis conditions, the controlled synthesis of required performance of molecular sieve. USY load on hydroxide, the outer surface of USY zeolite has undergone fundamental changes in the morphology of many pine needle hydroxides in the the zeolite surface three-dimensional direction directional growth, forming a loose accumulation with higher porosity porous nanomaterials. This dispersion of the active material has a very high specific surface area and within the range of nano-scale microstructure, prompting the active ions in the electrolyte, in the required power density, not only can be rapidly spread to the surface of the electrode, but also can be spread to The electrode body phase, full use of the electrode material is electrically active sites, redox reaction occurs to produce a high capacitance value. The specific capacity of the nickel hydroxide load an amount of 50% of the composite material obtained was 1670 F / g, and after the correction of the mass fraction of nickel hydroxide, nickel oxide, the corresponding pure hydrogen than the capacity of up to 3340 F / g. Than the highest capacity of the hydroxide of cobalt loading was 90% of the composite material obtained, up to 716F / g, and after the correction of the mass fraction of the cobalt hydroxide corresponding pure hydrogen cobalt oxide than the maximum capacity of up to 795 F / g. Be seen, when the composite material was prepared using USY zeolite as carrier, the ratio of capacitance of the single-electrode active material with a great degree of improvement. Prepared in the coprecipitation method with a simple Al-doped α-Ni (OH) ₂ electrode materials, the results show, the incorporation of aluminum can be suppressed to α-Ni (OH) _{2 ₂ transition to the β-Ni (OH),}, and increases the electrochemical reversibility of the electrode material, but does not play a role in the improvement of the discharge capacity. Its mechanism of action is that by raising the NiO layer between the number of positive charge, increasing anion bonding force between the NiO layer, and to ensure the stability of the anionic, water molecules are not lost, and the lattice constant. 7.5% Al-Ni (OH) ₂ of the highest ratio of the sample capacity of 2080F / g, and the material having a good large-current discharge characteristics and cycle stability. 5 in this paper for the first time as a positive Ni-Co mixed oxide, AC negative 2M KOH solution as electrolyte assembled into Ni-Co mixed oxide / AC hybrid supercapacitor and test its electrochemical properties; test results show based on Co0.56Ni0.44 oxide electrode potential of the capacitor window extended from 0.4V to 1.6V, and the capacity up to 97F / g, and exhibits excellent capacitor characteristics and large-current discharge performance. Electrochemical performance improvement thanks to the large specific surface area and proper pore size distribution of the activated carbon as the anode, can promote Co _0.56 Ni _0.44 oxides in a wide potential window within unobstructed the Faraday reaction, to maintain its excellent capacitance performance. CO _0.56 Ni _0.44 the oxides / AC hybrid capacitor having a high energy density and power density, power density of 133.3 W k / g when the energy density of 34.5 Wh k / g, and the energy density in the power density 1333.3 W k / g remained at 22.5 Wh of k / g.

Study on Metal Oxide and Its Composite Materials for Supercapacitor Electrode

Abstract

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