Preparation And Properties Of Electrode Materials For Electrochemical Capacitor And Ni/MH Alkaline Rechargeable Batteries

At present, electrochemical capacitor and nickel/mental hydride (Ni/MH) battery are two kinds of important energy storage equipments. Electrochemical capacitor is a new type of energy storage equipment, which combines the advantages of both dielectric capacitors that can deliver high power within a very small period and conventional rechargeable batteries that have high energy densities. Therefore, electrochemical capacitors have a wide range of applications and have already become one of the research interests related to new chemical energy sources studies. At the same time, alkaline rechargeable batteries such as Ni/metal hydride (Ni/MH) are widely applied to today's market covering domains ranging from power tools to portable electronics and electric vehicle. Furthermore, nickel/metal hydride (Ni/MH) batteries are considered to be one of the most promising choices for electric vehicle (EV) and hybrid electric vehicle (HEV) applications due to high power and low cost.In this work, we have prepared relevant electrode materials of electrochemical capacitor and nickel/mental hydride (Ni/MH) battery, and studied the electrochemical performance, structural and morphological characterizations of these nanomaterials in detail. The main content is as follows:1. Nanostructured SnO2 was prepared by the sol–gel method. Aniline monomer was polymerized in the suspension of nanocrystalline SnO2 to form inorganic-organic composite materials, in which SnO2 nanoparticles were embedded within netlike polyaniline (PANI). Structural and morphological characterizations of SnO2 and PANI/SnO2 were carried out using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Their electrochemical properties were also investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The as-prepared composites had excellent properties in the capacitance, and its specific capacitance was up to 305.3 F g–1 with a specific energy density of 42.4 Wh kg–1 and a coulombic efficiency of 96%. The results indicated that the PANI/SnO2 had a synergistic effect of the complementary properties of both components. 2. A novel nanostructured mesoporous CoxNi1–x layered double hydroxides (CoxNi1–x LDHs), which both Co(OH)2 and Ni(OH)2 exhibitαphase, have been successfully synthesized by a chemical co-precipitation route using polyethylene glycol as the structure-directing reagent. Structural and morphological characterizations were performed using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The component and thermal stability of the sample were measured by energy dispersed X-ray spectrometry (EDS), FT–IR and thermal analyses, including thermogravimetry (TG) and differential thermal analysis (DTA). Cyclic voltammogram and galvanostatic charge-discharge testified that the CoxNi1–x LDH has a specific capacitance of 1809 F g–1 at a current density of 1 A g–1 and remains at about 90.2% of the initial value after 1000 cycles at a current density of 10 A g–1. The relationship between the chemical composition and capacitance is discussed.3. The fourα-cobalt hydroxides (green or blue) with different intercalated anions were synthesized by a chemical precipitation route in which polyethylene glycol was used as the structure-directing reagent for application in the electrode materials of electrochemical capacitors. Every one among the four samples displays an interesting and distinctive morphology although the synthesis conditions were same except for anions. The intercalated anions have a critical effect on the basal plane spacing, morphologies and capacitive properties of the products. Structural and morphological characterizations were performed using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The component and thermal stability of the sample were respectively measured by FT–IR and thermal analyses, including thermogravimetry (TG) and differential thermogravimetry (DTG). The electrochemical behaviors were measured by cyclic voltammogram and galvanostatic charge-discharge. The specific capacitance is up to 697 F g–1 at a charge-discharge current density of 1 A g–1 for the sample with intercalated chlorine. But the sample with intercalated sulfate, which has small crystalline size, more disordered structure and almost perfect alveolate nanostructure with a large surface area, exhibits relatively poor specific capacitance (420 F g–1 ). The exceptive phenomena caused by intercalated anions were explained by hydrogen bonding and electrostatic forces. Moreover, the relationships between the specific capacitance, basal plane spacing as well as the content of the interlayer water were discussed in detail for the four as-synthesized samples.4. A nanostructured curly laminarβ-nickel hydroxide was successfully synthesized by a chemical precipitation route in which polyethylene glycol was used as the structure-directing reagent. Structural and morphological characterizations were performed using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The component and thermal stability of the sample were respectively measured by FT–IR and thermal analyses, including thermogravimetry (TG) and differential thermal analysis (DTA). Its electrochemical properties were evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge technique in 6 M KOH aqueous electrolyte. The results showed that the nanostructured curly laminarβ-Ni(OH)2 exhibits a high electrochemical capacity of up to 274 mAh g–1.5. A board-like Al-substitutedα-Ni(OH)2 were synthesized via a optimizing chemical precipitation method, in which polyethylene glycol was used as the structure-directing reagent. Structural and morphological characterizations of these nanomaterials were performed using powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The experimental results of XRD show that the samples are typicalα-phase. The component and thermal stability of the sample were respectively measured by FT–IR and thermogravimetry (TG-DTA). The SEM results show that the Al-substitutedα-Ni(OH)2 displays board-like morphology. Its electrochemical properties were evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge technique in 6 M KOH aqueous electrolyte. The results show that a maximum capacity of 331 mAh g–1 for 10%Al-substitutedα-Ni(OH)2 were obtained at 0.2C rate.