The Fabrication,Properties And Application Of Nanostructured Array Electrodes In New Types Of Nickel-iron Batteries

Nickel-iron rechargeable batteries possess the advantages of high energy density,high power density, abundant raw material, low price and environmental friendship.These advantages make this battery a powerful competitor for the next new generation of green power batteries. However, there are some obvious shortcomings in the nickel-iron rechargeable batteries before it is widely commercialized. The main drawback is that the battery has poor cycle stability. In addition, with the development of wearable smart devices,the demand for flexible energy storage devices are increasing, the development of flexible nickel-iron rechargeable batteries needs to be studied. Through preliminary studies, it is found that the poor dispersion of the nickel-iron rechargeable batteries is mainly due to the expansion of the bulk of the active material of the iron negative material during the repeated charging and discharging process. In this thesis, in the first place, improving the cycle stability of the negative material by facile and reproducible successive electrodeposition, then with copper-nickel oxide nanowire as positive material, a new type of nickel-iron rechargeable battery was fabricated and its energy storage characteristics were studied systematically; Secondly, through doping and surface modification to improve the cycle stability of the negative electrode, then with copper-nickel oxide nanowire as positive material, we not only assembled aqueous nickel-iron rechargeable battery, but also prepared a flexible quasi-solid nickel-iron rechargeable battery with KOH/PVA gel as electrolyte and their energy storage characteristics were studied systematically.The main research contents of my thesis are as follows:1. By using facile hydrothermal route, FeOOH nanorods arrays were uniformly grown on carbon cloth. Then through the electrodeposition method and high temperature annealing, FeOOH nanorods arrays were converted to uniform Fe₃O₄@MoO₂ nanorods. MoO₂ coating not only increased the conductivity but also help maintaining the integration of nanorod array. The three-electrode-testing results showed that our Fe₃O₄@MoO₂ composite nanorods arrays exhibit excellent storage capacity and stable cycling performance compared with pure Fe2O3 nanorods; The copper-nickel oxide nanowire grown directly on a carbon cloth was used as a positive electrode, a novel thin film type nickel-iron rechargeable battery was assembled. Both negative and positive materials were grown on carbon cloth directly. In the water system full battery test, with potassium hydroxide aqueous solution as the electrolytic solution, the thin film type nickel-iron rechargeable alkaline battery has 1.2 V discharge platform voltage at current density of 2 mA/cm²; After cycling at a current density of 10 mA/cm² for 400 times,the battery can maintain 60% of initial capacity.2. By using facile hydrothermal route, FeOOH nanorods arrays were uniformly grow on carbon cloth. Then adding glucose solution on the FeOOH nanorods arrays directly, under high temperature annealing, FeOOH nanorods were converted to Fe₃O₄@C composite material. We denoted as "carbon glue",and "carbon glue" coating not only increase the conductivity but also help maintaining the integration of nanorod array. The three-electrode-testing results showed that by combining the advantages of both structural design and carbon coating, our Fe₃O₄@C composite electrode material exhibit excellent storage capacity and stable cycling performance compared with pure Fe2O3 nanorods. With the copper-nickel nanowires grown directly on the carbon cloth as the positive electrode, the aqueous nickel-iron rechargeable alkaline batteries were obtained by using the potassium hydroxide as the electrolytic solution. In the full cell test, the nickel-iron rechargeable battery has the discharge voltage platform of 1.2 V at a current density of 1.5 mA/cm²; After cycling at a current density of 12 mA/cm² for 2000 times, the battery can maintain 82% of initial capacity. In addition, with KOH/PVA gel as the electrolyte, we successfully prepared a flexible quasi-solid nickel-iron rechargeable battery. The electrochemical results showed that our flexible battery device exhibit high volumetric energy density ?3.34 mWh/cm³?, high volumetric power density ?278.24 mW/cm³?; After cycling at a current density of 10 mA/cm² for 5000 times, the battery can maintain 85% of initial capacity.