1 research outputs found
Performance Enhancement and Side Reactions in Rechargeable Nickel–Iron Batteries with Nanostructured Electrodes
We
report for the first time a solution-based synthesis of strongly
coupled nanoFe/multiwalled carbon nanotube (MWCNT) and nanoNiO/MWCNT
nanocomposite materials for use as anodes and cathodes in rechargeable
alkaline Ni–Fe batteries. The produced aqueous batteries demonstrate
very high discharge capacities (800 mAh g<sub>Fe</sub><sup>–1</sup> at 200 mA g<sup>–1</sup> current density), which exceed that
of commercial Ni–Fe cells by nearly 1 order of magnitude at
comparable current densities. These cells also showed the lack of
any “activation”, typical in commercial batteries, where
low initial capacity slowly increases during the initial 20–50
cycles. The use of a highly conductive MWCNT network allows for high-capacity
utilization because of rapid and efficient electron transport to active
metal nanoparticles in oxidized [such as FeÂ(OH)<sub>2</sub> or Fe<sub>3</sub>O<sub>4</sub>] states. The flexible nature of MWCNTs accommodates
significant volume changes taking place during phase transformation
accompanying reduction–oxidation reactions in metal electrodes.
At the same time, we report and discuss that high surface areas of
active nanoparticles lead to multiple side reactions. Dissolution
of Fe anodes leads to reprecipitation of significantly larger anode
particles. Dissolution of Ni cathodes leads to precipitation of Ni
metal on the anode, thus blocking transport of OH<sup>–</sup> anions. The electrolyte molarity and composition have a significant
impact on the capacity utilization and cycling stability