(414b) Experimental Study On Zinc-Nickel Hydroxide Flow Battery

Zinc anode rechargeable batteries are amongst the most alternative systems for electrochemical energy storage because of the low cost of zinc and the high energy and power densities obtainable. The hydraulic ion required for the redox reaction with zinc can be supplied by an air cathode or by nickel hydroxide incorporated in a nickel matrix electrode. The primary problem with the use of zinc anodes in rechargeable batteries relates to dendrite formation upon charging. This non-uniformity in electrodeposition occurs due to the system being strongly non-linear and far from equilibrium, the processes being controlled by Poisson-type of equations for the diffusion and electrical fields. The method to change the control mechanism is mass transfer from diffusion control to convection control by making use of flowing electrolyte. This also allows reconditioning of the battery to as new by stripping the deposited zinc by deep discharge when needed.

The purpose of this study is to experimentally investigate the morphology of zinc on charging zinc-nickel hydroxide batteries with flowing electrolyte and to evaluate battery performance to obtain near optimum conditions. Galvanostatic cycling experiments were carried out. The results show that the batteries operate quite stably at the Coulomb efficiency of more than 90% for 300 cycles with reconditioning at every tens of cycles. The electrodeposition of zinc was fairly flat and dendritic structure was hardly observed. The flow velocity of the electrode was set to ~ 10 cm/s and this is slower than those in the past studies. This means that the energy consumption by the pump can be significantly reduced. Although further investigations is required for clarifying the more detailed features and to obtain better performance, it is proved that zinc-nickel hydroxide battery with flowing electrolyte is a reasonable, innovative, and promising battery with high efficiency and long cycle life.