| Summary: | 碩士 === 國立中央大學 === 化學工程與材料工程學系 === 104 === Zinc is one of the most commonly used materials for batteries ascribed to its abundance, high energy density, well reversibility, and eco-friendliness. Unfortunately, Zn-based secondary batteries typically suffer from short lifetimes due to the dendrite formation during charging process. The inhibition of dendrite growth has been extensively studied. However, most of the strategies were adding additives into electrode or electrolyte, which may decrease the efficiency of batteries. Hence we expect to develop a physical method to prevent dendrite formation. In this work, Ni foam was used as the current collector in an alkaline electrolyte composed of 6 M KOH with saturated ZnO. In a parallel experiment, Ni foil was also used for comparison.
Electrochemical analysis and scanning electron microscopy (SEM) were utilized to evaluate the performance of Ni foam and Ni foil electrodes. The Ni foam exhibited a superior cycling stability during deep charge-discharge, at current densities of 20, 50, and 100 mA/cm2. It was found that Zn deposited uniformly on Ni foam through the constant current density of 100 mA/cm2, charging for 30 min. Additionally, no dendrite formation was observed after 50 cycles of 50% depth-of-charge. The current-time profile of Ni foam was also more stable than that of Ni foil at constant voltage of -1.7 V, suggesting a significant surface morphology control of Zn deposit using Ni foam.
Through cyclic voltammetry(CV) as well as potentiostatic electrodeposition results showed that Ni foam carried about 3.5 times larger electrochemically active surface area than Ni foil. The maximum dendrite free current density of Ni foam is between 110 mA/cm2 and 120 mA/cm2, which is also about 4-5 times larger than that of Ni foil. In addition, the maximum load of Ni foam is twice of Ni foil under dendrite free current density.
This study has demonstrated that the porous nature of Ni foam can suppress Zn dendrite formation effectively in the alkaline solution. Furthermore, Ni foam carried a higher load of Zn deposits than Ni foil as well as better tolerance under high current density. Accordingly, Ni foam could be a well choice of anode current collector for Zn-based secondary batteries.
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