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|Title: ||以發泡鎳網作為鋅二次電池陽極集電網之電化學特性分析;Electrochemical characterization of using Ni foam as anode current collector for Zn-based secondary batteries|
|Keywords: ||鋅空氣電池;陽極;發泡鎳網;枝狀晶;Zn-air batteries;anode;Ni foam;dendrite|
|Issue Date: ||2016-10-13 12:45:59 (UTC+8)|
|Abstract: ||本研究採用商業發泡鎳網(Ni foam)作為鋅二次電池陽極集電網，主要為藉由其高比表面積之特性，抑制鋅陽極在充放電過程中鋅枝狀晶的形成，同時提升電極單位投影面積下鋅金屬的負載量。實驗採用三極式系統，置於含有飽和氧化鋅(ZnO)之6 M 氫氧化鉀(KOH)水溶液中執行電化學測試，並以鎳箔(Ni foil)作為實驗對照組。|
Ni foam於20 mA/cm2、50 mA/cm2、100 mA/cm2的電流密度下進行充放電20圈，皆具有穩定的循環效率。Ni foam於100 mA/cm2的電流密度下充電30分鐘，電極表面維持平坦且無枝狀晶生成，經過50%放電深度(DOD)充放電50圈之後，電極表面亦無明顯枝狀晶殘留。經循環伏安法及定電壓充電測定Ni foam之電化學活性面積約為Ni foil的3.5倍，闡述其多孔結構有助於分散實際單位面積的電流密度，為鋅金屬的沉積提供了更多空間，故能有效抑制在鹼性電解質中鋅枝狀晶的生成。
Ni foam最大可承受無枝狀晶生長電流密度介於110 mA/cm2至120 mA/cm2之間，約為Ni foil的5倍；在Ni foil與Ni foam皆無枝狀晶生長的電流密度下充電，Ni foam的最大負載量約為Ni foil的2倍，說明使用Ni foam作為鋅二次電池負極不僅可容許電池在大電流密度下充放電，單位面積電容量亦能提升為2倍，有利於鋅空氣二次電池在電動車領域的發展。
;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.
|Appears in Collections:||[化學工程與材料工程研究所] 博碩士論文|
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