應用於鋁硫電池原位X光繞射分析的金屬集流體之研究

Investigation on Metal Current Collectors for In-situ X-ray Diffraction Analysis of Aluminum-sulfur Batteries

目前全球正面臨著嚴峻的化石能源導致的高碳排放危機，可再生能源發電與儲能裝置為未來改善此問題的核心技術之一。在此背景前提下，鋁硫電池作為一種高能量密度、高安全與低成本的電化學儲能技術，使用金屬鋁單質和硫兩種低成本與蘊藏量豐富的元素作為負極和正極，可實現高容量(理論容量，鋁：2982毫安時/克；硫：1675毫安時/克)儲能，但鋁硫電池面臨著單質硫在充放電時之相變化過程不明確，導致循環穩定性差等挑戰。本研究開發原位X光繞射分析平台用於深入理解相變化過程，首先採用熔融擴散法來製作所需要的硫碳正極材料（硫含量：18-77 wt.%），後將正極材料塗佈於鈹、鎳與鋁等正極金屬集流體之上並應用於充放電過程，充放電循環期間的原位分析有助於理解電化學穩定性和相關現象。研究結果指出，金屬鈹會在充放電過程中被腐蝕而導致穿孔。金屬鎳則是由於其對於X光的高吸收度，導致其X光繞射分析訊號微弱。金屬鋁則兼具電化學穩定性與低X光吸收度；且其內電阻相較於金屬鎳集流體組成的電池低五倍以上。綜上，在原位X光繞射分析的應用中，金屬鋁箔有潛力成為一種電化學穩定且低成本的金屬集流體材料。

The world is currently grappling with a major crisis related to excessive carbon emissions, mainly caused by fossil fuel energy use. This situation highlights the urgent need to develop and implement alternative technologies. Renewable energy generation and energy storage equipment play a vital role in solving this problem. In the current context, aluminum-sulfur batteries have emerged as a promising electrochemical energy storage technology due to their high energy density, safety properties, and cost-effectiveness. These batteries can achieve large capacities by utilizing aluminum as the anode and sulfur as the cathode, two economically viable and readily available elements. The theoretical capacity of aluminum is 2982 mAh/g, while that of sulfur is 1675 mAh/g. However, the unclear phase transition of elemental sulfur during charge-discharge cycles poses challenges, resulting in insufficient cycle stability. This study aims to develop an in-situ X-ray diffraction analysis platform to enhance our understanding of the phase transition mechanisms that occur in aluminum-sulfur batteries. Initially, sulfur-carbon cathode materials were synthesized using a melt diffusion method with sulfur contents varying from 18 to 77 wt.%. The cathode material is then applied as a coating to the metal current collector, including beryllium, nickel, and aluminum. In situ analysis during charge-discharge cycles contributes to a comprehensive understanding of electrochemical stability and related phenomena. Research shows that beryllium metal corrodes when it undergoes charge and discharge cycles, resulting in perforations. Metallic nickel exhibits a weakened X-ray diffraction signal due to its significant X-ray absorption, thus limiting its applicability in analytical studies. In comparison, aluminum is a very promising candidate as a metallic current collector material due to its electrochemical stability and low X-ray absorptivity. Furthermore, the internal resistance of batteries using aluminum current collectors was observed to be five times lower than that of batteries using nickel current collectors. Therefore, in the application of in-situ X-ray diffraction analysis, aluminum foil has the potential to become an electrochemically stable and cost-effective metal current collector material.