近年來，眾多學者致力於解決轉化型電極材料在充放電過程中的體積膨脹與電容衰減問題。然而，多數研究仍主要依賴實驗手法，對於轉化型電極材料的模擬研究相對較少。為填補此領域的空缺，本研究採用第一原理計算，探討知名電極材料之一：一磷化鐵及其改質後的電極材料。一磷化鐵以其低成本和高電容的優勢著稱，與石墨烯結合後更可有效抑制充放電過程中的體積膨脹。此外，實驗結果也證實，銅元素摻雜能顯著提升一磷化鐵的導電性與電容表現。 本研究首先根據文獻構建一磷化鐵@石墨烯的模型，並進行結構優化。在單顆鈉原子的吸附中，發現其在複合材料中的吸附效果優於單獨吸附於一磷化鐵或石墨烯的情形。隨著鈉原子濃度增加，我們觀察到原子簇體積變化與平均吸附能出現轉折點，這暗示電極材料由嵌入反應轉變為轉化反應。藉由部分態密度 (Partial Density of States) 分析，更進一步確定發生轉化反應所需要的鈉原子數為八顆。此外，我們計算了鈉原子的擴散能障、開路電壓與電容。在銅原子於一磷化鐵參雜的討論中，我們證實銅的摻雜可有效增強鈉原子在電極材料中的吸附行為。 ;In recent years, various strategies have been proposed to address the challenges of significant volume changes and capacity degradation in conversion-type electrodes. While most research has concentrated on experimental approaches, relatively few have focused on simulation studies. This study seeks to utilize density functional theory (DFT) to investigate one of the most famous conversion type electrodes, FeP and its modifications. FeP offers low cost and high theoretical capacity, and combining it with graphene (FeP@graphene) helps mitigate volume variation. Additionally, Cu doping in FeP has been shown to improve both conductivity and capacity. We firstly constructed the model of FeP@graphene based on experimental studies, and subsequently performed geometry optimization. The single Na adsorption showed that the adsorption behavior is stronger when Na is adsorbed between composite materials compared to being solely adsorbed on FeP or graphene. Following this, the number of Na atoms in the anode was increased, and an inflection point occurred at high Na ratios, based on cluster volume and the average adsorption energy calculations. This indicated a transformation in the mechanism from intercalation to conversion. The number of Na atoms required for conversion reaction was further confirmed to be 8 through the Partial Density of States (PDOS) analyze. Additionally, the diffusion energy barrier of a Na atom, open-circuit voltage (OCV), and the anode capacity were calculated. The effect of Cu doping in FeP was also examined, and it was found that Cu enhances the adsorption of a Na atom.
