無陽極鋰電池(AFLMBs)具有高理論能量密度、簡單的電池結構、更為低廉的製程成本和更為優良的安全性。然而，其中仍存在一些挑戰，尤其是銅集電器具有不均勻表面且與鋰親和性不足，導致循環壽命不佳、庫倫效率低落、金屬枝狀結晶的生成和不穩定的固態電解質介面(Solid Electrolyte Interface, SEI)，造成無陽極鋰電池的電化學性能惡化，最終使其應用受限。目前有許多研究著重於表面的修飾、電解質配方的調整或使用合適的電解質添加劑以改善無陽極鋰電池的電化學性能。根據先前文獻，氮化銅(Cu3N)修飾的銅集電器具有均勻分布的表面，且經過第一次鋰沉積後，氮化銅會被轉化成氮化鋰，進而有效抑制鋰枝狀結晶的生成和穩定SEI的結構。然而，在氮化銅(Cu3N)修飾的銅集電器表面上SEI的生成機制尚不明瞭。因此，在這項研究中，我們使用第一原理分子動力學(AIMD)探討以2M LiPF6、Ethylene Carbonate(EC)、Diethyl Carbonate(DEC)組成的電解質於氮化銅表面上生成SEI的反應性及分解反應機制。此外，我們還分析了添加劑氟代碳酸乙烯酯(Fluoroethylene carbonate, FEC)在SEI生成時所扮演的角色。為了探討在高電流量充電過程中集電器表面帶電後對於SEI生成的影響，我們以過量電子環境進行模擬，並且比較電解質於中性環境和過量電子環境中的還原分解途徑和電荷演化。在中性環境中，氮化銅表面會抑制LiF成分的生成和促進乙烯氣體(C2H4)的生成，令SEI的電子絕緣性變差且可能劣化SEI的結構穩定性。而電解質中加入FEC添加劑後可以增加SEI中LiF的含量，也能夠防止SEI形成時生成氣體。在過量電子環境中，氮原子從氮化銅向鋰層遷移進而生成氮化鋰(Li3N)，這有益於提升SEI的導離率。若電解質中加入FEC添加劑後，除了有利於提升SEI中LiF含量之外，更可以加速Li2O和Li3N的生成，進而提升SEI的結構穩定性。最重要的是，可以抑制電解質分解反應時氣體的生成。根據這些理論計算結果，我們預期含有FEC的電解質搭配氮化銅修飾後的銅集電器表面於高速的充電過程，可以提升SEI中LiF、Li2O 和Li3N的含量，進而改善無陽極鋰電池的結構穩定性。

Anode-Free Lithium Metal Batteries (AFLMBs) are gaining popularity due to their high theoretical energy density, simplified structure, lower cost, and improved safety. However, some critical issues, such as poor cycling lifespan, low Coulombic efficiency, notorious metal dendrite growth, and unstable SEI, impede their practical applications. This poor electrochemical performance was caused primarily by the lithiophobic and non-homogeneous surface of the bare copper (bare Cu) current collector. Various strategies for improving the electrochemical performance of AFLMBs have been proposed over the last few decades, including surface modification, electrolyte formulation, and the use of appropriate electrolyte additives. Cu3N-modified Cu collectors have been reported to suppress lithium dendrites and stabilize the SEI, where the Cu3N was converted to a Li3N after initial lithium plating, providing homogeneous electronic conductivity distribution on the electrode surface and improving cycling performance. The precise mechanism of SEI formation on Cu3N-modified Cu surfaces, however, remains unknown. Therefore, in this study, the reactivity of electrolyte consisting of 2M LiPF6, EC, and DEC on the Cu3N surface are investigated using ab initio molecular dynamics (AIMD) simulations. Furthermore, the role of the electrolyte additive FEC on the SEI formation mechanisms is analyzed. To approximate the effects of an electrified surface, an electron-rich environment of the electrolyte on the Cu3N surface is considered. The electrolyte reduction reaction pathways and Bader charges with respect to simulation time for both neutral and excess electron cases are analyzed and compared. In the neutral case, the Cu3N surface inhibited the formation of LiF species and induced the formation of C2H4 gas molecules. Whereas the presence of additive FEC in the electrolyte increased the LiF species in the SEI, preventing undesirable gas molecules from forming on the interface. In electron-rich environments, it is observed that the N atoms from the Cu3N are migrated into Li layers and form Li3N, which can further enhance the ion transport property of the SEI. However, solvent decompositions and the formation of undesirable gas molecules continue to occur during SEI formation in the LiPF6/EC/DEC mixture on the Cu3N surface under electron-rich conditions. The addition of additive FEC to the LiPF6/EC/DEC mixture, on the other hand, increases the abundance of LiF in the SEI film as well as the formation of other major SEI constituents such as Li2O and Li3N and, most importantly, prevents gas formation. Based on these theoretical calculations, it is expected that Cu3N-modified Cu surfaces with FEC-containing electrolytes will increase the LiF, Li2O, and Li3N contents in the SEI film during the high-rate charging process, thereby improving the structural stability of AFLMBs.

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