| 摘要: | 因應全球暖化與科技進步的需求，開發具可持續性與高能量密度的儲能系統已成為關鍵課題。因此，鋰金屬電池(Lithium Metal Batteries, LMBs)因為具備極高的理論比容量(3860 mAh g⁻¹)以及最低電化學電位(-3.04 V vs. SHE)，被廣泛視為下一世代高能量密度儲能系統的理想負極材料。然而，實際應用上卻受到嚴重限制，面臨的挑戰包括枝晶鋰生成導致在沉積過程中容易刺穿隔膜，引發短路與熱失控以及界面不穩定使電解液與鋰金屬的副反應生成不均勻、低機械強度和低導鋰性的固態電解質界面(Solid Electrolyte Interphase, SEI)，導致庫倫效率(Coulombic Efficiency, CE)下降與循環壽命縮短。
為了克服上述問題，過去研究提出人工固態電解質界面(Artificial Solid Electrolyte Interphase, ASEI)概念，以兼具高強度與高導鋰性的保護層來穩定界面。氟化鋰(LiF)因具備高機械強度(~58 GPa)與化學穩定性，被廣泛應用於抑制枝晶穿透與降低副反應，氮化鋰(Li3N)則具有高導鋰性(~10-3 S cm-1)，能促進鋰離子快速傳輸並引導均勻沉積，此外，氧化鋰(Li2O)在適中氧含量下生成比例較高，能提供穩定的導鋰通道並減少過多氧轉化成Li2CO3。石墨烯基材料因高比表面積與優異導電性，被視為理想的鋰沉積載體。傳統電極添加黏著劑與助導劑，但這些成分容易引發副反應，降低穩定性，而無黏著劑(Binder-Free)能抑制額外副反應之干擾，展現更高的界面穩定性與電子及離子傳輸效率。
本研究利用電泳沉積法(Electrophoretic Deposition, EPD)將氟化電化學剝離石墨烯(FG)與電化學剝離石墨烯(ECG)沉積於銅基底，製備Binder-Free電極，透過不同電漿處理引入氟氮雙功能，探討氧含量與氟氮比例對ASEI的影響。結果顯示，高氮含量促進Li3N的生成，降低成核過電位至62 mV，並於橫截面觀察到鋰沉積深度達4.25 μm，顯示其能有效改善導鋰性，高氟含量則促進LiF的形成，在循環257次時仍能維持93.8 % 的CE，證實其優異的機械支撐性與化學穩定性，而適中氧含量則生成更多Li2O，提供額外導鋰通道並提升界面穩定性。此外，退火處理進一步修復缺陷並強化碳結構，顯著延長循環壽命，證明透過合理調控氟、氮與氧，可設計兼具高穩定性與高導鋰性的ASEI。
;In response to the urgent demand for sustainable and high–energy-density storage systems driven by global warming and technological advancement, lithium metal batteries (LMBs) have emerged as one of the most promising candidates for next-generation energy storage. Benefiting from an ultrahigh theoretical specific capacity (3860 mAh g-1) and the lowest electrochemical potential (-3.04 V vs. SHE), lithium metal is regarded as an ideal anode material. However, its practical application is severely hindered by the formation of lithium dendrites, which can penetrate the separator and cause short circuits and thermal runaway. In addition, unstable interfacial reactions between the electrolyte and lithium metal lead to the formation of a heterogeneous solid electrolyte interphase (SEI) with low mechanical strength and poor ionic conductivity, resulting in reduced Coulombic efficiency (CE) and shortened cycle life.
To overcome these issues, the concept of an artificial solid electrolyte interphase (ASEI) has been proposed, aiming to design protective layers with both high mechanical robustness and excellent Li-ion conductivity. Lithium fluoride (LiF), with a high mechanical modulus (~58 GPa) and chemical stability, has been widely used to suppress dendrite penetration and mitigate side reactions. Lithium nitride (Li3N), featuring high ionic conductivity (~10-3 S cm-1), facilitates rapid Li-ion transport and promotes uniform deposition. Furthermore, lithium oxide (Li2O), when formed under moderate oxygen content, provides stable Li-ion diffusion channels while preventing excess oxygen from transforming into Li2CO3, thereby enhancing interfacial stability. Graphene-based materials, owing to their high surface area and excellent electronic conductivity, are considered ideal hosts for Li deposition. In contrast, traditional electrodes require the use of binders and conductive additives, which often introduce additional side reactions and degrade interfacial stability. Binder-free electrodes can eliminate such inactive components and interference, thereby exhibiting higher interfacial integrity and improved electronic/ionic transport efficiency.
In this work, fluorinated electrochemically exfoliated graphene(FG) and electrochemically exfoliated graphene (ECG) were deposited on Cu foils using electrophoretic deposition (EPD) to fabricate binder-free electrodes. By applying different plasma treatments, dual-functional graphene containing both fluorine and nitrogen was constructed, and the effects of oxygen content and F/N ratio on ASEI performance were systematically investigated. The results demonstrate that high nitrogen content promotes Li3N formation, reducing the nucleation overpotential to 62 mV and enabling lithium deposition at greater depths (4.25 μm), thereby improving ionic transport. High fluorine content facilitates the formation of LiF, maintaining a CE of 93.8 % after 257 cycles and providing excellent mechanical and chemical stability. Meanwhile, moderate oxygen content enhances the generation of Li2O, which further stabilizes the interface and promotes Li-ion diffusion. The optimized electrode achieved over 450 hours of stable cycling with CE above 93 %. Moreover, annealing treatment effectively repaired structural defects and reinforced the carbon framework, significantly extending cycle life.
These findings confirm the complementary roles of LiF, Li3N, and Li2O within ASEI and highlight that rational tuning of fluorine, nitrogen, and oxygen contents, combined with defect-healing annealing strategies, can yield a stable artificial interphase with both high mechanical strength and ionic conductivity. This work provides new insights into designing advanced ASEIs for high–energy-density lithium metal batteries. |
