| 摘要: | 因應全球暖化問題以及科技的不斷進步，我們需要尋找可持續和更加環保的能源儲存解決方案。因此，無陽極鋰金屬電池(anode-free lithium metal batteries, AFLB)因為具有高能量密度而引起了廣泛的研究。然而，AFLB的研究存在一些問題，其中一個主要的問題是在鋰沉積過程中可能形成的枝晶鋰，造成AFLB的陽極循環穩定性不佳，甚至導致電池短路。為了克服這些挑戰，近期的研究發展一種人工固態電解質界面膜(artificial solid electrolyte interphase, ASEI)來改善此瓶頸。其中，ASEI是一種功能性薄膜，過去常用有機或無機的材料來達成，其用於保護鋰金屬陽極並優化其性能。但對於提高鋰沉積的效率與材料穩定性，以及增加電池的循環壽命仍不理想。
本研究中，通過使用電泳沉積法(electrophoretic deposition, EPD)沉積氟化電化學剝離石墨烯(FECG)及電化學剝離石墨烯(ECG)來製備新型態複合多層膜結構的ASEI並研究其電化學基礎特性。複合多層膜上層為FECG塗層，具有高的親鋰性並能達到均勻填鋰，以及下層漸變為ECG層，其具有導電特性能傳輸電子，底層則為薄層之FECG，其可與銅基材有高的接著穩定性，這種複合多層膜在機制上，藉由親鋰層向下擴散，並由所設計的漸變層，讓鋰沿片層間通道向下的過程，可由導電子ECG轉移下方電子，而還原鋰離子，藉此高效地促進鋰於ECG/FECG界面均勻沉積，並維持鋰沉積/脫鋰的庫倫效率跟結構穩定性。我們發現此複合多層ASEI膜，其半電池具有低的成核過電位(46.1 mV)和較低的過電壓(81.8 mV)，且隨著循環次數的增加，過電壓降低，因此可提升填鋰效率。在第325次循環後庫倫效率(Coulombic efficiency, CE)仍維持97.2 %，具有高的穩定性，並且極化曲線特性可穩定循環達600 hr。而在全電池(NMC-622//ML)測試中，第150次循環後比容量仍超過120 mAh/g，於第160次循環時電容維持率為72 %。此外，藉由材料分析，包含鋰沉積/脫鋰的微結構形貌、化學鍵結組成，探討複合ASEI膜中鋰沉積的行為機制，這一關鍵技術的應用有望解決AFLB面臨的挑戰，使其成為更安全且高能量密度的儲能電池。
;In response to global warming and the continuous advancement of technology, there is a growing demand for sustainable and environmentally friendly energy storage solutions. Consequently, the research focus has turned towards anode-free lithium metal batteries (AFLB) due to their high energy density. However, AFLB research faces challenges, notably the formation of dendritic lithium during lithium deposition, which undermines the stability of the anode and can lead to battery short-circuiting. Recent studies have thus aimed to address this issue by developing an artificial solid electrolyte interphase (ASEI) as a solution. ASEI, typically a functional thin film composed of organic or inorganic materials, is designed to protect the lithium metal anode and enhance its performance. Yet, improving lithium deposition efficiency, material stability, and increasing battery cycle life remains an ongoing challenge.
This study explores a novel approach by employing electrophoretic deposition (EPD) to fabricate a new type of composite multilayer ASEI structure using fluorinated electrochemically exfoliated graphene (FECG) and electrochemically exfoliated graphene (ECG). The upper layer consists of FECG, which exhibits high lithium ion conductivity enabling uniform lithium plating. Transitioning below is the ECG layer, known for its electron conductivity, facilitating efficient electron transfer, with a thin FECG layer at the base ensuring robust adhesion to the copper substrate. Mechanistically, this composite multilayer ASEI facilitates uniform lithium deposition by guiding lithium ions through its conductive layers and gradual transitions, thereby promoting efficient lithium plating and stripping processes at the ECG/FECG interface, maintaining high Coulombic efficiency and structural stability.
The fabricated composite multilayer ASEI membrane demonstrated promising electrochemical characteristics, including low nucleation overpotential (46.1 mV) and reduced polarization (81.8 mV), which diminish with cycling, indicating enhanced lithium plating efficiency. After 325 cycles, the Coulombic efficiency remained high at 97.2 %, underscoring its stability. Polarization curves remained stable for up to 600 hours. In full-cell (NMC-622//ML) testing, the specific capacity exceeded 120 mAh/g after 150 cycles, with capacity retention at 72 % after 160 cycles. Additionally, material analysis of lithium deposition behaviors within the composite ASEI membrane, including microstructural morphology and chemical bonding composition during lithium plating and stripping, elucidated the mechanism behind its performance.
These findings suggest that the application of this composite multilayer ASEI membrane holds promise in addressing the challenges faced by AFLB, potentially advancing safer and higher energy density energy storage batteries. |
