原位聚合生成雙鋰鹽系統類凝膠聚(1,3-二氧戊環)電解質應用於鋰離子電池之研究;In Situ Polymerization of Dual-Salt Poly(1,3-dioxolane) Gel-Like Electrolyte for Lithium-Ion Batterie義

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Title:	原位聚合生成雙鋰鹽系統類凝膠聚(1,3-二氧戊環)電解質應用於鋰離子電池之研究;In Situ Polymerization of Dual-Salt Poly(1,3-dioxolane) Gel-Like Electrolyte for Lithium-Ion Batterie義
Authors:	洪章堯;Hong, Jhang-Yao
Contributors:	化學工程與材料工程學系
Keywords:	鋰離子電池;原位聚合生成法;雙鋰鹽系統;1,3-二氧戊環;類凝膠電解質;Lithium-ion batteries;In situ polymerization;Dual-salt system;1-3,dioxolane;Gel-Like Electrolyte
Date:	2023-08-11
Issue Date:	2023-10-04 14:43:08 (UTC+8)
Publisher:	國立中央大學
Abstract:	高能量密度的鋰離子電池有著廣泛的應用，但安全風險始終阻礙其更廣泛的發展。由於傳統電池中的液體電解質(Liquid Electrolyte, LE)是電池危害的主要來源。為了避免與 LE相關的安全性問題，開發更穩定、更安全的電解質是一個重要的議題。傳統固態電解質多以外部生成電解質薄膜的方式製備，容易受到固體與固體之間不均勻的界面限制，因此本研究採用原位聚合生成(In situ polymerization)製備具有固液特性的凝膠狀電解質解決了傳統固態電解質不均勻界面限制的問題，並且減少了短路造成的熱失控相關問題，是一種可行的策略。本研究採用1,3-二氧戊環(1,3-dioxolane, DOL)與碳酸乙烯酯(Ethylene Carbonate, EC)添加雙(三氟甲基磺醯)氨基鋰(lithium bis(trifluoromethanesulfonyl) imide, LiTFSI)作為鋰鹽以及六氟磷酸鋰(lithium hexafluorophosphate, LiPF6)作為誘發劑引發DOL溶劑開環聚合，形成類凝膠電解質(Gel-Like Electrolyte , GLE)。透過調整誘發劑和鋰鹽濃度的比例以討論聚合度對離子電導率以及鋰離子轉移數的影響，並得到最佳比例的GLE。所得的GLE表現出高聚和度84.3%，並擁有4.16x10-5(S/cm)的離子電導率以及高鋰離子轉移數0.63，同時也良好的電化學穩定性(>5.0 V) 保持其結構完整性。在1.0 mA/cm2電流密度超過1000小時以上的穩定鋰沉積與剝落行為可以避免形成鋰枝晶造成短路和熱失控相關問題。應用於LFP電池展示出高達161.8 mAh/g的電容量在0.1 C充放電條件下，並且1.0 C充放電速率條件下200圈循環後仍有133.0 mAh/g的電容量，而在高電壓NCM811電池應用中，展現出202.6 mAh/g的初始電容量在0.2 C時，並且循環100圈後，仍有70.7 %的電容保持率。綜合上述，本研究所使用的類凝膠電解質表現出優秀的電化學性能應用在LFP與NCM811電池，同時對環境友善的材料與製程，有助於鋰離子電池更廣泛的發展應用。 ;High-energy density lithium-ion batteries have widely applications, but their development is hindered by safety risks. The liquid electrolyte (LE) in conventional batteries is the main source of hazards. To address the safety issues associated with LE, it is crucial to develop more stable and safer electrolytes. In this regard, traditional solid-state electrolytes often poor contact due to the formation of solid-solid interfaces. Therefore, this study proposes an in-situ polymerization method to synthesize a gel-like electrolyte (GLE) with solid-liquid characteristics, which overcomes the limitations of traditional solid-state electrolytes, making it a viable strategy. In this study, 1,3-dioxolane (DOL) and ethylene carbonate (EC) were used as solvents, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium hexafluorophosphate (LiPF6) were used as initiators to induce the ring-opening polymerization of DOL. This resulted in the formation of gel-like electrolyte. By adjusting the ratio of initiators and lithium salts, the influence of degree of polymerization on ion conductivity and lithium ion transference number was investigated, leading to the optimal ratio of gel-like electrolyte. The obtained GLE exhibited a high polymerization degree of 84.3%, an ion conductivity of 4.16x10-5 S/cm, and a high lithium ion transference number of 0.63. It also demonstrated good electrochemical stability (>5.0 V) while maintaining its structural integrity. Stable lithium ion stripping and plating were achieved for over 1000 hours at a current density of 1.0 mA/cm2, preventing the formation of lithium dendrites and associated short-circuit and thermal runaway issues. When applied to LFP batteries, it demonstrated a high capacity of 161.8 mAh/g under 0.1 C charging/discharging conditions. Even after 200 cycles at a charging/discharging rate of 1.0 C, it still maintained a capacity of 133.0 mAh/g. In high-voltage NCM811 battery applications, it demonstrates an initial capacity of 202.6 mAh/g at 0.2 C, with a capacity retention of 70.7% after 100 cycles. In conclusion, the developed GLE in this study exhibited excellent electrochemical performance when used in LFP and NCM811 batteries. Moreover, its environmentally friendly materials and processes contribute to the wider development and application of lithium-ion batteries.
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