應用於鋰離子電池之鈉超離子導體型固態電解質界面修飾

Interface Modification of Na Superionic Conductor (NASICON)-Type Solid-State Electrolyte for Lithium-Ion Batteries

賴彥銘(Yan-Ming Lai)

指導教授 ： 劉如熹

國立臺灣大學/理學院/化學系/碩士(2023年)

https://doi.org/10.6342/NTU202301007

摘要

為因應全球暖化之氣候變遷議題，各國皆以節能減碳之策略為目標。提升儲能效率乃節能之首要任務，鋰離子電池為儲能系統之大宗。然，傳統式液態電解質之可燃性為安全隱患。故，具阻燃性與高能量密度之無機固態電解質乃為電池研究之焦點。
本研究第一部分將探討鈉超離子導體型(NASICON)固態電解質(Li1.5Al0.5Ge1.5(PO4)3; LAGP)與鋰金屬之界面失效問題。組裝Li|LAGP|LiFePO4電池並藉X光繞射儀分析(012)晶面消失之原因，經各項光譜如FT-IR、Raman與XPS以證實LAGP之受腐蝕之過程，由TOF-SIMS與AFM證實該反應生成混合導電界面層。此外，經對稱電池之測試結果，揭示離子與電子傳輸對LAGP 之電化學腐蝕反應具相同重要之作用。
第二部分之研究以複合式聚合物電解質(composite polymer electrolyte; CPE)為LAGP與鋰金屬間之界面層，以避免LAGP與鋰金屬接觸而引發界面失效。藉石榴石型(garnet-type)固態電解質(Li6.4La3Zr1.4Ta0.6O12; LLZTO)粉末以及丁二腈(succinonitrile; SN)共同引入PEO基聚合物電解質，以配製為界面修飾層之複合式聚合物電解質。導入各項填料(filler)之結果將促使聚合物具優異電化學性能，鋰離子導電率將提升一數量級。該電解質將作為LAGP之界面修飾層，於Li|CPE|LAGP|CPE|Li對稱電池之電化學測試中，保持穩定達300小時且具75 mV之低過電位，而Li|CPE|LAGP|LiFePO4全電池測試之放電容量達136 mAh/g且於75次循環之放電容量保持率達90%。
本研究之新穎性為基於文獻報導之失效反應，深入探討實質原理，並藉各項儀器揭示失效機制之另一觀點。此外，藉PEO、LiTFSI、LLZTO與SN組成之複合式聚合物電解質，作為LAGP之界面修飾材料，以開發高性能之固態電池。

關鍵字

LAGP固態電解質 ； 鋰金屬電池 ； 混合離子界面層 ； 界面修飾

並列摘要

The primary objective of countries worldwide in response to the issue of climate change caused by global warming is to prioritize energy conservation and carbon reduction. Within the realm of energy conservation, improving energy storage efficiency stands as a top priority, with lithium-ion batteries serving as the primary energy storage systems. However, the flammability of traditional liquid electrolytes poses a significant safety hazard. Consequently, the focus of battery research has shifted towards developing inorganic solid-state electrolytes with flame retardancy and high energy density.
The first section of this study aims to investigate the interface failure between the sodium super-ionic conductor (NASICON) solid-state electrolyte, Li1.5Al0.5Ge1.5(PO4)3 (LAGP), and lithium metal. Through the assembly and analysis of a Li|LAGP|LiFePO4 battery using X-ray diffraction, the cause of the disappearance of the (012) crystal plane will be determined. Various spectroscopic techniques, including FT-IR, Raman, and XPS, will be utilized to confirm the corrosion process of LAGP. The formation of a mixed conductive interface layer will be confirmed using TOF-SIMS and AFM. Additionally, a symmetrical battery test will reveal that both ion and electron transport play equally critical roles in the electrochemical corrosion reaction of LAGP.
In the second section of the study, a composite polymer electrolyte (CPE) will be used as the interface layer between LAGP and lithium metal to prevent interface failure caused by direct contact. The composite polymer electrolyte will be prepared by incorporating Li6.4La3Zr1.4Ta0.6O12 (LLZTO) powder and succinonitrile (SN) into a PEO-based polymer electrolyte as the interface modifier layer. The introduction of various fillers will promote the excellent electrochemical performance of the polymer electrolyte, resulting in a ten-fold increase in lithium-ion conductivity. The electrolyte will be utilized as the interface modifier layer of LAGP and will maintain stability for 300 hours and a low overpotential of 75 mV in the electrochemical test of a Li|CPE|LAGP|CPE|Li symmetrical battery. Furthermore, the discharge capacity of the Li|CPE|LAGP|LiFePO4 full battery test will reach 136 mAh/g, with a discharge capacity retention rate of 90% after 75 cycles.
The novelty of this study lies in the thorough exploration of the actual principles underlying the failure reaction documented in existing literature, and the revelation of the failure mechanism from an alternative perspective using various instruments. Moreover, a composite polymer electrolyte composed of PEO, LiTFSI, LLZTO, and SN will be developed as the interface modifier material of LAGP to produce high-performance solid-state batteries.

並列關鍵字

LAGP solid-state electrolyte ； Li-metal battery ； mixed-conductive interphase ； interface modification

參考文獻

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