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| 題名: | 電解質的濃度效應與複合式材料的製備應用於鋰離子電池之矽負極;Development of Silicon based Anode for Lithium-Ion Batteries: Effect of Salt Concentration in Electrolytes, and Composite Materials Preparation |
| 作者: | 芭瑞斯;Umesh, Bharath |
| 貢獻者: | 材料科學與工程研究所 |
| 關鍵詞: | 鋰離子電池;矽陽極;電解質;Li-ion batteries;Silicon anode;Electrolytes |
| 日期: | 2022-01-24 |
| 上傳時間: | 2022-07-13 18:31:55 (UTC+8) |
| 出版者: | 國立中央大學 |
| 摘要: | 鋰離子電池 (LIBs) 為目前儲能技術的主流。在商用鋰電池中的石墨負極因具有層狀結構，使鋰離子能在充放電過程中藉由電解質的傳輸進入石墨層中進行反應。基於鋰離子電池的技術成熟，目前已經能擴展到電動汽車市場和大規模電網系統中。因此，需要更高能量密度的電池。為了達到這項需求，替換正極和負極中活性物質是必要的。電解質也將承受較大的電位差，在低電位和高電位下都會進行分解，形成一鈍化層，稱之為固態電解質介面層 (SEI)。
在此，我們研究了電解質的濃度效應，發現雙（氟磺酰基）亞胺鋰（LiFSI）濃度對於碳酸亞乙酯（EC）/碳酸二乙酯（DEC）電解質中矽負極的電容量、高速性能和循環穩定性與氟代碳酸亞乙酯 (FEC)電解質中得到相反的結果。透過拉曼光譜、穿透式電子顯微鏡、電化學阻抗光譜和恆電流間歇滴定技術對該結果進行了系統性的分析。同時，透過X 射線光電子能譜分析對固液界面化學進行了詳細的研究。發現當電解質中有適合的 LiFSI 濃度時，在EC/DE電解質中發生的鋁腐蝕現象在FEC電解質中可以被有效地抑制。
在第二項研究中，將使用高電導率、良好的高維穩定性的複合式負極（Si/CNT/G）作為鋰離子電池的高能量密度負極材料，電解質為由醚側鏈吡咯烷鎓、不對稱酰亞胺和高 Li+ 濃度組成的離子液體（IL）。這種電解液首次使用於矽基鋰離子電池。醚基的分解會產生有機成分形成SEI。而高濃度的 Li+ 會促進（氟磺酰基）（三氟甲磺酰基）酰亞胺 (FTFSI-) 陰離子的分解，產生富含 LiF- 和 Li3N 的 SEI層。具備有機-無機平衡的 SEI 層是 Si/CNT/G 負極有優異充放電性能的原因。 FTFSI− 陰離子對鋁基板有較低的腐蝕性，並與 LiNi0.8Co0.1Mn0.1O2 (NCM-811) 正極具有高相容性。在 4.5 V 的高電壓下， NCM-811 在高 Li+ 轉移數 N-甲氧基乙基-N-甲基吡咯烷鎓/FTFSI IL 電解質中具有良好的可逆電容量和循環穩定性。差示掃描量熱法用於檢測脫鋰 NCM-811 與各種電解質之間的界面放熱反應。
為了克服矽負極中機械劣化和低鋰擴散速率的問題，我們製備出一種透過一氧化氮下熱處理的富矽氮化矽 (Si/SiN)。Si/SiN 奈米顆粒可透過Si3N4以及在充放電過程中於原位形成的 Li3N來提高機械穩定性與離子導電率進而改善矽負極的電化學性能。Si/SiN奈米顆粒成功地表現出優異的電化學性能，包括良好的循環穩定性和高速維持率。
;Lithium-ion batteries (LIBs) are currently the dominant energy storage technology, current commercial lithium ion battery utilizes graphite anode which have intercalation of lithium between the layered structure. The lithium ions are transported through the electrolyte during the charge/discharge process. LIBs have now made inroads into the electric vehicle sector and large-scale grid storage, both of which require batteries with significantly higher energy densities due to their success. Alternative anode and cathode chemistries are required to meet this demand. As a result, the electrolyte will be under a lot of strain, and it will decompose at both low and high potentials to form a passivation layer known as the solid electrolyte interphase (SEI).
Here, in this work we investigate moderately concentrated electrolytes and find that the effects of lithium bis(fluorosulfonyl)imide (LiFSI) concentration on the capacity, rate capability, and cycling stability of Si anodes in an ethylene carbonate (EC)/diethyl carbonate (DEC) mixed electrolyte are found to be opposite to those in a fluoroethylene carbonate (FEC) electrolyte in this study. The reasons for these observations are investigated using Raman spectroscopy, transmission electron microscopy, electrochemical impedance spectroscopy, and the galvanostatic intermittent titration technique. The solid electrolyte interphase chemistry is investigated in detail using an X-ray photoelectron spectroscopy investigation. Al corrosion that occurs with EC/DEC-based electrolytes can be efficiently reduced with FEC-based electrolytes if an acceptable LiFSI concentration is used.
The compatibility of a prepared ionic liquid (IL) electrolyte containing ether-side-chain pyrrolidinium, asymmetric imide, and a high Li+ fraction with a high conductivity, high dimensional stability composite anode (denoted as Si/CNT/G) as a high energy density anode material for LIBs is studied in the second study of this thesis. This is the first time this electrolyte has been used in Si-based Li-ion batteries. Organic components are formed when the ether groups decompose to form a solid electrolyte interphase (SEI). Because of the high Li+ concentration, the (fluorosulfonyl)(trifluoromethanesulfonyl)imide (FTFSI−) anions decompose, resulting in a LiF and Li3N-rich SEI. The Si/CNT/G anode′s exceptional charge-discharge characteristics are due to the organic-inorganic balanced SEI. The FTFSI− anions are non-corrosive to the Al current collector and have a high compatibility with the LiNi0.8Co0.1Mn0.1O2 (NCM-811) cathode. NCM-811 in the high-Li+-fraction N-methoxyethyl-N-methylpyrrolidinium/FTFSI IL electrolyte exhibits remarkable reversible capacity and cycle stability when charged upto 4.5 V. The interfacial exothermic interactions between the delithiated NCM-811 and various electrolytes are investigated using differential scanning calorimetry.
In the third section of this thesis, we describe a Si-rich silicon nitride (Si-SiNx) synthesized via heat treatment under gaseous nitric oxide (NO) to alleviate the main inherent difficulties of Si anodes, such as mechanical deterioration and slow Li+ diffusion. During charge/discharge, the produced Si-SiNx nanoparticles successfully change the inherent electrochemical properties of the Si anode by enhancing mechanical stability and ionic conductivity with Si3N4 and in-situ generated Li3N. Si-SiNx nanoparticles have shown enhanced battery performance, including high rate capability and cycling stability. |
| 顯示於類別: | [材料科學與工程研究所 ] 博碩士論文
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