高濃度電解質於鋰電池知應用研究;High Concentration Electrolytes for Lithium Batteries

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Title:	高濃度電解質於鋰電池知應用研究;High Concentration Electrolytes for Lithium Batteries
Authors:	劉翁境;LIU, WENG-JING
Contributors:	材料科學與工程研究所
Keywords:	高濃度;鋰電池;High Concentration Electrolyte
Date:	2017-08-15
Issue Date:	2017-10-27 13:17:45 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文中利用高濃度醚類電解液、高濃度碳酸類電解液，分別應用於石墨負極和鋰金屬負極，提高電容量、庫倫效率。第一部分為高濃度醚類電解液應用於鋰金屬負極，同時比較一系列鏈狀、環狀醚類，發現有別於傳統商用電解液低庫倫效率的問題，高濃度醚類電解液有約 97%的庫倫效率，同時抑制鋰金屬枝晶狀結構的產生。第二部分為高濃度碳酸類電解液應用於鋰金屬負極，其庫倫效率有約 96%，相較於文獻上傳統碳酸類電解液小於 90%的低庫倫效率，有效提高約 15%以上的庫倫效率，其重點在不同於以往碳酸類溶劑溶液容易生長出鋰金屬枝晶狀結構，高濃度碳酸類電解液呈現非常不同的形貌。第三部分為高濃度碳酸類電解液應用於石墨負極，在石墨負極上有相較以往商用電解液較高的電容量，改善了特別是在高速充放電時傳統電解液在石墨中具有較低的電容量的問題，而利用高濃度電解液也展現在不添加 EC 的情況下，能有效在石墨負極中具有循環可逆的電容值，而不破壞石墨的結構。結果顯示高濃度電解液能有效提高鋰金屬負極、石墨負極的電化 II 學性能，並抑制負面的影響，顯示高濃度電解液為一有效並容易達到的方法。;In this study, high concentration ether and carbonate electrolytes were used in graphite and lithium metal anode to enhance the electrochemical properties in terms of coulombic efficiency, capacity, and high-rate. The first part of this study explores high concentration ether electrolyte used for lithium metal anode. On comparing a series of different ether based electrolytes with 1M and 3M concentration, 3M ether based electrolyte was found to offer exceptional properties than traditional electrolytes. 3M ether based electrolytes solved the major problems faced for Li metal anode (coulombic efficiency and dendrite formation). A very high coulombic efficiency of ~97 % can be achieved using 3M. The second part of this study of high concentration carbonate electrolyte (1M, 3M, and 5.5M) for lithium metal anode. The coulombic efficiency of about ~96% was obtained for the 5.5M electrolyte which was found to be quite high compared to the literature on the traditional carbonate electrolyte (less than 80%). In addition, the dendrite formation is completely inhibited to a larger extent by using high concentration (5.5 M) carbonate electrolytes. The final part of the study involves high concentration carbonate electrolyte (5.5M) used for graphite anode. The 5.5M electrolytes found to offer high charge/discharge properties than the commercial electrolyte. The exceptional properties are obtained even without the addition of EC, which is a prerequisite for traditional electrolytes. Higher reversible performance is obtained for 5.5M carbonate without destroying the graphitic structure. The results show that high concentration electrolytes can effectively improve the electrochemical performance of lithium metal anode and graphite anode by offering high coulombic efficiency and inhibiting the dendrite formation (in Li metal anode). This study demonstrates the higher performance can be obtained by optimizing the electrolyte concentration.
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