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Stable cycling of small molecular organic electrode materials enabled by high concentration electrolytes
Energy Storage Materials ( IF 18.9 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.ensm.2020.06.032
Taotao Cai , Yan Han , Qing Lan , Feng Wang , Jun Chu , Hui Zhan , Zhiping Song

Small molecular organic electrode materials (SMOEMs) enjoy favorable high capacity and low cost, but suffer from poor cycling stability and low Coulombic efficiency due to the unavoidable dissolution in aprotic electrolytes. Previous studies of the dissolution inhibition strategy mainly focused on the molecular designing or electrode engineering, but neglected the important or crucial influence of the electrolyte. Herein, a facial “high concentration electrolyte” strategy is employed to study two typical dianhydride molecules, namely 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), achieving dramatically improved cycling stability for both. Remarkably, in 3 M LiTFSI/DOL + DME electrolyte (lithium bis(trifluoromethanesulphonyl)imide/1,3-dioxolane + 1,2-dimethoxyethane), PTCDA shows a high capacity retention of 87% (relative to the maximum capacity of 147 mAh g−1) after 1000 cycles at a current rate of 100 mA g−1, along with an exceptional average Coulombic efficiency of 99.99%, setting one of the best cycling performance records for SMOEMs. The comparative study of NTCDA and PTCDA in LiTFSI/DOL + DME electrolytes with different concentrations (1, 2, 3, and 4 M) indicates that both intrinsic crystalline structure stability of the active material and appropriate electrolyte are key origins of good cycling stability. According to ex-situ characterization results, a “dissolution–redeposition” mechanism of SMOEMs is proposed to update researchers’ obscure understanding of the dissolution behavior. We believe this work provides not only confidence on the performance potential but also insightful mechanism understanding of SMOEMs, which are important for their further development towards practical application.



中文翻译:

高浓度电解质可实现小分子有机电极材料的稳定循环

小分子有机电极材料(SMOEM)具有良好的高容量和低成本,但由于不可避免地溶解在非质子电解质中,因此循环稳定性差,库伦效率低。先前关于溶解抑制策略的研究主要集中在分子设计或电极工程上,但是忽略了电解质的重要或关键影响。在本文中,采用面部“高浓度电解质”策略来研究两种典型的二酐分子,即1,4,5,8-萘四甲酸二酐(NTCDA)和3,4,9,10-per四羧酸二酐(PTCDA),改善了两者的循环稳定性。值得注意的是,在3 M LiTFSI / DOL + DME电解质中(双(三氟甲磺酰基)酰亚胺/ 1,3-二氧戊环+ 1,2-二甲氧基乙烷),-1)之后以100 mA g -1的电流速率循环1000次,平均库仑效率高达99.99%,为SMOEM创造了最佳自行车性能记录之一。在不同浓度(1、2、3和4 M)的LiTFSI / DOL + DME电解质中NTCDA和PTCDA的比较研究表明,活性材料的固有晶体结构稳定性和适当的电解质都是良好循环稳定性的关键来源。根据异位表征结果,提出了SMOEM的“溶解-再沉积”机制,以更新研究人员对溶解行为的模糊理解。我们相信这项工作不仅使人们对SMOEM的性能潜力充满信心,而且对SMOEM有了深刻的机制理解,这对于它们向实际应用的进一步发展很重要。

更新日期:2020-07-01
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