Atomic to Nanoscale Origin of Vinylene Carbonate Enhanced Cycling Stability of Lithium Metal Anode Revealed by Cryo-TEM.
Atomic to Nanoscale Origin of Vinylene Carbonate Enhanced Cycling Stability of Lithium Metal Anode Revealed by Cryo-TEM.
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DOI：
10.1021/acs.nanolett.9b04111
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发表时间：
2019-12
期刊：
影响因子：
10.8
通讯作者：
Yaobin Xu;Haiping Wu;Yang He;Qingsong Chen;Ji‐Guang Zhang;Wu Xu;Chongmin Wang
中科院分区：
文献类型：
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作者：
Yaobin Xu;Haiping Wu;Yang He;Qingsong Chen;Ji‐Guang Zhang;Wu Xu;Chongmin Wang
使用锂（Li）金属作为阳极的电池由于其高比能量密度而被认为是有前途的储能系统。锂金属负极的关键瓶颈是锂枝晶的生长和与电解质的副反应，导致安全问题、库仑效率（CE）低和循环寿命短。碳酸亚乙烯酯（VC）作为锂离子电池中有效的电解质添加剂，已被注意到可以显着提高CE，但这种添加剂的来源仍不清楚。这里我们利用低温透射电子显微镜成像结合能量色散X射线能谱元素和电子能量损失能谱电子结构分析来揭示VC添加剂的作用。我们发现含 VC 电解液中电化学沉积的锂金属 (EDLi) 被轻微氧化，SEI 是由有机物质、Li2O 和 Li2CO3 组成的纳米级马赛克状结构；而在不含VC的电解质中形成的EDLi的特点是完全氧化的Li与Li2O SEI层和纯Li金属与多层纳米结构SEI的结合。这些结果强调了通过添加剂可以调整 EDLi 和 SEI 的关键结构和化学特征，从而与电化学性能直接相关，为合理选择、设计和合成新型电池化学添加剂提供了宝贵的指导。
Batteries using lithium (Li) metal as anode are considered promising energy storage systems because of their high specific energy densities. The crucial bottlenecks for Li-metal anode are Li dendrites growth and side reactions with electrolyte inducing safety concern, low Coulombic efficiency (CE) and short cycle life. Vinylene carbonate (VC), as an effective electrolyte additive in Li-ion batteries, has been noticed to significantly enhance the CE, while the origin of such an additive remains unclear. Here we use cryogenic transmission electron microscopy imaging combing with energy dispersive X-ray spectroscopy elemental and electron energy loss spectroscopy electronic structure analyses to reveal the role of VC additive. We discovered that the electrochemically deposited Li metal (EDLi) in VC-containing electrolyte is slightly oxidized with the SEI being a nanoscale-mosaic like structure comprised of organic species, Li2O and Li2CO3; while the EDLi formed in VC-free electrolyte is featured by a combination of fully oxidized Li with Li2O SEI layer and pure Li metal with multilayer nano-structured SEI. These results highlight the possible tuning of crucial structural and chemical features of EDLi and SEI through additives and consequently direct correlation with electrochemical performance, providing valuable guidelines to rational selection, design and synthesis of additives for new battery chemistries.