<br>含 LiBOB、LiDFOB 和 LiBF4 的 PEO 电解质中的初始 SEI 形成,Journal of Materials Chemistry A

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含 LiBOB、LiDFOB 和 LiBF4 的 PEO 电解质中的初始 SEI 形成
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2024-03-19 , DOI: 10.1039/d3ta07175h
Edvin K. W. Andersson, Liang-Ting Wu, Luca Bertoli, Yi-Chen Weng, Daniel Friesen, Kenza Elbouazzaoui, Sophia Bloch, Ruslan Ovsyannikov, Erika Giangrisostomi, Daniel Brandell, Jonas Mindemark, Jyh-Chiang Jiang, Maria Hahlin

基于固体聚合物电解质（SPE）的锂电池的一个限制因素是在锂金属阳极自发形成的电解质分解层的功能。对这一层有更深入的了解，将有利于其改进。本研究研究了三种 SPE：聚环氧乙烷：四氟硼酸锂 (PEO:LiBF ₄ )、聚环氧乙烷：二草酸硼酸锂 (PEO:LiBOB) 和聚环氧乙烷：二氟草酸硼酸锂 (PEO:LiDFOB)。电化学阻抗谱 (EIS)、恒电流循环、原位锂沉积光电子能谱 (PES) 和从头算分子动力学 (AIMD) 模拟的组合。通过这种组合，PEO:LiDFOB 的电池性能可以与阳极界面处的初始 SPE 分解联系起来。研究发现，PEO:LiDFOB 具有最高的容量保持率，这与界面处的分解最少有关。这表明界面处较低的 SPE 分解仍然会产生更有效的分解层，能够防止电解质进一步分解。此外，PES 结果表明，在基于 PEO 电解质的电池中，SEI 中形成了聚乙烯。 AIMD 证实了这一点，AIMD 显示了通过乙烯自由基聚合形成聚乙烯的途径。

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Initial SEI formation in LiBOB-, LiDFOB- and LiBF4-containing PEO electrolytes

A limiting factor for solid polymer electrolyte (SPE)-based Li-batteries is the functionality of the electrolyte decomposition layer that is spontaneously formed at the Li metal anode. A deeper understanding of this layer will facilitate its improvement. This study investigates three SPEs – polyethylene oxide:lithium tetrafluoroborate (PEO:LiBF₄), polyethylene oxide:lithium bis(oxalate)borate (PEO:LiBOB), and polyethylene oxide:lithium difluoro(oxalato)borate (PEO:LiDFOB) – using a combination of electrochemical impedance spectroscopy (EIS), galvanostatic cycling, in situ Li deposition photoelectron spectroscopy (PES), and ab initio molecular dynamics (AIMD) simulations. Through this combination, the cell performance of PEO:LiDFOB can be connected to the initial SPE decomposition at the anode interface. It is found that PEO:LiDFOB had the highest capacity retention, which is correlated to having the least decomposition at the interface. This indicates that the lower SPE decomposition at the interface still creates a more effective decomposition layer, which is capable of preventing further electrolyte decomposition. Moreover, the PES results indicate formation of polyethylene in the SEI in cells based on PEO electrolytes. This is supported by AIMD that shows a polyethylene formation pathway through free-radical polymerization of ethylene.

更新日期：2024-03-19

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