Interface reactivity of in-situ formed LiCoO2 - PEO solid-state interfaces investigated by X-ray photoelectron spectroscopy: Reaction products, energy level offsets and double layer formation
Interface reactivity of in-situ formed LiCoO2 - PEO solid-state interfaces investigated by X-ray photoelectron spectroscopy: Reaction products, energy level offsets and double layer formation
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DOI：
10.1016/j.apsusc.2021.151218
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发表时间：
2021-09-21
影响因子：
6.7
通讯作者：
Hausbrand, Rene
中科院分区：
文献类型：
--
作者：
Ferber, Thimo H.;Cangaz, Sahin;Hausbrand, Rene
涉及陶瓷固体电解质的界面仍然是所有固态电池的最大挑战，因为它们的刚性和脆性导致高界面电阻。解决这一问题的一种方法是制备具有更好机械性能和润湿性能的固体聚合物电解质（SPE）。常用的聚合物电解质是具有LiTFSI的PEO，其达到足够的离子电导率，但在高压阴极上遭受副反应。为了使用PEO，有必要了解发生的潜在反应过程，例如，在LiCoO 2电极上。在这方面的贡献，我们的表面科学的方法来调查电池接口转移到PEO使用低聚物聚（乙二醇）与LiTFSI沉积通过热蒸发，研究界面形成对LiCoO 2。蒸发过程中PEG和LiTFSI的稳定性用XPS和质谱法显示。在超高真空条件下研究了LiCoO 2/PEG和LiCoO 2/PEG与LiTFSI的界面。形成反应层，其限于LiCoO 2的上表面。此外，已观察到电子和Li+-离子从LiCoO 2转移到反应相中。用SEM观察了界面的润湿行为。绘制了两个界面的能级图，解释了接触形成的性质。
Interfaces involving ceramic solid electrolytes remain the biggest challenge for all solid-state batteries due to their rigid and brittle nature resulting in high interface resistances. A solution for this problem are solid polymer electrolytes (SPE) with better mechanical and wetting-behavior. A commonly used polymer electrolyte is PEO with LiTFSI, which reaches sufficient ionic conductivity but suffers from side reactions on high voltage cathodes. To use PEO, it is necessary to understand the underlying reaction processes that occur e.g., at the LiCoO2 electrode. In this contribution, our surface science approach to investigate battery interfaces is transferred to PEO using the oligomer poly (ethylene glycol) with LiTFSI deposited by thermal evaporation to study the interface formation towards LiCoO2. The stability of PEG and LiTFSI during evaporation is shown with XPS and mass spectroscopy. The interfaces of LiCoO2/PEG and LiCoO2/PEG with LiTFSI are studied under UHV condition on sputtered LiCoO2 thin films. A reaction layer is formed that is limited to the upper surface of LiCoO2. Additionally, electron and Li+-ion transfer from the LiCoO2 into the reaction phase has been observed. The wetting-behavior of the interfaces are investigated with SEM. Energy level diagrams for both interfaces are drawn, explaining the contact formation properties.