Physik-Department ECS , Technische Universität München , James-Franck-Straße 1 , 85748 Garching , Germany.
Nanosystems Initiative Munich (NIM) , Schellingstraße 4 , 80799 Munich , Germany.
ACS Appl Mater Interfaces. 2018 Apr 25;10(16):14063-14069. doi: 10.1021/acsami.7b18738. Epub 2018 Apr 12.
A so-called solid electrolyte interface (SEI) in a lithium-ion battery largely determines the performance of the whole system. However, it is one of the least understood objects in these types of batteries. SEIs are formed during the initial charge-discharge cycles, prevent the organic electrolytes from further decomposition, and at the same time govern lithium intercalation into the graphite anodes. In this work, we use electrochemical impedance spectroscopy and atomic force microscopy to investigate the properties of a SEI film and an electrified "graphite/SEI/electrolyte interface". We reveal a multistage mechanism of lithium intercalation and de-intercalation in the case of graphite anodes covered by SEI. On the basis of this mechanism, we propose a relatively simple model, which perfectly explains the impedance response of the "graphite/SEI/electrolyte" interface at different temperatures and states of charge. From the whole data obtained in this work, it is suggested that not only Li but also negatively charged species, such as anions from the electrolyte or functional groups of the SEI, likely interact with the surface of the graphite anode.
在锂离子电池中，所谓的固体电解质界面（SEI）在很大程度上决定了整个电池系统的性能。然而，它是这类电池中了解最少的对象之一。SEI 在初始充放电循环期间形成，防止有机电解质进一步分解，同时控制锂离子嵌入石墨阳极。在这项工作中，我们使用电化学阻抗谱和原子力显微镜来研究 SEI 膜和带电的“石墨/SEI/电解质界面”的性质。我们揭示了在 SEI 覆盖的石墨阳极的情况下，锂离子嵌入和脱嵌的多阶段机制。基于该机制，我们提出了一个相对简单的模型，该模型完美地解释了“石墨/SEI/电解质”界面在不同温度和荷电状态下的阻抗响应。从这项工作中获得的全部数据表明，不仅锂离子，而且带负电荷的物质，例如电解质中的阴离子或 SEI 的官能团，可能与石墨阳极的表面相互作用。
