Forming an effective solid electrolyte interphase (SEI) is a significant issue in lithium ion batteries that utilize graphite as a negative electrode material, because the SEI determines the reversibility of the intercalation and de-intercalation of lithium ions into graphite for secondary batteries. In propylene carbonate (PC)-based electrolyte solutions, ceaseless co-intercalation of solvated lithium ions takes place because no effective SEI is formed. It is indisputable that this continuous co-intercalation leads to graphite exfoliation; however, the reason for this is currently not well understood. In this study, we investigate interfacial reactions that contribute to SEI formation on highly oriented pyrolytic graphite (HOPG) in ethylene carbonate (EC) and PC-based electrolyte solutions by in situ atomic force microscopy. The blisters formed on HOPG after the decomposition of solvated lithium ions within the graphite layers do not change over the course of ten electrochemical cycles in an EC-based electrolyte solution. In contrast, when cycling in PC-based electrolytes, the blisters continually change, and the height at the vicinity of the graphite edge plane increases. These morphological changes are attributed to the continuous co-intercalation of solvated lithium ions in PC-based electrolyte solutions.

在利用石墨作为负极材料的锂离子电池中，形成有效的固体电解质中间相（SEI）是一个重要的问题，因为SEI决定了锂离子嵌入和脱嵌到用于二次电池的石墨中的可逆性。在碳酸亚丙酯（PC）基电解质溶液中，由于没有形成有效的SEI，所以发生了溶剂化锂离子的不间断共嵌入。毫无疑问，这种连续的共嵌入会导致石墨剥落。但是，目前尚不清楚其原因。在这项研究中，我们通过原位原子力显微镜研究了界面反应，这些反应有助于在碳酸亚乙酯（EC）和基于PC的电解质溶液中的高取向热解石墨（HOPG）上形成SEI。石墨层中的溶剂化锂离子分解后，在HOPG上形成的气泡在基于EC的电解质溶液中经过十个电化学循环后不会发生变化。相反，当在基于PC的电解质中循环时，气泡不断变化，并且石墨边缘平面附近的高度增加。这些形态变化归因于PC基电解质溶液中溶剂化锂离子的连续共嵌入。