In Situ Potentiodynamic Analysis of the Electrolyte/Silicon Electrodes Interface Reactions - A Sum Frequency Generation Vibrational Spectroscopy Study
In Situ Potentiodynamic Analysis of the Electrolyte/Silicon Electrodes Interface Reactions - A Sum Frequency Generation Vibrational Spectroscopy Study
复制标题
DOI：
10.1021/jacs.5b10333
复制
发表时间：
2016-01-27
影响因子：
15
通讯作者：
Somorjai, Gabor A.
中科院分区：
文献类型：
--
作者：
Horowitz, Yonatan;Han, Hui-Ling;Somorjai, Gabor A.
电池长期使用的关键因素是形成电绝缘固体层，该固体层允许锂离子传输，但阻止电极表面上进一步的电解质氧化还原反应，从而形成固体电解质界面（SEI）。我们研究了一种常见电解质，即 1.0 M LiPF6/碳酸乙烯酯 (EC)/碳酸二乙酯 (DEC)，以及在反应条件下锂 (Li) 半电池系统中晶体硅 (Si) 电极上的还原产物。我们采用具有界面敏感性的原位和频发生振动光谱 (SFG-VS)，以探测在预期电解质还原的各种施加电位下 SEI 表面物质的分子组成。我们发现，对于 Si(100) 氢封端晶圆，由于 DEC 分解，会形成 Si-乙氧基 (Si-OC2H5) 表面中间体。我们的结果表明，SEI 表面成分的变化取决于 Si 表面的终止，即 Si 表面的酸度。我们提供了反应条件下阳极表面 SEI 的特定化学成分的证据。这支持了电化学电解质还原机制，其中 DEC 分子还原为乙氧基部分起着关键作用。这些发现为特别是硅阳极上 SEI 的形成机制以及一般 SEI 的形成提供了新的线索。
The key factor in long-term use of batteries is the formation of an electrically insulating solid layer that allows lithium ion transport but stops further electrolyte redox reactions on the electrode surface, hence solid electrolyte interphase (SEI). We have studied a common electrolyte, 1.0 M LiPF6/ethylene carbonate (EC)/diethyl carbonate (DEC), reduction products on crystalline silicon (Si) electrodes in a lithium (Li) half-cell system under reaction conditions. We employed in situ sum frequency generation vibrational spectroscopy (SFG-VS) with interface sensitivity in order to probe the molecular composition of the SEI surface species under various applied potentials where electrolyte reduction is expected. We found that, with a Si(100)-hydrogen terminated wafer, a Si-ethoxy (Si-OC2H5) surface intermediate forms due to DEC decomposition. Our results suggest that the SEI surface composition varies depending on the termination of Si surface, i.e., the acidity of the Si surface. We provide the evidence of specific chemical composition of the SEI on the anode surface under reaction conditions. This supports an electrochemical electrolyte reduction mechanism in which the reduction of the DEC molecule to an ethoxy moiety plays a key role. These findings shed new light on the formation mechanism of SEI on Si anodes in particular and on SEI formation in general.