Yamada Yuki, Usui Kenji, Chiang Ching Hua, Kikuchi Keisuke, Furukawa Keizo, Yamada Atsuo
Department of Chemical System Engineering, The University of Tokyo , Tokyo 113-8656, Japan.
ACS Appl Mater Interfaces. 2014 Jul 23;6(14):10892-9. doi: 10.1021/am5001163. Epub 2014 Mar 26.
Lithium-ion batteries have exclusively employed an ethylene carbonate (EC)-based electrolyte to ensure the reversibility of the graphite negative electrode reaction. Because of the limitation of electrolyte compositions, there has been no remarkable progress in commercial lithium-ion batteries despite active research on positive electrode materials. Herein, we present a salt-superconcentrating strategy as a simple and effective method of universalizing a graphite negative electrode reaction in various organic solvents. A dilute electrolyte (e.g., 1 mol dm(-3)) of sulfoxide, ether, and sulfone results in solvent cointercalation and/or severe electrolyte decomposition at a graphite electrode, whereas their superconcentrated electrolyte (e.g., >3 mol dm(-3)) allows for highly reversible lithium intercalation into graphite. We have found a unique coordination structure in the superconcentrated solution and an anion-based inorganic SEI film on the cycled graphite electrode, which would be the origin of the reversible graphite negative electrode reaction without EC. Our salt-superconcentrating strategy, expanding the graphite negative electrode reaction in various organic solvents other than EC, will contribute to the development of advanced lithium-ion batteries with high-voltage and fast-charging characters based on new EC-free functional electrolytes.
锂离子电池一直专门采用基于碳酸亚乙酯（EC）的电解质，以确保石墨负极反应的可逆性。由于电解质成分的限制，尽管对正极材料进行了积极研究，但商用锂离子电池仍未取得显著进展。在此，我们提出一种盐超浓缩策略，作为一种在各种有机溶剂中使石墨负极反应通用化的简单有效方法。亚砜、醚和砜的稀电解质（例如1 mol dm⁻³）会导致在石墨电极处发生溶剂共嵌入和/或严重的电解质分解，而它们的超浓缩电解质（例如>3 mol dm⁻³）则允许锂高度可逆地嵌入石墨中。我们在超浓缩溶液中发现了一种独特的配位结构，并在循环后的石墨电极上发现了一种基于阴离子的无机固体电解质界面（SEI）膜，这可能是无EC时可逆石墨负极反应的起源。我们的盐超浓缩策略扩展了除EC之外的各种有机溶剂中的石墨负极反应，将有助于基于新型无EC功能电解质开发具有高电压和快速充电特性的先进锂离子电池。
