title: General observation of lithium intercalation into graphite in ethylene-carbonate-free superconcentrated electrolytes.
abstract: 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.
authors.affiliation: Department of Chemical System Engineering, The University of Tokyo , Tokyo 113-8656, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yamada
authors.forename: Kenji
authors.initials: K
authors.lastname: Usui
authors.forename: Ching Hua
authors.initials: CH
authors.lastname: Chiang
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kikuchi
authors.forename: Keizo
authors.initials: K
authors.lastname: Furukawa
authors.forename: Atsuo
authors.initials: A
authors.lastname: Yamada