Effect of the Addition of Bivalent Ions on Electrochemical Lithium-Ion Intercalation at Graphite Electrodes

Abstract

Electrochemical lithium-ion intercalation/de-intercalation at a graphite electrode were studied in propylene carbonate-based electrolyte solutions containing both lithium bis(trifluoromethanesulfonyl)amide and magnesium bis(trifluoromethanesulfonyl)amide salts by using lithium/graphite cell, and the influence of the salt concentration was investigated. In the higher concentration electrolyte solutions, reversible lithium-ion intercalation/de-intercalation at the graphite electrodes occurred. In contrast, only the exfoliation of graphite occurred in the lower concentration electrolyte solutions. The threshold ratio of the magnesium salt (Mg2+/Li+ = 0.9) was lower than that of the calcium salt (Ca2+/Li+ = 1.1).