Electrochemical lithium ion intercalation into graphite electrode in propylene carbonate-based electrolytes with dimethyl carbonate and calcium salt

摘要

Electrochemical intercalation of Li~+ ions into graphite electrodes in propylene carbonate (PC)-dimethyl carbonate (DMC)-based electrolytes containing Ca~(2+) ions was studied. The molar ratio of PC, Li~+ ion, and Ca~(2+) ion was PC:Li~+:Ca~(2+) = 12:1.0:0.5. Intercalation of Li~+ ions became possible by adding DMC to the PC-based electrolytes containing Ca~(2+) ions: Li~+ ion intercalation did not take place when the amount of DMC was DMC/PC = 6 (molar ratio) and below, and Li~+ ions intercalated when the amount of DMC was above DMC/PC = 8. Intercalation of Li~+ ions did not take place in PC-DMC-based electrolyte of no Ca~(2+) ions, and both Ca~(2+) ion and DMC were necessary for Li~+ ion intercalation. Successful Li~+ ion intercalation can be attributed to smaller solvation number of PC on Li~+ ions by addition of DMC and Ca~(2+) ions to the PC-based electrolyte.