Electrochemical Intercalation/De-Intercalation of Lithium Ions at Graphite Negative Electrode in TMP-Based Electrolyte Solution

A new approach for the non-flammable electrolytes of lithium-ion batteries is proposed. Effect of calcium salt addition on electrochemical behaviors of a graphite negative electrode in ethylene carbonate (EC)-based electrolyte containing 40 vol.% trimethyl phosphate (TMP) were studied. Co-intercalation of Li+ with TMP followed by exfoliation of graphite took place when the electrolyte does not contain calcium salt. On the contrary, reversible lithium-ion intercalation/de-intercalation behaviors were observed when the certain amount of calcium salt was added to the electrolyte. Correlation between calcium salt addition and lithium-ion intercalation behavior is discussed by considering the Lewis acidity of calcium- and lithium-ions and donor numbers of solvents.