LONG CHAIN 1-ALKYL-3-METHYLIMIDAZOLIUM TETRAFLUOROBORATES AS ELECTROLYTES IN Li-ION BATTERIES

We have determined the electrochemical behavior of a series of long chain 1-alkyl-3-methylimidazolium ionic liquids [(R-mim)BF4], with alkyl groups ranging from pentyl to octyl, and tested them as electrolytes in lithium ion batteries. These ionic liquids present good conductivities and electrochemical Windows which make them likely solvents of choice for Li-ion batteries using LiMn2O4 as the cathode. Charge/discharge properties of a Li/ R-mim)BF4/LiMn2O4 cell have been evaluated both with the IL as the sole electro lyte and with IL and conducting support. The Li- ion insertion results in IL can be explained on the basis of self aggregation of each long chain 1-alkyl-3-methylimidazolium cation.