A new ionic liquid was prepared by introducing a boronic acid group to an imidazolium cation with a hydrophobic anion. The boronic acid-containing ionic liquid showed the best ionic conductivity of 6.5 x 10(-4) S cm(-1) at 50 degrees C, with a high lithium ion transference number of over 0.5, owing to the anion-trapping effect of the boronic acid group.