Ionic liquids(ILs)have very wide perspective industrial applications.Understanding their structural and dynamic properties is essential for the systematic design of ILs to meet specific application requests.ILs with intermediate nonpolar cationic side-chain lengths are known to have nanoscale spatial heterogeneities with nonpolar tail domains separated by a continuous polar network.Based on this knowledge,our most recent molecular dynamics simulations have the following discoveries: 1)the intrinsic electric field in ILs is only slightly stronger than molecular solvents and much weaker than molten salts; 2)driven by an external electric field,the ion cage structure of ILs was found to play an essential role in determining the structural and dynamic properties of the IL system,and a systematic mechanism based on the ion cage concept was proposed to explain the structural and dynamic changes of ILs with electric field; 3)when the nonpolar cationic side chain is sufficiently long,due to the stronger van der Waals interactions between the side chains,the structure of ionic liquids goes through a transition from spatially heterogeneous to liquid crystalline-like; 4)ILs with polar cationic tails form a rich number of hydrogen bonds with other groups,indicating that the hydroxyl substituent changes the IL system from an amphiphilic liquid to a polar liquid.