Ionic liquids are composed of equal quantities of positive and negative ions. In the bulk, electrical neutrality occurs in these liquids due to Coulombic ordering, in which ion shells of alternating charge form around a central ion. Their structure under confinement is far less well understood. This hinders the widespread application of ionic liquids in technological applications. Here we use scattering experiments to resolve the structure of a widely used ionic liquid (EMI–TFSI) when it is confined inside nanoporous carbons. We show that Coulombic ordering reduces when the pores can accommodate only a single layer of ions. Instead, equally charged ion pairs are formed due to the induction of an electric potential of opposite sign in the carbon pore walls. This non-Coulombic ordering is further enhanced in the presence of an applied external electric potential. This finding opens the door for the design of better materials for electrochemical applications.

离子液体由等量的正离子和负离子组成。在大体积中，由于库仑排序，这些液体中会出现电中性，其中交替电荷的离子壳围绕中心离子形成。它们在限制条件下的结构远没有那么好理解。这阻碍了离子液体在技术应用中的广泛应用。在这里，我们使用散射实验来解析广泛使用的离子液体 (EMI-TFSI) 当它被限制在纳米多孔碳内时的结构。我们表明，当孔只能容纳单层离子时，库仑排序会降低。相反，由于在碳孔壁中感应出相反符号的电势，会形成带相同电荷的离子对。这种非库仑有序在存在外加电势的情况下得到进一步增强。这一发现为设计更好的电化学应用材料打开了大门。