Confining Ionic Liquids in Developing Quasi‐Solid‐State Electrolytes for Lithium Metal Batteries

The concept of confining ionic liquids (ILs) in developing quasi-solid-state electrolytes (QSSEs) has been proposed, where ILs are dispersed in polymer networks/backbones and/or filler/host pores, forming the so-called confinement, and great research progress and promising research results have been achieved. In this review, the progress and achievement in developing QSSEs using IL-confinement for lithium metal batteries (LMBs), together with advanced characterizations and simulations, were surveyed, summarized, and analyzed, where the influence of specific parameters, such as IL (type, content, etc.), substrate (type, structure, surface properties, etc.), confinement methods, and so on, was discussed. The confinement concept was further compared with the conventional one in other research areas. It indicates that the IL-confinement in QSSEs improves the performance of electrolytes, for example, increasing the ionic conductivity, widening the electrochemical window, and enhancing the cycle performance of the assembled cells, and being different from those in other areas, that is, the IL-confinement concept in the battery area is in a broad extent. Finally, insights into developing QSSEs in LMBs with the confinement strategy were provided to promote the development and application of QSSE LMBs.