Functional ionic liquids: Cationic SEI-formers for lithium batteries

Journal article, 2019

More stable electrolytes for lithium-ion batteries are urgently needed, and apart from general improvements in thermal and electrochemical stabilities, both stability, safety and performance are connected with the formation of the solid electrolyte interphase (SEI) layer at the negative electrode. A high performant SEI-layer; thin, uniform, highly ion conducting, etc., is difficult to achieve and proper control of its formation process is therefore highly desirable. The idea presented here is based on computational screening of a wide range of modifications of wellknown ionic liquid (IL) cations towards better ability to form SEI-layers - i.e. acting as SEI-formers. Different cation chemistries and kinds of structural modifications were tested, with introduction of nitrile groups and/or double bonds resulting to be the most promising. The latter is outlined as especially beneficial, as apart from enabling an easier initiation reaction it provides a site for polymerization, resulting in polymeric SEI-products poly (IL) s (PILs), which can be expected to provide both protection of the electrode surface and fast Li thorn transport.