Lithium Metal Protection by a Cross-Linked Polymer Ionic Liquid and Its Application in Lithium Battery

Lithium (Li) metal has been considered as an important anode candidate to reach more powerful energy storage devices with higher gravimetric and volumetric capacities. Nevertheless, the growth of high surface area lithium (HSAL) and dendrites during the stripping/deposition of Li causes safety concerns and a low cycle life of Li metal batteries. Here, we report the obtained results for protection of metallic lithium surface by using a gel polymer ionic liquid cross-linked by activation with UV radiation (UV-PIL). The UV-PIL protects Li against the constant degradation caused by the formation of unstable lithium metal electrolyte interphase and cell dry out due to continuous electrolyte consumption. We observed retarded growth of dendrites when lithium metal was protected with UV-PIL, and due to the lower ionic conductivity of UV-PIL, some differences of mass transport are present compared to carbonate-based liquid electrolyte. Nevertheless, the UV-PIL@Li negative electrode was successfully applied in a Li-ion battery with a lithium iron phosphate (LFP) positive electrode, showing similar behavior compared to the bare Li surface.