Crosslinked ionogels containing a Li-conducting inorganic phase as electrolyte for lithium-metal batteries

In the quest for the development of safer lithium-metal batteries (LMBs), the integration of inorganic fillers and ionic liquids into polymer matrices has emerged as a promising strategy to enhance safety, ionic conductivity and battery performance. This study introduces a novel composite ionogel (IG) synthesized through a facile one-pot method, incorporating butyl methacrylate (BMA) and poly(ethylene glycol) diacrylate (PEGDA) with the ionic liquid 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR$_{14}$FSI) and garnet Li$_{6.4}$La$_{3}$Zr$_{1.4}$Ta$_{0.6}$O$_{12}$ (LLZTO) nanoparticles. A distinctive feature of the approach is the use of an organosilane functionalization of the LLZTO nanoparticles, which ensures their full integration into the polymer matrix during free-radical polymerization. Moreover, this method effectively eliminates the Li$_2$CO$_3$ passivation layer that typically forms on the surface of the LLZTO nanoparticles, thus, further contributing to an enhanced performance. As a result, a LMB with the functionalized LLZTO IG electrolyte delivered more than 160 mA h g$^{−1}$ with a very good capacity retention of 97.7% after 400 cycles in Li|IG|LFP cells.