In-situ Crosslinked Gel Polymer Electrolytes Based on Ionic Monomers as Charge Carriers for Lithium-Ion Batteries

Abstract

In-situ polymerization is a method for fabricating lithium-ion batteries to contain solid or gel electrolytes without major manufacturing changes. Gel polymer electrolytes (GPEs) wherein some polymer in incorporated, decreasing the volume of liquid electrolyte, have been pursued as they may be safer. One challenge with GPEs is reduced ion transport properties. In this work, macromonomers with different chain chemistry and ionic monomers are crosslinked on electrospun polyvinylidene difluoride (PVDF) in the presence of solvents, without conventional salt, to in-situ fabricate GPEs with elevated transference number within coin cells. These GPEs would be single-ion conductors in the case of complete ionic monomer polymerization to the crosslinked network. The effect of chain chemistry and the percentage of macromonomers and ionic monomers in the GPEs on conductivity are investigated. It is found that poly(siloxane) diacrylate (PDMSDA)- and perfluoropolyether tetra-acrylate (PFPETA)-based GPEs outperform the poly(propylene glycol) diacrylate (PPGDA)- and poly(tetrahydrofuran) diacrylate (PTHFDA)-based GPEs in terms of ionic conductivity. The highest ionic conductivity was achieved for a PDMSDA-based GPE at 4.2 × 10-4 S/cm at 23°C. Graphite/NMC-811 full cells prepared with the in-situ polymerized PDMSDA-based GPEs show capacity retention of 82.6% after 100 cycles, albeit with limited electrode utilization due to ion transport limitations.