In situ crosslinked PMMA gel electrolyte from a low viscosity precursor solution for cost-effective, long lasting and sustainable lithium-ion batteries

To address the shortcomings of current gel electrolytes such as cost, processability, safety and sustainability, we report here on the in situ preparation of a crosslinked gel polymer electrolyte by polymerization of methyl methacrylate with poly(ethylene glycol) dimethacrylate within a liquid electrolyte composed of an ethylene carbonate/propylene carbonate low volatility solvent mixture. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is used as main lithium salt since it is stable thermally and vs. hydrolysis, which is advantageous for gel formation and recycling. Aluminum current collector corrosion and the efficient operation of the graphite anode are addressed via the use of lithium bis(oxalato)borate (LiBOB), vinylene carbonate and 1-propene 1,3-sultone as additives. The self-standing elastomeric gel electrolyte allows reaching conductivities close to those of the liquid fraction with a conductivity of 3.9 mS cm(-1) at 20 degrees C probably due to a high mobility as suggested by the glass transition temperature that is almost unaffected by the presence of the polymer. From a processing point of view, the use of methyl methacrylate (MMA) allows decreasing the viscosity of the precursor solution for efficient wetting of the cell components prior to thermal polymerization. The good contact allows cycling graphite/LiMn0.33Ni0.33Co0.33O2 (NMC111) cells with a 2.1 mAh cm(-2) areal capacity steadily for hundreds of cycles.