Improvement of Lithium-Ion Battery Performance at Low Temperature by Adopting Ionic Liquid-Decorated PMMA Nanoparticles as Electrolyte Component

A novel electrolyte system blending ionic liquid (IL)-decorated PMMA nanoparticles with 1 M LiTFSI dissolved in a mixture of propylene carbonate (PC) and methyl acetate (MA) is reported. With the addition of PMMA-IL-TFSI, this electrolyte exhibits an ionic conductivity of 9.15 × 10^-4 S cm^-1 even at -40 °C. The improved ionic conductivity at low temperature is attributed to the liquid component in the electrolyte and the unique grafting structure of IL groups on PMMA nanoparticles. Furthermore, it is proved that the presence of PMMA-IL-TFSI can improve the reversible capacity and rate capability of Li₄Ti₅O₁₂ (LTO)/Li half cells at low temperature. In addition, the morphology change and the electrochemical impedance spectroscopy (EIS) results indicate that the enhancement in battery performances is mainly attributed to the increase of ion conduction via the formation of a stable and effective SEI film on the electrode. These attributes enable the developed PMMA-IL-TFSI-based electrolyte to be a potential ingredient in high-performance lithium-ion batteries at low temperature.