The effects of functional ionic liquid on properties of solid polymer electrolyte

Polyethylene oxide (PEO) based solid state electrolytes have been thought as promising electrolytes to replace the organic liquid electrolyte for lithium ion batteries. But the lower ionic conductivities at room temperature restrict their application. In this paper, functional ionic liquid and polymer mixed electrolytes are prepared from N-methyoxymethyl-N-methylpiperidinium bis(trifluoromethanesulfonyl)imide (PP1.1O1TFSI) and polyethylene oxide. The PP1.1O1TFSI, a kind of room-temperature molten salt, was added to the conventional P(EO)20LiTFSI polymer electrolyte and resulted in a significant improvement of the ionic conductivity at room temperature. LiFePO4/Li and Li4Ti5O12/Li cells using this kind of electrolyte show high reversible capacity and stable cycle performance.

► The functional ionic liquid(IL)-polymer electrolytes were successfully prepared.
► The ionic conductivity of PEO electrolytes was raised to above 10-4 S·cm-1 at room temperature by functional IL.
► The cells using functional IL-PEO electrolyte show higher reversible capacity and long cycle life.