Facile preparation of polymer electrolytes based on the polymerized ionic liquid poly((4-vinylbenzyl)trimethylammonium bis(trifluoromethanesulfonylimide)) for lithium secondary batteries

• A new polymer electrolyte incorporating a DEME-TFSI liquid is prepared.
• The ionic conductivity of the electrolytes reaches 7.58 × 10−4 S cm−1 at 60 °C.
• Batteries discharge 130 mAh g−1 at 0.1 C rates with good capacity retention.

The polymer electrolytes based on a novel poly((4-vinylbenzyl)trimethylammonium bis(trifluoromethanesulfonylimide)) polymeric ionic liquid (PIL) as polymer host and containing DEME-TFSI ionic liquid, LiTFSI salt and nano silica are prepared. The polymer electrolyte is chemically stable even at a higher temperature of 60 °C in contact with lithium anode. Particularly, the electrolyte exhibits high lithium ion conductivity, wide electrochemical stability window and good lithium stripping/plating performance. When the IL content reaches 60% (the weight ratio of DEME-TFSI/PIL), the PIL electrolyte presents a higher ionic conductivity, and it is 7.58 × 10−4 S cm−1 at 60 °C. Preliminary battery tests show that Li/LiFePO4 cells with the PIL electrolytes are capable to deliver above 130 mAh g−1 at 60 °C with very good capacity retention.

(A) The main components of PIL electrolytes, (B) A PIL electrolyte sample.Figure optionsDownload as PowerPoint slide