A novel gel polymer electrolyte based on trimethylolpropane trimethylacrylate/ionic liquid via in situ thermal polymerization for lithium-ion batteries

Gel polymer electrolytes (GPEs) based on trimethylolpropane trimethylacrylate (TMPTMA) are in situ polymerized using lithium bis(trifluoromethane)sulfonimide (LiTFSI), dimethylcarbonate (DMC) and ionic liquid (IL)-tributylmethylammonium bis(trifluoromethanesulfonyl) imide (N1,4,4,4TFSI). The GPEs presented both the liquid-like ionic transport and solid-like features. The N1,4,4,4TFSI can effectively dissociate the lithium salts to boost ionic transport, and thus delivers a high ionic conductivity of 6.15 x 10(-3) S cm(-1) at 25 degrees C. The interfacial resistance between ionic liquid and lithium metals was reduced, resulting in the benign interfacial contact with Li metal electrode. Lithium ion batteries are assembled based on TMPTMAbased cross-linked gel polymer electrolytes (with LiCoO2 as positive electrode and lithium as negative electrode). The results suggest that the GPEs modified with ionic liquid presented improved cycling performance (with a discharge capacity of 111.1 mA h g(-1) after 100 cycles) and good capacity retention of 80%. Also, the GPEs hold favorable compatibility with the LiNi0.8Co0.1Mn0.1O2 positive electrode, exhibiting an initial discharge capacity of 183.1 mA h g(-1) as well as a stable capacity of beyond 149 mA h g(-1) after 100 cycles. The GPEs enable the assembled LiCoO2/Li and Li1.2Ni0.8Co0.1Mn0.1O2/Li batteries for well operating within a wide C rate range (0.1-2.0 C). The improved cycling behaviors can be attributed to the suppressed growth of the cell impedance and stable interface compatibility toward lithium metal negative electrode . (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The research on ionic liquid-modified gel polymer electrolytes based on TMPTMA shows promising applications in lithium ion batteries due to their good ion transport and stability.