Electrochemical behavior of organic radical polymer cathodes in organic radical batteries with N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid electrolytes

The electrochemical behavior of a poly(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl methacrylate) (PTMA) cathode in organic radical batteries with lithium bis(trifluoromethylsulfonyl)imide in N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (LiTFSI/BMPTFSI) ionic liquid electrolytes is investigated. The ionic liquid electrolytes containing a high concentration of the LiTFSI salt have a high polarity, preventing the dissolution of the polyvinylidene fluoride binder and PTMA in the electrolytes. The results of cyclic voltammetry and AC impedance indicate that an increase in the LiTFSI concentration results in a decrease in the impedance of the lithium electrode, which affects the C-rate performance of batteries. The discharge capacity of the PTMA composite electrode in a 0.6 m LiTFSI/BMPTFSI electrolyte is 92.9 mAh g−1 at 1 C; its C-rate performance exhibits a capacity retention, 100 C/1 C, of 88.3%. Moreover, the battery with the 0.6-m LiTFSI/BMPTFSI electrolyte has very good cycle-life performance.

► Pyrrolidinium ionic liquid was used as an electrolyte in an organic radical battery. ► Addition of lithium salt suppresses the dissolution of the polyvinylidene fluoride binder into the electrolyte. ► Addition of lithium salt decreases the resistance of the solid electrolyte interface film. ► Cells with the pyrrolidinium ionic liquid electrolytes demonstrate excellent electrochemical performance.