Study on ionic liquid-based gel polymer electrolytes for dual-graphite battery systems

Compared with Li-ion batteries, dual-graphite batteries (DGBs) have low cost, easy handling, and renewable advantages. However, DGBs with pure ionic liquid as the electrolyte (LEDGBs) suffer from high self-discharge rate (SDR). Here, a gel polymer electrolyte (ILGPE) was prepared using polyvinylidene fluoride as the polymer matrix and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide as the electrolyte and assembled into a gel polymer double-graphite battery (IGDGB). The results show that the IGDGB has an initial discharge capacity of 34.9 mAh g-1, and SDR is only 3.63%/h lower than the LEDGB (25.07%/h) after resting for 3 h. Notably, even after resting for 10 h, the IGDGB still has a discharge capacity of 27.5 mAh g-1. Meanwhile, the electrochemical impedance spectroscopy analysis results indicate that the low SDR of IGDGB is due to the limiting effect of ILGPE on the carrier strength. This result provides an idea of self-discharge reduction strategy for other electrochemical energy storage systems with intercalation storage mechanism.