Fast Charge and High Stability of Solid‐State Graphite Organic Ionic Plastic Crystal Composite Anodes

Abstract

AbstractAll‐solid‐state batteries (ASSBs) using organic ionic plastic crystals (OIPCs) are promising candidates to overcome the inherent safety issues of lithium‐ion batteries (LIBs). Although OIPCs have excellent process applicability in the roll‐to‐roll electrode fabrication process, their application as solid electrolytes incorporated in composite electrodes has yet to be demonstrated in detail. Herein, we denote the positive effect of the N‐ethyl‐N‐methylpyrrolidinium bis(fluorosulfonyl)imide ([C2mpyr][FSI]) incorporated within a composite graphite anode on the charge rate capability and cycle life. The highest charge capacity ratio (the charge capacity at 2C vs. that measured at 0.1C) was measured for the composite anode with an OIPC composite ratio of 50 wt % (89.5 %, 295.7 mAh/g at 2C charge), almost the same as that of the graphite anode with a liquid electrolyte (85.7 %, 295.9 mAh/g at 2C charge). More favorable lithium‐ion conduction pathways were resolved for the anode with a higher OIPC composite ratio, whereas an excessive amount of OIPC reduced the long‐term cyclability. The most stable discharge capacity retention was obtained for 30 wt % OIPC composite (257.4 mAh/g at the 100th discharge), which showed no signs of discharge capacity fading within 100 cycles. The lithiation/delithiation process of the solid‐state graphite‐[C2mpyr][FSI] composite anode was evaluated to be stable and reversible. In addition, the incorporated OIPC composite enhanced the electrolyte/electrode and electrode/current collector contacts. This work highlights multiple advantageous functions of the OIPC in a composite graphite anode, which will broaden our horizons for the use of OIPC composites in ASSBs.