POSS hybrid poly(ionic liquid) ionogel solid electrolyte for flexible lithium batteries

Abstract

Traditional lithium-ion batteries based on liquid electrolytes cannot adapt to the increasing and various highly flexible requirements. In this work, a confinement-driven strategy has been developed to confine the ionic liquids in a polyhedral oligomeric silsesquioxanes (POSS) and poly(ethylene glycol) diacrylate (PEGDA) hybrid cross-linked poly(ionic liquid)s ionogel (POSS-CPIL-n), which endows this novel electrolyte superior flame retardancy and dramatically flexibility. The POSS-CPIL-n ionogel renders exceptional flexibility (bend, fold and twist) and desired mechanical properties (2.5 MPa). Advantageous for high dissociation of lithium salt, high ionic conductivity (2.5 mS cm−1 at 25 °C) and considerable lithium ion mobility (0.51) are provided. Thanks to the flexibility of ionogel electrolyte together with excellent thermal and electrochemical stability, the LiFePO4||Li cell based on POSS-CPIL-n exhibits significant rate performance and cycling stability, the capacity of the cell can reach to 100 mAh g−1 at 4 C and maintain a substantial discharge capacity of 160.5 mAh g−1 after 200 cycles at 0.2C. Furthermore, the soft-package assembled with POSS-CPIL-n can successfully charge a cell phone and continue to supply power stably even when the battery is exposed to the air, which indicates that POSS-CPIL-n has a promising potential application in high safety flexible electronic devices.