Remarkable Conductivity of a Self-Healing Single-Ion Conducting Polymer Electrolyte, Poly(ethylene-<i>co</i>-acrylic lithium (fluoro sulfonyl)imide), for All-Solid-State Li-Ion Batteries

Abstract

Single-ion conducting polymer electrolyte (SICPE) is a safer alternative to the conventional high-performance liquid electrolyte for Li-ion batteries. The performance of SICPEs-based Li-ion batteries is limited due to the low Li⁺ conductivities of SICPEs at room temperature. Herein, we demonstrated the synthesis of a novel SICPE, poly(ethylene-<i>co</i>-acrylic lithium (fluoro sulfonyl)imide) (PEALiFSI), with acrylic (fluoro sulfonyl)imide anion (AFSI). The solvent- and plasticizer-free PEALiFSI electrolyte, which was assembled at 90 °C under pressure, exhibited self-healing properties with remarkably high Li⁺ conductivity (5.84 × 10^-4 S cm^-1 at 25 °C). This is mainly due to the self-healing behavior of this electrolyte, which induced to increase the proportion of the amorphous phase. Additionally, the weak interaction of Li⁺ with the resonance-stabilized AFSI anion is also responsible for high Li⁺ conductivity. This self-healed SICPE showed high Li⁺ transference number (ca. 0.91), flame and heat retardancy, and good thermal stability, which concurrently delivered ca. 88.25% (150 mAh g^-1 at 0.1C) of the theoretical capacitance of LiFePO₄ cathode material at 25 °C with the full-cell configuration of LiFePO₄/PEALiFSI/graphite. Furthermore, the self-healed PEALiFSI-based all-solid-state Li battery showed high electrochemical cycling stability with the capacity retention of 95% after 500 charge-discharge cycles.