Highly stretchable, non-flammable and notch-insensitive intrinsic self-healing solid-state polymer electrolyte for stable and safe flexible lithium batteries

Abstract

Solid-state polymer electrolytes (SPEs) with superior self-healing capacity are urgently required for next-generation flexible energy storage devices. Herein, a highly stretchable (extensibility > 4000% and stress > 130 kPa), non-flammable and notch-insensitive intrinsic self-healing solid-state polymer electrolyte (SHSPE) was prepared based on the combination of a poly(HFBM-co-SBMA) network, imidazole-based ionic liquid (EMI–TFSI) and LiTFSI. The incorporation of the imidazole cation and fluorine atom contributed to the formation of supramolecular bonds (ion–dipole interactions) inside the electrolyte framework, thus endowing SHSPE with prominent self-healing ability (recovery time < 60 min, 25 °C). Moreover, the density functional theory (DFT) calculations indicated that the large electrostatic attraction of SO₃⁻ towards Li⁺ liberated it from trapping in the ionic reservoir of TFSI⁻ and EMI⁺, thereby resulting in a superior t_Li⁺ (0.37). The electrochemical window of SHSPE achieved was 4.9 V vs. Li⁺/Li, which well satisfies the demand for safe lithium batteries. The optimized SHSPE3 presented excellent interfacial compatible property with a lithium electrode and record adhesion strength (weight loading > 200 g). The as-assembled Li/SHSPE3/LiFePO₄ battery delivered a high discharge capacity of 144.8 mA h g⁻¹ at 0.2C, and its capacity retention ratio reached 82% after 100 cycles with a coulombic efficiency of 97%. In particular, the mechanical properties and conductivity of SHSPE3 could fully recover after repeated damage, conferring the derived soft-pack battery excellent anti-fatigue capability. The use of intrinsic self-healing principles in the field of SPEs provides new insight for developing reliable and safe flexible electronic devices.