Self-healing and shape-memory solid polymer electrolytes with high mechanical strength facilitated by a poly(vinyl alcohol) matrix

Abstract

Self-healing and shape-memory solid polymer electrolytes (SSSPEs) based on poly(vinyl alcohol) (PVA) with ureidopyrimidinone (UPy) and poly(ethylene glycol) (PEG) units (PVA-UPy-PEG) were successfully fabricated by the reactions of different chain length epoxide functionalized-PEG and 2(6-isocyanatohexylaminocarbonylamino)-6-methyl-4[1H]-pyrimidinone (UPy-NCO) with the hydroxyl of PVA. The SSSPE with the longest PEG side chain (PVA-UPy-PEG750) exhibited good thermal stability until 254 °C, a low glass transition temperature (−44.8 °C), excellent self-healing and shape-memory performance, and high tensile stress. The PVA-UPy-PEG750 also showed a high ionic conductivity of 1.51 × 10⁻⁴ S cm⁻¹ with an EO/Li⁺ ratio of 11 : 1 at 60 °C, wide electrochemical window (5.0 V vs. Li/Li⁺), and improved lithium-ion transference number (t_Li⁺ = 0.34). Moreover, the lithium plating/stripping behavior of SSSPEs indicated the improved interfacial stability between the polymer electrolyte and the lithium metal electrode. The Li/PVA-UPy-PEG750/LiFePO₄ cell exhibited a higher initial discharge capacity of 145 mA h g⁻¹ and maintained a discharge capacity of 117 mA h g⁻¹ after 150 cycles and a coulombic efficiency of 99% with 0.1C at 60 °C. The SSSPE could be a promising candidate as the all-solid-state polymer electrolyte for lithium-ion batteries.