Self-healing and shape-memory solid polymer electrolytes with high mechanical strength facilitated by a poly(vinyl alcohol) matrix
Self-healing and shape-memory solid polymer electrolytes (SSSPE) 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 lengths of epoxide functionalized-PEG and 2(6-isocyanatohexylaminocarbonylamino)-6methyl-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 oC, low glass transition temperature (-44.8 oC), excellent self-healing and shape-memory performance, and high tensile stress. The PVA-UPy-PEG750 also showed the high ionic conductivity of 1.51 × 10-4 S cm-1 with EO/Li+ ratio of 11:1 at 60 oC, wide electrochemical window (5.0 V vs. Li/Li+), and improved lithium-ion transference number (tLi+ = 0.34). Moreover, the lithium plating/stripping behavior of SSSPE indicated the improved interfacial stability between polymer electrolyte and lithium metal electrode. The Li/PVA-UPy-PEG750/LiFePO4 cell exhibited a higher initial discharge capacity of 145 mAh g-1, and maintained a discharge capacity of 117 mAh g-1 after 150 cycles and a coulombic efficiency of 99% with 0.1C at 60 oC. The SSSPE could be a promising candidate as the all-solid-state polymer electrolyte for lithium-ion battery.