Stretchable Coaxial\nGel Polymer Electrolyte Based\non a Styrene–Ethylene–Butylene–Styrene Block\nCopolymer Nanofiber for Stretchable Lithium-Ion Batteries

This paper describes the fabrication of stretchable coaxial\ngel\npolymer electrolytes (SC-GPEs) using electrospinning, which is a simple\nand inexpensive method. By combining a styrene–ethylene–butylene–styrene\n(SEBS) core and a poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene)\n(PVDF-HFP) shell, the SC-GPEs offer a unique combination of mechanical\nflexibility and electrochemical performance that is ideal for stretchable\nlithium-ion batteries. Control over the mechanical stretchability\nand electrochemical properties of the SC-GPEs is achieved by modulating\nthe composition ratio between the core and shell. Morphological investigations\nvia transmission electron microscopy and scanning electron microscopy\nconfirmed the successful integration of the stretchable SEBS core\nand PVDF-HFP shell within the SC-GPEs, which exhibit a diameter of\napproximately 1 μm. More importantly, the addition of SEBS significantly\nimproved both the elongation and Young’s modulus of the SC-GPEs,\nwith elongation values ranging from 71.5 to 207.4% depending on the\nPVDF-HFP/SEBS ratio. Cyclic loading tests show the ability of the\nSC-GPEs to undergo reversible deformation under mechanical stress,\nwith the SC-GPEs containing SEBS demonstrating superior resilience.\nMoreover, electrochemical analysis shows that the SC-GPEs exhibit\nthe typical ionic conductivity values ranging from 10<sup>–1</sup> mS cm<sup>–1</sup> and good electrolyte affinity, thus rendering\nthem appropriate for lithium-ion batteries. The Li-ion transference\nvalue of the SC-GPEs (0.6–0.7) surpasses that of conventional\nliquid electrolytes, thus suggesting excellent Li-ion selectivity.\nThe SC-GPEs have a high specific capacity of 140 mA h g<sup>–1</sup> at 0.5 C rates and good cycling performance with 71.0% capacity\nretention after 100 cycles, which surpasses that of liquid electrolytes\n(66%). This work presents high-stretchability gel polymer electrolytes\nand supports investigations into manufacturing processes for flexible\nfunctional membranes utilized in stretchable electronics.