Abstract:

Objective This study aims to address the contradiction between mechanical properties and ionic transport properties in polyethylene oxide （PEO）-based solid electrolytes when loaded with high concentrations of nitrile plasticizers. By utilizing electrospinning technology to construct a three-dimensional fiber network structure， this study investigates the regulatory mechanisms governing the mechanical support and ionic transport behavior of the electrolyte under high-load conditions. Additionally， conjugate electrospinning is employed to prepare a core-shell structured lithium iron phosphate （LFP） all-solid-state yarn electrode， providing both theoretical and experimental support for the application of flexible energy storage devices in fields such as wearable electronics and smart textiles.

Method Fiber-shaped PEO（polyethylene oxide）-based solid electrolytes （F-PEO） were prepared using the electrospinning method， with acetonitrile as the solvent， where the molar ratios of EO/Li⁺ = 28∶1， EO/Li⁺ = 32∶1， EO/Li⁺ = 36∶1 and EO/SN = 4∶1 were employed， along with a solid content of 6%. Electrospinning was conducted at a voltage of 15 kV， a receiving distance of 10 cm， and a collection roller speed of 800 r/min. A control sample （B-PEO） was prepared using the solution casting method. A core-shell structured electrode was constructed using conjugate electrospinning technology， with stainless steel yarn as the core fiber， a composite of LFP， conductive carbon black， and graphene oxide as the core layer， and F-PEO as the shell layer. The material properties were characterized using SEM， XRD， DSC， and an electrochemical workstation.

Results XRD testing indicated that the crystallinity of F-PEO decreased from 39% in B-PEO to 28%， attributing to the rapid solidification of the polymer solution under the influence of a high-voltage electric field during electrospinning， which inhibited the ordered arrangement of molecular chains. DSC results revealed that the glass transition temperatures of both materials are approximately -47 ℃， indicating that segmental motion could occur at low temperatures in the high-load nitrile system. Mechanical property testing showed that the tensile strength （0.796 MPa） and elongation at break （484%） of F-PEO were 4.2 times and 2.2 times those of B-PEO （0.153 MPa， 218%）， respectively. SEM observations revealed that the three-dimensional interpenetrating porous network structure of F-PEO disperses stress through fiber slippage， while the dense layered structure of B-PEO develops cracks and fractures upon stretching. Electrochemical testing showed that the conductivity of F-PEO at 30 ℃ reached 1.19×10⁴ S/cm， higher than that of B-PEO （6.98×10⁵ S/cm）. The lithium-ion conduction activation energy decreased from 0.36 eV to 0.33 eV， and the migration number increased from 0.4 to 0.43. Both materials showed an electrochemical window of 5.3 V. The assembled lithium symmetric battery exhibited stable cycling for over 1，500 h at 30℃ and 0.1 mA/cm²， with the interfacial impedance increasing only from 91.603 Ω to 95.447 Ω during a 120-hour storage period. SEM analysis of the all-solid-state yarn electrode demonstrated that the electrolyte uniformly coated the fibers to form a continuous layer with a thickness of （24.7 ± 1.5） μm， At 30 ℃ and 0.2 ℃， the initial discharge specific capacity of LFP-1 was 124.3 mA·h/g， with a coulombic efficiency of 96.88%. After 100 cycles， the capacity retention was 99.7%. At 0.1 ℃， the initial capacity of 130.97 mA·h/g was close to the theoretical value， and at 1 ℃， the capacity was 39.37 mA·h/g. After recovery at 0.1 ℃， the capacity retention was 99.5%， and the initial capacity could be activated to 145.1 mA·h/g， attributed to the a

Key words: fibrous solid electrolyte, lithium symmetric cell, flexible energy storage device, mechanical optimization, ion transport, electrochemical performance, electrospinning