Flexible aqueous lithium-ion batteries (ALIBs) represent a promising frontier in wearable and portable energy storage due to their inherent safety, low cost, and environmental compatibility. However, the development of high-performance separators remains a critical challenge, particularly in balancing mechanical robustness, electrolyte wettability, and long-term electrochemical stability under bending and cycling conditions. This study presents a novel amphiphilic nanofiber separator fabricated via electrospinning and chemical cross-linking of a hybrid system composed of polyacrylonitrile (PAN) and poly(ethylene glycol)diacrylate-grafted siloxane (TPT), resulting in a cross-linked electrospun nanofiber (CEN) membrane with exceptional properties tailored for flexible ALIBs.
The CEN separator is synthesized by first preparing the TPT cross-linking agent through thiol-ene “click” chemistry between PEGDA and thiosiloxane, which introduces both polar EO chains and thermally stable siloxane moieties into the polymer network. The TPT/PAN precursor solution is electrospun into a fibrous mat, followed by immersion in formic acid to induce chemical cross-linking. The resulting CEN membranes exhibit a highly porous, interconnected nanofibrous architecture with an average fiber diameter of 500 nm and pore size of 600 nm. Scanning electron microscopy confirms uniform morphology and excellent structural integrity. The porosity of the CEN separator reaches 77.9%, significantly surpassing commercial PP separators (41%), enabling efficient ion transport and enhanced electrolyte uptake.
Notably, the CEN separator demonstrates superior wettability toward aqueous electrolytes. Contact angle measurements reveal near-zero angles (approximately 0°) for water within 2 seconds, while PP separators show a contact angle of 130°. Meniscus tests confirm rapid capillary rise of water within 3 minutes, indicating strong hydrophilicity driven by polar functional groups—Si–O–Si, C=O, C–O, and CN—on the surface. The separator absorbs up to 344% of water, confirming its high affinity for aqueous systems. These features ensure intimate electrode-separator contact and minimize interfacial resistance, crucial for stable performance in ALIBs.
Mechanical evaluation shows a dramatic improvement after cross-linking: tensile strength increases from 3.2 MPa to 18.8 MPa, and Young’s modulus rises from 0.61 MPa to 100 MPa. This enhancement stems from covalent Si–O–Si bond formation between nanofibers, creating a rigid yet flexible network capable of withstanding repeated bending. Thermal stability is further confirmed by differential scanning calorimetry (DSC), which reveals a glass transition temperature (Tg) of -50 °C and no significant degradation below 200 °C. At 160 °C, the CEN separator maintains dimensional stability without shrinkage or melting—unlike PP separators, which begin shrinking at 140 °C and fully melt within 20 seconds.
Electrochemical testing in flexible ALIBs assembled with LiMn₂O₄ (LMO) cathode and LiTi₂(PO₄)₃@C (LTP) anode using 0.5 M Li₂SO₄ aqueous electrolyte demonstrates outstanding performance. Galvanostatic charge-discharge profiles at 1 C (138 mA h g⁻¹) show stable voltage plateaus and high reversibility. Rate capability tests reveal that the cell delivers reversible capacities of 98, 90, 62, 53, and 40 mA h g⁻¹ at 0.2, 0.5, 2, 3, and 6 C rates, respectively. Even at high current densities, the cell retains 80 mA h g⁻¹ after 50 cycles, indicating robust reaction kinetics and structural resilience.
Long-term cycling performance is exceptionally stable: the full cell maintains 98% capacity retention over 200 cycles at 1 C, with minimal polarization.58-85-5 medchemexpress The Coulombic efficiency remains above 99.EphA5 Antibody web 5%, suggesting a stable solid-electrolyte interphase (SEI) and suppressed side reactions.PMID:35066170 In situ analysis confirms consistent interfacial behavior throughout cycling, attributed to the hydrophilic nature of the CEN separator that promotes uniform ion distribution and prevents localized dehydration.
Mechanical flexibility is rigorously tested: the constructed ALIB successfully powers three light-emitting diodes (LEDs) under various bending angles—including 0°, 90°, and 170°—without any drop in voltage or current output. This highlights the excellent bendability and durability of the CEN separator, which can withstand mechanical stress without cracking or delamination.
X-ray diffraction (XRD) and SEM analyses of the LTP and LMO electrodes confirm phase purity and uniform coating, ensuring reproducible electrochemical performance. Electrochemical impedance spectroscopy (EIS) shows low charge-transfer resistance and stable interface evolution over time, further supporting the effectiveness of the CEN separator in maintaining a favorable electrode-electrolyte interface.
This work establishes the CEN nanofiber membrane as a multifunctional, flexible, and highly stable separator for aqueous lithium-ion batteries. Its combination of high porosity, superior wettability, excellent mechanical strength, thermal resilience, and long-term cycling stability makes it ideal for next-generation wearable and implantable devices. By addressing key limitations of conventional separators, this design paves the way for safer, more durable, and scalable aqueous battery systems with broad applicability in smart textiles, biomedical sensors, and flexible electronics.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
