The development of high-performance battery separators is pivotal to advancing the safety, efficiency, and lifespan of rechargeable energy storage systems. Conventional polyolefin-based separators, such as polyethylene (PE) and polypropylene (PP), face critical limitations including low thermal stability, poor electrolyte wettability, and susceptibility to dendrite penetration. These drawbacks are particularly pronounced in high-energy-density systems like lithium-metal and lithium-sulfur batteries, where interfacial instability and thermal hazards pose significant risks. To address these challenges, this study presents a novel multifunctional nanofiber membrane fabricated via electrospinning and chemical cross-linking of a hybrid precursor composed of polyacrylonitrile (PAN) and amphiphilic poly(ethylene glycol)diacrylate-grafted siloxane (TPT). The resulting cross-linked electrospun nanofiber (CEN) membrane exhibits exceptional mechanical strength, high thermal resilience, superior electrolyte affinity, and effective suppression of polysulfide shuttle effects—making it ideal for use in diverse battery architectures.
The synthesis of the TPT cross-linking agent is achieved through thiol-ene “click” chemistry between PEGDA and thiosiloxane, forming a dual-functional network that combines the robustness of siloxane backbones with the ion-conducting properties of ethylene oxide (EO) chains. This hybrid system enables precise control over surface polarity and nanostructure formation. After electrospinning the TPT/PAN solution onto a rotating collector, the nascent nanofibers undergo cross-linking in aqueous formic acid, leading to the formation of covalent Si–O–Si bonds and enhanced inter-fiber connectivity. Scanning electron microscopy reveals a highly porous, interconnected fibrous network with an average fiber diameter of 500 nm and pore size of 600 nm. The membrane demonstrates a porosity of 77.9%, significantly higher than commercial PP separators (41%), which facilitates rapid ion transport and high electrolyte uptake. The CEN separator absorbs up to 353% of EC/DMC, 346% of DOL/DME, and 344% of water—indicative of its strong capillary action and compatibility with both nonaqueous and aqueous electrolytes.
Wettability analysis confirms the amphiphilic nature of the CEN surface: contact angles for EC/DMC, DOL/DME, and H₂O drop to nearly 0° within 2 seconds, compared to 100°, 50°, and 130° on PP separators. Meniscus tests show complete capillary rise of electrolytes within 3 minutes, whereas PP membranes fail to draw liquid upward. This behavior is attributed to polar functional groups—Si–O–Si, C=O, C–O, and CN—that promote strong interactions with polar solvents and ions. Nuclear magnetic resonance (¹H NMR) and FTIR spectroscopy confirm the consumption of acrylate double bonds during the thiol-ene reaction, validating successful TPT formation and subsequent cross-linking.
Mechanical testing shows a dramatic improvement in tensile strength—from 3.2 MPa in uncross-linked TPT-PAN fibers to 18.8 MPa after cross-linking—alongside a modulus increase from 0.61 MPa to 100 MPa. This enhancement arises from the formation of dense cross-links and Si–O–Si bridges, which reinforce the nanofibrous structure. Thermal stability assessments reveal no measurable shrinkage or melting at 160 °C, while PP separators begin to shrink at 140 °C and fully melt within 20 seconds. Differential scanning calorimetry (DSC) indicates a glass transition temperature (Tg) of -50 °C and a decomposition onset above 200 °C, enabling operation across a wide temperature range (-50 to 200 °C).
Electrochemical evaluation confirms the CEN separator’s superiority in lithium-metal batteries. Linear sweep voltammetry shows no decomposition current up to 4 V, indicating excellent electrochemical stability. Ionic conductivity reaches 1.62 mS cm⁻¹—over twice that of PP (0.71 mS cm⁻¹)—while the lithium-ion transference number (tLi⁺) is 0.9004-32-4 Synonym 54 versus 0.887375-67-9 Description 25 for PP.PMID:34378829 In Li//Cu half-cells, the CEN separator reduces nucleation overpotential to -32 mV (vs. -156 mV for PP) and maintains a voltage difference of only 23 mV after 50 cycles, compared to 58 mV for PP. Ex situ SEM imaging reveals uniform granular lithium deposition on Cu with CEN, whereas PP leads to needle-like dendrites that compromise safety and cycle life.
In full-cell Li//LiFePO₄ configurations, CEN-separator cells deliver a stable capacity of 133 mA h g⁻¹ after 1000 cycles at 0.3 C, with a Coulombic efficiency of 99.8% and a fade rate of just 0.03% per cycle. In contrast, PP-based cells degrade rapidly, dropping to 95 mA h g⁻¹ after 400 cycles. The dendrite-free lithium deposition is attributed to the homogeneous Li⁺ flux enabled by the polar surface and high wettability.
For lithium-sulfur batteries, the CEN separator effectively mitigates the polysulfide shuttle effect. Density functional theory (DFT) calculations reveal strong binding energies between Li₂Sₓ species (x = 4–8) and the CEN surface—up to -1.43 eV for terminal Si–O–Si sites. In situ UV-vis spectroscopy shows minimal absorbance increase at 330 and 430 nm during discharge, confirming suppressed polysulfide dissolution. Full-cell Li-S tests demonstrate a reversible capacity of 960 mA h g⁻¹ initially and 750 mA h g⁻¹ after 300 cycles—achieving 86% capacity retention. PP-based cells, in comparison, retain only 355 mA h g⁻¹ after 300 cycles.
Finally, flexible aqueous lithium-ion batteries using CEN separators between LiMn₂O₄ (LMO) and LiTi₂(PO₄)₃@C (LTP) electrodes exhibit outstanding performance. The cells deliver 98 mA h g⁻¹ at 0.2 C, maintain 80 mA h g⁻¹ after 50 cycles, and achieve 98% capacity retention over 200 cycles at 1 C. When bent to 170°, the cell successfully powers three LEDs, demonstrating excellent mechanical flexibility and electrochemical stability.
This work establishes a versatile, high-performance separator platform based on chemically cross-linked amphiphilic nanofibers. By integrating mechanical strength, thermal resistance, electrolyte affinity, and functional surface chemistry, the CEN membrane offers a universal solution for next-generation lithium-ion, lithium-metal, and lithium-sulfur batteries—advancing the frontier of safe, durable, and high-energy-density energy storage.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