Lab Electrospinning System| Three-dimensional flame-retardant quasi-solid composite electrolyte with a fiberstructure formed using the coaxialelectrospinning to suppress lithiumdendrite growth

In the current era of rapid development in new energy technologies, lithium-ion batteries play a pivotal role as the core power source in electric vehicles, electronic devices, and many other fields. The improvement of their safety and performance remains a key focus for both academia and industry. Achieving high ionic conductivity and good mechanical properties while effectively suppressing lithium dendrite growth and enhancing thermal stability has become a critical bottleneck in advancing lithium batteries toward higher energy density and safety. The growth of lithium dendrites may not only puncture battery separators, causing safety hazards such as short circuits, but also reduce battery cycle life. Meanwhile, insufficient thermal stability may lead to thermal runaway under high-temperature conditions, posing serious safety risks. Therefore, exploring electrolyte technologies that combine both efficiency and safety has become imperative.

Recently, the research team of Gaofeng Zheng and Huangping Yan from Xiamen University published a study titled "Three-Dimensional Flame-Retardant Quasi-Solid Composite Electrolyte with a Fiber Structure Formed Using the Coaxial Electrospinning to Suppress Lithium Dendrite Growth" in Chemical Engineering Journal. The team successfully prepared a PVDF/SiO₂@LLTO quasi-solid composite electrolyte (QSCE) with a three-dimensional core-shell fiber structure by combining polyvinylidene fluoride (PVDF), silica (SiO₂), and lithium lanthanum titanate (LLTO) through coaxial electrospinning technology. This unique fiber structure not only effectively suppresses lithium dendrite growth but also significantly improves thermal stability, safety, and electrochemical performance, providing new insights and practical approaches for developing high-energy-density and reliable energy storage solutions.

Figure 1: Demonstration of lithium dendrite suppression and thermal stability

The flame retardancy and thermal stability of electrolytes are crucial factors affecting the safety of lithium-ion batteries. The study employed multiple strategies to synergistically suppress lithium dendrite growth, significantly enhancing thermal stability and safety. Experimental results showed that lithium symmetric batteries based on PVDF/SiO₂@10LLTO QSCE exhibited no significant lithium dendrite formation after prolonged cycling tests. In thermal shrinkage tests at 160°C, the shrinkage rate after one hour was only 1.79%, demonstrating excellent thermal stability. When exposed to an open flame, the electrolyte self-extinguished immediately while maintaining structural integrity, showcasing outstanding flame retardancy and safety.

Figure 2: Preparation process of QSCE with three-dimensional fiber structure

During preparation, LLTO nanoparticles were first synthesized and then mixed with PVDF, SiO₂, and LiTFSI. Using coaxial electrospinning technology, PVDF/SiO₂ solution was used as the inner spinning fluid, and LLTO solution as the outer spinning fluid, successfully constructing a three-dimensional core-shell fiber structure. In this structure, LLTO nanoparticles were mainly distributed in the fiber shell, forming efficient ion conduction pathways and enhancing structural stability, while PVDF and SiO₂ constituted the fiber core, providing mechanical support and improving thermal stability.

Figure 3: Mechanical and thermal properties of different QSCEs

The study evaluated the mechanical and thermal properties of different QSCEs. Results showed that PVDF/SiO₂@10LLTO QSCE exhibited excellent thermal stability and flame retardancy. Further research found that the introduction of LLTO nanoparticles significantly improved ionic conductivity. However, excessive addition might adversely affect mechanical properties. Mechanical tensile tests on QSCE samples with different LLTO mass fractions revealed that tensile strength first increased and then decreased with increasing LLTO content. When the LLTO content was 10 wt%, the tensile strength peaked at 46.8 MPa, significantly higher than that of traditional Celgard separators, samples without LLTO, or those with excessive LLTO, fully validating its good mechanical stability.

Figure 4: Electrochemical performance of different QSCEs

The electrochemical performance of PVDF/SiO₂@LLTO QSCE was systematically evaluated. Experimental data indicated that ionic conductivity first increased and then decreased with increasing LLTO mass fraction. When the LLTO content was 10 wt%, the ionic conductivity reached a maximum of 1.26×10⁻⁴ S·cm⁻¹ at 25°C, along with a wide electrochemical window of 4.45 V and low interfacial impedance of 214.51 Ω. In battery performance tests, lithium iron phosphate (LiFePO₄) batteries based on PVDF/SiO₂@10LLTO QSCE demonstrated excellent cycling stability and rate capability, with an initial capacity of 174 mAh·g⁻¹ and a capacity retention rate of 95% after 100 charge-discharge cycles, significantly outperforming samples without LLTO and traditional Celgard2325 separator batteries, fully validating the significant advantages of this composite electrolyte in improving overall battery performance.

Figure 5: Lithium dendrite suppression capability of different QSCEs

Long-term cycling tests on lithium symmetric batteries confirmed the ability of PVDF/SiO₂@10LLTO QSCE to suppress lithium dendrite growth. Results showed that the QSCE maintained stable operation for 400 hours without short circuits, with the lithium anode surface remaining smooth. In contrast, samples without LLTO experienced short circuits after 155 hours, with obvious lithium dendrite formation observed on the anode surface. Additionally, electrochemical impedance spectroscopy (EIS) tests further confirmed that PVDF/SiO₂@10LLTO QSCE had good electrode-electrolyte interface contact, effectively blocking lithium dendrite penetration.

The coaxial electrospinning strategy proposed in this study provides new insights for developing high-performance electrolytes, effectively addressing key challenges such as dendrite suppression and interface compatibility in lithium batteries. This research offers new solutions for improving the safety and performance of lithium-ion batteries and provides theoretical and practical foundations for developing next-generation high-energy-density, safe, and reliable lithium-ion batteries.

Paper link: https://doi.org/10.1016/j.cej.2025.164616