Sodium-ion batteries (SIBs) are emerging as promising low-cost and long-cycle energy storage systems. However, the poor wettability of the conventional polyolefin separators with polar electrolytes leads to low ionic conductivity and high battery resistance, causing rapid capacity decay. Herein, we propose using a polyethylene (PE) separator coated with a nanofiber composited of poly(vinylidene fluoride) (PVDF) and Al₂O₃ filler via electrospinning. Compared to the standard PE separators, this composite separator offers much improved electrolyte wettability, mechanical strength, and electrochemical stability. Electrochemical tests demonstrate that the Na[Ni_1/3Fe_1/3Mn_1/3]O₂||hard carbon pouch cells based on the PVDF-Al₂O₃/PE composite separator exhibit a capacity retention of 95.1% after 800 cycles at 1C. Additionally, the separator significantly enhances low-temperature discharge performance and cycling stability. Characterizations based on Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction confirm the successful integration of Al₂O₃ nanoparticles into the PVDF matrix, resulting in a homogeneously dispersed and well-connected structure, which improves ion transport efficiency and stability, thereby effectively boosting battery performance. This research highlights the potential of PVDF-Al₂O₃ nanofiber composite separators for advanced SIBs with high reversibility, a wide operating temperature range, and long cycling life.

中文翻译：

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电纺纳米纤维表面改性聚乙烯隔膜，用于增强钠离子电池的循环稳定性和低温性能


钠离子电池 （SIB） 正在成为有前途的低成本和长周期储能系统。然而，带有极性电解质的传统聚烯烃隔膜的润湿性差，导致离子电导率低，电池电阻高，导致容量快速衰减。在此，我们建议使用聚乙烯 （PE） 隔膜，通过静电纺丝涂有聚偏二氟乙烯 （PVDF） 和 Al₂O₃ 填料复合的纳米纤维。与标准 PE 隔膜相比，这种复合隔膜的电解液润湿性、机械强度和电化学稳定性大大提高。电化学测试表明，Na[Ni_1/3Fe_1/3Mn_1/3]O₂||基于 PVDF-Al₂O₃/PE 复合隔膜的硬碳软包电池在 1C 下循环 800 次后，容量保持率为 95.1%。此外，隔膜还显著提高了低温放电性能和循环稳定性。基于傅里叶变换红外光谱、扫描电子显微镜和 X 射线衍射的表征证实了 Al₂O₃ 纳米颗粒成功整合到 PVDF 基体中，从而产生均匀分散和连接良好的结构，从而提高了离子传输效率和稳定性，从而有效提升电池性能。这项研究强调了 PVDF-Al₂O₃ 纳米纤维复合隔膜在高级 SIB 中的潜力，这些隔膜具有高可逆性、宽工作温度范围和长循环寿命。