Multifunctional Interlayer\nIncluding Metal Fluoride–Modified\nPAN/PSF–Based Superfine and Porous Carbon Nanofibers for Stable\nLithium Metal Cells

In this study, yttrium fluoride–modified PAN/PSF–based\nsuperfine and porous carbon nanofibers (YF<sub>3</sub>–PAN/PSF-CNFs)\nbased on the “Tug-of-War” refinement mechanism of heterogeneous\nviscous fluid are designed and prepared through electro-blow spinning\nand subsequent carbonization processes. The prepared YF<sub>3</sub>–PAN/PSF-CNFs are applied as an important component of the\nfunctional interlayer to study its effect on the electrochemical performance\nand safety of lithium metal cells. The interconnected framework of\nYF<sub>3</sub>–PAN/PSF-CNFs, with high conductivity and a large\nspecific surface area, can provide facilitated lithium ion and electron\ntransmission channels and lower local current density. The lithiophilic\nYF<sub>3</sub> also can provide enough active sites to produce an\nalloying reaction with lithium ions to uniformly guide lithium deposition.\nFor the assembled Li||LiFePO<sub>4</sub> battery, after 650 cycles\nat 0.5 C, it still maintained a high specific discharge capacity of\n154.9 mAh g<sup>–1</sup>. The assembled Li||Li symmetric battery,\nbased on the prepared functional interlayer, further presented that\nthe functional YF<sub>3</sub>–PAN/PSF-CNFs interlayer can significantly\nsuppress the growth of lithium dendrites and greatly improve cycle\nstability, with the batteries having relatively stable low overpotential\nwithin a 1000-h cycle time, and the voltage amplitude is basically\nstable within ±0.1 V. At the same time, the assembled lithium–sulfur\n(Li||S) cell equipped with the interlayer based on the YF<sub>3</sub>–PAN/PSF-CNFs also presents outstanding cycle stability. The\nmain reasons for this result are ascribed to the synergistic effect\nof physical confinement and chemical adsorption of the YF<sub>3</sub>–PAN/PSF-CNFs effectively reducing the “shuttle effect”\nof lithium polysulfide. All the results illustrate that the application\nof the YF<sub>3</sub>–PAN/PSF-CNFs interlayer can provide insights\ninto enhancing electrochemical performances and protecting the lithium\nanode of the lithium metal cell.