Yttrium trifluoride doped polyacrylonitrile based carbon nanofibers as separator coating layer for high performance...

In this study, the yttrium trifluoride-doped polyacrylonitrile(PAN) based carbon nanofibers (YF₃-PAN-CNFs) are successfully designed and prepared through the electro-blow spinning and carbonization strategies. And the YF₃-PAN-CNFs acted as main materials of functional layer for modifying separator of lithium metal batteries are systematically studied and analyzed. The prepared CNFs have long-range ordered structures and high conductivity, which can extremely improve the transport of lithium ions and electrons during charge-discharge processes. The lithiophilic YF₃ nanoparticles formed in the carbonization process can endow enough active sites to produce alloying reaction with Li, which makes the plating/stripping of Li more uniform. For the assembled Li||lithium iron phosphate (LiFePO₄) battery, it still maintains a high specific discharge capacity of 137.1 mAh g^-1 after 500 cycles at 0.5 C, which there is almost no specific discharge capacity degradation after long cycle. The modified separator for the Li||Li symmetric battery can effectively suppress the growth of lithium dendrites and improve cycle stability. Meanwhile, based on the strong chemical bonding between YF₃ and lithium polysulfide combining the effectively physical confinement of the YF₃-PAN-CNFs coating layer, the "shuttle effect" of lithium polysulfide also can be greatly suppressed. Thus the assembled Li||S battery using the separator has excellent electrochemical performance. Therefore, the YF₃-PAN-CNFs modified separator will have a promising application prospect in lithium metal batteries even other high performance secondary batteries.