Regulate the Uniform Deposition of Lithium Through MgF2/Hydroxypropyl Modified Polyethylene Separator Applied to Lithium Metal Batteries

Abstract

The uneven growth of lithium dendrites not only compromise the performance of lithium metal batteries, but also has security risks. In this sutudy, double coating with MgF₂ and hydroxypropyl methylcellulose was synthesized on the surface of polyethylene separator through a simple soaking and in-situ chemical precipitation method, achieve the purpose of protecting lithium metal anode. Utilizing the MgF₂/HPMC@PE separator, the Li||Li symmetric cell was capable of cycling for over 1000 hours with a voltage hysteresis of only 11.4 mV, comparing the voltage hysteresis based on the cell use of PE separator increases rapidly after 200 h. Furthermore, the initial discharge capacity of Li||LiNi_0.6Co_0.2Mn_0.2O₂(NCM622) is 144.6 mAh g⁻¹ and the capacity retention is 87.2 % after 200 cycles at 1 C, which is higher than that of the PE separator (135.3 mAh g⁻¹, with retention of 74.9 %). All improvements can be credited with the formation of stable solid electrolyte interphase(SEI) film induced by HPMC/MgF₂ double coating, which is reduced the Li nucleation overpotential and ultimately promoted uniform Li deposition. This study provides a simple and effective strategy for improving the cycling performance and safety of lithium metal batteries.