Upgrading the Separators Integrated with Desolvation and Selective Deposition toward the Stable Lithium Metal Batteries.

Abstract

A practical and effective approach to improve the cycle stability of high-energy density lithium metal batteries (LMBs) is to selectively regulate the growth of the lithium anode. The design of desolvation and lithiophilic structure have proved to be significant means to regulate the lithium deposition process. Here, a fluorinated polymer lithiophilic separator (LS) loaded with a metal-organic framework (MOF801) is designed, which facilitates the rapid transfer of Li⁺ within the separator owing to the MOF801-anchored PF₆ ^- from the electrolyte, Li deposition is confined in the plane resulting from the polymer fiber layer rich in lithiophilic groups (C─F). The numerical simulation results confirm that LS induces a uniform electric field and Li⁺ concentration distribution. Visualization technology records the behavior of regular Li deposition in Li||Li and Li||Cu cells equipping LS. Therefore, LS exhibits an ultrahigh Li⁺ transference number (t_Li ⁺ = 0.80) and a large exchange current density (j₀ = 1.963 mA cm^-2). LS guarantees the stable operation of Li||Li cells for over 1000 h. In addition, the LiNi_0.8Co_0.1Mn_0.1O₂||Li cell equipped with LS exhibits superior rate and cycle performances owing to the formation of LiF-rich robust SEI layers. This study provides a way forward for dendrite-free Li anodes from the perspective of separator engineering.