A stable protective layer toward high-performance lithium metal battery

Abstract

Metal lithium anodes are quite promising for next-generation batteries due to their high energy density and low voltage, which has attracted numerous attention of the researchers. However, the main challenge for lithium anodes still lies on their serious dendrite problems, leading to the poor cycling stabilities. Here, we introduced poly(vinylidene-co-hexafluoropropylene) (PVDF-HFP) composite film combined with nano alumina (nano-Al2O3), lithium fluoride (LiF) and lithiumbis(trifluoromethanesulphonyl)imide (LiTFSI), as a stable protective layer (SPL), to coat on the surface of cooper current collector, which was beneficial to improve the cycling stabilities of the fabricated lithium–copper (Li–Cu) half-cell. The copper foil electrode modified with the protective layer exhibited a much enhanced cycling performance compared with the one without modification, which did not show obvious capacity decay after 250 cycles at the current density of 0.5 mA/cm2 for 2 h. From SEM and XPS characterizations, it had to be found that the preset protective composite layer kept a stable structure during the charge and discharge process, which guaranteed the achieved stable cycling performance. In addition, a full battery system based on modified copper foil anode and LiFePO4 cathode also constructed and presented a good cycling performance.