C-F-rich oil drop as non-expendable fluid interface modifier with low surface energy to stabilize Li metal anode
Metallic Li is the most promising anode material for next-generation batteries pursuing higher energy densities. However, its uncontrollable electro-deposition would cause unstable breakage of solid electrolyte interphase (SEI) and severe dendrite growth, hindering the commercialization of Li metal batteries (LMBs). Here, a strategy of non-expendable fluid interface modification is proposed by interposing a C-F-rich oil drop (PFPE) with low surface energy to address the deformation issue of Li anode. Different from usual additives which disperse in electrolyte and sacrifice during cycling, this laminated oil drop can endurably protect Li anode from side reaction with electrolyte and mitigate Li-salt consumption. Its high fluidity and inertness enable a ‘dynamic’ healing of ‘hot-spots’ without the compromise of Li+ permeability and Li nucleation kinetics. The PFPE moieties near Li skin trigger the interface enrichment of C-F and Li-F components to reinforce the robustness of SEI and compactness of Li plating (from mosaic-tile-like packing to dense interconnected network). This strategy endows LiNi0.8Mn0.1Co0.1O2/Li full cells with ultralong cycling life (over 700 cycles) and ultrahigh rate endurance (up to 10 C). This study provides a new route to high-performance LMBs based on immiscible liquid interlayer as permanent modulator.