A robust, highly stretchable ion-conducive skin for stable lithium metal batteries

Lithium metal anode is strongly considered as the ‘Holy Grail’ anode for the next generation energy storage system. However, the major obstacle towards lithium metal batteries (LMBs) is the unstable solid electrolyte interface (SEI) because of its high reactivity, which can result in dendrite growth, dead lithium accumulation and even short circuit. Herein, the highly ion-conductive, stretchable and stable artificial SEI layer derived from Polymethyl methacrylate (PMMA)/Poly(vinylidene fluoride) (PVDF) hybrid polymer is fabricated through an in-situ reaction during the preparation and electrochemical process. In this way, LiF and Li-O bond would be generated in the interface of the PMMA/PVDF layer and lithium metal, which can provide fast ion transport channels during lithium stripping and plating process. Furthermore, the robust and flexible polymer coating can simultaneously adapt the volume change and suppress dendrite growth. Therefore, based on the synergistic effect between PMMA and PVDF, the PMMA/PVDF-Li delivers ultrahigh cycling stability at 2 mA cm⁻² with an areal capacity of 1 mAh cm⁻² for more than 2000 h. The corresponding PMMA/PVDF-Li||NCA full cell also exhibits superior stability with a high capacity retention of 82.3% at 2 C rate after 300 cycles.