A functional SnS2-engineered separator for durable and practical lithium metal battery

Lithium (Li) metal is one of the most promising anodes for next-generation high-energy-density batteries. However, the practical application of Li metal anodes (LMAs) is hindered by uncontrollable solid electrolyte interphase (SEI) formation and detrimental Li dendrites growth. Herein, a well-designed SnS2 nanoflakes coating is utilized to modify the commercial polypropylene (PP) separator (denoted as SnS2@PP), providing a solution to tackle above issues. Impressively, an artificial SEI consisting of Li2S, Li5Sn2, and Li7Sn2 species with high ionic conductivity and superior Li affinity is generated on the Li surface to regulate homogeneous Li plating/stripping. Consequently, the Li||Li symmetric cells exhibit a stable cycling behavior of over 2700 h at 1 mA cm−2 for 1 mAh cm−2. Remarkably, SnS2@PP enables over 600 cycles at 2 C with a capacity retention of ∼80% in a Li||LiFePO4 coin cell and more than 110 cycles at 0.3 C with a capacity retention of ∼97% in a Li||LiFePO4 pouch cell under high cathode loading (13 mg cm−2), ultrathin Li foil (50 µm), and lean electrolyte (2.8 g Ah−1 after sealed) conditions. This work extends the scalable technology into a platform to control Li deposition and SEI formation toward practical Li metal batteries (LMBs) with ultralong life spans.