Moisture-assistant chlorinated separator with dual-protective interface for ultralong-life and high-rate lithium metal batteries

Metallic lithium (Li) is among the most promising anodes due to their high theoretical capacity (3860 mAh g^–1) and the lowest redox potentials (−3.04 V vs standard hydrogen electrode). However, the application of lithium metal batteries (LMBs) has encountered by the uncontrollable growth of Li dendrite and unstable solid electrolyte interface (SEI). Therefore, regulating a compositionally favorable and Li⁺-permeable SEI is crucial for the development of long-life LMBs. Previous studies have revealed the moisture as a detrimental inducement to cell degradation. Beyond current understanding, inorganic LiCl with adsorption of moisture is first applied to protect Li anode, where the hydrated and chlorinated separator has introduced LiF/artificial SEI dual-layer simultaneously with much improved cycle stability and interface compatibility over the non-hydrated counterparts. Meanwhile, the modified separator (with hydrated LiCl/poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) layer) has synergistically achieved the suppression of dendrite growth and interface distortion, restraining the decay of Li deposition/stripping for better cycle stability. Accordingly, the lifespan of modified Li|Li cell is extended to over 2700 h with improved rate capability, reduced overpotentials and high Coulombic efficiency (CE) of 99.5 %. Further, the moisture-assistant chlorinated separator is applied in energy-dense LMBs system, which allows for a stable and shuttle-free Li–S batteries with high sulfur utilization and chemically accelerated conversion kinetics. As a result, the dual-shield protected separator configuration synergistically fulfills high sulfur capacity of 1293.6 mAh g^–1 at 0.1 C (1C = 1675 mA g⁻¹), long-term Li–S cycle stability at 1 C and high-rate capability (582.2 mAh g^–1 at 5 C). This contribution provides insights of implementing moisture-assistant chlorinated separator for Li anode protection and high-performance Li–S batteries.