Sulfurized polyacrylonitrile (SPAN) represents one of the most promising directions for high-energy-density lithium (Li)-sulfur batteries. However, the practical application of Li||SPAN is currently limited by the insufficient chemical/electrochemical stability of electrode/electrolyte interphase (EEI). Here, a pinned EEI layer is designed for stabilizing a SPAN cathode by regulating the EEI formation mechanism in an advanced LiFSI/ether/fluorinated-ether electrolyte. Computational simulations and experimental investigations reveal that, benefiting from the nonsolvating nature, the fluorinated-ether can not only act as a protective shield to prevent the Li polysulfides dissolution but also, more importantly, endow a diffusion-controlled EEI formation process. It promotes the formation of a uniform, protective, and conductive EEI layer pinning into SPAN surface region, enabling the high loading Li||SPAN batteries with superior cycling stability, wide temperature performance, and high-rate capability. This design strategy opens an avenue for exploring advanced electrolytes for Li||SPAN batteries and guides the interface design for broad types of battery systems.

Despite cobalt (Co)-free/nickel (Ni)-rich layered oxides being considered as one of the promising cathode materials due to their high specific capacity, their highly reactive surface still hinders practical application. Herein, a polyimide/polyvinylpyrrolidone (PI/PVP, denoted as PP) coating layer is demonstrated as dual protection for the LiNi 0.96 Mg 0.02 Ti 0.02 O 2 (NMT) cathode material to suppress surface contamination against moist air and to prevent unwanted interfacial side reactions during cycling. The PP-coated NMT (PP@NMT) preserves a relatively clean surface with the bare generation of lithium residues, structural degradation, and gas evolution even after exposure to air with ∼30% humidity for 2 weeks compared to the bare NMT. In addition, the exposed PP@ NMT significantly enhances the electrochemical performance of graphite||NMT cells by preventing byproducts and structural distortion. Moreover, the exposed PP@NMT achieves a high capacity retention of 86.7% after 500 cycles using an advanced localized high-concentration electrolyte. This work demonstrates promising protection of Co-free/Ni-rich layered cathodes for their practical usage even after exposure to moist air.