Dual‐Additive Strategy with α‐Cyclodextrin Molecular Sieving and LiDFOB Interface Engineering for Stable NCM811||Li Batteries in Ether Electrolytes

Abstract Lithium metal batteries (LMBs) employing lithium metal anodes paired with nickel‐rich layered oxide cathodes, such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NCM811), are attractive due to their high energy density. However, they face significant challenges, including unstable electrode/electrolyte interfaces and Li dendrite growth. This work presents a dual‐additive strategy utilizing α‐cyclodextrin (α‐CD) and lithium difluoro(oxalate) borate (LiDFOB) to enhance ion transport properties and stabilize electrode/electrolyte interfaces, enabling the stable operation of NCM811||Li cells with ether‐based electrolytes. The macrocyclic α‐CD selectively constrains anion mobility via host‐guest interactions, significantly increasing the Li + transference number. This enhancement reduces concentration polarization and suppresses Li dendrite growth. The further incorporation of LiDFOB stabilizes the interfaces by promoting the formation of a robust, inorganic‐rich solid electrolyte interface (SEI) and a boron‐containing cathode electrolyte interface (CEI). Consequently, the Li||Li symmetric cell achieves long‐term cycling stability exceeding 1500 h at 5 mA cm −2 for 5 mAh cm −2 . Moreover, the NCM811||Li cell retains 83% of its capacity after 200 cycles at a rate of 1 C with a cutoff voltage of 4.3 V.