Non‐Corrosive Methide‐Based Lithium Salt for Stabilizing Ni‐Rich NMC Cathodes

ABSTRACT High‐nickel LiNi _x Mn _y Co _1‐x‐y O ₂ (NMC) cathodes are promising for next‐generation lithium‐ion batteries (LIBs) due to their high energy density, but their performance is limited by interfacial instability with conventional electrolytes. While lithium hexafluorophosphate (LiPF ₆ ) is widely used, its chemical instability (e.g., generating HF) undermines battery performance. Lithium imides such as lithium bis(trifluoromethanesulfonyl)imide (LiNTf ₂ ) improve chemical stability but corrode aluminum current collectors above 3.7 V, motivating the development of non‐corrosive alternatives. Herein, we report a non‐corrosive methide‐based lithium salt, lithium bis(trifluoromethanesulfonyl)methide (LiCTf ₂ ), in which the central nitrogen of LiNTf ₂ is replaced by a methine (─CH─) moiety, modulating the electronic structure of the CTf ₂ ⁻ anion to promote the formation of low‐solubility Al ³⁺ complexes and thus suppress corrosion, while enhancing coordination with Li ⁺ to reinforce solvation structures and establish denser interphase. This design realizes interfacial stabilization, as evidenced by electrochemical and microscopic characterization. Consequently, LiNi _0.5 Mn _0.3 Co _0.2 O ₂ (NMC532) and LiNi _0.8 Mn _0.1 Co _0.1 O ₂ (NMC811) cycled in LiCTf ₂ ‐based electrolyte exhibit enhanced cycling stability compared with LiNTf ₂ and LiPF ₆ . Notably, the excellent performance of LiCTf ₂ is achieved without any film‐forming additives, highlighting its intrinsic interfacial engineering capability. These results provide valuable insights into optimizing electrolyte formulation, offering a promising approach to enhancing the electrochemical stability and cycling performance of NMC cathodes and beyond.