Optimized Nickel Aluminate Surface Coating to Enhance the Electrochemical Stability of <scp> LiMn ₂ O ₄ </scp> Cathode Materials for Li‐Ion Batteries

ABSTRACT Spinel lithium‐manganate, known as LiMn 2 O 4 (LMO), is extensively utilized in high‐voltage lithium‐ion batteries (LIBs). Nevertheless, these materials face major issues, including limited cyclability, insufficient capacity retention, and poor rate capability, mainly due to manganese dissolution and structural distortion. This work presents a method to address these challenges by coating LMO cathodes with a thin layer of Ni x Al y O z (NAO) spinel oxide using a scalable sol–gel method, thereby minimizing Mn dissolution and Jahn–Teller distortion. The shape‐controlled truncated octahedron LMO cathodes, featuring a preferred crystal plane orientation that enhances lithium‐ion diffusion, are derived from pre‐synthesized α‐MnO 2 nanostructures. LMO surfaces were coated with NAO at 1%, 2%, and 3% by weight. These modified LMO cathodes exhibit improved cycle stability over 3.0–4.5 V. The LMO cathode with 3% NAO coating maintained 98.8% capacity retention after 500 charge/discharge cycles, versus pristine LMO retaining only 56.88% after 500 cycles at a 1C rate. This performance stems from a dual‐phase design integrating truncated octahedral LMO with an orthorhombic nickel aluminate surface layer at 1–3 wt % loading, providing suppression of Mn dissolution and structural degradation under high‐voltage operation.