How does a surface coating dictate bulk structural evolution in spinel cathodes?

Surface coating materials are widely utilized across diverse sectors, including aerospace, medical technology, packaging, and construction, owing to their exceptional properties, such as self-healing, corrosion resistance, and protection against external factors and they are also extensively applied in the field of battery materials. Here, we focus on spinel-type LiMn₂O₄ (LMO) and construct a nanoscale LiNbO₃ surface coating using a precipitation–high-temperature solid-state method. This approach leverages the benefits of both surface-coating and bulk doping techniques by shielding the bulk lithium manganate from electrolyte corrosion, while maintaining ion and charge transport channels on the surface through a fast-ion conductor layer. Additionally, it exerts an effect on the bulk crystal structure of LMO induced by the compressive stress from the robust Nb–O bond near the surface, reinforcing the structural integrity of the MnO₆ octahedral framework and mitigating lattice distortion during repeated cycling. As a consequence, the surface-coated lithium manganate exhibits improved electrochemical performance, delivering an initial capacity of 117 mAh g⁻¹ and retaining 92.31% of this capacity after 300 cycles at 1 C. Even at 10 C, the material maintains a high capacity of 95 mAh g⁻¹. This study underscores the utmost role of the LiNbO₃ surface layer on LMO, which can serve as a promising strategy to enhance the cycling performance of lithium-ion batteries.