Highly-dispersed high-entropy oxide nanoparticles prepared by flame spray pyrolysis as a coating for enhancing the electrochemical stability of layered lithium-ion battery cathodes

Layered oxide cathode materials, such as LiNi 0.83 Co 0.12 Mn 0.05 O 2 (NCM83), often suffer from structural degradation during electrochemical cycling, which leads to capacity fading. Although conventional surface coatings can improve stability, they frequently impede Li + transport over prolonged cycling, reducing rate capability. High-entropy oxides, with their characteristic low Gibbs Free Energy and excellent thermal/structural stability, present a novel strategy for performance enhancement in layered cathode. However, constructing a high-entropy oxide coating on electrode presents challenges, including compositional segregation and inhomogeneity. In this work, we introduce Flame Spray Pyrolysis (FSP) to synthesize homogeneous, highly dispersed (NiMnTiMoCr) 3 O 4 (HEO) nanoparticles with a narrow size distribution. This approach can prevent the destruction of the high-entropy crystal structure and ensure elemental homogeneity; combined with dry ball-milling and solid-state sintering, it facilitated the rapid formation of a dense, nanoscale HEO coating on NCM83. The high-entropy HEO coating synergistically improves electrochemical performance by enhancing Li + kinetics, suppressing the H2-H3 phase transition, and stabilizing the interface. The HEO-coated cathode delivered an initial discharge capacity of 211.4 mAh/g and outstanding long-term stability of 95.66% (0.5C, 100 cycles), compared to 90.05% for NCM83. Post-cycling morphology and spectral analysis further revealed how the HEO coating preserves the cathode's structural integrity. This study not only provides a novel synthetic route for high-entropy oxides but also enables efficient, controllable synthesis of HEO nanoparticles with high scalability potential. It substantiates the promise of the high-entropy coating strategy for enabling the rational design of future high-performance cathodes.