Positive Electrode Active Material Surface Gradient

The patent resolves this contradiction by applying stabilization additives locally only in the surface region of the active material particles, specifically within 10 nm from the surface. This localized approach ensures that the bulk material maintains its high-capacity composition with optimal nickel content, while only the surface region receives the stabilizing calcium and fluorine elements. As a result, the discharge capacity is preserved because the high-capacity bulk material remains unchanged, while cycle performance improves due to the stabilized surface that resists degradation during cycling.

The patent applies local quality by creating a non-uniform distribution of calcium and fluorine additive elements within the positive electrode active material particles. The additive elements are concentrated in the surface region (within 10 nm from the surface) rather than being uniformly distributed throughout the particle. This localized modification provides targeted surface protection where degradation occurs most, while maintaining optimal bulk composition for high capacity.

The patent applies parameter changes by optimizing the heat treatment temperature range (500-900°C) and time duration (2-20 hours) to achieve the desired concentration gradient distribution of calcium and fluorine additives. By controlling these thermal parameters, the patent enables precise element distribution where additives concentrate in the surface region during heating, without requiring complex multi-step manufacturing processes. This approach achieves high manufacturing precision through simple parameter optimization rather than process complexity.