Ni-Rich Cathode Precursor With Co-Mn Surface Gradient Stability

The patent applies local quality by creating a concentration gradient where the nickel content varies spatially within the particle - high nickel content in the inner region for capacity and lower nickel content in the outer region for stability. This is achieved by controlling the precipitation process to form a core-shell like structure during the co-precipitation reaction, where the composition is not uniform but optimized locally for different functions.

The patent creates a composite structure within the positive electrode active material by combining regions with different nickel concentrations and incorporating multiple metal elements (Ni, Co, Mn, Al) in a controlled distribution. This composite approach allows the material to simultaneously exhibit high capacity characteristics from the nickel-rich core and high stability characteristics from the nickel-poor shell, resolving the contradiction between capacity and stability.

The patent uses local quality to address thermal stability by concentrating the nickel content in the inner region while maintaining a nickel-poor outer shell. This spatial distribution ensures that the bulk material provides high capacity while the surface region, which is more exposed to thermal and chemical environments, provides enhanced stability and reduced reactivity, thereby improving thermal stability without sacrificing capacity.

The patent converts the potential harm of high nickel content (which causes poor thermal stability) into a benefit by strategically distributing the nickel. The high nickel content in the core provides capacity, while the controlled lower nickel content at the surface, achieved through the concentration gradient, prevents thermal degradation. Thus, the same nickel content that could be harmful is transformed into a beneficial configuration that simultaneously provides capacity and thermal stability.

The patent resolves this contradiction by optimizing the local quality distribution - the concentration gradient is designed such that the inner region has high nickel content (0.7-0.95) to maximize capacity, while the outer region has lower nickel content (0.5-0.8) to maintain stability. This controlled spatial variation allows the overall nickel content to be high enough for high capacity while maintaining structural stability through the gradient structure, unlike uniform distribution which would require compromising either stability or overall nickel content.

The patent uses parameter changes by precisely controlling the nickel concentration as a function of position within the particle. The concentration gradient is achieved by adjusting precipitation conditions, pH, and addition rates during synthesis, creating a continuous or stepped variation in nickel content from core to shell. This parameter optimization allows maximizing the integral of nickel content (for capacity) while maintaining the stabilizing effect of the gradient structure.

The patent merges the mixing of multiple metal solutions into a single co-precipitation process. Instead of separately preparing and mixing first and second metal solutions, the invention uses a unified precipitation reaction where all metal ions (Ni, Co, Mn, Al) are simultaneously precipitated from a combined solution by controlling pH and precipitation conditions. This integration simplifies the process while maintaining the ability to control nickel content distribution through the precipitation kinetics and local pH gradients that naturally form during the unified process.

The patent applies self-service by allowing the system to automatically create the concentration gradient through the precipitation process itself. By controlling the overall pH and precipitation conditions, the system self-organizes into a concentration gradient structure without requiring complex external mixing or multiple separate solution preparations. The precipitation kinetics and diffusion processes naturally create the desired nickel distribution, reducing process complexity while achieving precise compositional control.