Cathode Active Material Manganese Gradient Thermal Stability

The patent applies local quality by creating a concentration gradient of manganese oxide within the cathode active material particles, where the concentration varies from the center to the surface. This gradient structure allows different regions of the same material to have different compositions - the manganese-rich surface layer provides thermal stability and structural protection during over-charging, while the manganese-poor core maintains high energy density and electrochemical performance. This resolves the contradiction by optimizing different regions for different functions.

The patent creates a composite cathode active material by combining lithium nickel oxide with manganese oxide in a concentration gradient distribution. The resulting material Li1+aNixCo1-x-yMnyM1bO2 integrates the high energy density characteristics of nickel-based materials with the thermal stability of manganese-based materials. The composite structure with controlled composition gradient simultaneously achieves both high energy density and improved thermal stability, preventing the rapid structural changes and oxygen emission that occur in pure nickel-based materials during over-charging.

The patent uses local quality by concentrating manganese oxide at the surface regions of the cathode particles while maintaining a nickel-rich composition in the core. The manganese-rich surface layer specifically addresses thermal stability concerns, while the nickel-rich core preserves excellent charge/discharge characteristics. This spatial differentiation allows the material to simultaneously achieve good electrochemical performance and thermal stability without requiring complete nickel replacement.

The patent creates a composite material system where cobalt and manganese work synergistically. Cobalt provides enhanced charge/discharge characteristics and structural stability, while manganese contributes thermal stability. The concentration gradient distribution optimizes the contribution of each element - cobalt and manganese at the surface for stability, and nickel in the core for energy density and electrochemical activity. This composite approach resolves the contradiction between performance and thermal stability.

The patent applies preliminary action by incorporating the protective manganese oxide layer directly into the bulk structure of the cathode active material during synthesis, rather than applying it as a separate coating step afterward. The concentration gradient is established during the formation process, creating an intrinsic protective structure that is integral to the material itself. This preliminary incorporation ensures the protective layer is uniformly distributed and firmly bonded throughout the particle structure, preventing the delamination and degradation that occur with post-synthesis coatings over long cycling periods.

The patent creates an integrated composite material where the protective manganese oxide component is synthesized together with the lithium nickel cobalt oxide core, forming a concentration gradient structure. This integrated composite approach ensures uniform distribution and strong bonding between the protective layer and the active material core, eliminating the interface adhesion problems that plague separate coating approaches. The resulting material maintains its protective function consistently over hundreds of cycles.

The patent applies preliminary action by establishing the desired concentration gradient during the synthesis process itself, before any heat treatment occurs. The controlled composition gradient is formed during the sol-gel or co-precipitation synthesis, where manganese oxide is selectively concentrated at the particle surfaces through controlled precipitation or surface reaction. By achieving the gradient structure during synthesis rather than through subsequent high-temperature heat treatment, the patent avoids the thermal diffusion that would otherwise homogenize the composition and eliminate the protective gradient structure.

The patent applies parameter changes by carefully controlling synthesis parameters such as pH, temperature, and precursor ratios during the formation process to achieve selective manganese oxide precipitation at the particle surfaces. By adjusting these parameters during synthesis rather than relying on high-temperature heat treatment, the patent creates the concentration gradient under milder conditions that preserve compositional precision. This approach achieves surface enrichment of manganese oxide without the thermal diffusion that would occur at high temperatures and reduce the gradient sharpness.