Nickel-Rich Cathode Material with Internal Doping and Surface Coating
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Solution Overview
Problem
Current nickel-rich ternary cathode materials face challenges in achieving high rate capability and thermal stability due to increased nickel content, with existing modification methods like doping and coating being complex and costly.
Innovation Solution
A cathode material with the chemical formula Li b Ni 1-x-y Co x Al y M z O 2, where the M element is distributed both internally and superficially, with a molar ratio greater than 0.5, enhancing both doping and coating effects in a single, simplified process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coating modification is applied to improve rate capability and thermal stability, then thermal stability is improved, but process complexity increases due to additional coating accessories, mixing and heat treatment processes
Solution Approach 1:
The patent combines doping and coating modifications into a single integrated process. The M compound is added to the precursor mixture before sintering, allowing simultaneous doping (internal) and coating (surface) effects to be achieved in one step, eliminating the need for separate coating processes and their associated complexity
Solution Approach 2:
The M compound serves dual functions: it acts as a dopant when incorporated into the bulk material structure and as a coating material on the surface. This multi-functionality allows a single additive to address both internal structural stability and surface protection needs
2Reliability
If doping modification is applied in precursor preparation to improve rate capability, then rate capability is improved, but process complexity of precursor preparation increases
Solution Approach 1:
The patent merges doping and coating operations into a single precursor preparation step. By adding the M compound to the precursor mixture along with other cathode material precursors, both doping and coating effects are achieved simultaneously during one sintering process, avoiding separate doping and coating steps
3Quantity of substance
If nickel content is increased in nickel-rich ternary materials to improve energy density, then energy density is improved, but thermal stability and rate capability are greatly challenged
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of M element: doping provides internal modification throughout the bulk material to maintain structural stability, while coating provides concentrated surface modification to protect the high-nickel surface from degradation and electrolyte attack, with each region optimized for its specific function
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed cathode material achieves improved rate capability and thermal stability by optimizing the layered structure, suppressing phase changes, and enhancing lithium ion conductivity and diffusion rates, while also simplifying the production process and reducing costs.
Implementation Method 1
doping modification can be implemented in the two procedures, precursor preparation and sintering
Implementation Method 2
coating modification not only requires an additional cost of coating accessories, but also requires additional processes
Implementation Method 3
sintering a mixture containing at least one of Ni1-x-yCoxAly oxide and/or hydroxide, an M compound and a lithium compound
Implementation Method 4
enhancing lithium ion conductivity and diffusion rates
Data Source
Figure 1~2b
Figure 3a~4
Figure 5~6
AI summary
The present application provides a cathode material, a preparation method thereof, and a secondary lithium battery. The cathode material is characterized in that a chemical formula of the cathode material is LibNil-x-yCoxAlyMzO2, where 0.95≤b≤1.10, 0≤x≤0.15, 0.01≤y≤0.1, 0<z≤0.05, and an M element is a metal element; the M element is distributed in interior and surface of the cathode material, the M element distributed in the interior of the cathode material is presented in a doped form, and the M element distributed in the surface of the cathode material is presented in a form of a coating layer formed of at least one of M oxide or lithium-M composite oxide; and a molar ratio of the M element in the interior to the M element in the surface is greater than 0.5. The cathode material provided in the present application has good high-rate capability and thermal stability.