Core-Shell Cathode Material Cobalt Content Optimization
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Solution Overview
Problem
Lithium secondary batteries face challenges with cathode active materials having unstable internal structures due to discontinuous metal composition changes, leading to reduced efficiency and poor performance in terms of capacity, stability, and high-temperature characteristics.
Innovation Solution
A cathode active material with a core-shell structure is developed, where the total cobalt content in the core and shell portions is adjusted to a range of 5 to 12 mol%, with the cobalt content in the shell portion being 0.2 to 1.0 times the total cobalt content, to enhance stability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a core-shell structure with high nickel content in the core and low nickel content in the shell is adopted, then capacity and charge/discharge efficiency are improved, but the internal structure becomes unstable due to discontinuous metal composition changes
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core portion contains high nickel content (0.5-0.8 mol fraction) for high capacity, while the shell portion contains low nickel content (0.1-0.3 mol fraction) for structural stability. This spatial differentiation of composition allows each region to fulfill its specific function optimally.
Solution Approach 2:
The patent utilizes parameter changes by precisely controlling the cobalt content in both core and shell portions within specific ranges (core: 0.1-0.3 mol fraction, shell: 0.05-0.15 mol fraction), and adjusting the total cobalt content to 5-12 mol%. This continuous parameter optimization resolves the discontinuous composition problem and stabilizes the internal structure.
2Quantity of substance
If LiNiO2 is used as the cathode active material, then high discharge capacity is achieved, but thermal stability and cycle characteristics are poor
Solution Approach 1:
The patent employs composite materials by combining lithium nickel oxide (providing high capacity) with lithium cobalt oxide (providing thermal stability and structural integrity) in a core-shell configuration. The composite structure synergistically integrates the advantages of both materials while mitigating their individual disadvantages.
3Reliability
If LiMn2O4 is used as the cathode active material, then thermal stability and low price are achieved, but capacity and temperature characteristics are low
Solution Approach 1:
The patent applies local quality by placing high nickel content material in the core portion where high capacity is needed, while using low nickel content material in the shell portion where thermal stability is prioritized. This spatial differentiation allows the material to simultaneously achieve high capacity and thermal stability in different regions.
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AI summary
The present invention relates to a cathode active material for a lithium secondary battery, and more particularly, to a cathode active material for a lithium secondary battery, which includes a core portion and a shell portion surrounding the core portion, in which a total content of cobalt in the core portion and the shell portion is 5 to 12 mol%, and the content of cobalt in the core portion and the shell portion is adjusted to be within a predetermined range. In the cathode active material precursor and the cathode active material for a secondary battery prepared using the same according to the present invention, optimal capacity of a lithium secondary battery may be increased by adjusting the cobalt content in the particles of the cathode active material, and life characteristics may be enhanced by improving stability.