Nickel-Rich Cathode Material with Cobalt Gradient for Longer Cycle Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face issues with reduced output characteristics and lifespan due to side reactions between the cathode active material and electrolyte, necessitating improved stability and efficiency.
Innovation Solution
A cathode active material comprising lithium transition metal oxide particles with a high nickel content and a cobalt concentration gradient, where the cobalt content varies radially, minimizing lattice structure deformation and reducing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content cathode active material is used to increase capacity, then energy density is improved, but structural stability deteriorates and side reactions with electrolyte increase
Solution Approach 1:
The patent applies local quality by creating a cobalt concentration gradient within the cathode active material particles, where the cobalt content varies from the center to the surface. This gradient structure allows different regions of the material to have different compositions optimized for their specific functions: the core region maintains high nickel content for capacity while the surface region has higher cobalt content for stability, thus resolving the contradiction between energy density and structural stability.
2Quantity of substance
If high nickel content cathode active material is used to increase capacity, then energy density is improved, but lifespan decreases due to side reactions with electrolyte
Solution Approach 1:
The patent implements local quality through a cobalt concentration gradient where the surface portion of the particles has higher cobalt content (5-15 mol%) compared to the center (1-10 mol%). This surface enrichment with cobalt reduces side reactions with the electrolyte, thereby extending battery lifespan while maintaining high energy density through the nickel-rich core.
3Ease of manufacture
If uniform cobalt content is used in cathode active material, then manufacturing is simplified, but structural stability during charge-discharge deteriorates
Solution Approach 1:
The patent applies parameter changes by intentionally varying the cobalt content parameter throughout the particle radius, creating a gradient distribution rather than a uniform composition. This parameter variation (cobalt concentration increasing from center to surface) optimizes structural stability during charge-discharge cycles while the gradient itself can be controlled through manufacturing parameters like calcination conditions.
Data Source
Figure 1~2
Figure 3
AI summary
According to the present disclosure, there is provided a cathode active material for a secondary battery, which includes lithium transition metal oxide particles containing nickel in a content of 80 mol% or more, based on a total number of moles of elements excluding lithium and oxygen, and cobalt. An average content of cobalt in a surface portion of the particle, based on the total number of moles of elements excluding lithium and oxygen is higher than an average content of cobalt in a central portion of the particle, based on the total number of moles of elements excluding lithium and oxygen. The lithium transition metal oxide particle satisfies Equation 1-1 below. 0.2<S1−S2<1.15 In Equation 1-1 and Equation 1-2, S1 is an average slope of cobalt content in a region from the center of the particle to a point located 25% of the radius of the particle toward the surface. S2 is the average slope of cobalt content in a region from the surface of the particle to a point located 25% of the radius of the particle toward the center.