Bimodal Cathode Material with Cobalt Gradient for Particle Stability
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Solution Overview
Problem
Existing lithium secondary batteries face issues with particle stability and volume changes in bimodal-type positive electrode active materials due to uneven cobalt distribution, leading to structural instability and reduced energy density.
Innovation Solution
A bimodal-type positive electrode active material with a controlled concentration gradient of cobalt decreasing from the surface to the central portion in both small and large particles, ensuring uniform particle stability and minimizing stress during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a bimodal-type positive electrode active material with small particles and large particles is used to increase energy density, then the integration density and capacity are improved, but the particle stability deteriorates due to volume changes and stress accumulation during charging and discharging
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of cobalt within the particles, where the cobalt content varies from the surface to the center. This non-uniform distribution allows different regions of the particle to have different properties: the surface region has higher cobalt content for stability, while the inner region has lower cobalt content for capacity, thus resolving the contradiction between particle stability and energy density
Solution Approach 2:
The patent changes the concentration parameter of cobalt within the particle structure, creating a gradient distribution rather than uniform distribution. This parameter change allows the material to simultaneously achieve structural stability at the surface and high capacity in the interior, addressing both particle stability and energy density requirements
2Ease of manufacture
If the cobalt concentration is uniformly distributed in the positive electrode active material, then the synthesis process is simple, but the particle stability deteriorates due to stress accumulation during lithium ion intercalation and deintercalation
Solution Approach 1:
The patent implements local quality by establishing a cobalt concentration gradient where the surface portion has higher cobalt content and the central portion has lower cobalt content. This local variation in composition enhances particle stability during charging and discharging cycles while maintaining a relatively simple synthesis process through controlled coprecipitation and heat treatment
3Quantity of substance
If the cobalt content is increased in the positive electrode active material to improve capacity, then the energy density is improved, but the particle stability worsens due to volume expansion and structural degradation
Solution Approach 1:
The patent applies local quality by distributing cobalt non-uniformly within the particle structure, with higher concentration at the surface and lower concentration in the center. This allows the material to achieve high capacity through sufficient overall cobalt content while maintaining particle stability through higher cobalt concentration at the surface that resists volume expansion and structural degradation
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 controlled cobalt gradient improves the integration density and stability of the particles, enhancing the energy density and reducing structural damage, thereby stabilizing the battery performance.
Implementation Method 1
controlling a slope of a concentration gradient in which cobalt in the small particle and the large particle decreases from a surface portion toward a central portion
Data Source
AI summary
The present invention relates to a positive electrode active material and a lithium secondary battery including the same, and more particularly, to a bimodal-type positive electrode active material including a first lithium composite oxide as a small particle and a second lithium composite oxide as a large particle, wherein the positive electrode active material may uniformly improve the particle stability of the small particle and the large particle by controlling a slope of a concentration gradient in which cobalt in the small particle and the large particle decreases from a surface portion toward a central portion, a positive electrode including the positive electrode active material, and a lithium secondary battery using the positive electrode.