High-Nickel Cathode Particle Structure for Crack-Resistant Li-Ion Cells
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Solution Overview
Problem
High nickel positive electrode active materials in lithium secondary batteries face structural degradation due to volume changes during charging and discharging, leading to cracks and reduced conductivity, and existing solutions for secondary particles fail to address the issues of both secondary and single particles effectively, particularly for high nickel materials with excellent capacity characteristics.
Innovation Solution
A positive electrode active material is developed with secondary particles formed by aggregating primary particles of specific size and composition, including a lithium transition metal composite oxide with a high nickel content, which recovers the layered structure from a rock salt structure after high-temperature heat treatment, ensuring excellent crystallinity and density characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high nickel content is used to achieve excellent capacity characteristics, then energy density is improved, but structural degradation and crack formation occur during charge and discharge
Solution Approach 1:
The patent changes the particle size parameter of primary particles to a specific range (1.0-5.0 μm) and controls the nickel content parameter (60-80 mol%) to optimize the balance between energy density and structural stability. By precisely controlling these parameters, the material achieves high capacity while maintaining structural integrity during cycling.
Solution Approach 2:
The patent creates a composite structure where primary particles with specific size and composition are aggregated into secondary particles. This composite approach combines the high energy density of high nickel content with the structural stability provided by controlled particle morphology and size distribution, resolving the contradiction between capacity and reliability.
2Reliability
If secondary particle structure is used to improve rolling density and reduce cracks, then structural stability is improved, but particle diameter distribution increases after grinding
Solution Approach 1:
The patent controls the size parameter of primary particles (1.0-5.0 μm) and the aggregation structure to create secondary particles that maintain narrow diameter distribution even after grinding. This parameter optimization ensures both structural stability and manufacturing precision are achieved simultaneously.
Solution Approach 2:
The patent segments the positive electrode active material into primary particles of controlled size that aggregate into secondary particles. This segmentation allows the material to maintain structural stability while preserving a narrow particle diameter distribution after processing, as the primary particle size is controlled before aggregation.
3Shape
If heat treatment temperature is increased to achieve micron-level primary particle diameter, then rolling density is improved, but layered structure degenerates into rock salt structure
Solution Approach 1:
The patent optimizes the heat treatment temperature parameter to a specific range that achieves micron-level primary particle diameter (1.0-5.0 μm) while preserving the layered structure. By precisely controlling this temperature parameter, the patent avoids the degradation into rock salt structure that occurs at higher temperatures, thus maintaining both rolling density and crystallinity.
4Manufacturing precision
If single particle form is used to reduce particle diameter distribution increase, then manufacturing precision is improved, but specific surface area decreases leading to poor cell resistance characteristics
Solution Approach 1:
The patent segments the material into primary particles (1.0-5.0 μm) that aggregate into secondary particles. This segmentation maintains a narrow particle diameter distribution (improving manufacturing precision) while the aggregation structure preserves sufficient specific surface area (maintaining good cell resistance characteristics), thus resolving the contradiction between these two parameters.
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 solution improves energy density, lifetime, and reduces gas generation in lithium secondary batteries by stabilizing the structure of high nickel positive electrode active materials, addressing both secondary and single particle issues.
Implementation Method 1
it is necessary to perform a heat treatment at a higher temperature than a secondary particle in which a diameter of a primary particle is at a submicron level of less than 1 μm
Implementation Method 2
since a layered structure of lithium transition metal composite oxide is degenerated into a rock salt structure as the heat treatment temperature is increased
Data Source
Figure 1(A)~1(B)
Figure 2(A)~2(B)
Figure 3(A)~3(B)
AI summary
The present invention relates to a positive electrode active material, and to a positive electrode active material which may simultaneously solve a problem of a conventional secondary particle and a problem of a single particle, wherein the positive electrode active material may improve energy density through excellent density characteristics as well as cell characteristics, such as improved lifetime and reduced gas generation amount of a lithium secondary battery, by including a particle, such as a conventional single particles, as a primary particle and including a secondary particle that is formed by aggregation of a plurality of primary particles, and a positive electrode and a lithium secondary battery which include the same.