Nickel-Rich Cathode Particle Structure for Output and Cycle-Life
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Solution Overview
Problem
Rechargeable lithium batteries using lithium nickel-based composite oxides face challenges in achieving high capacity, long cycle-life, and high output due to the increased surface area of smaller primary particles leading to undesirable reactions with the electrolyte, which deteriorate stability and cycle-life.
Innovation Solution
A positive electrode active material is developed with secondary particles composed of primary particles agglomerated to specific size and aspect ratio ranges, controlled through electron backscatter diffraction analysis, and prepared by mixing nickel-based composite oxide with lithium raw materials and heat-treatment, enhancing uniformity and sphericity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If smaller primary particles are used, then charge/discharge efficiency and output characteristics are improved, but surface area increases leading to undesirable reactions with electrolyte and deteriorated stability and cycle-life
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core maintains small particle size for high charge/discharge efficiency while the shell provides protective properties. The secondary particles are formed by agglomerating multiple primary particles, creating a hierarchical structure with different functional zones that simultaneously achieve high productivity and reliability.
Solution Approach 2:
The patent implements the nested doll principle through its hierarchical particle structure. Primary particles (first level) are agglomerated to form secondary particles (second level), creating a nested arrangement where smaller functional units are contained within larger structural units. This nested structure allows the inner primary particles to maintain small size for efficiency while the outer secondary particle structure provides stability and reduced electrolyte exposure.
2Reliability
If coated particles or single crystals with enlarged particle sizes are applied, then stability and cycle-life are improved, but high output characteristics are limited
Solution Approach 1:
The patent applies segmentation by dividing the particle structure into distinct primary particles that are agglomerated to form secondary particles. This segmentation allows each primary particle to maintain small size for high output characteristics while the collective secondary particle structure provides the stability and cycle-life improvements associated with larger particle sizes. The segmented structure reconciles the conflicting requirements of small and large particle sizes.
Solution Approach 2:
The patent transitions from considering only primary particle size to a hierarchical two-level structure (primary particles within secondary particles). This dimensional change in the particle size hierarchy allows simultaneous optimization of both output characteristics (through small primary particles) and cycle-life (through larger secondary particle structures), resolving the contradiction between these two performance parameters.
3Speed
If primary particle size is reduced to improve charge/discharge efficiency, then output characteristics improve, but surface area available for undesirable reactions with electrolyte increases
Solution Approach 1:
The patent merges multiple primary particles together to form secondary particles. This combining approach maintains the high charge/discharge rate benefits of small primary particles while reducing the total surface area exposed to the electrolyte by consolidating them into larger secondary particle structures. The merging of particles resolves the contradiction between speed and harmful surface reactions.
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 provides a positive electrode active material that ensures high capacity, long cycle-life, and high output by maintaining uniform primary particle sizes and aspect ratios, improving charge/discharge efficiency and stability.
Implementation Method 1
performing a heat-treatment (to the mixture) to obtain the positive electrode active material
Data Source
AI summary
A positive electrode active material, a preparation method thereof, a positive electrode including the same, and a rechargeable lithium battery are disclosed. The positive electrode active material includes a positive electrode active material including a lithium nickel-based composite oxide and having a secondary particle form in which a plurality of primary particles are agglomerated, wherein an average size of the primary particles measured through electron backscatter diffraction (EBSD) analysis of a cross-section of the secondary particles is about 1.05 μm to about 1.5 μm, a standard deviation of the size of the primary particles is less than or equal to about 0.3 μm, and an average aspect ratio of the primary particles is less than or equal to about 1.7.