Positive Electrode Active Material for High Volume Capacity Density
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries, such as lithium ion batteries, face challenges in achieving high volume capacity density and cycle characteristics due to the insufficient performance of conventional positive electrode active materials.
Innovation Solution
A positive electrode active material comprising monoparticulate and secondary particulate lithium composite oxide particles, where the secondary particles have a larger average size and porosity of 0.9% to 4.0%, and a specific composition of lithium nickel cobalt manganese oxide with a layered structure, enhancing filling properties and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If monoparticulate and secondary particulate lithium composite oxide are used in combination, then volume capacity density is improved, but cycle characteristics deteriorate
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the secondary particulate lithium composite oxide has a specific porosity distribution (0.9% to 4.0%) and the monoparticulate lithium composite oxide forms a dense core. This localized structural differentiation allows the outer porous structure to accommodate volume changes during cycling (improving cycle characteristics) while the inner dense structure provides high capacity (improving volume capacity density).
Solution Approach 2:
The patent uses composite materials by combining two distinct lithium composite oxide particle types with different properties: monoparticulate particles (high density, high capacity) and secondary particulate particles (controlled porosity, good structural stability). This composite approach allows the positive electrode to simultaneously achieve high volume capacity density from the monoparticulate component and high cycle characteristics from the secondary particulate component with optimized porosity.
2Volume of moving object
If secondary particulate lithium composite oxide with larger particle size is used, then filling property is improved, but porosity control becomes more difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling the porosity parameter of secondary particulate lithium composite oxide within a specific range (0.9% to 4.0%). This parameter optimization allows larger particle sizes (12 μm to 20 μm) to maintain both good filling property and adequate porosity for ion transport, resolving the trade-off between particle size and porosity control.
3Power
If monoparticulate lithium composite oxide with smaller particle size is used, then output characteristics are improved, but filling property deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the positive electrode active material into two distinct particle size segments: monoparticulate lithium composite oxide (2 μm to 6 μm) for high output characteristics and secondary particulate lithium composite oxide (12 μm to 20 μm) for good filling property. This segmentation allows each particle type to optimize its function while contributing to the overall electrode performance.
Data Source
AI summary
Provided is a positive electrode active material that can increase a volume capacity density of a positive electrode of a nonaqueous battery secondary battery and can provide the nonaqueous electrolyte secondary battery with high cycle characteristics. A positive electrode active material disclosed here includes monoparticulate first lithium composite oxide particles and secondary particulate second lithium composite oxide particles. An average particle size of the second lithium composite oxide particles is larger than an average particle size of the first lithium composite oxide particles. The second lithium composite oxide particles have a porosity of 0.9% to 4.0%.