Positive Electrode Active Material With Bimodal Particles for Stable Capacity
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high ion conductivity, stability, and capacity retention due to limitations in existing positive electrode active materials.
Innovation Solution
A positive electrode active material is developed, comprising a mixture of first and second particles with different average particle diameters, where the first particle includes yttrium (Y) and zirconium (Zr) on its surface, and the second particle has a distinct yttrium composition, with a ratio of the first composition to the second composition greater than about 100.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content is used in lithium composite oxide to increase energy density, then capacity is improved, but stability and ion conductivity deteriorate
Solution Approach 1:
The patent applies local quality by creating a bimodal particle size distribution where small particles (first particles) with high nickel content provide high capacity, while large particles (second particles) with lower nickel content provide stability. Each particle size range has optimized nickel content and surface composition, allowing local optimization of properties for different functional requirements within the same electrode material system.
Solution Approach 2:
The patent uses composite materials by combining lithium composite oxides with different nickel contents and particle sizes in a bimodal distribution. The composite structure integrates high-nickel small particles for capacity with lower-nickel large particles for stability, creating a synergistic material system that achieves both high energy density and good stability.
2Reliability
If small particles are used to increase surface area and ion conductivity, then ion conductivity is improved, but stability and capacity retention worsen
Solution Approach 1:
The patent applies segmentation by dividing the electrode material into two distinct particle size segments: small particles (first particles) that provide high surface area and excellent ion conductivity, and large particles (second particles) that provide structural stability and good capacity retention. This segmentation allows each particle size range to fulfill its specific functional role without compromising the other.
3Reliability
If bimodal particle size distribution is used to balance conductivity and stability, then both properties are improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing specific parameters of the bimodal particle system: the particle size ranges (small particles: 0.5-5 μm, large particles: 5-20 μm), the nickel content distribution, and the surface composition with yttrium and zirconium. By carefully controlling these parameters, the patent achieves optimal balance between ion conductivity and stability while making the manufacturing process manageable through defined synthesis conditions.
Data Source
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AI summary
A rechargeable lithium battery includes a positive electrode active material. The positive electrode active material comprises a first particle that includes a first lithium composite oxide and has a first average particle diameter, and a second particle that includes a second lithium composite oxide and has a second average particle diameter greater than the first average particle diameter. The first particle includes yttrium (Y) and zirconium (Zr) on a surface of the first particle. The yttrium (Y) on the surface of the first particle has a first composition. Yttrium (Y) on a surface of the second particle has a second composition. A ratio of the first composition to the second composition is greater than about 100.