Bimodal Cathode Active Material for Ion-Conductive Li-Ion Batteries
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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 lithium composite oxide particles with different average particle diameters. The first particles include yttrium and zirconium on their surface, while the second particles have a distinct yttrium composition. This bimodal particle structure enhances ion conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a bimodal-type positive electrode active material including a mixture of small particles and large particles is used to achieve high capacity, then the energy density increases, but the ion conductivity and stability deteriorate
Solution Approach 1:
The patent applies local quality by creating a bimodal particle size distribution where small particles (first particles) with high ion conductivity are concentrated at the surface region, while large particles (second particles) provide bulk capacity. The surface enrichment of small particles with diameter of 1 μm or less ensures high ion conductivity at the electrode-electrolyte interface, while the inner region contains large particles for high energy density.
Solution Approach 2:
The positive electrode active material is segmented into two distinct particle populations: first particles with diameter of 0.1 μm to 1 μm that enrich at the surface, and second particles with diameter of 1 μm to 10 μm that form the bulk structure. This segmentation allows each particle size to fulfill its specific function - small particles for conductivity and large particles for capacity.
2Quantity of substance
If a bimodal-type positive electrode active material including a mixture of small particles and large particles is used to achieve high capacity, then the energy density increases, but the stability deteriorates
Solution Approach 1:
The surface region of the positive electrode active material is engineered to have high concentration of small particles (first particles) with diameter of 1 μm or less, creating a stable surface layer that resists degradation. The bulk region contains large particles (second particles) that provide energy density. This spatial differentiation of particle sizes enhances overall stability while maintaining high capacity.
3Reliability
If small particles are used to improve ion conductivity, then the ion conductivity increases, but the energy density decreases
Solution Approach 1:
The patent transitions from a single-dimensional particle size approach to a two-dimensional distribution strategy. The small particles (first particles) are strategically positioned in the size dimension (0.1-1 μm) for high ion conductivity, while large particles (second particles) occupy the larger size dimension (1-10 μm) for high energy density. The surface enrichment of small particles creates a conductivity-enhanced surface layer without sacrificing bulk capacity from large particles.
Data Source
AI summary
A rechargeable lithium battery may include 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) is 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.