Bimodal Positive Electrode Composition for Lower Irreversible Capacity Loss
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Solution Overview
Problem
Existing lithium-based oxides are expensive, and generate a large amount of lithium by-products, which increase the amount of gas generated, and silicon-based negative electrode materials have low charge and discharge efficiency, leading to high lithium ion loss and rapid capacity reduction.
Innovation Solution
A positive electrode with a bimodal particle size distribution, using a first lithium transition metal oxide with a larger average particle diameter and a second lithium transition metal oxide with a smaller average particle diameter, both with single-particle type particles, and controlled interfacial resistance, to improve capacity and high-temperature life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode material is used to increase capacity, then energy density is improved, but irreversible capacity loss increases during initial charge and discharge
Solution Approach 1:
The patent changes the particle size parameters of the positive electrode active material, specifically using a D50 of 6.0 μm or more, to optimize the electrochemical performance and reduce irreversible capacity loss while maintaining high energy density with silicon-based negative electrode material
Solution Approach 2:
The patent applies local quality by creating a specific particle size distribution in the positive electrode active material, where the D50 is controlled at 6.0 μm or more, to locally optimize the interface characteristics and reduce capacity loss in specific regions of the electrode
2Quantity of substance
If lithium-based oxide is used as positive electrode material, then capacity is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the particle size parameter (D50 ≥ 6.0 μm) of the lithium-based oxide to optimize both capacity performance and manufacturing feasibility, reducing the need for expensive fine particle processing while maintaining high capacity
3Quantity of substance
If lithium-based oxide is used as positive electrode material, then capacity is improved, but gas generation increases due to lithium by-products
Solution Approach 1:
The patent changes the particle size parameter (D50 ≥ 6.0 μm) to reduce the surface area-to-volume ratio, thereby reducing the formation of lithium by-products and subsequent gas generation while maintaining high capacity
4Reliability
If single-particle type particles are used with controlled interfacial resistance, then resistance characteristics are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a concrete particle size parameter (D50 ≥ 6.0 μm) that balances resistance characteristics improvement with manufacturability, providing a clear target for production while achieving the desired interfacial resistance performance
Data Source
Figure 1
AI summary
A positive electrode includes a positive electrode active material layer including a first positive electrode active material and a second positive electrode active material having different average particle diameters from each other. An average particle diameter D50 of the first positive electrode active material is larger than an average particle diameter D50 of the second positive electrode active material, the first positive electrode active material and the second positive electrode active material include single-particle type particles, and an interface resistance of the positive electrode having an SOC of 50% measured in a coin half-cell manufactured using the positive electrode is 6.5 Ω to 8.5 Ω, and an interface resistance of the positive electrode having an SOC of 10% measured in a coin half-cell manufactured using the positive electrode is 15 Ω to 19 Ω.