Positive Electrode Particle Distribution for Lower Capacity Loss
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Solution Overview
Problem
Lithium secondary batteries face issues with high irreversible capacity loss and degradation due to the use of silicon-based negative electrode materials, leading to reduced capacity and life characteristics, while conventional sacrificial positive electrode materials cause lithium byproduct generation and increased resistance.
Innovation Solution
A positive electrode with a bimodal particle size distribution of single-crystalline lithium transition metal oxides, where the first active material has a larger average particle diameter than the second, and controlled interfacial resistance, minimizing lithium ion loss and byproduct generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based negative electrode materials are used to increase capacity, then energy density is improved, but irreversible capacity loss increases
Solution Approach 1:
The patent changes the particle size parameters of the positive electrode active material, specifically using a D50 of 6-12 μm with a narrow size distribution (D90-D10 ≤ 6 μm). This parameter optimization balances the electrochemical reaction efficiency and reduces irreversible capacity loss when paired with silicon-based negative electrodes, thereby maintaining energy density while minimizing capacity loss.
2Reliability
If conventional sacrificial positive electrode materials are used to compensate for negative electrode loss, then capacity characteristics are improved, but resistance increases and lithium byproducts are generated
Solution Approach 1:
The patent optimizes the particle size parameters of the positive electrode active material (D50: 6-12 μm, D90-D10 ≤ 6 μm) to achieve balanced electrochemical performance. This parameter control enables the positive electrode to maintain good capacity characteristics without requiring excessive sacrificial materials, thereby reducing lithium byproduct generation and resistance increase.
3Object-generated harmful factors
If positive electrode material with larger particle size is used to reduce surface area, then lithium byproduct generation is reduced, but interface resistance increases
Solution Approach 1:
The patent identifies and controls critical particle size parameters: D50 of 6-12 μm and D90-D10 ≤ 6 μm. This optimized parameter range reduces the specific surface area to minimize lithium byproduct generation while maintaining interface resistance within acceptable limits, achieving a balance between harmful factor reduction and performance maintenance.
Solution Approach 2:
The patent uses a composite structure consisting of the positive electrode active material with controlled particle size distribution, combined with conventional negative electrodes. This composite electrode system achieves reduced lithium byproduct generation through optimized particle size while maintaining good interface resistance and electrochemical performance.
Data Source
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-crystalline 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 about 6.5Ω to 8.5Ω, 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 about 15Ω to 19Ω.