Layered Cathode Particle Structure for High-Output Li-Ion Electrodes
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Solution Overview
Problem
Existing nonaqueous electrolyte secondary batteries with positive electrode active materials face challenges in maintaining high output characteristics due to cracking and increased resistance, especially when secondary particles collapse during press molding and form new surfaces, leading to reduced void diameters and poor electrolyte distribution.
Innovation Solution
The use of a positive electrode active material with a layered structure composed of two or more transition metals, having an average particle diameter of 1 to 7 µm, a specific particle size distribution, and a void fraction of 10 to 45%, which includes Ni, Mn, or Al as main components, ensures that the material remains intact and maintains efficient lithium ion diffusion paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If secondary particles are used to increase density, then electrode density is improved, but cracks are generated during press molding and charge-discharge cycles, reducing output characteristics
Solution Approach 1:
The positive electrode active material is divided into multiple primary particles (0.1 to 1 µm) that aggregate to form secondary particles with controlled void fractions (30-50%). This segmentation allows the electrode to maintain high density while the void spaces prevent crack propagation during press molding and charge-discharge cycles, resolving the contradiction between density and crack resistance.
2Volume of stationary object
If void fraction is decreased to increase density, then electrode density is improved, but pore diameter is reduced, increasing resistance and reducing output characteristics
Solution Approach 1:
The electrode structure is designed with heterogeneous void distribution: void fractions of 30-50% are maintained specifically within the secondary particles, while the overall electrode density is optimized. This local quality approach ensures sufficient pore diameter (0.09 to 0.30 µm) for low resistance and high output characteristics, while achieving high overall density through the secondary particle structure.
3Volume of stationary object
If press molding pressure is increased to improve electrode density, then electrode density is improved, but cracks are generated in the positive electrode active material, reducing durability
Solution Approach 1:
The secondary particle structure with 30-50% void fraction acts as a cushioning mechanism before press molding. The void spaces absorb and distribute the stress from press molding pressure, preventing crack generation in the positive electrode active material. This beforehand cushioning allows high electrode density to be achieved while maintaining durability during charge-discharge cycles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the output characteristics by preventing cracking and maintaining high density, ensuring efficient lithium ion diffusion and reducing resistance, thereby achieving higher energy density and durability in nonaqueous electrolyte secondary batteries.
Implementation Method 1
maintains efficient lithium ion diffusion paths
Data Source
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AI summary
The present invention provides an electrode for nonaqueous electrolyte secondary batteries, which enables the achievement of high output characteristics. An electrode for nonaqueous electrolyte secondary batteries, which is provided with a collector and a positive electrode active material layer that is arranged on the collector and contains a positive electrode active material. The positive electrode active material is configured to contain compound particles which have a layered structure composed of two or more transition metals, and which have an average particle diameter DSEM of from 1 µm to 7 µm (inclusive) based on the observation with an electron microscope, a ratio of the 50% particle diameter D50 in a volume-based cumulative particle size distribution to the average particle diameter DSEM, namely D50/DSEM of from 1 to 4 (inclusive), and a ratio of the 90% particle diameter D90 in the volume-based cumulative particle size distribution to the 10% particle diameter D10 in the volume-based cumulative particle size distribution, namely D90/D10 of 4 or less. The positive electrode active material layer has a void fraction of 10-45%.