Silicon Negative Electrode Particle Mix for Density-Stress Balance
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Solution Overview
Problem
Existing negative electrode active materials in electricity storage devices face challenges in achieving a balance between high filling density and avoiding internal stress, as high circularity materials increase density but reduce voids, while low circularity materials provide voids but are prone to cracking, leading to reduced capacity and specific surface area.
Innovation Solution
Incorporating first and second particles with specific circularity and size ratios in the negative electrode active material layer, where the first particles have an average circularity of 0.5 to 0.9 and the second particles exceed 0.9, with a particle diameter ratio of 0.1 to 1, to enhance specific surface area and maintain proper voids, thereby reducing internal stress and capacity retention issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high circularity particles are used to increase filling density, then the negative electrode active material layer achieves high density, but the specific surface area is reduced and internal stress increases
Solution Approach 1:
The negative electrode active material is segmented into two distinct particle types: first particles with moderate circularity (0.5-0.9) providing structural stability and void spaces, and second particles with high circularity (>0.9) providing filling density. This segmentation allows each particle type to fulfill different functional requirements simultaneously.
Solution Approach 2:
Different regions of the negative electrode active material layer have different particle compositions. The first particles with moderate circularity are distributed throughout to provide void spaces and maintain specific surface area, while second particles with high circularity are distributed to increase filling density in specific regions, creating local quality variations that resolve the contradiction.
2Quantity of substance
If high circularity particles are used to increase filling density, then the negative electrode active material layer achieves high density, but internal stress increases leading to capacity reduction
Solution Approach 1:
The negative electrode active material is segmented into two distinct particle types: first particles with moderate circularity (0.5-0.9) providing structural stability and void spaces, and second particles with high circularity (>0.9) providing filling density. This segmentation allows each particle type to fulfill different functional requirements simultaneously.
Solution Approach 2:
The invention changes the parameter distribution of particle circularity by introducing a bimodal distribution with first particles having moderate circularity (0.5-0.9) and second particles having high circularity (>0.9). This parameter change allows the system to achieve high filling density while maintaining capacity retention through the presence of first particles with optimal stress-resistant properties.
3Area of moving object
If low circularity particles are used to provide voids, then the specific surface area is maintained, but the filling density is reduced
Solution Approach 1:
The negative electrode active material is segmented into two distinct particle types: first particles with moderate circularity (0.5-0.9) providing structural stability and void spaces, and second particles with high circularity (>0.9) providing filling density. This segmentation allows each particle type to fulfill different functional requirements simultaneously.
Solution Approach 2:
The invention merges two different particle types with complementary properties into a single negative electrode active material system. The first particles with moderate circularity and the second particles with high circularity are combined in specific ratios to achieve both high specific surface area and high filling density, resolving the contradiction between these two parameters.
4Area of moving object
If low circularity particles are used to provide voids, then the specific surface area is maintained, but the filling density is reduced
Solution Approach 1:
The negative electrode active material is segmented into two distinct particle types: first particles with moderate circularity (0.5-0.9) providing structural stability and void spaces, and second particles with high circularity (>0.9) providing filling density. This segmentation allows each particle type to fulfill different functional requirements simultaneously.
Solution Approach 2:
The invention merges two different particle types with complementary properties into a single negative electrode active material system. The first particles with moderate circularity and the second particles with high circularity are combined in specific ratios to achieve both high specific surface area and high filling density, resolving the contradiction between these two parameters.
Data Source
AI summary
Provided is a technology that realizes a more preferable specific surface area in a negative electrode active material layer including silicon. An electricity storage device disclosed herein includes a negative electrode active material layer including a negative electrode active material. The negative electrode active material includes first particles including silicon and second particles that include silicon and are different from the first particles. An average circularity CR1 of the first particles is 0.5 or more and 0.9 or less. An average circularity CR2 of the second particles is more than 0.9. A ratio (D1/D2) between an average particle diameter D1 of the first particles and an average particle diameter D2 of the second particles is 0.1 or more and less than 1.