Si Composite Particle Structure for Battery Expansion Control
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Solution Overview
Problem
Conventional active materials comprising Si face challenges in maintaining cycle characteristics under varying constraints, particularly due to volume expansion during charging which can lead to cracks and gaps in secondary batteries.
Innovation Solution
The development of an active material composite particle comprising Si and a resin, where the resin area ratio is higher in the surface layer than in the center, with higher porosity in the center portion, effectively moderating volume change and maintaining the composite particle's shape, thereby enhancing cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si is used as active material, then battery capacity is improved, but volume expansion during charging causes cracks and gaps reducing cycle characteristics
Solution Approach 1:
The patent applies local quality by creating a composite particle structure where Si particles are concentrated in the center portion and resin is concentrated in the surface layer portion. This spatial differentiation allows the Si-rich center to provide high capacity while the resin-rich surface provides structural stability and crack prevention, resolving the contradiction between capacity improvement and cycle characteristic degradation.
2Quantity of substance
If Si particles are aggregated to increase capacity, then battery performance is improved, but volume expansion leads to particle cracking and gaps
Solution Approach 1:
The patent employs composite materials by combining Si particles with resin to form a composite particle structure. The Si particles provide high capacity while the resin matrix provides mechanical strength and flexibility to accommodate volume expansion, preventing particle cracking and maintaining integrity during charge-discharge cycles.
Solution Approach 2:
The composite particle structure distributes Si particles in the center portion surrounded by resin in the surface layer, creating local quality differences that allow the Si-rich core to deliver capacity while the resin-rich shell maintains particle strength and prevents cracking during volume changes.
3Reliability
If resin content is increased to prevent cracking, then cycle characteristics are improved, but active material content decreases reducing capacity
Solution Approach 1:
The patent resolves this contradiction by applying local quality through spatial differentiation: Si particles are concentrated in the center portion to maximize capacity contribution, while resin is concentrated in the surface layer portion to provide crack prevention. This arrangement optimizes both capacity and cycle characteristics by giving each material its optimal location.
Solution Approach 2:
The patent transitions from a homogeneous mixture to a structured composite particle with distinct center and surface layer portions. This dimensional organization allows simultaneous optimization of capacity (center) and durability (surface layer), resolving the trade-off between resin content for crack prevention and active material content for capacity.
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 results in improved cycle characteristics under both high and low constraint pressures by moderating volume expansion and reducing the likelihood of cracks and gaps, ensuring stable battery performance.
Implementation Method 1
volume expansion during charging which can lead to cracks and gaps
Implementation Method 2
a porosity in a center portion of the composite particle is higher than a porosity in a surface layer portion
Data Source
Figure 1A~1B
Figure 2~3
Figure 4A~4B
AI summary
Disclosed is an active material composite particle comprising Si and having excellent cycle characteristics under low constraint. The active material composite particle of the present disclosure comprises Si and a resin, wherein an area ratio of the resin in a surface layer portion of the composite particle is higher than an area ratio of the resin in a center portion of the composite particle when a cross-section of the composite particle is observed.