Si Granulated Anode Powder for Lithium-Ion Cycle Stability
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Solution Overview
Problem
Silicon (Si) based negative electrode materials for lithium-ion batteries suffer from significant volume expansion and contraction due to lithium occlusion, leading to cracking and peeling from the current collector, which deteriorates cycle characteristics and reduces charge and discharge capacity.
Innovation Solution
A negative electrode material powder comprising a Si-containing granulated body formed by aggregating primary particles of Si phase, Si compound phase, and Sn compound phase, with a defined average particle diameter range for the primary particles, allowing for a reduced binder content of 0-2.0 mass%, and a balanced composition to enhance battery characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si is used as the negative electrode active material to increase capacity, then the theoretical capacity increases from 372 mAh/g to 4198 mAh/g, but Si particles crack or peel off from the current collector due to large volume expansion and contraction, deteriorating cycle characteristics
Solution Approach 1:
The Si-containing granulated body is divided into multiple primary particles (0.1-10.0 μm) that aggregate together. Each primary particle can independently expand and contract during Li occlusion/release, reducing stress concentration and preventing crack propagation throughout the entire structure. This segmentation allows Si to maintain high capacity while improving structural stability during cycling.
Solution Approach 2:
The granulated body structure with primary particles of controlled size (0.1-10.0 μm) and specific distribution (d50 of primary particles between 1/200 to 1/3 of granulated body d50) creates internal buffer spaces that accommodate volume expansion before cracking occurs. This pre-designed structure cushioning prevents particle fracture and detachment from the current collector during repeated charging-discharging cycles.
2Reliability
If a binder is used to bind particles in the Si-containing granulated body to prevent cracking, then cycle characteristics improve, but the binder does not involve in charging and discharging of Li, causing a decrease in charge and discharge capacity
Solution Approach 1:
The invention optimizes the particle size parameters of primary particles (0.1-10.0 μm range with d50 between 1/200 to 1/3 of granulated body d50) to achieve a structure that is inherently resistant to cracking without requiring excessive binder. This parameter optimization reduces the binder content to 0-2.0 mass%, minimizing the non-active material while maintaining structural integrity and high charge-discharge 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
The solution prevents collapse of the Si-containing granulated body, improves cycle characteristics, and maintains initial discharge capacity by providing a buffer region for volume expansion, while minimizing the need for a binder, thus enhancing overall battery performance.
Implementation Method 1
Si has large volume expansion and contraction along with occlusion and release of Li due to occlusion of Li by an alloying reaction with Li
Data Source
Figure 1~2
Figure 3(A)~3(D)
AI summary
The present invention relates to a negative electrode material powder for a lithium-ion battery, the negative electrode material powder comprising a Si-containing granulated body that includes a Si phase, a Si compound phase, and a Sn compound phase, of which the primary particles are aggregated, and arbitrarily and selectively contains a binder within the range of 0-2.0 mass%. The average grain diameter (d50) of the primary particles forming the Si-containing granulated body is within the range of 0.1-10.0 µm. The average grain diameter (d50) of the primary particles is less than 1/3 of, and greater than 1/200 of, the average grain diameter (d50) of the Si-containing granulated body.