Silicon Anode Particles with Low Circularity
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving high capacity due to shape deformation of anode active materials like silicon and tin, which result in lower charge and discharge characteristics.
Innovation Solution
An anode active material with particles having an average degree of circularity of 90% or less, made from silicon or its alloys, is used, along with an anode current collector with a surface roughness of 0.1 μm to 3.5 μm, to prevent shape deformation and enhance charge and discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon or tin is used as anode active material to achieve high capacity, then battery capacity is improved, but shape deformation occurs due to volume change during lithium insertion and extraction
Solution Approach 1:
The anode active material is divided into fine particles with an average degree of circularity of 90% or less. This segmentation into smaller units distributes the volume change stress, preventing macroscopic shape deformation and cracking while maintaining high lithium insertion capacity.
Solution Approach 2:
The invention controls the local geometric properties of particles by specifying an average degree of circularity of 90% or less. This local geometric characteristic creates sufficient surface area and reactive regions to accommodate volume changes during lithium insertion and extraction, preventing crack formation.
2Area of stationary object
If particles with high degree of circularity are used, then packing density is improved, but reactive surface area is reduced leading to local intense reaction and cracks
Solution Approach 1:
The anode active material is divided into fine particles with an average degree of circularity of 90% or less. This segmentation into smaller units distributes the volume change stress, preventing macroscopic shape deformation and cracking while maintaining high lithium insertion capacity.
Solution Approach 2:
The invention transitions from considering only particle size to also considering particle shape characteristics (degree of circularity). By controlling the degree of circularity to 90% or less, the invention optimizes the surface area to volume ratio and creates sufficient reactive regions distributed throughout the particle structure.
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 cracks and improves charge and discharge characteristics by increasing the reactive surface area, allowing for more uniform lithium insertion and reducing volume change, thereby maintaining superior battery performance.
Implementation Method 1
the volume is largely changed associated insertion and extraction of lithium (Li) and the shape is deformed
Data Source
AI summary
Anode active materials, anodes, and batteries are provided. In one embodiment, an anode active material includes particles consisting essentially of a material selected from the group consisting of silicon and an alloy of silicon. An average degree of circularity of the particles is 90% or less.