Silicon Anode Metal Gradient Relieves Stress Concentration
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Solution Overview
Problem
Lithium ion secondary batteries with graphite anodes face limitations in capacity due to the expansion and shrinkage of silicon-based anode active material layers, leading to reduced cycle characteristics and potential battery swelling.
Innovation Solution
Incorporating a metal element with varying concentrations in the anode active material layer, specifically in increasing and decreasing regions, to reduce internal resistance and alleviate stress concentration, thereby improving cycle characteristics and preventing swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used for the anode active material layer to increase battery capacity, then the battery capacity is improved, but the cycle characteristics are lowered due to pulverization from expansion and shrinkage
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of metal elements within the anode active material layer. The metal element concentration varies from the surface toward the interior, with higher concentration at the surface and lower concentration toward the center. This non-uniform distribution allows the surface regions to experience greater expansion and shrinkage while the interior regions experience less stress, thereby preventing pulverization and improving cycle characteristics while maintaining high battery capacity.
2Reliability
If a metal element is added to the anode active material layer to relax expansion and shrinkage, then the cycle characteristics are improved, but the internal resistance increases and lithium insertion becomes non-uniform
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through a spatially varying metal element concentration. By having higher metal element concentration at the surface and lower concentration toward the interior, the surface regions benefit from stress relaxation during expansion and shrinkage, improving cycle characteristics. Meanwhile, the interior regions with lower metal element concentration maintain better electrical conductivity and more uniform lithium insertion, thus avoiding the worsening of manufacturing precision.
3Quantity of substance
If the anode active material layer is intensely expanded and shrunk during charge and discharge, then the battery capacity is increased, but the anode current collector is deformed and the battery swells
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of metal elements that varies from the surface toward the interior of the anode active material layer. The surface regions with higher metal element concentration accommodate the expansion and shrinkage stresses, while the interior regions with lower concentration maintain structural integrity. This gradient distribution effectively manages the stress during intense expansion and shrinkage, preventing current collector deformation and battery swelling while allowing high battery 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 effectively decreases internal resistance, ensures uniform lithium insertion, and enhances cycle life by relaxing stress concentrations, resulting in improved battery performance and capacity retention.
Implementation Method 1
the internal resistance of the anode active material layer can be decreased, an electrode reactant such as lithium can be easily inserted into the anode active material layer, and insertion can be uniformly progressed
Implementation Method 2
Silicon or the like is largely expanded and shrunk due to charge and discharge
Data Source
AI summary
An anode capable of relaxing the stress concentration and improving the characteristics and a battery using it are provided. The anode includes an anode current collector and an anode active material layer containing silicon (Si) as an element, wherein an anode active material layer has a metal element increasing and decreasing region in which a metal element is contained as an element, and a concentration of the metal element is increased and then decreased in a thickness direction.