Silicon-Based Battery Anode Layering for Conductivity Stability
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Solution Overview
Problem
The conductivity and adhesion issues in negative electrodes of lithium secondary batteries are exacerbated by the migration of binders and conductive agents due to volume changes in silicon-based active materials, leading to reduced life and input/output characteristics.
Innovation Solution
A multi-layered negative electrode structure with a first layer containing a carbon-based active material and a second layer with silicon-based active material and carbon nanotube structures, where the carbon nanotubes are bonded side by side, forming a robust conductive network to maintain connectivity and minimize migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-walled carbon nanotubes are used as conductive agent to improve conductivity, then conductivity is improved, but the carbon nanotubes break due to volume expansion and contraction of silicon-based active material, degrading life characteristics
Solution Approach 1:
The negative electrode is divided into two distinct layers: a first negative electrode active material layer containing graphite and a second negative electrode active material layer containing silicon-based active material. This segmentation isolates the silicon-based material's volume expansion/contraction to the second layer, preventing it from affecting the conductive network in the first layer, thereby maintaining conductivity and improving life characteristics.
2Stability of the object's composition
If carbon nanotube dispersion with low solid content is used to uniformly arrange carbon nanotubes, then uniform arrangement is achieved, but binder and conductive agent migrate to upper portion during drying, reducing adhesion and conductivity
Solution Approach 1:
The negative electrode is divided into two distinct layers: a first negative electrode active material layer containing graphite and a second negative electrode active material layer containing silicon-based active material. This segmentation isolates the silicon-based material's volume expansion/contraction to the second layer, preventing it from affecting the conductive network in the first layer, thereby maintaining conductivity and improving life characteristics.
3Quantity of substance
If silicon-based active material is used to improve capacity, then capacity is improved, but volume excessively expands during charge and discharge, causing severe breakage of conductive network
Solution Approach 1:
The negative electrode is divided into two distinct layers: a first negative electrode active material layer containing graphite and a second negative electrode active material layer containing silicon-based active material. This segmentation isolates the silicon-based material's volume expansion/contraction to the second layer, preventing it from affecting the conductive network in the first layer, thereby maintaining conductivity and improving life characteristics.
Solution Approach 2:
The first negative electrode active material layer acts as an intermediary buffer layer between the current collector and the silicon-based active material layer. This intermediary layer absorbs and mitigates the mechanical stress from volume changes in the silicon-based material, protecting the conductive network from breakage while allowing the high-capacity silicon-based material to function.
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 multi-layered structure enhances adhesion and conductivity, improving the battery's life and input/output characteristics by preventing crack formation and maintaining electrical connectivity during volume changes.
Implementation Method 1
the carbon nanotube structures may strongly hold second negative electrode active material particles together while connecting the second negative electrode active material particles even with a large volume change of SiOx
Implementation Method 2
the carbon nanotube structures may strongly hold second negative electrode active material particles together
Data Source
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AI summary
The present invention relates to a negative electrode including a negative electrode collector, a first negative electrode active material layer disposed on the negative electrode collector, and a second negative electrode active material layer disposed on the first negative electrode active material layer, wherein the second negative electrode active material layer includes a second negative electrode active material and a second conductive agent, wherein the second negative electrode active material includes a silicon-based active material, the silicon-based active material includes SiOx(0≤x<2), the second conductive agent includes a carbon nanotube structure in which 2 to 5,000 single-walled carbon nanotube units are bonded side by side, and the carbon nanotube structure is included in an amount of 0.01 wt% to 1.0 wt% in the second negative electrode active material layer, and a secondary battery including the same.