Graphite Negative Electrode Composition for Low-Swelling Li-Ion Cycling
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Solution Overview
Problem
Conventional negative electrodes in secondary batteries, particularly lithium ion batteries, face challenges in suppressing thickness changes during repetitive charge and discharge cycles and maintaining capacity at high temperatures, leading to potential battery case swelling and capacity deterioration.
Innovation Solution
A negative electrode configuration using graphite as the active material and single-wall carbon nanotubes as conductive material, with a mass proportion of 0.02% to 0.08% of single-wall carbon nanotubes, which helps in binding graphite particles and reducing lithium ion intercalation, thereby minimizing thickness changes and enhancing high-temperature storage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-wall carbon nanotubes are used as conductive material in negative electrode active material layer, then cycle characteristics are enhanced, but thickness change of negative electrode in repetitive charge and discharge increases
Solution Approach 1:
The patent changes the type of carbon nanotube from multi-wall to single-wall, and optimizes the content parameter to 0.02-0.08 mass%. This parameter change resolves the contradiction by maintaining conductive functionality while reducing the thickness expansion effect, achieving both good cycle characteristics and minimal thickness change.
Solution Approach 2:
The patent creates a composite structure where single-wall carbon nanotubes are dispersed within the graphite particle layers. This composite material approach allows the nanotubes to provide conductive pathways and structural support without causing excessive thickness expansion, thus improving cycle characteristics while controlling dimensional changes.
2Reliability
If dimensional change of electrode body is large, then battery characteristics are affected, but suppression of negative electrode thickness change is difficult to achieve
Solution Approach 1:
By changing from multi-wall to single-wall carbon nanotubes and optimizing content to 0.02-0.08 mass%, the patent minimizes the thickness change parameter of the negative electrode. This directly addresses the dimensional stability issue, preventing battery characteristic degradation while maintaining necessary conductive properties.
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 proposed configuration effectively suppresses negative electrode thickness changes during charge and discharge cycles and provides excellent high-temperature storage characteristics by reducing capacity deterioration, ensuring better battery performance and safety.
Implementation Method 1
single-wall carbon nanotubes... binding graphite particles
Implementation Method 2
single-wall carbon nanotube... conductive material
Implementation Method 3
graphite as a negative electrode active material... lithium ion intercalation
Data Source
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AI summary
Provided is a negative electrode using graphite as a negative electrode active material and using carbon nanotubes as a conductive material. The negative electrode can suppress a change in thickness of the negative electrode in repetitive charge and discharge of a secondary battery and provides the secondary battery with excellent high-temperature storage characteristics. The negative electrode disclosed here includes a negative electrode current collector and a negative electrode active material layer supported on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material and single-wall carbon nanotubes. The negative electrode active material consists essentially of graphite. A mass proportion of the single-wall carbon nanotubes to the negative electrode active material is 0.02 mass% or more and 0.08 mass% or less.