Negative Electrode Carbon Material Distribution for Battery Resistance
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Solution Overview
Problem
Existing methods for producing negative electrodes for nonaqueous electrolyte secondary batteries face challenges in reducing DC resistance during charging and capacity retention rate during high temperature storage, particularly due to the adsorption of binders on carbon materials with large BET specific surface areas, which increases resistance and affects battery performance.
Innovation Solution
A method involving the use of two types of carbon materials with specific BET specific surface areas and mass ratios, where the first carbon material with a higher surface area is mixed with the thickener and the second carbon material with an even higher surface area is added later, minimizing binder adsorption on the first carbon material, thereby reducing DC resistance and enhancing capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon material with large BET specific surface area is mixed into negative electrode active material, then charging characteristic is improved (DC resistance is reduced), but binder is selectively adsorbed to the carbon material, which weakens the resistance reduction effect
Solution Approach 1:
The patent applies local quality by using two types of carbon materials with different BET specific surface areas (first carbon material: 30-100 m2/g, second carbon material: 200-500 m2/g) in specific mass ratios. The first carbon material provides structural stability while the second carbon material provides conductive network, creating different functional zones within the negative electrode to optimize both charging characteristic and DC resistance.
Solution Approach 2:
The patent uses composite materials by combining negative electrode active material with two types of carbon materials having different surface areas. This composite structure allows the second carbon material (higher surface area) to form a conductive network that reduces DC resistance, while the first carbon material (lower surface area) provides structural stability, achieving both improved charging characteristic and maintained low resistance.
2Reliability
If carbon material is added to negative electrode active material, then charging characteristic is improved, but capacity retention rate during high temperature storage deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the BET specific surface area parameters of the carbon materials used. The first carbon material has BET specific surface area of 30-100 m2/g and the second has 200-500 m2/g, with mass ratios satisfying specific formulas. This parameter optimization allows sufficient carbon material to improve charging characteristic while controlling the total surface area to minimize capacity retention loss during high temperature storage.
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
This approach effectively reduces DC resistance during charging and capacity retention rate loss during high temperature storage, improving the overall performance of nonaqueous electrolyte secondary batteries by optimizing the distribution and adsorption of binder materials.
Implementation Method 1
the thickener is thought to be adsorbed to the first carbon material
Implementation Method 2
the binder is thought to be selectively adsorbed to the second carbon material
Data Source
AI summary
A negative electrode active material, a first carbon material, a thickener, and a solvent are mixed to prepare a first dispersion solution. The first dispersion solution and a second carbon material are mixed to prepare a second dispersion solution. The second dispersion solution and a binder are mixed to prepare a negative electrode paint. The negative electrode paint is applied to a surface of a negative electrode current collector and dried to produce a negative electrode for a nonaqueous electrolyte secondary battery. The negative electrode active material has a BET specific surface area of 3 m2/g or more and 8 m2/g or less. The first carbon material has a BET specific surface area of 30 m2/g or more and 100 m2/g or less. The second carbon material has a BET specific surface area of 200 m2/g or more and 500 m2/g or less.