Positive Electrode Composition Balancing Conductivity and Adhesion
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Solution Overview
Problem
Conventional lithium ion secondary batteries face challenges in achieving low internal resistance and excellent discharge rate and cycle characteristics due to the poor conductivity of positive electrode active materials, necessitating improvements in the positive electrode composition and manufacturing processes.
Innovation Solution
A positive electrode composition comprising carbon black with a specific DBP/CDBP ratio of 2.0 or less, carbon nanotubes with an average diameter of 5 to 15 nm, and a binding material, combined with a controlled ratio of average diameter to BET specific surface area, is used to form a mixture layer on a current collector, enhancing conductivity and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional carbon black and carbon nanotube composites are used to improve conductivity, then electrical conductivity improves, but internal resistance remains high and discharge rate characteristics deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the DBP/CDBP ratio of carbon black within 1.05-2.00 and the carbon nanotube diameter within 4-16 nm. These specific parameter ranges optimize the balance between conductivity enhancement and internal resistance reduction, resolving the contradiction between improving conductivity and maintaining discharge rate characteristics
Solution Approach 2:
The patent uses composite materials by combining carbon black with specific DBP/CDBP ratio and carbon nanotubes with controlled diameter in defined weight ratios (0.01-5% carbon nanotubes, 95-99.99% carbon black). This composite structure synergistically improves conductivity while reducing internal resistance and enhancing discharge rate characteristics
2Reliability
If carbon nanotube diameter is reduced to enhance conductivity, then electrical conductivity improves, but adhesion and structural stability worsen
Solution Approach 1:
The patent applies parameter changes by optimizing the carbon nanotube diameter within the specific range of 4-16 nm. This parameter control ensures that the nanotubes are thin enough to provide excellent conductivity pathways while maintaining sufficient mechanical strength and adhesion properties for structural stability in the electrode
Solution Approach 2:
The patent applies local quality by creating a hierarchical structure where ultra-fine carbon nanotubes (4-16 nm) provide localized conductivity enhancement at critical interfaces, while the overall composite structure maintains global mechanical integrity through the carbon black matrix and binder system
3Strength
If DBP absorption amount is increased to improve adhesion, then adhesion improves, but internal resistance increases and discharge rate characteristics worsen
Solution Approach 1:
The patent applies parameter changes by precisely controlling the DBP/CDBP ratio within the optimal range of 1.05-2.00. This parameter optimization ensures sufficient adhesion through appropriate DBP absorption while preventing excessive absorption that would increase internal resistance and degrade discharge rate characteristics
Solution Approach 2:
The patent applies parameter changes by optimizing the ratio of average diameter to BET specific surface area of carbon nanotubes within 0.004-0.08 nm/(m2/g). This control ensures the carbon nanotubes provide adequate conductivity and adhesion without creating excessive surface area that would increase internal resistance
Data Source
AI summary
A positive electrode composition contains carbon black, a carbon nanotube, a binding material, and an active material. A ratio (DBP/CDBP) of a DBP absorption amount (DBP) to a compressed DBP absorption amount (CDBP) of the carbon black is 2.0 or less. The carbon nanotubes have an average diameter of 5 to 15 nm.