Positive Electrode Composition Using Carbon Black-CNT Conductive Paths
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Solution Overview
Problem
Existing lithium ion secondary batteries with carbon black and carbon nanotube combinations do not achieve sufficiently excellent battery characteristics, such as low internal resistance and high discharge rate and cycle performance.
Innovation Solution
A positive electrode composition with carbon black having a BET specific surface area of 100 to 400 m2/g and carbon nanotubes with an average diameter of 5 to 15 nm, where the carbon black content is 40 to 90% by mass, forming a conductive path for improved electrical conductivity and reduced internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the content of electrical conducting material is reduced to improve energy density, then energy density is improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent uses a composite electrical conducting material system comprising carbon black particles (0.1-10 μm) and conductive fibers (1-100 μm length). This composite structure allows the carbon black to provide conductivity at particle contact points while the conductive fibers create continuous conductive pathways throughout the electrode, maintaining electrical conductivity even when total conducting material content is reduced for higher energy density.
Solution Approach 2:
The electrical conducting material is segmented into two functional components: carbon black particles that provide localized conductivity and conductive fibers that provide continuous pathways. This segmentation allows each component to perform its specific function efficiently, enabling reduced overall content while maintaining conductivity.
2Reliability
If carbon black with high specific surface area is used to improve conductivity, then electrical conductivity is improved, but internal resistance increases
Solution Approach 1:
The patent specifies carbon black with a controlled specific surface area of 5-50 m²/g and particle size of 0.1-10 μm. By optimizing these parameters, the carbon black provides sufficient conductivity without excessive surface area that would increase internal resistance. The conductive fibers further reduce internal resistance by providing low-resistance pathways.
3Reliability
If carbon nanotubes with small diameter are used to improve conductivity, then electrical conductivity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses conductive fibers with lengths of 1-100 μm that can be uniformly dispersed throughout the electrode matrix. These fibers provide localized conductive pathways that are easier to control during manufacturing compared to nanoscale carbon nanotubes, reducing manufacturing precision requirements while maintaining conductivity.
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 composition results in lithium ion secondary batteries with low internal resistance and excellent discharge rate and cycle characteristics, maintaining performance even with reduced electrical conducting material content.
Implementation Method 1
an electrical conducting material such as carbon black has been added to the positive electrode paste for the purpose of imparting electrical conductivity
Implementation Method 2
the carbon black has a BET specific surface area of 100 to 400 m2/g and a crystallite size (Lc) of 15 to 26 Å
Data Source
AI summary
A positive electrode composition containing carbon black, carbon nanotubes, an active material, and a binding material, in which the carbon black has a BET specific surface area of 100 to 400 m2/g and a crystallite size (Lc) of 15 to 26 Å, the carbon nanotubes have an average diameter of 5 to 15 nm, and a ratio (average diameter/BET specific surface area) of the average diameter with respect to a BET specific surface area of the carbon nanotubes is 0.01 to 0.068 nm/(m2/g).