Layered Positive Electrode with CNT Network for Rolling Durability
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Solution Overview
Problem
Existing lithium secondary batteries face issues with high resistance due to inadequate conductivity in the positive electrode, leading to accelerated damage of the positive electrode active material during the rolling process and reduced lithium ion diffusion rates.
Innovation Solution
A positive electrode design featuring a first active material layer and a second active material layer with interconnected carbon nanotube structures, where 2 to 5,000 single-walled carbon nanotube units are bonded side by side to form a network structure, enhancing conductivity and minimizing damage during rolling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-walled carbon nanotube units are completely dispersed to improve conductivity, then electrical conductivity is improved, but the nanotube units are easily broken and accelerate damage of the positive electrode active material
Solution Approach 1:
The patent applies local quality by creating regions with different carbon nanotube configurations: the first positive electrode active material layer contains completely dispersed single-walled carbon nanotube units for high conductivity, while the second layer contains bundled nanotube units for mechanical strength. This spatial differentiation allows each layer to optimize for its specific function.
Solution Approach 2:
The patent uses composite materials by combining two types of carbon nanotube structures (dispersed units and bundled units) in a multi-layer electrode configuration. The composite structure integrates the high conductivity of dispersed nanotubes with the mechanical robustness of bundled nanotubes, resolving the contradiction between electrical performance and structural integrity.
2Stability of the object's composition
If carbon nanotube dispersion with low solid content is used to uniformly arrange carbon nanotubes, then uniform distribution is achieved, but positive electrode adhesion and electrical conductivity are significantly reduced due to migration phenomenon
Solution Approach 1:
The patent segments the electrode into two distinct layers to resolve the contradiction. The first layer uses low solid content dispersion for uniform nanotube distribution, while the second layer uses high solid content dispersion to prevent migration and ensure good adhesion. This segmentation allows each layer to optimize for its specific requirement without compromising the other.
Solution Approach 2:
The patent changes the solid content parameter of the carbon nanotube dispersion between layers: low solid content (0.1-5 wt%) in the first layer for uniform distribution, and high solid content (5-20 wt%) in the second layer to suppress migration. This parameter variation resolves the contradiction between uniformity and adhesion.
3Reliability
If single-walled carbon nanotube units with small diameter are used to improve conductivity, then conductivity is enhanced, but they block space between active materials and reduce porosity and lithium ion diffusion rate
Solution Approach 1:
The patent applies local quality by placing dispersed single-walled carbon nanotube units primarily in the first positive electrode active material layer where they provide conductivity without excessively blocking pores. The second layer uses bundled nanotubes that occupy less space while maintaining conductivity, thereby preserving porosity and lithium ion diffusion pathways in the overall electrode structure.
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 design significantly reduces the damage of positive electrode active materials during the rolling process, improves electrical conductivity, and enhances the input/output characteristics and life characteristics of the battery.
Implementation Method 1
carbon nanotube structures in which 2 to 5,000 single-walled carbon nanotube units are bonded side by side... enhancing conductivity
Implementation Method 2
a non-aqueous electrolyte containing lithium ions is included in an electrode assembly which includes a positive electrode including a positive electrode active material capable of intercalating/deintercalating the lithium ions
Data Source
Figure 1(A)~1(C)
Figure 2(A)~2(B)
Figure 3
AI summary
The present invention relates to a positive electrode which includes a positive electrode collector, a first positive electrode active material layer which is disposed on the positive electrode collector and includes a first positive electrode active material, and a second positive electrode active material layer disposed on the first positive electrode active material layer, wherein the second positive electrode active material layer includes a second positive electrode active material, and a carbon nanotube structure in which 2 to 5,000 single-walled carbon nanotube units are bonded side by side, wherein the carbon nanotube structure is included in an amount of 0.01 wt% to 1.0 wt% in the second positive electrode active material layer, and a secondary battery including the same.