Positive Electrode Pore Structure for Stable DC Resistance
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Solution Overview
Problem
Conventional positive electrodes for energy storage devices experience a significant increase in direct-current resistance during charge-discharge cycles due to insufficient electrolyte penetration and retention, leading to reduced electron conduction paths and increased resistance.
Innovation Solution
A positive electrode design incorporating a particulate conductive agent and a fibrous conductive agent with specific pore volume distribution characteristics, including a median pore diameter of 100 nm or more and a peak height ratio of 1.20 or less, ensuring adequate voids for electrolyte penetration and retention, thereby reducing direct-current resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional positive electrode structure with particulate conductive agent is used, then the electrode can be manufactured with simple structure, but the direct-current resistance increases significantly during charge-discharge cycles
Solution Approach 1:
The patent applies composite materials by combining particulate conductive agents (acetylene black) with fibrous conductive agents (carbon nanotubes) in a specific configuration. The carbon nanotubes form a three-dimensional network structure that provides stable electron conduction paths, while the acetylene black particles fill interstitial spaces. This composite structure maintains low direct-current resistance throughout charge-discharge cycles, resolving the contradiction between reliability and structural simplicity.
Solution Approach 2:
The patent implements local quality by creating regions with different conductive agent concentrations and types. The fibrous conductive agent forms a continuous three-dimensional network in specific regions to ensure stable electron transport, while particulate conductive agents are distributed in other regions to enhance conductivity. This spatial differentiation of conductive properties maintains low resistance stability without requiring complex overall restructuring.
2Reliability
If the pore volume distribution is optimized with median pore diameter of 100 nm or more and peak height ratio of 1.20 or less, then electrolyte penetration and retention are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by optimizing the pore volume distribution through controlled formation of the three-dimensional network structure. By adjusting the median pore diameter to 100 nm or more and controlling the peak height ratio to 1.20 or less, the electrode achieves improved electrolyte penetration and retention. These parameter optimizations are accomplished through the self-organizing nature of the fibrous conductive agent network during electrode fabrication, reducing the need for precise external control while achieving reliable electrolyte access.
3Reliability
If fibrous conductive agent with diameter of 60 nm or less is used to enhance electron conduction, then the electron conduction path efficiency improves, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the conductive agent system into two functional segments: fibrous conductive agents (carbon nanotubes with diameter 60 nm or less) that form a three-dimensional network for efficient electron transport, and particulate conductive agents (acetylene black) that fill interstitial spaces. This segmentation allows each component to perform its specialized function optimally, with the fibrous segment providing high-efficiency conduction paths without requiring complex overall device architecture.
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 electrode structure significantly reduces the rate of increase in direct-current resistance during charge-discharge cycles, enhancing the longevity and performance of energy storage devices by maintaining efficient electron conduction paths and electrolyte distribution.
Implementation Method 1
a positive active material layer containing a positive active material, a particulate conductive agent, and a fibrous conductive agent
Implementation Method 2
a pore volume distribution of the positive active material layer has a median pore diameter of 100 nm or more, a Log differential pore volume distribution curve determined from the pore volume distribution has a first peak that appears in a pore diameter range of 10 nm or more and less than 100 nm, and a second peak that appears in a pore diameter range of 100 nm or more and less than 2000 nm
Data Source
AI summary
A positive electrode for an energy storage device according to an aspect of the present invention includes a positive active material layer containing a positive active material, a particulate conductive agent, and a fibrous conductive agent, the fibrous conductive agent is 60 nm or less in diameter, a pore volume distribution of the positive active material layer has a median pore diameter of 100 nm or more, a Log differential pore volume distribution curve determined from the pore volume distribution has a first peak that appears in a pore diameter range of 10 nm or more and less than 100 nm, and a second peak that appears in a pore diameter range of 100 nm or more and less than 2000 nm, and the ratio of the height of the second peak to the height of the first peak (second peak/first peak) is 1.20 or less.