Positive Electrode Composition Using Dual-SP Dispersants
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving low internal resistance and excellent discharge rate and cycle characteristics due to poor conductivity of the positive electrode active material, which is exacerbated by inadequate dispersion of conductive materials.
Innovation Solution
A positive electrode composition incorporating carbon black and carbon nanotubes with specific BET surface areas and average diameters, along with dispersing agents having different solubility parameters (SP values), is formulated through a multi-step mixing process to ensure optimal dispersion and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive materials (carbon black only) are used in the positive electrode paste, then the manufacturing process is simple, but the conductivity is insufficient and internal resistance is high
Solution Approach 1:
The patent combines carbon black and carbon nanotubes to form a composite conductive material system. Carbon black provides baseline conductivity while carbon nanotubes create efficient conduction pathways due to their high aspect ratio and superior electrical properties. This composite approach resolves the contradiction by achieving high conductivity through material composition rather than increasing complexity of the paste formulation process.
Solution Approach 2:
The patent specifies precise parameters for carbon black (BET specific surface area: 100-500 m²/g, crystallite size Lc: 15-26 Å) and carbon nanotubes (average diameter: 5-15 nm, length: 1-10 μm). By controlling these physical parameters within defined ranges, the invention optimizes the conductive network formation while maintaining manageable manufacturing complexity.
2Reliability
If a single dispersing agent is used for conductive materials, then the formulation is simple, but the dispersion uniformity is poor leading to inadequate conductivity
Solution Approach 1:
The patent employs different dispersing agents tailored to specific conductive materials: a first dispersing agent for carbon black and a second dispersing agent for carbon nanotubes. Each dispersing agent is selected based on its compatibility and effectiveness with its target material, creating locally optimized dispersion conditions. This resolves the contradiction by achieving uniform dispersion through targeted material-specific approaches rather than uniform treatment.
Solution Approach 2:
The dispersing agents act as intermediary substances that facilitate the interaction between the conductive materials (carbon black and carbon nanotubes) and the liquid medium. By introducing these intermediary agents, the patent enables uniform dispersion of conductive materials without requiring complex formulation processes, thus resolving the contradiction between dispersion quality and formulation simplicity.
3Reliability
If carbon black with high BET specific surface area is used, then the conductivity improves, but the aggregation tendency increases reducing dispersion quality
Solution Approach 1:
The patent defines a specific range for carbon black BET specific surface area (100-500 m²/g) and crystallite size (15-26 Å). By controlling these parameters within optimal ranges, the invention balances the conductivity benefit of high surface area with the dispersion stability requirement. The specified crystallite size range particularly helps prevent aggregation while maintaining electrical conductivity.
Solution Approach 2:
The first dispersing agent specifically for carbon black acts as an intermediary that prevents aggregation of high-surface-area carbon black particles. This dispersing agent creates steric or electrostatic barriers between carbon black particles, allowing the system to achieve both high conductivity (from sufficient carbon black content) and stable dispersion (from prevented aggregation).
4Power
If the positive electrode active material is used alone without sufficient conductive material, then the paste formulation is simple, but the discharge rate characteristics are poor due to high internal resistance
Solution Approach 1:
The patent creates a composite conductive network using carbon black and carbon nanotubes in specific proportions (carbon nanotube content: 0.01-5 mass%, carbon black content: 0.1-5 mass%). This composite structure provides efficient three-dimensional conduction pathways that significantly improve discharge rate characteristics. The high aspect ratio of carbon nanotubes creates conductive bridges between active material particles, reducing internal resistance without requiring excessive conductive material content.
Solution Approach 2:
The introduction of carbon nanotubes adds a dimensional aspect to the conductive network. Their elongated structure (1-10 μm length) creates conductive pathways in multiple dimensions, forming a three-dimensional conductive network that efficiently connects active material particles. This dimensional enhancement improves power characteristics and discharge rate performance without proportionally increasing conductive material quantity.
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 reduced internal resistance and improved discharge rate and cycle characteristics by ensuring effective conduction paths and uniform dispersion of conductive materials.
Implementation Method 1
the conductive material includes carbon black and carbon nanotubes... ensures effective conduction paths
Implementation Method 2
the dispersing agent for a conductive material includes two or more dispersing agents having different SP values... uniform dispersion of conductive materials
Data Source
AI summary
A positive electrode composition containing a conductive material, an active material, a binding material, a dispersing agent for a conductive material, and a liquid medium, wherein the conductive material includes carbon black and carbon nanotubes, wherein the dispersing agent for a conductive material includes two or more dispersing agents having different SP values, and wherein the carbon black has a BET specific surface area of 100 to 500 m2/g.