PTFE-SWCNT Electrode Binder for Low-Resistance Dry Batteries
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Solution Overview
Problem
Conventional binders for lithium ion batteries face challenges in reducing electrode resistance and achieving high strength, often requiring solvents that increase costs and introduce moisture, which can degrade battery performance.
Innovation Solution
A binder composed of a mixed powder of polytetrafluoroethylene (PTFE) and single-walled carbon nanotubes, with specific properties such as a standard specific gravity of 2.11 to 2.20 and a G/D ratio of 2 or more, is used to create a fibrillated structure that acts as a binder, reducing moisture content and improving dispersibility, thereby enhancing electrode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional binders are used for lithium ion batteries, then the electrode can be formed, but the electrode resistance is high and strength is insufficient
Solution Approach 1:
The patent uses a composite binder system combining PTFE (polytetrafluoroethylene) with conductive carbon materials. This composite approach allows the binder to simultaneously provide mechanical strength through PTFE's fibrous structure and electrical conductivity through the carbon component, resolving the contradiction between strength and resistance.
Solution Approach 2:
The patent optimizes specific parameters of the PTFE binder including standard specific gravity (2.11 to 2.20), G/D ratio (2 or more for single-walled carbon nanotubes), and fibril diameter (20 nm or more). These parameter changes enable the binder to achieve both high strength and low resistance properties.
2Ease of manufacture
If solvents are used in binder preparation, then the binder can be applied, but moisture is introduced that degrades battery performance
Solution Approach 1:
The patent extracts and eliminates the harmful solvent component from the binder system. By using a solvent-free PTFE-based binder composition, the invention removes the source of moisture while maintaining ease of manufacture through direct mixing and application of the binder components.
Solution Approach 2:
The PTFE (polytetrafluoroethylene) material inherently provides a chemically inert environment that resists moisture absorption and degradation. This inert characteristic protects the battery components from moisture-related damage while allowing for practical manufacturing and application.
3Reliability
If single-walled carbon nanotubes are used as conductive material, then electrical conductivity improves, but dispersibility and homogeneity are difficult to achieve
Solution Approach 1:
The PTFE acts as an intermediary material that facilitates the uniform dispersion of single-walled carbon nanotubes. The fibrillated PTFE structure provides a matrix that distributes the carbon nanotubes homogeneously throughout the binder, preventing aggregation and ensuring stable composition while maintaining high electrical 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 binder effectively reduces electrical resistance and increases the strength of the electrode, improving battery performance by minimizing moisture contact with active materials and ensuring homogeneous distribution of single-walled carbon nanotubes, leading to higher energy density and reduced production costs.
Implementation Method 1
studies have been made on the use of a single-walled carbon nanotube as an electrically conductive material in a negative electrode
Implementation Method 2
The electrode preferably has a polytetrafluoroethylene resin having a fibrous structure with a fibril diameter (median value) of 20 nm or more
Implementation Method 3
a binder including a mixed powder, the mixed powder including a polytetrafluoroethylene resin and a single-walled carbon nanotube
Implementation Method 4
The method for producing a binder, including homogeneously mixing a PTFE dispersion and a single-walled carbon nanotube dispersion by using water as a dispersion solvent, followed by drying to form a mixed powder. The method for the drying is preferably spray drying.
Implementation Method 5
The binder preferably has a moisture content of 1,000 ppm or less
Data Source
AI summary
A binder containing a mixed powder including a polytetrafluoroethylene resin and a single-walled carbon nanotube. A weight ratio of the polytetrafluoroethylene resin to the single-walled carbon nanotube is 99.9:0.1 to 80:20. Also disclosed is a composition for producing an electrode in a form of a powder including the binder and an electrode active material substantially free of a liquid medium; an electrode mixture including the composition for producing an electrode; an electrode using the electrode mixture; a secondary battery having the electrode; a method for producing the binder; and a method for producing the electrode.