Dry Battery Electrode Sheet with Low-Shear PTFE for Stretchability
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Solution Overview
Problem
Existing methods for producing non-aqueous electrolyte secondary battery electrodes, particularly those using a dry method, face issues with poor stretchability of the mixture sheet, leading to reduced productivity and strength in the thickness direction of the electrode.
Innovation Solution
A method involving the use of a fibrous binder containing polytetrafluoroethylene with a shear bond stress of less than or equal to 40 kPa as a main component, applied in a mixture sheet prepared with a solid content concentration of 100%, which is bonded to a core material to enhance stretchability and thickness-direction strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a dry method is used to prepare a mixture sheet by stretching electrode mixture powder, then the binder distribution uniformity is improved, but the stretchability of the sheet deteriorates
Solution Approach 1:
The invention changes the particle size parameter of the PTFE binder from conventional fine particles to coarse particles with specific size range (5-50 μm). This parameter change fundamentally alters the deformation behavior during stretching, allowing the sheet to stretch without breaking while maintaining binder distribution uniformity. The coarse particles act as spacers that prevent excessive binder aggregation during the stretching process.
Solution Approach 2:
The invention creates a composite structure by combining electrode mixture powder with coarse PTFE particles having specific physical properties (low shear bond stress ≤40 kPa). This composite material approach allows the mixture sheet to exhibit both good stretchability (from the loose binding of coarse particles) and uniform binder distribution (from the spacing effect of particles with 5-50 μm size range).
2Productivity
If the stretchability of the mixture sheet is improved, then the productivity is increased, but the strength in the thickness direction may be reduced
Solution Approach 1:
The invention optimizes the particle size parameter of PTFE to 5-50 μm, which creates an optimal balance between stretchability and thickness-direction strength. The coarse particles provide spacing that enables stretching (improving productivity), while their specific size range ensures sufficient mechanical interlocking and bonding to maintain adequate strength in the thickness direction after stretching.
Solution Approach 2:
The invention creates local quality differences in the binder structure: coarse PTFE particles are distributed throughout the electrode mixture powder to provide spacing and stretchability, while the particles themselves maintain bonding capability for thickness-direction strength. This local differentiation of functions within the binder system resolves the contradiction between stretchability and strength.
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 method results in a mixture sheet with improved stretchability and increased strength in the thickness direction of the electrode, ensuring better productivity and structural integrity.
Implementation Method 1
the binder contains polytetrafluoroethylene having a shear bond stress less than or equal to 40 kPa as a main component
Data Source
Figure 1~3
AI summary
The present invention provides a method for producing an electrode with which it is possible to obtain a mixture sheet exhibiting good stretchability. This method for producing an electrode (10) is characterized by including a mixture sheet preparation step in which a powder (20) of an electrode mixture including an active material and a fibrous binder and having a solid content concentration of substantially 100% is molded into a sheet shape to prepare a mixture sheet (12), and a bonding step in which the mixture sheet (12) is bonded to the surface of a core material (11), wherein the binder contains polytetrafluoroethylene having a shear bond stress of 40 kPa or less as a main component.