Positive Electrode Binder Composition for Dispersibility and Heat Storage
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Solution Overview
Problem
Existing binder compositions for non-aqueous secondary battery positive electrodes fail to achieve a balance between high dispersibility of conductive material dispersion liquids and excellent high-temperature storage characteristics.
Innovation Solution
A binder composition with a polymer containing a nitrile group-containing monomer unit, having a weight-average molecular weight of 300,000 or less and a sulfur content of 500 ppm or more, which includes a linear alkylene structural unit with a carbon number of 4 or more in a proportion of 30-80 mass % and a nitrile group-containing monomer unit in a proportion of 10-55 mass %, enhancing dispersibility and high-temperature storage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binder compositions are used, then the battery can be manufactured with standard materials, but the dispersibility of conductive material dispersion liquid is insufficient and high-temperature storage characteristics are poor
Solution Approach 1:
The patent changes the molecular weight parameter of the binder polymer to 300,000 or less (which is relatively low compared to conventional binders) and controls the sulfur content to be 500 ppm or more. These parameter changes enable the binder to provide both excellent dispersibility of conductive materials and superior high-temperature storage characteristics, resolving the technical contradiction between reliability and ease of manufacture.
Solution Approach 2:
The patent uses a composite binder system comprising a polymer with specific molecular weight and sulfur content, combined with a dispersant having a carboxyl group. This composite material approach enhances both the dispersibility of conductive materials and the high-temperature storage stability, achieving the desired balance between the conflicting requirements.
2Strength
If the molecular weight of the binder polymer is increased to improve mechanical strength, then the electrode structure is strengthened, but the dispersibility of conductive material decreases
Solution Approach 1:
The patent optimizes the molecular weight parameter to 300,000 or less, which is a specific threshold value that balances mechanical strength and dispersibility. This parameter change ensures that the electrode maintains sufficient structural strength while the binder provides excellent dispersibility of conductive materials, resolving the contradiction between strength and ease of operation.
3Reliability
If sulfur content in the binder is increased to improve high-temperature storage characteristics, then the battery stability at high temperature is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The patent sets the sulfur content parameter to 500 ppm or more, which is a straightforward quantitative specification that can be controlled during polymer synthesis. This parameter change provides excellent high-temperature storage characteristics without significantly increasing manufacturing complexity, as it involves a simple compositional threshold rather than a complex multi-component system.
Data Source
AI summary
A binder composition for a non-aqueous secondary battery positive electrode contains a polymer. The polymer includes a nitrile group-containing monomer unit and has a weight-average molecular weight of 300,000 or less and a sulfur content of 500 ppm or more.