Cathode Binder and Electrolyte Composition for Low-Temperature Batteries
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Solution Overview
Problem
Conventional secondary battery binders like polyvinylidene difluoride (PVDF) lead to gelation issues, affecting slurry stability and battery performance, and are environmentally harmful, failing to meet green and sustainable development requirements.
Innovation Solution
Employing polyvinyl butyral in the positive electrode and a specific combination of lithium difluorophosphate and trinitrile compounds in the electrolyte to enhance cohesion and reduce swelling, thereby improving shedding resistance and reducing initial resistance and enhancing low-temperature rate characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF is used as the binding material for forming the positive composite material layer, then the binding material can effectively bind the components, but it is prone to gelation leading to a decrease in slurry stability and affecting battery performance
Solution Approach 1:
The patent changes the chemical composition parameters of the binding material from PVDF to polyvinyl butyral, which has different gelation characteristics and bonding properties. This parameter change resolves the contradiction by maintaining binding capability while eliminating the gelation issue that affects slurry stability.
Solution Approach 2:
The patent uses a composite approach by combining polyvinyl butyral with specific electrolyte additives (lithium difluorophosphate and trinitrile compounds) to create a system where the binder and electrolyte work synergistically. This composite material strategy improves both binding performance and slurry stability simultaneously.
2Ease of manufacture
If PVDF is used as the binding material, then the positive composite material layer can be formed, but it is a fluorine-containing binder whose polymerization monomer VDF is prepared by dehydrochlorination of 1-chloro-1,1-difluoroethane (R142B), which is a high-risk environmental pollutant
Solution Approach 1:
The patent extracts and removes the harmful fluorine-containing component (PVDF) from the binding material system and replaces it with an environmentally friendly alternative (polyvinyl butyral). This extraction of the harmful substance eliminates the environmental pollution issue while maintaining manufacturing feasibility.
Solution Approach 2:
The patent adopts a more sustainable and environmentally acceptable binding material that does not rely on hazardous chemicals like R142B. This substitution aligns with green chemistry principles and sustainable development, replacing short-living, harmful materials with longer-living, eco-friendly alternatives.
3Reliability
If polyvinyl butyral is used in the positive electrode with specific particle size, degree of acetalation, and molecular weight, then the shedding resistance is improved, but the formulation complexity increases
Solution Approach 1:
The patent specifies precise parameter ranges for polyvinyl butyral (particle size: 20-100 microns, degree of acetalation: 30-60 mol%, molecular weight: 3×10^4 to 20×10^4) to optimize shedding resistance. By controlling these parameters within defined ranges, the patent achieves reliable performance while managing formulation complexity through standardized specifications.
Data Source
AI summary
A secondary battery, including: a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive current collector and a positive active material layer formed on the positive current collector, the positive active material layer includes a positive active material and polyvinyl butyral, and the electrolyte includes lithium difluorophosphate and a trinitrile compound. A shedding resistance of the positive electrode is improved, an initial resistance of the secondary battery is further reduced, and a low-temperature rate characteristic is further improved.