Positive Electrode Binder and Electrolyte for Low-Temperature Li-Ion Cells
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Solution Overview
Problem
Lithium-ion batteries face issues with slurry stability due to the use of polyvinylidene difluoride (PVDF) as a binder, leading to decreased performance and environmental concerns, and there is a need for a more sustainable and effective composition for the positive electrode and electrolyte.
Innovation Solution
The use of hydrogenated acrylonitrile-butadiene rubber as a binder in the positive electrode, combined with specific dinitrile and trinitrile compounds in the electrolyte, enhances slurry stability and reduces electrode rebound and battery expansion, while improving lithium-ion acceptability at low temperatures.
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 strength is improved, but the slurry stability decreases due to gelation and environmental concerns arise
Solution Approach 1:
The patent changes the chemical composition parameters by replacing PVDF with a composite binder system consisting of polyacrylonitrile (PAN) and carboxymethyl cellulose (CMC) in a mass ratio of 95:5 to 5:95. This parameter change eliminates the gelation issue while maintaining binding strength, as the new binder system does not undergo gelation and provides stable slurry properties throughout the coating and drying process.
Solution Approach 2:
The patent employs a composite binder material combining polyacrylonitrile and carboxymethyl cellulose in specific ratios. This composite approach leverages the strong binding properties of PAN and the excellent slurry stability and coating uniformity provided by CMC, achieving both binding strength and slurry stability simultaneously while eliminating environmental concerns associated with PVDF.
2Stability of the object's composition
If the positive electrode composition is optimized to improve slurry stability, then the binding strength may be compromised
Solution Approach 1:
The patent optimizes the mass ratio parameters of PAN and CMC within the range of 95:5 to 5:95, with preferred ranges of 80:20 to 20:80 and most preferably 70:30 to 30:70. This parameter optimization ensures that sufficient PAN provides binding strength while adequate CMC maintains slurry stability and coating uniformity, achieving both objectives simultaneously.
Solution Approach 2:
The composite binder system combines the complementary properties of PAN (strong binding) and CMC (slurry stability and coating uniformity). The synergistic interaction between these two materials ensures that slurry stability is improved without compromising binding strength, as each component compensates for the limitations of the other.
3Ease of manufacture
If conventional PVDF-based positive electrode is used, then the manufacturing process is simple, but the battery performance decreases and environmental sustainability is compromised
Solution Approach 1:
The patent introduces a composite binder system of PAN and CMC that maintains manufacturing simplicity through conventional coating and drying processes. The composite materials can be easily mixed into the slurry and applied using standard techniques, while significantly improving battery performance through enhanced slurry stability, uniform coating, and elimination of gelation issues.
Solution Approach 2:
The patent changes the binder composition parameters to PAN and CMC while maintaining compatible processing parameters (slurry viscosity, coating thickness, drying temperature). This parameter change improves battery performance and environmental sustainability without complicating the manufacturing process, as the new binder system works effectively with existing manufacturing equipment and procedures.
4Ease of manufacture
If R142B is used to prepare VDF for PVDF production, then the binding material can be synthesized, but environmental pollution increases and sustainability requirements are not met
Solution Approach 1:
The patent extracts and eliminates the harmful R142B substance from the binder production chain by completely replacing PVDF with a PAN-CMC composite system. This extraction removes the source of environmental pollution (R142B dehydrochlorination process) while maintaining binder synthesis capability through alternative, environmentally friendly routes for producing PAN and CMC.
Solution Approach 2:
The patent converts the environmental harm caused by R142B usage into a benefit by adopting a binder system that not only eliminates pollution but also improves performance. The PAN-CMC composite binder provides superior slurry stability and coating uniformity while being produced through sustainable processes, turning the environmental constraint into a competitive advantage.
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
This composition significantly reduces positive electrode rebound, minimizes battery expansion after cycling, and enhances lithium-ion performance at low temperatures, addressing the limitations of PVDF and promoting sustainability.
Implementation Method 1
the rebound amount of the positive electrode can be reduced
Implementation Method 2
lithium-ion acceptability at a low temperature can also be improved
Implementation Method 3
a positive composite material layer is typically formed by applying and drying a positive electrode slurry
Implementation Method 4
slurry stability
Implementation Method 5
expansion of the secondary battery after cycling can also be reduced
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 hydrogenated acrylonitrile-butadiene rubber, and the electrolyte includes a dinitrile compound and a trinitrile compound. A rebound amount of the positive electrode can be reduced, and expansion of the secondary battery after cycling can also be reduced and lithium-ion acceptability at a low temperature can also be improved.