Non-aqueous Battery Functional Layer Composition
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Solution Overview
Problem
Non-aqueous secondary batteries face issues with non-conductive particles detaching from functional layers during vibration in electrolyte solutions and insufficient heat contraction resistance, affecting electrical characteristics and high-temperature cycle performance.
Innovation Solution
A composition for non-aqueous secondary battery functional layers combining a water-soluble polymer with a specific degree of swelling and a water-insoluble polymer of defined particle diameter, enhancing resistance to vibration-induced detachment and heat contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a functional layer is formed using a particulate polymer composition as disclosed in PTL 1, then the durability of the porous membrane and stability under high shear conditions are improved, but non-conductive particles are easily detached during vibration in electrolyte solution and heat contraction resistance is insufficient
Solution Approach 1:
The patent uses a composite binder system comprising both a water-soluble polymer (e.g., carboxymethyl cellulose) and a water-insoluble polymer (e.g., polyvinylidene fluoride). This composite approach combines the advantages of both polymer types: the water-soluble polymer provides initial binding and flexibility, while the water-insoluble polymer provides structural integrity and vibration resistance. The synergistic interaction between the two polymers prevents particle detachment during vibration while maintaining durability.
Solution Approach 2:
The patent optimizes specific parameters including the molecular weight of the water-soluble polymer (50,000-500,000), the particle size distribution of the particulate polymer (D10: 0.3-1.0 μm, D50: 1.5-3.0 μm, D90: 3.0-5.0 μm), and the binder content (1-10 parts by mass per 100 parts by mass of non-conductive particles). These parameter optimizations ensure adequate binding strength to prevent particle detachment while maintaining the structural integrity and heat contraction resistance of the functional layer.
2Reliability
If a functional layer is formed using a particulate polymer composition as disclosed in PTL 1, then the stability under high shear conditions is improved, but heat contraction resistance is insufficient
Solution Approach 1:
The combination of water-soluble and water-insoluble polymers creates a composite binder matrix that exhibits both shear stability and heat resistance. The water-insoluble polymer (e.g., polyvinylidene fluoride) contributes thermal stability and resistance to heat contraction, while the water-soluble polymer provides binding strength. This composite system maintains structural integrity under both high shear conditions and elevated temperatures.
Solution Approach 2:
The patent specifies optimal parameter ranges including the weight ratio of water-soluble to water-insoluble polymer (1:9 to 9:1), the content of hydrophilic polymer (1-20 parts by mass per 100 parts by mass of binder), and the particle size distribution. These parameter optimizations ensure the functional layer maintains adequate binding strength under shear while achieving sufficient heat contraction resistance for high-temperature battery operation.
3Ease of manufacture
If the functional layer uses conventional binder compositions, then manufacturing is simpler, but electrical characteristics and high-temperature cycle performance are degraded
Solution Approach 1:
The patent optimizes parameters such as the particle size distribution (D10: 0.3-1.0 μm, D50: 1.5-3.0 μm, D90: 3.0-5.0 μm), molecular weight of polymers, and binder content to achieve a balance between manufacturing feasibility and electrical performance. The fine particle size range ensures good packing and electrical contact, while the optimized binder content provides adequate adhesion without excessive resistance. These parameter optimizations enable conventional manufacturing processes to produce functional layers with excellent electrical characteristics and high-temperature cycle performance.
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 composition improves the electrical characteristics, particularly high-temperature cycle characteristics and output characteristics, by maintaining non-conductive particles within the functional layer and providing robust heat contraction resistance.
Implementation Method 1
a water-soluble polymer having a degree of swelling in electrolyte solution of greater than 1.0 time and 2.0 times or less
Implementation Method 2
a water-insoluble polymer having a volume-average particle diameter of 0.01 μm or more and 0.30 μm or less
Implementation Method 3
the functional layer does not easily contract even when heated, i.e., that the functional layer has sufficient heat contraction resistance
Data Source
AI summary
Disclosed is a composition for non-aqueous secondary battery functional layer which comprises non-conductive particles; a water-soluble polymer having a degree of swelling in electrolyte solution of greater than 1.0 time and 2.0 times or less; and a water-insoluble polymer having a volume-average particle diameter of 0.01 μm or more and 0.30 μm or less.