Secondary Battery Separator Coating for Adhesion and Dimensional Stability
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Solution Overview
Problem
Current secondary battery separators face challenges in achieving both wet and dry adhesiveness with electrodes and dimensional stability while maintaining low production costs, with existing methods being costly and insufficient in providing adequate adhesiveness and stability.
Innovation Solution
A secondary battery separator is developed with a porous layer composed of inorganic particles and organic resins having different melting points, including a fluororesin with a melting point of 130°C or higher, which provides both wet and dry adhesiveness and dimensional stability through a common coating method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous layer mainly composed of polyvinylidene fluoride resin is stacked on a porous base material to improve wet adhesiveness, then production cost increases
Solution Approach 1:
The patent uses a composite porous layer containing both polyvinylidene fluoride resin particles and inorganic particles (such as aluminum oxide, silica, or boehmite). This composite structure provides wet adhesiveness through the fluororesin while the inorganic particles contribute to dimensional stability and cost-effectiveness, reducing reliance on expensive pure fluororesin coatings
Solution Approach 2:
The porous layer is designed with specific particle size distributions and compositional gradients to optimize local properties. The fluororesin particles are distributed throughout the porous structure to provide localized adhesion points, while inorganic particles are positioned to maintain structural integrity and dimensional stability where needed
2Stability of the object's composition
If a porous layer with inorganic particles is stacked to improve dimensional stability, then production cost increases
Solution Approach 1:
The patent creates a cost-effective composite by combining relatively inexpensive inorganic particles (such as aluminum oxide, silica, or boehmite) with fluororesin particles. The inorganic particles provide dimensional stability through their high melting points and thermal resistance, while the fluororesin provides adhesion, allowing the use of lower-cost inorganic materials rather than expensive heat-resistant organic resins alone
Solution Approach 2:
The patent uses inorganic particles that are inherently stable and reusable in the sense that they maintain their properties throughout the battery's lifecycle. These particles provide long-term dimensional stability without degrading, replacing the need for more expensive alternative materials that would require frequent replacement or maintenance
3Reliability
If the molecular weight of polyvinylidene fluoride resin is not appropriately controlled, then sufficient wet adhesiveness cannot be obtained
Solution Approach 1:
The patent specifies precise molecular weight parameters for the polyvinylidene fluoride resin, requiring a weight average molecular weight of 100,000 or more and 5,000,000 or less. This parameter control ensures optimal balance between adhesion performance (requiring sufficient molecular weight for strong intermolecular forces) and processability (requiring lower molecular weight for easier handling and coating)
Solution Approach 2:
The patent allows different molecular weight ranges for different applications and positions within the porous layer. By controlling the local molecular weight distribution and particle size, the patent optimizes adhesion properties in specific regions while maintaining overall manufacturing feasibility
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 solution enables high-capacity, long-lasting lithium-ion batteries with improved adhesiveness and stability at a lower cost, ensuring effective ion movement and preventing short circuits.
Implementation Method 1
the porous layer including a fluororesin having a melting point of 130 °C or higher... the porous layer has a melting point of 130°C or higher and lower than 180 °C and a melting point of 20°C or higher and lower than 130°C
Implementation Method 2
a characteristic in which the separator contains an electrolyte solution in a porous structure, so that ion movement is possible
Implementation Method 3
secondary battery separators have been required to have dimensional stability for preventing a short circuit resulting from contact between a positive electrode and a negative electrode, which is caused by thermal shrinkage of the secondary battery separator at a high temperature
Data Source
AI summary
The purpose of the present invention is to provide a secondary battery separator which exhibits adhesiveness with an electrode and dimensional stability at a low cost. The secondary battery separator of the present invention is a separator including: a porous base material; and a porous layer stacked on at least one surface of the porous base material, the porous layer being mainly composed of inorganic particles, and two or more organic resins having different melting points, the porous layer including a fluororesin as at least one of the organic resins, the secondary battery separator satisfying at least one of the following requirements (A) and/or (B): (A) the porous layer has a melting point of 130°C or higher and 20°C or higher and lower than 130°C; and (B) the porous layer has a melting point of 130°C or higher, and includes an amorphous organic resin.