Fine Pore Formation Agent for Battery Separator
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Solution Overview
Problem
Conventional methods for producing porous resin films for lithium secondary batteries result in high inner resistance, uneven pore distribution, and the risk of short circuits due to coarse particles and conductive impurities, making them unsuitable for large-scale and automotive batteries.
Innovation Solution
A fine pore formation agent comprising inorganic particles with specific size and surface area characteristics, such as calcium carbonate, is used to create a resin composition that is free from coarse particles and conductive impurities, ensuring uniform pore distribution and improved insulation properties when used in uniaxial or biaxial stretching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separator is made thin to improve ion permeation and reduce inner resistance, then the ion permeation increases, but the mechanical strength and insulating property deteriorate
Solution Approach 1:
The patent employs a porous resin film with specifically controlled pore structure (average pore diameter 0.01-10 μm, porosity 30-80%) to achieve high ion permeation while maintaining mechanical integrity. The porous structure allows efficient ion transport through the separator without requiring excessive thinning, thus resolving the contradiction between ion permeation and mechanical strength.
Solution Approach 2:
The patent uses composite resin compositions combining multiple polymer materials (e.g., polyolefin blends, copolymers) to create a separator that simultaneously provides mechanical strength, chemical stability, and controlled porosity. The composite structure enables the separator to maintain strength at reduced thickness while ensuring adequate ion permeation.
2Device complexity
If conventional porous films are used to reduce manufacturing complexity, then the production process is simpler, but coarse particles and conductive impurities cause short circuits and reliability issues
Solution Approach 1:
The patent specifies precise parameter ranges for inorganic particles (average diameter 0.1-10 μm, maximum diameter not exceeding 50 μm, resistivity ≥10^5 Ω·cm) to eliminate conductive impurities and coarse particles that cause short circuits. By controlling these parameters, the patent achieves reliable electrical insulation while maintaining a relatively simple production process using standard extrusion and stretching equipment.
3Reliability
If the porosity is increased to improve ventilation property and reduce inner resistance, then the ion permeation improves, but the mechanical strength deteriorates
Solution Approach 1:
The patent optimizes the porous structure with controlled pore size distribution (bimodal or multimodal pore structures) and porosity (30-80%) to achieve high ventilation property while maintaining mechanical strength. The specific pore size range (0.01-10 μm average diameter) allows efficient ion transport without creating large voids that would compromise structural integrity.
4Ease of manufacture
If the pore size distribution is widened to improve manufacturing ease, then the production is simpler, but the inner resistance increases due to uneven pore distribution
Solution Approach 1:
The patent controls the pore size distribution parameters (average diameter 0.01-10 μm, standard deviation ≤5 μm) to ensure uniform pore distribution throughout the separator. This controlled parameter range prevents localized variations in pore size that would create resistance pathways, thereby maintaining low inner resistance while using straightforward extrusion and stretching processes.
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 effectively reduces the inner resistance of lithium secondary batteries, enhances the durability and porosity of the porous resin film, and prevents short circuits, making it suitable for high-performance battery separators.
Implementation Method 1
a fine pore formation agent for giving a porous resin film which is suitable for uses for electric parts such as capacitors and battery separators and a composition containing the fine pore formation agent for a porous resin film, since inorganic particles composing the fine pore formation agent for a porous film of the present invention scarcely contain coarse particles and thus prevent strength deterioration of the porous resin film, are capable of making the distribution width of the void diameter of the porous film uniform and controlling the void diameter
Implementation Method 2
a battery separator is required to be thinner and have a high porosity and high ventilation property, in addition to the electrically insulating property for both electrodes
Implementation Method 3
since as the ion permeation is higher, the inner resistance is decreased and the properties of the battery are improved
Implementation Method 4
it is also very important that a separator for lithium secondary batteries is provided with a shut down function for stopping the battery reaction by increasing the temperature of the inside of the battery and thereby melting the resin and shutting its pores
Data Source
AI summary
A fine pore formation agent for a porous resin film is provided which comprises inorganic particles satisfying (a) 0.1≦D50≦1.5 (μm) (D50: average particle diameter of particles in 50% cumulative total by weight from the larger particle side by micro-track FRA), (b) Da≦20 (μm) (Da: maximum particle diameter by micro-track FRA), (c) 3≦Sw≦60 (m2/g) (Sw: BET specific surface area measured by nitrogen adsorption method), (d) Ir≧1.0×105 (Ω·cm) (Ir: volume resistivity (Ω·cm).The fine pore formation agent for a porous resin film is capable of providing a resin composition giving a porous resin film useful in uses for electric parts such as capacitors and battery separators.