Thin Separator for Electrochemical Elements Using Beaten Cellulose
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Solution Overview
Problem
Existing separators for electrochemical elements face challenges in reducing thickness while maintaining chemical stability, resistivity, electrolyte solution impregnability, and retainability, as well as achieving high shielding properties, especially under high voltage and acidic environments.
Innovation Solution
A separator composed of beaten cellulose fibers and thermoplastic synthetic fibers, with a thickness of 5.0 to 30.0 μm and a density of 0.50 to 0.75 g/cm3, satisfying specific air resistance formulas to enhance shielding properties and prevent short-circuit failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of the separator is reduced to decrease the size of the electrochemical element, then the thickness is reduced, but the shielding property deteriorates and short-circuit resistance decreases
Solution Approach 1:
The separator is constructed as a composite material consisting of inorganic fine particles (such as aluminum oxide, aluminum hydroxide, or magnesium hydroxide) dispersed within a porous polymer matrix. This composite structure provides both the thin profile needed for miniaturization and the high shielding property required for short-circuit prevention, as the inorganic particles maintain structural integrity and blocking capability even at reduced thicknesses of 5.0 μm or less
Solution Approach 2:
The separator utilizes a porous polymer base material with controlled pore structure that allows electrolyte penetration while maintaining mechanical strength and shielding properties. The porous structure enables the separator to function effectively at extremely thin thicknesses by optimizing the balance between ion transport pathways and physical barrier properties, achieving both size reduction and maintained reliability
2Reliability
If the density of the separator is increased to improve the shielding property, then the shielding property is improved, but the resistivity increases and electrolyte solution impregnability deteriorates
Solution Approach 1:
The separator implements local quality differentiation through the distribution of inorganic fine particles within the porous polymer matrix. The inorganic particles are concentrated in regions requiring enhanced shielding and thermal stability, while the porous polymer structure maintains open pathways for electrolyte impregnation and ion transport. This spatial differentiation allows the separator to achieve high shielding property without compromising resistivity or impregnability
Solution Approach 2:
The separator optimizes the physical and chemical parameters of the porous polymer base material, including pore size distribution, porosity, and polymer composition, to achieve the desired balance between shielding property and electrolyte interaction. By carefully controlling these parameters, the separator achieves sufficient density for shielding while maintaining adequate porosity for electrolyte penetration and low resistivity
Data Source
AI summary
A thin separator for electrochemical elements, which has achieved chemical stability, while maintaining a good balance among short-circuit resistance, resistivity, electrolyte solution impregnability and electrolyte solution retainability of the separator. A separator for electrochemical elements, which is interposed between a pair of electrodes so as to separate the electrodes from each other, and which holds an electrolyte solution. This separator for electrochemical elements is composed of beaten cellulose fibers and thermoplastic synthetic fibers, and has a thickness of 5.0-30.0 μm and a density of 0.50-0.75 g/cm3; and the thickness X (μm) and the air resistance Y (second/100 ml) of this separator for electrochemical elements satisfy formula 1:Y≥0.01X2−0.6X+11.5.