Double-Layer Cellulose Separator for Tear-Resistant Supercapacitors
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Solution Overview
Problem
Existing separators for electric double-layer capacitors face challenges such as low tear strength, increased leakage current, and reduced productivity due to high internal resistance and shedding of fibers during manufacturing.
Innovation Solution
A double-layer structured separator is manufactured using a method that involves refining regenerated cellulose fibers to specific Canadian Standard freeness (CSF) values for each layer, resulting in a fibrous layer A and fibrous layer B with optimized tensile and tear strength properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a separator made of 100% by mass refinable, regenerated cellulose fibers is used, then the separator has good shielding property and low leakage current, but the separator breaks in the manufacturing process due to low tear strength
Solution Approach 1:
The patent applies composite materials by combining regenerated cellulose fibers (70-100% by mass) with other fibers (0-30% by mass) to create a separator that maintains low leakage current while improving tear strength. The composite structure allows the separator to retain the excellent shielding properties of cellulose fibers while gaining mechanical strength from the additional fiber components.
Solution Approach 2:
The patent changes the physical and chemical parameters of the separator by controlling the fiber composition ratio, refining degree (CSF value), and physical properties (thickness, density). By adjusting these parameters, the separator achieves both low leakage current and sufficient tear strength for manufacturing processes.
2Reliability
If the internal resistance of the separator is reduced to improve cycle life, then the capacitance performance improves, but the manufacturing complexity increases due to demands for precise control of fiber refinement and layer structure
Solution Approach 1:
The patent reduces internal resistance by optimizing specific parameters: controlling fiber composition (70-100% regenerated cellulose), refining degree (CSF value), and physical properties (thickness 10-150 μm, density 0.25-0.65 g/cm³). These parameter optimizations improve cycle life while maintaining manufacturability through clear specification ranges.
Solution Approach 2:
The patent segments the separator into a multi-layer structure with different fiber compositions and refining degrees. This segmentation allows each layer to be optimized for specific functions (shielding, mechanical strength, ion permeability) while collectively achieving low internal resistance and improved cycle life.
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 proposed separator achieves excellent tensile strength and tear strength, enhancing the productivity of energy storage devices while maintaining low internal resistance and leakage current characteristics.
Implementation Method 1
a separator for an energy storage device, which is interleaved between a pair of polarizable electrodes and is capable of holding an electrolytic solution containing electrolyte
Implementation Method 2
density of the entire double layer structure is 0.25 to 0.65 g/cm³
Data Source
Figure 1
AI summary
A separator for an electric double-layer capacitor is provided having a double-layer structure made of a fibrous layer A obtained by papermaking using a Fourdrinier net or a tanmo net, and a fibrous layer B obtained by papermaking using a cylinder net. The fibrous layer A is a layer that is refined until a CSF value decreases once to 0ml (lower limit), and further refined until it turns to rise to 10 to 600ml, the fibrous layer B is a layer that is refined until a CSF value of 700 to 0ml, and the fibrous layer A and the fibrous layer B contain 70% by mass or more refinable, regenerated cellulose fibers. The density of the entire double-layer structure is 0.25 to 0.65 g/ cm3, and the thickness of the same is 10 to 150µm. This allows provision of a separator for an electric double-layer capacitor having excellent tensile strength and tear strength, provision of a degree of mechanical strength such that the separator does not break in a manufacturing process of a wound or a stacked type electric double-layer capacitor, and improvement of productivity without adversely affecting internal resistance and leakage current properties of the capacitor as an energy storage device.