Lithium Ion Battery Separator Substrate Fibrillation Control
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Solution Overview
Problem
Lithium ion battery separators face challenges with high adhesion to inorganic particle layers, tensile strength, and cuttability, particularly when containing high amounts of heat-resistant fibers, which can lead to thermal runaway and short circuits in large-sized batteries.
Innovation Solution
A substrate for lithium ion battery separators comprising fibrillated heat-resistant fibers with a modified freeness of not more than 300 ml, and synthetic resin short fibers, where the content of fibrillated heat-resistant fibers is between 1.0% to 5.0% and synthetic resin short fibers is greater than 90.0%, enhancing adhesion and cuttability while maintaining tensile strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the content of heat-resistant fibers is increased to enhance heat resistance, then the heat resistance of the separator is improved, but the substrate becomes difficult to smash and reduce thickness, and the tensile strength decreases
Solution Approach 1:
The patent changes the physical and chemical parameters of heat-resistant fibers by controlling their fibrillation degree (freeness) to a specific range of 100-300 ml. This parameter optimization allows the fibers to provide adequate heat resistance while maintaining substrate smashability and tensile strength, resolving the contradiction between heat resistance and mechanical properties
Solution Approach 2:
The patent creates a composite fiber structure by combining heat-resistant fibers with synthetic resin short fibers in a specific ratio (heat-resistant fibers: 1-10 mass%, synthetic resin short fibers: 90-99 mass%). This composite approach balances the heat resistance provided by heat-resistant fibers with the mechanical strength and processability contributed by synthetic resin fibers
2Temperature
If the content of heat-resistant fibers is increased to improve heat resistance, then the thermal stability is enhanced, but the substrate cuttability deteriorates
Solution Approach 1:
The patent optimizes the freeness parameter of heat-resistant fibers to 100-300 ml, which controls the fiber's flexibility and bonding characteristics. This parameter adjustment enables the substrate to be heat-resistant while remaining cuttable during the slitting process, resolving the contradiction between thermal stability and manufacturability
3Temperature
If the content of heat-resistant fibers is increased to enhance heat resistance, then the thermal stability is improved, but the adhesion to inorganic particle layer decreases
Solution Approach 1:
The patent adjusts the freeness of heat-resistant fibers to a specific range (100-300 ml) that optimizes surface properties and bonding capacity. This parameter control ensures that the substrate maintains good adhesion to the inorganic particle layer while providing adequate heat resistance
Solution Approach 2:
The composite fiber structure combining heat-resistant fibers (1-10 mass%) with synthetic resin short fibers (90-99 mass%) creates a balanced substrate that provides both heat resistance and sufficient surface adhesion properties for bonding with inorganic particle layers
4Temperature
If the content of heat-resistant fibers is increased to improve heat resistance, then the thermal stability is enhanced, but the internal resistance increases
Solution Approach 1:
The patent optimizes the freeness parameter of heat-resistant fibers to control pore structure and ion transport properties. By setting freeness to 100-300 ml, the substrate achieves heat resistance while maintaining low internal resistance for efficient ion conduction
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 substrate achieves high adhesion to inorganic particle layers, excellent cuttability, and reduced internal resistance, preventing thermal runaway and improving the safety and performance of lithium ion batteries.
Implementation Method 1
The substrate achieves high adhesion to inorganic particle layers
Implementation Method 2
reduced internal resistance
Data Source
AI summary
It is an object of the present invention to provide a substrate for lithium ion battery separators which has high adhesion to an inorganic particle layer, can be made thin and is excellent in tensile strength and cuttability and a lithium ion battery separator including the substrate for lithium ion battery separators. The substrate for lithium ion battery separators which contains heat-resistant fibers and synthetic resin short fibers contains fibrillated heat-resistant fibers having a modified freeness of not more than 300 ml as the heat-resistant fibers and has a content of the fibrillated heat-resistant fibers having a modified freeness of not more than 300 ml of not less than 1.0 mass % to less than 5.0 mass % based on the total of all the fiber components contained in the substrate. The modified freeness is a value measured in accordance with JIS P8121-2:2012 except that an 80-mesh wire net having a wire diameter of 0.14 mm and an opening of 0.18 mm is used as a screening plate and the concentration of a sample is 0.1%.