Multilayer Microporous Polyolefin Membrane Oxidation Resistance
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Solution Overview
Problem
Multilayer, microporous polyolefin membranes used as battery separators face challenges in maintaining excellent oxidation resistance, electrolyte injection performance, and strength balance, particularly when high polypropylene content compromises permeability and strength.
Innovation Solution
A multilayer, microporous polyolefin membrane with a first microporous layer containing polypropylene, where the polypropylene distribution is uniform in the in-plane direction, and a method involving melt-kneading polyolefin resins with specific molecular weights and solvents, followed by extrusion, cooling, stretching, and solvent removal to achieve a balanced structure with optimized polypropylene and polyethylene ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polypropylene is added to improve oxidation resistance, then oxidation resistance is improved, but permeability and strength deteriorate
Solution Approach 1:
The patent applies local quality by creating a multilayer structure where the surface layer contains polypropylene for oxidation resistance while the base layer contains polyethylene for strength and permeability. This allows different regions of the membrane to have optimized properties for their specific functions, resolving the contradiction between oxidation resistance and mechanical strength.
Solution Approach 2:
The patent uses composite materials by combining polypropylene and polyethylene in a multilayer configuration. The surface layer uses polypropylene-containing resin for oxidation resistance, while the base layer uses polyethylene for mechanical properties, creating a composite structure that achieves both oxidation resistance and strength simultaneously.
2Reliability
If polypropylene content is increased to improve oxidation resistance, then oxidation resistance is improved, but permeability deteriorates
Solution Approach 1:
The patent applies local quality by concentrating polypropylene in the surface layer where oxidation resistance is needed, while keeping the base layer as polyethylene to maintain high permeability. This localized distribution allows the membrane to achieve oxidation resistance without sacrificing overall permeability.
Solution Approach 2:
The multilayer composite structure allows the polypropylene surface layer to provide oxidation resistance while the polyethylene base layer maintains permeability, resolving the contradiction between these two properties through material composition design.
3Reliability
If polypropylene is added to improve oxidation resistance, then oxidation resistance is improved, but electrolyte injection performance deteriorates
Solution Approach 1:
The patent applies local quality by placing the polypropylene-containing surface layer on the outside, allowing the electrolyte to first contact the polyethylene base layer which has better injection performance, while still gaining oxidation resistance from the polypropylene surface layer.
4Reliability
If polypropylene is added to improve oxidation resistance, then oxidation resistance is improved, but uniformity of polyethylene distribution deteriorates
Solution Approach 1:
The patent applies local quality by segregating polypropylene to the surface layer and polyethylene to the base layer, ensuring uniform polyethylene distribution in the base layer while still achieving oxidation resistance through the polypropylene surface layer.
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 membrane achieves excellent oxidation resistance, electrolyte injection performance, and strength balance, preventing deterioration during battery charging and discharging, thereby prolonging battery life and ensuring safety and productivity.
Implementation Method 1
a process of preparing a polyolefin solution by melt-kneading a polyolefin resin and a solvent for membrane formation
Implementation Method 2
a process of forming an extrudate by extruding the polyolefin solution
Implementation Method 3
a process of forming a gel-like sheet by cooling the obtained extrudate
Implementation Method 4
a process of producing a stretched body by stretching the obtained gel-like sheet
Implementation Method 5
a process of removing the solvent for membrane formation from the obtained stretched body
Data Source
AI summary
Provided is a microporous polyolefin membrane which has excellent oxidation resistance and electrolyte injection performance and further has excellent permeability and strength balance. The multilayer, microporous polyolefin membrane has a first microporous layer containing polypropylene. The electrolyte injection performance is 20 seconds or less, at least one surface layer is the first microporous layer, and the PP distribution in the first microporous layer is uniform in the in-plane direction.