High-Whiteness Battery Separator for Heat Resistance and Ion Flow
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Solution Overview
Problem
Existing separators for lithium ion batteries face challenges with heat resistance, durability, and safety due to polyethylene melting, metal oxide-induced deterioration, and potential reactions with electrolytic solutions, leading to issues like yellowing, voltage resistance concerns, and battery swelling.
Innovation Solution
A separator with a porous layer comprising a polyolefin resin and an ionic compound, where the ionic compound content is between 5% to 99% by weight and the degree of whiteness is greater than 98%, enhancing heat resistance and ion permeability while minimizing polyolefin deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a polyethylene microporous membrane is used as a base material for heat-resistant layer, then heat resistance is improved, but polyethylene melts and flows at elevated temperature causing loss of insulation
Solution Approach 1:
The patent uses a composite structure consisting of a heat-resistant base layer (made from heat-resistant resin or inorganic material) and a polyethylene microporous membrane layer. This composite structure allows the base layer to provide heat resistance while the polyethylene layer maintains insulation properties at operating temperatures, preventing the melting and flow problem of pure polyethylene.
Solution Approach 2:
The patent applies different material properties to different layers: the base layer is designed with high heat resistance properties to withstand elevated temperatures, while the polyethylene microporous membrane layer is optimized for ion permeability and insulation. This local differentiation of material qualities allows each layer to perform its specific function without compromising the other.
2Temperature
If metal oxide fillers are combined with polyolefin to enhance heat resistance, then heat resistance is improved, but polyolefin undergoes metal oxide-induced deterioration causing yellowing and voltage resistance issues
Solution Approach 1:
The patent removes the harmful metal oxide fillers from the separator structure and replaces them with a heat-resistant base layer made from heat-resistant resin or inorganic material. This extraction eliminates the source of metal oxide-induced deterioration while maintaining the heat resistance function through the alternative base layer design.
Solution Approach 2:
The heat-resistant base layer acts as an intermediary between the polyethylene microporous membrane and the high-temperature environment. It provides thermal stability and protects the polyethylene layer from direct exposure to elevated temperatures that would cause deterioration, while not introducing harmful metal oxide interactions.
3Temperature
If multiple processes are used to manufacture base material and form heat-resistant layer, then heat resistance is improved, but productivity decreases
Solution Approach 1:
The patent merges the base material manufacturing and heat-resistant layer formation into a single integrated structure. The heat-resistant base layer is formed as an integral part of the separator during the membrane fabrication process itself, eliminating the need for separate coating or lamination processes that would reduce productivity.
Solution Approach 2:
The heat-resistant base layer serves multiple functions simultaneously: it provides thermal stability, acts as a support structure for the microporous membrane, and enables the formation of the porous structure through interfacial stripping. This multi-functionality reduces the number of separate manufacturing steps required.
4Temperature
If inorganic filler and heat-resistant organic resin are used to form heat-resistant layer, then heat resistance is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the complex heat-resistant organic resin coating process and replaces it with a simplified heat-resistant base layer made from heat-resistant resin or inorganic material that is integrated into the membrane structure during fabrication. This reduces structural complexity while maintaining heat resistance.
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 provides a separator with improved heat resistance, ion permeability, and safety for lithium ion batteries, maintaining durability and preventing polyolefin deterioration, thus enhancing the reliability and safety of the battery.
Implementation Method 1
polyethylene resins such as high density polyethylene, soft polypropylene, etc., and barium sulfate (average particle size of 660 nm) as a filler are mixed, and the obtained mixture is stretched to strip at an interface between the resin and the filler, forming a porous membrane
Implementation Method 2
The separator is disposed between a positive electrode and a negative electrode to prevent electron conduction due to direct contact or short circuit between the positive and negative electrodes, while allowing ion conduction through an electrolytic solution held in microporous pores of the separator
Implementation Method 3
a polyolefin microporous membrane is generally used as a separator... allowing ion conduction through an electrolytic solution held in microporous pores of the separator
Implementation Method 4
The separator is disposed between a positive electrode and a negative electrode to prevent electron conduction due to direct contact or short circuit between the positive and negative electrodes
Data Source
AI summary
A separator for electricity storage devices, which comprises a porous layer that contains a polyolefin resin and an ionic compound, and which is configured such that: the content of the ionic compound in the porous layer is from 5% by mass to 99% by mass (inclusive); and the degree of whiteness of this separator is more than 98.0.