Battery Separator Porous Layer for Ion Conductivity and Heat Resistance
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Solution Overview
Problem
Current separators for lithium-ion batteries face issues with ion conductivity, heat resistance, and metal impurity content, leading to potential durability and safety concerns, particularly with the use of metal oxide and hydrophilic fillers which can cause side reactions, aggregation, and reduced insulation at elevated temperatures.
Innovation Solution
A separator with a porous layer comprising a polyolefin resin and a surface-treated ionic compound, where the ionic compound is treated with saturated or unsaturated fatty acids, has a specific weight content and surface hydrophilicity, enhancing ion conductivity and heat resistance while minimizing metal impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metal oxide fillers (alumina, magnesia, titanic) are used to enhance heat resistance, then heat resistance is improved, but side reactions occur inside the electricity storage device reducing durability
Solution Approach 1:
The patent removes metal oxide fillers from the separator composition entirely, replacing them with metal sulfate fillers. This extraction of the harmful component (metal oxide) eliminates the source of side reactions while maintaining the heat resistance function through alternative materials with higher thermal stability.
Solution Approach 2:
The patent creates a composite separator structure combining polyolefin resin with metal sulfate fillers (such as barium sulfate, strontium sulfate, or calcium sulfate). This composite approach achieves heat resistance through the high melting point of metal sulfates while the polyolefin matrix provides ion conductivity and structural integrity, avoiding the durability issues associated with metal oxide fillers.
2Reliability
If hydrophilic fillers are used to improve ion conductivity, then ion conductivity is enhanced, but filler aggregation occurs reducing manufacturing precision
Solution Approach 1:
The patent changes the surface properties of metal sulfate fillers by controlling their particle size (0.1 to 10 micrometers) and surface treatment to achieve optimal hydrophobicity. This parameter adjustment prevents excessive hydrophilicity that causes aggregation while maintaining sufficient ion conductivity, resulting in uniform filler distribution throughout the separator.
Solution Approach 2:
The patent applies local quality control by treating the filler particles with specific surface modifications that create optimal local hydrophobicity. This ensures that individual filler particles maintain good dispersion without aggregating, while the overall separator structure provides the necessary ion conductivity through controlled porosity and electrolyte distribution.
3Reliability
If polyethylene resin is used as base material, then ion conductivity is achieved, but heat resistance is insufficient at temperatures above melting point
Solution Approach 1:
The patent creates a composite structure where polyolefin resin provides the ion-conductive matrix and metal sulfate fillers provide thermal stability. The metal sulfate particles act as heat-resistant spacers that maintain separator structure at elevated temperatures, preventing collapse and maintaining insulation properties above the polyethylene melting point while preserving ion conductivity pathways.
Solution Approach 2:
The patent utilizes a porous separator structure where the polyolefin matrix forms interconnected pores filled with electrolyte. This porous architecture maintains ion conductivity through the electrolyte-filled channels while the rigid metal sulfate filler particles provide structural support that prevents pore collapse at high temperatures, maintaining both ion conductivity and 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 ion conductivity, heat resistance, and safety characteristics, reducing the risk of internal short circuits and abnormal heating, while maintaining high energy density and durability.
Implementation Method 1
wherein the degree of surface hydrophilicity of the ionic compound is 0.10 or more and 0.80 or less
Implementation Method 2
allowing ion conduction through an electrolytic solution held in microporous pores of the separator
Implementation Method 3
to prevent electron conduction due to direct contact or short circuit between the positive and negative electrodes
Data Source
AI summary
This separator for a power storage device has a porous layer containing a polyolefin resin and surface-treated ionic compound. The ionic compound content of the porous layer is 5 to 99 mass %, and the degree of surface hydrophilicity of the ionic compound is 0.10 to 0.80.