Composite Battery Separator Coating for Low-Voltage Defect Reduction
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Solution Overview
Problem
The increasing demand for eco-friendly energy sources has led to a challenge in reducing the low-voltage defective rate of batteries in electrochemical devices, particularly in electric vehicles, due to the thinning of separators, which results in voltage drop and requires a solution that maintains heat resistance and adhesion while minimizing defects.
Innovation Solution
A separator with a porous substrate and an inorganic particle layer using a water-soluble binder containing (meth)acrylamide-based monomer polymerization units, applied via a hydrophilically surface-treated substrate, which enhances adhesion and heat resistance, and controls the dielectric breakdown voltage to thickness ratio, thereby reducing the low-voltage defective rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the separator is thinned to achieve high capacity and output characteristics, then the energy density and power density are improved, but the low-voltage defective rate increases due to reduced withstand voltage capability
Solution Approach 1:
The separator is constructed as a composite material consisting of a porous substrate (polyolefin or aramid) combined with an inorganic particle layer (alumina, silica, or boehmite particles). This composite structure provides both the mechanical integrity needed for thin separators and the surface properties that enhance withstand voltage capability, thereby reducing low-voltage defects while maintaining thin profile for high energy density
Solution Approach 2:
The patent optimizes specific parameters including the inorganic particle size distribution ((D80-D20)/D50 value of 0.01 to 2.0), binder composition (water-soluble binder with specific functional groups), and layer thickness (inorganic particle layer thickness of 1-10 μm). These parameter optimizations enhance the separator's dielectric properties and surface characteristics, improving withstand voltage capability without increasing overall thickness
2Volume of stationary object
If the separator is thinned to reduce battery volume and increase capacity, then the volume energy density is improved, but the heat resistance deteriorates due to reduced thermal stability
Solution Approach 1:
The combination of organic porous substrate with inorganic particle coating creates a composite structure where the inorganic layer (alumina, silica, or boehmite) provides exceptional thermal stability and heat resistance. This allows the separator to maintain its structural integrity and shutdown function at elevated temperatures despite the reduced overall thickness, enabling thin-profile batteries with high volume energy density
Solution Approach 2:
The porous substrate structure (with porosity of 30-80%) provides both ion transport pathways for battery operation and thermal management capabilities. The porous structure allows heat dissipation while maintaining mechanical strength, and when combined with the inorganic particle layer, enhances thermal stability without requiring increased thickness
3Power
If the separator is thinned to enhance power density and output characteristics, then the power density is improved, but the adhesion to electrodes deteriorates due to reduced contact area
Solution Approach 1:
The patent optimizes the inorganic particle size distribution with a specific (D80-D20)/D50 value ratio of 0.01 to 2.0, which creates an optimized surface morphology that enhances contact with electrodes. The binder composition is also optimized with specific functional groups that improve interfacial adhesion. These parameter optimizations ensure strong electrode adhesion even with the reduced thickness required for high power density
Solution Approach 2:
The inorganic particle layer is applied specifically on the surface of the porous substrate that contacts the electrodes, creating a localized enhancement of surface properties. This surface layer provides improved wettability, adhesion, and interfacial contact area without significantly increasing the overall separator thickness, thereby maintaining high power density while improving electrode adhesion
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 significantly decreases the low-voltage defective rate, maintains excellent heat resistance, and improves adhesion, even with a thin separator, ensuring high capacity and output characteristics at elevated temperatures.
Implementation Method 1
an inorganic particle layer including a binder and inorganic particles on at least one surface of the porous substrate, wherein the binder is a water-soluble binder including a (meth)acrylamide-based monomer polymerization unit
Implementation Method 2
BDV/t wherein BDV is a voltage (kV) measured in accordance with ASTM D 3755, when a leakage current value is 5 mA, measured under conditions of raising an applied voltage at 5 kV/10 sec
Data Source
AI summary
Provided are a separator, a method of manufacturing the separator, and an electrochemical device including the separator. According to an exemplary embodiment, a separator including: a porous substrate; and an inorganic particle layer including a binder and inorganic particles on at least one surface of the porous substrate may be provided, wherein the binder is a water-soluble binder including a (meth)acrylamide-based monomer polymerization unit and the separator has a value of the following Formula (1) satisfying 0.15 or more: BDV/t wherein 'BDV' is a voltage (kV) measured in accordance with ASTM D 3755, when a leakage current value is 5 mA, measured under conditions of raising an applied voltage at 5 kV/10 sec after placing the separator between electrodes of a withstand voltage tester(Hipot Tester), and 't' is an overall average thickness (um) of the separator.