Thin Battery Separator Coating for Low-Voltage Defect Reduction
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Solution Overview
Problem
The increasing demand for eco-friendly energy has led to a challenge in reducing the low-voltage defective rate in electrochemical devices, particularly in electric vehicle batteries, due to the thinning of separators, which results in voltage drop and requires a solution that maintains heat resistance and adhesion while minimizing battery discard.
Innovation Solution
A separator with a porous substrate and an inorganic particle layer using a water-soluble binder, including a (meth)acrylamide-based monomer polymerization unit, is developed, where the dielectric breakdown voltage to thickness ratio (BDV/t) is optimized, and the inorganic particle layer is applied on at least one surface with a specific packing density and particle size distribution, enhancing adhesion and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the separator is thinned to achieve high capacity and output characteristics, then the device size and weight are reduced, but the low-voltage defective rate increases
Solution Approach 1:
The patent applies composite materials by combining an inorganic particle layer (containing ceramic particles such as Al2O3, SiO2, or TiO2) with a polymer binder on the porous substrate. This composite structure enhances the separator's mechanical strength and electrical insulation properties, allowing thin separators to maintain high reliability and resist low-voltage defects while keeping thickness minimal for high capacity and output characteristics.
Solution Approach 2:
The patent utilizes porous materials by employing a porous substrate (such as polyolefin or aromatic polyamide) with controlled porosity. The porous structure provides adequate ion transport pathways even at reduced thickness, maintaining electrochemical performance while the inorganic particle layer reinforces the mechanical and electrical properties to prevent low-voltage defects.
2Productivity
If the separator is thinned to reduce battery size, then productivity and capacity are improved, but heat resistance deteriorates
Solution Approach 1:
The inorganic particle layer containing ceramic particles (Al2O3, SiO2, TiO2) with specific surface areas (5-50 m²/g) provides exceptional heat resistance to the thin separator. The ceramic particles have high thermal stability and form a heat-resistant network that prevents thermal runaway and maintains structural integrity at elevated temperatures, enabling thin separators to achieve both high capacity and excellent heat resistance.
Solution Approach 2:
The patent optimizes parameters by controlling the particle size distribution (D50: 0.5-5 μm, surface area: 5-50 m²/g) and packing density of inorganic particles, as well as the binder content (1-10 wt%). These parameter optimizations ensure the inorganic layer provides sufficient heat resistance while maintaining thin overall thickness for high battery capacity and productivity.
3Power
If the separator is thinned to increase output characteristics, then device performance is improved, but adhesion to electrodes deteriorates
Solution Approach 1:
The composite inorganic particle layer with polymer binder creates a multi-functional interface that enhances adhesion between the separator and electrodes. The inorganic particles provide mechanical interlocking and chemical bonding sites, while the polymer binder ensures flexible adhesion, collectively strengthening the separator-electrode interface even when the separator is thinned for high output characteristics.
Solution Approach 2:
The inorganic particle layer is applied locally on the separator surface (at least one surface, or both surfaces) with controlled thickness and packing density. This local reinforcement provides enhanced adhesion and mechanical strength precisely where needed at the electrode interface, without increasing the overall separator thickness, thereby maintaining high output characteristics while improving 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 high temperatures.
Implementation Method 1
an inorganic particle layer including a binder and inorganic particles on at least one surface of the porous substrate
Implementation Method 2
maintains excellent heat resistance
Implementation Method 3
a porous substrate
Data Source
AI summary
Provided are a separator, a method of manufacturing the separator, and an electrochemical device including the separator. According to an 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 (1)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 (μm) of the separator.