AlN-Coated Battery Separator for Thin-Substrate Insulation
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Solution Overview
Problem
Lithium secondary battery separators face challenges with insufficient heat resistance, adhesive strength, and insulation performance, particularly when using thin porous polymer substrates, which can lead to electrode folding and increased interface resistance due to clumped inorganic particles.
Innovation Solution
A lithium secondary battery separator is developed with a structure that includes a porous polymer substrate coated with a first and second coating layer, each containing inorganic particles like aluminum nitride, and aqueous binder layers with different particle type binders, such as fluorine-based and acrylic-based binders, to enhance adhesive strength and insulation performance while maintaining a reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a thin porous polymer substrate (12 μm or less) is used to reduce separator thickness, then energy density is improved, but inorganic particles clump together and cause local pressing damage to the substrate, deteriorating insulation properties
Solution Approach 1:
The patent applies local quality by creating a porous coating layer with controlled pore structure and distributing inorganic particles uniformly within a polymer matrix. The coating layer has different local properties (porosity, particle distribution) compared to the bulk substrate, allowing thin substrates to maintain insulation performance by preventing particle clumping and local pressing damage through the porous structure that distributes stress.
Solution Approach 2:
The patent uses composite materials by combining inorganic particles (alumina, silica, titania, zirconia) with polymer materials (polyolefin, polyacrylonitrile, carboxymethyl cellulose) to form a porous coating layer. This composite structure prevents particle clumping while maintaining mechanical strength and insulation properties, enabling the use of thin substrates without compromising reliability.
2Temperature
If oil-based binder is used in porous coating layer to improve heat resistance, then thermal stability is improved, but adhesive strength between electrode and separator becomes insufficient, causing electrode folding and increased interface resistance
Solution Approach 1:
The patent applies parameter changes by transitioning from oil-based binders to water-based binder systems. This fundamental parameter change in the binder chemistry enables simultaneous achievement of heat resistance (through inorganic particles and polymer matrix) and adequate adhesive strength (through water-based binder properties), eliminating the trade-off between thermal stability and bonding strength.
3Strength
If high heat temperature and pressure are applied in hot press process to increase bonding strength, then adhesive strength is improved, but damage to thin separator substrate increases
Solution Approach 1:
The patent applies beforehand cushioning by forming a porous coating layer with polymer matrix and inorganic particles on the thin substrate before the hot press process. This coating layer acts as a protective cushion that distributes the applied heat and pressure, preventing local pressing damage to the thin substrate while still allowing sufficient bonding strength to be achieved through the controlled porous structure.
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 separator achieves improved heat resistance, adhesive strength, and insulation performance, allowing for bonding under alleviated heat and pressure conditions, preventing damage during the bonding process and maintaining uniform quality even after electrolyte injection.
Implementation Method 1
In order to enhance the thermal resistance characteristics of a porous polymer substrate, a separator has been developed in which a porous coating layer containing a binder polymer and inorganic particles is formed on a polymer substrate
Implementation Method 2
the separator is required to have a high ionic conductivity based on a high porosity to increase the transmission of lithium ions
Data Source
AI summary
A lithium secondary battery separator having excellent heat resistance, adhesive strength, and insulation performance is provided. A lithium secondary battery separator according to one aspect of the present disclosure includes a porous polymer substrate, a first coating layer on a first surface of the porous polymer substrate, a second coating layer on a second surface of the porous polymer substrate, a first aqueous binder layer on a surface of the first coating layer, and a second aqueous binder layer on a surface of the second coating layer. The first coating layer and the second coating layer each include inorganic particles and a coating layer binder, in which the inorganic particles include aluminum nitride (AlN). The first aqueous binder layer and the second aqueous binder layer include different types of particle-type binders. The particle-type binder includes at least one selected from fluorine-containing binders and acrylic-containing binders.