Electrode-Integrated Separator Coating for Pinhole-Resistant Bonding
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Solution Overview
Problem
Existing separators for lithium secondary batteries face issues with insufficient adhesion to electrodes, thermal instability, and mechanical weakness, leading to defects such as pinholes and micro-short circuits.
Innovation Solution
A method involving the sequential application of a binder solution and a slurry containing a second polymer binder and inorganic fine particles onto an electrode substrate, with the binder solution having a viscosity of 1000 cP to 9500 cP, to form a binder coating layer and a porous layer, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a separator consisting of a substrate and an inorganic coating layer is used, then ionic permeability and mechanical strength are improved, but adhesion to electrodes deteriorates due to material characteristics
Solution Approach 1:
The patent changes the chemical composition parameters of the coating layer by incorporating specific polymers (polyacrylic acid, polyacrylonitrile, carboxymethyl cellulose, or starch) with defined molecular weight ranges and concentrations. This parameter optimization enables the coating layer to achieve both mechanical strength and adhesion to electrodes simultaneously, resolving the contradiction between these two properties.
Solution Approach 2:
The patent creates a composite coating layer combining inorganic particles (alumina, silica, boehmite, or magnesia) with specific polymers in defined ratios. This composite structure provides the mechanical strength from inorganic particles while the polymer matrix ensures adhesion to electrodes, thus resolving the contradiction between strength and adhesion.
2Ease of manufacture
If polyolefin is used as the substrate, then manufacturing ease and cost are improved, but thermal stability deteriorates due to melting at high temperatures
Solution Approach 1:
The patent applies a composite coating layer containing inorganic particles (alumina, silica, boehmite, or magnesia) with specific surface area and pore size distribution over the polyolefin substrate. This coating provides high-temperature stability while the polyolefin substrate maintains manufacturing ease and cost-effectiveness, resolving the contradiction between ease of manufacture and thermal stability.
3Temperature
If the separator is configured only with an inorganic coating film by removing the substrate, then thermal stability is improved, but adhesion to electrodes and insulation deteriorate significantly
Solution Approach 1:
The patent creates a composite coating layer combining inorganic particles with specific polymers in defined ratios. The inorganic particles provide thermal stability while the polymer matrix ensures adhesion to electrodes and maintains insulation properties, thus resolving the contradiction between thermal stability and reliability.
Solution Approach 2:
The patent optimizes the local composition of the coating layer by controlling the size distribution (0.1-10 μm) and concentration of inorganic particles, creating regions with different properties: areas closer to electrodes have higher polymer content for adhesion, while other areas have higher inorganic content for thermal stability and insulation, resolving the multiple contradictory requirements.
4Device complexity
If the inorganic coating film is applied directly to the electrode substrate, then manufacturing simplicity is improved, but coating uniformity deteriorates due to electrode substrate state variations
Solution Approach 1:
The patent introduces a polymer matrix as an intermediary medium between the inorganic particles and the electrode substrate. This polymer matrix (polyacrylic acid, polyacrylonitrile, carboxymethyl cellulose, or starch) acts as a binding agent that ensures uniform distribution of inorganic particles and consistent coating quality regardless of electrode substrate variations, resolving the contradiction between manufacturing simplicity and coating uniformity.
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
This approach enhances interlayer bonding durability, minimizes defects like pinholes, and improves the mechanical strength of the separator, ensuring stable performance and safety in lithium secondary batteries.
Implementation Method 1
a binder solution containing a first polymer binder is applied onto an electrode substrate to form a binder coating layer
Implementation Method 2
a slurry containing a second polymer binder and inorganic fine particles is applied onto the binder coating layer to form a porous layer
Data Source
AI summary
The present invention relates to a method for manufacturing an electrode-integrated separator for lithium secondary batteries. According to the present invention, a method for manufacturing an electrode-integrated separator is provided, which can minimize defects such as pinholes while exhibiting excellent interlayer bonding durability.