Separator Manufacturing via Dual-Binder Phase Separation
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Solution Overview
Problem
Existing separators for electrochemical devices face issues with inorganic particle separation during manufacturing, leading to reduced bindability and increased safety risks due to thermal shrinkage and potential short circuits, which affects the performance and safety of the devices.
Innovation Solution
A method for manufacturing a separator with a porous coating layer composed of inorganic particles and binder polymers, where a slurry containing inorganic particles and a mixture of first and second binder polymers is coated on a porous substrate, with a non-solvent promoting phase separation to enhance surface distribution of the second binder polymer, thereby improving bindability and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the content of inorganic particles in the porous coating layer is increased to maintain physical shape and prevent thermal shrinkage, then thermal stability is improved, but bindability to electrodes deteriorates and inorganic particles separate during manufacturing
Solution Approach 1:
The patent uses a composite binder system comprising both a first binder polymer (polyvinylidene fluoride-co-hexafluoropropylene) and a second binder polymer (carboxymethyl cellulose or hydroxypropyl cellulose). This composite approach allows the first binder to provide strong adhesion to electrodes while the second binder maintains binding ability after solvent removal, resolving the contradiction between maintaining high inorganic particle content for thermal stability and ensuring sufficient bindability during manufacturing
Solution Approach 2:
The patent optimizes the weight ratio parameters of the binder polymers and inorganic particles, specifically setting the binder polymer content at 10-50 wt% and the weight ratio of first to second binder polymer between 9:1 and 1:9. These parameter adjustments enable the coating layer to maintain both thermal stability and bindability simultaneously
2Temperature
If the content of binder polymer is decreased to increase inorganic particle content, then thermal shrinkage resistance is improved, but manufacturing complexity increases due to particle separation
Solution Approach 1:
The dual-binder composite system prevents inorganic particle separation during manufacturing while allowing high inorganic particle content (50-90 wt%) for thermal shrinkage resistance. The synergistic interaction between the two binder polymers ensures particle suspension and coating layer integrity throughout the manufacturing process
Solution Approach 2:
The patent applies preliminary action by pre-dissolving both binder polymers in a solvent to form a homogeneous slurry before coating. This preliminary mixing ensures uniform distribution of inorganic particles and binder polymers, preventing separation during subsequent manufacturing steps while maintaining high inorganic particle content
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 method ensures high bonding strength between the separator and electrodes, preventing inorganic particle separation and enhancing the stability and safety of electrochemical devices by maintaining a sufficient content of inorganic particles in the coating layer.
Implementation Method 1
a non-solvent incapable of dissolving the second binder polymer is sequentially coated on the slurry through a second discharge hole adjacent to the first discharge hole; and the solvent and the non-solvent are simultaneously removed by drying, whereby a larger amount of the second binder polymer is present at the surface portion of the porous coating layer than the underlying portion
Data Source
Figure 1
AI summary
Disclosed is a method for manufacturing a separator. The method includes (S1) preparing a porous planar substrate having a plurality of pores, (S2) preparing a slurry containing inorganic particles dispersed therein and a polymer solution including a first binder polymer and a second binder polymer in a solvent, and sequentially coating the slurry on the porous substrate through a first discharge hole and a non-solvent incapable of dissolving the second binder polymer on the slurry through a second discharge hole adjacent to the first discharge hole, and (S3) simultaneously removing the solvent and the non-solvent by drying. According to the method, a separator with good bindability to electrodes can be manufactured in an easy manner. In addition, problems associated with the separation of inorganic particles in the course of manufacturing an electrochemical device can be avoided.