Separator Coating Method for Lithium Ion Battery Thermal Stability
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Solution Overview
Problem
Lithium ion batteries face safety issues such as fire and explosion due to thermal shrinkage of porous polyolefin substrates, and the use of excessive binder polymers in separators can deteriorate the performance of electrochemical devices during the adhesion process.
Innovation Solution
A method involving a porous substrate with a porous coating layer formed by a first slurry containing inorganic particles and a first binder polymer, and a second slurry with a second binder polymer, applied through a slot and slide section respectively, to create a thin layer for adhesion with electrodes without compromising thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a binder polymer is used in excessive amount to form a layer for adhesion with an electrode, then the adhesion performance is improved, but the performance of electrochemical devices is deteriorated
Solution Approach 1:
The patent applies local quality by creating distinct regions with different binder polymer concentrations: a first region with lower concentration (0.1-5 wt%) for maintaining porosity and ion transport, and a second region with higher concentration (5-20 wt%) for providing adhesion. This spatial differentiation resolves the contradiction by localizing the adhesion function to specific areas rather than uniformly increasing binder content throughout the separator.
Solution Approach 2:
The separator is segmented into multiple functional regions: a porous substrate layer, a porous coating layer with inorganic particles and low binder content, and a specific adhesion layer with higher binder content. This segmentation allows each layer to perform its specialized function - the porous layers maintain thermal stability and ion transport, while the adhesion layer provides bonding - thereby resolving the contradiction between adhesion strength and device performance.
2Stability of the object's composition
If a porous coating layer with inorganic particles is formed on the porous substrate to prevent thermal shrinkage, then the thermal stability is improved, but the complexity of the separator structure increases
Solution Approach 1:
The patent merges multiple functions into a single integrated porous coating layer: inorganic particles provide thermal stability by preventing shrinkage, while simultaneously serving as spacers to maintain pore structure. The binder polymer in this layer provides both structural integrity and adhesion capability. This merging reduces overall device complexity compared to having separate layers for each function.
Solution Approach 2:
The separator employs composite materials by combining inorganic particles (alumina, silica, titania) with organic binder polymers on the porous substrate. This composite structure achieves thermal stability through the inorganic phase while the organic phase provides flexibility and adhesion, resolving the contradiction between improved thermal stability and increased structural complexity.
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 method prevents inter-mixing of the coating layers, enhances adhesiveness to electrodes, and maintains the thermal stability of the separator, thereby improving the performance and safety of electrochemical devices.
Implementation Method 1
porous polyolefin substrates commonly used as separators for electrochemical devices undergo severe thermal shrinkage at a temperature of 100° C. or higher in view of their material characteristics and production processes including elongation
Implementation Method 2
it is favorable for a layer for adhesion with an electrode to be significantly exposed on the porous substrate layer of the separator for good adhesion with the electrode
Data Source
AI summary
The present invention refers to a method of preparing a separator, a separator prepared therefrom and an electrochemical device having the separator. The method of preparing a separator according to the present invention comprises providing a planar and porous substrate having multiple pores; and coating a first slurry on at least one surface of the porous substrate through a slot section to form a porous coating layer, while continuously coating a second slurry on the porous coating layer through a slide section adjacent to the slot section to form a layer for adhesion with an electrode, the first slurry comprising inorganic particles, a first binder polymer and a first solvent, and the second slurry comprising a second binder polymer and a second solvent.