Patterned Separator Coating for Fast Electrolyte Impregnation
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Solution Overview
Problem
Lithium ion batteries face safety issues due to thermal shrinkage of porous polyolefin separators, leading to potential short circuits and slow electrolyte impregnation, which complicates the fabrication of electrochemical devices and increases the risk of thermal runaway or explosion.
Innovation Solution
A separator with a porous organic-inorganic coating layer featuring a continuous or discontinuous patterned layer with grooves, using polyolefin substrates and inorganic particles with high dielectric constants or lithium ion transport capabilities, along with a binder polymer, to enhance electrolyte impregnation and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a porous organic-inorganic coating layer is formed on the separator, then heat resistance is improved, but electrolyte impregnation time increases
Solution Approach 1:
The coating layer is divided into multiple layers with different functions: a lower layer containing inorganic particles for heat resistance and an upper organic layer for electrolyte affinity. This segmentation allows each layer to optimize its specific function without compromising the other, resolving the contradiction between heat resistance and impregnation speed.
Solution Approach 2:
The separator uses a composite structure combining inorganic particles (for thermal stability) with organic binder polymers (for electrolyte wettability). This composite material approach integrates the advantages of both materials, achieving simultaneous heat resistance and fast electrolyte impregnation.
2Ease of manufacture
If a porous polyolefin substrate is used as separator, then manufacturing is simplified, but thermal shrinkage causes safety issues at high temperatures
Solution Approach 1:
Inorganic particles are incorporated into the polyolefin substrate to create a composite separator that maintains the ease of manufacturing polyolefin while adding thermal stability. The inorganic particles prevent thermal shrinkage at high temperatures, thus improving safety without significantly complicating the manufacturing process.
Solution Approach 2:
The separator maintains a porous structure that allows electrolyte penetration while the inorganic particles provide thermal stability. The porous design ensures that the separator remains permeable to electrolytes while the inorganic reinforcement prevents collapse or shrinkage at elevated temperatures, addressing both manufacturing ease and high-temperature safety.
3Reliability
If the separator structure is modified to improve electrolyte impregnation, then wettability increases, but structural integrity may be compromised
Solution Approach 1:
The dual-layer coating structure combines materials with complementary properties: the inorganic particle layer provides structural reinforcement and thermal stability, while the organic binder layer ensures good electrolyte wettability. This composite approach improves wettability without compromising structural integrity, as each material compensates for the other's limitations.
Solution Approach 2:
Different regions of the separator surface are given different properties: the inorganic particle-rich lower layer provides structural strength and heat resistance, while the organic polymer-rich upper layer provides enhanced wettability. This local differentiation of material properties allows simultaneous optimization of structural integrity and electrolyte impregnation.
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 improves the wettability and impregnation speed of the electrolyte solution, reducing the risk of thermal runaway and enhancing the safety and performance of lithium secondary batteries by creating a more efficient and heat-resistant separator.
Implementation Method 1
inorganic particles with high dielectric constants or lithium ion transport capabilities
Implementation Method 2
significantly improves the wettability and impregnation speed of the electrolyte solution
Implementation Method 3
a porous coating layer into which a continuous or discontinuous patterned layer is introduced to allow an electrolyte solution to permeate therethrough
Implementation Method 4
a porous polyolefin substrate commonly used as a separator of a lithium secondary battery undergoes extreme thermal shrinkage at a temperature of 100 °C or higher
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Disclosed is a separator. The separator includes a porous substrate, and a porous coating layer formed on at least one surface of the porous substrate and including a mixture of inorganic particles and a binder polymer. A continuous or discontinuous patterned layer is formed on the surface of the porous coating layer to allow an electrolyte solution to permeate therethrough. The continuous or discontinuous patterned layer may be formed with continuous grooves to allow an electrolyte solution to permeate therethrough. Due to this structure, the wettability of the separator with an electrolyte solution is improved, shortening the time needed to impregnate the electrolyte solution into the separator.