Separator Coating for Lithium-Ion Battery Thermal Stability
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Solution Overview
Problem
Existing separators for lithium secondary batteries face challenges in achieving high packing density and bindability to both the porous substrate and electrodes, which affects the stability and capacity of the battery, while also being prone to thermal shrinkage and mechanical stress.
Innovation Solution
A separator with a porous organic-inorganic coating layer formed by a mixture of inorganic particles and a first binder polymer containing a specific copolymer, along with an organic coating layer, is used to enhance binding properties and maintain stability, allowing for the fabrication of thin batteries without increased resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the content of inorganic particles in the porous organic-inorganic coating layer is increased to inhibit thermal shrinkage, then thermal stability is improved, but bindability to electrodes deteriorates and inorganic particles separate during fabrication
Solution Approach 1:
The patent introduces a binder polymer as an intermediary substance between inorganic particles and electrodes. The binder polymer contains functional groups that chemically interact with both the inorganic particles and the electrode surface, creating a bridging effect that prevents particle separation while maintaining thermal stability. This mediator enables the system to achieve both high inorganic particle content and good bindability simultaneously.
Solution Approach 2:
The patent creates a composite coating layer structure combining inorganic particles, binder polymer, and porous substrate. This composite material approach allows the system to leverage the thermal stability of inorganic particles while the organic binder polymer provides adhesion and flexibility. The synergistic combination resolves the contradiction between particle content and bindability.
2Object-affected harmful factors
If a porous organic-inorganic coating layer is formed to prevent thermal shrinkage, then safety is improved, but device complexity increases
Solution Approach 1:
The binder polymer is pre-synthesized with specific functional groups designed to interact with both inorganic particles and electrodes. This preliminary preparation of the binder with dual functionality simplifies the overall fabrication process by eliminating the need for separate treatment steps to achieve both adhesion and thermal stability.
Solution Approach 2:
The patent optimizes parameters such as the molecular weight, functional group density, and composition ratio of the binder polymer to achieve optimal performance. By carefully controlling these parameters, the coating layer achieves effective thermal shrinkage prevention without requiring overly complex fabrication procedures.
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 provides a high packing density and improved bindability, resulting in reduced resistance and enhanced capacity, while preventing inorganic particle separation and maintaining stability against thermal and mechanical impacts.
Implementation Method 1
The inorganic particles present in the porous organic-inorganic coating layer coated on the porous substrate serve as spacers that can maintain a physical shape of the porous organic-inorganic coating layer to inhibit the porous substrate from thermal shrinkage when an electrochemical device overheats
Implementation Method 2
a first binder polymer containing a copolymer including (a) a first monomer unit including either at least one amine group or at least one amide group or both in the side chain thereof
Data Source
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AI summary
A separator includes a porous substrate, a porous organic-inorganic coating layer formed on at least one surface of the porous substrate, and an organic coating layer formed on the surface of the organic-inorganic coating layer. The porous organic-inorganic coating layer includes a mixture of inorganic particles and a first binder polymer. The first binder polymer contains a copolymer including (a) a first monomer unit including either at least one amine group or at least one amide group or both in the side chain thereof and (b) a (meth)acrylate having a C1-C14 alkyl group as a second monomer unit. The organic coating layer is formed by dispersing a second binder polymer on the surface of the organic-inorganic coating layer, leaving scattered uncoated areas. The porous organic-inorganic coating layer of the separator has a high packing density, enabling the fabrication of a thin battery in an easy manner without losing stability. The porous organic-inorganic coating layer has good ability to bind to the porous substrate, which prevents the inorganic particles from separating from the porous organic-inorganic coating layer. In addition, the organic coating layer enhances the bindability of the separator to an electrode without a substantial increase in resistance.