Lithium Battery Separator Coating for Uniform Adhesion and Bending Strength
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Solution Overview
Problem
Existing separators for lithium secondary batteries face challenges with heat shrinkage and poor physical durability due to non-uniform coatings of inorganic particles and polymer binders, leading to potential deformation and explosion risks.
Innovation Solution
A separator design with a first layer of inorganic particles having a reduced surface roughness and improved packing density, combined with a second layer of polymer binder particles, where the average particle diameters are carefully controlled to enhance adhesion and bending strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic particles and binder are coated simultaneously and consecutively in two layers, then heat resistance and safety are improved, but uniform coating of binder slurry on wet inorganic particles becomes difficult
Solution Approach 1:
The coating process is divided into two separate sequential steps: first coating inorganic particles, drying to form a porous layer, then coating polymer binder particles. This segmentation allows each layer to be optimized independently, achieving both heat resistance and uniform coating.
Solution Approach 2:
The inorganic particle layer is prepared and dried in advance before binder coating. This preliminary action creates a stable, porous substrate that facilitates uniform binder penetration and coating, resolving the difficulty of coating on wet inorganic particles.
2Ease of manufacture
If separator uses polyolefin-based fabric substrate, then basic separator function is provided, but heat shrinkage and poor physical durability occur at high temperatures
Solution Approach 1:
The separator combines polyolefin-based fabric substrate with inorganic particles (alumina, boehmite, etc.) and polymer binder to create a composite structure. This composite material maintains the flexibility and basic function of the fabric while adding heat resistance and physical durability from the inorganic components.
Solution Approach 2:
The physical and chemical parameters of the separator are modified by adding inorganic particles and binder coating layers, changing its thermal stability and mechanical strength parameters while retaining the base fabric's functional properties.
3Reliability
If inorganic particles layer is coated to improve heat resistance, then safety is enhanced, but surface roughness increases making uniform binder coating difficult
Solution Approach 1:
The inorganic particles are distributed with controlled local density and size distribution to create a surface that maintains heat resistance while providing sufficient uniformity for binder coating. The particle size and concentration are locally optimized to balance roughness and thermal properties.
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 improved separator design achieves enhanced adhesion between the separator and electrodes, resulting in increased bending strength and capacity per volume of the lithium secondary battery.
Implementation Method 1
an average particle diameter (D50) of the inorganic particles is less than 300 nm
Implementation Method 2
improving adhesion between the separator and electrodes by implementing a uniform coating between a first layer including inorganic particles and a second layer including polymer binder particles
Implementation Method 3
separators that not only serve as interposed membranes that isolate a positive electrode and a negative electrode from each other in a battery and continuously maintain ionic conductivity
Data Source
AI summary
Provided are a separator for a lithium secondary battery, a lithium secondary battery including the same, and a method of preparing the separator for a lithium secondary battery. The separator for a lithium secondary battery includes: a substrate; a first layer disposed on a surface of the substrate and consisting of inorganic particles; and a second layer disposed on the first layer and consisting of polymer binder particles, wherein an average particle diameter of the inorganic particles is less than 300 nm, and an average particle diameter of the polymer binder particles is 200 nm to 500 nm. The separator, due to reduced surface roughness and improved packing density of the first layer consisting of the inorganic particles, may have a uniform coating. The lithium secondary battery including the separator may have improved adhesion between the separator and electrodes, and thus the lithium secondary battery may have improved bending strength.