Porous Battery Separator Coating for Adhesion and Air Permeability
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in maintaining high adhesion between the separator and electrodes, leading to reduced cycle-life and increased risk of lithium deposition and dead lithium layers, which affects battery performance and safety.
Innovation Solution
A separator with a porous substrate coated with a fluorine-containing binder and filler, where the fluorine-containing binder has a concentration gradient increasing towards the surface, and an additive with a carboxyl group is used, optimizing the crystallinity degree and molecular weight of the binder to enhance adhesion and air permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a separator with coating layer is used to improve adhesion between separator and electrodes, then adhesion force is improved, but air permeability deteriorates
Solution Approach 1:
The coating layer is designed with a porous structure containing voids that penetrate through the layer. This porous structure allows air and electrolyte to pass through while the coating material provides adhesion between the separator and electrodes, thus resolving the contradiction between adhesion force and air permeability
Solution Approach 2:
The coating layer comprises a composite of binder polymer and inorganic filler particles. The binder provides adhesive properties while the filler particles maintain structural integrity and porosity, enabling both good adhesion and air permeability simultaneously
2Reliability
If the separator structure is optimized to reduce lithium deposition, then battery safety is improved, but manufacturing complexity increases
Solution Approach 1:
The coating layer parameters are optimized including thickness (1-10 μm), porosity (30-70%), and composition ratios to prevent lithium deposition. By controlling these parameters within specific ranges, battery safety is improved while maintaining manufacturability through standardized production processes
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 improves adhesion between the separator and electrodes, reduces lithium deposition, and enhances cycle-life and safety by maintaining a balance between adhesion force and air permeability, thereby improving battery performance.
Implementation Method 1
improves adhesion between the separator and electrodes
Implementation Method 2
the additive includes a hydrocarbon polymer compound that includes a carboxyl group
Data Source
AI summary
A separator for a rechargeable battery includes a porous substrate; and a coating layer on the porous substrate, the coating layer includes a fluorine-containing binder, a filler, and an additive, the additive is included in an amount of 0.35 wt % to 1.25 wt %, an infrared spectral intensity of a C-F group of the fluorine-containing binder is greater than 0.0030 to less than 0.0050, the infrared spectral intensity of the C-F group of the fluorine-containing binder is measured as a functional group of the fluorine-containing binder to evaluate a distribution of the fluorine-containing binder when separator specimens are mounted on an ATR crystal of a FT-IR spectroscopy and infrared rays are entered at a 45 degree angle, the additive includes a hydrocarbon polymer compound that includes a carboxyl group, and the hydrocarbon polymer compound has a weight average molecular weight of about 5,000 g/mol to about 15,000 g/mol.