Binder-Free Separator Coating for Battery Safety
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Solution Overview
Problem
Current composite separators for batteries face issues such as particle agglomeration, inhomogeneous component distribution, poor wettability, increased thickness leading to decreased energy density, and safety concerns due to ceramic layer defects, along with poor bonding properties at the electrode interface, resulting in reliability and safety problems.
Innovation Solution
A separator with a porous inorganic layer and an organic particle coating layer, where the inorganic layer is binder-free and formed by vapor deposition, and the organic particle coating layer is discontinuously distributed to enhance interface stability and ion transmission, providing protection and available space for electrode expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic coating is applied on both sides of the substrate to improve safety performance, then thermal shrinkage resistance is improved, but separator thickness increases by at least 50%, resulting in decreased energy density
Solution Approach 1:
The patent applies ceramic coating selectively on only one side of the porous substrate rather than both sides, creating local differentiation in coating distribution. This local quality approach provides thermal shrinkage resistance where most needed while avoiding unnecessary thickness increase on the other side, thus improving safety performance without proportionally increasing overall separator thickness and energy density loss.
Solution Approach 2:
The patent uses a thin ceramic coating layer with controlled thickness that provides sufficient thermal shrinkage resistance without applying excessive coating material. This partial action principle ensures that the ceramic layer is thick enough to prevent thermal shrinkage but thin enough to minimize the increase in separator overall thickness and maintain energy density.
2Reliability
If ceramic coating is applied to improve thermal shrinkage resistance, then safety performance is improved, but particle agglomeration and inhomogeneous distribution occur in the coating
Solution Approach 1:
The patent introduces a surfactant as an intermediary substance in the ceramic slurry formulation. This surfactant acts as a mediator between the ceramic particles and the slurry medium, improving particle dispersion and preventing agglomeration during the coating process. The surfactant ensures homogeneous distribution of ceramic particles in the coating layer, achieving uniform coating quality while maintaining thermal shrinkage resistance.
Solution Approach 2:
The patent optimizes the composition parameters of the ceramic slurry, including ceramic particle size distribution, binder content, and surfactant concentration, to achieve optimal coating uniformity. By carefully controlling these parameters, the patent prevents particle agglomeration and ensures homogeneous ceramic particle distribution in the coating layer while maintaining the desired thermal shrinkage resistance properties.
3Strength
If binder is used to bond ceramic layer to substrate, then coating adhesion is improved, but binding force varies in different areas leading to cracks and detachment
Solution Approach 1:
The patent ensures homogeneous distribution of binder and surfactant throughout the ceramic slurry, which leads to uniform binding force across the entire coating area. This homogeneity in material distribution prevents localized weak points that would otherwise cause cracks and detachment, ensuring consistent coating adhesion and integrity across the substrate surface.
Solution Approach 2:
The surfactant acts as an intermediary that enhances the compatibility and bonding between the binder and ceramic particles, as well as between the coating and substrate. This intermediary substance ensures uniform adhesion properties across the coating, preventing areas of weak bonding that could lead to cracks and detachment during battery operation.
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 achieves high wettability, low thermal shrinkage, excellent ion-transmission performance, and improved durability, leading to enhanced cycling performance and long-term reliability of the electrochemical device.
Implementation Method 1
The porous inorganic layer according to the present disclosure includes an inorganic dielectric material containing no binder
Implementation Method 2
a separator is usually is a porous polymer film having characteristics of electron isolation and ion conduction, by which ions can be normally transferred between positive and negative electrodes
Implementation Method 3
The organic particle coating layer is an island-like or sheet-like coating discontinuously distributed on a surface of the porous inorganic layer
Data Source
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AI summary
The present disclosure relates to the field of energy storage, and in particular to a separator and an electrochemical device including the separator. The separator includes a porous substrate. At least one of a porous inorganic layer and an organic particle coating layer is provided on at least one surface of the porous substrate, and a composite layer is provided on at least one surface of the porous substrate. The composite layer includes a porous inorganic layer and an organic particle coating layer sequentially disposed on the surface of the porous substrate. The porous inorganic layer includes an inorganic dielectric material containing no binder. The organic particle coating layer is a coating discontinuously distributed on the porous inorganic layer. The composite layer has a mass of 0.2 g/m2 to 8.4 g/m2 per unit area.