Composite-Coated Li-Ion Separator for Heat Shrinkage and Adhesion
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Solution Overview
Problem
Existing lithium ion battery separators made of polyolefin-based porous membranes have a low melting point, leading to potential short circuits during thermal runaway, and require improved bonding strength and ion conductivity to ensure safety and performance.
Innovation Solution
A ceramic-and-polymer-compositely-coated lithium ion separator is developed, featuring a polyolefin porous membrane with a ceramic coating on one or both sides and a polymer coating on the ceramic or membrane surface, enhancing heat resistance, bonding strength, and ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic layer is coated on the separator to reduce heat shrinkage and improve mechanical strength, then thermal safety is improved, but bonding strength with pole pieces and interfacial compatibility deteriorate
Solution Approach 1:
The patent applies composite materials by combining ceramic coating with polymer coating (PVDF, PMMA, or PAN) on the polyolefin separator. The ceramic layer provides thermal stability and heat shrinkage resistance, while the polymer coating layer enhances bonding strength with pole pieces and interfacial compatibility, creating a multi-functional composite structure that resolves the contradiction between thermal safety and bonding strength
Solution Approach 2:
The patent implements local quality by differentiating the functions of different coating layers: the ceramic layer specifically addresses thermal safety concerns, while the polymer coating layer specifically addresses bonding and interfacial compatibility requirements. This localized functional distribution allows each layer to optimize its specific property without compromising the other
2Temperature
If a ceramic layer is coated on the separator to reduce heat shrinkage, then heat resistance is improved, but ion conductivity and electrochemical performance deteriorate
Solution Approach 1:
The patent employs porous materials by incorporating porous polymer coating materials (PVDF, PMMA, or PAN) that maintain high ion conductivity through their porous structure. The porous structure allows efficient Li+ ion transport while the ceramic layer provides heat resistance, thus resolving the contradiction between thermal stability and ion conductivity
Solution Approach 2:
The composite structure combines the heat-resistant ceramic layer with the ion-conductive porous polymer coating, where each material contributes its superior property. The ceramic provides thermal stability while the porous polymer provides ion conductivity pathways, achieving both heat resistance and electrochemical performance simultaneously
3Strength
If a ceramic coating is applied to improve mechanical strength, then separator durability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by using slurry preparation and dip-coating methods that simplify the coating process. The ceramic slurry and polymer slurry are prepared in advance with appropriate viscosities and compositions, allowing straightforward dip-coating operations followed by drying and heat treatment, thus achieving complex multi-layer coating with relatively simple manufacturing steps
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 effectively reduces heat shrinkage and improves bonding strength with pole pieces, preventing short circuits and enhancing the safety and electrochemical performance of lithium ion batteries, while allowing for continuous and large-scale production.
Implementation Method 1
coat the separator with a ceramic layer to reduce the degree of heat shrinkage of the separator
Implementation Method 2
a polymer coating coated onto the ceramic surface or the membrane surface
Data Source
AI summary
Disclosed are a ceramic and polymer compositely coated lithium ion separator and a preparation method therefor. The ceramic and polymer compositely coated lithium ion separator comprises a polyolefin porous membrane, a ceramic coating coated onto one or both sides of a membrane surface, and a polymer coating coated onto a ceramic surface or the membrane surface. The composite separator prepared in the present disclosure significantly enhances heat resistance of the separator and bonding strength thereof with positive and negative pole pieces, improves the wettability of an electrolyte, can effectively prevent an internal short circuit due to layer dislocation between the separator and the electrodes, and also improves hardness and safety performance of the battery. Further disclosed is a method for preparing the ceramic and polymer compositely coated lithium ion separator, which method enables the preparation of a separator having even coating thickness of the ceramic coating and the polymer coating and good uniformity, and is favorable for continuous and large-scale production.