Cross-Linked Ceramic Battery Separator Coating for Thin Thermal Stability
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Solution Overview
Problem
Existing ceramic-coated separators in lithium ion batteries lack sufficient thermal stability and mechanical properties to meet the demands of high energy density batteries.
Innovation Solution
A cross-linked ceramic coating is applied to a porous membrane, which can be thin (≤5 microns) and includes a cross-linker or cross-linking agent, thickening agent, adhesion-promotion agent, surfactant, and dispersant, forming a coating with improved thermal stability and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional ceramic coating is applied to a porous membrane, then the separator provides basic thermal stability, but the thermal stability is insufficient for high energy density batteries and the coating requires greater thickness to achieve adequate protection
Solution Approach 1:
The patent applies cross-linking chemistry to transform the ceramic coating from a conventional structure to a cross-linked network structure. This parameter change in molecular architecture enables the coating to achieve superior thermal stability at reduced thickness, directly resolving the contradiction between thermal stability and coating thickness
Solution Approach 2:
The patent creates a composite ceramic coating system combining ceramic particles with cross-linking agents and binders. This composite structure leverages the thermal stability of ceramics while the cross-linked polymer network provides structural integrity at thin thicknesses, simultaneously achieving high reliability and thin dimensions
2Weight of moving object
If the ceramic coating thickness is reduced to improve energy density, then the separator becomes thinner and lighter, but the mechanical properties and thermal stability deteriorate
Solution Approach 1:
Cross-linking transforms the mechanical properties of the ceramic coating by creating a three-dimensional network structure. This parameter change in molecular structure provides enhanced mechanical strength and rigidity that compensates for the reduced coating thickness, maintaining separator integrity while reducing overall weight
Solution Approach 2:
The patent replaces reliance on coating thickness for mechanical strength with a cross-linked molecular network. Instead of using thicker coatings to achieve mechanical properties, the cross-linking chemistry creates a structurally robust network that provides equivalent or superior mechanical performance at reduced thickness
3Reliability
If a thicker ceramic coating is applied to improve thermal stability, then the separator maintains better mechanical properties, but the moisture content increases and affinity for electrolyte decreases
Solution Approach 1:
Cross-linking changes the physical and chemical parameters of the ceramic coating, creating a more compact and stable structure. This parameter change reduces the coating's moisture absorption capacity while enhancing thermal stability, allowing thin coatings to outperform thicker conventional coatings in both thermal stability and moisture content
4Ease of manufacture
If a conventional ceramic coating is used, then the manufacturing process is simple, but the separator exhibits higher heat shrinkage and insufficient thermal stability
Solution Approach 1:
The patent introduces cross-linking as an additional process parameter that transforms the coating's thermal properties. While this adds a cross-linking step to manufacturing, the resulting heat shrinkage resistance and thermal stability are dramatically improved, with cross-linked coatings showing less than 5% heat shrinkage at 150°C compared to much higher values for conventional coatings
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 cross-linked ceramic coating exhibits reduced heat shrinkage, lower moisture content, and enhanced electrolyte affinity, maintaining mechanical integrity and thermal stability, even at high temperatures.
Implementation Method 1
a cross-linked ceramic coating provided on at least one side of the porous membrane... the cross-linked ceramic coating may comprise ceramic particles and at least one cross-linker or cross-linking agent
Implementation Method 2
applying a slurry to at least one side of a porous membrane to form a slurry layer
Implementation Method 3
cross-linking the slurry layer... Cross-linking may comprise applying light (including UV light), heat, or light (including UV light) and heat to the slurry layer
Data Source
AI summary
A porous membrane having a cross-linked ceramic coating on at least one side thereof is disclosed. The coated porous membrane may be used as a battery separator, particularly a battery separator for a lithium ion battery. The coating includes at least a cross-linker and a ceramic. The cross-linker may be a particulate polymeric binder cross-linker, a PEO (PEG) cross-linker, or a POSS cross-linker. The coated membrane exhibits improved properties that may be favorable for its use as a battery separator. For example, the coated porous membrane may exhibit improved shrinkage properties and high temperature resistance.