Binder-Free Inorganic Separator Coating for Thermal Shrinkage
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Solution Overview
Problem
Existing composite separators in batteries face challenges with high thermal shrinkage and poor electrolyte wettability due to issues with binder distribution, leading to cracking, aging, and detachment of ceramic particles, which affect ion conduction and safety performance.
Innovation Solution
A separator with an ultra-thin, binder-free inorganic dielectric layer of specific thickness and mass ratio on a porous substrate, formed through vapor deposition, enhancing interfacial wettability and thermal shrinkage resistance while maintaining mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a composite separator is prepared by coating a ceramic coating layer on a polymer substrate using binder-based methods, then the thermal shrinkage and electrolyte wettability are improved, but the coating layer easily develops cracks, aging, porosity changes, or particle detachment during long-term cycling or battery abuse
Solution Approach 1:
The patent removes the binder component from the coating layer formulation, using only inorganic particles without any organic binder material. This extraction of the problematic binder eliminates the source of cracking and detachment while maintaining coating integrity through direct particle-to-substrate adhesion and particle-to-particle contact
Solution Approach 2:
The patent creates a composite structure consisting of inorganic particles directly deposited on the polymer substrate, forming an inorganic-coating layer without organic binder. This composite material approach uses the inherent properties of inorganic particles to provide both thermal stability and mechanical integrity
2Temperature
If the inorganic coating layer thickness is increased to improve thermal shrinkage resistance, then the thermal stability is improved, but the ion conduction performance deteriorates due to pore blocking
Solution Approach 1:
The patent optimizes the thickness parameter of the inorganic coating layer to a specific range (50-500 nm) that balances thermal shrinkage resistance and ion conduction performance. This parameter optimization ensures the coating is thick enough to prevent thermal shrinkage but thin enough to maintain pore openness for ion transport
Solution Approach 2:
The patent creates a coating layer with controlled local density and porosity characteristics, where the inorganic particles are distributed to provide thermal stability in certain regions while maintaining open pore structures in other regions for ion conduction, achieving spatially differentiated functionality
3Temperature
If the mass ratio of inorganic layer to substrate is increased to enhance thermal stability, then the thermal shrinkage resistance is improved, but the mechanical strength and energy density are compromised
Solution Approach 1:
The patent optimizes the mass ratio parameter of the inorganic coating layer to the range of 0.01-10, finding the optimal balance point where sufficient inorganic content provides thermal stability while excessive amounts that would compromise mechanical strength and energy density are avoided
Solution Approach 2:
The patent applies a moderate amount of inorganic coating (not excessive coverage) that is sufficient to provide thermal shrinkage resistance and safety performance while avoiding over-coating that would increase mass, reduce mechanical flexibility, and lower energy density
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 mechanical strength, thermal shrinkage resistance, and safety performance by preventing cracking and pore blocking, thereby extending battery cycle life and maintaining high energy density.
Implementation Method 1
forming an inorganic layer on a surface of the substrate and in the pores by means of vapor deposition
Data Source
AI summary
The present disclosure relates to a separator, a method for preparing the separator, and an electrochemical device containing the separator. The separator includes a substrate and an inorganic layer disposed on at least one side of the substrate. The substrate is a porous substrate. The inorganic layer is a dielectric layer containing no binder. The inorganic layer has a thickness of 20 nm to 2000 nm. A mass of the inorganic layer is M1, a mass of the substrate is M2, and M1/M2 is greater than or equal to 0.05 but smaller than or equal to 7.5. An interfacial peeling force between the inorganic layer and the substrate is not smaller than 30 N/m. The interfacial wettability and thermal shrinkage resistance performance of the separator are effectively improved while the separator has a certain mechanical strength. The separator can have favorable mechanical strength and thermal shrinkage percentage and high energy density.