Porous Separator Coating to Prevent Thermal Shrinkage and Dendrites
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Solution Overview
Problem
Existing lithium ion batteries face safety issues due to thermal shrinkage of polyolefin-based separators, leading to short circuits and dendrite formation, which compromises battery stability and safety, particularly at high temperatures.
Innovation Solution
A porous separator comprising a layer of plate-type inorganic particles with a first binder polymer and a coating layer of spherical inorganic particles with a second binder polymer, which enhances tortuosity and uniform lithium ion distribution, reducing the likelihood of dendrite growth and short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based porous substrate is used as a separator, then it provides good porosity and ion conductivity, but it shows extreme thermal shrinkage behavior at temperatures of 100°C or higher causing short circuits
Solution Approach 1:
The patent applies composite materials by combining polyolefin-based porous substrate with inorganic particles (such as alumina, silica, or boehmite) and binder polymers to create a separator that maintains the porosity and ion conductivity of the polyolefin substrate while adding thermal stability through the inorganic component. The inorganic particles do not undergo thermal shrinkage, thus compensating for the polyolefin's thermal instability at high temperatures.
Solution Approach 2:
The patent changes the physical and chemical parameters of the separator by incorporating inorganic particles with specific size ranges (0.1-10 μm) and controlling the binder polymer content (1-30 parts by weight per 100 parts inorganic particles). These parameter adjustments ensure the composite separator maintains structural integrity at elevated temperatures without compromising ion conductivity.
2Reliability
If a porous organic-inorganic coating layer is formed by coating a mixture of inorganic particles and binder polymer, then thermal stability is improved, but coating defects and cracks occur during the drying process
Solution Approach 1:
The patent optimizes the slurry composition parameters, specifically controlling the binder polymer content to 1-30 parts by weight per 100 parts inorganic particles, and adjusting the solvent type and concentration. These parameter changes ensure proper slurry viscosity and drying characteristics, preventing crack formation while maintaining coating uniformity.
Solution Approach 2:
The patent utilizes the porous structure of the coating layer formed during the drying process, where the solvent evaporation creates a controlled porous network. This porous structure accommodates volume changes during drying, reducing internal stress and preventing crack formation while maintaining the desired coating uniformity and thermal stability.
3Reliability
If slurry is used to form a porous coating layer, then inorganic particles are packed in high density during drying, but this causes a problem of declining air permeability properties
Solution Approach 1:
The patent deliberately creates a porous coating layer structure during the drying process by controlling slurry composition and drying conditions. The porous structure provides both adequate particle packing density for thermal stability and sufficient pore spaces for air permeability and ion conductivity, resolving the contradiction between dense packing and permeability.
Solution Approach 2:
The patent applies local quality by creating different structural characteristics in different regions of the coating layer. The inorganic particles are densely packed in certain areas to provide thermal stability, while interconnected pore spaces are maintained in other regions to ensure air permeability and ion transport pathways.
4Power
If lithium ion batteries use organic electrolyte liquid, then high operating voltage and energy density are achieved, but safety problems such as ignition and explosion occur
Solution Approach 1:
The patent uses the porous separator with inorganic coating as an intermediary barrier between the cathode and anode. This separator mediates ion transport while physically blocking dendrite growth and providing thermal stability, preventing the harmful effects of organic electrolyte such as ignition and explosion without compromising the high energy density benefits.
Solution Approach 2:
The patent applies preliminary anti-action by incorporating thermally stable inorganic particles and heat-resistant binder polymers into the separator before battery operation. This preliminary structural reinforcement prevents thermal runaway and dendrite-induced short circuits that could lead to ignition or explosion, addressing safety concerns before they can manifest.
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 proposed separator design effectively blocks dendrite growth, improves safety by preventing thermal shrinkage, and ensures stable lithium ion transfer, thereby enhancing battery performance and safety, especially at high temperatures.
Implementation Method 1
a porous separator comprising: a porous layer including a number of plate-type inorganic particles, and a first binder polymer located on a part or all of surfaces of the plate-type inorganic particles to connect and fix the plate-type inorganic particles
Implementation Method 2
the organic/inorganic composite porous layer may be readily desorbed from the polyolefin-based porous substrate when assembling a secondary battery or using a battery, and this leads to decline in the battery safety
Implementation Method 3
ensures stable lithium ion transfer, thereby enhancing battery performance and safety
Data Source
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AI summary
According to the present invention, there is provided a porous separator provided with a porous layer including a number of plate-type inorganic particles, and a first binder polymer located on a part or all of surfaces of the plate-type inorganic particles to connect and fix the plate-type inorganic particles, and an electrochemical device including the same.