Separator Coating for Lithium Battery Thermal Stability
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Solution Overview
Problem
Lithium batteries face instability at high temperatures due to rapid thermal contraction, leading to potential short circuits and thermal runaway, as existing separators with polyethylene wax coatings melt and lose their structural integrity.
Innovation Solution
A separator with a network structure coating layer comprising organic particles, boehmite, and needle-shaped ceramic particles, along with high-melting-point binders, is developed to maintain stability and prevent electrode contact at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene wax is coated on the separator to improve shutdown function, then shutdown function is improved, but coating layer stability at high temperature deteriorates
Solution Approach 1:
The patent uses a composite coating layer comprising polyethylene wax particles (for shutdown function), boehmite particles (for thermal stability), and a binder resin (for structural integrity). This composite structure allows the separator to maintain both shutdown capability and high-temperature stability, as the binder resin prevents coating layer collapse even when polyethylene wax melts at elevated temperatures.
2Ease of manufacture
If the separator uses simple structure to reduce manufacturing complexity, then manufacturing ease is improved, but high-temperature stability deteriorates
Solution Approach 1:
The patent modifies the coating layer by controlling the glass transition temperature (Tg) of the binder resin to be 50°C or higher, and adjusting the weight ratios of components (polyethylene wax: boehmite: binder resin = 70:20:10 to 30:70:10). These parameter changes enable the coating layer to maintain structural integrity at high temperatures while preserving the relatively simple coating process.
3Reliability
If the separator coating layer is made thinner to improve ion conductivity, then ion conductivity is improved, but structural integrity at high temperature deteriorates
Solution Approach 1:
The patent employs a porous substrate with controlled porosity (30-80%) and uses a binder resin with Tg ≥ 50°C to create a coating layer that maintains porosity for ion conduction while providing thermal stability. The porous structure allows efficient ion transport even in thinner coatings, while the high-Tg binder prevents collapse at elevated temperatures.
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 separator effectively delays thermal runaway and maintains structural integrity, enhancing the stability and performance of lithium batteries at elevated temperatures by suppressing electrode contact and improving ion conductivity and air permeability.
Implementation Method 1
an organic particle having a melting point (Tm) in a range of 100°C to 130°C
Implementation Method 2
a first adhesive layer having a glass transition temperature (Tg) of 50°C or higher
Data Source
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AI summary
Provided are a separator and a lithium battery, the separator including: a porous substrate; and a first coating layer disposed on a surface of the porous substrate and including an organic particle having a melting point (Tm) in a range of 100 °C to 130 °C, a particle-type boehmite, a needle-shaped ceramic particle, and a first binder; a first adhesive layer disposed on another surface of the porous substrate, having a glass transition temperature (Tg) of 50 °C or higher, and containing a particle-type second binder; and a second adhesive layer disposed on the first coating layer, having a glass transition temperature (Tg) of 50 °C or higher, and including a particle-type second binder.