Lithium Battery Separator Emulsion Binder Layer Adhesion
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Solution Overview
Problem
Lithium secondary batteries face safety risks due to thermal contraction of polyolefin-based separators, which can lead to short circuits and explosions, and existing composite separators have issues with inorganic particle content affecting binder polymer stability during assembly.
Innovation Solution
A separator for lithium secondary batteries featuring a porous polymer substrate with an emulsion binder layer between the substrate and a porous coating layer, using specific polymer binders and inorganic particles to enhance adhesion and thermal stability, and a manufacturing method involving emulsion binder solution formation and coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the content of inorganic particles in the porous active layer is increased to suppress thermal contraction, then thermal stability is improved, but the binder polymer content becomes relatively lower causing inorganic particles to get unstuck during assembly
Solution Approach 1:
The patent changes the chemical composition parameters of the binder polymer to achieve optimal binding. Specifically, it uses a binder polymer with a glass transition temperature of -50°C to 0°C and specific functional groups that provide both thermal resistance and adhesion strength, allowing the system to maintain binding reliability while using high inorganic particle content for thermal stability
Solution Approach 2:
The patent creates a composite porous active layer combining inorganic particles (such as alumina, silica, or boehmite) with a specifically designed binder polymer system. This composite structure allows the inorganic particles to provide thermal stability while the engineered binder matrix maintains particle adhesion during assembly processes
2Reliability
If the content of binder polymer is increased to prevent inorganic particles from getting unstuck, then binding reliability is improved, but the content of inorganic particles becomes relatively lower reducing thermal contraction suppression
Solution Approach 1:
Rather than increasing binder content, the patent changes the quality parameters of the binder polymer including its glass transition temperature (-50°C to 0°C), molecular weight, and functional group composition. This enables effective binding with lower binder content while maintaining thermal stability through the inorganic particle network
3Ease of manufacture
If polyolefin-based porous substrates are used for separators, then manufacturing ease is improved, but thermal shrinking behavior becomes extremely severe at 100°C or above causing short circuits
Solution Approach 1:
The patent applies composite materials by coating a porous active layer containing inorganic particles and binder polymer on the polyolefin substrate. The inorganic particles serve as spacers that mechanically maintain the shape and suppress thermal contraction of the substrate at elevated temperatures, while the substrate itself retains its manufacturing advantages
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 binding between the separator and coating layers, reduces the risk of peeling, enhances processability, and increases electrolyte wettability, thereby improving cell safety and performance.
Implementation Method 1
improves binding between the separator and coating layers
Implementation Method 2
increases electrolyte wettability
Data Source
AI summary
Provided are a separator for a lithium secondary battery and a manufacturing method therefor. In order to improve processability and cell stability by increasing the bonding force between a separator and a coating layer, the separator comprises: a porous polymer substrate having a plurality of pores; a porous coating layer formed on at least one surface of the porous polymer substrate; and an emulsion binder layer formed between the porous polymer substrate and the porous coating layer.