Lithium Battery Separator with Organic-Inorganic Layers
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in preventing battery expansion during repeated cycles and ensuring safety against overheating, which can limit the effectiveness of the separator's shut-down function and insulation between the positive and negative electrodes.
Innovation Solution
The battery design incorporates a stacked electrode assembly with a first separator and a second separator, where at least one side of each separator includes an organic layer and an inorganic layer, optimized for adherence and electrolyte supply to prevent expansion and enhance safety through controlled longitudinal compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If repeated charge and discharge cycles are performed, then battery capacity is improved, but battery expansion occurs
Solution Approach 1:
The separator thickness is optimized within a specific range (6-25 μm) to balance mechanical strength and flexibility. This parameter optimization allows the separator to accommodate volume changes of electrodes during cycling without causing battery expansion, while maintaining sufficient strength to prevent short circuits.
Solution Approach 2:
The separator employs a porous structure with controlled pore size (0.01-1 μm) that allows efficient lithium ion transport during charge-discharge cycles while providing a buffer for electrode expansion. The porous network can absorb mechanical stress from electrode swelling, preventing battery expansion over repeated cycles.
2Reliability
If separator thickness is increased to improve insulation, then safety is improved, but battery thickness increases
Solution Approach 1:
The separator thickness is precisely controlled within the range of 6-25 μm to achieve optimal balance between insulation performance and battery compactness. This parameter optimization ensures sufficient electrical insulation while minimizing the contribution of the separator to overall battery thickness.
Solution Approach 2:
The coating layer with inorganic heat-resistant particles provides enhanced insulation and thermal stability without requiring significant increases in separator thickness. The composite structure delivers high performance in a thin format, maintaining battery compactness while improving safety.
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
This configuration effectively prevents battery expansion during charge and discharge cycles, improves safety by reducing battery strength, and ensures efficient electrolyte supply, thereby enhancing the battery's performance and safety against overheating.
Implementation Method 1
improves safety by controlling battery strength to be favorable for longitudinal compression
Implementation Method 2
The separator electrically insulates the space between the positive electrode and the negative electrode and includes micropores through which lithium ions move
Implementation Method 3
a shut-down function of the separator prevents overheating of a battery when the battery temperature is above a predetermined temperature
Data Source
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AI summary
A rechargeable lithium battery includes an electrode assembly including a positive electrode, a first separator, a negative electrode, and a second separator that are sequentially stacked. The first separator includes a first substrate including a first side facing the positive electrode and a second side facing the negative electrode. The second separator includes a second substrate including a third side facing the negative electrode and a fourth side facing the positive electrode. At least one of the first side to the fourth side includes an organic layer including an organic material, and at least one of the second side or the third side includes an inorganic layer including an inorganic material.