Multi-Layer Separator with Variable Melting Point Particles
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Solution Overview
Problem
Conventional separators for rechargeable lithium batteries fail to adequately insulate positive and negative electrodes and prevent thermal runaway, leading to overheating and potential short circuits.
Innovation Solution
A separator comprising a substrate with an organic layer and an inorganic layer, where the organic layer includes two or more organic particles with different melting points and the inorganic layer includes inorganic materials, enhancing the shut-down function to suppress exothermicity and prevent short circuits by controlling lithium ion movement and thermal contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used, then the battery can operate, but it fails to adequately insulate electrodes and prevent thermal runaway
Solution Approach 1:
The separator is constructed as a composite material combining an organic layer (containing polyolefin particles with different melting points) and an inorganic layer (containing alumina particles). This composite structure enables multi-stage shut-down functionality: the organic layer provides initial thermal protection at lower temperatures through particle melting and pore closure, while the inorganic layer maintains structural integrity at higher temperatures, collectively preventing electrode short circuits and thermal runaway.
2Reliability
If the separator uses multiple organic particles with different melting points, then exothermicity is suppressed earlier, but the structure becomes more complex
Solution Approach 1:
The organic layer contains polyolefin particles with deliberately selected different melting points (e.g., 105-115°C and 125-135°C) to create staged thermal responses. This parameter variation enables the separator to activate protection mechanisms at different temperature thresholds, suppressing exothermicity earlier and providing progressive thermal management without requiring complex additional components.
3Temperature
If the inorganic layer is added to the separator, then thermal stability is improved, but the manufacturing process becomes more difficult
Solution Approach 1:
The inorganic layer is constructed using porous alumina particles that maintain high porosity (30-70%) to ensure lithium ion permeability while providing thermal stability. The porous structure allows the layer to be formed through conventional coating and drying processes without requiring complex sintering or high-temperature treatments, thus maintaining ease of manufacture while achieving the desired thermal properties.
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 multi-stage shut-down function effectively reduces exothermicity and prevents short circuits, improving the safety of rechargeable lithium batteries by increasing internal resistance and blocking electrochemical reactions at lower temperatures.
Implementation Method 1
the organic material includes two or more organic particles having respective melting points that are different from each other
Implementation Method 2
the separator shuts down the battery when the battery temperature goes above or over a predetermined or set temperature
Data Source
AI summary
A separator for a rechargeable lithium battery includes a substrate; an organic layer on at least one side of the substrate and including an organic material; and an inorganic layer on at least one side of the substrate and including an inorganic material, where the organic material includes two or more organic particles having respective melting points that are different from each other. A rechargeable lithium battery includes the separator.