Lithium Battery Separator With Composite Coating For Thermal Runaway Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional separators for rechargeable lithium batteries lack sufficient insulation and shut-down functions, leading to overheating and potential short circuits between positive and negative electrodes.
Innovation Solution
A separator comprising a substrate with an organic layer and an inorganic layer, where the organic layer includes two or more kinds of organic particles with different sizes and a lower melting point than the substrate, and the inorganic layer includes inorganic particles, enhancing the shut-down function to suppress exothermicity and prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used, then the battery can operate, but the insulation function between positive and negative electrodes is insufficient leading to potential short circuits
Solution Approach 1:
The separator is constructed as a composite material consisting of a polyolefin base layer combined with a heat-resistant coating layer containing inorganic particles (such as alumina, silica, or boehmite) dispersed in a binder resin. This composite structure provides both the necessary insulation function and enhanced heat resistance to prevent short circuits under thermal stress.
Solution Approach 2:
The heat-resistant coating layer is applied locally on one or both surfaces of the polyolefin base layer, creating a functional gradient where the surface facing the electrodes has enhanced thermal stability and insulation properties, while the bulk material maintains its original shutdown function at lower temperatures.
2Reliability
If a conventional separator is used, then the battery can operate, but the shut-down function is insufficient due to previously generated heat and thermal runaway
Solution Approach 1:
The polyolefin base layer undergoes a phase transition (melting) at its specific melting point temperature, causing the separator pores to close and shut down ion transport. The heat-resistant coating layer with inorganic particles maintains structural integrity at higher temperatures, ensuring the shut-down function activates before thermal runaway occurs even when the battery has previously generated heat.
Solution Approach 2:
The heat-resistant coating layer acts as a protective barrier that prevents the base layer from degrading due to previously generated heat, cushioning the separator against thermal stress and ensuring the shut-down function remains effective when needed.
3Quantity of substance
If the organic layer includes two or more kinds of organic particles having different particle sizes, then the packing density is improved, but the manufacturing complexity increases
Solution Approach 1:
The invention specifies particular parameter ranges for the organic particles including size distribution (e.g., average particle size of 0.1-5 μm with a ratio of small to large particles between 1:1.5 and 1:7), weight ratios (e.g., 10:90 to 90:10), and melting points (100-130°C). By optimizing these parameters, the coating layer achieves high packing density and excellent insulation properties while maintaining feasibility for industrial manufacturing through controlled particle blending.
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 enhanced separator effectively suppresses exothermicity and prevents short circuits, thereby improving the safety of rechargeable lithium batteries by increasing internal resistance and controlling lithium ion movement.
Implementation Method 1
The organic material may have a lower melting point than that of the substrate. The organic material may have a melting point of about 100° C. to about 130° C.
Implementation Method 2
an inorganic layer positioned on at least one side of the substrate and including an inorganic material... capable of early suppressing exothermicity of a battery and preventing a short circuit between positive and negative electrodes
Implementation Method 3
The separator includes micropores through which lithium ions are passed, and plays a role of electrically insulating the positive and negative electrodes.
Data Source
AI summary
A separator for a rechargeable lithium battery includes a substrate, an organic layer positioned on at least one side of the substrate and including an organic material and an inorganic layer positioned on at least one side of the substrate and including an inorganic material, wherein the organic material includes two or more kinds of organic particles having different particle sizes from each other.