Single-Layer Composite Separator for Li-Ion Battery Thermal Runaway Prevention
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Solution Overview
Problem
Conventional lithium-ion battery separators are prone to thermal runaway and short circuiting due to their multi-layered structure, which can lead to overheating and catastrophic failures, and they lack effective mechanisms to interrupt electro-chemical processes during overheating events.
Innovation Solution
A single-layer composite separator made of entangled glass microfibers and a polymer component with a melting point below 150°C, which is uniformly distributed throughout the mat, providing puncture resistance and the ability to melt and disrupt electro-chemical reactions upon overheating, thereby preventing thermal runaway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional multi-layered separators are used, then structural strength is provided, but thermal runaway prevention is insufficient
Solution Approach 1:
The patent combines the mechanical strength function (previously provided by glass fiber layers) and the thermal shutdown function (previously provided by polymer layers) into a single integrated layer. The glass fiber mat and polymer component are uniformly mixed and bonded together to form one homogeneous layer that simultaneously provides both structural support and thermal runaway prevention, eliminating the need for multiple separate layers.
Solution Approach 2:
The invention creates a composite material by uniformly distributing polymer components (such as polyethylene or polypropylene with melting points below 150°C) throughout a glass fiber mat matrix. This composite structure allows the separator to exhibit both the mechanical properties of glass fibers and the thermal response properties of polymers within a single layer, resolving the contradiction between structural strength and thermal safety.
2Productivity
If separator thickness is reduced to improve battery efficiency, then energy density increases, but mechanical strength decreases
Solution Approach 1:
The patent optimizes the physical and chemical parameters of the composite material, specifically the ratio of glass fiber to polymer component, the melting point of the polymer (selected to be below 150°C), and the bonding characteristics. By carefully controlling these parameters, the separator achieves optimal balance between thinness (0.03-0.1 inches) for battery efficiency and sufficient mechanical strength for safety, allowing reduced thickness without sacrificing puncture resistance.
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 single-layer composite separator effectively prevents thermal runaway and maintains mechanical strength and thinness, enhancing lithium-ion battery safety and efficiency by ensuring the polymer component melts and interrupts ion transport when exposed to high temperatures, thus preventing overheating.
Implementation Method 1
The polymer component has a melting point of less than about 150 degrees Celsius so that when exposed to a sufficiently high temperature, the polymer component melts within the nonwoven fiber mat and disrupts the electro-chemical reaction of the lithium-ion battery
Data Source
AI summary
A battery separator for a lithium-ion battery includes a nonwoven fiber mat that is composed of entangled microfibers having an average fiber diameter of less than 6 microns. The nonwoven fiber mat also includes a binder that binds the microfibers together and a polymer component that is dispersed homogeneously through or within the entangled microfibers so that the polymer component is uniformly distributed throughout the nonwoven fiber mat and so that the entangled microfibers, the binder, and the polymer component form a single layer component or product. The polymer component is configured to melt within the nonwoven fiber mat when exposed to a sufficiently high heat in order to effectively interrupt an electro-chemical process of the lithium-ion battery and thereby prevent overheating of the lithium-ion battery. The nonwoven fiber mat is typically between 0.1 and 20 mils thick.