Coated Polyolefin Separator for Fast Low-Temperature Pore Closure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithium battery separators have a high pore-closing temperature and slow response time, leading to thermal runaway and safety issues due to poor compatibility between materials and inefficient pore closure mechanisms.
Innovation Solution
A separator substrate made from a combination of linear unbranched polyethylene and long-branched polyethylene, coated with a heat-sensitive high molecular material, ceramic particles, and a binder, to achieve a lower pore-closing temperature and faster response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If low-melting point materials are introduced into polyolefin material to reduce pore-closing temperature, then the pore-closing temperature decreases, but the pore-closing response time becomes slow and heat accumulates causing thermal runaway
Solution Approach 1:
The patent uses a composite structure consisting of a polyolefin base membrane combined with a heat-sensitive polymer coating layer. This composite design allows the base membrane to provide structural stability while the coating layer enables rapid pore closure at lower temperatures, resolving the contradiction between low pore-closing temperature and thermal safety reliability.
Solution Approach 2:
The patent modifies the pore-closing characteristics by changing the chemical composition and thermal properties of the coating layer. By selecting heat-sensitive polymers with specific glass transition temperatures and adjusting their molecular weight and crosslinking degree, the patent achieves rapid pore closure response at controlled low temperatures without causing thermal runaway.
2Temperature
If a low-melting point polymer is coated on the surface to lower pore-closing temperature, then the pore-closing temperature decreases, but the polymer vaporizes at higher temperatures causing bubble breakage and pore reopening
Solution Approach 1:
The patent applies local quality by creating a coating layer with specific heat-sensitive properties only on the surface of the base membrane. This localized modification allows the coating to close pores rapidly at low temperatures while the underlying polyolefin base membrane maintains structural integrity and prevents pore reopening at higher temperatures, thus ensuring stable pore closure.
Solution Approach 2:
The heat-sensitive polymer coating acts as an intermediary layer between the external environment and the base membrane. It mediates the pore closure process by responding to temperature changes and closing pores at low temperatures, while the polyolefin base membrane serves as a stable substrate that prevents pore reopening, thus ensuring stable pore closure without vaporization-induced bubble breakage.
3Temperature
If a composite PP/PE/PP separator is prepared by co-extrusion to achieve low pore-closing temperature, then the pore-closing temperature equals the melting point of PE, but the compatibility between PP and PE is poor
Solution Approach 1:
The patent segments the separator structure into two distinct functional layers: a polyolefin base membrane providing mechanical strength and chemical stability, and a heat-sensitive polymer coating layer providing rapid pore closure capability. This segmentation avoids the material compatibility issues of co-extruded multi-layer structures while achieving both low pore-closing temperature and high material compatibility.
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 proposed separator effectively reduces the pore-closing temperature and response time, enhancing the automatic power-off function of batteries and improving safety performance by preventing thermal runaway.
Implementation Method 1
a layer of a heat-sensitive material is coated on the surface of the separator substrate to achieve the effects of lowering the pore-closing temperature and pore-closing response time
Implementation Method 2
When the internal temperature of a battery increases quickly, a separator is rapidly melted to close pores to block lithium ions from passing through
Data Source
Figure 1~2
AI summary
The present invention provides a separator having a low pore-closing temperature, including a base membrane containing an unbranched polyolefin and a long-branched polyolefin, and a coating formed on at least one surface of the base membrane and containing a heat-sensitive high molecular material. By the aforesaid solution, the present invention can substantially lower the pore-closing response time and pore-closing temperature of the separator, thus improving the safety performance of lithium ion batteries. In addition, the present invention further provides a method for preparing the aforesaid separator having a low pore-closing temperature and a battery containing the aforesaid separator having a low pore-closing temperature.