Nanofibrous Battery Separator With Melt-Shutdown Pore Blocking
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Solution Overview
Problem
Existing separator-free lithium-ion batteries face safety hazards due to the inability of non-woven fabric separation layers to occlude pores during thermal runaway and low mechanical strength, leading to potential internal short circuits and self-discharge issues.
Innovation Solution
A separation layer comprising a nanofibrous porous substrate with low-melting-point polymer particles distributed within, which occludes pores and enhances mechanical strength to prevent short circuits and self-discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a non-woven fabric separation layer is used to simplify the production process and reduce manufacturing difficulty, then the production process is simplified and manufacturing difficulty is reduced, but the separation layer cannot occlude pores under heat and cannot cut off electrical current during thermal runaway, causing safety hazards
Solution Approach 1:
The patent uses a composite structure consisting of a fibrous substrate combined with a heat-responsive polymer coating layer. The fibrous substrate provides mechanical strength and porosity for ion transport, while the polymer coating layer (with melting point 60-100°C) provides thermal shutdown capability. This composite approach allows the separation layer to maintain both ease of manufacture and high safety performance by combining materials with complementary properties.
Solution Approach 2:
The patent applies a heat-responsive polymer coating that undergoes a phase change at a specific temperature range (60-100°C). When the battery experiences thermal runaway and the temperature reaches this range, the polymer melts and closes the pores, automatically cutting off the electrical current. This parameter-based response (temperature-triggered phase change) provides intelligent safety protection while maintaining the simple non-woven fabric structure for easy manufacturing.
2Ease of manufacture
If a non-woven fabric separation layer with low mechanical strength is used, then the production process is simplified, but the separation layer cannot resist penetration by positive or negative electrode particles, causing internal short circuits
Solution Approach 1:
The patent creates a composite separation layer where a fibrous substrate (providing mechanical strength and structural integrity) is combined with a heat-responsive polymer coating (providing thermal shutdown function). The fibrous substrate can be made from common materials like polyolefin non-woven fabric that offer adequate mechanical strength to prevent particle penetration, while the polymer coating adds the safety function without significantly complicating the manufacturing process.
Solution Approach 2:
The heat-responsive polymer coating is applied as a thin layer on the surface of the fibrous substrate, providing the thermal shutdown function locally where it is most needed (at the separation interface), while the bulk fibrous substrate maintains its mechanical strength properties. This localized application of functional material preserves the overall simplicity of the non-woven fabric structure while adding the required safety capability.
3Ease of manufacture
If a non-woven fabric separation layer with large and unevenly distributed pore diameters is used, then the production process is simplified, but severe self-discharge problems occur in the lithium-ion battery
Solution Approach 1:
The heat-responsive polymer coating undergoes a phase change at 60-100°C, transitioning from a solid state that allows ion transport to a melted state that closes the pores. This parameter-based response provides dynamic control of pore size: under normal operating conditions, the pores remain open for ion transport, but during thermal runaway when temperature rises, the pores automatically close to prevent self-discharge and electrical short circuits.
Solution Approach 2:
The patent converts the potential harm of thermal runaway (excessive heat generation) into a beneficial safety mechanism. The heat itself triggers the polymer coating to melt and close the pores, transforming the harmful thermal condition into an automatic shutdown signal that prevents further energy loss through self-discharge and electrical short circuits.
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 solution improves safety by blocking ion conduction paths during thermal runaway and reduces self-discharge, while increasing mechanical strength to prevent penetration by active material particles.
Implementation Method 1
A melting temperature of the polymer particles is 70° C. to 150° C.
Implementation Method 2
a nanofibrous porous substrate comprising nanofibers and polymer particles distributed in the porous substrate
Data Source
AI summary
An electrochemical device includes an electrode plate and a separation layer on at least one surface of the electrode plate. The separation layer includes a nanofibrous porous substrate including nanofibers and polymer particles distributed in the nanofibrous porous substrate including nanofibers. A melting temperature of the polymer particles is 70° C. to 150° C.