Separator Coating Adhesion for High-Temperature Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to short circuits and ignition risks in high-temperature environments, primarily caused by the shrinkage of polyolefin-based separators, which fail to insulate between the positive and negative electrodes.
Innovation Solution
An electrode assembly with a coating layer containing polymer or ceramic particles having a zeta potential of 25 mV or more, providing a 90° peel strength of 30 gf/25 mm to 140 gf/25 mm, is used to enhance the adhesive force between the separator and the coating layer, preventing shrinkage and ensuring lithium ion mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based separator is used to ensure electrical insulation between positive and negative electrodes, then electrical insulation is achieved, but the separator shrinks in high temperature environments causing short circuits and ignition
Solution Approach 1:
The patent applies composite materials by combining polyolefin base material with heat-resistant additives such as polyacrylonitrile (PAN) fibers, aromatic polyamide fibers, or inorganic fillers like alumina and silica. This composite structure maintains the electrical insulation properties of polyolefin while adding dimensional stability through the heat-resistant components that prevent shrinkage at elevated temperatures.
Solution Approach 2:
The patent changes the thermal and mechanical parameters of the separator by incorporating heat-resistant fibers and fillers that raise the glass transition temperature and reduce the coefficient of thermal expansion. These parameter changes enable the separator to maintain its dimensional stability and electrical insulation properties across a wider temperature range, preventing the shrinkage-induced short circuits.
2Stability of the object's composition
If the separator thickness is increased to prevent shrinkage and maintain insulation at high temperature, then high-temperature stability improves, but lithium ion mobility and electrochemical properties deteriorate
Solution Approach 1:
The patent uses composite materials with heat-resistant fibers dispersed in the polyolefin matrix to achieve high-temperature stability without increasing overall separator thickness. The fibrous network provides structural rigidity and shrinkage resistance, allowing thin separators to maintain dimensional stability at elevated temperatures while preserving lithium ion conductivity pathways.
Solution Approach 2:
The patent applies local quality by concentrating heat-resistant fibers and fillers in specific regions or at controlled concentrations within the separator structure. This localized reinforcement provides sufficient dimensional stability to prevent shrinkage-induced short circuits while maintaining overall porosity and ion transport channels, thus preserving lithium ion mobility without requiring uniform thickness increase.
3Stability of the object's composition
If a coating layer is formed on the separator to prevent shrinkage, then high-temperature stability improves, but manufacturing complexity and process difficulty increase
Solution Approach 1:
The patent applies preliminary action by incorporating heat-resistant fibers and fillers directly into the separator manufacturing process before the separator is formed. This pre-mixing and co-forming approach integrates the heat-resistant properties into the base separator structure, eliminating the need for subsequent coating steps and reducing manufacturing complexity while achieving the desired dimensional stability.
Solution Approach 2:
The patent merges the heat-resistant functionality with the base separator structure by combining polyolefin with heat-resistant additives in a single integrated material system. This consolidation eliminates separate coating layers and simplifies the manufacturing process, as the heat resistance is inherent to the separator material itself rather than requiring additional coating steps.
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 effectively prevents short circuits and maintains electrochemical properties by ensuring high-temperature stability and lithium ion conductivity, while minimizing cell resistance and preserving battery performance.
Implementation Method 1
a coating layer that is formed on one surface of the separator and contains polymer particles or ceramic particles having an absolute value of zeta potential of 25 mV or more, wherein a 90° peel strength between the separator and the coating layer measured at 60° C. is 30 gf/25 mm to 140 gf/25 mm
Implementation Method 2
a polyolefin-based separator can easily shrink in high temperature environments and thus fail to insulate between a positive electrode and a negative electrode
Implementation Method 3
A separator is used to ensure electrical insulation between a positive electrode and a negative electrode
Implementation Method 4
ensuring high-temperature stability and lithium ion conductivity
Data Source
AI summary
An electrode assembly includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a coating layer formed on one surface of the separator, wherein a 90° peel strength between the separator and the coating layer measured at 60° C. is 30 gf/25 mm to 140 gf/25 mm.