Polymer Separator Membrane Cross-Linking via Energy Beam Irradiation
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Solution Overview
Problem
Existing methods for cross-linking separator membranes in electrochemical cells, such as lithium-ion batteries, are limited to the extrusion process and cannot be applied to already formed membranes, posing challenges in achieving thermal stability and safety standards.
Innovation Solution
A method involving irradiation of a polymer separator membrane with an energy beam at specific doses and temperatures to create cross-linking chemical bonds, reducing shrinkage and enhancing thermal stability, without the need for cross-linking agents or initiators, and incorporating ceramic particles in polymeric binders for added thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If chemical treatments are used to facilitate cross-linking reaction during separator extrusion, then cross-linking is achieved, but the method cannot be applied to already formed separator membranes
Solution Approach 1:
The patent replaces chemical treatment methods with physical irradiation treatment. Instead of using chemical cross-linking agents during extrusion, the invention uses electron beam or gamma ray irradiation to induce cross-linking in already-formed separator membranes, thereby extending the cross-linking capability to post-production stages while achieving comparable or superior thermal stability.
Solution Approach 2:
The patent performs cross-linking treatment after the separator membrane has been fully formed and assembled into the battery structure. This preliminary action (in the sense of being done in advance of final battery assembly or as a standalone post-processing step) allows the separator to gain enhanced thermal properties without requiring modification of the extrusion process itself.
2Stability of the object's composition
If cross-linking is performed on already formed separator membranes, then thermal stability is enhanced, but additional processing steps are required
Solution Approach 1:
The patent extracts the cross-linking function from the extrusion process and makes it a separate, independent treatment step. This allows the cross-linking to be applied to already-formed membranes without requiring integration into the complex extrusion machinery, thereby adding only a single processing step rather than complicating the existing extrusion line.
3Stability of the object's composition
If cross-linking agents and initiators are used, then cross-linking reaction is facilitated, but residual chemicals remain in the separator membrane
Solution Approach 1:
The patent completely eliminates chemical cross-linking agents and initiators by using physical irradiation (electron beam or gamma rays) to induce cross-linking. This substitution of chemical methods with physical radiation methods achieves effective cross-linking without introducing any residual chemicals that could harm battery performance or safety.
Solution Approach 2:
The separator membrane itself undergoes self-cross-linking when exposed to irradiation. The radiation energy directly induces cross-linking reactions within the polymer structure of the separator without requiring any external chemical agents, making the process clean and free from chemical contaminants.
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 method achieves a cross-linked polymer separator membrane with a gel content of 30-90% and a shrinkage rate less than 30% at 140°C, providing enhanced thermal stability and safety for lithium-ion batteries.
Implementation Method 1
irradiating the polymer separator membrane with an energy beam under a radiation dose ranging between 50 and 200 kGy to effect a cross-linking in the polymer separator membrane
Implementation Method 2
a shrinkage rate less than 30% at 140°C
Data Source
AI summary
The invention discloses a method of manufacturing an electrochemical cell having a polymer separator membrane for separation of electrodes in the electrochemical cell, including providing a cathode and providing a polymer separator membrane. At least one cycle of irradiating the polymer separator membrane is performed by an energy beam under a radiation dose ranging between 50 and 200 kGy to effect a cross-linking in the polymer separator membrane. The polymer separator membrane is maintained at a temperature between 30° C. and 70° C. An anode is then provided. Subsequently, the polymer separator membrane is compressed between the cathode and the anode. An electrolyte is provided to form the electrochemical cell.