Nanofiber Electrode Coating for Separator Shutdown in Li Batteries
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Solution Overview
Problem
Conventional rechargeable lithium batteries face challenges with heat shrinkage of separators, leading to potential short circuits and safety issues, and existing solutions with high heat resistance materials lack effective shutdown characteristics.
Innovation Solution
An electrode assembly is developed with a coating layer integrated with the electrode active material layer, using polymer nanofibers composed of fluorine-based and nitrile-based polymers, which have high dielectric constant and electrical conductivity, to replace the conventional separator, ensuring no heat shrinkage and providing shutdown characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used in rechargeable lithium batteries, then the battery structure is simple and easy to manufacture, but the separator undergoes heat shrinkage at high temperatures leading to short circuits and safety issues
Solution Approach 1:
The patent combines the separator function and electrode active material layer into a single integrated coating layer formed by electrospinning polymer nanofibers directly on the current collector. This merging eliminates the need for a separate conventional separator while providing both structural integrity and shutdown characteristics, thereby improving safety without significantly increasing device complexity
Solution Approach 2:
The patent uses composite polymer nanofiber materials consisting of heat-resistant polymers (such as polyimide, polyether sulfone, or polyacrylonitrile) combined with shutdown-functional polymers. This composite material structure provides both high-temperature stability to prevent heat shrinkage and shutdown characteristics to block ion transport at elevated temperatures, resolving the contradiction between safety and structural simplicity
2Temperature
If high heat resistance materials are used for the separator to prevent heat shrinkage, then thermal stability is improved, but shutdown characteristics are lost
Solution Approach 1:
The patent employs composite polymer materials that combine heat-resistant polymers (providing thermal stability up to 200°C or higher) with shutdown-functional polymers (providing pore closure at specific temperatures). The electrospun nanofiber structure allows both material types to work synergistically, maintaining structural integrity at high temperatures while enabling shutdown characteristics through controlled pore blocking
Solution Approach 2:
The patent implements local quality differentiation within the coating layer by creating regions with different polymer compositions and thermal properties. The heat-resistant polymer provides structural framework maintaining dimensional stability, while embedded shutdown-functional polymer regions provide localized pore closure at specific temperatures, achieving both heat resistance and shutdown characteristics in different local areas of the same layer
3Reliability
If a separate separator is used, then shutdown characteristics can be provided, but heat shrinkage occurs leading to potential short circuits
Solution Approach 1:
The patent merges the separator and electrode active material layer into a single electrospun coating layer that is directly formed on the current collector. This integrated structure eliminates the interface between separate components, preventing relative movement and heat-induced separation that causes short circuits, while maintaining dimensional stability through the nanofiber network structure
Solution Approach 2:
The patent uses a thin film structure formed by electrospun polymer nanofibers that provides both mechanical flexibility and thermal stability. The nanofiber network creates a porous yet structurally sound layer that maintains dimensional integrity at high temperatures while allowing ion transport, preventing the heat shrinkage issues associated with conventional dense separator films
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 enhances safety by preventing heat shrinkage and thermal runaway, while maintaining high heat resistance and stability, thereby improving the capacity and cycle-life characteristics of rechargeable lithium batteries.
Implementation Method 1
the polymer nanofibers include a fluorine-based polymer and a nitrile-based polymer... exhibiting shutdown characteristics and no heat shrinkage
Implementation Method 2
electrospinning the polymer solution onto the electrode active material layer
Data Source
AI summary
Disclosed are an electrode assembly, a method of preparing the electrode assembly, and a rechargeable lithium battery including the electrode assembly. The electrode assembly includes an electrode current collector, an electrode active material layer on the electrode current collector, and a coating layer located on the electrode active material layer and integrated with the electrode active material layer. The coating layer includes polymer nanofibers. The polymer nanofibers include a fluorine-based polymer and a nitrile-based polymer as a polymer. A dielectric constant of the polymer is greater than or equal to about 0.06 pF/mm3, and the electrical conductivity of the polymer is in a range of about 3.0 μS/mm3 to about 50.0 μS/mm3.