Composite Electrode Coating Layer for Separator-Free Li Battery Durability
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Solution Overview
Problem
Existing coating layers in electrode assemblies for rechargeable lithium batteries that function as separators have reduced durability compared to separate separators, compromising the safety and cycle-life of the batteries.
Innovation Solution
An electrode assembly is developed with a coating layer integrated with the electrode active material layer, composed of polymer nanofibers derived from fluorine-based and nitrile-based polymers, and inorganic particles, which enhances durability by improving puncture strength and tensile strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a coating layer is integrated with the electrode active material layer to function as a separator, then the energy density is improved by removing the need for a separate separator, but the durability is reduced compared to separate separators
Solution Approach 1:
The coating layer is constructed as a composite material comprising polymer nanofibers (including polyvinylidene fluoride and polyacrylonitrile) combined with inorganic particles (such as alumina, silica, or boehmite). This composite structure provides both the functional separation capability and enhanced mechanical durability, resolving the contradiction between energy density improvement and durability maintenance.
2Device complexity
If a coating layer is integrated with the electrode active material layer to function as a separator, then the device complexity is reduced by eliminating the separate separator, but the puncture strength is compromised
Solution Approach 1:
The coating layer is applied locally and directly onto the electrode active material layer surface, creating a localized protective and separating structure. This local integration reduces overall device complexity while the specialized composition (polymer nanofibers with inorganic particles) ensures sufficient puncture strength at this critical interface location.
3Ease of manufacture
If a coating layer is integrated with the electrode active material layer to function as a separator, then the manufacturing process is simplified, but the tensile strength is reduced
Solution Approach 1:
The coating layer formation process merges the separator function with the electrode structure, eliminating the need for separate separator manufacturing and assembly steps. The combined structure uses polymer nanofibers reinforced with inorganic particles to maintain adequate tensile strength while simplifying the overall manufacturing process.
Data Source
AI summary
An electrode assembly and a rechargeable lithium battery including the same are provided. The electrode assembly includes a current collector; an electrode active material layer on the current collector; and a coating layer combined with the electrode active material layer. The coating layer includes polymer nanofibers each including a structural unit derived from a fluorine-based polymer and a structural unit derived from a nitrile-based polymer; and inorganic particles. The coating layer has a puncture strength of about 15 to about 100 gram force (gf) and a tensile strength of about 120 to about 1,000 kilogram force per square centimeter (kgf/cm2).