Dry-Processed Lithium-Ion Electrode Sheet for Crack-Resistant Thickness
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Solution Overview
Problem
The manufacturing process of electrode sheets for lithium ion secondary batteries is complex and prone to cracking due to the use of solvents, and fibrous carbon's anisotropic mechanical strength, making it difficult to achieve desired thickness and conductivity.
Innovation Solution
An electrode sheet composed of fibrous carbon and a fluorine-based polymer, without the use of solvents, with a thickness of 50 to 2000 μm and a tensile breaking strength of 0.20 N/mm² or more, where the fibrous carbon has an average fiber diameter of 100 to 900 nm and is packed at 0.8 g/cm³, providing high electrical conductivity and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a slurry containing solvent is used to produce electrode sheets, then the manufacturing process can be completed, but the process becomes complicated and the electrode sheet is likely to crack during drying
Solution Approach 1:
The invention extracts and eliminates the solvent component from the traditional slurry-based electrode sheet manufacturing process. By using a dry mixture of active material, conductive aid, and binder without solvent, the process avoids the complicated drying step that causes cracking, thereby improving both manufacturing simplicity and crack resistance.
Solution Approach 2:
The invention changes the physical state parameter of the electrode mixture from a wet slurry to a dry powder mixture. This parameter change eliminates the need for solvent removal and prevents cracking associated with drying, while still enabling successful electrode sheet formation through direct compression and lamination.
2Reliability
If fibrous carbon is used as conductive aid to improve conductivity, then electrical conductivity improves, but the electrode sheet exhibits anisotropy in mechanical strength
Solution Approach 1:
The invention applies local quality by using fibrous carbon with specific aspect ratios (length/diameter) to create conductive pathways in critical areas while maintaining overall mechanical uniformity. The fibrous carbon is distributed to provide localized conductivity enhancement without compromising the isotropic mechanical properties of the entire electrode sheet.
Solution Approach 2:
The invention uses a composite material system combining fibrous carbon with particulate conductive aids and binder in a dry mixture. This composite approach allows the fibrous carbon to provide conductivity while the binder and particle matrix maintain mechanical strength uniformity, resolving the anisotropy problem.
3Quantity of substance
If the electrode sheet thickness is increased, then more active material can be incorporated, but the electrode sheet is likely to crack in the drying process
Solution Approach 1:
By removing the solvent drying step through extraction of the liquid component, the invention enables production of thicker electrode sheets without the cracking problem that occurs during solvent evaporation. The dry processing method allows greater thickness while maintaining structural integrity.
Solution Approach 2:
The invention changes the processing parameter from wet slurry application to dry powder compression. This parameter change allows thicker electrode sheets to be manufactured without the drying-induced cracking that limits thickness in conventional processes.
Data Source
AI summary
The present invention provides an electrode sheet for a lithium ion secondary battery containing at least a lithium ion battery active material, fibrous carbon, and a fluorine-based polymer. This electrode sheet for a lithium ion secondary battery is characterized by having the film thickness of 50-2000 (μm), the tensile breaking strength of at least 0.2 (N/mm2), the average fiber diameter of the fibrous carbon of 100-900 (nm), and the fibrous carbon content of 0.1-10 (mass %) in the electrode sheet.