Battery Electrode Slurry Shear Control for Surface Flatness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for producing battery electrodes with silicon-containing negative electrode active materials face challenges in achieving high energy density due to structural disorder caused by the expansion and contraction of the active material, leading to uneven surface flatness and reduced battery capacity.
Innovation Solution
A method involving a specific shear rate-shear stress profile for the electrode active material slurry, with a core-shell structure using a polyurethane or vinyl-based resin coating agent, and a binder content of 1% or less, to improve surface flatness and energy density without increasing binder amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If cross-linked polyacrylic acid or neutralized product is used as a binder to suppress structural disorder, then structural stability is improved, but fluidity of the slurry decreases and surface flatness deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by using polyacrylic acid without cross-linking or with minimal cross-linking, and by selecting specific neutralization agents (amines or organic bases) to achieve the desired balance between structural stability and slurry fluidity. This parameter change resolves the contradiction by eliminating the cross-linking step that causes thixotropy while maintaining binding effectiveness through controlled neutralization.
Solution Approach 2:
The invention creates a composite binder system combining polyacrylic acid with specific neutralization agents (amines or organic bases) in controlled ratios. This composite approach allows the binder to provide structural stability through the polyacrylic acid framework while maintaining fluidity through the neutralization reaction products, thus resolving the contradiction between stability and surface flatness.
2Stability of the object's composition
If binder content is increased to suppress structural disorder, then structural stability is improved, but energy density decreases
Solution Approach 1:
The invention changes the binder content parameter to 1% by mass or less, which is a significant reduction from conventional amounts. This parameter change is made possible by using polyacrylic acid with controlled neutralization, which provides higher binding efficiency per unit mass. This resolves the contradiction by achieving structural stability with minimal binder content, thereby maximizing energy density.
3Stability of the object's composition
If slurry viscosity is high to suppress structural disorder, then structural stability is improved, but coating flatness deteriorates
Solution Approach 1:
The invention changes the viscosity parameter of the slurry by controlling the binder composition (polyacrylic acid with amine or organic base neutralization) and optimizing the solid content concentration. This creates a slurry with appropriate viscosity that maintains structural stability during storage and handling while flowing smoothly during coating to achieve flat surfaces, thus resolving the contradiction.
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
This approach results in a battery electrode with enhanced surface flatness, increased energy density, and improved cycle durability, effectively addressing the structural issues and capacity limitations of previous techniques.
Implementation Method 1
the flow characteristics of the slurry becomes thixotropic
Implementation Method 2
a shell portion comprising a coating agent containing a coating resin comprising a polyurethane resin or a vinyl-based resin is formed on at least a part of the surface of a core portion comprising the electrode active material
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Provided is a means capable of improving the flatness of a surface of an electrode active material layer in which an electrode active material slurry without assuming addition of a binder. Upon producing a battery electrode which has a current collector and an electrode active material layer disposed on a surface of the current collector and containing an electrode active material, in a coating step of coating an electrode active material slurry in which the electrode active material is dispersed in a solvent on the surface of the current collector to form the electrode active material layer, an electrode active material slurry which has flow characteristics that a region A in which a shear stress is not increased according to an increase in shear rate is present and a region B in which a shear stress is increased and an increase rate thereof is decreased according to an increase in shear rate is present in a region having a shear rate larger than that of the region A, in a shear rate (horizontal axis)-shear stress (vertical axis) curve of the electrode active material slurry, is used as the electrode active material slurry, and, coating of the electrode active material slurry is performed at a coating rate at which the shear rate at the time of coating is a value in which a shear stress equal to or more than a yield stress of the electrode active material slurry is applied in the coating step.