Anode Slurry Composition for Stronger Li-Ion Electrode Adhesion
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Solution Overview
Problem
Existing thickeners for Li-ion battery anode active material slurries, such as carboxymethyl cellulose and hydrophobically modified alkali-swellable emulsions, face challenges including brittleness, pH restrictions, and formulation dependency, which affect electrode adhesion and stability.
Innovation Solution
An anode active material slurry comprising 80-98 wt.% anode active material, 0-5 wt.% conductive material, 0.1-5 wt.% alkali-swellable emulsion (ASE) as thickener, and optional latex binder and further components, where the ASE is a non-hydrophobically modified copolymerizate of nonionic monomers and olefinically unsaturated carboxylic acids, providing improved adhesion and formulation robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If carboxymethyl cellulose is used as thickener, then the slurry has appropriate viscosity for coating, but the dried electrode becomes brittle and adhesion deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters of the thickener from carboxymethyl cellulose to a specific copolymer composition containing acrylic acid, methacrylic acid, and hydrophilic monomers in controlled ratios. This parameter change maintains the required slurry viscosity while eliminating the brittleness and adhesion problems of CMC, achieving both coating performance and electrode strength
Solution Approach 2:
The invention uses a composite polymer structure combining multiple functional monomers (acrylic acid for adhesion, methacrylic acid for viscosity, and hydrophilic monomers for flexibility) to create a thickener that simultaneously provides coating viscosity and prevents brittleness, resolving the contradiction between ease of operation and strength
2Strength
If hydrophobically modified alkali-swellable emulsion is used as thickener, then electrode adhesion increases, but formulation dependency and pH restrictions increase
Solution Approach 1:
The invention modifies the chemical parameters by using unmodified alkali-swellable emulsion with specific monomer composition (acrylic acid 20-40%, methacrylic acid 10-30%, hydrophilic monomers 30-60%) and controlled molecular weight (50,000-200,000). This parameter optimization achieves strong adhesion while reducing pH restrictions and formulation dependency, enhancing adaptability
Solution Approach 2:
The invention extracts the hydrophobic modification from the alkali-swellable emulsion, using only the unmodified base polymer with controlled composition. This removal of hydrophobic groups reduces the complexity of interactions with other formulation ingredients, decreasing formulation dependency while maintaining adhesion benefits
3Quantity of substance
If high active material content is used in electrode, then energy density increases, but adhesion deteriorates due to thickener limitations
Solution Approach 1:
The invention changes the thickener composition parameters to a copolymer with optimized ratios of acrylic acid (20-40%), methacrylic acid (10-30%), and hydrophilic monomers (30-60%), with molecular weight控制在50,000-200,000。This parameter optimization provides sufficient adhesion even at high active material content (90-98 wt%), enabling high energy density while maintaining electrode integrity
Solution Approach 2:
The invention employs a composite polymer thickener combining multiple monomer components that work synergistically: acrylic acid for adhesion to current collector, methacrylic acid for viscosity control, and hydrophilic monomers for flexibility and crack prevention. This composite structure enables high active material loading while maintaining strong adhesion
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 use of non-hydrophobically modified alkali-swellable emulsions as thickeners in the anode active material slurry significantly enhances the adhesion force of the anode active material layer to the current collector, reducing delamination and improving the overall stability and performance of Li-ion batteries.
Implementation Method 1
0.1 to 5 wt.% of at least one alkali-swellable emulsion (6)
Data Source
AI summary
The present invention relates to an anode active material slurry (1) for coating an anode current collector (2) for a secondary Li-ion battery (3), wherein the slurry (1) comprises i) 80 to 98 wt.% of at least one anode active material (4); ii) 0 to 5 wt.% of at least one conductive material (5); iii) 0.1 to 5 wt.% of at least one alkali-swellable emulsion (6); iv) 0 to 5 wt.% of at least one latex binder (7); v) 0 to 5 wt.% of at least one further component (8) selected from a specific group, and vi) at least one solvent (9), in particular water. wherein the at least one alkali-swellable emulsion (6) is an emulsion- or suspension copolymerizate of a nonionic monomer (6a) comprising butadiene, styrene or at least one (meth)acrylate monomer, and optionally acrylonitrile, and an olefinically unsaturated carboxylic acid or olefinically unsaturated carboxylic acid salt (6b), wherein the (meth)acrylate monomer is a C1- to C4- alkyl (meth)acrylate monomer, i.e., the alkali-swellable emulsion (6) is not hydrophobically modified. Claimed also is an anode (10) for the secondary Li-ion battery (3), wherein the anode (10) comprises an anode active material layer (1*) coated on the anode current collector (2), wherein the anode active material layer (1*) is the anode active material slurry (1) when applied onto the anode current collector (2) and dried, the process to make the anode (10) as well as the use of the anode active material slurry (1).