Aqueous Anode Binder Composition for Swelling and Adhesion Control
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Solution Overview
Problem
Existing binders for anodes in lithium ion secondary batteries exhibit insufficient strength and adhesion, leading to material breaks during volume expansion and shrinkage due to lithium intercalation and disintercalation, and require high anode material density with low binder content.
Innovation Solution
An aqueous dispersion of a polymer P, produced by radically initiated emulsion polymerization, comprising specific monomer ratios of vinylaromatic compounds, conjugated aliphatic dienes, and ethylenically unsaturated monomers, is used as a binder in the electrode slurry composition for anodes, enhancing stress/strain behavior and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional binders (styrene/butadiene copolymer) are used in anodes, then the anode material density can be increased with low binder content, but the binder strength is insufficient leading to material breaks during volume expansion and shrinkage
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by incorporating vinylaromatic compounds (40-75 parts), conjugated aliphatic dienes (22.5-55 parts), and ethylenically unsaturated monomers with acid groups (0.5-10 parts) in specific ratios. This compositional parameter change enables the binder to achieve both high strength and adequate elongation, resolving the contradiction between low binder content and sufficient binder strength during anode volume changes.
Solution Approach 2:
The patent creates a composite binder system by copolymerizing multiple monomer types (vinylaromatic compounds, conjugated dienes, and ethylenically unsaturated monomers) to form a polymer with combined properties. This composite polymer structure provides both the strength needed to prevent material breaks and the flexibility to accommodate volume expansion and shrinkage during lithium ion intercalation and deintercalation.
2Quantity of substance
If binder content is reduced to increase anode material density, then energy density improves, but adhesion between binder and anode active material deteriorates
Solution Approach 1:
The patent modifies the binder's chemical parameters by including ethylenically unsaturated monomers containing acid groups (0.5-10 parts per 100 parts total monomers). These acid groups enhance the binder's adhesion properties through chemical interactions with the anode active material surface, allowing reduced binder content while maintaining reliable adhesion.
Solution Approach 2:
The patent applies local quality enhancement by incorporating specific functional groups (acid groups from ethylenically unsaturated monomers) at strategic positions within the binder polymer chain. These localized functional groups provide strong adhesion points between the binder and anode active material, ensuring reliable bonding even when overall binder content is low.
3Ease of manufacture
If conventional styrene/butadiene copolymer binders are used, then manufacturing is simplified, but the binders show insufficient strength and poor stress/strain behavior during charging/discharging cycles
Solution Approach 1:
The patent employs composite material principles by copolymerizing vinylaromatic compounds, conjugated aliphatic dienes, and ethylenically unsaturated monomers in a single emulsion polymerization process. This composite approach maintains manufacturing simplicity while achieving superior binder strength and stress/strain behavior through the synergistic combination of different monomer properties.
Solution Approach 2:
The patent optimizes manufacturing parameters by conducting emulsion polymerization at controlled temperatures (70-95°C) and using specific initiator systems. These parameter changes enable the production of the complex multi-monomer polymer with consistent high strength and good stress/strain behavior, maintaining ease of manufacture while improving performance.
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 polymer P binder effectively suppresses swelling and maintains adhesion during charging/discharging cycles, providing high breaking stress and strain, thus improving the structural integrity of anodes.
Implementation Method 1
The polymer P binder effectively suppresses swelling and maintains adhesion during charging/discharging cycles, providing high breaking stress and strain
Implementation Method 2
An aqueous dispersion of a polymer P, produced by radically initiated emulsion polymerization, comprising specific monomer ratios of vinylaromatic compounds, conjugated aliphatic dienes, and ethylenically unsaturated monomers
Data Source
AI summary
The present invention relates to a method of using an aqueous dispersion of a polymer P obtainable by radically initiated emulsion polymerization, which comprises polymerizing (a) 40 to 75 parts by weight of at least one vinylaromatic compound, (b) 22.5 to 55 parts by weight of at least one conjugated aliphatic diene, (c) 0.5 to 10 parts by weight of at least one ethylenically unsaturated monomer containing acid groups (dl) 1 to 5 parts by weight of acrylamide and/or methacrylamide, (d2) 1 to 10 parts by weight of acrylonitrile and/or methacrylonitrile (e) 0 to 5 parts by weight of monoethylenically unsaturated monomer having at least one epoxy, hydroxyl, N-methylol or carbonyl group (f) 0 bis 20 parts by weight of at least one other monoethylenically unsaturated monomer, where the amounts of the monomers (a) to (f) add up to 100 parts by weight, at a polymerization temperature in the range of 70 to 95° C., as a polymeric binder in an electrode slurry composition for anodes of secondary batteries, aqueous polymer dispersions itself and a process for producing the aqueous dispersion by radically initiated emulsion polymerization, electrode slurry compositions for anodes comprising the polymer P, an anode of secondary batteries comprising the polymer P, a method of preparing this anode and the lithium ion secondary battery comprising the anode.