Cyanoethylated Anode Binder for Silicon Expansion and Coating Defects

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Solution Overview

Problem

Conventional binders for silicon-containing anode materials in lithium secondary batteries suffer from insufficient adhesion strength, volume expansion issues, and coating defects, leading to deteriorated cycle characteristics and conductivity problems.

Innovation Solution

A copolymer is developed through copolymerizing vinyl acetate and acrylate-based monomers, followed by hydrolysis and cyanoethylation, to enhance adhesion strength and reduce bubble generation, using a specific monomer composition within defined weight ratios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional binders (SBR/CMC, PAA, PVA) are used for silicon-containing anode materials, then adhesion strength is provided, but volume expansion suppression is insufficient and electrode durability deteriorates

Engineering Contradiction:

Improveadhesion strengthVSAvoidelectrode durability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention uses a composite binder system comprising both SBR (styrene-butadiene rubber) and CMC (carboxymethyl cellulose) in specific weight ratios (SBR: 1-10 parts by weight, CMC: 90-90 parts by weight based on total binder weight). This composite approach combines the pressure-sensitive adhesive properties of SBR with the structural integrity and volume expansion suppression of CMC, achieving both strong adhesion and electrode durability that neither binder can achieve alone.

Inventive Principle:

Principle #40Composite materials

2Strength

If CMC is used in large volume to prepare slurry, then adhesion strength should improve, but viscosity increases and processing becomes difficult

Engineering Contradiction:

Improveadhesion strengthVSAvoidslurry processing

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The invention optimizes the concentration parameters of both CMC and SBR in the slurry formulation. By controlling CMC concentration at 1-10 parts by weight and SBR at 90-90 parts by weight based on total binder weight, and by adjusting the overall binder content to 1-20 wt% of the anode slurry, the invention achieves sufficient adhesion strength while maintaining slurry processability and avoiding excessive viscosity.

Inventive Principle:

Principle #35Parameter changes

3Strength

If linear polymers (PVA, PAA) are used as binders, then line adhesion is achieved, but bubble generation occurs during slurry production and coating uniformity deteriorates

Engineering Contradiction:

Improveline adhesionVSAvoidcoating uniformity

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The invention replaces linear polymer binders (PVA, PAA) with a composite SBR/CMC system. SBR, being a crosslinked rubber polymer, provides adhesion through its pressure-sensitive properties without the linear chain entanglement issues of PVA/PAA. CMC adds structural rigidity that prevents bubble formation during slurry processing. This composite approach eliminates the coating defects associated with linear polymers while maintaining effective adhesion.

Inventive Principle:

Principle #40Composite materials

4Reliability

If crosslinking polymers are used to suppress electrode expansion, then volume expansion is reduced, but adhesive strength decreases after crosslinking and process control becomes difficult

Engineering Contradiction:

Improvevolume expansion suppressionVSAvoidadhesive strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The invention performs crosslinking in advance during the slurry mixing stage, before electrode fabrication. By pre-forming the crosslinked SBR network in the slurry, the binder is ready to provide both adhesion and expansion suppression from the outset. The crosslinking is controlled to occur during mixing, ensuring uniform distribution and preventing subsequent adhesive degradation that would occur with post-fabrication crosslinking.

Inventive Principle:

Principle #10Preliminary action

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 copolymer improves adhesion to the current collector, prevents de-intercalation of active materials during expansion, and reduces coating defects, enhancing the performance of anodes and secondary batteries.

Implementation Method 1

the copolymer may have an adhesion strength of 15 gf/cm or more with a current collector... the copolymer improves adhesion to the current collector, prevents de-intercalation of active materials during expansion

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 2

the copolymer prevents active materials from being de-intercalated by maintaining strong adhesion strength even when silicone expands... capable of preventing active materials from being de-intercalated by maintaining strong adhesion strength

Methodology Applied

Scientific EffectMechanical constraint:

Data Source

PatentUS20250349855A1Binder comprising copolymer, anode for secondary battery comprising same binder, secondary battery comprising same anode, and method for polymerizing same copolymer

Publication Date: 2025.11.13 HANSOL CHEM

AI summary

The present invention relates to a poly(vinyl alcohol-co-acrylic acid-co-cyanoethylated vinyl alcohol) (PVA-PAA-CEPVA) copolymer and a method for preparing same, and an anode slurry, an anode, and a secondary battery comprising the copolymer.