Water-Soluble Polyamic Acid Binder for Battery Electrodes

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Solution Overview

Problem

Existing polyimide binders for rechargeable batteries face challenges with poor initial formation efficiency due to reactivity with lithium ions and environmental concerns, as they require organic solvents and are not suitable for water-based production processes, while also experiencing issues with volumetric changes in high-capacity negative active materials.

Innovation Solution

A water-soluble binder composition using a polyamic acid with an acid equivalent of 300 to 600 g/eq, which can be converted into a polyimide during drying, offering excellent adhesion and tensile strength while being environmentally friendly and applicable in water-based processes, comprising a mixture of polyamic acids with different structures or molecular weights, and including additives like dispersants, thickeners, and conductive agents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If polyimide binder is used for rechargeable batteries, then adhesion and tensile strength are improved, but initial formation efficiency deteriorates due to reactivity with lithium ions

Engineering Contradiction:

Improveadhesion and tensile strengthVSAvoidinitial formation efficiency

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent changes the chemical structure parameter of the binder by using polyamic acid instead of polyimide, and specifically controls the acid equivalent weight to 300-600 g/eq. This parameter change reduces the reactivity with lithium ions while maintaining the necessary mechanical properties, thereby improving initial formation efficiency without sacrificing adhesion and tensile strength.

Inventive Principle:

Principle #35Parameter changes

2Strength

If polyimide binder is used, then binding performance is improved, but environmental compatibility deteriorates due to requirement of organic solvents

Engineering Contradiction:

Improvebinding performanceVSAvoidenvironmental compatibility

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent changes the solvent system parameter from organic solvents to water, making the binder composition environmentally friendly. The polyamic acid binder is specifically designed to be soluble in water, eliminating the need for harmful organic solvents while maintaining binding performance through controlled acid equivalent weight and molecular structure.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the chemical system (organic solvents) with a different chemical system (water-based solution). By replacing organic solvents with water as the solvent medium, the invention eliminates environmental harm while preserving the binding function through the water-soluble polyamic acid structure.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If existing binder composition is used, then manufacturing process is simple, but adaptability to water-based production processes deteriorates

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidcompatibility with water-based production processes

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent changes the solubility parameter of the binder by designing polyamic acid with specific acid equivalent weight (300-600 g/eq) and appropriate molecular weight, making it soluble in water. This parameter change enables the binder to be used in water-based production processes while maintaining manufacturing simplicity through direct dissolution without complex processing steps.

Inventive Principle:

Principle #35Parameter changes

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 water-soluble binder composition enhances initial formation efficiency and maintains cycle lifetime characteristics by minimizing imide content, ensuring environmental sustainability and compatibility with existing production lines, thus improving the performance and eco-friendliness of rechargeable battery electrodes.

Implementation Method 1

preparing an organic solvent soluble polyamic acid by performing condensation polymerization of one or more aromatic diamine monomers and one or more aromatic acid dianhydride monomers in an organic solvent

Methodology Applied

Scientific EffectCondensation polymerization:

Implementation Method 2

converting the organic solvent soluble polyamic acid into a water soluble polyamic acid, wherein the converting of the organic solvent soluble polyamic acid into the water soluble polyamic acid may include converting a carboxylic acid group of the organic solvent soluble polyamic acid into an amine salt or a metal salt

Methodology Applied

Scientific EffectChemical conversion to salt form:

Implementation Method 3

preparing a polyamic acid dissolved in water by dissolving the polyamic acid powder in a water solution including a water soluble amine compound, a metal hydroxide compound or a metal carbonate compound dissolved therein

Methodology Applied

Scientific EffectDissolution: Solvation

Implementation Method 4

offering excellent adhesion and tensile strength

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS9200116B2Water soluble binder composition, method of producing the same and electrode for rechargeable battery employing

Publication Date: 2015.12.01 SAMSUNG SDI CO LTD

AI summary

A water soluble binder composition for preparing an electrode of a rechargeable battery includes a binder and a conductive agent, the binder including a water soluble polyamic acid having an acid equivalent of about 300 to about 600 g/eq.