Composite Binder Composition for Lithium Battery Electrodes

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Solution Overview

Problem

Lithium batteries face challenges in achieving high energy density and lifespan due to the trade-off between the amount of binder, which affects dispersibility, binding force, and flexibility of electrode active materials and conductive agents, with existing binders either swelling excessively or providing inadequate properties.

Innovation Solution

A binder composition combining a tetrafluoroethylene polymer binder, a vinylidene fluoride binder, and a non-fluoropolymer binder with repeating units derived from acryl and olefin monomers, optimizing flexibility, binding force, and dispersibility to enhance energy density and lifespan characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the amount of binder is decreased to increase energy density, then energy density is improved, but dispersibility and binding force of electrode active material and conductive agent deteriorate

Engineering Contradiction:

Improveenergy densityVSAvoidbinding force

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent uses a composite binder system combining fluoropolymer binder (polyvinylidene fluoride) and non-fluoropolymer binder (hydrogenated acrylonitrile-butadiene) in specific weight ratios (fluoropolymer: 5-40%, non-fluoropolymer: 60-95%). This composite approach allows the fluoropolymer to provide structural stability and low swelling while the non-fluoropolymer enhances binding force and flexibility, achieving both high energy density and reliable electrode integrity with minimized total binder content.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If fluoropolymer binder is used to reduce swelling and improve structure retention, then structure retention is improved, but dispersibility of conductive agent and binding force deteriorate

Engineering Contradiction:

Improvestructure retentionVSAvoiddispersibility of conductive agent

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent combines fluoropolymer binder (providing structure retention and low swelling) with non-fluoropolymer binder (hydrogenated acrylonitrile-butadiene providing improved dispersibility and binding force). The specific weight ratio range (fluoropolymer: 5-40%, non-fluoropolymer: 60-95%) optimizes the balance between structure retention and conductive agent dispersibility, allowing both properties to coexist.

Inventive Principle:

Principle #40Composite materials

3Reliability

If non fluoropolymer binder is used to improve dispersibility and binding force, then dispersibility and binding force are improved, but swelling with electrolytic solution increases excessively

Engineering Contradiction:

Improvebinding forceVSAvoidswelling volume

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent uses a composite binder system where non-fluoropolymer binder (hydrogenated acrylonitrile-butadiene) provides improved binding force and dispersibility, while fluoropolymer binder (polyvinylidene fluoride) constrains excessive swelling. The specific weight ratio (fluoropolymer: 5-40%, non-fluoropolymer: 60-95%) allows the non-fluoropolymer to deliver its binding benefits while the fluoropolymer component limits overall swelling to acceptable levels.

Inventive Principle:

Principle #40Composite materials

4Reliability

If binder amount is increased to improve binding force and flexibility, then binding force and flexibility are improved, but energy density decreases

Engineering Contradiction:

ImproveflexibilityVSAvoidenergy density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent employs a composite binder system that achieves high flexibility and binding force with minimized total binder content. The synergistic combination of fluoropolymer (5-40%) and non-fluoropolymer (60-95%) binders provides enhanced flexibility and binding force per unit weight, allowing reduced overall binder用量 and thereby increasing energy density compared to using single binder types in higher amounts.

Inventive Principle:

Principle #40Composite materials

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 novel binder composition improves the cyclic characteristics of lithium batteries at high voltages, maintaining electrode structure integrity and increasing energy density while maintaining flexibility and binding force, outperforming comparative examples with improved capacity retention ratios.

Implementation Method 1

a fluoropolymer binder, such as a polar functional group-free polyvinylidene fluoride, swells less with respect to an organic electrolytic solution

Methodology Applied

Scientific EffectSwelling resistance:

Implementation Method 2

binding force of the electrode active material and/or the conductive agent

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 3

flexibility of the electrode plate

Methodology Applied

Scientific EffectFlexibility: Elasticity

Implementation Method 4

dispersibility of electrode active material and/or conductive agent

Methodology Applied

Scientific EffectDispersion: Dispersion (of waves)

Data Source

PatentUS9711796B2Binder composition for secondary battery, cathode and lithium battery including the binder composition

Publication Date: 2017.07.18 SAMSUNG SDI CO LTD

AI summary

In an aspect, a binder composition for a secondary battery including a first fluoropolymer binder including a tetrafluoroethylene polymer binder, a second fluoropolymer binder including a vinylidene fluoride binder, and a non fluoropolymer binder is provided.