Conductive Undercoat Layer for Battery Electrode Adhesion

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Solution Overview

Problem

The adhesiveness between the current collector and the electrode mixture layer in lithium ion secondary batteries is insufficient, leading to issues like minute short circuits, battery capacity variation, and safety concerns due to swelling and increased contact resistance over time.

Innovation Solution

A thin film forming composition comprising a conductive carbon material, a dispersant, a solvent, and a polymer with a pendant chain structure is used to form an undercoat layer that enhances adhesion between the current collector and the electrode mixture layer, reducing resistance and preventing capacity deterioration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional binder is used to bond the electrode mixture to the current collector, then the electrode structure is formed, but the adhesion is insufficient leading to material stripping and short circuits

Engineering Contradiction:

Improveadhesion between electrode mixture and current collectorVSAvoidmaterial stripping and short circuits

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A conductive undercoat layer is introduced as an intermediary between the current collector and the electrode mixture layer. This undercoat layer serves as a mediator that enhances adhesion and provides electrical conductivity, preventing material stripping and short circuits while maintaining good contact between the electrode mixture and current collector.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The current collector is constructed as a composite structure consisting of a metal foil base layer and a conductive undercoat layer. This composite material approach combines the mechanical strength of the metal foil with the enhanced adhesion and conductivity properties of the undercoat layer, resolving the adhesion insufficiency problem.

Inventive Principle:

Principle #40Composite materials

2Duration of action of stationary object

If the binder is used to hold the electrode components together, then the electrode structure is maintained, but long-term use causes swelling and volume change leading to increased contact resistance

Engineering Contradiction:

Improvebattery lifespanVSAvoidcontact resistance stability

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The conductive undercoat layer acts as a buffer and intermediary that accommodates the swelling and volume changes of the binder and active material during battery cycling. This undercoat layer maintains stable electrical contact between the current collector and electrode mixture, preventing increased contact resistance over time.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the structural parameters of the current collector by adding a conductive undercoat layer with different mechanical and electrical properties. This undercoat layer has parameters optimized for adhesion and conductivity stability, compensating for the parameter changes (swelling, volume change) that occur in the binder and active material during long-term use.

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 composition effectively improves the adhesion between the current collector and the electrode mixture layer, enhancing the performance and longevity of lithium ion secondary batteries by reducing internal resistance and preventing capacity loss.

Implementation Method 1

a polymer having a pendant chain having a partial structure of formula (P1)... improves the adhesion between a current collector and an electrode mixture layer

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 2

a conductive layer including carbon as a conductive filler is disposed as an undercoat layer... the contact resistance between the current collector and the electrode mixture layer can be reduced

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS11670777B2Thin film forming composition for energy storage device electrodes

Publication Date: 2023.06.06 NISSAN CHEM CORP

AI summary

The present invention provides a thin film forming composition for energy storage device electrodes, said composition containing a conductive carbon material, a dispersant, a solvent and a polymer that has a partial structure represented by formula (P1) in a side chain.(In the formula, L represents —O— or —NH—; R represents an alkylene group having from 1 to 20 carbon atoms; T represents a substituted or unsubstituted amino group, a nitrogen-containing heteroaryl group having from 2 to 20 carbon atoms or a nitrogen-containing aliphatic heterocyclic group having from 2 to 20 carbon atoms; and * represents a bonding hand.)