Cathode Active Material Coating for Battery Adhesion

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Lithium secondary batteries face issues with cathode active material degradation due to volume expansion, separation from current collectors, and side reactions, leading to reduced performance and lifespan, especially when using conventional binders like PVdF which can decompose under moisture exposure.

Innovation Solution

A cathode active material coated with a carboxymethyl cellulose derivative is used, enhancing adhesion and dispersion, forming a film that prevents metal elution and reduces volume expansion, combined with a rubber-based binder for improved adhesion and stress absorption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If PVdF is used as a binder, then adhesion is provided, but moisture permeation causes HF formation and metal layer decomposition

Engineering Contradiction:

ImproveadhesionVSAvoidmoisture permeation and metal decomposition

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

A water-based binder system is introduced as an intermediary between the cathode active material and current collector, replacing PVdF to eliminate moisture-related decomposition while maintaining adhesion through rubber-based latexes and carboxymethyl cellulose derivatives

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The binder chemistry is fundamentally changed from fluoropolymer (PVdF) to water-based systems (rubber latexes and carboxymethyl cellulose), altering the chemical parameters to eliminate HF formation and metal decomposition while preserving adhesion functionality

Inventive Principle:

Principle #35Parameter changes

2Duration of action of stationary object

If SBR is used as a water-based binder, then adhesion sustainability is enhanced, but adhesion effects remain low for high-capacity active materials

Engineering Contradiction:

Improveadhesion sustainabilityVSAvoidadhesion effect

Core Design Contradiction:

Duration of action of stationary objectVSStrength

Solution Approach 1:

A composite binder system is created by combining rubber-based latexes (for elasticity and adhesion sustainability) with carboxymethyl cellulose derivatives (for enhanced adhesion strength), achieving both long-term sustainability and strong initial adhesion required for high-capacity active materials

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention merges the advantages of two different water-based binder systems (rubber latexes and carboxymethyl cellulose derivatives) into a single composite binder that simultaneously provides adhesion sustainability and strong adhesion effects

Inventive Principle:

Principle #5Merging (Combining)

3Use of energy by moving object

If cathode active material volume changes during charging and discharging, then lithium ion intercalation and deintercalation occur, but separation and adhesion loss occur

Engineering Contradiction:

Improvelithium ion intercalation and deintercalationVSAvoidcathode structure stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The elastic rubber-based binder and carboxymethyl cellulose derivative coating are applied beforehand to the cathode active material particles, creating a cushioning layer that absorbs and accommodates volume changes during lithium ion intercalation and deintercalation, preventing separation and adhesion loss

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

A flexible binder system comprising rubber-based latexes and carboxymethyl cellulose derivatives forms a thin film around cathode active material particles, allowing the film to flex and accommodate volume changes during charging and discharging cycles while maintaining structural integrity and adhesion

Inventive Principle:

Principle #30Flexible shells and thin films

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 solution results in enhanced high-voltage and high-temperature performance, improved cycle stability, and extended lifespan of lithium secondary batteries by preventing metal elution and controlling volume expansion.

Implementation Method 1

a carboxymethyl cellulose derivative is coated on surfaces of particles of a lithium transition metal oxide

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

the carboxymethyl cellulose derivative serves as a thickening agent, facilitates dispersion of the cathode active material, and forms a film at a cathode surface

Methodology Applied

Scientific EffectDispersion: Dispersion (of waves)

Implementation Method 3

adhesion sustainability of SBR is enhanced due to elasticity of rubber

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS9812708B2Cathode active material and lithium secondary battery comprising same

Publication Date: 2017.11.07 LG ENERGY SOLUTION LTD

AI summary

Disclosed is a cathode active material for secondary batteries in which a carboxymethyl cellulose derivative is coated on surfaces of particles of a lithium transition metal oxide having the formula LixMyO2 where M: NiaMnbCoc wherein 0≦a≦0.9, 0≦b≦0.9, 0≦c≦0.5, and 0.85≦a+b+c≦1.05 and x+y=2, wherein 0.95≦x≦1.15.