Cross-linked Copolymer Binder for Silicon Electrodes

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Solution Overview

Problem

Conventional binders for secondary battery electrodes, such as carboxymethylcellulose and styrene butadiene rubber, fail to effectively control structural deformation due to volume expansion of silicon-based active materials during charging and discharging, leading to electrode separation and increased resistance, which deteriorates battery performance and life-time characteristics.

Innovation Solution

A cross-linked copolymer binder comprising a polyvinyl alcohol-derived unit and an ionically substituted acrylate-derived unit is used, providing enhanced elasticity and adhesion through hydrogen and ionic bonding, which helps maintain the conductive path and suppress volume expansion of the electrode active material.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional binders (CMC, SBR) are used to suppress electrode deformation, then adhesion is improved, but the conductive path is difficult to ensure and resistance increases

Engineering Contradiction:

ImproveadhesionVSAvoidconductive path

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention uses a composite binder system comprising both carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) in a specific weight ratio range (SBR/CMC = 0.3 to 2.0). This composite approach combines the adhesive strength of CMC with the flexibility and conductive path maintenance of SBR, resolving the contradiction between adhesion and conductivity by leveraging the complementary properties of both materials

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention optimizes the weight ratio parameter of SBR to CMC within a specific range (0.3 to 2.0) to achieve the best balance between adhesion and conductive path maintenance. By adjusting this compositional parameter, the binder system can effectively suppress electrode deformation while maintaining adequate conductivity, resolving the contradiction through parameter optimization

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If silicon-based active material is used to improve capacity, then energy density is improved, but volume expansion occurs causing electrode structure deformation

Engineering Contradiction:

ImprovecapacityVSAvoidelectrode structure

Core Design Contradiction:

Quantity of substanceVSShape

Solution Approach 1:

The invention applies beforehand cushioning by using a dual-binder system (CMC and SBR) that is pre-configured to accommodate and cushion the volume expansion of silicon-based active material during lithiation. The CMC provides structural framework that resists deformation while SBR provides flexibility to accommodate expansion, together cushioning the shape changes before they cause electrode structure failure

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The composite binder system combines CMC's structural stability with SBR's flexibility to create a matrix that can handle the volume expansion of silicon-based active material. This composite approach allows the electrode to maintain structural integrity while accommodating the capacity benefits of silicon, resolving the contradiction between capacity and shape stability

Inventive Principle:

Principle #40Composite materials

3Strength

If electrode structure deforms due to volume expansion, then adhesion is maintained, but separation between active material and current collector occurs

Engineering Contradiction:

ImproveadhesionVSAvoidelectrode integrity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention optimizes the CMC and SBR content parameters within specific ranges to achieve the best balance between adhesion and electrode integrity. By controlling the total binder content and the SBR/CMC ratio within specified ranges, the electrode maintains strong adhesion to the current collector while preventing separation caused by volume expansion, resolving the contradiction through parameter optimization

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 new binder effectively controls structural changes during charging and discharging, improving the conductivity and life-time characteristics of the battery by maintaining the conductive path and reducing electrode resistance.

Implementation Method 1

providing enhanced elasticity and adhesion through hydrogen and ionic bonding

Methodology Applied

Scientific EffectHydrogen bonding:

Implementation Method 2

providing enhanced elasticity and adhesion through hydrogen and ionic bonding

Methodology Applied

Scientific EffectIonic bonding:

Implementation Method 3

providing enhanced elasticity and adhesion

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS11600823B2Binder for secondary battery electrode, secondary battery electrode and secondary battery including same, composition for secondary battery electrode for producing said secondary battery electrode, and method for producing said secondary battery electrode

Publication Date: 2023.03.07 LG ENERGY SOLUTION LTD

AI summary

The present invention provides a binder for a secondary battery electrode, a secondary battery electrode and secondary battery including the same, a composition for a secondary battery electrode for producing the secondary battery electrode, and a method for producing the secondary battery electrode, wherein in the binder for a secondary battery electrode, a copolymer includes a polyvinyl alcohol-derived unit and an ionically substituted acrylate-derived unit, and is cross-linked to each other.