Silicon Anode Composition for Expansion Control and Cycle Life

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Solution Overview

Problem

Rechargeable lithium batteries face challenges in maintaining excellent cycle-life characteristics while ensuring good expansion reduction and electrical conductivity.

Innovation Solution

A negative electrode for rechargeable lithium batteries is designed with a Si-including negative active material, a binder comprising a copolymer with acryl and cyano groups, a linear carbon conductive material, a dispersant, and an additive with OH functional groups to enhance dispersibility and reduce volume expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a Si-including negative active material is used to increase capacity, then the battery capacity is improved, but volume expansion occurs during charge-discharge cycles

Engineering Contradiction:

Improvebattery capacityVSAvoidvolume expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The patent uses a binder comprising a copolymer of acryl and cyano groups that forms a flexible coating film around the Si-including negative active material particles. This flexible film accommodates the volume expansion of silicon during lithium insertion while maintaining structural integrity, preventing particle disintegration and electrode degradation.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent creates a composite structure by combining Si-including negative active material with carbon materials (graphite, amorphous carbon) and a polymer binder. The carbon matrix provides structural stability while the silicon particles provide high capacity, and the copolymer binder holds the composite structure together during volume changes.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the electrode structure is optimized to reduce volume expansion, then cycle-life is improved, but electrical conductivity may deteriorate

Engineering Contradiction:

Improvecycle-life characteristicVSAvoidelectrical conductivity

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent introduces a linear carbon conductive material as an intermediary between the Si-including negative active material particles and the current collector. This carbon network maintains electrical conductivity pathways even when the silicon expands and contracts, ensuring continuous electron transport while the copolymer binder maintains structural integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical composition parameters of the binder by using a copolymer with specific ratios of acryl and cyano groups. This compositional change optimizes both the binding strength to maintain structure during volume changes and the electrical conductivity through the electrode, achieving a balance between cycle-life and conductivity.

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If a copolymer binder including acryl and cyano groups is used to suppress volume expansion, then expansion reduction is achieved, but the complexity of binder synthesis increases

Engineering Contradiction:

Improvevolume expansion reductionVSAvoidbinder synthesis complexity

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The patent uses a copolymer with a specific composition ratio (acryl group 30-70 wt%, cyano group 30-70 wt%) to achieve optimal performance. This parameter optimization allows the binder to provide both structural support during volume expansion and adequate electrical conductivity, while the synthesis complexity remains manageable through conventional copolymerization methods.

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 solution effectively suppresses volume expansion, maintains electrical conductivity, and improves cycle-life retention, resulting in enhanced electrochemical performance.

Implementation Method 1

an additive having one or more OH functional groups (multifunctional hydroxyl group) and being capable of adsorbing to a surface of the dispersant

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

a negative electrode and a positive electrode including an active material capable of intercalating and deintercalating lithium ions

Methodology Applied

Scientific EffectIntercalation:

Implementation Method 3

electrical energy is produced by oxidation and reduction reactions if lithium ions are intercalated/deintercalated at the positive and negative electrodes

Methodology Applied

Scientific EffectOxidation and reduction reactions: Redox Reactions

Implementation Method 4

the binder is a copolymer including an acryl group and a cyano group... exhibits excellent cycle-life characteristic, while good expansion reduction effect

Methodology Applied

Scientific EffectVolume expansion suppression:

Data Source

PatentUS20260018618A1Negative electrode for rechargeable lithium battery and rechargeable lithium battery including same

Publication Date: 2026.01.15 SAMSUNG SDI CO LTD

AI summary

Disclosed are a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same. The negative electrode for the rechargeable lithium battery includes a negative active material layer including a Si-including negative active material, a binder, a linear carbon conductive material, a dispersant, an additive having one or more OH functional groups (multifunctional hydroxyl group) and being capable of adsorbing to a surface of the dispersant.