Silicon Negative Electrode Adhesive Dot Pattern for Battery Cycle Life

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Solution Overview

Problem

Rechargeable lithium batteries face challenges in suppressing the volume extraction and expansion of silicon-based negative active materials during charging and discharging, which affects their energy density and cycle-life characteristics.

Innovation Solution

A negative electrode with a silicon-based active material and an adhesive layer, comprising an acryl-based and fluorine-based binder, is developed. The adhesive layer is thin (≤5 μm) and covers about 50% of the active material layer in a dot pattern, improving stiffness and adhesion while minimizing electrical resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the negative active material layer is thickly formed to improve energy density, then the energy density increases, but the volume extraction and expansion during charging and discharging becomes more severe

Engineering Contradiction:

Improveenergy densityVSAvoidvolume stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent divides the adhesive layer into multiple discrete dots distributed across the negative active material layer, rather than using a continuous adhesive layer. This segmentation allows the adhesive dots to provide localized support and constrain volume changes at specific points where silicon-based materials undergo expansion and contraction, while maintaining overall structural flexibility and lithium ion mobility throughout the layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The adhesive layer is applied non-uniformly as discrete dots with specific area ratios (5-50% of total layer area) rather than as a continuous uniform layer. This local quality approach concentrates adhesive support where needed to suppress volume extraction and expansion, while leaving other areas open for efficient lithium ion transport, thus resolving the contradiction between structural stability and ion mobility.

Inventive Principle:

Principle #3Local quality

2Reliability

If an adhesive layer is added to suppress volume extraction and expansion, then the cycle-life characteristics improve, but the electrical resistance increases

Engineering Contradiction:

Improvecycle-life characteristicsVSAvoidelectrical resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

By segmenting the adhesive layer into discrete dots rather than using a continuous layer, the patent minimizes the total area occupied by adhesive material. This segmentation reduces the overall electrical resistance introduced by the adhesive while maintaining sufficient adhesion and structural support at critical locations to improve cycle-life characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies adhesive layer only partially (5-50% area ratio) rather than covering the entire negative active material layer. This partial action provides just enough adhesive support to suppress volume extraction and expansion and improve cycle life, while minimizing the harmful effect of electrical resistance by reducing the total adhesive material present.

Inventive Principle:

Principle #16Partial or excessive action

3Strength

If the adhesive layer thickness is increased to improve adhesion, then the adherence improves, but the bending strength increases excessively affecting lithium ion mobility

Engineering Contradiction:

ImproveadherenceVSAvoidlithium ion mobility

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The adhesive layer is segmented into discrete dots with controlled thickness (1-5 μm), preventing the formation of a thick continuous barrier. This segmentation maintains sufficient adherence strength at contact points while ensuring that the overall structure remains flexible enough to allow lithium ion mobility, resolving the contradiction between adhesion strength and ion transport ease.

Inventive Principle:

Principle #1Segmentation

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 reduces volume contraction and expansion, enhancing the cycle-life characteristics and energy density of the lithium battery by maintaining structural integrity and lithium ion mobility.

Implementation Method 1

an adhesive layer on the negative active material layer... exhibiting good adherence

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 2

The adhesive layer may include an acryl-based binder and a fluorine-based binder

Methodology Applied

Scientific EffectPolymer bonding: Chemical Bonding

Data Source

PatentUS20230122468A1Negative electrode for rechargeable lithium battery and rechargeable lithium battery including same

Publication Date: 2023.04.20 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 including a current collector, a negative active material layer on the current collector, including a silicon-based negative active material, and an adhesive layer on the negative active material layer, wherein the adhesive layer has a thickness of about 5 μm or less, the adhesive layer has an area of about 50 area % based on the total area of the negative active material layer, and the adhesive layer is positioned in a dot pattern.