Three-Layer Silicon-Carbon Negative Electrode for Swelling Control

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Solution Overview

Problem

Rechargeable lithium batteries face challenges in achieving low volume expansion and maintaining excellent life cycle characteristics, which are crucial for high-capacity and lightweight electronic devices.

Innovation Solution

A negative electrode for rechargeable lithium batteries is designed with a three-layer structure, comprising a first crystalline carbon layer, a silicon layer with a Si-carbon composite as the active material, and a second crystalline carbon layer. The silicon layer is positioned between the carbon layers, and its thickness is optimized to be about 3% to 35% of the total negative active material layer thickness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a silicon layer is added to increase battery capacity, then the energy storage capacity is improved, but the volume expansion during charging and discharging increases

Engineering Contradiction:

Improvebattery capacityVSAvoidvolume expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The silicon layer is nested between two crystalline carbon layers, forming a sandwich structure where the carbon layers contain and constrain the silicon layer. This nesting approach allows the high-capacity silicon to be enclosed within a low-expansion carbon matrix, enabling the silicon to expand and contract during lithiation/delithiation while the outer carbon layers maintain overall structural integrity and limit volume expansion.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The negative electrode uses a composite structure combining silicon and crystalline carbon materials. The silicon layer provides high capacity while the crystalline carbon layers provide structural stability and low expansion. This composite material approach leverages the complementary properties of both materials to achieve both high capacity and low volume expansion simultaneously.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If the silicon layer thickness is increased to improve capacity, then the energy storage is enhanced, but the structural stability and cycle life deteriorate

Engineering Contradiction:

Improveenergy storageVSAvoidcycle life

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The negative electrode structure assigns different local functions to different layers: the silicon layer is optimized for high capacity with thickness of 3-35% of the total active material layer, while the crystalline carbon layers are optimized for structural stability. This local quality differentiation allows each layer to perform its specific function optimally, with the silicon providing capacity and the carbon layers providing stability, thereby achieving both high energy storage and excellent cycle life.

Inventive Principle:

Principle #3Local quality

3Reliability

If a three-layer structure is implemented to suppress volume expansion, then the cycle life is improved, but the device complexity increases

Engineering Contradiction:

Improvecycle lifeVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The negative active material layer is segmented into three distinct functional layers: a first crystalline carbon layer, a silicon layer, and a second crystalline carbon layer. This segmentation allows each layer to perform its specific function - the carbon layers suppress volume expansion and the silicon layer provides capacity - while maintaining a relatively simple overall sandwich structure that is easier to manufacture than more complex alternatives.

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

This configuration effectively suppresses volume expansion during charging and discharging, thereby enhancing the cycle-life characteristics and maintaining high capacity of the lithium battery.

Implementation Method 1

each of which include an active material capable of intercalating and deintercalating lithium ions

Methodology Applied

Scientific EffectIntercalation: Absorption (physical)

Implementation Method 2

A rechargeable lithium battery generates electrical energy due to the oxidation and reduction reactions that occur when lithium ions are intercalated and deintercalated

Methodology Applied

Scientific EffectReduction reaction: Reduction

Implementation Method 3

A rechargeable lithium battery generates electrical energy due to the oxidation and reduction reactions that occur when lithium ions are intercalated and deintercalated

Methodology Applied

Scientific EffectOxidation reaction: Oxidation

Data Source

PatentUS20250062321A1Negative electrode for rechargeable lithium battery and rechargeable lithium battery including same

Publication Date: 2025.02.20 SAMSUNG SDI CO LTD

AI summary

A negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same are provided. The negative electrode includes a current collector; and a negative active material layer on at least one surface of the current collector, wherein the negative active material layer comprises a first crystalline carbon layer in contact with the current collector, a silicon layer on the first crystalline carbon layer and comprising a Si-carbon composite, and a second crystalline carbon layer on the silicon layer, and a thickness of the silicon layer is about 3% to about 35% based on a total thickness of the negative active material layer.