Low-Oxidation Silicon-Carbon Anode for Crack-Resistant Cycling

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Solution Overview

Problem

Lithium secondary batteries face challenges in achieving high energy and power density due to the low theoretical capacity and high volume change of silicon-based negative electrode materials, leading to particle cracking and reduced discharge capacity.

Innovation Solution

A silicon-carbon composite negative electrode active material with a controlled oxidation degree of 10.5% or less, incorporating silicon nanoparticles and a carbon matrix, and an amorphous carbon coating layer to enhance structural stability and electrochemical performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based negative electrode material is used to achieve high theoretical capacity, then capacity is improved, but volume change up to 300% causes particle cracking and loss of electrical contact

Engineering Contradiction:

Improvetheoretical capacityVSAvoidstructural stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The silicon-based negative electrode material is divided into fine particles with a diameter of 10 μm or less, which reduces the overall volume change impact and prevents particle cracking during charging and discharging cycles

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A composite structure is formed by coating the fine silicon-based particles with a carbon layer, creating a robust composite material that maintains structural integrity while achieving high capacity through the silicon component

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If silicon-based negative electrode material is used to achieve high theoretical capacity, then discharge capacity is improved, but discharge capacity ratio becomes low due to continuous charging and discharging

Engineering Contradiction:

Improvedischarge capacityVSAvoiddischarge capacity ratio

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

Dividing silicon into fine particles reduces volume change during cycling, maintaining electrical contact and preserving discharge capacity ratio over extended battery life

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The carbon-coated silicon composite structure ensures long-term stability by preventing particle degradation, thereby maintaining high discharge capacity ratio across multiple charge-discharge cycles

Inventive Principle:

Principle #40Composite materials

3Reliability

If graphite-based material is used for negative electrode, then excellent capacity retention and efficiency are achieved, but theoretical capacity value is low at 372 mAh/g

Engineering Contradiction:

Improvecapacity retention characteristicsVSAvoidtheoretical capacity value

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The invention creates a composite negative electrode material combining fine silicon-based particles with carbon coating, achieving both high theoretical capacity (3600 mAh/g for Li15Si4) and improved capacity retention through the protective carbon structure

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

By changing the physical state of silicon from bulk to fine particles (10 μm or less diameter), the material achieves both high capacity and acceptable structural stability, bridging the gap between graphite's reliability and silicon's high capacity

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20240055586A1Negative electrode active material for lithium secondary battery, method for preparing same, and lithium secondary battery comprising same

Publication Date: 2024.02.15 POSCO HLDG INC

AI summary

The present embodiments relate to a negative electrode active material for a lithium secondary battery, a method for preparing the same, and a lithium secondary battery comprising the same.The negative electrode active material for a lithium secondary battery, according to one embodiment, comprises a silicon-carbon composite comprising silicon nanoparticles and a carbon matrix, and can have a degree of oxidation that is less than or equal to 10.5%.