Low-Oxygen Graphite Anodes to Prevent Electrode Expansion

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Solution Overview

Problem

Graphite particles coated with amorphous carbon for lithium-ion secondary cells can develop cracks during high-pressure pressing, leading to reactions with the electrolyte and expansion of the negative electrode, which compromises cell performance.

Innovation Solution

Using carbon particles with an oxygen content of 0.005% to 0.15% by mass, which are preferably graphite particles or spherical graphite, to create a negative electrode material that maintains favorable storage properties without an amorphous carbon coating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If graphite particles are coated with amorphous carbon to improve charge/discharge rate and suppress side reactions, then cell performance is improved, but cracks form in the coating during high-pressure pressing leading to electrolyte reactions and electrode expansion

Engineering Contradiction:

Improvecell performanceVSAvoidcoating integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The invention removes the amorphous carbon coating entirely and instead uses controlled oxygen content within graphite particles (0.03-0.20 mass%) to achieve the desired performance. This extracts the problematic coating while retaining the protective and performance-enhancing functions through a different mechanism.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the chemical composition parameter of the graphite particles by controlling the oxygen content within a specific range (0.03-0.20 mass%). This parameter change allows the graphite to maintain structural integrity during pressing while still providing improved charge/discharge rates and suppressed side reactions, eliminating the need for the coating.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If amorphous carbon coating is applied to suppress side reactions with electrolyte, then storage properties are improved, but the coating cracks during manufacturing causing harmful reactions

Engineering Contradiction:

Improvestorage propertiesVSAvoidreaction with electrolyte

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention removes the amorphous carbon coating that caused cracking and subsequent electrolyte reactions, while achieving the same protective effect through controlled oxygen content within the graphite particles themselves.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The oxygen content within the graphite particles acts as an intermediary that provides protection against electrolyte reactions without forming a separate coating layer. The controlled oxygen (0.03-0.20 mass%) serves as a built-in protective mechanism that prevents harmful side reactions while maintaining structural integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If amorphous carbon coating is used to improve charge/discharge rate, then cell performance is enhanced, but the harder coating creates cracks under pressing pressure

Engineering Contradiction:

Improvecharge/discharge rateVSAvoidcoating hardness

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The invention removes the hard amorphous carbon coating that provided fast charge/discharge rates but caused cracking under pressure, and instead achieves enhanced productivity through controlled oxygen content within the graphite particles.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the chemical parameter (oxygen content: 0.03-0.20 mass%) of the graphite particles to achieve improved charge/discharge rates without the need for a hard coating. This parameter change maintains structural integrity while providing the desired performance enhancement.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3886222B1Negative electrode material for lithium-ion secondary cell, method for manufacturing negative electrode material for lithium-ion secondary cell, negative electrode material slurry for lithium-ion secondary cell, negative electrode for lithium-ion secondary cell, and lithium-ion secondary cell

Publication Date: 2025.02.12 RESONAC CORP

Figure 1

AI summary

A negative electrode material for a lithium-ion secondary cell, comprising carbon particles having an oxygen content of 0.15% by mass or less.