Lithium-Ion Battery Negative Electrode Amorphous Carbon Coating

Solution Overview

Problem

Existing lithium ion secondary battery negative electrodes face challenges in durability and gas generation during charging, particularly when excessive amorphous carbon coverage leads to separation issues from the current collector and reduced hydroxyl group affinity, affecting adhesive power and electrolyte decomposition.

Innovation Solution

A negative electrode with a carbon material comprising graphite particles covered by 5 wt% or less amorphous carbon, featuring an uneven and irregular shape, and an aqueous binder to enhance adhesion and prevent aggregation, thereby improving durability and suppressing gas generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If graphite particles are covered with amorphous carbon, then gas generation during charging is suppressed, but adhesive power to current collector decreases and separation issues occur

Engineering Contradiction:

Improvegas generation during chargingVSAvoidadhesive power to current collector

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The patent applies local quality by creating a non-uniform carbon structure where graphite particles have an inner core of crystalline graphite and an outer partial coating of amorphous carbon. This localized differentiation allows the inner graphite to provide structural stability and adhesion while the outer amorphous carbon layer suppresses gas generation, resolving the contradiction between these two opposing requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining crystalline graphite and amorphous carbon in a specific structure. The composite consists of graphite particles partially coated with amorphous carbon, where the amorphous carbon content is controlled to be 5-50 wt%. This composite structure leverages the beneficial properties of both materials: the adhesion and stability of graphite and the gas-suppressing property of amorphous carbon.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If amorphous carbon coverage is increased, then gas generation is suppressed, but hydroxyl group affinity decreases affecting adhesive power

Engineering Contradiction:

Improvegas generation during chargingVSAvoidadhesive power and charge retention

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies parameter changes by precisely controlling the amorphous carbon content within the range of 5-50 wt% of the total carbon material weight. This parameter optimization ensures that there is enough amorphous carbon to suppress gas generation during charging while maintaining sufficient hydroxyl group affinity for adequate adhesive power and charge retention, thus resolving the contradiction.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If regular graphite particles are used, then charge retention is good, but durability and gas generation control are insufficient

Engineering Contradiction:

Improvecharge retentionVSAvoiddurability and gas generation control

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent uses composite materials by combining crystalline graphite and amorphous carbon in a specific structure. The composite consists of graphite particles partially coated with amorphous carbon, where the amorphous carbon content is controlled to be 5-50 wt%. This composite structure leverages the beneficial properties of both materials: the adhesion and stability of graphite and the gas-suppressing property of amorphous carbon.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by creating a non-uniform carbon structure where graphite particles have an inner core of crystalline graphite and an outer partial coating of amorphous carbon. This localized differentiation allows the inner graphite to provide structural stability and adhesion while the outer amorphous carbon layer suppresses gas generation, resolving the contradiction between these two opposing requirements.

Inventive Principle:

Principle #3Local quality

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 results in a negative electrode with high adhesive power, improved durability, and extended battery lifetime by optimizing the amorphous carbon to graphite ratio, ensuring effective charge retention and reduced gas generation during charging.

Implementation Method 1

graphite particles each at least partially covered by an amorphous carbon film... the gas generation in the charging is suppressed

Methodology Applied

Scientific EffectSurface passivation:

Implementation Method 2

hydroxyl groups exist on the surface of the graphite particle... improved durability and extended battery lifetime by optimizing the amorphous carbon to graphite ratio, ensuring effective charge retention

Methodology Applied

Scientific EffectChemical bonding: Chemical Bonding

Data Source

PatentEP3264502B1Negative electrode for lithium ion secondary battery and lithium ion secondary battery

Publication Date: 2020.08.19 ENVISION AESC JAPAN LTD

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Figure 2A~2B
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AI summary

Provided is a negative electrode for a lithium ion secondary battery including: a negative electrode current collector; and a negative electrode active material for a lithium ion secondary battery which is disposed on the negative electrode current collector and contains a carbon material and an aqueous binder. The carbon material is a graphite particle having a covering layer containing amorphous carbon by 5 wt% or less relative to a total weight of the carbon material