Graphite Core Negative Electrode with Metal Particles

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Solution Overview

Problem

Conventional lithium secondary battery negative electrode active materials, such as carbonaceous and metal-graphite composite materials, face issues with irreversible capacitance, rapid degradation, and volume changes during charge/discharge cycles, leading to decreased cycle characteristics and risk of short circuits.

Innovation Solution

A negative electrode active material comprising a graphite core particle with a carbon coating layer and dispersed metal particles, where the carbon coating layer is 1 to 4µm thick, inhibiting volume change and enhancing conductivity, and the graphite core has low porosity to ensure uniform metal dispersion and improved binding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If metal particles (Si, Sn) are used as negative electrode active material to increase capacitance, then battery capacitance is improved, but volume change during charge/discharge causes particle separation and rapid degradation

Engineering Contradiction:

Improvebattery capacitanceVSAvoidcycle characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

Metal particles (Si, Sn) are embedded within graphite core particles, forming a nested structure where the metal is contained inside the graphite matrix. This prevents the metal particles from expanding and contracting freely during lithium insertion/extraction, thereby maintaining structural integrity and improving cycle characteristics while preserving high capacitance.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The invention uses a composite material system combining graphite and metal particles (Si, Sn) in a specific configuration. The graphite provides structural stability and lithium insertion/extraction pathways, while the metal particles provide high capacitance. The composite structure resolves the contradiction between high capacitance and cycle stability.

Inventive Principle:

Principle #40Composite materials

2Reliability

If carbonaceous materials are used as negative electrode active material to replace lithium metals, then safety is improved, but theoretical marginal capacitance is limited to approximately 372 mAh/g

Engineering Contradiction:

ImprovesafetyVSAvoidtheoretical marginal capacitance

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The invention merges the safety advantages of carbonaceous materials with the high capacitance benefits of metal particles. By combining graphite (safe, structurally stable) with metal particles like Si and Sn (high capacitance), the composite achieves both safety and enhanced capacitance beyond the limitations of pure carbonaceous materials.

Inventive Principle:

Principle #5Merging (Combining)

3Quantity of substance

If amorphous carbon is used as negative electrode active material, then capacitance is improved, but irreversibility in charge/discharge cycle increases

Engineering Contradiction:

ImprovecapacitanceVSAvoidcharge/discharge reversibility

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The invention uses crystalline graphite with specific local structural properties (layered structure, intercalation sites) that enable reversible lithium insertion/extraction. This local structural quality of graphite provides both high capacitance and excellent reversibility, overcoming the limitations of amorphous carbon.

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 improved cycle characteristics, increased capacitance, and enhanced charge/discharge efficiency by preventing metal particle separation and maintaining conductivity, thus extending battery lifespan and performance.

Implementation Method 1

the carbon coating layer is coated to a thickness of 1 to 4µm... improved cycle characteristics by inhibiting volume change of a metal particle

Methodology Applied

Scientific EffectVolume change inhibition:

Implementation Method 2

The graphite core particle has a porosity of more than 0 to 0.07 cc/g

Methodology Applied

Scientific EffectPorosity: Porosity

Data Source

PatentEP2192642B1Negative electrode active material, negative electrode having the same and lithium secondary battery

Publication Date: 2017.02.22 SAMSUNG SDI CO LTD

AI summary

Provided is a lithium secondary battery including a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, a separator separating the positive electrode from the negative electrode and an electrolyte. Here, the negative electrode active material includes a graphite core particle, a carbon coating layer coating the graphite core particle, and metal particles dispersed in the carbon coating layer. Thus, the negative electrode active material, the negative electrode having the same, and the lithium secondary battery may provide improved cycle characteristics by inhibiting volume change in metal particles.