Graphite Negative Electrode Composition for Low-Resistance Durability

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Solution Overview

Problem

Existing negative electrodes for nonaqueous electrolyte secondary batteries, particularly those using spherical graphite, face challenges in uniformly covering the inside and edge surfaces of scaly graphites, leading to excessive electrolyte reaction, increased resistance, and reduced durability.

Innovation Solution

A negative electrode configuration using a first negative electrode active substance with scaly graphite surfaces covered by low crystalline carbon and a second negative electrode active substance with controlled graphite interlayer distance, along with a balanced void distribution, to uniformly cover and suppress volume expansion and electrolyte reaction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If spherical graphite is used as negative electrode active substance, then energy density is improved, but uniform coverage of scaly graphite surfaces is insufficient leading to increased resistance

Engineering Contradiction:

Improveenergy densityVSAvoidresistance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent uses a composite structure where scaly graphite particles are embedded in an amorphous carbon matrix. This composite material approach allows the spherical graphite to maintain its high energy density while the amorphous carbon provides uniform coverage and suppression of electrolyte reactions, resolving the resistance issue.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The amorphous carbon acts as an intermediary substance that covers the scaly graphite surfaces. This intermediate layer prevents direct contact between the reactive edge surfaces of scaly graphite and the electrolyte, thereby reducing resistance while maintaining the energy storage capacity of the graphite.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If scaly graphite is compressed to form spherical graphite, then particle expansion is suppressed, but edge surface coverage is insufficient leading to excessive electrolyte reaction

Engineering Contradiction:

Improveparticle expansion suppressionVSAvoidelectrolyte reaction

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The patent applies different properties to different parts of the spherical graphite structure. The interior scaly graphite particles maintain their compressed, expansion-suppressed structure, while the exterior is coated with amorphous carbon that provides uniform edge surface coverage and prevents harmful electrolyte reactions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

By creating a composite where compressed scaly graphite is embedded in amorphous carbon, the patent simultaneously achieves particle expansion suppression (from the compressed graphite structure) and edge surface coverage (from the amorphous carbon matrix), eliminating excessive electrolyte reactions.

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If only spherical graphite is used as negative electrode active substance, then manufacturing is simplified, but initial resistance value becomes higher

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidinitial resistance value

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent creates a composite negative electrode material where spherical graphite particles are embedded in an amorphous carbon matrix. This composite structure maintains manufacturing simplicity while significantly reducing initial resistance values through the uniform surface coverage provided by the amorphous carbon.

Inventive Principle:

Principle #40Composite materials

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 reduces initial resistance and improves durability by uniformly covering scaly graphite surfaces and optimizing void distribution, enhancing ion diffusion and conductivity.

Implementation Method 1

the surface of at least one part is covered with a low crystalline carbon

Methodology Applied

Scientific EffectSurface coverage: Adsorption

Implementation Method 2

A graphite interlayer distance of the above described low crystalline carbon based on electron diffraction images by a transmission electron microscope is equal to or more than 3.8 Å and not more than 5.0 Å

Methodology Applied

Scientific EffectIon diffusion: Diffusion

Data Source

PatentUS12531233B2Negative electrode for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery

Publication Date: 2026.01.20 PRIME PLANET ENERGY & SOLUTIONS INC

AI summary

A negative electrode active substance layer of a negative electrode for nonaqueous electrolyte secondary battery herein disclosed includes at least a first negative electrode active substance and a second negative electrode active substance. The first negative electrode active substance is configured with an aggregated body of a scaly graphite whose surface of at least one part is covered with a low crystalline carbon. A graphite interlayer distance of the low crystalline carbon is equal to or more than 3.8 Å and not more than 5.0 Å. The second negative electrode active substance is a natural graphite or an artificial graphite whose graphite interlayer distance based on electron diffraction images by the transmission electron microscope is equal to or more than 3.35 Å and not more than 3.4 Å. Here, a mass ratio of the first negative electrode active substance and the second negative electrode active substance is 50:50 to 90:10.