Graphite Anode Inner Channels for Fast Lithium Charging

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Solution Overview

Problem

Current lithium-ion battery anode materials lack fast charging capability, long cyclability, high capacity, and high coulombic efficiency, making them unsuitable for large-scale applications such as electric vehicles.

Innovation Solution

A carbon anode material with interconnected inner channels and surface pores is developed by heating spherical graphite or graphite-carbon composite particles in specific temperature-controlled atmospheres to create a structure that enhances lithium ion intercalation and diffusion, thereby improving rate capability and cyclability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If graphite is used as anode material, then cost is low and capacity is high, but lithiation rate capability is limited

Engineering Contradiction:

Improvelithiation rate capabilityVSAvoidinterlayer space structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent introduces a porous structure within graphite particles by creating inner channels and surface pores. This porous architecture allows lithium ions to access multiple pathways for intercalation, significantly improving the lithiation rate capability while maintaining the low cost and high capacity advantages of graphite material

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The graphite particle is segmented into multiple functional regions including surface pores, inner channels, and bulk graphite regions. This segmentation creates a hierarchical structure where lithium ions can intercalate at surface pores and diffuse through inner channels to reach bulk regions, enhancing overall charge acceptance rate

Inventive Principle:

Principle #1Segmentation

2Productivity

If soft carbon is used, then lithium input rate is fast, but capacity is limited and average potential is high

Engineering Contradiction:

Improvelithium input rateVSAvoidcapacity

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The patent creates a composite structure combining amorphous carbon (soft carbon) with crystalline graphite. The amorphous carbon phase provides fast lithium input rate characteristics, while the graphite phase contributes high capacity. The composite leverages the advantages of both materials to achieve both fast charging and high capacity

Inventive Principle:

Principle #40Composite materials

3Quantity of substance

If hard carbon is used, then capacity is around 400 mAh/g, but density is low and coulombic efficiency is low

Engineering Contradiction:

ImprovecapacityVSAvoiddensity

Core Design Contradiction:

Quantity of substanceVSVolume of stationary object

Solution Approach 1:

The patent applies local quality by creating regions of different carbon structures within the particle. The surface and inner channel regions have amorphous carbon characteristics that facilitate fast lithium uptake, while the bulk regions maintain crystalline graphite structure that provides high density and high coulombic efficiency

Inventive Principle:

Principle #3Local quality

4Productivity

If macropores are introduced in graphite, then charge-discharge rate is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvecharge-discharge rateVSAvoidmanufacturing process

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent employs preliminary action by using a template-directed approach where a mold is prepared first, then carbon is deposited around it. After carbonization, the mold is removed to leave behind the desired macroporous structure. This preliminary template preparation simplifies the overall manufacturing process compared to direct pore creation methods

Inventive Principle:

Principle #10Preliminary action

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 resulting anode material exhibits excellent capacity, rate capability, and cyclability, making it suitable for high-energy density lithium-ion batteries.

Implementation Method 1

first heating the spherical raw carbon particle at a temperature of 500 to 800° C. with a temperature rising rate of 15 to 30° C./min in an oxygen-containing atmosphere

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

second heating the particle after the first heating by rising the temperature up to 900 to 1200° C. with a temperature rising rate of 1 to 10° C./min in an inert atmosphere

Methodology Applied

Scientific EffectGraphitization:

Implementation Method 3

the small interlayer spaces (0.335 nm), the lack of Li-ion intercalation sites on the natural graphite basal plane

Methodology Applied

Scientific EffectIntercalation:

Implementation Method 4

the long diffusion range among the graphite interlayers result in a limited lithiation rate capability

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS11171335B2Fast chargeable carbon anode material with inner channels

Publication Date: 2021.11.09 NEC CORP

AI summary

To provide an anode material for implementing a lithium-ion battery that is capable of high-speed charging and excellent in cycle characteristics, and has high capacity. The anode material includes a spherical particle of graphite or graphite-carbon composite provided with pores on the surface and inner channels in the core part of the particle, the inner channels being interconnected to the pores.