Lithium-Ion Battery Negative Electrode Material with Carbon-Coated Alloy Particles

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Solution Overview

Problem

Existing lithium ion secondary battery negative electrode materials face challenges such as high manufacturing costs due to the need for heat treatment in a vacuum or inert atmosphere, significant capacity reduction during charge and discharge cycles, and inefficiencies in electron conduction paths due to volume changes of alloy-based materials.

Innovation Solution

A negative electrode material with lithium-occluding alloy particles coated in carbon and bonded to carbon fibers via an adhesive resin, which maintains electron conduction paths during volume changes without requiring heat treatment in a vacuum or inert atmosphere.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If alloy based material is used as negative electrode active material to increase charged capacity, then lithium occlusion amount increases, but volume changes during charge and discharge cause particle disconnection and large capacity reduction

Engineering Contradiction:

Improvelithium occlusion amountVSAvoidcapacity retention during charge and discharge cycles

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A carbon coating film is applied on the surface of alloy-based particles to provide flexibility and accommodate volume changes during lithium insertion/extraction. This thin film shell prevents particle disconnection while allowing the underlying alloy material to expand and contract, thereby maintaining electron conduction paths and capacity retention.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The negative electrode uses a composite structure combining alloy-based particles (for high lithium occlusion) with carbon-coated graphite particles (for structural stability and electron conduction). This composite material approach allows the alloy to provide high capacity while the carbon matrix maintains structural integrity and electrical connectivity during cycling.

Inventive Principle:

Principle #40Composite materials

2Reliability

If polyimide resin is used as negative electrode binder to suppress capacity degradation, then adhesiveness to silicon improves, but heat treatment in vacuum or inert atmosphere is required increasing manufacturing cost

Engineering Contradiction:

Improvecharge and discharge cycle characteristicsVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent extracts the heat treatment step from the manufacturing process by using alternative binder materials (such as polyvinylidene fluoride or carboxymethyl cellulose) that do not require thermal curing. This removes the expensive vacuum or inert atmosphere requirement while still achieving adequate adhesion between the negative electrode active material and current collector.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention employs conventional, low-cost binder materials that can be applied at room temperature or with simple drying, replacing the expensive polyimide resin system. These simpler binders achieve sufficient performance without requiring complex heat treatment infrastructure, thereby reducing manufacturing costs.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If carbon fiber is added to maintain electron conduction path during volume changes, then capacity reduction is suppressed, but manufacturing complexity increases

Engineering Contradiction:

Improveelectron conduction path stabilityVSAvoidnegative electrode structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the electron conduction function with the existing carbon coating on alloy particles and the graphite matrix structure. Instead of adding separate carbon fibers, the conductive network is formed by the inherent carbon materials already present in the composite structure, eliminating the need for additional components while maintaining electron conduction during volume changes.

Inventive Principle:

Principle #5Merging (Combining)

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 enhances the initial capacity and reduces capacity loss in charge and discharge cycles, eliminating the need for costly heat treatments and maintaining efficient electron conduction.

Implementation Method 1

a particle of a negative electrode active material which occludes and releases lithium ions and a carbon fiber, wherein the negative electrode active material occludes lithium by forming an alloy with the lithium

Methodology Applied

Scientific EffectAlloy formation: Chemical Bonding

Implementation Method 2

the carbon fiber is bonded to the surface of the carbon via an adhesive resin

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS9997771B2Negative electrode material for lithium ion secondary battery and manufacturing method of the same, negative electrode for lithium ion secondary battery and manufacturing method of the same, and lithium ion secondary battery

Publication Date: 2018.06.12 HITACHI LTD

AI summary

To provide a negative electrode material having a high initial capacity and a long charge and discharge cycle life A negative electrode material according to the present invention contains a particle of a negative electrode active material that occludes and releases lithium ions and a carbon fiber, wherein the negative electrode active material occludes lithium by forming an alloy with the lithium, a surface of the negative electrode active material particle is coated with carbon, and the carbon fiber is bonded to the surface of the carbon via an adhesive resin.