Silicon-Coated Carbon Anode Particles for Lithium-Ion Batteries

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Solution Overview

Problem

Lithium ion batteries face limitations due to the low electrochemical capacity and mechanical instability of graphitic carbon anode materials, which result in significant volume expansion and irreversible capacity loss during cycling, hindering the utilization of high theoretical specific capacities of alternative materials like silicon.

Innovation Solution

Coating electrically conductive carbon particles with elemental silicon using chemical vapor deposition in an oxygen-free gas atmosphere, ensuring uniform coating and increased mechanical stability, thereby enhancing the anode material's performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If graphitic carbon is used as anode material, then mechanical stability and cycling properties are improved, but electrochemical capacity is limited to 372 mAh/g

Engineering Contradiction:

Improvecycling propertiesVSAvoidelectrochemical capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent uses composite carbon particles consisting of a graphite core surrounded by a coating layer containing crystalline and/or amorphous carbon. This composite structure combines the mechanical stability of graphite with the high capacity potential of alternative materials, achieving both reliability and increased capacity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The coating layer is applied locally around the graphite core to provide different functional properties in different regions. The core maintains structural stability while the coating enables higher lithium insertion capacity, creating local quality differentiation that resolves the capacity limitation.

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If alternative materials like silicon are used to increase electrochemical capacity, then specific capacity increases to 4400 mAh/g, but volume expansion up to 323% causes mechanical stress and particle disintegration

Engineering Contradiction:

Improvespecific capacityVSAvoidmechanical stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The coating layer is applied beforehand to cushion and absorb the mechanical stress generated during lithium insertion and extraction. This pre-applied protective layer prevents particle disintegration before it occurs, allowing high-capacity materials like silicon to be used without suffering from their inherent volume expansion problems.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The coating layer acts as a flexible shell that can accommodate volume changes during cycling. This thin film structure provides mechanical flexibility to handle the 323% volume expansion of silicon while maintaining particle integrity and electrical contact.

Inventive Principle:

Principle #30Flexible shells and thin films

3Quantity of substance

If alloy anode materials are used, then electrochemical capacity increases to 994 mAh/g for tin, but volume expansion above 200% occurs during cycling

Engineering Contradiction:

Improveelectrochemical capacityVSAvoidvolume expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The patent changes the physical and chemical parameters of the carbon particles by applying a coating layer that modifies the volume expansion behavior. The coating constrains and distributes the volume changes, transforming the extreme parameter change of 200-300% expansion into manageable local deformations that maintain overall particle stability.

Inventive Principle:

Principle #35Parameter changes

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 coated carbon particles with silicon exhibit improved mechanical stability and reduced irreversible capacity loss, allowing for increased cycle life and higher specific capacity utilization, leading to enhanced energy density and extended operating times for lithium ion batteries.

Implementation Method 1

coating electrically conductive carbon particles with elemental silicon using chemical vapor deposition

Methodology Applied

Scientific EffectChemical vapor deposition: Chemical Vapour Deposition

Data Source

PatentUS8673502B2Method for producing coated carbon particles and use of the latter in anode materials for lithium-ion batteries

Publication Date: 2014.03.18 NEXEON LTD

AI summary

The invention relates to a process for producing coated carbon particles, which comprises coating electrically conductive carbon particles with elemental doped or undoped silicon by chemical vapor deposition from at least one gaseous silane in an oxygen-free gas atmosphere in a reaction space, with the electrically conductive carbon particles being in continual motion during the vapor deposition, and also correspondingly coated carbon particles and their use in anode materials for lithium ion batteries.