Composite Silicon Anode Coating for Low-Expansion Li-Ion Batteries

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Solution Overview

Problem

Lithium-ion batteries using traditional graphite anodes face limitations in energy density, and silicon anode materials suffer from significant volume expansion and poor conductivity, leading to reduced cycling and rate performance.

Innovation Solution

A composite anode material with a novel structure comprising an inner core of silicon nanoparticles and titanium monoxide particles, coated with silicon suboxide and porous carbon fibers, which addresses volume expansion and conductivity issues through synergistic effects, enhancing cycling and rate performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon anode materials are used to increase theoretical specific capacity, then energy density is improved, but volume expansion occurs during lithium intercalation/de-intercalation

Engineering Contradiction:

Improvetheoretical specific capacityVSAvoidvolume expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The patent employs a nested structure where silicon nanoparticles are enclosed within a carbon fiber coating layer, which is further protected by an outer carbon layer. This nested design allows the silicon to expand and contract during lithium intercalation/de-intercalation without causing volume expansion of the overall anode material, as the carbon layers accommodate the dimensional changes.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent uses a flexible carbon fiber coating layer with porous structure that can accommodate the volume changes of silicon during lithium insertion/extraction. The carbon shell acts as a flexible container that expands and contracts with the silicon core, preventing pulverization while maintaining structural integrity throughout cycling.

Inventive Principle:

Principle #30Flexible shells and thin films

2Quantity of substance

If silicon anode materials are used to increase theoretical specific capacity, then energy density is improved, but conductivity deteriorates due to semiconductor properties

Engineering Contradiction:

Improvetheoretical specific capacityVSAvoidconductivity

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent creates a composite material system combining silicon nanoparticles with conductive carbon fibers and carbon coating layers. The carbon components provide excellent electrical conductivity pathways, compensating for the semiconductor nature of silicon, while the silicon core delivers high theoretical specific capacity. This composite structure achieves both high capacity and good conductivity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The carbon fiber coating layer acts as an intermediary between the silicon nanoparticles and the electrolyte, providing a conductive pathway for electron transport. The carbon layer mediates the electrical connection, allowing electrons to move efficiently from the silicon particles to the current collector, thereby improving overall conductivity of the anode material.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If silicon anode materials are used to increase theoretical specific capacity, then energy density is improved, but cycling performance deteriorates due to pulverization and detachment

Engineering Contradiction:

Improvetheoretical specific capacityVSAvoidcycling performance

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The patent applies a carbon fiber coating layer beforehand to cushion and protect the silicon nanoparticles from mechanical stress during lithium intercalation/de-intercalation. This protective layer is applied in advance to prevent pulverization and detachment that would otherwise occur during cycling, thereby maintaining structural integrity and improving cycling performance.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent divides the anode material into segmented silicon nanoparticles rather than using bulk silicon. This segmentation reduces the overall volume expansion effect and minimizes mechanical stress on individual particles during cycling. The nanoscale segmentation allows each particle to undergo volume changes independently without causing aggregate failure, thereby improving cycling stability.

Inventive Principle:

Principle #1Segmentation

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 composite anode material exhibits low volume expansion, excellent cycling stability, and improved conductivity, effectively utilizing the high theoretical capacity of silicon, resulting in higher discharge capacity and energy density.

Implementation Method 1

provide channels for lithium ion intercalation/de-intercalation

Methodology Applied

Scientific EffectIntercalation:

Implementation Method 2

sintering the pre-sintered fiber membrane at 800-1200°C for a sintering time in an inert atmosphere in plasma equipment

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentUS20240429376A1Composite anode material and preparation method thereof, anode sheet, battery and powered device

Publication Date: 2024.12.26 BYD CO LTD

AI summary

An anode material includes an inner core, a first coating layer coated on a surface of the inner core, and a second coating layer coated on a surface of the first coating layer. The inner core includes silicon nanoparticles and titanium monoxide particles, the first coating layer includes silicon suboxide, and the second coating layer includes carbon fibers with a porous structure.