Silicon Anode Layer Structure for Low-Resistance Li-Ion Cycling

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Solution Overview

Problem

Silicon-based negative electrode active materials in lithium secondary batteries experience increased resistance and volume contraction/expansion issues during charging and discharging, leading to short circuits and reduced battery lifespan due to side reactions with the electrolyte.

Innovation Solution

A negative electrode structure is developed with a carbon-coated silicon-based active material in the first layer and a metal-doped silicon-based active material in the second layer, both with controlled particle sizes and compositions to minimize side reactions and expansion, including a conductive agent like SWCNT or MWCNT to enhance conductivity and prevent peeling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based active material is used to increase capacity, then energy density is improved, but resistance increases due to side reactions with electrolyte

Engineering Contradiction:

ImprovecapacityVSAvoidresistance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A carbon coating layer is applied as an intermediary between the silicon-based active material and the electrolyte. This carbon layer prevents direct contact and side reactions between silicon and electrolyte, thereby reducing resistance increase while preserving the high capacity benefits of silicon-based materials.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The negative electrode uses a composite structure combining silicon-based active material with carbon material. This composite approach leverages the high capacity of silicon while utilizing carbon's chemical stability and conductivity to mitigate side reactions and resistance issues.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If silicon-based active material is used to increase capacity, then energy density is improved, but volume contraction and expansion cause short circuits and cracks

Engineering Contradiction:

ImprovecapacityVSAvoidstructural integrity

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A carbon coating shell is formed around the silicon-based active material particles. This flexible carbon shell accommodates the volume contraction and expansion of silicon during charge-discharge cycles, preventing structural failure, cracks, and short circuits while maintaining particle integrity.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The carbon coating is applied beforehand to the silicon-based active material, creating a protective buffer layer that cushions against the mechanical stress of volume changes during cycling, preventing premature failure of the active material structure.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If carbon coating is applied to suppress side reactions, then resistance increase is suppressed, but manufacturing complexity increases

Engineering Contradiction:

ImproveresistanceVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The carbon coating process parameters (coating thickness, carbon source, treatment conditions) are optimized to achieve effective protection with minimal processing steps. This balances the need for resistance suppression with manufacturing simplicity, making the process industrially viable.

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

This configuration improves the room temperature and high-temperature lifespan characteristics and rapid charging performance of lithium secondary batteries by suppressing side reactions and contraction/expansion, resulting in enhanced capacity retention rates.

Implementation Method 1

silicon-based active materials, such as silicon oxide, increase resistance due to side reactions with electrolyte

Methodology Applied

Scientific EffectCarbon coating protection: Coatings

Implementation Method 2

a second negative electrode mixture layer including a second silicon-based negative electrode active material on the first negative electrode mixture layer, wherein the second silicon-based negative electrode active material is SiOx

Methodology Applied

Scientific EffectMetal doping: Dopants

Implementation Method 3

including a conductive agent like SWCNT or MWCNT to enhance conductivity and prevent peeling

Methodology Applied

Scientific EffectCarbon nanotube conduction: Carbon Nanotubes

Data Source

PatentEP4439687A1Negative electrode for lithium secondary battery and lithium secondary battery comprising the same

Publication Date: 2024.10.02 SK ON CO LTD

Figure 1

AI summary

A negative electrode for a lithium secondary battery and a lithium secondary battery including the same are disclosed. In some implementations, the negative electrode for a secondary battery includes a negative electrode current collector, a first negative electrode mixture layer including a first silicon-based negative electrode active material on at least one surface of the negative electrode current collector, and a second negative electrode mixture layer including a second silicon-based negative electrode active material on the first negative electrode mixture layer, wherein the second silicon-based negative electrode active material is SiOx (0≤x<2) doped with a metal element.