High Loading Sulfur Cathode Slurry via Encapsulation

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Solution Overview

Problem

Sulfur-based cathodes in batteries face challenges due to low conductivity and polysulfide diffusion, leading to reduced cycle life and energy density, which are not adequately addressed by existing solutions that compromise sulfur's high charge capacity.

Innovation Solution

A high-density slurry comprising encapsulated chalcogen particles, carbon nanofibers, carbon black, carboxymethyl cellulose, styrene butadiene rubber, and water, with a sulfur content greater than 85 wt%, and a specific ratio of carbon nanofibers to carbon black, enhancing conductivity and sulfur loading while controlling polysulfide diffusion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high loading of conductive additives is used to improve the electronic conductivity of sulfur, then the overall electronic conductivity is improved, but the sulfur content in the cathode decreases

Engineering Contradiction:

Improveelectronic conductivityVSAvoidsulfur content

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent encapsulates sulfur particles within conductive carbon matrix structures, creating a nested configuration where sulfur is contained inside conductive hosts. This allows the sulfur to be surrounded by conductive material without requiring high loadings of external conductive additives, thereby maintaining high sulfur content while achieving improved electronic conductivity.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent creates composite structures by combining sulfur with conductive carbon materials (such as carbon nanotubes, graphene, or conductive polymers) to form a composite cathode material. This composite approach provides both the high capacity of sulfur and the electrical conductivity of carbon materials, eliminating the need for high loadings of separate conductive additives.

Inventive Principle:

Principle #40Composite materials

2Reliability

If sulfur is infused into micro/nano carbon hosts to enhance conductivity, then the electronic conductivity is improved, but polysulfide diffusion is not adequately controlled

Engineering Contradiction:

Improveelectronic conductivityVSAvoidpolysulfide diffusion

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent applies different functional characteristics to different regions of the cathode structure. The inner region contains encapsulated sulfur with high conductivity, while the outer region incorporates polysulfide-blocking layers or intermediates that specifically address polysulfide diffusion. This local differentiation allows simultaneous optimization of conductivity and polysulfide control.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces intermediary layers or materials between the sulfur and the external environment, such as coating layers or intermediate compounds, that specifically interact with polysulfides to prevent their diffusion while allowing ionic transport. These intermediaries act as barriers that control polysulfide movement without compromising the electrical conductivity of the sulfur cathode.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If sulfur is reduced to improve charge capacity, then polysulfide intermediates are formed, but mass loss occurs due to solubility in electrolyte

Engineering Contradiction:

Improvecharge capacityVSAvoidmass loss

Core Design Contradiction:

Quantity of substanceVSLoss of substance

Solution Approach 1:

The patent converts the harmful effect of polysulfide formation into a beneficial outcome by designing the cathode structure to contain and utilize polysulfides. The encapsulated sulfur and blocking layers prevent polysulfide dissolution, allowing the polysulfide intermediates to remain within the cathode structure and participate in reversible reactions, thereby maintaining charge capacity while preventing mass loss.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 solution significantly increases sulfur loading and conductivity, resulting in improved cycle life and energy density, making sulfur-based batteries competitive with commercial lithium-ion batteries for electric vehicles and energy storage applications.

Implementation Method 1

the need for high loadings of conductive additives to improve the overall electronic conductivity

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

control the diffusion of polysulfide intermediates formed during cycling

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Implementation Method 3

high density slurries comprising encapsulated sulfur and/or chalogen particles, carbon nanofibers and activated carbon black

Methodology Applied

Scientific EffectComposite materials: Composite Materials

Data Source

PatentUS10312500B2Formation of slurry for high loading sulfur cathodes

Publication Date: 2019.06.04 TOYOTA JIDOSHA KK

AI summary

A high density slurry comprising encapsulated sulfur particles, carbon nanofibers and activated carbon black suitable for use in forming the active material of an electrode. A method for forming the high density sulfur slurry is also provided. A cathode containing the particles and a battery constructed with the cathode as well as methods for their formation are also provided.