Yolk-Shell Nanoparticle for Lithium-Sulfur Battery Expansion

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Solution Overview

Problem

Lithium-sulfur batteries face limitations due to low sulfur conductivity, polysulfide dissolution, and volumetric expansion during discharge, which hinder their practical application despite their high energy capacity and low fabrication cost.

Innovation Solution

A yolk-shell nanoparticle structure is developed, featuring a decomposable sulfur material yoke and a permeable organic polymer shell with a void space, allowing for sulfur expansion and minimizing polysulfide dissolution, enhancing battery performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If sulfur is used as cathode material in lithium-sulfur batteries, then high theoretical energy capacity is achieved, but volumetric expansion during discharge occurs

Engineering Contradiction:

Improveenergy capacityVSAvoidvolumetric expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The patent employs a core-shell nanoparticle structure where sulfur is encapsulated within a protective shell. The core contains the sulfur cathode material while the shell provides structural containment, allowing the battery to achieve high energy capacity from the sulfur while preventing the volumetric expansion from damaging the electrode structure.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent utilizes a flexible polymer shell surrounding the sulfur core. This shell can accommodate the volumetric expansion of sulfur during discharge through its elastic properties, preventing structural collapse while maintaining the integrity of the electrode. The thin film structure allows lithium ion transport while providing mechanical protection.

Inventive Principle:

Principle #30Flexible shells and thin films

2Quantity of substance

If sulfur is used as cathode material, then high energy capacity is achieved, but polysulfide dissolution and shuttling effect occur

Engineering Contradiction:

Improveenergy capacityVSAvoidpolysulfide dissolution

Core Design Contradiction:

Quantity of substanceVSLoss of substance

Solution Approach 1:

The patent extracts the harmful polysulfides from the electrolyte by confining them within the nanoparticle shell. The shell acts as a barrier that prevents polysulfide dissolution into the bulk electrolyte, thereby eliminating the shuttling effect while retaining the high capacity benefits of sulfur.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a polymer shell as an intermediary layer between the sulfur core and the electrolyte. This shell mediates the interaction by allowing lithium ion transport while blocking polysulfide dissolution, thus resolving the contradiction between achieving high capacity and preventing polysulfide loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If sulfur is used as cathode material, then low fabrication cost is achieved, but low conductivity of sulfur occurs

Engineering Contradiction:

Improvefabrication costVSAvoidconductivity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent creates a composite nanoparticle structure combining sulfur with conductive materials in the shell. This composite structure maintains the low cost advantage of sulfur while improving electrical conductivity through the conductive components, enabling both economical fabrication and reliable battery performance.

Inventive Principle:

Principle #40Composite materials

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 yolk-shell structure improves cycling stability and capacity retention in lithium-sulfur batteries by accommodating volumetric expansion and reducing polysulfide loss, achieving stable capacities at 765 mAh g−1 at 0.2 C and 628 mAh g−1 at 0.5 C after 200 cycles.

Implementation Method 1

a permeable organic polymer material shell surrounding the decomposable material yoke

Methodology Applied

Scientific EffectPermeation: Permeation

Implementation Method 2

a decomposable material yoke (i.e., a sulfur material which is thermally decomposable to form a sulfur material vapor)

Methodology Applied

Scientific EffectThermal decomposition: Pyrolysis

Implementation Method 3

The void space accommodates materials expansion (i.e., generally but not limited to cathodic materials) when operating the battery

Methodology Applied

Scientific EffectVolumetric expansion: Thermal Expansion

Data Source

PatentUS11437615B2Yolk-shell nanoparticle, method and applications

Publication Date: 2022.09.06 CORNELL UNIVERSITY

AI summary

A nanoparticle and a method for fabricating the nanoparticle utilize a decomposable material yoke located within permeable organic polymer material shell and separated from the permeable organic polymer material shell by a void space. When the decomposable material yoke comprises a sulfur material and the permeable organic polymer material shell comprises a material permeable to both a sulfur material vapor and a lithium ion within a battery electrolyte the nanoparticle may be used within an electrode for a Li/S battery absent the negative effects of battery electrode materials expansion.