Sulfur-Carbon Composite with Acid-Modified Surface for Lithium-Sulfur Batteries

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Solution Overview

Problem

Lithium-sulfur batteries face challenges with lithium polysulfide elution, leading to active material loss and reduced capacity and lifespan, due to the nonconductive nature of sulfur and the complexity and high cost of existing methods to address this issue.

Innovation Solution

A sulfur-carbon composite is created by modifying a carbon-based material with a hydroxyl group and carboxyl group using a mixed solution of nitric acid and sulfuric acid, which effectively adsorbs polysulfides, enhancing electrical conductivity and preventing elution, thus improving battery capacity and lifespan without the need for additional additives.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If sulfur is used as a positive electrode active material to achieve high energy density, then the battery capacity is improved, but lithium polysulfide elution occurs causing active material loss and reduced battery lifespan

Engineering Contradiction:

Improvebattery capacityVSAvoidbattery lifespan

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A carbon-based material serves as an intermediary between sulfur and the electrolyte, providing a conductive framework that hosts sulfur while preventing direct contact between lithium polysulfide and the electrolyte, thus suppressing elution while maintaining high capacity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention uses a composite structure combining sulfur with a carbon-based material, where the carbon component provides electrical conductivity and structural support, while sulfur provides high capacity, creating a synergistic material that resolves both capacity and stability issues

Inventive Principle:

Principle #40Composite materials

2Reliability

If carbon-based material is used to improve electrical conductivity, then electron migration is facilitated, but the material becomes more expensive and complex to process

Engineering Contradiction:

Improveelectrical conductivityVSAvoidprocessing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention uses a homogeneous carbon-based material (such as carbon black or graphite) that can be easily mixed with sulfur, avoiding complex composite structures while providing uniform electrical conductivity throughout the positive electrode

Inventive Principle:

Principle #33Homogeneity

Solution Approach 2:

The invention optimizes parameters such as the carbon-to-sulfur ratio, particle size distribution, and mixing method to achieve effective conductivity enhancement through simple mixing processes, avoiding complex fabrication steps

Inventive Principle:

Principle #35Parameter changes

3Reliability

If transition metal chalcogenides are used as additives to adsorb sulfur, then polysulfide elution is suppressed, but the additive cost increases and positive electrode weight increases

Engineering Contradiction:

Improvepolysulfide elution suppressionVSAvoidpositive electrode weight

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The invention replaces expensive transition metal chalcogenides with inexpensive carbon-based materials that, while less inherently adsorptive, provide sufficient polysulfide suppression through their conductive network and surface properties, significantly reducing material cost

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The carbon-based material performs multiple functions simultaneously: providing electrical conductivity, hosting sulfur, and suppressing polysulfide elution, eliminating the need for separate expensive additives and reducing overall electrode weight

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 sulfur-carbon composite effectively suppresses polysulfide elution, enhancing the battery's capacity retention and lifespan by using a simple and cost-effective process to modify the carbon-based material, ensuring high electrical conductivity and polysulfide adsorption.

Implementation Method 1

a sulfur-carbon composite including a carbon-based material of which surface is modified with a hydroxyl group and a carboxyl group, and sulfur

Methodology Applied

Scientific EffectAdsorption: Adsorption

Data Source

PatentUS11239465B2Sulfur-carbon composite, preparation method therefor, and lithium-sulfur battery comprising same

Publication Date: 2022.02.01 LG ENERGY SOLUTION LTD

AI summary

A sulfur-carbon composite including a carbon-based material of which surface is modified by acid treatment is provided, as well as a method for preparing the same, and a lithium-sulfur battery including the same. A sulfur-carbon composite suppresses polysulfide elution when used as a positive electrode active material of a lithium-sulfur battery by including a carbon-based material of which surface is modified to have a hydroxyl group and a carboxyl group capable of adsorbing polysulfide on the surface. Accordingly, capacity property and life time property of the battery may be enhanced. In addition, a surface of the carbon-based material can be modified using a simple process of treating with a mixed solution of nitric acid and sulfuric acid, and a content of functional groups on the surface can be controlled depending on a mixing ratio of the nitric acid and the sulfuric acid.