Sulfur-Carbon Cathode Coating for Conductivity and Polysulfide Control

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Solution Overview

Problem

Lithium-sulfur batteries face limitations in capacity and efficiency due to low lithium ion conductivity and polysulfide dissolution, leading to reduced discharging capacity and stability issues.

Innovation Solution

A positive electrode active material with a sulfur-carbon composite coated with a carbon nanostructure and iron oxyhydroxynitrate is developed, enhancing electrical conductivity and adsorbing lithium polysulfide to improve battery performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If sulfur is used as positive electrode active material to achieve high capacity, then theoretical energy density increases to 2,600 Wh/kg, but electrical conductivity decreases to about 5.0×10−14 S/cm causing electrochemical reaction difficulty

Engineering Contradiction:

Improvetheoretical energy densityVSAvoidelectrical conductivity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent uses sulfur-carbon composite materials where sulfur provides high theoretical energy density (2,600 Wh/kg) while carbon matrix provides electrical conductivity. The composite structure allows sulfur particles to be dispersed in conductive carbon, solving the contradiction between high capacity and poor conductivity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Conductive carbon materials act as an intermediary between sulfur particles, providing electron transport pathways. The carbon mediator enables electrochemical reactions to proceed efficiently while sulfur maintains its high capacity characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If sulfur content is increased to improve battery capacity, then energy density increases, but polysulfide dissolution into electrolyte increases causing capacity loss and voltage decay

Engineering Contradiction:

Improvesulfur contentVSAvoidcapacity retention

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent converts the harmful polysulfide dissolution into a beneficial effect by using polysulfide-absorbing materials. These materials intentionally capture dissolved polysulfides, preventing them from causing capacity loss and voltage decay, thus turning the harmful dissolution phenomenon into a controlled process that maintains battery performance.

Inventive Principle:

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

Solution Approach 2:

Porous carbon structures and polysulfide-absorbing materials with controlled porosity are used to physically confine polysulfides. The porous structure provides large surface area for polysulfide adsorption while maintaining ion transport, preventing polysulfide dissolution into the bulk electrolyte.

Inventive Principle:

Principle #31Porous materials

3Reliability

If conventional carbon coating is applied to improve electrical conductivity, then conductivity increases slightly, but substantial performance improvement is not achieved due to insufficient conductivity enhancement

Engineering Contradiction:

Improveelectrical conductivityVSAvoiddischarging capacity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent changes the parameters of the conductive material from conventional carbon black to advanced carbon nanomaterials with superior conductivity. By changing the type, structure, and distribution of carbon materials, the patent achieves substantial conductivity enhancement rather than marginal improvement.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent transitions from zero-dimensional carbon black particles to one-dimensional carbon nanotubes and two-dimensional graphene structures. This dimensional change provides continuous conductive networks and larger surface areas, dramatically improving electrical conductivity and discharging capacity.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 the discharging capacity and stability of lithium-sulfur batteries by improving electrical conductivity and reducing polysulfide-related degradation, leading to enhanced charging/discharging efficiency and extended battery life.

Implementation Method 1

enhancing electrical conductivity

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

adsorbing lithium polysulfide

Methodology Applied

Scientific EffectAdsorption: Adsorption

Data Source

PatentUS11837731B2Cathode active material for lithium secondary battery

Publication Date: 2023.12.05 LG ENERGY SOLUTION LTD

AI summary

A positive electrode active material for a lithium secondary battery, including a sulfur-carbon composite and a coating layer located on a surface of the sulfur-carbon composite and including a carbon nanostructure and iron oxyhydroxynitrate.