Lithium-Sulfur Battery Cathode Catalyst for Polysulfide Control

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Solution Overview

Problem

Lithium-sulfur secondary batteries face challenges with the low electrical conductivity of sulfur and lithium sulfide, leading to inhibited electron transfer and reduced battery performance due to the leaching of poly sulfides, making it difficult to commercialize and maintain high energy density.

Innovation Solution

A lithium secondary battery with a positive electrode catalyst comprising a transition metal composite bonded to porous carbon, where the transition metal is bonded to four nitrogen atoms, enhancing the kinetic of sulfur reduction and improving the battery's performance and lifetime.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If sulfur is used as a positive electrode active material to achieve high energy density, then theoretical energy density increases to 2,800 Wh/kg, but electrical conductivity decreases making electron transfer difficult

Engineering Contradiction:

Improveenergy densityVSAvoidelectrical conductivity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

A transition metal composite catalyst is introduced as an intermediary substance between sulfur and the electrode. This catalyst mediates the electrochemical reactions, facilitating electron transfer and improving electrical conductivity without compromising the high energy density provided by sulfur. The catalyst acts as a bridge that enables efficient charge transfer while maintaining the sulfur-based active material's energy storage capacity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs composite materials by combining sulfur with transition metal composites (such as Fe, Co, Ni, Cu, or Zn-based catalysts) to create a positive electrode with enhanced properties. This composite structure integrates the high energy density advantage of sulfur with the improved electrical conductivity and catalytic activity of transition metals, resolving the contradiction between energy density and conductivity.

Inventive Principle:

Principle #40Composite materials

2Productivity

If platinum is used as an electrochemical catalyst to improve the kinetic of redox reaction, then reaction kinetics improve, but cost increases and catalyst poisoning occurs

Engineering Contradiction:

Improvereaction kineticsVSAvoidcost and commercialization

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent replaces expensive platinum catalysts with cheaper transition metal composites (Fe, Co, Ni, Cu, or Zn-based catalysts). These alternative catalysts provide sufficient catalytic activity for the redox reactions at a fraction of the cost of platinum, making the battery commercially viable. The transition metal composites maintain acceptable reaction kinetics while dramatically reducing material costs.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention changes the chemical composition parameter of the catalyst from precious metals (platinum) to transition metals with different electronic structures and catalytic properties. This parameter change maintains or improves reaction kinetics while reducing cost and eliminating catalyst poisoning issues associated with platinum in sulfur-based systems.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If sulfur is used as positive electrode material to achieve high capacity, then theoretical capacity reaches 1,675 mAh/g, but poly sulfide leaching occurs during charging/discharging

Engineering Contradiction:

ImprovecapacityVSAvoidlifetime characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The transition metal composite catalyst converts the harmful poly sulfide leaching phenomenon into a beneficial process. The catalyst promotes the conversion of soluble poly sulfides into insoluble lithium sulfide products, effectively trapping the poly sulfides that would otherwise leach and cause degradation. This transforms the leaching issue into a mechanism that enhances both capacity utilization and battery lifetime.

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 transition metal composite catalyst improves the initial discharging capacity and lifetime characteristics of the battery by enhancing the reaction rate of sulfur reduction, making it suitable for commercialization and reducing the reliance on expensive platinum catalysts.

Implementation Method 1

a positive electrode catalyst that may facilitate the commercialization and high performance of the battery by promoting a chemical reaction occurring in the electrode

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

achieve high energy capacity and rechargeability from electrochemical cleavage (reduction) and reforming (oxidation) of sulfur-sulfur bonds

Methodology Applied

Scientific EffectElectrochemical reaction: Redox Reactions

Data Source

PatentUS11876227B2Lithium secondary battery

Publication Date: 2024.01.16 LG ENERGY SOLUTION LTD

AI summary

A lithium secondary battery is provided and, more specifically, a lithium secondary battery comprising a cathode catalyst including a transition metal composite having a stable structure in which four nitrogens are bonded to the transition metal as a cathode catalyst for a reduction reaction of sulfur generated during operation of the lithium secondary battery having a sulfur-containing material included in a cathode thereof, thereby improving performance and longevity of the battery.