Sulfur-Based Cathode Material with Metallic Sulfide Particles
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Solution Overview
Problem
Lithium-ion secondary batteries using elemental sulfur as a positive-electrode active material suffer from deteriorated battery capacity due to sulfur compounds dissolving in the electrolyte, leading to reduced charging and discharging capacity over repeated cycles, and existing sulfur-based materials do not adequately improve cyclability.
Innovation Solution
A process involving the heat-treatment of a starting material comprising a polymer, sulfur, and an organometallic compound dispersed as fine particles under a non-oxidizing atmosphere, resulting in metallic sulfide particles with specific particle sizes dispersed in the material, enhancing the charging and discharging capacity and cyclability of lithium-ion secondary batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If elemental sulfur is used as a positive-electrode active material, then charging and discharging capacity is significantly increased, but battery capacity deteriorates through repeated charging and discharging due to sulfur compound elution into the electrolyte
Solution Approach 1:
Metallic sulfide particles are introduced as an intermediary substance between sulfur and the electrolyte. These particles act as a mediator that prevents direct contact and reaction between sulfur compounds and the electrolyte, thereby preventing elution while maintaining the high capacity benefits of sulfur-based materials
Solution Approach 2:
The invention creates a composite material system consisting of sulfur-based positive-electrode active material combined with metallic sulfide particles. This composite structure integrates the high capacity advantage of sulfur with the protective function of metallic sulfide, achieving both high capacity and improved cyclability
2Quantity of substance
If sulfur-based positive-electrode active material is used to increase capacity, then charging and discharging capacity is enhanced, but sulfur compounds elute into the electrolyte causing capacity reduction over cycles
Solution Approach 1:
Metallic sulfide particles serve as an intermediary barrier that physically blocks sulfur compounds from eluting into the electrolyte. This intermediary layer allows the sulfur-based material to maintain its high capacity function while preventing the harmful elution effect
Solution Approach 2:
The invention converts the potentially harmful sulfur compounds into beneficial metallic sulfide particles through controlled reaction. Instead of allowing harmful elution, the sulfur compounds are transformed into stable metallic sulfide that provides protective functionality while maintaining electrochemical activity
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 approach significantly improves the cyclability and charging and discharging capacity of lithium-ion secondary batteries by preventing sulfur compound elution into the electrolyte, maintaining a high capacity retention rate over multiple cycles.
Implementation Method 1
particles of metallic sulfide resulting from sulfurization of the organometallic compound
Implementation Method 2
heat-treating a starting material comprising a polymer, sulfur, and an organometallic compound dispersed in a form of fine particles
Data Source
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AI summary
An object of the present invention is to provide a novel sulfur-based positive electrode active material for a lithium-ion secondary battery which is excellent in cyclability and can largely improve a charging and discharging capacity, a positive electrode comprising the positive electrode active material and a lithium-ion secondary battery made using the positive electrode. The sulfur-based positive electrode active material is obtainable by subjecting a starting material comprising a polymer, sulfur and an organometallic compound dispersed in a form of fine particles to heat-treatment under a non-oxidizing atmosphere, wherein the particles of metallic sulfide resulting from sulfurization of the organometallic compound are dispersed in the heat-treated material, and particle size of the metallic sulfide particles is not less than 10 nm and less than 100 nm.