All-solid-state lithium sulfur cathode mixture
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Solution Overview
Problem
All-solid-state lithium sulfur batteries face challenges in achieving sufficient charge/discharge capacity, especially at high current levels due to the low electron conductivity and lithium-ion conductivity of the cathode mixture layer, which limits the practical application of sulfur's high theoretical capacity.
Innovation Solution
A cathode mixture comprising an ion-conductive material with phosphorus at a specific weight ratio, sulfur or its discharge product, and a conductive material, where the sulfur and/or its discharge product constitutes 40% or more of the total weight, is used to reduce reaction resistance and enhance conductivity, thereby improving charge/discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfur is used as cathode active material to achieve high theoretical capacity, then charge/discharge capacity is improved, but electron conductivity and lithium-ion conductivity of cathode mixture layer deteriorate due to electrical insulation properties of sulfur
Solution Approach 1:
The patent applies composite materials by combining sulfur with conductive materials (such as carbon materials) and ion-conductive materials (such as solid electrolytes) to form a cathode mixture. This composite structure allows the sulfur to provide high theoretical capacity while the conductive and ion-conductive components compensate for sulfur's poor conductivity, thereby resolving the contradiction between capacity and conductivity.
Solution Approach 2:
The patent introduces ion-conductive materials (solid electrolytes) as intermediaries between sulfur and the lithium anode. These intermediary materials facilitate lithium-ion transport through the cathode mixture layer, overcoming sulfur's electrical insulation properties and enabling sufficient ionic conductivity while maintaining high sulfur content for capacity.
2Object-affected harmful factors
If traditional cathode mixture layer is used in all-solid-state lithium sulfur batteries, then safety is improved by eliminating combustible organic solvents, but charge/discharge capacity deteriorates at practical high currents due to low conductivity
Solution Approach 1:
The patent changes the compositional parameters of the cathode mixture by optimizing the ratios of sulfur, conductive materials, and ion-conductive materials. By adjusting these parameters, the cathode mixture achieves sufficient conductivity to support practical high-current applications while maintaining the safety advantages of all-solid-state construction without combustible solvents.
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 cathode mixture significantly enhances the charge/discharge capacity of all-solid-state lithium sulfur batteries, ensuring high performance at both low and high current levels, including practical applications such as smartphones and electric vehicles.
Implementation Method 1
the ion-conductive material is (A) an ion-conductive material containing phosphorus in a specific amount (weight ratio)... it is possible to reduce resistance (reaction resistance) during the reaction of sulfur, electrons, and lithium ions at the reaction interface
Implementation Method 2
the cathode mixture obtained by mixing an ion-conductive material, sulfur and/or its discharge product, and a conductive material... improve the charge/discharge capacity... by reducing resistance
Implementation Method 3
In the cathode mixture layer of the all-solid-state lithium sulfur batteries, a reversible reaction represented by the following formula (1) occurs, wherein the reaction toward the right predominantly proceeds during discharge, and the reaction toward the left predominantly proceeds during charge. S+2Li++2e−⇄Li2S
Data Source
AI summary
The present invention aims to maximize the advantageous physical properties of sulfur and provide a cathode mixture that can be suitably used in a cathode mixture layer of an all-solid-state lithium sulfur battery exhibiting excellent charge/discharge capacity. The present invention also aims to provide an all-solid-state lithium sulfur battery including a cathode mixture layer containing the cathode mixture. The present invention provides a cathode mixture for use in a cathode mixture layer of an all-solid-state lithium sulfur battery, the cathode mixture containing: (A) an ion-conductive material containing phosphorus at a weight ratio of 0.2 to 0.55; (B) sulfur and/or its discharge product (B); and (C) a conductive material, the amount of the component (B) being 40% by weight or more of the total amount of the components (A), (B), and (C).