All-solid-state lithium-sulfur battery cathode mixture with phosphorus additives
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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 their cathode mixture layers, which limits their practical application in devices like smartphones and personal computers.
Innovation Solution
Incorporating elemental phosphorus or phosphorus sulfide with sulfur and an ion-conductive material, along with an electronically conductive material, in the cathode mixture to enhance the reactivity and conductivity, thereby improving the charge/discharge capacity at both low and high current densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfur is used as cathode active material in all-solid-state lithium-sulfur batteries, then high theoretical capacity (1672 mAh/g) is achieved, but the cathode mixture layer exhibits very low electron conductivity and very low lithium-ion conductivity
Solution Approach 1:
The patent applies composite materials by combining sulfur with carbon materials (graphite, amorphous carbon, carbon nanotubes, or graphene) and conductive metal sulfides (such as FeS2, CoS2, NiS2, or CuS) in specific weight ratios. This composite structure addresses the contradiction by maintaining high charge/discharge capacity from sulfur while the carbon and metal sulfide components provide electron conductivity and lithium-ion conductivity pathways, enabling practical reactivity during charge and discharge cycles.
2Object-affected harmful factors
If traditional cathode mixture layer is used in all-solid-state lithium-sulfur batteries, then safety is ensured without combustible organic solvents, but insufficient charge/discharge capacity is achieved at high current levels
Solution Approach 1:
The patent employs composite materials consisting of sulfur (30-70 wt%), carbon materials (10-50 wt%), and conductive metal sulfides (5-30 wt%). This composite structure maintains the safety advantages of all-solid-state batteries by eliminating combustible organic solvents, while simultaneously enabling high charge/discharge capacity at high current levels through the synergistic conductivity contributions of carbon and metal sulfide components.
Solution Approach 2:
The patent applies local quality by creating distinct functional zones within the cathode mixture layer. Sulfur particles provide high capacity regions, carbon materials provide conductivity networks, and metal sulfides provide additional conductivity and catalytic sites. This spatial distribution of different materials with specific local functions enables both safety and high productivity at practical current levels.
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 with elemental phosphorus and phosphorus sulfide improves the reactivity and conductivity, enabling all-solid-state lithium-sulfur batteries to achieve high charge/discharge capacity at various current levels, making them suitable for applications such as electric cars and hybrid cars, and contributing to reduced CO2 emissions.
Implementation Method 1
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
Data Source
Figure 1
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 having 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 relates to a cathode mixture for use in a cathode mixture layer of an all-solid-state lithium-sulfur battery, the cathode mixture containing the following components (A) to (D) : (A) sulfur and/or its discharge product; (B) elemental phosphorus and/or PxSy where x and y independently represent an integer that gives a stoichiometric ratio; (C) an ion-conductive material; and (D) a conductive material.