All-solid-state battery sulfur loading via composite electrode
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Solution Overview
Problem
All-solid-state lithium-sulfur secondary batteries face challenges with low electron conductivity and ion conductivity, limiting the amount of sulfur that can be loaded and resulting in rapid capacity deterioration at higher sulfur loadings.
Innovation Solution
Incorporating a sulfur-containing positive electrode active material with elemental sulfur and transition metal disulfide, such as iron disulfide, along with a halogen-containing sulfide solid electrolyte and conductive carbon material, to enhance ion and electron conductivity and maintain the crystal structure of the transition metal disulfide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large amount of sulfur is loaded per unit area to increase specific capacity, then the battery's energy density improves, but electron conductivity and ion conductivity decrease, causing rapid capacity deterioration
Solution Approach 1:
The patent introduces a solid electrolyte layer as an intermediary between the sulfur-containing positive electrode and the negative electrode. This solid electrolyte mediates ion transport while maintaining structural stability, enabling higher sulfur loading without the dissolution problems associated with liquid electrolytes. The solid electrolyte acts as a buffer that allows increased sulfur content while preventing the harmful effects that would otherwise limit capacity retention.
Solution Approach 2:
The positive electrode is designed as a composite material system containing sulfur, conductive carbon, and transition metal compounds. This composite structure combines the high capacity of sulfur with the conductivity benefits of carbon and the structural stability of transition metals, resolving the contradiction between loading amount and conductivity by integrating multiple materials with complementary properties.
2Quantity of substance
If sulfur loading is increased beyond 1 mg/cm² to improve specific capacity, then energy density increases, but ion conductivity decreases, resulting in rapid capacity loss at loadings of 4-5 mg/cm² or higher
Solution Approach 1:
The solid electrolyte serves as an intermediary that facilitates ion transport through the positive electrode layer containing high sulfur content. Unlike liquid electrolytes that allow polysulfide dissolution, the solid electrolyte provides a stable medium for ion conduction even when sulfur loading is increased to 10 mg/cm² or higher, maintaining ion conductivity while enabling increased capacity.
Solution Approach 2:
The patent changes the physical state parameter of the electrolyte from liquid to solid, fundamentally altering the transport mechanism. This parameter change enables the system to accommodate higher sulfur concentrations without the dissolution and conductivity loss problems that plague liquid electrolyte systems, allowing sulfur loading to be increased from the conventional 1 mg/cm² to much higher levels.
3Duration of action of stationary object
If all-solid-state materials are used to eliminate polysulfide dissolution, then cycle stability improves, but electron conductivity and ion conductivity become insufficient, limiting sulfur loading to 1 mg/cm²
Solution Approach 1:
The positive electrode is constructed as a composite containing sulfur, conductive carbon, and transition metal compounds. The conductive carbon network provides electron conductivity pathways, while the transition metal compounds enhance ion conductivity and structural stability. This composite approach maintains the cycle stability benefits of all-solid-state construction while compensating for conductivity limitations through material composition optimization.
Solution Approach 2:
The patent creates local conductive pathways within the positive electrode by distributing conductive carbon and transition metal compounds throughout the sulfur matrix. This local quality enhancement ensures that electron and ion transport can occur efficiently even when sulfur loading is increased, addressing the conductivity bottleneck without sacrificing the cycle stability provided by the solid-state architecture.
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
This configuration allows for a significant increase in specific capacity even at higher sulfur loadings, improving the battery's performance and extending its cycle life.
Implementation Method 1
a halogen-containing sulfide solid electrolyte... to enhance ion and electron conductivity
Implementation Method 2
a conductive carbon material... to enhance ion and electron conductivity
Data Source
AI summary
An all-solid-state secondary battery including: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer includes a sulfur-containing positive electrode active material, a halogen-containing sulfide solid electrolyte, and a conductive carbon material, and wherein the sulfur-containing positive electrode active material includes elemental sulfur and a transition metal disulfide.