Gradient Sulfur Electrode for Lithium-Sulfur Battery Conductivity
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Solution Overview
Problem
Lithium/sulfur batteries face challenges due to sulfur's low electrical conductivity, polysulfide dissolution, and the need for enhanced electrode conductivity to ensure high utilization and long cycle life, which conventional methods fail to address effectively.
Innovation Solution
A sulfur- and carbon-containing electrode with a gradient sulfur content is created by calendaring sulfur and carbon films, eliminating layered interfaces and enhancing conductivity, comprising a core with higher sulfur content gradually reducing to the surfaces, thus improving electrical conductivity and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfur size is reduced to ensure high sulfur utilization and reversible capacitance, then sulfur utilization is improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent applies local quality by creating a gradient sulfur content distribution within the electrode layer, where the core region has high sulfur content for high utilization while the surface regions have lower sulfur content and higher carbon content for enhanced conductivity. This spatial variation in composition allows simultaneous optimization of both sulfur utilization and electrical conductivity.
Solution Approach 2:
The patent uses composite materials by combining sulfur, carbon, and binder in a gradient distribution. The core region contains sulfur-carbon composite with high sulfur content, while the surface regions contain carbon-rich composite structures. This composite approach enables the electrode to achieve both high sulfur utilization and adequate electrical conductivity.
2Loss of energy
If conventional wet coating method is used to coat carbon material on sulfur electrode, then conductivity is improved, but impedance increases due to layered interface
Solution Approach 1:
The patent merges the sulfur-containing layer and carbon-containing layer into a single integrated gradient structure through calendaring. Instead of creating separate layered interfaces, the sulfur and carbon materials are combined in a continuous gradient distribution within one layer, eliminating the harmful interface between distinct layers while maintaining the conductivity benefits of carbon.
Solution Approach 2:
The patent applies parameter changes by varying the sulfur content parameter continuously from the core to the surface of the electrode layer. This gradient parameter variation allows the electrode to achieve optimal balance between conductivity and impedance without creating sharp interfaces that would increase impedance.
3Ease of manufacture
If sulfur content is uniformly distributed in the electrode, then manufacturing is simplified, but conductivity and rate capability deteriorate
Solution Approach 1:
The patent implements local quality by creating a non-uniform gradient distribution of sulfur content within the electrode layer. The core region maintains high sulfur content while surface regions have progressively lower sulfur content. This local variation in composition enhances overall conductivity and rate capability while using a single-layer manufacturing approach.
4Productivity
If polysulfide is allowed to dissolve in electrolyte, then charge-discharge process is facilitated, but cycle lifetime decreases
Solution Approach 1:
The patent applies local quality by creating a gradient sulfur content distribution where surface regions have lower sulfur content. This gradient structure reduces the concentration of polysulfides at the electrode-electrolyte interface, minimizing their dissolution into the electrolyte while still allowing adequate charge-discharge processes to occur in the core region.
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 electrode achieves high conductivity and sustained capacitance even at elevated charge-discharge rates, with minimal capacitance loss over multiple cycles, demonstrating improved battery performance and stability.
Implementation Method 1
a first carbon film and a second carbon film are prepared, a sulfur-carbon composite film is prepared, the sulfur-carbon composite film is sandwiched between the first carbon film and the second carbon film, and then the first carbon film, the sulfur-carbon composite film, and the second carbon film are laminated by using a calendar press
Data Source
AI summary
An electrode is provided, which includes a sulfur- and carbon-containing layer having a carbon material, a sulfur material, and a binder. A sulfur content at a core part of the sulfur- and carbon-containing layer is gradually reduced to a sulfur content at two side surfaces of the sulfur- and carbon-containing layer. The electrode may serve as a positive electrode of a battery. The battery also includes a negative electrode, and an electrolyte liquid between the positive electrode and the negative electrode.