Lithium-Sulfur Battery Electrode Structure for High Energy Density
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Solution Overview
Problem
Lithium-sulfur batteries face challenges in achieving high energy density due to inefficiencies in the positive electrode, degradation of the negative electrode, and excessive use of electrolyte, which limits their theoretical capacity and energy density.
Innovation Solution
A lithium-sulfur battery design incorporating a sulfur-carbon composite positive electrode with a specific XRD pattern and optimized sulfur loading, electrolyte ratio, and structural components to enhance energy density, including a sulfur-carbon composite with a high S/C weight ratio and a method for evaluating energy density through XRD analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a sulfur-based material is used as a positive electrode active material to achieve high theoretical energy density, then the theoretical energy density increases, but the actual energy density does not reach the theoretical value due to decreased efficiency of the positive electrode
Solution Approach 1:
The patent uses a sulfur-carbon composite material where sulfur particles are embedded in a conductive carbon matrix. This composite structure maintains the high theoretical energy density of sulfur while the carbon component provides electrical conductivity and structural stability, preventing the positive electrode efficiency from deteriorating during charge-discharge cycles.
Solution Approach 2:
The patent employs a porous carbon structure with controlled pore size and distribution. The porous structure provides large surface area for sulfur loading, facilitates electrolyte penetration and ion transport, and maintains structural integrity during volume changes, thereby preserving positive electrode efficiency while achieving high energy density.
2Productivity
If the amount of electrolyte is increased to ensure proper ion transport, then ion transport is improved, but the energy density decreases due to the large amount of electrolyte
Solution Approach 1:
The patent creates local high-concentration electrolyte environments within the porous carbon structure and at the electrode-electrolyte interfaces. This localized electrolyte distribution ensures sufficient ion transport where needed while minimizing the overall electrolyte volume, thereby maintaining ion transport efficiency without sacrificing energy density.
Solution Approach 2:
The patent uses thin film electrodes with optimized thickness and porous structure. The thin film design reduces the electrolyte volume required while maintaining adequate ion transport pathways, achieving a balance between ion transport efficiency and energy density.
3Quantity of substance
If the sulfur loading amount is increased to improve capacity, then the discharge capacity increases, but the structural stability deteriorates leading to negative electrode degradation
Solution Approach 1:
The patent uses sulfur-carbon composite where the carbon matrix provides structural stability and mechanical strength. The sulfur particles are dispersed within the carbon structure, allowing high sulfur loading while the carbon framework prevents structural collapse and negative electrode degradation during cycling.
Solution Approach 2:
The patent employs a nested structure where sulfur particles are embedded within porous carbon, which in turn is supported on a current collector framework. This nested architecture allows high sulfur content while maintaining structural integrity and preventing degradation through multiple protective layers.
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 battery achieves an energy density of 430 Wh/kg or higher by maintaining high reactivity and stability, overcoming previous limitations in lithium-sulfur battery performance.
Implementation Method 1
a positive electrode where the conversion of lithium ions and sulfur occurs (S8+16Li++16e−→8Li2S)
Implementation Method 2
a carbon-based material wherein intercalation/deintercalation of lithium ions occurs
Implementation Method 3
diffraction angles (2θ values) of X-ray diffraction (XRD) patterns
Implementation Method 4
diffraction angles (2θ values) of X-ray diffraction (XRD) patterns
Data Source
AI summary
A lithium-sulfur battery having high energy density and a method for manufacturing the same are provided. The lithium-sulfur battery at depth of discharge (DOD) 15% to DOD 80% includes a compound having three or more characteristic peaks of diffraction angles (2θ values) of X-ray diffraction (XRD) patterns selected from 7.1±0.2°, 9.0±0.2°, 9.4±0.2°, 9.6±0.2°, 9.9±0.2°, 10.0±0.2°, 10.4±0.2°, 11.0±0.2°, 11.6±0.2°, 12.1±0.2°, 13.3±0.2°, 14.5±0.2° and 15.0±0.2°.