Lithium-Sulfur Battery Electrolyte Ratio for High Energy Density
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Solution Overview
Problem
Lithium-sulfur batteries do not achieve their full theoretical energy density due to inefficiencies in the positive electrode and large amounts of electrolyte, leading to suboptimal performance in applications requiring high capacity and energy density.
Innovation Solution
A lithium-sulfur battery design with a sulfur-carbon composite positive electrode, specific sulfur loading amounts, and controlled electrolyte-to-sulfur ratios, along with characteristic X-ray diffraction peaks, to optimize energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of electrolyte is used in the lithium-sulfur battery, then the battery can operate smoothly, but the energy density decreases due to the increased weight
Solution Approach 1:
The patent optimizes the electrolyte-to-sulfur weight ratio parameter to specific ranges (1.3-2.5:1, preferably 1.5-2.0:1) to achieve the best balance between battery operation stability and energy density. This parameter optimization allows the battery to maintain smooth operation while minimizing electrolyte weight, thereby maximizing energy density.
Solution Approach 2:
The patent uses sulfur-carbon composite materials where sulfur is embedded in a carbon matrix. This composite structure allows for reduced electrolyte content while maintaining battery performance, as the carbon matrix provides structural support and conductive pathways, reducing the need for excessive electrolyte and thus improving energy density.
2Quantity of substance
If the sulfur loading amount in the positive electrode is increased to achieve high capacity, then the theoretical capacity increases, but the positive electrode efficiency decreases
Solution Approach 1:
The patent employs sulfur-carbon composite structures where sulfur is locally distributed within a conductive carbon matrix. This local quality approach ensures that sulfur is positioned optimally within the electrode, maintaining high sulfur loading while preserving electron transport pathways through the carbon matrix, thus sustaining positive electrode efficiency despite increased sulfur content.
Solution Approach 2:
By creating sulfur-carbon composites with specific sulfur loading densities, the patent achieves high capacity while maintaining efficiency. The carbon matrix provides a conductive network that prevents aggregation of sulfur particles, ensuring efficient electron and ion transport even at high sulfur loadings.
3Use of energy by moving object
If the sulfur loading amount is increased to improve energy density, then more lithium ions can be stored, but the negative electrode undergoes degeneration
Solution Approach 1:
The patent introduces an intermediary layer or coating on the negative electrode that mediates between the high sulfur loading in the positive electrode and the negative electrode material. This intermediary structure prevents direct harmful interactions, reduces polysulfide shuttling to the negative electrode, and protects the negative electrode from degeneration, enabling high energy density to be achieved without compromising negative electrode stability.
4Use of energy by moving object
If the electrolyte-to-sulfur ratio is reduced to improve energy density, then less electrolyte weight is used, but the battery performance may deteriorate
Solution Approach 1:
The patent optimizes the electrolyte-to-sulfur weight ratio to specific ranges (1.3-2.5:1, preferably 1.5-2.0:1) that balance energy density and battery performance. Within this optimized range, the battery achieves high energy density while maintaining adequate ionic conductivity and electrochemical performance, avoiding the performance deterioration that would occur with excessive electrolyte reduction.
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 300 Wh/kg or higher, with a sulfur loading of 1.4 mAh/cm² or more, and a weight ratio of electrolyte to sulfur of 2.5 or less, enhancing its performance for high-capacity applications.
Implementation Method 1
the conversion of lithium ions and sulfur occurs (S 8 + 16Li
Implementation Method 2
a carbon-based material wherein intercalation/deintercalation of lithium ions occurs
Implementation Method 3
silicon or tin that forms an alloy with lithium
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The present disclosure relates to a lithium-sulfur battery comprising: an electrode assembly, an electrolyte, and a case accommodating the electrode assembly, wherein the electrode assembly comprises a positive electrode comprising a sulfur-carbon composite, a negative electrode and a separator disposed between the positive electrode and the negative electrode, wherein the lithium-sulfur battery fulfills the following requirement of equation 1: SX=SPE/SEL/S, wherein SPE is the sulfur (S) loading amount of the positive electrode as a mAh/cm2 value, SEL/S is the weight ratio of the electrolyte and sulfur (S) as a dimensionless value, and wherein SX is the sulfur (S) loading amount of the positive electrode per ratio of electrolyte and sulfur, and SX is 1.4 mAh/cm2 or higher, preferably in a range between 1.4 and 10 mAh/ cm2, or wherein the lithium-sulfur battery contains a compound comprising three or more characteristic diffraction angle peaks (2θ values) selected from the following: 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° in the X-ray diffraction (XRD) pattern at DOD 15% to DOD 80%. Furthermore, a method for evaluating the energy density of a lithium-sulfur battery.