Lithium-Sulfur Battery Electrolyte for Polysulfide Shuttle Suppression
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Solution Overview
Problem
Lithium-sulfur batteries face challenges in maintaining lifetime and capacity due to side reactions and polysulfide shuttle phenomena, leading to reduced efficiency and reactivity, despite efforts to improve with lanthanum nitrate and other additives in existing electrolyte solutions.
Innovation Solution
An electrolyte solution combining a heterocyclic compound with double bonds and oxygen or sulfur atoms, an ether-based solvent, lithium salt, lanthanum nitrate, and lithium nitrate, which forms a protective film on the lithium metal surface to suppress polysulfide leaching and enhance ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional electrolyte solution is used to enable lithium-sulfur battery operation, then the battery can function, but polysulfide leaching and shuttle phenomena occur leading to reduced lifetime and capacity
Solution Approach 1:
A co-solvent comprising a cyclic carbonate and a chain carbonate is introduced as an intermediary component in the electrolyte solution. This co-solvent mixture mediates between the lithium salt and the heterocyclic compound solvent, forming a balanced solvent system that suppresses polysulfide dissolution and shuttle phenomena while maintaining electrochemical performance, thereby resolving the contradiction between battery functionality and polysulfide stability
Solution Approach 2:
The electrolyte solution employs a composite solvent system combining three components: a heterocyclic compound (high reactivity), a co-solvent mixture of cyclic and chain carbonates (balanced properties), and lithium salt. This composite approach integrates materials with complementary characteristics to achieve both high capacity and long lifetime by preventing polysulfide leaching while maintaining ion conductivity
2Quantity of substance
If a highly reactive solvent and lithium salt are used to increase battery capacity, then capacity improves, but side reactions occur reducing lifetime
Solution Approach 1:
The electrolyte composition parameters are precisely optimized: the heterocyclic compound content is controlled at 70-95 vol% to maintain high reactivity and capacity, while the co-solvent mixture (cyclic carbonate 5-20 vol% + chain carbonate 5-20 vol%) is added in controlled amounts to suppress side reactions. The lithium salt concentration is optimized at 0.5-2.0 M. These parameter adjustments balance capacity and lifetime by controlling reaction kinetics and stability
Solution Approach 2:
A composite electrolyte system is created integrating a heterocyclic compound (for high capacity), a co-solvent mixture of cyclic and chain carbonates (for stability), and lithium salt. This composite material approach combines components with opposing characteristics - high reactivity versus high stability - to achieve both high capacity and long lifetime simultaneously by preventing detrimental side reactions
3Reliability
If a highly stable solvent and lithium salt are used to increase battery lifetime, then lifetime improves, but capacity increases less
Solution Approach 1:
The electrolyte formulation uses a heterocyclic compound at 70-95 vol% (high reactivity for capacity) combined with a co-solvent mixture at 10-40 vol% total (stability for lifetime). This parameter optimization ensures that the stable co-solvent components do not dominate the system, allowing high capacity to be maintained while their stabilizing effect prevents side reactions and extends lifetime
4Reliability
If lanthanum nitrate is added to improve coulombic efficiency, then efficiency improves, but the electrolyte composition becomes more complex
Solution Approach 1:
Lanthanum nitrate is incorporated into the electrolyte solution to perform multiple functions simultaneously: it improves coulombic efficiency by suppressing polysulfide dissolution, stabilizes the electrode interfaces, and enhances overall battery performance. This multi-functional additive justifies its inclusion despite the increased compositional complexity, as it addresses multiple problems with a single component
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 solution significantly improves the cycle lifetime and coulombic efficiency of lithium-sulfur batteries by reducing polysulfide shuttle and side reactions, thereby enhancing both capacity and longevity.
Implementation Method 1
combining a highly reactive solvent and lithium salt which can increase the capacity of the battery, and a highly stable solvent and lithium salt which can increase the lifetime of the battery
Implementation Method 2
An electrolyte solution combining a heterocyclic compound with double bonds and oxygen or sulfur atoms, an ether-based solvent, lithium salt, lanthanum nitrate, and lithium nitrate, which forms a protective film on the lithium metal surface to suppress polysulfide leaching and enhance ion conductivity
Implementation Method 3
since polysulfide leached from the positive electrode has high solubility in the organic electrolyte solution, it can undesirably move toward the negative electrode (PS shuttling) through the electrolyte solution
Data Source
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AI summary
Disclosed are an electrolyte solution for the lithium secondary battery, which can improve the performance of the battery, by combining a highly reactive solvent and lithium salt which can increase the capacity of the battery, and a highly stable solvent and lithium salt which can increase the lifetime of the battery, and a lithium secondary battery comprising the same. The electrolyte solution for the lithium secondary battery comprises a first solvent comprising a heterocyclic compound containing one or more double bonds and at the same time, containing any one of an oxygen atom and a sulfur atom; a second solvent comprising at least one of an ether-based compound, an ester-based compound, an amide-based compound, and a carbonate-based compound; lithium salt; lanthanum nitrate; and an additive comprising lithium nitrate.