Lithium Secondary Battery Electrolyte for Polysulfide Shuttle Suppression
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Solution Overview
Problem
Lithium-sulfur batteries face challenges with reduced lifetime and discharging capacity due to polysulfide shuttle phenomena and increased cell resistance at low temperatures, which are exacerbated by the properties of the electrolyte solution.
Innovation Solution
An electrolyte solution comprising a glyme-based compound, a conjugated heterocyclic compound, a non-conjugated cyclic ether-based compound, and lithium salt, which reduces polysulfide leaching, forms a protective film on the lithium metal surface, and moderates viscosity, thereby stabilizing the battery performance at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte solutions are used in lithium-sulfur batteries, then the batteries can operate at normal temperatures, but the discharging capacity and lifetime are significantly reduced due to polysulfide shuttle phenomena and high cell resistance at low temperatures
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolyte by incorporating specific additives (LiNO3, TBTA, and cyclic carbonates) into the glyme-based electrolyte system. These compositional changes alter the electrochemical properties of the electrolyte, enabling it to suppress polysulfide dissolution and reduce cell resistance at low temperatures, thereby simultaneously improving battery lifetime and low-temperature discharging capacity
Solution Approach 2:
The patent creates a composite electrolyte system by combining multiple components: glyme-based solvents (DMOE, DEE, MEOE), lithium salts (LiFSI, LiNO3), chelating agents (TBTA), and cyclic carbonates (EC, PC). This composite formulation works synergistically to address both polysulfide shuttle phenomena and low-temperature resistance issues, achieving improved reliability and productivity simultaneously
2Productivity
If the electrolyte solution is designed to reduce resistance for low-temperature operation, then the discharging capacity improves, but the lifetime characteristics deteriorate due to increased side reactions and polysulfide leaching
Solution Approach 1:
The patent introduces TBTA (tertiary butyltriazolylborane) as an intermediary chelating agent that specifically binds to lithium polysulfides, forming stable complexes that prevent polysulfide dissolution into the bulk electrolyte. This intermediary substance mediates between the lithium polysulfide and the electrolyte, reducing both polysulfide leaching (improving lifetime) and maintaining ionic conductivity (preserving low-temperature capacity)
3Productivity
If sulfur is allowed to leach into the electrolyte solution forming lithium polysulfide, then the electrochemical reactions can proceed, but the polysulfide shuttles to the negative electrode causing capacity loss and reduced lifetime
Solution Approach 1:
The patent converts the harmful polysulfide dissolution phenomenon into a beneficial process by using TBTA chelating agents that selectively bind to lithium polysulfides. The polysulfides that would normally shuttle harmfully are instead captured by TBTA, forming stable soluble complexes that remain in the electrolyte without causing shuttle effects. This transforms the harmful dissolution into a controlled, beneficial interaction that maintains electrochemical reactivity while preventing polysulfide loss
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 enables lithium-sulfur batteries to maintain 90-97% discharging capacity retention at 15°C or less and extends the battery's lifetime by reducing cell resistance and polysulfide decomposition, ensuring stable performance in low-temperature conditions.
Implementation Method 1
the leaching and shuttle phenomenon of lithium polysulfide occurs during charging/discharging, and the lithium polysulfide is transferred to the negative electrode
Implementation Method 2
An electrolyte solution comprising a glyme-based compound, a conjugated heterocyclic compound, a non-conjugated cyclic ether-based compound, and lithium salt, which reduces polysulfide leaching
Implementation Method 3
the reduction reaction of sulfur and the oxidation reaction of lithium metal take place during discharging
Implementation Method 4
moderates viscosity, thereby stabilizing the battery performance at low temperatures
Data Source
AI summary
An electrolyte solution for a lithium secondary battery, which is capable of not only operating at a low temperature by lowering resistance, but also securing the stable lifetime characteristics of the battery, and increasing the discharging capacity at a low temperature. The electrolyte solution for the lithium secondary battery includes a first solvent including at least one glyme-based compound; a second solvent including at least one conjugated heterocyclic compound; a third solvent including at least one non-conjugated cyclic ether-based compound; and lithium salt.