Electrolyte for lithium-sulfur batteries and lithium-sulfur battery comprising the same

Lithium-sulfur electrolyte converting polysulfides into a polymer membrane using an isocyanate additive

This technology incorporates an additive with isocyanate (-N=C=O) functional groups into the lithium-sulfur battery electrolyte. It selectively reacts with lithium polysulfides dissolved from the cathode to create an ion-conductive polymer layer at the interface between the electrode and the separator.

In lithium-sulfur batteries, lithium polysulfides generated at the cathode during discharge dissolve into the electrolyte and diffuse to the anode. This leads to reduced capacity and side reactions that corrode the anode, ultimately degrading cycle life and electrochemical performance.

This technology involves adding 1 to 5 parts by weight of an isocyanate-based additive, such as hexamethylene diisocyanate (HDI), per 100 parts by weight of the electrolyte. The additive reacts chemically with lithium polysulfides to form a polymer membrane on the surfaces of the cathode and separator, physically and chemically blocking further polysulfide dissolution. A key advantage is that it can be applied to existing lithium-sulfur cell production lines using ether-based electrolytes, enabling shuttle suppression simply by adding the additive without requiring changes to electrodes or separators.

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Key Features:

• Base electrolyte forming the fundamental composition of the lithium-sulfur battery electrolyte, including lithium salts and organic solvents
• Electrolyte additive containing isocyanate functional groups and consisting of one or more diisocyanate compounds, such as hexamethylene diisocyanate
• Non-aqueous organic solvent consisting of one or more of the following: ether-based materials, 1,2-dimethoxyethane, 1,3-dioxolane, or dimethyl sulfoxide
• Polymer layer formed by the reaction between lithium polysulfides and the electrolyte additive, provided on at least one of the cathode or separator

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This invention was developed with support from the Ministry of Science and ICT for the optimal design of high-ion-conductivity solid electrolytes with 3D ion channels and high-capacity electrodes.

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