Lithium Sulfide

Lithium Sulfide (Li₂S) is an inorganic compound made of lithium and sulfur. It is primarily used in the battery industry, especially in lithium-sulfur (Li-S) batteries, which are seen as a promising technology for high-capacity energy storage due to their high theoretical energy density and lightweight design.

Physical Properties:

Chemical formula：Li2S

CAS#:12136-58-2

Molar mass：45.95 g/mol

Appearance：white solid

Density：1.67 g/cm3

Melting point：938 °C (1,720 °F; 1,211 K)

Boiling point：1,372 °C (2,502 °F; 1,645 K)

Solubility in water：very soluble, hydrolyses to LiOH and H2S

Solubility：very soluble in ethanol

Crystal structure：Antifluorite (cubic), cF12

Thermal and Chemical Properties:

High Ionic Conductivity: Li₂S has high ionic conductivity, making it ideal for use as a solid electrolyte or cathode material in batteries.

Reactivity: Lithium sulfide can react with moisture in the air, producing toxic hydrogen sulfide gas. Therefore, it must be handled in a dry or controlled environment.

Thermal Stability: Li₂S is stable at high temperatures, which is advantageous in battery applications where thermal management is crucial.

Applications:

Lithium-Sulfur (Li-S) Batteries: Lithium sulfide is a key component in Li-S batteries, serving as either the cathode material or a precursor for creating other sulfur-based compounds. Li-S batteries are considered a potential alternative to lithium-ion batteries due to their higher theoretical energy density.

Solid-State Batteries: Li₂S can be used as a solid electrolyte in solid-state lithium batteries, contributing to enhanced safety, higher energy capacity, and the potential for longer cycle life.

Material Synthesis: Lithium sulfide serves as a precursor in the synthesis of lithium-containing sulfide materials, which are often used in solid-state electrolytes for advanced battery technologies.

Limitations:

Sensitivity to Moisture: Li₂S is highly reactive with water, which can release toxic hydrogen sulfide gas. This limits its handling and storage to controlled, dry environments.

Stability Issues in Batteries: Lithium-sulfur batteries using Li₂S are prone to issues such as the “shuttling effect,” where polysulfide intermediates dissolve in the electrolyte, leading to reduced cycle life and efficiency.

Handling and Storage:

Controlled Environment: Lithium sulfide should be stored in tightly sealed containers and handled in dry, inert atmospheres to prevent reaction with moisture.

Safety Precautions: Protective equipment (gloves, goggles, and respiratory protection) is recommended to avoid exposure to toxic hydrogen sulfide gas if Li₂S comes into contact with water or humid air.