Lithium selenide

Lithium selenide is an inorganic compound that formed by selenium and lithium. It is a selenide with a chemical formula Li₂Se. Lithium selenide has the same crystal form as other selenides, which is cubic, belonging to the anti-fluorite structure, the space group is ${\displaystyle Fm{\bar {3}}m}$ , each unit cell has 4 units.^[1]

Lithium Selenide can be synthesized via the reaction between 1.0 equivalents of grey elemental selenium and 2.1 equivalents of lithium trialkylborohydride. The reaction takes place in a solution of THF (tetrahydrofuran) under  with stirring (minimum of 20 minutes) at room temperature according to the reaction below:^[5] To increase yields and harmful byproducts, naphthalene can be added to the reaction as a catalyst.^[6]

Se + 2Li(C₂H₅)₃BH → Li₂Se + 2(C₂H₅)₃B + H₂

Another method of synthesis involves the reduction of selenium with lithium in liquid ammonia. The Li₂Se can be extracted after evaporation of the ammonia.^[6]

One of the most contemporary uses of Li₂Se compounds is in the creation of high-density capacitors and batteries. Lithium selenide can act as an excellent prelithiation agent, which helps to prevent the loss of capacity and efficiency during the formation of the solid electrolyte interphase (SEI). Additionally, the high relative conductivity and solubility of the products of lithium selenide decomposition makes it an ideal prelithiation agent. No harmful byproducts or gases are created during this decomposition of Li₂Se.^[7] One potential drawback to the use of Li₂Se is the dissolution and shuttle problems inherent to the transition metals like selenide. To avoid this problem, evolving heterostructure materials can be used to inhibit the dissolution and shuttle effects of Li₂Se.^[8]