Facile and efficient synthesis of Li2Se particles towards high-areal capacity Li2Se cathode for advanced Li–Se battery

Abstract Lithium‑selenium (Li–Se) batteries are considered as promising candidates for the next generation battery technology due to their high volumetric energy density and low cost. Compared with Se cathode in Li–Se batteries, Li2Se cathode can not only alleviate the negative effect of volume expansion in the cycle process, but also avoid utilizing lithium foil as the anode. However, Li2Se has received little coverage due to its high cost and difficulty in production. Herein, two facile synthesis routes, including ball milling and direct heating, are successfully developed to produce pure Li2Se particles by reacting LiH powers with Se powers (2LiH + Se = Li2Se + H2↑). The microstructure of Li2Se particles is investigated by cryogenic transmission electron microscopy (cryo-TEM) technology for the first time. The Li2Se cathode with layer-by-layer structure exhibits superior electrochemical performance at high loading (698 mA h g−1@50 mA g−1@10.6 mg cm−2; 333 mA h g−1@1000 mA g−1@7.1 mg cm−2), attributed to the high polyselenides-trapping and reutilization capability of active layer as well as the excellent polyselenides-interception and high conductivity of barrier layers. This innovative synthesis strategy of Li2Se and the intriguing design of cathodic structure are highly expected to promote the practical implementation of the safer high energy-density Li–Se batteries.