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

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, Li 2 Se 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, Li 2 Se 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 Li 2 Se particles by reacting LiH powers with Se powers (2LiH + Se = Li 2 Se + H 2 ↑). The microstructure of Li 2 Se particles is investigated by cryogenic transmission electron microscopy (cryo-TEM) technology for the first time. The Li 2 Se 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 Li 2 Se and the intriguing design of cathodic structure are highly expected to promote the practical implementation of the safer high energy-density Li–Se batteries. • Li 2 Se is synthesized by ball milling method or heat treatment. • LiH powders react with Se powders to product Li 2 Se particles. • Alternate layer structure Li 2 Se cathode is fabricated by vacuum filtration. • Li 2 Se cathode with high loading exhibit superior electrochemical performance.