Built-in electric field by CoSe2-CoS2 mott schottk heterostructure: Promoting rapid conversion and ordered deposition of polyselenides in lithium selenium batteries

Selenium cathodes have attracted particular interest due to their high volumetric capacity and electronic conductivity compared to sulfur cathodes. However, slow conversion reaction kinetics and shuttle effect of polyselenides lead to poor cycling performance of lithium selenium batteries. To overcome these limitations, this paper designs a cobalt selenide-sulfide mott schottkyl heterostructure catalyst on carbon fibers (CoSe2-CoS2@CNF). Through the built-in electric field and high catalytic activity of heterostructure, the CoSe2-CoS2@CNF effectively decreases the nucleation barrier for polyselenides, enhances the liquid–solid conversion process and ultimately realizes ordered radial deposition of polyselenides on carbon fibres. Density functional theory calculations also prove that CoSe2-CoS2 mott schottkyl heterostructure has the highest catalytic activity and accelerates the rapid conversion of polyselenides. As a result, Se/CoSe2-CoS2@CNF free-standing electrodes exhibit a high initial specific capacity of 401.6 mAh g−1 at 5C and maintained a capacity of 410.2 mAh g−1 after 1000 cycles at 0.5C, with a capacity decay rate of only 0.04% per cycle. This work opens up a new field for achieving high stability lithium selenium batteries by forming mott schottkyl heterostructure structures to promote rapid conversion and ordered deposition of polyselenides.