Competition between Li2Se2Sx conversion and Li Ion transport on graphene surface coordination doped with transition metal and N

Abstract

The shuttling of polyselenide (Li2Se2Sx) was prevented effectively by building a separator in Li-SexSy batteries. Nitrogen atoms are used to coordinate transition metal (TM=Ti, Zr, V) co-doped graphene to restrict the free shuttling of polylithium selenide (Li2Se2Sx, x = 1–6) through physical confinement and chemical adsorption. The nitrogen (N) atom assisted transition metal co-doped graphene surface to build a model of strong adsorption of cations and anions on lithium-sulfur-selenium compounds to inhibit the shuttle phenomenon. Nitrogen atoms are not only coordinately doped with transition metals, but also lithium atoms can easily form bonds to improve the adsorption strength of Li2Se2Sx on the graphene surface. The evolution of the N-type to P-type adsorption model of Li2Se2Sx on the graphene co-doped Ti-N-G surface to the Zr-N-G surface was constructed based on the phenomenon of Fermi level changes strong adsorption capacity and immobilization. The Fermi energy level of the V-N-G weak adsorption catalytic model was located between the valence and conduction bands. The doping of N and TM improves the ionic conductivity of graphene, which adsorbs Li2Se2Sx and causes a high Li diffusion barrier. A coupled physical model of ion transport and polyselenide conversion was built by adjusting the Fermi level of separator.

Keywords

• Coordinated doping separator
• Fermi level
• Ion transport
• Density functional theory calculation