Oriented loading and enduring confinement endow long-life-span Se cathode based on chemical affinity

Abstract

Reversible electrochemical conversion between selenium (Se) and lithium selenide (Li2Se) can be achieved in the carbonate-based electrolytes through a solid-solid phase transformation, avoiding the fatal shuttle effect of intermediate products in the ethter-based electrolytes. However, the solid-solid conversion puts forward more stringent requirements on the initial distribution state of active Se, which cannot be satisfied by the existing physical methods for Se loading. Herein, a novel in-situ oxidization strategy is developed to construct an ideal Se/dual-carbon composite (marked as Gr@Se⊂HC). In the process, under the guidance of the N/O heteroatoms, Se molecules oxidized from the pre-embedded ZnSe are orientedly deposited inside of the hollow carbon (HC) boxes that are implanted on the 3D graphene scaffold. More impressively, the durable chemical confinement effect from the N/O functional groups during the overall lithiation/delithiation process and the fast electron transfer path provided by the delicate graphene (Gr) framework contribute to the suppressive micro-structure degradation and rapid interfacial charge transfer. Thereby, Gr@Se⊂HC delivers the ultra-long cycle life and the outstanding high-rate capability. This work proposes an original strategy for the synthesis of Se cathode and opens a new route for propelling the development of the long-life-span Li-Se batteries.