LAUSR

The urgent demand on the development of power sources for electric vehicles has created many opportunities for new energy storage systems.[1] In the past decades, lithium/sulfur (Li/S) battery has received considerable attention because of its high energy density (≈2600 Wh kg−1) and the natural abundance of elemental sulfur.[2] However, the poor electronic conductivity of sulfur and its discharge products (Li2S/Li2S2) presents a critical barrier for high-performance sulfur cathodes with high reversible capacity, long cycle life, and high rate capability.[3,4] A relatively high amount of conductive carbon is usually required to ensure efficient electron transport within the sulfur electrodes to enable high utilization of the insulating sulfur. However, carbon is usually electrochemically inactive and thus decreases the overall capacity of the sulfur electrode. Recently, lithium/selenium (Li/Se) battery has attracted research interest Lithium/selenium-sulfur batteries have recently received considerable attention due to their relatively high specific capacities and high electronic conductivity. Different from the traditional encapsulation strategy for suppressing the shuttle effect, an alternative approach to directly bypass polysulfide/polyselenide formation via rational solid-electrolyte interphase (SEI) design is demonstrated. It is found that the robust SEI layer that in situ forms during charge/discharge via interplay between rational cathode design and optimal electrolytes could enable solid-state (de)lithiation chemistry for selenium-sulfur cathodes. Hence, Se-doped S22.2Se/Ketjenblack cathodes can attain a high reversible capacity with minimal shuttle effects during longterm and high rate cycling. Moreover, the underlying solid-state (de)lithiation mechanism, as evidenced by in situ 7Li NMR and in operando synchrotron X-ray probes, further extends the optimal sulfur confinement pore size to large mesopores and even macropores that have been long considered as inferior sulfur or selenium host materials, which play a crucial role in developing high volumetric energy density batteries. It is expected that the findings in this study will ignite more efforts to tailor the compositional/ structure characteristics of the SEI layers and the related ionic transport across the interface by electrode structure, electrolyte solvent, and electrolyte additive screening.