Solid‐State Lithium/Selenium–Sulfur Chemistry Enabled via a Robust Solid‐Electrolyte Interphase

Abstract

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 long‐term 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.

In Batteria Electrochemical Polymerization to Form a Protective Conducting Layer on Se/C Cathodes for High‐Performance Li–Se Batteries

“…Recently, lithium–selenium (Li–Se) batteries have been considered one of the promising next‐generation batteries not only because they offer a high energy density (2528 Wh L −1 ), which is higher than that of graphite–LiFePO 4 and comparable to that of Li–S batteries, but also because the active material, Se, has a higher electrical conductivity compared with S and LiFePO 4 (10 −3 S m −1 of Se vs 10 −28 S m −1 of S and 10 −7 S m −1 of LiFePO 4 ). [ 5,7,10–26 ] Therefore, a higher utilization of Se in LiBs provides a higher energy density in spite of the lower amount of conductive carbon. [ 12,20–22 ] Moreover, the compatibility of Se with low‐cost carbonate‐based electrolytes reduces costs and mitigates capacity decay, unlike in Li–S batteries where the nucleophilic reaction of carbonyl groups with S degrades the cell performance.…”

Beyond the Polysulfide Shuttle and Lithium Dendrite Formation: Addressing the Sluggish Sulfur Redox Kinetics for Practical High‐Energy Li‐S Batteries

“…[20] Therefore, they have been widely used as diluents or cosolvents to boost the electrolyte properties. [11,14,24,30] Wang et al thus proposed an LHCE by adding af luorinated ether diluent into concentrated LiFSI/DME electrolytes to enable the operation of Li-S cells in alean electrolyte,however, the Sloading is still within 1-2 mg cm À2 . [11] Recently,S ed oping has been proven to effectively enhance the Sredox kinetics in various electrolytes.…”

A Selection Rule for Hydrofluoroether Electrolyte Cosolvent: Establishing a Linear Free‐Energy Relationship in Lithium–Sulfur Batteries

“…For these new battery systems to be successful, it is critical to develop reliable electrolytes and to understand their working principles . First introduced as an electrolyte cosolvent a decade ago, hydrofluoroethers (HFEs) have rapidly been employed by researchers all over the world to construct functional electrolytes for high‐voltage lithium‐ion, lithium‐metal, lithium–sulfur (Li–S), lithium–air, lithium/selenium–sulfur, and even sodium‐ion batteries . Because of their low solvating ability, HFEs are exceptionally versatile as electrolyte cosolvents.…”