Regulating the Hidden Solvation‐Ion‐Exchange in Concentrated Electrolytes for Stable and Safe Lithium Metal Batteries
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25 ENERGY STORAGE↗
Engineering topics
Sun, Hui
Publications and source records attributed to Sun, Hui.
High rate and long cycle life in Li-O 2 batteries with highly efficient catalytic cathode configured with Co 3 O 4 nanoflower
The reaction mechanism of non-aqueous Li-O 2 batteries is based on the deposition and decomposition of Li 2 O 2 . The polarization of Li-O 2 batteries can be rapidly increased by operation under a high rate condition, resulting in the early capacity fade of the cells. Therefore, a well-designed catalyst with a unique structure and excellent catalytic ability is an important way to boost the round-trip performance of Li-O 2 batteries, especially under high current density. In this work, a unique nanoflower structure assembled with Co 3 O 4 nanosheets is synthesized by using 2-methylimidazole (2-MIM) as a structural directing agent. X-ray photoelectron spectroscopy (XPS) and Raman spectra reveal abundant oxygen vacancies on the surface of the Co 3 O 4 nanoflower, which are beneficial for oxygen reduction and evolution reactions and long round-trip lifetime. Density functional theory results demonstrate that Co 3 O 4 catalyst with oxygen vacancies could promote the wetting of Li 2 O 2 on substrate and formation of a Li 2 O 2 nanofilm, thereby boosting the discharge capacity of Li-O 2 batteries. On account of the synergistic effect of abundant oxygen vacancies, the unique structure, and excellent oxygen evolution reaction, Co 3 O 4 nanoflower-based cells could deliver ultralong lifetime of 276 and 248 cycles with a discharge capacity of 1000 mAh g(-1) under charge/discharge current densities of 0.5 A g -1 and 1 A g -1 , respectively. Finally, this study has shed light on a new strategy for catalyst preparation for long lifetime Li-O 2 batteries.
25 ENERGY STORAGE↗
Solid-State Lithium/Selenium–Sulfur Chemistry Enabled via a Robust Solid-Electrolyte Interphase
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 here. 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 S 22.2 Se/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 7 Li 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.
(de)lithiation chemistry↗