Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH, 43210, USA.
Department of Physics and Astronomy, California State University, 18111 Nordhoff Street, Northridge, CA, 91330, USA.
Angew Chem Int Ed Engl. 2016 Dec 5;55(49):15310-15314. doi: 10.1002/anie.201608607. Epub 2016 Nov 3.
Alkali metal-oxygen batteries are of great interests for energy storage because of their unparalleled theoretical energy densities. Particularly attractive is the emerging Na-O battery because of the formation of superoxide as the discharge product. Dimethyl sulfoxide (DMSO) is a promising solvent for this battery but its instability towards Na makes it impractical in the Na-O battery. Herein we report the enhanced stability of Na in DMSO solutions containing concentrated sodium trifluoromethanesulfonimide (NaTFSI) salts (>3 mol kg ). Raman spectra of NaTFSI/DMSO electrolytes and ab initio molecular dynamics simulation reveal the Na solvation number in DMSO and the formation of Na(DMSO) (TFSI)-like solvation structure. The majority of DMSO molecules solvating Na in concentrated solutions reduces the available free DMSO molecules that can react with Na and renders the TFSI anion decomposition, which protects Na from reacting with the electrolyte. Using these concentrated electrolytes, Na-O batteries can be cycled forming sodium superoxide (NaO ) as the sole discharge product with improved long cycle life, highlighting the beneficial role of concentrated electrolytes for Na-based batteries.
碱金属-氧电池因其无与伦比的理论能量密度而在储能方面具有巨大的吸引力。由于放电产物为超氧化物，新兴的 Na-O 电池特别吸引人。二甲基亚砜（DMSO）是这种电池的一种很有前途的溶剂，但由于其对 Na 的不稳定性，在 Na-O 电池中并不实用。在此，我们报告了在含有浓缩三氟甲磺酸纳（NaTFSI）盐（>3 mol kg-1）的 DMSO 溶液中 Na 的稳定性增强。NaTFSI/DMSO 电解质的拉曼光谱和 ab initio 分子动力学模拟揭示了 DMSO 中 Na 的溶剂化数和 Na(DMSO)(TFSI)样溶剂化结构的形成。在浓溶液中，大多数与 Na 配位的 DMSO 分子减少了可与 Na 反应的游离 DMSO 分子，并使 TFSI 阴离子分解，从而防止 Na 与电解质反应。使用这些浓缩电解质，Na-O 电池可以循环形成过氧化钠（NaO ）作为唯一的放电产物，具有改善的长循环寿命，突出了浓缩电解质对 Na 基电池的有益作用。
