Restructuring Electrolyte Solvation by a Versatile Diluent Toward Beyond 99.9% Coulombic Efficiency of Sodium Plating/Stripping at Ultralow Temperatures,Advanced Materials

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Restructuring Electrolyte Solvation by a Versatile Diluent Toward Beyond 99.9% Coulombic Efficiency of Sodium Plating/Stripping at Ultralow Temperatures
Advanced Materials ( IF 27.4 ) Pub Date : 2024-01-08 , DOI: 10.1002/adma.202312161
Liang Hu ₁ , Jiaojiao Deng ₂ , Yuxiao Lin ₃ , Qinghua Liang ₄ , Bingcheng Ge ₁ , Qingsong Weng ₁ , Yu Bai ₅ , Yunsong Li ₆ , Yonghong Deng ₇ , Guohua Chen ₈ , Xiaoliang Yu ₁

Affiliation

The reversible and durable operation of sodium metal batteries at low temperatures (LT) is essential for cold-climate applications but is plagued by dendritic Na plating and unstable solid-electrolyte interphase (SEI). Current Coulombic efficiencies of sodium plating/stripping at LT fall far below 99.9%, representing a significant performance gap yet to be filled. Here, the solvation structure of the conventional 1 m NaPF₆ in diglyme electrolyte by facile cyclic ether (1,3-dioxolane, DOL) dilution is efficiently reconfigured. DOL diluents help shield the Na⁺-PF₆⁻ Coulombic interaction and intermolecular forces of diglyme, leading to anomalously high Na⁺-ion conductivity. Besides, DOL participates in the solvation sheath and weakens the chelation of Na⁺ by diglyme for facilitated desolvation. More importantly, it promotes concentrated electron cloud distribution around PF₆⁻ in the solvates and promotes their preferential decomposition. A desired inorganic-rich SEI is generated with compositional uniformity, high ionic conductivity, and high Young's modulus. Consequently, a record-high Coulombic efficiency over 99.9% is achieved at an ultralow temperature of −55 °C, and a 1 Ah capacity pouch cell of initial anode-free sodium metal battery retains 95% of the first discharge capacity over 100 cycles at −25 °C. This study thus provides new insights for formulating electrolytes toward increased Na reversibility at LT.

中文翻译：

通过多功能稀释剂重构电解质溶剂化，实现超低温下钠电镀/剥离的库仑效率超过 99.9%

钠金属电池在低温（LT）下的可逆和持久运行对于寒冷气候应用至关重要，但受到枝晶钠镀层和不稳定的固体电解质界面（SEI）的困扰。当前 LT 下钠电镀/剥离的库仑效率远低于 99.9%，这表明存在尚未填补的重大性能差距。在这里，通过简单的环醚（1,3-二氧戊环，DOL）稀释，传统的1 m NaPF ₆在二甘醇二甲醚电解质中的溶剂化结构被有效地重新配置。 DOL 稀释剂有助于屏蔽二甘醇二甲醚的 Na ⁺ -PF ₆ ^-库仑相互作用和分子间力，从而导致异常高的 Na ⁺离子电导率。此外，DOL参与溶剂化鞘层，削弱二甘醇二甲醚对Na ⁺的螯合，促进去溶剂化。更重要的是，它促进了溶剂化物中PF ₆ ^-周围电子云的集中分布，并促进它们的优先分解。生成所需的富含无机物的 SEI，具有成分均匀性、高离子电导率和高杨氏模量。因此，在-55℃的超低温下实现了超过99.9%的创纪录库仑效率，并且初始无阳极钠金属电池的1Ah容量软包电池在100次循环后仍保留了95%的首次放电容量。 −25°C。因此，这项研究为配制电解质以提高 LT 时的 Na 可逆性提供了新的见解。

更新日期：2024-01-08

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