Designing fluorine-free electrolytes for stable sodium metal anodes and high-power seawater batteries via SEI reconstruction,Energy & Environmental Science

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Designing fluorine-free electrolytes for stable sodium metal anodes and high-power seawater batteries via SEI reconstruction
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2022-08-25 , DOI: 10.1039/d2ee01295b
Jinuk Kim ₁ , Jioh Kim ₁ , Jooyoung Jeong _{1,

2} , Jiwon Park ₃ , Cheol-Young Park ₁ , Sewon Park _{1,

4} , Shin Gwon Lim ₅ , Kyu Tae Lee ₅ , Nam-Soon Choi ₁ , Hye Ryung Byon ₃ , Changshin Jo _{2,

6} , Jinwoo Lee ₁

Affiliation

Fluorine (F) is regarded as a key element in electrolytes for sodium metal anodes (SMAs) because of the formation of NaF containing solid–electrolyte interphase (SEI) layers; however, the high-cost and HF formation issues experienced by F-based electrolytes should be addressed. Herein, F-free, cost-effective 1 M NaBH₄/ether-based electrolytes are proposed, motivated by the recent speculation that NaH is a “good SEI layer.” The time-of-flight secondary ion mass spectrometry (TOF-SIMS) results of sodium metal electrodes after galvanostatic cycling demonstrated that NaH is a major component of the SEI layer. In addition, the native oxide surface of sodium was converted into NaH and NaBO₂ after soaking in the electrolytes, implying that “SEI reconstruction” occurred by chemical reduction. Accordingly, significantly longer cyclability was obtained in the Na‖Na symmetric cell (1200 h, 1 mA cm⁻², 1 mA h cm⁻²) than in F-based electrolytes. In seawater batteries (SWBs), 1 M NaBH₄/DEGDME (diethylene glycol dimethyl ether) delivers higher power density (2.82 mW cm⁻² vs. 2.27 mW cm⁻²) and cyclability (300 h vs. 50 h) under 1 mA cm⁻² than 1 M NaOTf/TEGDME (tetraethylene glycol dimethyl ether), which is commonly used in SWBs. In conclusion, two novel contributions of this study include the demonstration that NaH can work as a “good SEI layer” apart from NaF and the proposal of a cost-effective, F-free electrolyte for practical and large-scale SWBs.

中文翻译：

通过 SEI 重建设计用于稳定钠金属负极和大功率海水电池的无氟电解质

氟 (F) 被认为是钠金属阳极 (SMA) 电解质中的关键元素，因为它会形成含 NaF 的固体电解质界面 (SEI) 层；然而，应解决 F 基电解质所经历的高成本和 HF 形成问题。在此，由于最近推测 NaH 是“良好的 SEI 层”，提出了不含 F、具有成本效益的 1 M NaBH _{4 /醚基电解质。}恒电流循环后钠金属电极的飞行时间二次离子质谱 (TOF-SIMS) 结果表明，NaH 是 SEI 层的主要成分。此外，钠的天然氧化物表面转化为 NaH 和 NaBO ₂浸泡在电解液中后，暗示“SEI重建”是通过化学还原发生的。因此，在 Na‖Na 对称电池（1200 小时，1 mA cm ^-2，1 mA h cm ^-2）中获得了比 F 基电解质显着更长的循环能力。在海水电池 (SWB) 中，1 M NaBH ₄ /DEGDME（二甘醇二甲醚）在 1 mA 电流下提供更高的功率密度（2.82 mW cm ^-2 对2.27 mW cm ^-2）和可循环性（300 小时对50 小时）厘米^-2大于 1 M NaOTf/TEGDME（四甘醇二甲醚），通常用于 SWB。总之，这项研究的两个新贡献包括证明 NaH 可以作为除 NaF 之外的“良好 SEI 层”，以及为实用和大规模 SWB 提出具有成本效益的无 F 电解质。

更新日期：2022-08-25

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