Due to the intrinsic flame‐retardant, eutectic electrolytes are considered a promising candidate for sodium‐metal batteries (SMBs). However, the high viscosity and ruinous side reaction with Na metal anode greatly hinder their further development. Herein, based on the Lewis acid‐base theory, a new eutectic electrolyte (EE) composed of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), succinonitrile (SN), and fluoroethylene carbonate (FEC) is reported. As a strong Lewis base, the ─C≡N group of SN can effectively weaken the interaction between Na+ and TFSI−, achieving the dynamic equilibrium and reducing the viscosity of EE. Moreover, the FEC additive shows a low energy level to construct thicker and denser solid electrolyte interphase (SEI) on the Na metal surface, which can effectively eliminate the side reaction between EE and Na metal anode. Therefore, EE‐1:6 + 5% FEC shows high ionic conductivity (2.62 mS cm−1) and ultra‐high transference number of Na+ (0.96). The Na||Na symmetric cell achieves stable Na plating/stripping for 1100 h and Na||Na3V2(PO4)3/C cell shows superior long‐term cycling stability over 2000 cycles (99.1% retention) at 5 C. More importantly, the Na||NVP/C pouch cell demonstrates good cycling performance of 102.1 mAh g−1 after 135 cycles at 0.5 C with an average coulombic efficiency of 99.63%.

中文翻译：

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相互作用的三元组分确保高性能钠金属电池的高安全性共晶电解质


由于其固有的阻燃性，共晶电解质被认为是钠金属电池（SMB）的有前途的候选者。然而，高粘度和与钠金属阳极发生破坏性副反应极大地阻碍了它们的进一步发展。在此，基于路易斯酸碱理论，报道了一种由双（三氟甲磺酰基）亚胺钠（NaTFSI）、丁二腈（SN）和氟代碳酸亚乙酯（FEC）组成的新型共晶电解质（EE）。作为强路易斯碱，SN的─C≡N基团可以有效削弱Na+和TFSI−之间的相互作用，达到动态平衡并降低EE的粘度。此外，FEC添加剂表现出低能级，可以在Na金属表面构建更厚、更致密的固体电解质界面（SEI），可以有效消除EE与Na金属阳极之间的副反应。因此，EE-1:6 + 5% FEC 显示出高离子电导率（2.62 mS cm−1）和超高的 Na+ 迁移数（0.96）。 Na||Na 对称电池实现了 1100 小时稳定的 Na 电镀/剥离，Na||Na3V2(PO4)3/C 电池在 5 C 下显示出超过 2000 个循环的优异长期循环稳定性（99.1% 保留率）。更重要的是， Na||NVP/C软包电池在0.5 C下循环135次后表现出102.1 mAh g−1的良好循环性能，平均库仑效率为99.63%。