双（2-氟乙基）碳酸酯作为一种新型电解质添加剂可提高锂金属电池的长期循环性能,Journal of The Electrochemical Society

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双（2-氟乙基）碳酸酯作为一种新型电解质添加剂可提高锂金属电池的长期循环性能
Journal of The Electrochemical Society ( IF 3.1 ) Pub Date : 2023-02-28 , DOI: 10.1149/1945-7111/acbca1
Jiwon Han , Changhee Park , Dahee Jin , Suhwan Kim , Cyril Bubu Dzakpasu , Sunggi Lee , Yong Min Lee

为了满足高能量密度的需求，锂金属因其高理论比容量和低电极电位而被认为是下一代负极材料。然而，传统的基于LiPF ₆的电解质在锂金属上形成厚而多孔的固体电解质界面（SEI），导致循环性能差。解决这些问题的尝试之一是优化电解质成分，因为锂金属与电解质的反应最活跃。在这里，双（2-氟乙基）碳酸酯（B-FC）作为一种新型氟基线性碳酸酯，被添加到基于 LiTFSI-LiBOB 的双盐电解质中。为了确认 B-FC 对电化学性能的影响，Li || Li 对称电池和 LiNi _0.6 Co _0.2 Mn _0.2 O ₂(NMC622) || 评估了有或没有 B-FC 的锂金属全电池。B-FC 的添加形成了富含 LiF 的 SEI，并显着减少了锂枝晶的生长，从而导致薄死锂层的形成。此外，NMC622的高压性能|| 与纯 DSL 相比，具有 B-FC 的锂金属全电池得到有效改善（300 次循环后容量保持率分别为 73.1% 和 62.4% ，在 21 mA cm ^-2时的容量分别为 117 mAh g −1 和 87 ^mAh g ⁻¹） . 因此，在本文中，我们证明了即使在 4.5 V 截止条件下，具有 B-FC 的双盐也可以稳定 SEI。

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A Bis(2-fluoroethyl) Carbonate as a New Electrolyte Additive for Enhancing the Long-Term Cycle Performance of Li-Metal Batteries

To meet the demand for high energy density, Li metal is considered a next-generation anode material owing to its high theoretical specific capacity and low electrode potential. However, conventional LiPF₆-based electrolytes form a thick and porous solid electrolyte interphase (SEI) on Li metal, resulting in poor cycle performance. One of attempts to resolve these is to optimize the electrolyte composition because the Li metal reacts most actively with electrolyte. Here, bis(2-fluoroethyl) carbonate (B-FC), as a new fluorine-based linear carbonate, was added to a LiTFSI–LiBOB-based dual-salt electrolyte. To confirm the effect of B-FC on the electrochemical properties, Li || Li symmetric cells and LiNi_0.6Co_0.2Mn_0.2O₂ (NMC622) || Li metal full cells with or without B-FC were evaluated. The addition of B-FC forms LiF-rich SEI and significantly reduced Li dendrite growth, leading to the thin dead Li layer formation. Furthermore, high-voltage performances of NMC622 || Li metal full cells with B-FC were effectively improved compared to the pure DSL (capacity retention of 73.1% vs 62.4% after 300 cycles and a capacity of 117 mAh g⁻¹ vs 87 mAh g⁻¹ at 21 mA cm⁻²). Consequently, herein, we demonstrated that the dual-salts with B-FC can stabilize the SEI even under the 4.5 V cut-off condition.

更新日期：2023-02-28

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