We explore a novel ether aided superconcentrated ionic liquid electrolyte: a combination of ionic liquid, N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (C₃mpyrFSI) and ether solvent, 1,2 dimethoxy ethane (DME) with 3.2 mol kg⁻¹ LiFSI salt, which offers an alternative ion-transport mechanism and improves the overall fluidity of the electrolyte. The molecular dynamics (MD) study reveals that the coordination environment of lithium in the ether aided ionic liquid system offers a coexistence of both the ether DME and FSI anion simultaneously and the absence of ‘free’, uncoordinated DME solvent. These structures lead to very fast kinetics and improved current density for lithium deposition–dissolution processes. Hence the electrolyte is used in a lithium metal battery against a high mass loading (∼12 mg cm⁻²) LFP cathode which was cycled at a relatively high current rate of 1 mA cm⁻² for 350 cycles without capacity fading and offered an overall coulombic efficiency of >99.8%. Additionally, the rate performance demonstrated that this electrolyte is capable of passing current density as high as 7 mA cm⁻² without any electrolytic decomposition and offers a superior capacity retention. We have also demonstrated an ‘anode free’ LFP–Cu cell which was cycled over 50 cycles and achieved an average coulombic efficiency of 98.36%. The coordination chemistry and (electro)chemical understanding as well as the excellent cycling stability collectively leads toward a breakthrough in realizing the practical applicability of this ether aided ionic liquid electrolyte in lithium metal battery applications, while delivering high energy density in a prototype cell.

中文翻译：

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醚助超浓缩离子液体电解质中增强的离子传输，适用于长寿命的实用锂金属电池应用

我们探索了一种新型的醚助超浓缩离子液体电解质：离子液体，N-丙基-N-甲基吡咯烷鎓双（氟磺酰基）酰亚胺（C ₃ mpyrFSI）和醚溶剂，1,2 mol二甲氧基乙烷1,2二甲氧基乙烷（DME）的组合^-1LiFSI盐提供了一种替代的离子传输机制，并改善了电解质的整体流动性。分子动力学（MD）研究表明，锂在醚辅助离子液体系统中的配位环境同时提供了醚DME和FSI阴离子的共存，并且没有“游离的”未配位的DME溶剂。这些结构导致锂沉积-溶解过程非常快的动力学并提高了电流密度。因此，该电解质用于锂金属电池中的高质量负载（〜12 mg cm ^-2）LFP阴极，该阴极以相对较高的电流速率（1 mA cm ^-2）循环在350次循环中不发生容量衰减，并且库仑效率整体> 99.8％。另外，速率性能证明该电解质能够通过高达7mA cm ^-2的电流密度而没有任何电解分解，并提供了优异的容量保持率。我们还展示了一个“无阳极” LFP-Cu电池，该电池循环了50个循环，平均库仑效率为98.36％。对配位化学和（电化学）化学的了解以及出色的循环稳定性共同导致在实现这种醚辅助离子液体电解质在锂金属电池应用中的实际适用性的同时取得突破，同时在原型电池中提供了高能量密度。