Concentrated Ionic-Liquid-Based Electrolytes for High-Voltage Lithium Batteries with Improved Performance at Room Temperature
Concentrated Ionic-Liquid-Based Electrolytes for High-Voltage Lithium Batteries with Improved Performance at Room Temperature
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DOI：
10.1002/cssc.201901739
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发表时间：
2019-08-13
期刊：
影响因子：
8.4
通讯作者：
Passerini, Stefano
中科院分区：
文献类型：
--
作者：
Gao, Xinpei;Wu, Fanglin;Passerini, Stefano
离子液体作为替代电解质已被广泛探索，以解决与传统有机电解质相关的安全问题。然而，由于其相对较高的粘度，il基电池的电化学性能通常在中高温和有限循环速率下进行评估。烷氧基功能化阳离子与不对称亚胺阴离子的适当组合可以有效降低晶格能，提高IL材料的流动性。采用n - n -二乙基- n -甲基- n -（2-甲氧基乙基）铵（氟磺酰基）（三氟甲烷磺酰基）亚胺（DEMEFTFSI）基电解质的Li/Li1.2Ni0.2Mn0.6O2电池在2.5-4.6 V电压范围内提供了153 mAh g（-1）的初始容量，500次循环后容量保持率为65.5%，稳定的库仑效率超过99.5%。此外，初步的电池测试表明，在倍率能力方面的缺点可以通过使用锂浓缩的il基电解质来改善。这些电解质的室温速率性能的提高可能是由于含有Li+的聚集体的形成，改变了浓度依赖的Li离子传输机制。
Ionic liquids (ILs) have been widely explored as alternative electrolytes to combat the safety issues associated with conventional organic electrolytes. However, hindered by their relatively high viscosity, the electrochemical performances of IL-based cells are generally assessed at medium-to-high temperature and limited cycling rate. A suitable combination of alkoxy-functionalized cations with asymmetric imide anions can effectively lower the lattice energy and improve the fluidity of the IL material. The Li/Li1.2Ni0.2Mn0.6O2 cell employing N-N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (DEMEFTFSI)-based electrolyte delivered an initial capacity of 153 mAh g(-1) within the voltage range of 2.5-4.6 V, with a capacity retention of 65.5 % after 500 cycles and stable coulombic efficiencies exceeding 99.5 %. Moreover, preliminary battery tests demonstrated that the drawbacks in terms of rate capability could be improved by using Li-concentrated IL-based electrolytes. The improved room-temperature rate performance of these electrolytes was likely owing to the formation of Li+-containing aggregate species, changing the concentration-dependent Li-ion transport mechanism.