Chen Shijian, Xiang Yuxuan, Zheng Guorui, Liao Ying, Ren Fucheng, Zheng Yezhen, He Huajin, Zheng Bizhu, Liu Xiangsi, Xu Ningbo, Luo Mingzeng, Zheng Jianming, Yang Yong
Collaborative Innovation Center of Chemistry for Energy Materials, State Key Laboratory for Physical Chemistry of Solid Surface, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
College of Energy, Xiamen University, Xiamen 361005, China.
ACS Appl Mater Interfaces. 2020 Jun 17;12(24):27794-27802. doi: 10.1021/acsami.0c06930. Epub 2020 Jun 4.
Lithium (Li) metal anode (LMA) has received growing attention due to its highest theoretical capacity (3860 mA h g) and lowest redox potential (-3.04 V versus standard hydrogen electrode). However, practical application of LMA is obstructed by the detrimental side reactions between Li metal and organic electrolytes, especially when cycled in traditional carbonate ester electrolytes. Herein, we propose a novel fluorinated carbonate ester-based electrolyte by combining diethyl fluorocarbonate (ETFEC) solvent and 5 M LiFSI concentration (M = mol L). Using this electrolyte, an ultrahigh Li plating/stripping Coulombic efficiency (CE) of 99.1% can be obtained in Li||Cu cells and a stable cycle performance of Li||LiFePO is achieved under the conditions of limited Li metal (5 mA h cm), moderate loading LiFePO (7-8 mg cm), and lean electrolyte (40 uL). The fundamental functioning mechanism of this novel electrolyte has been carefully investigated by scanning electronic microscopy (SEM), operando optical microscopy (OM), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and solid state nuclear magnetic resonance (SS-NMR). The results demonstrate that this optimized electrolyte facilitates formation of a high Li conductive SEI layer enriched with LiF and inorganic sulfur-containing species, which can effectively suppress the side reactions between electrolyte and Li metal and prevent formation of dead Li.
锂（Li）金属阳极（LMA）因其最高理论容量（3860 mA h g）和最低氧化还原电位（相对于标准氢电极-3.04 V）而受到越来越多的关注。然而，锂金属与有机电解质之间的有害副反应阻碍了LMA的实际应用，尤其是在传统碳酸酯电解质中循环时。在此，我们通过将氟代碳酸二乙酯（ETFEC）溶剂和5 M LiFSI浓度（M = mol L）相结合，提出了一种新型的基于氟代碳酸酯的电解质。使用这种电解质，在Li||Cu电池中可获得99.1%的超高锂电镀/剥离库仑效率（CE），并且在有限锂金属（5 mA h cm）、适度负载LiFePO（7-8 mg cm）和贫电解质（40 uL）的条件下实现了Li||LiFePO的稳定循环性能。通过扫描电子显微镜（SEM）、原位光学显微镜（OM）、电化学阻抗谱（EIS）、X射线光电子能谱（XPS）和固态核磁共振（SS-NMR）对这种新型电解质的基本作用机制进行了仔细研究。结果表明，这种优化的电解质有助于形成富含LiF和无机含硫物种的高锂导电SEI层，这可以有效抑制电解质与锂金属之间的副反应并防止死锂的形成。
