物理化学学报 >> 2020, Vol. 36 >> Issue (11): 1912068.doi: 10.3866/PKU.WHXB201912068

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多酚类化合物—丹宁酸用作锂金属负极电解液成膜添加剂

冉琴1, 孙天霷1, 韩冲宇1, 张浩楠2, 颜剑2, 汪靖伦1,*()   

  1. 1 理论有机化学与功能分子教育部重点实验室,湖南科技大学化学化工学院,湖南 湘潭 411201
    2 桑顿新能源科技有限公司,湖南 湘潭 411201
  • 收稿日期:2019-12-27 录用日期:2020-03-06 发布日期:2020-03-17
  • 通讯作者: 汪靖伦 E-mail:jlwang@hnust.edu.cn
  • 基金资助:
    湖南科技大学博士科研启动项目(E518B1);湖南科技大学2019年度大学生科研创新计划项目“挑战杯专项”(TZ9003)

Natural Polyphenol Tannic Acid as an Efficient Electrolyte Additive for High Performance Lithium Metal Anode

Qin Ran1, Tianyang Sun1, Chongyu Han1, Haonan Zhang2, Jian Yan2, Jinglun Wang1,*()   

  1. 1 Key Laboratory of Theoretical Organic Chemistry and Functional Molecule, Ministry of Education, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan 411201, Hunan Province, P. R. China
    2 Soundon New Energy Technology Co. Ltd., Xiangtan 411201, Hunan Province, P. R. China
  • Received:2019-12-27 Accepted:2020-03-06 Published:2020-03-17
  • Contact: Jinglun Wang E-mail:jlwang@hnust.edu.cn
  • Supported by:
    the Doctoral Foundation of Hunan University of Science and Technology, China(E518B1);2019 Undergraduate Student Scientific Research Innovation Plan "Challenge Cup Project" of Hunan University of Science and Technology, China(TZ9003)

摘要:

金属锂因具有高理论容量和低化学电位被认为是电化学储能系统的“圣杯”,但无规则的锂枝晶生长和与电解液的高反应活性导致其安全性能差和库伦效率低,这严重阻碍了锂金属负极的大规模应用。电解液添加剂具有用量小、效果显著等特点,是改善电池性能的有效手段之一。本研究首次报道一种植物多酚—丹宁酸(TA)用作电解液添加剂改善锂金属负极的电化学性能。通过在基础电解液1 mol·L-1 LiPF6-EC/DMC/EMC (1 : 1 : 1,质量比)中添加质量分数0.15% TA,Li|Li对称电池在电流密度为1 mA·cm-2和容量为1 mAh·cm-2的条件下能稳定循环270 h (以0.1 V为截止电压),而没有TA添加剂的Li|Li电池在相同条件下只能循环170 h。电化学阻抗、扫描电镜、傅里叶红外、循环伏安和X射线能谱分析测试结果表明,丹宁酸能在锂金属表面参与形成了一层稳定且致密的固态电解质界面层。推测其可能的机理为多羟基酚有助于LiPF6的水解反应并形成LiF,多羟基酚的锂盐能与碳酸二甲酯发生酯交换反应而形成交联聚合物,从而形成了稳定且均匀的有机/无机复合SEI膜、显著提高了锂金属负极的电化学性能。

关键词: 丹宁酸, 电解液添加剂, 固态电解质界面膜, 锂金属负极

Abstract:

As the application of lithium-ion batteries in advanced consumer electronics, energy storage systems, plug-in hybrid electric vehicles, and electric vehicles increases, there has emerged an urgent need for increasing the energy density of such batteries. Lithium metal anode is considered as the "Holy Grail" for high-energy-density electrochemical energy storage systems because of its low reduction potential (-3.04 V vs standard hydrogen electrode) and high theoretical specific capacity (3860 mAh·g-1). However, the practical application of lithium metal anode in rechargeable batteries is severely limited by irregular lithium dendrite growth and high reactivity with the electrolytes, leading to poor safety performance and low coulombic efficiency. Recent research progress has been well documented to suppress dendrite growth for achieving long-term stability of lithium anode, such as building artificial protection layers, developing novel electrolyte additives, constructing solid electrolytes, using functional separator, designing composite electrode or three-dimensional lithium-hosted material. Among them, the use of electrolyte additives is regarded as one of the most effective and economical methods to improve the performance of lithium-ion batteries. As a natural polyphenol compound, tannic acid (TA) is significantly cheaper and more abundant compared with dopamine, which is widely used for the material preparation and modification in the field of lithium-ion batteries. Herein, TA is first reported as an efficient electrolyte film-forming additive for lithium metal anode. By adding 0.15% (mass fraction, wt.) TA into the base electrolyte of 1 mol·L-1 LiPF6-EC/DMC/EMC (1 : 1 : 1, by wt.), the symmetric Li|Li cell exhibited a more stable cyclability of 270 h than that of only 170 h observed for the Li|Li cell without TA under the same current density of 1 mA·cm-2 and capacity of 1 mAh·cm-2 (with a cutoff voltage of 0.1 V). Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), and energy-dispersive X-ray spectroscopy (EDS) analyses demonstrated that TA participated in the formation of a dense solid electrolyte interface (SEI) layer on the surface of the lithium metal. A possible reaction mechanism is proposed here, wherein the small amount of added polyphenol compound could have facilitated the formation of LiF through the hydrolysis of LiPF6, following which the resulting phenoxide could react with dimethyl carbonate (DMC) through transesterification to form a cross-linked polymer, thereby forming a unique organic/inorganic composite SEI film that significantly improved the electrochemical performance of the lithium metal anode. These results demonstrate that TA can be used as a promising film-forming additive for the lithium metal anode.

Key words: Tannic acid, Electrolyte additive, Solid electrolyte interface, Lithium metal anode

MSC2000: 

  • O646