物理化学学报 >> 2021, Vol. 37 >> Issue (1): 2004058.doi: 10.3866/PKU.WHXB202004058

所属专题： 金属锂负极

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原位聚合表面修饰的金属锂负极

刘亚1,2, 郑磊2,3, 谷巍2,4, 沈炎宾2,*(), 陈立桅2,5,*()   

  1. 1 中国科学技术大学纳米科学技术学院，江苏 苏州 215123
    2 中国科学院苏州纳米技术与纳米仿生研究所，国际实验室卓越纳米科学中心，江苏 苏州 215123
    3 中国科学技术大学纳米技术与纳米仿生学院，合肥 230026
    4 上海科技大学物质科学与技术学院，上海 201210
    5 上海交通大学化学化工学院，上海 200240
  • 收稿日期:2020-04-21 录用日期:2020-05-14 发布日期:2020-05-20
  • 通讯作者: 沈炎宾,陈立桅 E-mail:ybshen2017@sinano.ac.cn;lwchen2008@sinano.ac.cn
  • 基金资助:
    国家自然科学基金(21625304);国家自然科学基金(21733012);国家自然科学基金(21772190);国家科技部(2016YFB0100102)

Surface Passivation of Lithium Metal via In situ Polymerization

Ya Liu1,2, Lei Zheng2,3, Wei Gu2,4, Yanbin Shen2,*(), Liwei Chen2,5,*()   

  1. 1 Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, Jiangsu Province, China
    2 i-Lab, CAS Center for Excellence in Nanoscience, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, Jiangsu Province, China
    3 School of Nano Technology and Nano Bionics, University of Science and Technology of China, Hefei 230026, China
    4 School of Physical Science and Technology, Shanghai Tech University, Shanghai 201210, China
    5 School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
  • Received:2020-04-21 Accepted:2020-05-14 Published:2020-05-20
  • Contact: Yanbin Shen,Liwei Chen E-mail:ybshen2017@sinano.ac.cn;lwchen2008@sinano.ac.cn
  • About author:Chen Liwei. E-mail:lwchen2008@sinano.ac.cn.Tel.: +86-512-62872655
    Shen Yanbin. E-mail:ybshen2017@sinano.ac.cn. Tel.: +86-512-62872503
  • Supported by:
    the National Natural Science Foundation of China(21625304);the National Natural Science Foundation of China(21733012);the National Natural Science Foundation of China(21772190);the Ministry of Science and Technology of China(2016YFB0100102)

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摘要：

金属锂负极由于比容量高(3860 mAh·g-1)及氧化还原电位极低(-3.04 V vs.标准氢气电极(SHE))，被认为是实现高能量密度锂电池的理想负极。然而，金属锂电极与电解液反应剧烈，且锂离子在电极表面沉积不均匀容易产生枝晶，导致其循环稳定性和安全性都较差，限制了其应用推广。我们前期通过构建金属锂-碳纳米管(Li-CNT)复合结构，极大的提高了金属锂的比表面积，降低了电极电流密度，从而有效地抑制了锂枝晶的生长，提高了金属锂电极的循环稳定性和安全性能。本工作在前期工作基础上，采用简单的液相反应，利用4-氟苯乙烯(FPS)对Li-CNT进行表面修饰并进行原位聚合，得到了表面富含氟化锂(LiF)保护层的Li-CNT(FPS-Li-CNT)。该表面修饰层能够有效抑制电解液和空气对Li-CNT的侵蚀，显著的提高了Li-CNT电极的界面稳定性。FPS-Li-CNT与磷酸铁锂正极(LFP)组成的LFP||FPS-Li-CNT全电池，在正负极容量配比为1 : 6条件下，能够稳定循环280圈，库伦效率达到97.7%。

关键词: 锂碳纳米管复合物, 金属锂电池, 氟化锂, 原位聚合, 锂枝晶

Abstract:

Lithium (Li) metal is considered a promising anode material for high energy density secondary Li metal batteries because it has the highest specific energy (3860 mAh·g-1) and lowest redox potential (-3.04 V compared to standard hydrogen electrodes. However, the development of high-performance Li metal batteries is challenging. Firstly, Li dendrites tend to grow on the surface of Li metal foil, leading to a limited anodic coulombic efficiency (CE), poor cyclability, and even explosion hazards when an internal cell short circuit occurs. Moreover, Li metal suffers from serious surface stability problems and is easily corroded by electrolytes during cycling, further resulting in low CE, thus shortening the life cycle. We have developed a Li-carbon nanotube (Li-CNT) composite microsphere via a facile molten impregnation method. The Li-CNT composite's CNT framework can suppress volume changes during the charge/discharge process and help stabilize the solid electrolyte interphase (SEI), which is typically mechanically fragile. As a result, Li-CNT shows a high specific capacity (2000 mAh·g-1) and can significantly suppress dendrite formation by reducing the current density, resulting in enhanced safety and cycling stability. However, the large specific surface area of the Li-CNT microspheres also enables increased reaction with the air and the electrolyte. A passivation layer is critical for the practical application of Li-CNT during the electrochemical cycling and manufacturing process. LiF is an important component of SEI in the liquid electrolyte system, and a uniform and dense LiF-rich SEI film can enable stable cycling. Moreover, LiF has been widely used as the preferred coating material to protect Li metal anodes through different methods. In this study, we improved the Li-CNT composite stability by constructing a uniform LiF-rich protecting layer on the surface through in situ polymerization of 4-fluorostyrene. The F functional group of 4-fluorostyrene, which is a lithiophilic group, reacts with the Li-CNT to produce a uniform LiF-rich layer on the surface of the Li-CNT via a facile and scalable liquid-phase reaction. The resulting passivation layer effectively suppresses the Li-CNT corrosion by the electrolyte and air, leading to better environmental and electrochemical stability. Consequently, after exposure to dry-air with a dew point -40 ℃ for 24 h, the specific capacity of the surface passivated Li-CNT is still as high as 1129 mAh·g-1, corresponding to a capacity retention of 52.85%. When the surface passivated Li-CNT is paired with a LiFePO4 cathode (the capacity ratio of cathode and anode is 1 : 6), a prolonged lifespan of over 280 cycles at 0.5C was reached, corresponding to a CE of 97.7%. The in situ polymerization passivation is simple and easy to be scale up; thus, it is a promising method for developing Li metal anodes towards the practical Li metal batteries.

Key words: Li-carbon nanotube, Li metal battery, LiF, In situ polymerization, Li dendrite